Death in leopard geckos (Eublepharis macularius) following ingestion of vermiculite

This paper details the clinical and post-mortem findings of leopard geckos following ingestion of vermiculite bedding material. Death was attributed to the high magnesium content of the vermiculite.     

Heat tolerance, behavioural temperature selection and temperature-dependent respiration in larval Octopus huttoni

This study reports temperature effects on paralarvae from a benthic octopus species, Octopus huttoni, found throughout New Zealand and temperate Australia. We quantified the thermal tolerance, thermal preference and temperature-dependent respiration rates in 1-5 days old paralarvae. Thermal stress (1 °C increase h⁻¹) and thermal selection (∼10-24 °C vertical gradient) experiments were conducted with paralarvae reared for 4 days at 16 °C. In addition, measurement of oxygen consumption at 10, 15, 20 and 25 °C was made for paralarvae aged 1, 4 and 5 days using microrespirometry. Onset of spasms, rigour (CT_max) and mortality (upper lethal limit) occurred for 50% of experimental animals at, respectively, 26.0±0.2 °C, 27.8±0.2 °C and 31.4±0.1 °C. The upper, 23.1±0.2 °C, and lower, 15.0±1.7 °C, temperatures actively avoided by paralarvae correspond with the temperature range over which normal behaviours were observed in the thermal stress experiments. Over the temperature range of 10 °C-25 °C, respiration rates, standardized for an individual larva, increased with age, from 54.0 to 165.2 nmol larvae⁻¹ h⁻¹ in one-day old larvae to 40.1-99.4 nmol h⁻¹ at five days. Older larvae showed a lesser response to increased temperature: the effect of increasing temperature from 20 to 25 °C (Q₁₀) on 5 days old larvae (Q₁₀=1.35) was lower when compared with the 1 day old larvae (Q₁₀=1.68). The lower Q₁₀ in older larvae may reflect age-related changes in metabolic processes or a greater scope of older larvae to respond to thermal stress such as by reducing activity. Collectively, our data indicate that temperatures >25 °C may be a critical temperature. Further studies on the population-level variation in thermal tolerance in this species are warranted to predict how continued increases in ocean temperature will limit O. huttoni at early larval stages across the range of this species.     

Locomotor performance and social dominance in male Anolis cristatellus

The proximal mechanisms determining social dominance are not well understood. We used the highly territorial lizard A. cristatellus to test two main hypotheses: (1) that male social dominance is associated with locomotor abilities; (2) that locomotor abilities (maximal performance), as measured in the laboratory, are correlated with behaviour in the field. In the field, we recorded locomotor behaviours and assertion displays, then characterized microhabitat use and thermal relations. In the laboratory, we measured maximum sprint running speed, endurance and morphometric characters, and assessed dominance by pairing males of similar body size in an experimental arena. In 72 of 77 interactions, one lizard (the ‘winner’) was unequivocally determined to be dominant over the other (the ‘loser’). Winners performed more assertion displays than losers before capture and also had higher endurance in laboratory tests. Although contestants were matched for snout-vent length, winners had significantly deeper and wider heads. However, we found no significant differences in field locomotor behaviours, perch or thermal characteristics, head length, or maximal sprint speed. Our findings support those of previous studies, and extend them in several ways. This is the first demonstration that assertion displays in the field are related to both locomotor performance and laboratory-assessed social dominance. Locomotor performance may directly affect social dominance by allowing some males to perform better in dyadic interactions. Alternatively, both locomotor performance and social dominance may be linked to a common underlying mechanism, such as variation in hormone levels, which are known to affect aggression, locomotor performance and morphology.     

Female brown-headed cowbirds', Molothrus ater, organization and behaviour reflects male social dynamics

In four large aviaries, we studied social assortment and reproductive behaviour of female brown-headed cowbirds housed with males differing in age class and in corresponding levels of intrasexual interaction. Juvenile and adult females resided with either (1) adult males, (2) juvenile males, (3) adult and juvenile males, or (4) no males. We observed social behaviour of males and females from September 1999 through to the 2000 breeding season. Throughout the year, males in the different conditions showed different levels of social interaction, with adult males being most engaged in male-male interactions and juvenile males being least engaged in male-male interactions. Females in the four conditions differed in their associations with males and with other females. In conditions with adult males, females spent more time near males, approached males more often, and associated with females less. During the breeding season, females in conditions with more adult males copulated more and produced more fertile and viable eggs. In the condition where females were housed with juvenile males, they copulated less, laid fewer eggs and destroyed more of their eggs. Results indicate that throughout the year, females are sensitive to male age and behaviour in their social group, and that this sensitivity can have reproductive consequences. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Adult male emigration and a female-based social organization in swift foxes, Vulpes velox

Members of the family Canidae are distinguished from other carnivore families by pair bonding and male care of the young. Because of the importance of food provisioning and territorial defence by males, social structure among canids is shared or even dominated by males. However, small, insectivorous species of canids show little male parental care, although whether social structure differs from other canids is unknown. We combined data from three independent research projects on a small canid, the swift fox, to help elucidate the social organization of this species. Based on data on movements of 35 adult mated pairs and the fate of litters, we found that adult females maintained territories and family structure, whereas adult males tended to emigrate. This is the first evidence of a female-based social organization among any canid species. This type of social organization probably resulted from the decreased importance of territorial defence and food provisioning by males, as their diet is primarily insectivorous during summer when young are weaned. Our results, along with others, indicate that variations in social structure among canid species are strongly influenced by the importance of food provisioning and territorial defence by males.     

The effect of temperature change on gene expression in Paramecium primaurelia

When paramecia grown at 24°C are transferred rapidly to 32°C, DNA and protein synthesis continue uninterrupted but at higher rates. Electron microscopic observations indicate that more of the macronuclear chromatin is transcribed at the elevated temperature. This interpretation is supported by hybridization experiments which show that the percentage of the macronuclear genome transcribed into poly(A)⁺ RNA is 24°C and 35% at 32°C. Kinetic analysis of cDNA-poly(A)⁺ RNA hybridizations reveals three abundance classes of poly(A)⁺ RNA and indicates that the number of genes expressing low abundance sequences is about 9000 at 24°C and 13000 at 32°C. The intermediately abundant and highly abundant classes are represented by 100–200 and 1–3 different kinds of RNA sequence, respectively. Cross hybridization shows that changes occur throughout the distribution of abundance classes of poly(A)⁺ RNA with increase in temperature.     

Endotoxin-induced behavioural fever in the Madagascar cockroach, Gromphadorhina portentosa

Injections of a suspension of E. coli into the haemocoel of Gromphadorhina portentosa induced dose-dependent behavioural fevers. Cockroaches injected with bacteria and placed in a thermal gradient preferred temperatures significantly elevated over those chosen by control cockroaches. The fever response could also be induced by the injection of bacterial endotoxin, lipopolysaccharide-W. This is the first indication that insects are capable of febrogenesis.     

Carapace color change in Uca pugilator as a response to temperature

Brachyurid species have various coloration patterns that fluctuate among individuals due to behavioral interactions or a changing environment. In the fiddler crab Uca pugilator, the historical notion is that color change is regulated by circadian rhythms. In this study, color patterns of U. pugilator were affected by changes in temperature; crab carapaces become light in warm temperatures and dark in colder temperatures. The response to temperature occurred within 15 min (often within 5 min of exposure to the treatment), suggesting that temperature may play a key role in color change, and it is activated not through a hormonal pathway, but rather a direct response of the chromatophores. Color change occurred differently between day and night for each sex, which implies that endogenous rhythms are not the sole mechanism for color change in U. pugilator. Both sexes became darker in the cold treatment, however there were differences between the sexes with high temperatures. Females did not show significant coloration changes, while males became significantly lighter and more speckled. Results from this study suggest sex-specific constraints in response to temperature that could be associated to morphological body mass to surface area ratios, as males have large cheliped, which may be involved in thermoregulation. Constraints could also be associated to different diel activities that each sex performs or visual cues associated with mating behaviors.