Recovery from Intermittent exercise by the Christmas Island red crab, Gecarcoidea natalis

Agnieszka M. Adamczewska‡ and Steve Morris†

‡ InterRidge, Ocean Research Institute, University of Tokyo, Tokyo, Japan
† Morlab, School of Biological Sciences University of Bristol, Bristol UK

To determine if intermittent walking in terrestrial Christmas Island red crab, Gecarcoidea natalis would be an advantageous locomotor strategy for this species, we investigated the rate of recovery from voluntary intermittent exercise in the red crabs.

Two different exercise regimens were used: four cycles of either 2.5 min exercise/2.5 min rest or 4 min exercise/1 min rest. Haemolymph and tissue samples were obtained from crabs at rest, immediately after exercise and after 5 min, 30 min, 5 h and 24 h of recovery from exercise (4/1). Metabolites and high energy phosphates were measured in the leg muscle tissue to determine the status of oxygen debt.

Both exercise regimens resulted in a significant decrease in the energy charge (by ~ 0.05 units) and a decrease in adenylate-P of ~50%, while glucose and L-lactate levels increased. Five minutes post exercise, only the Energy Charge showed recovery. After 30 min of recovery Arginine-P levels were still only two thirds of resting values. Lactate continued to increase during the first 5 min of recovery from exercise (max ~ 35 @mol/g in the muscle after 5 min of recovery. After 5 hours of recovery, the perturbations in the parameters measured were no longer statistically different from basal levels. Since the rate of Lactate reoxidation and high energy phosphate recovery after exercise is rather slow, exercise at a rate where these crabs accumulate an oxygen debt would not be an advantageous locomotor strategy for this species.

Living in the cold: Energy economising in arctic breeding Kittiwakes (Rissa tridactyla)

Claus Bech¹, Ingveig Langseth¹, Børge Moe¹, Marianne Fyhn^2,3 and Geir Wing Gabrielsen²

¹Department of Zoology, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway (correspondence: claus.bech@chembio.ntnu.no)
²Norwegian Polar Institute, Polar Environmental Centre, NO-9296 Tromsø, Norway
³Department of Arctic Biology, University of Tromsø, NO-9037 Tromsø, Norway

We measured rates of energy metabolism (basal metabolic rates [BMR] and field metabolic rates [FMR]), body masses and body composition in female Kittiwakes throughout the breeding season at Svalbard (79°N). At this high latitude, the time of breeding in Kittiwakes is distinguished by continuous daylight, ambient temperatures averaging only 4.5°C and occasional spells of very cold weather.
The main characteristic of the energy budget of breeding Kittiwakes, is a decrease in body mass and BMR after hatching. Also the FMR during the first part of the chick-rearing period is lower than during the pre-incubation and incubation period. The first part of the chick-rearing period is hence a period of negative energy balance, which probably is caused by time constraints, since one of the adults needs to attend the chicks at all times. After thermal independence of the chicks, at an age of about 15 days, more time is available for the adults to forage. However, the BMR is still kept at a low level. The reduction in BMR during the chick-rearing period could be an adaptation to reduce the maintenance cost of the adults, allowing the parent birds to allocate more energy into chick growth. While most internal organs are reduced in mass in direct proportion to the general decrease in body mass, the liver and the kidney masses decreases disproportionately more. Since both the liver and the kidney are known to have high intrinsic metabolic rates, the results supports the notion that the reduction in body mass is an adaptation to reduce the maintenance costs. At the end of the chick-rearing period, FMR reaches its highest level during the breeding season mainly as a result of an increased workload connected to the increased chick feeding. This occurs at a time of stable or slightly increased body mass. A large increase in metabolic intensity (FMR/BMR) during the latter part of the chick-rearing period suggests that this ratio is not a good measure of energy stress during breeding in Kittiwakes.

Hematology and hematozoa in North American and neotropical songbirds.

Charles E. Booth and Phillip F. Elliott

Dept. of Biology, Eastern Connecticut State Univ., Willimantic, CT, USA.

As part of a broad survey of blood parasite infections in songbirds, hematology and hematozoa prevalence were examined in 1200+ individuals from ca.100 species captured in Belize (January, March), along the Louisiana Gulf Coast (April), and in Connecticut (May-October). Birds caught in Belize were more heavily parasitized than those caught in the U.S., possibly due to greater exposure to insect vectors in the tropics. Returning trans-Gulf migrants had fewer parasites than migrants wintering in Belize, suggesting that migration may "filter out" heavily infected birds. A higher variance in infection intensity for returning migrants could indicate that migration stress triggers renewed parasite activity within some infected hosts. Tropical residents in Belize had "normal" hemoglobin (Hb) levels despite high parasite loads, suggesting a physiological compensation to parasite infection. Migrants caught in Belize were anemic in January, but had "normal" RBC and Hb levels in March, suggesting that recovery from anemia can occur despite a greater likelihood of parasite infection with increased time in the tropics. Returning trans-Gulf migrants were anemic, suggesting that the stress of long distance flight may result in the loss of circulating RBC's, though fluid shifts could be involved. Data from individual taxa (i.e,. families and species) show trends similar those described here for the pooled data.

Evidence for oxygen and carbon dioxide receptors in the CNS of insects which influence ventilation

H. P. Bustami, *J. F. Harrison, R. Hustert

Institut für Zoologie und Anthropologie der Universität Göttingen, Berliner Str. 28, 37073 Göttingen, Germany;
*Dept. of Biology, Arizona State University, Tempe, Arizona USA 85287-1501

Ventilatory efferent discharges in the isolated central nervous system (CNS) of the lubber grasshopper Taeniopoda eques were recorded and the change of ventilatory rates were measured in correlation to changing partial pressures of oxygen and carbon dioxide. These in vitro responses were compared to the ventilatory rates of intact animals exposed to various gas tensions. We found highly significant effects of oxygen on the ventilatory response of both the in vitro CNS and the intact animals, with ventilatory rates inverse to the partial pressure of oxygen. Our results provide the first direct evidence for the existence of an oxygen receptor located in the CNS. Application of changing carbon dioxide concentrations showed significant effects on ventilatory frequencies in isolated CNS of the American desert locust (Schistocerca americana).

Carbonic anhydrase and carbon dioxide cellular transport in a symbiotic invertebrate, the hydrothermal vent tubeworm Riftia pachyptila

M.C. De Cian, A.C. Andersen, J.Y. Toullec* and F.H. Lallier

Ecophysiologie, Station Biologique de Roscoff, UPMC-CNRS-INSU, BP74, 29682 Roscoff cedex, France, and
* CNRS-EP2028 - Ecole Normale Superieure, 75230 Paris Cedex 05, France

The giant tubeworm Riftia pachyptila is a strict symbiosis with sulfur oxidizing bacteria, found around the East-Pacific Rise hydrothermal vents. The bacteria are located intracellularly in vacuoles of bacteriocytes which form a specialized organ, the trophosome. To fuel their metabolism the bacteria need molecular CO2 as a carbon source, and O2 and H2S as energy source. Carbon dioxide acquisition takes place at the plume level by diffusion and is transported mainly as bicarbonate in the blood towards the trophosome. We have developed a model of CO2 transport involving anion exchangers (AE) and carbonic anhydrases (CA).

In this study we present a new cellular approach, using isolated cell suspensions from plume and trophosome tissues. Worms collected on the bottom (2600m- EPR) by submersible were repressurized at least 4 h using thermostated pressure vessels. Viable cell suspensions have been obtained from plume and trophosome tissues and we found that trophosome preparations were indeed composed mainly of bacteriocytes, as indicated by in situ hybridization with fluorescent probes specific for g proteobacteria. By analyzing the extracellular and intracellular acid-base balance under normo- or hypercapnic conditions with a variety of inhibitors we were able to test the validity of the proposed model. In addition to this physiological approach, we have started to sequence the two forms of CA. Plume CA has been fully sequenced and a mRNA probe has been designed in order to localize CA expression in Riftia tissues.

The enteric nervous system in developing Xenopus and zebrafish

Anna Holmberg, Regina Fritsche, and Susanne Holmgren

University of Göteborg, Department of Zoology/Zoophysiology, Box 463, SE-405 30
Göteborg, Sweden

Corresponding author: anna.holmberg@zool.gu.se

The information about the ontogeny of the enteric nervous system (ENS) in non-mammalian and non-avian vertebrates is sparse. We have studied the development of ENS in relation to onset of exogenous feeding in developing South African clawed frog, Xenopus laevis and zebrafish, Danio rerio. Xenopus enteric neurons are present before the larvae start to feed (Epperlein, Krotoski, Halfter, Frey. Anatomy & Embryology 1990.182.53-67). By using immunohistochemistry, we studied the first occurrence of structural and functional nerves in Xenopus. In agreement with Epperlein et al. 1990, we found that neurons are present at NF stage 38-39, before the onset of feeding (stage 45). Shortly after the first occurrence of these neurons, they were shown to contain the neurotransmitters VIP (stage 40), PACAP (41), NOS, substance P, or NKA (stage 42). CGRP was demonstrated at stage 47, after the onset of feeding. However, the fact that transmitters are present in these nerves does not necessarily mean that they have a function on the gut motility i.e. the smooth muscles cells may not yet express the proper receptors. Neurotransmitters such as VIP can exhibit a trophic effect. A parallel study on developing zebrafish is performed, and enteric neurons are present from day 3 post fertilization. We conclude that several types of neurons are present and contain transmitters before the onset of feeding.

The roles of GnRH and leptin in the control of spermatogenesis in the four striped field mouse, Rhabdomys pumilio.

C. Jackson and R.T.F. Bernard

Department of Zoology and Entomology, Rhodes University, Grahamstown. 6140.
(r.bernard@ru.ac.za or g94j2708@campus.ru.ac.za)

It was recently shown that the reproductive activity of male Rhabdomys pumilio can be inhibited by a combination of reduced ambient temperature and food availability. However it also became apparent that this inhibition may be reduced by the presence of body fat reserves. To determine how these external factors influence reproductive activity, we examined the effects of exogenous GnRH and leptin on reproductively inactive male R. pumilio. Thirty mice were exposed to 15°C and a reduced food intake and once all the mice were non-scrotal, they were divided into one of two groups. In the first group mice were either injected with GnRH or saline (n=10 per treatment) for twenty-one days. In the second group, mice were either injected with leptin or saline (n=5 per treatment) and were treated for four days. After the respective treatments, the mice were sacrificed, weighed and dissected. Their reproductive organs were removed and weighed and blood was collected for testosterone, LH and leptin assays. Mice injected with GnRH had significantly larger testes and epididymides compared to their controls,, eventhough they were of similar body mass. however, leptin treatment resulted in no significant change in either body mass or reproductive organ mass compared to the control mice. Hormone assays indicated no significant difference in the levels of testosterone, LH or leptin in either experiment. From this we concluded that exogenous GnRH can assist in overcoming the negative effects of reduced food availability and ambient temperature, while exogenous leptin appears to have little effect on reproductive activity.

Surviving the arctic winter: the hibernating arctic ground squirrel

S. Karpovich, Ø. Tøien, and B. M. Barnes

Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775
(fssak3@uaf.edu)

Explanations of the mechanisms by which hibernators depress metabolic rate upon entry into torpor are controversial. Hypotheses fall into two categories: temperature-dependent or temperature-independent metabolic suppression. Temperature-dependent metabolic suppression suggests a downward adjustment of the set-point for body temperature; after which body tissues cool and metabolism decreases passively due to a Q10 effect. Temperature-independent metabolic suppression suggests that first metabolism is actively suppressed, and then Tb falls as a consequence of decreasing heat production. Temperature-independent hypotheses would be supported by observation of metabolic rate and Tb relationships during recooling producing Q10 values >3, the upper limit of what is accepted as the normal physiological range, or a constant torpid metabolic rate as Tb is varied.
A quantitative investigation into the relationship between Tb and VO2 during recooling produced Q10 values of 5. Analysis of the rates of decrease for Tb and VO2 during recooling indicate an effect of Ta on the rate of Tb decrease but not on VO2 depression. Both studies indicate metabolic suppression that is temperature-independent.
Steady state torpor measurements of were collected while warming Tb. Q10 values of 3 were observed, but extrapolate to only 62% of BMR at euthermic Tb’s. This indicates that active suppression of metabolism may be responsible for the initial 38% of entry into torpor after which, the Q10 effect continues to reduce metabolism.

Neural control of the dorsal vessel in lepidopterous insects

Kazuyuki Uchimura¹, Tomoko Matsushita², Hiroyuki Ai³ and Kiyoaki Kuwasawa¹

¹Deapartment of Biological Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji-shi, Tokyo 192-0397, Japan.
²Department of Oral Physiology, Ohu University, Mitsumido 31-1, Tomita-machi, Koriyama-shi, Fukusima, 963-8611.
³Div. of Biology, Dept. of Earth System Sciences, Fukuoka Univ.,8-19-1 Nanakuma, Jonan-ku, Fukuoka city, Fukuoka 814-0180, Japan.

We have previously reported that several types of reflexes of the dorsal vessel are caused by external stimuli applied to various regions of the body in lepidopterous insects (Bombyx mori and Agrius convolvuli). Among the reflexive responses of the dorsal vessel, The junction of the aorta and anterior end of the heart is the initiating site for reflex induction of posterograde heartbeat and thus heartbeat reversal. The anterior cardiac nerve branches off the visceral nerve extending from the frontal ganglion and innervates the junctional region of the dorsal vessel (Ai and Kuwasawa, 1995). (The visceral nerve is known as the recurrent nerve.) Activation of the anterior cardiac nerve triggered posterograde heartbeat even during a period of anterograde heartbeat.
We have now found another nerve branching off the nerve from the corpus cardiacum and innervating the junctional region of the dorsal vessel. This nerve inhibited retrograde heartbeat when electrical pulses were applied at the rostral cut-stump of the nerve. The inhibitory function of this nerve may explain a previous observation. In Manduca sexta, transection of the 3rd cardiacal nerve, extending from the corpus cardiacum, resulted in disinhibition of the pacemaker for the posterograde heartbeat (Davis et al., 2000). These results may indicate that the cardiacal nerve contains inhibitory axons to the anterior region of the dorsal vessel, responsible
for cardiac inhibition of posterograde heartbeat.

Adrenergic cardiac control during development of the African clawed frog, Xenopus laevis.

Angélica Jacobsson Kloberg and Regina Fritsche

Göteborg University, Department of Zoophysiology
(angelica.kloberg@zool.gu.se)

in embryos of the African clawed frog, Xenopus laevis, administration of isoprenaline on the heart causes an increase in heart rate four days post fertilisation. Three days post fertilisation an adrenergic tonus is active on the heart. This tonus increases during early development up to a peak at an age of four to seven days post fertilisation, and then decreases again. Similarly, the embryonic heart beats at its highest rate at day four to seven, suggesting that at least part of the high heart rate at these stages is due to a high adrenergic tonus. Earlier studies have not been able to show any adrenergic nerves in the heart at these early stages, suggesting that adrenergic cardiac control is due to either blood circulating catecholamines or catecholamines endogenous to the heart (or both). In fact, in recent studies catecholamines have been detected in the larval heart tissues from day three post fertilization and further on. A peak in adrenaline concentration, at an age of four to seven days post fertilisation, coincides with the peak in adrenergic tonus. In addition, cells immunoreactive to enzymes involved in the catecholamine synthesis have been found in the heart of Xenopus larvae already from the third day post fertilisation. We propose that adrenergic cardiac control can be achieved by catecholamines, produced and stored in specialised cells in the heart and acting upon beta-like adrenoreceptors.
All animal experiments have been approved by the local ethical committee.

Thermal conditions in the burrows of the Peruvian diving-petrel (Pelecanoides garnotii)

Edda D. Kölsch1, Gregor Kölsch2, Guillermo Luna-Jorquera3, Stefan Garthe1

1 Institut für Meereskunde, Dept. Marine Zoology, Düsternbrooker Weg 20, 24105 Kiel, Germany
2 Zoological Institute, University of Kiel, Olshausenstraße 40, 24098 Kiel, Germany
3 Dep. Biología Marina, Universidad Católica del Norte, Larrondo 1281, Coquimbo, Chile

The Peruvian diving-petrel (Pelecanoides garnotii) breeds on offshore islands in sheltered nests, either in rock crevices or in burrows dug by the birds in soft soil. As part of an investigation into the ecology of seabirds in the upwelling system along the Humboldt Current, these burrows were studied with regard to temperature (involving continuous registration of data for up to three days).
The burrows were about 63 cm long and dampened down the high temperatures incursed during the day (up to 47.7 °C on the ground) and the low temperatures at night (down to 13.2°C). Burrows had a relatively constant temperature (on average between 20.8 and 25.0°C, depending on habitat), which was higher than the mean temperature of the environment. The size of the burrows (length and volume) was correlated with various temperature parameters (maximum, minimum, mean and fluctuation), however, no general rule was found. The burrows had no special orientation, and the orientation of the burrows with respect to the sun or the predominant wind direction did not influence the temperature inside. The temperature at the end of burrows was, on average, higher and showed less fluctuation than at a distance of 30cm from the entrance.
Although the chicks are ectothermic during the first days after hatching, the thermal stability of the burrows soon enables the adults to leave their chicks alone and to forage at sea. A comparison among habitats (sandy plateau, beach, rocky slope) shows that the burrows in the rocky slopes had the lowest average temperatures with higher fluctuations and, therefore, seem less suitable than the burrows dug in the sediment.

Water flux and heat transfer of knots flying at different ambient temperatures

Anders Kvist

Department of Animal Ecology, Lund University, Ecology Building, S-223 62 Lund Sweden

Water efflux rates and evaporative heat loss were estimated from mass loss in two knots in sustained flights at 15 m/s in a windtunnel. At temperatures below 15 °C in one knot (SK) and 23 °C in the other (DG), water efflux rates were constant and water balance could be maintained. Evaporative heat loss accounted for 6 (SK) and 11 (DG) of the total heat production and heat balance was regulated by changes in dry conductance. At higher temperatures evaporative heat loss increased to compensate for a reduced dry heat loss and quickly rose above water influx rates to create a net water loss. Maximum dry conductance was 0.30 W/°C in one bird (SK) and 0.36 W/°C in the other (DG). At 25 °C about 36 (SK) and 15 (DG) of the total heat was lost through evaporation.

Faecal Hormonal Profiles During the Reproductive Cycle, Pregnancy and Lactation in Cricetomys emini (Rodentia: Cricetidae).

M. Jean Malekani

Department of Biology, Faculty of Science, University of Kinshasa, Democratic Republic of Congo.

Cricetomys emini, commonly called cricetoma or improperly named giant rat, is an endemic African rodent of big size (1.4 Kg), traditionally hunted for food in several places where it is still occurring. Its farming can be a good source of meat for many people in Africa who are suffering from hunger and malnutrition. In addition, rearing this species can help to preserve it from overhunting and eventual disappearance and to maintain fauna biodiversity in the concerned ecosystem. Although this rodent has been reproduced with some success in captivity at the University of Kinshasa in Democratic Republic of Congo its reproductive biology is not well known. Attempts to breed this rodent on a large scale have not been successful because detailed knowledge on their reproductive biology is still scanty and sometimes incorrect. The aim of the present study is to describe and re-evaluate the reproductive pattern in Cricetomys emini in terms of occurrence, duration and cyclicity (if! any), mode of ovulation (spontaneous or induced), detection and exact lenght of pregnancy, time and duration of postpartum oestrus, time of oestrus re-establishment after weaning. Sex steroid metabolites (progesterone, oestradiol) will be measured in blood, urine and faecal samples collected from females at different physiological stages. These samples will be prepared (extraction) for thin layer chromatography (TLC), high performance liquid chromatography (HPLC), mass spectrometry (MS) and serum assays. The temporal profiles of breeding and nonbreeding females will be statistically compared and pregnancy rate (in breeding females) will be recorded. The data will be analysed to characterise the normal hormonal profiles during the reproductive cycle, pregnancy and lactation. The reproductive parameters determined will help to enhance the productivity of the rodent in captivity.

Natural Entrainment of Circadian Rhythms in the Arctic ground squirrel, Spermophilus parryii

Timothy J. Martin and Brian M. Barnes

Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775.

Abdominally implanted temperature loggers and light-sensitive radio collars were used in the field to measure circadian rhythms of the Arctic ground squirrel (Spermophilus parryii) during the active season, including periods with 24 hours of daylight. Preliminary observations and telemetry data show that squirrels are not above ground to observe rapid light-dark (LD) transitions produced by dawn and dusk. The classical phase response model for circadian entrainment by LD pulses cannot explain how squirrels entrain to the natural LD cycle. The role of other aspects of light as potential zeitgebers is presently being investigated.

Response of blubber lipid chemistry to a low and variable food supply in the Bowhead whale.

Tamara L. Mau and Michael A. Castellini

Institute of Marine Science, University of Alaska Fairbanks, AK 99775

The lipid rich blubber layer of baleen whales serves as an important energy store. Changes in the relative thickness and lipid content of blubber are indicative of its nutritional status and body condition. Most whales fatten seasonally in response to a changing food supply and energetic demands associated with other functions of blubber including insulation, adjusting buoyancy and streamlining. The Bowhead whale has the thickest blubber of all whales, ranging from 10-50 cm, which extends beyond the thickness necessary for thermoregulation. Thus, overinsulation may be a trade-off for an increase in energy reserves, which provides a buffer during periods of low food supply.

We measured blubber thickness at six sites and blubber quality at six sites and five depths in Bowhead whales as they migrated past Point Barrow, AK in both spring and fall. We looked at factors that could affect blubber thickness and quality by comparing samples across season, age, sex and reproductive status. Blubber thickness was positively correlated and lipid content negatively correlated with total body length. Mean lipid content ranged from 68-87% and varied by both site and depth. Season was an important factor and lipid contents were generally higher in fall than in spring. Middle depths were high in lipid and stable across season, perhaps serving as a long-term reserve, whereas inner depths were quite variable and are probably the most important for active fat utilization.

The pericardial neurohemal organ in the abdomen of the tsetse fly and other cyclorraphan flies.

Shirlee Meola, Peter Langley and Helga Sittertz-Bhatkar

Institutions: USDA, ARS, Knipling-Bushland Insect Research Laboratory, Kerrville TX; University of Wales, Cardiff,UK; Texas A&M University, College Station,TX

The ventral surface of the tubular heart of cyclorraphan flies is supported by a dorsal (pericardial) septum that is anchored to the
sclerites by alary muscles. Unlike other insects, the pericardial septum of these flies contains a central band of longitudinal muscles. A histological study of the abdominal aorta in several species of cyclorraphan flies, revealed this longitudinal muscle is present in adults, but not the larval stage and extends beneath the heart from the 1st to the 5th abdominal segment. Four pairs of alary muscles insert on the ventrolateral surface of the longitudinal muscle, resulting in a pericardial sinus separate from the hemocoel. An ultrastructural study of the pericardial septum and sinus of the tsetse fly, Glossina morsitans, as well as the stable fly, Stomoxys calcitrans and another muscid, Orthellia caesarion, determined that neurosecretory fibers arising from the segmental nerves not only innervate the fibers of the longitudinal muscle, but extend between the muscle fibers, into the pericardial sinus where they release their products. In the tsetse fly, in addition to pericardial release, the neurosecretory fibers extend between the fibers of the myocardium and terminate in the lumen of the aorta. Thus the pericardial sinus of the adult flies was found to be a large neurohemal site in which the counter contractions of the circular muscles of the heart and the longitudinal muscle of the pericardial septum provide a forceful means of distributing neurosecretory material throughout the abdomen of the reproductive stage of these insects.

Regulation of circulation in insect by pumps, diaphragms and the coelopulse system.

Thomas A. Miller

Entomology Department, University of California, Riverside, CA

Insects have evolved mechanisms and strategies to ensure complete circulation of the hemolymph (Miller, 1997). The extent of the innovations in accessory pulsatile organs that perfuse appendages in insects is evident in the recent article by Pass (2000). The appendages in most insect pupae are not supplied by special circulatory organs, instead the hemocoelic pressure system (Slama, 2000) appears to assist in perfusion of hemolymph in all parts of the body. The pressure pulses appear to play a key role in respiration as well (Slama, 1999). The fact that respiration and circulation in insects are functionally connected was made clear by the work of Wasserthal (1996). Both ventilation movements and circulation movements are probably controlled by an autonomic nervous system (the coelopulse). The components of this system are only just being described, but probably are capable of great sophistication in directing hemolymph flow.

Miller, T.A. (1997) Control of circulation in insects. Gen. Pharmacol. 29: 23-38.
Pass, G. (2000) Accessory pulsatile organs: evolutionary innovations in insects. Ann. Rev. Entomol. 45: 495-518.
Slama, K. (2000) Extracardiac versus cardiac haemocoelic pulsations in pupae of the mealworm (Tenebrio molitor L.). J. Insect Physiol. 46: 977-992.
Slama, K. (1999) Active regulation of insect respiration. Ann. Entomol. Soc. Am. 92: 916-929.
Wasserthal, L. T. (1996) Interaction of circulation and tracheal ventilation in holometabolous insects. Adv. Insect Physiol. 26: 297-351.

Myoactive peptides and their role in cardio-regulation: conservation of activity and structure.

Janna Merte and Ruthann Nichols

University of Michigan, Biological Chemistry Department, Ann Arbor, MI, USA 48109-1048, nicholsr@umich.edu

To understand the roles and mechanisms of actions of myotropins, we are elucidating their structures, distributions, and activities. Drosophila melanogaster FDDY(SO3H)GHMRFamide (sulfakinin I, DSK I), TDVDHVFLRFamide (myosuppressin, DMS), SDNFMRFamide, and pEVRYRQCYFNPISCF (flatline, FLT) represent four structurally distinct myotropic peptide families.
DSK I, DMS, and SDNFMRFamide all contain a RFamide C terminus and, thus, by definition are FMRFamide-related peptides (FaRPs). The FaRP superfamily can be divided into subgroups including sulfakinins, myosuppressins, and FMRFamide-containing peptides. Sulfakinins have the consensus structure -XDY(SO3H)GHMRFamide, where X is E or D. Likewise, myosuppressins have a high degree of structure identity with the consensus structure XDVDHVFLRFamide, where X is pE, P, or T. In contrast, FMRFamide-containing peptides, like SDNFMRFamide, have a common C-terminal FMRFamide, but distinct N-terminal extension. The high degree of structure identity for sulfakinins and for myosuppressins suggests their N-terminal structures are critical for activity and justifies the subdivision of FaRPs.
FLT and other Manduca allatostatin (Mas AS)-like peptides have the consensus structure pEVRXRQCYFNPISCF, where X is F or Y. FLT structure is significantly different from DSK I, DMS, and SDNFMRFamide. FLT is not a FaRP and does not contain a C-terminal amide. These myotropins have non-overlapping cellular distributions in the central nervous system, which suggests different regulatory mechanisms affect their synthesis and release. Myotropins affect heart rate albeit with different magnitudes and different time-dependent responses. The differences among these myotropin structures, distributions, and activities suggest they have different signaling pathways and correspondingly different biological functions.

The effect of neem oil on lipid metabolism and respiration on the locust Locusta migratoria.

Søren N. Laursen and Hans Ramløv

Dept. of Life Sciences and Chemistry, Build. 18.1, P.O. Box 260, Roskilde University, DK-4000 Roskilde, Denmark
(hr@virgil.ruc.dk)

Due to their adaptations to dry environments, to long migratory flights and their ability to change from a solitary to a gregarious phase, locusts are a serious pest problem in countries in semi-arid and arid zones. Some plant species contain substances, which repel the locusts from eating them. One of these plants is the Neem tree Azadirachta indica. This tree contains the substance azadirachtin, which has been shown to interfere with the hormonal regulation of flight metabolism by inhibiting the release of diacylglycerol from the fat body in locusts. It has further been shown that prolonged flight activity in the locust Locusta migratoria is associated with a change in the utilization of trehalose as an energy source to diacylglycerol, despite a continuous availability of trehalose.
The overall physical condition of an animal is closely related to its energy metabolism, which can be measured by respirometry.
In the present study we present results showing that the application of Neem-oil containing 50 ppm azadirachtin to the cuticle of L. migratoria affected oxygen consumption of resting animals significantly. Exposed animals used oxygen at a rate of 208.8 31.3 µl O₂/g/hour whereas the controls used oxygen at a rate of 320.6 + 69.8 O₂/g/hour.
The results further showed that treatment with neem oil containing 50 ppm azadirachtin strongly affected the locusts ability to mobilize lipids for long term (30 min) flights. There was observed no effect of the Neem-oil on the animals ability to mobilize carbohydrates i.e. trehalose.
The observations presented here indicate that Neem-oil containing azadirachtin has an effect on the the release of neurohormones from the corpus cardiacum responsible for regulating metabolic activity.

Effect of bradykinin and related peptides on the vascular smooth muscle of the Atlantic cod, Gadus morhua

Fatemeh Shahbazi¹, J. Michael Conlon², Susanne Holmgren¹, and Jörgen Jensen^1
1Department of Zoophysiology, Göteborg University and
²Department of Biomedical Sciences, Creighton University Medical School, Omaha, U.S.A.
(fatemeh.shahbazi@zool.gu.se)

Mammalian bradykinin (BK) is a nonapeptide, which is cleaved from the inactive precursor high-molecular-mass kininogen by the enzyme kallikrein. Kinins are well known to exert a wide variety of biological effects by interacting with two different receptors, termed B₁ and B₂. The biological response to BK and related peptides in mammals consists of e.g. decrease arteriolar resistance and increased vascular permeability. In the present study the vasoactive effects of cod-BK ([Arg⁰, Trp⁵, Leu⁸]-BK) were investigated on isolated small branches of the cod celiac artery, using a myograph apparatus. Cod-BK (3x10^-8 M) induced vasorelaxation of the celiac artery precontracted with adrenaline (3x10^-7 M). The leukotriene synthesis (lipoxygenase) inhibitor, esculetin or the inhibitor of nitric oxide synthesis, N^G-nitro-L-arginine methyl ester (L-Name) had no effect on the response to cod-BK indicating that the vasodilation does not involve leukotrienes or nitric oxide. However, indomethacin, the cyclooxygenase inhibitor, completely abolished the effect of cod-BK suggesting that this effect is mediated by release of prostaglandins. Results from studies using structural analogs to cod-BK indicate that the cod bradykinin receptor have binding properties similar but not identical to the mammalian B₂ receptor.

Ultraviolet colour vision in birds: inferring physiology and perception from behaviour.

Emma Smith and Verity Greenwood.

Department of Biological Sciences, University of Bristol, Bristol, BS8 IUG, UK

The degree of colour vision that an animal possesses depends largely on the number of types of cone photoreceptors with differing sensitivities in its retina, and upon how the outputs of those receptors are processed within the brain. The sensation we think of as ‘colour’, or hue, is reliant on our ability to discriminate between different wavelengths of light. This discrimination is achieved by opponent coding, which compares the relative output of different cone types in response to a stimulus. The sensation of brightness, however, arises from the brain adding up the responses of all types of photoreceptor to work out how much light of all wavelengths is reflected by the stimulus. Both humans and birds have long, medium and short wavelength sensitive cones. In addition, birds generally have a violet sensitive cone that confers sensitivity to ultraviolet wavelengths (many non-passerines, for example, poultry and ducks) or a cone that is maximally sensitive to u! ltraviolet (notably passerines, for example songbirds). Birds have been shown to respond behaviourally to the presence or absence of ultraviolet, but it was unknown what type of perceptual experience ultraviolet vision would give the bird. The output of the violet/ultraviolet cone may simply be added to the output of the other cone types, which would make objects that reflect ultraviolet look brighter. If, however, the output is compared with the output of other cone types, it would enable birds to see ultraviolet as a separate hue. To investigate this, we have used psychophysical techniques based around associative learning to develop an ultraviolet ‘colour blindness’ test, which we have given to poultry (Japanese quail) and songbirds (European starlings). It appears that the output of the violet/ultraviolet cone is opponently coded, as both species appear to perceive ultraviolet as a separate hue.

Assimilation efficiency in two herbivorous animals: a comparison

Getachew Teferra

Department of Biological Sciences, University of Botswana, Pvt. Bag 00704, Gaborone, Botswana

The abilities of two herbivorous animals (Oreochromis niloticus and larvae of Imbrasia belina) to digest and absorb nutrients (Assimilation efficiency) from their guts were studied. Oreochromis niloticus mainly feeds on phytoplankton and the larvae of I. belina feeds on leaves of Mophane (Colophospermum mophane) and Morula (Sclerocarya birrea) trees. The level of organic matter in the diet of fish (100-600 mg/g D.M.) and assimilation efficiency (9.6-44%) were variable and an increase in the level of organic matter in the diet of fish resulted in an increase in assimilation efficiency. The organic content in the diet of the larvae was consistently high (>900 mg/g D.M.) but assimilation efficiency was not correspondingly high. The highest assimilation efficiency computed for these larvae was 36 ± 3.3%. This indicated that the organic material that is susceptible for digestion was relatively high in phytoplankton than in vascular plants. In I. belina, the old larvae (5th instars) assimilated better when fed Mophane leaves but there were no significant differences in assimilation efficiency between the old (5th instars) and young larvae (2nd instars) when fed Morula leaves. In this study, it has been shown that the level of organic matter and digestible organic matter in the diet limit assimilation efficiency in fish and larvae, respectively. As a result, both animals have only achieved about 40% maximum efficiency. Thus, the study of factors that optimise assimilation efficiency becomes essential in animal production.

Heat tolerance of an African ant: a possible record prompts a systematic critique of varying methodologies

Robbin Turner

University of Nevada, Las Vegas, Department of Biological Sciences, 4505 Maryland Parkway, Las Vegas, NV 89154, USA

In a desert, the extreme stresses of heat load and water deficit join with those of predation and competition to define the functional foraging niches of its species. Competition and predation can be diminished by utilizing a thermal window that more physiologically-limited species avoid. Those that can, do well, harvesting for themselves potential “heatfall.” Insects exhibit the highest heat tolerance among land animals; among insects the ant is currently declaimed as the “most thermo-tolerant” by Wehner, Marsh and others in studies of African and Australian species that determine the “critical thermal maximum” (CTmax) and tolerance ranges for each species. The biochemical mechanisms which drive such behavioral strategies are incompletely understood but may have broad application. Although the desert ant is diverse in kind and broad in geographic distribution, the accumulated physiological data on its thermal traits is also sparse, neglectin! g a field of New World, Old World and as yet un-typed candidates. In Part I of this study, thermal parameters of a heretofore unstudied (probable type-specimen) arid savannah Myrmicine, Ocymyrmex sp. were measured in the field. The CTmax of this species at 55 ºC may equal or surpass the record noted for the Saharan species Cataglyphis bombycina or its Australian Formicine cousin, Melophorus spp. In addition, survival time at 55 °C is significantly increased by prior exposure to high temperatures. How is such information best used? Do we seek to know absolute physiological limits or how such limits interface with ecological factors? An analysis of the implications of such a singular claim for highest heat tolerance should include a close examination of the progressive methods used to acquire the CTmax as well as CTmin. Different methods may induce and/or incorporate a different biochemical history and thus elicit variation in results. Her! e, in Part II, a parallel study of one Mojave desert ant, Pogonomyrmex rugosus compares the results of two differing methodologies, that of traditional progressive ramping of temperatures and that of abrupt immersion - after preconditioning - into a given temperature. The implications of different rates of temperature change are evaluated in light of the thermal time constant of the ant. Although standardization of the criteria used to measure such a critical adaptation serves consistency, it may also follow that distinctive methods of acquiring CTmax and CTmin may serve to indicate a range of biochemical “options” - dependent on conditions – which are potentially available to the animal.

Comparison of rumen fill and rate of passage in reindeer and muskoxen fed a common diet: Digestive strategies and competitive interactions.

Donald E. Spalinger1, Robert G. White2 and Pamela Groves2.

1 Department of Biology, University of Alaska Anchorage and Alaska Department of Fish and Game, Anchorage, AK99518
2 Large Animal Research Station, Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks AK 99775

Caribou and muskoxen are potentially competitive foragers, yet little is known of the way they digest common food types, information we must have to interpret diet use and preference in northern ecosystems. We hypothesized that reported differences in rumen fill and passage rates between caribou/reindeer (85kg) and muskoxen (250kg) are a function of diet and level of intake, and not a function of difference between an intermediate feeder and a grazer, sensu Hoffman. We fed a common diet (25% chopped Brome hay/ 75% concentrate pellets) at four levels of DM intake (1.3 - 3.3% BW) to rumen-cannulated reindeer (RD, 2 ad. females) and muskoxen (MO, 2 cast. males). Rumen DM fill (RDF, g/kgBW), liquid fill (RLF, l/kg BW), liquid passage rate (LPR, /h) and liquid outflow (LO, ml/h) were determined with pulsed intraruminal doses of Co-EDTA. Relative rumen fill was not different between RD and MO (RDF 13.2v14.0) (RLF 135v133), contrary to the grazer-browser hypothesis of Hoffman. T! he absolute difference in fill (RD<MO) was proportional to BW differences. DM fill/DM intake for RD (0.57) was less than MO (0.81 P<0.05). In absolute units, RDF (kg) increased with intake (kg/d) in separate regressions for RD and MO. This contrasted with absolute rumen liquid fill. Absolute RLF (l) for RD was independent of intake; whereas a linear increase was noted for MO. LPR of RD exceeded MO (0.112v0.076, P<0.05). LPR increased with intake in RD but not in MO. Although LO for RD was less than MO (1115v2043, P<0.01), a common interspecies regression related LO (Y) to DM intake (X): Y=358X+434 (R2=0.46). Liquid flow rate drives much of the passage of particulate matter from the rumen, thus DM flow likely parallels liquid flow. Since LPR of RD>MO, particulate matter of this diet should have a longer relative residence time in MO; therefore we should expect MO to digest fiber more efficiently (i.e. more completely) than RD when feeding at similar intake rate! s. Further, since LPR increases with DM intake in RD, we expect ruminal digestion of particulate matter to vary with intake in RD but to remain relatively constant with intake in MO.

Does insulin affect meal size and feeding frequency during down-regulation of food intake in winter?

Raphaela Stimmelmayr and Robert G White.

Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775.

Voluntary food intake (VFI) of caribou and reindeer is down-regulated in winter, and feeding is characterized by small, regular meals during daylight and irregular and sometimes large nighttime meals. Whereas daytime meal size approximates the energy deficit incurred since the previous meal, suggesting a role for insulin and glucose in appetite control, the occasional oversized nighttime meals suggests periodic deregulation of appetite. We hypothesized that nocturnal melatonin secretion could upset the meal size- intermeal interval mechanism by an effect on insulin secretion or a decline in sensitivity to insulin at night. In the present study a low daily insulin dose resulted in a slight rise in circulating levels of insulin and lactate in 5 pregnant female reindeer compared with 5 control animals given isotonic saline. We expected that this insulin effect would result in a more regular feeding throughout the day, and possibly would result in a decline in VFI. Exogenous ! insulin prevented an up-regulation of VFI during a warming trend, and, tended to counter a linear decline in body mass and backfat depth (measured by ultra-sound) typified by control animals. Effects of exogenous insulin on feeding behavior were small, and did not eliminate daytime-nighttime differences in meal size and frequency of feeding. Thus, as judged by its affect on VFI during the warming trend, insulin exerts a role over VFI, but how strongly insulin controls meal size in short-term appetite regulation was not answered by this study. We did not predict the influence of insulin over energy retention as judged by trends in backfat thickness. We suspect that chronically increased circulating levels of insulin may stimulate the Cori Cycle resulting in both the conservation of glucose carbon and provisioning reducing units (NADPH) for lipid synthesis through the Pentose Phosphate Cycle. In the wild a ready availability of highly preferred lichens, frozen mushrooms or per! haps muskrat “pushups” could provide the stimulus for increased insulin secretion in winter and thus variation in insulin levels could account for some of the observed high variability in overwinter fat use and conservation in caribou.

Phenoloxidase activity of arthropod hemocyanins: evolution of copper-oxygen proteins

Terwilliger, N., Ryan, M., Jaenicke, E. and Decker, H.

Oregon Institute of Marine Biology, University of Oregon, Charleston, USA; Institute of Molecular Biophysics, University of Mainz, Mainz, Germany.

Members of the hemocyanin gene family play vital roles during arthropod molting, including transport of oxygen to the tissues to support enhanced protein synthesis, transport of proteins for inclusion in the new exoskeleton, and incorporation of oxygen into substrates for hardening or sclerotization of the exoskeleton. Sclerotization in insects is initiated by phenoloxidase. Phenoloxidases (EC 1.14.18.1) are found in fungi and plants as well as animals, and they are involved in wound healing, in skin pigmentation and in the browning of plants. Several sequences of phenoloxidases from arthropods have been published recently that show phenoloxidases are related to arthropod hemocyanins. Hemocyanins from arthropods, well known as oxygen transport molecules, have been shown to function as phenoloxidases under some conditions[1-3]. Here, we show that hemocyanins from two ancient chelicerates, the horseshoe crab, Limulus polyphemus, and the tarantula, Eurypelma californicum, have @-phenoloxidase activity induced by submicellar concentrations of SDS. The enzyme activity is restricted to a few of the heterogeneous subunits, those that share similar topological positions in the quaternary structures of these huge hemocyanins. No other phenoloxidase activity has been found in the hemolymph of these animals, suggesting that their hemocyanins are involved in oxygen transport and in the primary immune response and sclerotization of the exoskeleton. In contrast, hemolymph from a more recent arthropod, the crustacean Cancer magister, contains a hemocyanin with slight phenoloxidase activity and another hemolymph protein with stronger phenoloxidase activity. Those hemocyanin subunits in chelicerata that function as linkers in the four to eight hexamer aggregates and have phenoloxidase activity may have evolved into separate @-diphenoloxidases in crustaceans, whose hemocyanins lack these linker subunits.
This work was supported by NSF 9984202 (NBT) and the NMFZ Mainz (HD).

1. Decker, H. and N. Terwilliger, COPs and robbers: putative evolution of copper oxygen binding proteins. J. Exp. Biol. 2000. 203: 1777-1782.
2. Nagai, T. and S. Kawabata, A link between blood coagulation and prophenol oxidase activation in arthropod host defense. J. Biol. Chem. 2000. 275(38): 29264-7.
3. Decker, H., Ryan, M. Jaenicke, E. and Terwilliger, N., SDS induced phenoloxidase activity of hemocyanins from Limulus polyphemus, Eurypelma californicum and Cancer magister. J. Biol. Chem. Feb. 15, 2001 as 10.1074/jbc.M010436200..

Central ganglionic vascularization of the isopod crustacean, Bathynomus doederleini.

Kosuke Tanaka¹, Yoko F.-Tsukamoto², and Kiyoaki Kuwasawa²

¹Department of Biology, Kyorin University School of Medicine, Mitaka, Japan, ²Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Japan
ktanak@kyorin-u.ac.jp

Decapods have a rich capillary system within all the central ganglia (Sandeman, 1967) although decapods have an open circulatory system. We studied the vascular system for the central ganglia of an isopod Bathynomus doederleini. There are thirteen arteries arising from the heart, three anterior arteries and five pairs of lateral arteries. The anterior median artery runs to the cephalon, where the cerebral ganglion is supplied arterioles from the cor-frontale. Arterioles from the first lateral artery (LA1) extend to the second to fifth thoracic ganglion (TG2-TG5). Arterioles from LA2, LA3 and LA4 extend to TG6, TG7 and TG8, respectively.
We performed anatomical and histological studies of arterioles supplying the central ganglia, by means of injection of inks through the heart or arteries and then making paraffin sections of the central nervous system. In the cerebral ganglion, the lumen between periganglionic sheath and epiganglionic sheath and channels extruding into the neuropil were filled with injected ink. In the thoracic ganglia, the lumen between the periganglionic sheath and epiganglionic sheath was filled with injected ink, but channels filled with ink were not observed in the neuropil of the ganglion. These results suggest that, in Bathynomus, arterioles open in the lumen between the periganglionic sheath and epiganglionic sheath and there are some blood channels extending into neuropil in the cerebral ganglion. Indeed, when the thoracic ganglia were perfused through these arterioles with saline containing humoral substances, the perfusates effectively exerted influence on neurons in the thoracic ganglia.

Cardiac pacemaker mechanism in the ostracod crustacean Vargula hilgendorfii

Yukiko Ishii and Hiroshi Yamagishi

Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
( yamagishi@biol.tsukuba.ac.jp)

To explore diversity of cardiac pacemaker mechanism in crustaceans, the heartbeat of the ostracod V. hilgendorfii, one of the lower orders within the Crustacea was examined electrophysiologically. The heart is single chambered and composed of a single layer of myocardial cells characterized by localization of myofibrils at the epicardial site. A single neuron situated on the outer surface of the dorsal heart wall sends an axon into the heart wall and the axon is branched widely forming many neuromuscular junctions on the myocardial cells. The frequency of the heartbeat changes widely and each heartbeat follows a myocardial action potential composed of a spike and plateau potential. The myocardial cells couple electrically and fire almost synchronously. By application of 1 µM TTX, the action potential of the myocardium disappeared, the myocardial membrane depolarized and oscillatory slow potentials often appeared. The frequency of the action potential was almost unchanged during injection of a depolarizing or hyperpolarizing current pulse into the myocardium. When the myocardial membrane was depolarized by the current the oscillatory slow potentials appeared in addition to the action potentials and its frequency was higher with stronger intensities of the current. The results suggest that, though the myocardial cell has conditional oscillatory properties, the heartbeat of V. hilgendorfii is basically neurogenic with the single motor neuron in the heart acting as a pacemaker.

The circulatory organs in myriapods: comparative morphology and physiology

Wirkner C.S. 1), Hertel W. 2), Pass G. 1)

1) Institut für Zoologie, Universität Wien, A-1090 Vienna, Austria
2) Institut für Allgemeine Zoologie und Tierphysiologie, Friedrich-Schiller-Universität Jena, D-07743 Jena, Germany

Within the recent debate on arthropod phylogeny myriapods play a crucial role. The present paper deals with the circulatory system of all high-rank taxa of myriapods, with exception of Pauropoda which lack circulatory organs at all. The morphologies of the circulatory organs were investigated in representative species by means of semithin sections and combined with data from the literature.
Among myriapods, the vascular system exhibits a wide range of complexity. In chilopods, the circulatory system consists of two longitudinal central vessels: the dorsal vessel and the ventral vessel. In the first body segment, the maxilliped arch connects these two vessels. From the longitudinal vessels peripheral arteries branch off which supply long body appendages or sinuses. In Scutigeromorpha, the circulatory system is closely linked with respiratory tasks by physiological and morphological features (e.g. hemocyanin, close spatial relation of heart and tracheal lungs, high-performance heart). In diplopods, there is only a longitudinal dorsal vessel. Ventrally, the blood flows in a perineural sinus. Peripheral vessels branchig off the dorsal vessel supply the antennae and sinuses. In symphylans, both a dorsal and a ventral vessel occur which are connected by an unpaired vessel. Peripheral arteries supply long body appendages and sinuses.
Physiological literature on myriapod circulatory organs is very scarce and we present the first electrophysiological data from the dorsal vessel of chilopods. Results are discussed from phylogenetic as well as from general evolutionary points of view.