Plasma glucocorticoid concentrations in free-ranging platypuses (Ornithorhynchus anatinus): response to capture and patterns in relation to reproduction

Energy demands in the platypus are likely to increase in the breeding season, which occurs from winter to early spring. Glucocorticoids, which play a major role in energy mobilisation, were measured in consecutive blood samples from free-ranging adults at approximately monthly intervals throughout the year. Glucose and free fatty acids were also measured in some samples. Plasma concentrations of glucocorticoids rose significantly during the first 30 min after capture, accompanied by a rise in free fatty acids, but no corresponding increase in glucose concentrations. We observed a strong pattern in plasma glucocorticoids in samples collected within 15 min of capture (indicative of pre-disturbance concentrations) in different phases of the annual reproductive cycle, with significantly higher levels in both males and females in the breeding season compared to the non-breeding season. These data, and the decline in tail fat stores that occur towards the end of the mating period (around October), suggest that platypus experience high-energy demands during this phase of reproduction. Plasma glucocorticoid concentrations in females sampled during the lactation period (October-February) were relatively low, and similar to those in females sampled in the non-breeding, non-lactation period (March-June). The latter requires further investigation as results may have been influenced by sampling limitations.     

Diving behaviour of dugongs, Dugong dugon

The diving behaviour of 15 dugongs (Dugong dugon) was documented using time-depth recorders (TDRs), which logged a total of 39,507 dives. The TDRs were deployed on dugongs caught at three study sites in northern Australia: Shark Bay, the Gulf of Carpentaria and Shoalwater Bay. The average time for which the dive data were collected per dugong was 10.4±1.1 (S.E.) days. Overall, these dugongs spent 47% of their daily activities within 1.5 m of the sea surface and 72% less than 3 m from the sea surface. Their mean maximum dive depth was 4.8±0.4 m (S.E.), mean dive duration was 2.7±0.17 min and the number of dives per hour averaged 11.8±1.2. The maximum dive depth recorded was 20.5 m; the maximum dive time in water >1.5 m deep was 12.3 min. The effects of dugong sex, location (study site), time of day and tidal cycle on diving rates (dives per hour), mean maximum dive depths, durations of dives, and time spent ≤1.5 m from the surface were investigated using weighted split-plot analysis of variance. The dugongs exhibited substantial interindividual variation in all dive parameters. The interaction between location and time of day was significant for diving rates, mean maximum dive depths and time spent within 1.5 m of the surface. In all these cases, there was substantial variation among individuals within locations among times of day. Thus, it was the variation among individuals that dominated all other effects. Dives were categorised into five types based on the shape of the time-depth profile. Of these, 67% of dives were interpreted as feeding dives (square and U-shaped), 8% as exploratory dives (V-shaped), 22% as travelling dives (shallow-erratic) and 3% as shallow resting dives. There was systematic variation in the distribution of dive types among the factors examined. Most of this variation was among individuals, but this differed across both time of day and tidal state. Not surprisingly, there was a positive relationship between dive duration and depth and a negative relationship between the number of dives per hour and the time spent within 1.5 m of the surface after a dive.     

Physiological and behavioral determinants of the aerobic dive limit in Weddell seal (Leptonychotes weddellii) Pups

The aerobic dive limit, as defined by an increase in plasma lactate levels following dives, has to date only been determined in adult and juvenile Weddell seals (Leptonychotes weddellii). However, theoretical aerobic dive limits based on calculated total body oxygen stores, estimated metabolic rates, and dive duration frequencies have been published for several species. Using data collected over the past 3 years in McMurdo Sound. Antarctica, the aerobic dive limit of Weddell seal pups was determined by both the physiological and modeling methods. Time-depth diving recorders deployed on 36 pups between 2 and 14 weeks of age allowed the aerobic dive limit to be predicted from duration-frequency histograms. The aerobic dive limit was also calculated from estimates of total body oxygen stores and predicted diving metabolic rates. Finally, these two estimates were compared with aerobic dive limits determined from post-dive lactate levels in three pups between 5 and 7 weeks old. The aerobic dive limits of pups increased with age, but pup aerobic dive limits were still significantly shorter than those of yearlings and adults. In addition, the aerobic dive limits determined by the three methods were not equivalent for pups, yearlings, or adults, and indicate that care should be taken when modeling methods are used to estimate the aerobic dive limit in other species. Changes in hematocrit, plasma glucose, and plasma lactate levels during and between rest, diving, and recovery in pups were compared to known values for juveniles and adults. Plasma metabolite levels were more highly regulated in older pups, and together with the increasing aerobic dive limit, suggest that Weddell seal pups are not refined divers until after they are weaned, and that their diving ability continues to develop over several years.     

Distribution of substance P in the enteric plexuses of the small intestine of the platypus,Ornithorhynchm anatinus

Summary A study was made of substance P-like-immunoreactive nerves within the small intestine of platypus, an Australian prototherian mammal. Both immunoreactive nerve cell bodies and fibres were present. No immunoreactive fibres were found in mesenteric nerves or on intramural blood vessels, suggesting that extrinsic sensory neurons containing substance P do not innervate platypus ileum. This was further supported by the result of in vitro experiments. Although applied substance P (10^-9 M-3 × 10^-8 M) caused contraction of the longitudinal muscle, neither mesenteric nerve stimulation nor application of capsaicin caused contractions.     

Temperature regulation in emperor penguins foraging under sea ice

Inferior vena caval (IVC) and anterior abdominal (AA) temperatures were recorded in seven emperor penguins (Aptenodytes forsteri) foraging under sea ice in order to evaluate the hypothesis that hypothermia-induced metabolic suppression might extend aerobic diving time. Diving durations ranged from 1 to 12.5 min, with 39% of dives greater than the measured aerobic dive limit of 5.6 min. Anterior abdominal temperature decreased progressively throughout dives, and partially returned to pre-dive values during surface intervals. The lowest AA temperature was 19 degrees C. However, mean AA temperatures during dives did not correlate with diving durations. In six of seven penguins, only minor fluctuations in IVC temperatures occurred during diving. These changes were often elevations in temperature. In the one exception, although IVC temperatures decreased, the reductions were less than those in the anterior abdomen and did not correlate with diving durations. Because of these findings, we consider it unlikely that regional hypothermia in emperor penguins leads to a significant reduction in oxygen consumption of the major organs within the abdominal core. Rather, temperature profiles during dives are consistent with a model of regional heterothermy with conservation of core temperature, peripheral vasoconstriction, and cooling of an outer body shell.     

The diving behavior of blue and fin whales: is dive duration shorter than expected based on oxygen stores?

Many diving seabirds and marine mammals have been found to regularly exceed their theoretical aerobic dive limit (TADL). No animals have been found to dive for durations that are consistently shorter than their TADL. We attached time-depth recorders to 7 blue whales and 15 fin whales (family Balaenopteridae). The diving behavior of both species was similar, and we distinguished between foraging and traveling dives. Foraging dives in both species were deeper, longer in duration and distinguished by a series of vertical excursions where lunge feeding presumably occurred. Foraging blue whales lunged 2.4 (+/-1.13) times per dive, with a maximum of six times and average vertical excursion of 30.2 (+/-10.04) m. Foraging fin whales lunged 1.7 (+/-0.88) times per dive, with a maximum of eight times and average vertical excursion of 21.2 (+/-4.35) m. The maximum rate of ascent of lunges was higher than the maximum rate of descent in both species, indicating that feeding lunges occurred on ascent. Foraging dives were deeper and longer than non-feeding dives in both species. On average, blue whales dived to 140.0 (+/-46.01) m and 7.8 (+/-1.89) min when foraging, and 67.6 (+/-51.46) m and 4.9 (+/-2.53) min when not foraging. Fin whales dived to 97.9 (+/-32.59) m and 6.3 (+/-1.53) min when foraging and to 59.3 (+/-29.67) m and 4.2 (+/-1.67) min when not foraging. The longest dives recorded for both species, 14.7 min for blue whales and 16.9 min for fin whales, were considerably shorter than the TADL of 31.2 and 28.6 min, respectively. An allometric comparison of seven families diving to an average depth of 80-150 m showed a significant relationship between body mass and dive duration once Balaenopteridae whales, with a mean dive duration of 6.8 min, were excluded from the analysis. Thus, the short dive durations of blue whales and fin whales cannot be explained by the shallow distribution of their prey. We propose instead that short duration diving in large whales results from either: (1) dispersal behavior of prey; or (2) a high energetic cost of foraging.     

Diving at the shallow end: Green turtle behaviour in near-shore foraging habitat

Green turtles Chelonia mydas of immature and adult size (n = 19, curved carapace length 49 to 118 cm) were equipped with time-depth recorders for short periods (≤ 7 d) to investigate diel and seasonal variation in diving behaviour. Research sessions were distributed over 2 years to cover seasonal variation in sea temperature from 14 °C to 30 °C. Diurnal dives were shallower and shorter than nocturnal dives, with diel patterns also evident in dawn and dusk peaks in occupation of depths within 1 m of the surface, elevated diurnal occupation of depths 1 to 2 m below the surface and elevated nocturnal occupation of depths > 2 m. Dive duration increased as sea temperature decreased, showing strong negative correlation by day and by night. Study turtles made resting dives that were 3 to 4 times longer in median duration, and six times longer in maximum duration, at cool temperatures than they were at warm temperatures, but there was no evidence of winter diapause or location shift to avoid cold water. The large majority of turtles spent 89 to 100% of their time at depths ≤ 5 m below the surface, three individuals did not exceed 3 m and the maximum depth recorded by any turtle was 7.9 m, although deeper water was available. Furthermore, the dive data indicated that study turtles collectively spent more than 80% of their time at charted (low tide) depths of 3 m or less, indicating that they consistently used the shallow margins of the bay where human activities tend to be concentrated, thereby potentially increasing their exposure to anthropogenic threats.     

Sex-specific foraging behaviour in a seabird with reversed sexual dimorphism: the red-footed booby

Most hypotheses attempting to explain the evolution of reversed sexual dimorphism (RSD) assume that size-related differences in foraging ability are of prime importance, but the studies on sex-specific differences in foraging behaviour remain scarce. We compare the foraging behaviour of males and females in a seabird species with a RSD by using several miniaturised activity and telemetry loggers. In red-footed boobies males are 5% smaller and 15% lighter than females, but have a longer tail than females. Both sexes spend similar time on the nest while incubating or brooding. When foraging at sea, males and females spend similar time foraging in oceanic waters, forage in similar areas, spend similar proportion of their foraging trip in flight, and feed on similar prey—flying fishes and flying squids—of similar size. However, compared to males, females range farther during incubation (85 km vs. 50 km), and furthermore feed mostly at the extremity of their foraging trip, whereas males actively forage throughout the trip. Males are much more active than females, landing and diving more often. During the study period, males lost mass, whereas females showed no significant changes. These results indicate that males and females of the red-footed boobies differ in several aspects in their foraging behaviour. Although some differences found in the study may be the direct result of the larger size of females, that is, the slightly higher speeds and deeper depths attained by females, others indicate clearly different foraging strategies between the sexes. The smaller size and longer tail of males confer them a higher agility, and could allow them to occupy a foraging niche different from that of females. The higher foraging effort of males related to its different foraging strategy is probably at the origin of the rapid mass loss of males during the breeding period. These results suggest that foraging differences are probably the reason for the differential breeding investment observed in boobies, and are likely to be involved in the evolution and maintenance of RSD.     

Seasonal changes in the oxygen storage capacity and aerobic dive limits of the muskrat (Ondatra zibethicus)

Summary The oxygen storage capacity and partitioning of body oxygen reserves were compared in summer-and winter-acclimatized muskrats (Ondatra zibethicus). Blood volume, blood oxygen capacity, and skeletal muscle myoglobin content were higher in December than in July (P<0.02). Total lung capacity increased only slightly in winter (P>0.05). The oxygen storage capacity of a diving muskrat was calculated at 25.2 ml O₂ STPD · kg^-1 in July, compared to 35.7 ml O₂ STPD · kg^-1 in December. Blood comprised the major storage compartment in both seasons, accounting for 57% and 65% of the total oxygen stores in summer and winter, respectively. Based on available oxygen stores and previous estimates of the cost of diving, the aerobic dive limit (ADL) increased from 40.9 s in July to 57.9 s in December. Concurrent behavioral studies suggested that most voluntary diving by muskrats is aerobic. However, the proportion of dives exceeding the calculated ADL of these animals was shown to vary with the context of the dive. Only 3.5% of all dives initiated by muskrats floating in the water exceeded their estimated ADL. Provision of a dry resting site and access to a submerged food source increased this proportion to 18–61%, depending on the underwater distance that foraging muskrats were required to swim. Serial dives exceeding the estimated ADL were not accompanied by extended postdive recovery periods.Abbreviations ADL acrobic dive limit - Hb hemoglobin - Hct hematocrit - Mb myoglobin - PaO₂ arterial O₂ tension - STPD standard temperature and pressure, dry     

Ventilation and metabolic rate in the platypus: insights into the evolution of the mammalian breathing pattern

The platypus (Ornithorhyncus anatinus) is characterized by a rate of oxygen consumption (V(O2))that is higher than that reported for other similar sized monotremes, similar to marsupials and somewhat lower than eutherians. The platypus is also characterized by a breathing pattern, more typical of a diving mammal, with a high 'inspiratory drive' and a post-inspiratory pause. Further, the platypus reveals an attenuated hyperventilatory response to hypoxia and a reduced hyperpnoea to hypercapnia; such a response to these chemical stimuli is commonly observed in semi-fossorial and diving mammals. Nevertheless, under conditions of normoxia, ventilation (V(E))is matched to (V(O(2)) such that the convection requirement (V(E)/V(O2)) is similar to that reported for other mammals (approx. 37). The apparent consistency of the convection requirement in mammals suggests the blueprint for the design of the mammalian respiratory system has remained an interspecies constant in the three divergent extant sub-classes of mammals.     

Resource limitation,predation risk and compensatory growth in a damselfly

Periods of poor nutrition during early development may have negative fitness consequences in subsequent periods of ontogeny. In insects, suppression of growth and developmental rate during the larval stage are likely to affect size and timing of maturity, which in turn may lead to reduced reproductive success or survivorship. In light of these costs, individuals may achieve compensatory growth via behavioural or physiological mechanisms following food limitation. In this study, we examined the effects of a temporary period of food restriction on subsequent growth and age and size at maturity in the larval damselfly Ischnura verticalis (Odonata: Coenagrionidae). We also asked whether this temporary period of reduced nutrition affected subsequent foraging behaviour under predation risk. I. verticalis larvae exposed to a temporary food shortage suffered from a reduced growth rate during this period relative to a control group that was fed ad libitum. However, increased growth rates later in development ensured that adult body size measurements (head and pronotum widths) did not differ between the treatments upon emergence. In contrast, adult dry mass did not catch up to that of the controls, indicating that the increased growth rates for size dimensions occur at the cost of similar gains in mass. Predators reduced foraging effort of larvae, but this reduction did not differ between control larvae and those previously exposed to poor nutrition.     

Costs and benefits of freezing behaviour in the harvestman Eumesosoma roeweri (Arachnida, Opiliones)

Animals present an enormous variety of behavioural defensive mechanisms, which increase their survival, but often at a cost. Several animal taxa reduce their chances of being detected and/or recognized as prey items by freezing (remaining completely motionless) in the presence of a predator. We studied costs and benefits of freezing in immature Eumesosoma roeweri (Opiliones, Sclerosomatidae). Preliminary observations showed that these individuals often freeze in the presence of the syntopic predatory spider Schizocosa ocreata (Araneae, Lycosidae). We verified that harvestmen paired with predators spent more time freezing than when alone or when paired with a conspecific. Then, we determined that predator chemical cues alone did not elicit freezing behaviour. Next, we examined predator behaviour towards moving/non-moving prey and found that spiders attacked moving prey significantly more, suggesting an advantage of freezing in the presence of a predator. Finally, as measure of the foraging costs of freezing, we found that individuals paired with a predator for 2 h gained significantly less weight than individuals paired with a conspecific or left alone. Taken together, our results suggest that freezing may protect E. roeweri harvestmen from predatory attacks by wolf spiders, but at the cost of reduced food and/or water intake.     

Interference and competitive behaviour of the aphid predators,Chrysoperla carnea andCoccinella septempunctata in the laboratory

Interference and competition betweenChrysoperla carnea (Stephens) andCoccinella septempunctata L. was investigated in the absence and presence of aphid prey. When larvae of similar vigour encountered each other,C. carnea larvae were superior toC. septempunctata. Otherwise the larger of 2 individuals always killed the smaller. In the absence of preyC. carnea adults were attacked by their own 2nd and 3rd instar larvae as well as by 3rd instar larvae ofC. septempunctata. In all encounters the adults ofC. septempunctata were superior. Since the eggs ofC. carnea are protected to some extent by being on egg stalks, they were less susceptible to cannibalism and predation thanC. septempunctata eggs which are deposited in batches directly on plant leaves. In the presence of prey cannibalism and predation were reduced, especially between larvae. Only eggs and 1st instar larvae were endangered. In the present experimentsC. carnea showed a slight superiority overc. septempunctata. Paper presented at the 17th International Congress of Entomology held in August 20–26 1984 in Hamburg, F.R. Germany.     

Over-wintering strategies of the Lesser Sheathbill Chionis minor in an impoverished and insular environment

Summary The Lesser Sheathbill Chionis minor is an opportunistic predator and scavenger that breeds on sub-Antarctic islands during the summer season, when many other seabirds are present, especially penguins on which it is kleptoparasitic. It is a poor flyer and over-winters on its breeding grounds, where it faces a diminished food supply and low temperatures. Its foraging behaviour was suspected to be plastic enough to respond to such a variable environment, and we show how this species enlarged its niche to survive in winter. Population movements, dietary changes and monthly weight gains were quantified during a 13-month period of observation. Mortality rates, calculated over a 19-year period of banding, appeared to be age dependent: they decrease, due to competition, from juveniles to subadults, adult non-breeders, and breeders. One of the survival strategies described here is, to our knowledge, unique among birds. After the Crested Penguin colonies have been deserted, some adult sheathbills (mainly females) remained territorial, extending their territory size and diet while their partners moved to previously undefended zones in King Penguin colonies (permanent and large in the Crozet archipelago), where they competed for a winter territory and subsequently associated with another mate. After this winter mating, mobile sheathbills returned the following summer to their breeding territory and previous mate.     

Lysozyme gene expression and hemocyte behaviour in the Mediterranean mussel, Mytilus galloprovincialis, after injection of various bacteria or temperature stresses

The aim of the present study was to evaluate the expression of the Mytilus galloprovincialis lysozyme gene in different in vivo stress situations, including injection of bacteria Vibrio splendidus LGP32, Vibrio anguillarum or Micrococcus lysodeikticus, as well as heat shock at 30 degrees C and cold stress at 5 degrees C. Injection of V. splendidus LGP32 resulted in: (i) a general down-regulation of lysozyme gene expression, as quantified by Q-PCR; (ii) reduction in the number of circulating hemocytes; (iii) decrease in the percentage of circulating hemocytes expressing lysozyme mRNA which was now restricted to only small cells, as observed by ISH; and (iv) accumulation of hemocytes expressing lysozyme in the muscle sinus where injection took place. Injection of V. anguillarum or M. lysodeikticus induced significant up-regulation of lysozyme gene expression, but only 2-3days post-injection, with no change in the total hemocyte counts but an increased percentage of hemocytes expressing lysozyme mRNA. Neither the control injection of PBS-NaCl nor temperature stress modified the lysozyme expression pattern. Consequently, the hemocyte population appears to be capable of discriminating between stress factors, and even between 2 Vibrio species.     

Meiotic pairing behaviour reveals differences in genomic constitution between Hystrix patula and other species of the genus Hystrix Moench (Poaceae, Triticeae)

Interspecific and intergeneric hybridizations were carried out to evaluate the genomic relationships among species of Hystrix Moench and to study the relationships between Hystrix species and Psathyrostachys huashanica Keng (2n=2x=14, Ns^h). Meiotic pairing in hybrids of Hystrix duthiei ssp. duthiei × P. huashanica (2n=3x=21), Hystrix duthiei ssp. longearistata × P. huashanica (2n=3x=21) and H. patula × P. huashanica (2n=3x=21) averaged 5.18, 5.11 and 0.29 bivalents per cell, while H. patula × H. duthiei ssp. longearistata (2n=4x=28) averaged 25.36 univalents and 1.32 bivalents per cell, respectively. The results indicate that (i) H. duthiei ssp. duthiei and H. duthiei ssp. longearistata have one set of Ns genome from Psathyrostachys; (ii) H. patula has no Ns genome; (iii) genomes of H. duthiei ssp. duthiei and H. duthiei ssp. longearistata are non-homologous to those of H. patula. The genomic relationships between H. patula and other Hystrix species are also discussed.     

Hybrid disadvantage in the larval foraging behaviour of the two neotropical species of <Emphasis Type="Italic">Drosophila pavani</Emphasis> and <Emphasis Type="Italic">Drosophila gaucha</Emphasis>

Flies from two populations of the Chilean endemic neotropical species Drosophila pavani and two populations of its sibling species Drosophila gaucha were crossed reciprocally to obtain intra- and interspecific hybrids. The developmental pathways of locomotor activity and feeding rate were analysed for eleven of twelve possible genotype groups. The hybrids showed reduced fitness indicated by a decrease in the measured traits. Hybrid disadvantage was strongest in interspecific hybrids, especially with respect to feeding behaviour. This evidence supports the contention that D. pavani and D. gaucha have evolved different coadapted gene pools controlling the developmental pathways for behavioural traits expressed during larval foraging; but genetic divergence affecting these behaviours has also taken place between locally adapted populations within each species.     

Feeding behaviour and food selection in the horseshoe crab,Tachypleus gigas (Müller)

The Indian horseshoe crab, Tachypleus gigas (Müller), is a benthic feeder which subsists mainly on molluscs, decayed organic matter and polychaetes, in order of prevalence. A strong and positive preference was recorded for molluscs over other food organisms. The intensity of feeding was maximum during the north-east monsoon (November to January) in females and during the intermonsoon season (February to May) in males. It was minimum during the south-west monsoon (June to September).     

Mating and oviposition behaviour in the legume pod borer, Maruca testulalis

Experiments were conducted outdoors and in the insect rearing laboratory at the International Institute of Tropical Agriculture (IITA) in Nigeria. Four or five nights pairing duration gave the highest mating percentage and oviposition by the pod borer. Direct observations on adult mating revealed that some males mated more than once. The majority of females mated only once. A one-to-one ratio (with 10 males: 10 females) gave the best results for mating and oviposition. Mating took place between 21.00 h and 05.00 h when temperature ranged between 20–25°C and rh over 80% with peak activity occurring between 02.00 and 03.00 h. Oviposition followed a similar trend to that observed for mating with an equal sex ratio (of 10 or more pairs per cage) giving the highest egg count. The average number of eggs laid was ca. 400 per female. These results show a much higher oviposition potential for Maruca testulalis than has been previously reported. The results are discussed with regard to the rearing of this species under laboratory conditions.

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Accouplement et comportement de ponte de Maruca testulalis

Résumé Tant de l'extérieur qu'au laboratoire (à l'IITA au Nigéria), la durée optimale de maintien des couples de M. testulalis Geyer (Lep. Pyralidae) pour obtenir l'accouplement et la ponte a été de 4 à 5 nuits, toutefois les meilleurs résultats ont été obtenus à l'extérieur. L'observation directe a révélé que contrairement aux femelles, les mâles peuvent copuler plus d'une fois. Le meilleur rapport sexuel pour obtenir l'accouplement et la ponte est 1/1 (10 mâles/10 femelles), suivi de près par un raport avec excédent de mâles. L'accouplement a lieu entre 21 h et 5 h quand la température est entre 20 et 30°C et HR supérieure à 80%; un pic est observé entre 2 et 3 h. La ponte présente la même tendance que l'accouplement, avec une production d'ufs plus élevée pour au moins 10 couples par cage. Le nombre moyen d'ufs par femelle est environ 400. Ces résultats sont supérieurs à ce qui avait été indiqué précédemment. La discussion porte sur les difficultés rencontrées pour élever cette espèce au laboratoire.