The effect of hydration state and energy balance on innate immunity of a desert reptile

INTRODUCTION: Immune function is a vital physiological process that is often suppressed during times of resource scarcity due to investments in other physiological systems. While energy is the typical currency that has been examined in such trade-offs, limitations of other resources may similarly lead to trade-offs that affect immune function. Specifically, water is a critical resource with profound implications for organismal ecology, yet its availability can fluctuate at local, regional, and even global levels. Despite this, the effect of osmotic state on immune function has received little attention. RESULTS: Using agglutination and lysis assays as measures of an organism’s plasma concentration of natural antibodies and capacity for foreign cell destruction, respectively, we tested the independent effects of osmotic state, digestive state, and energy balance on innate immune function in free-ranging and laboratory populations of the Gila monster, Heloderma suspectum. This desert-dwelling lizard experiences dehydration and energy resource fluctuations on a seasonal basis. Dehydration was expected to decrease innate immune function, yet we found that dehydration increased lysis and agglutination abilities in both lab and field studies, a relationship that was not simply an effect of an increased concentration of immune molecules. Laboratory-based differences in digestive state were not associated with lysis or agglutination metrics, although in our field population, a loss of fat stores was correlated with an increase in lysis. CONCLUSIONS: Depending on the life history of an organism, osmotic state may have a greater influence on immune function than energy availability. Thus, consideration of osmotic state as a factor influencing immune function will likely improve our understanding of ecoimmunology and the disease dynamics of a wide range of species

Major shifts in the evolution of somitogenesis: The reptile Anolis carolinensis represents a fourth type of segmentation clock among vertebrates

La prueba de Comprensión lectora ha sido construida en relación con lo que señala el Diseño Curricular Nacional (DCN) y la Propuesta Pedagógica EIB. En la ECE 2012, la prueba presenta los siguientes textos: notas, anécdotas, instructivos, cuentos, noticias y descripciones

The effect of carotenoid supplementation on immune system development in juvenile male veiled chameleons (Chamaeleo calyptratus)

Abstract Introduction Nutrient availability, assimilation, and allocation can have important and lasting effects on the immune system development of growing animals. Though carotenoid pigments have immunostimulatory properties in many animals, relatively little is known regarding how they influence the immune system during development. Moreover, studies linking carotenoids to health at any life stage have largely been restricted to birds and mammals. We investigated the effects of carotenoid supplementation on multiple aspects of immunity in juvenile veiled chameleons (Chamaeleo calyptratus). We supplemented half of the chameleons with lutein (a xanthophyll carotenoid) for 14 weeks during development and serially measured multiple aspects of immune function, including: agglutination and lysis performance of plasma, wound healing, and plasma nitric oxide concentrations before and after wounding. Results Though lutein supplementation effectively elevated circulating carotenoid concentrations throughout the developmental period, we found no evidence that carotenoid repletion enhanced immune function at any point. However, agglutination and lysis scores increased, while baseline nitric oxide levels decreased, as chameleons aged. Conclusions Taken together, our results indicate that body mass and age, but not carotenoid access, may play an important role in immune performance of growing chameleons. Hence, studying well-understood physiological processes in novel taxa can provide new perspectives on alternative physiological processes and nutrient function

Fractionated 131I anti-CEA radioimmunotherapy: effects on xenograft tumour growth and haematological toxicity in mice

Dose fractionation has been proposed as a method to improve the therapeutic ratio of radioimmunotherapy (RIT). This study compared a single administration of 7.4 MBq 131I-anti-CEA antibody given on day 1 with the same total activity given as fractionated treatment: 3.7 MBq (days 1 and 3), 2.4 MBq (days 1, 3, and 5) or 1.8 MBq (days 1, 3, 5, and 8). Studies in nude mice, bearing the human colorectal xenograft LS174T, showed that increasing the fractionation significantly reduced the efficacy of therapy. Fractionation was associated with a decrease in systemic toxicity as assessed by weight, but did not lead to any significant decrease in acute haematological toxicity. Similarly, no significant decrease in marrow toxicity, as assessed by colony-forming unit assays for granulocytes and macrophages (CFUgm), was seen. However, there was a significant depression of CFUgm counts when all treated animals were compared with untreated controls, suggesting that treatment did suppress marrow function. In conclusion, in this tumour model system, fractionated RIT causes less systemic toxicity, but is also less effective at treating tumours

Sexual Size Dimorphism and Growth Plasticity in Snakes: an Experiment on the Western Diamond‐Backed Rattlesnake (\u3cem\u3eCrotalus atrox\u3c/em\u3e)

We conducted an experiment to examine the effects of sex and food intake on growth, mass gain, and attainment of sexual maturity in Western Diamond‐backed Rattlesnakes (Crotalus atrox). We also measured testosterone levels to determine whether testosterone might be involved in the male‐biased sexual size dimorphism observed in this species. We collected neonate rattlesnakes and raised them in the laboratory for 2 years on either a high‐intake diet (fed one mouse per week) or a low‐intake diet (fed one mouse every 3 weeks). High‐intake snakes grew and gained mass more rapidly than low‐intake snakes, but males did not grow or gain mass more rapidly than females in either treatment group. High‐intake snakes attained reproductive maturity earlier than low‐intake snakes, indicating that size, not age, is the critical determinant of reproductive maturity. Males had higher levels of testosterone than females but did not grow more quickly, suggesting that testosterone may not affect growth in this species and may therefore not be the proximate determinant of sexual size dimorphism

Seasonal Steroid Hormone Levels and Their Relation to Reproduction in the Western Diamond-Backed Rattlesnake, \u3cem\u3eCrotalus atrox \u3c/em\u3e (Serpentes: Viperidae)

We report seasonal variation in steroid hormone levels in blood samples from free-ranging Western Diamond-backed Rattlesnakes (Crotalus atrox), and the relationship between these hormones and events in the reproductive cycle. At a field site in the Sonoran Desert of south-central Arizona, we collected monthly blood samples over the course of two active seasons from 17 radiotelemetered females, and over three active seasons from 103 randomly encountered males. We used radioimmunoassay to measure plasma levels of 17β-estradiol, progesterone, corticosterone, and testosterone in samples from females, and corticosterone and testosterone in samples from males. Non-reproductive females have consistently low levels of circulating 17β-estradiol, progesterone, and testosterone throughout the year. In reproductive females, 17β-estradiol levels increase dramatically and testosterone levels increase modestly during vitellogenesis in April and May, while progesterone levels increase dramatically at ovulation in June and then steadily decline until parturition in August. Corticosterone levels appear relatively constant in non-reproductive females, whereas reproductive females show increased levels at the end of gestation. Plasma testosterone levels in males are low in early summer and are elevated during spring and late summer, corresponding to the two mating periods of C. atrox. Plasma corticosterone levels in males did not vary seasonally and were not related to testosterone levels

Data from: Evidence for atypical nest overwintering by hatchling lizards, Heloderma suspectum

The timing of reproductive events (e.g., oviposition and hatching) to coincide with favorable seasonal conditions is critical for successful reproduction. However, developmental time may not match the duration between the optimal time for oviposition and the optimal time for hatchling survival. Thus, strategies that alter the time between oviposition and hatchling emergence can be highly advantageous. Arrested development and the resulting extension of the duration between oviposition and hatching has been widely documented across oviparous amniotes, but nest overwintering by hatchlings has only been documented in aquatic chelonians that live where winters are quite cold. Herein, we present a compilation of evidence regarding reproductive phenology by hatchling Gila monsters (Heloderma suspectum), a lizard inhabiting the Sonoran Desert of North America. Our data demonstrate that (1) Gila monster hatchlings from eggs oviposited in July do not emerge from their nests until late spring or summer of the following year, yet (2) Gila monster eggs artificially incubated at field-relevant temperatures hatch in 4-5 months. Furthermore, we describe a fortuitous excavation of a hatching Gila monster nest in late October, which coincides with the artificial incubation results. Together, these results provide strong support for the existence of overwintering in the nest by a lizard, and suggest that this reproductive strategy should be explored in a broader array of taxa