Journal of experimental zoology. Part A, Ecological genetics and physiology最新文献

Freshwater mussels have decreased dramatically in Iberia over the last decades. These animals are responsible for important ecosystem services such as recycling nutrients and improving water clarity. Under this view a better knowledge on the biological features of these animals is extremely important for future conservation and management actions. In this study the reproductive and gametogenic cycle of Anodonta anatina were studied during 2 years in one population as well as the sex ratio and hermaphroditism in six distinct populations, using standard histology. Gametogenesis was continuous in both sexes and germinal epithelium in early stages of development. Gametes were present throughout the reproductive cycle. Oogenesis and spermatogenesis occurred mainly between January and May. Larvae brooding occurred between September and March and main glochidia discharge occurred over a short period (2-3 weeks) in March. For the sex-ratio and hermaphroditism assessments a variable number of individuals were collected from several populations from lakes and rivers. Previous studies described A. anatina as mainly dioecious with only a few populations presenting occasional hermaphroditism. However, the present study indicates that A. anatina sexual behavior is influenced by environmental conditions, being mainly dioecious in rivers with increased hermaphroditism in standing waters. Although self-fertilization was not confirmed, additional studies with molecular characterization of larvae using fast evolving markers should be used in future studies to enlighten this process. Overall, this study indicates that for more efficient conservation actions and management plans, freshwater mussel reproductive biology should be studied at the population level mainly in the subfamily Anodontinae.

Bony fish primarily excrete ammonia as adults however the persistence of urea cycle genes may reflect a beneficial role for urea production during embryonic stages in protecting the embryo from toxic effects of ammonia produced from a highly nitrogenous yolk. This study aimed to examine the dynamic scope for changes in rates of urea synthesis and excretion in one such species (zebrafish, Danio rerio) by manipulating the intrinsic developmental rate (by alteration of light:dark cycles), as well as by direct chemical manipulation via ammonia injection (to potentially activate urea production) and nicotinamide exposure (to potentially inhibit urea production). Continuous dark exposure delayed development in embryos as evidenced by delayed appearance of hallmark anatomical features (heartbeat, eye pigmentation, body pigmentation, lateral line, fin buds) at 30 and 48 hr post-fertilization, as well by a lower hatching rate compared to embryos reared in continuous light. Both ammonia and urea excretion were similarly effected and were generally higher in embryos continuously exposed to light. Ammonia injection resulted in significant increases (up to fourfold) of urea N excretion and no changes to ammonia excretion rates along with modest increases in yolk ammonia content during 2-6 hr post-injection. Nicotinamide (an inhibitor of urea synthesis in mammals) reduced the ammonia-induced increase in urea excretion and led to retention of ammonia in the yolk and body of the embryo. Our results indicate that there is a relatively rapid and large scope for increases in urea production/excretion rates in developing embryos. Potential mechanisms for these increases are discussed.

Environmental conditions during early development can profoundly influence an individual's phenotype. Development requires simultaneous maturation and orchestration of multiple physiological systems creating the potential for interaction among key systems and requiring substantial resources. We investigated the influence of thermoregulation on immunocompetence in Wood Duck ducklings (Aix sponsa). At both 1 and 2 days post hatch (dph) we evaluated ducklings' abilities to thermoregulate during a thermal challenge at one of four temperatures (36 [thermoneutral controls], 20, 10, or 5°C). At 3 dph, ducklings received a superficial wound, which was monitored until full recovery to quantify wound healing ability, an ecologically relevant, integrative measure of immune function. We demonstrated that duckling body temperature decreased with increasing thermal challenge severity, thermoregulatory ability increased with age, and thermoregulation had temperature-dependent effects on the immune system. Specifically, a more severe thermal challenge (5°C) resulted in decreased immune performance when compared to a mild challenge (20°C). We conclude that early thermoregulatory experiences are influential in shaping immune responses early in development. Furthermore, our results emphasize that future studies of environmental stressors need to consider multiple physiological endpoints since interaction among systems can result in competing physiological demands.

Almost the whole life cycle of the grass puffer (Takifugu niphobles) occurs in seawater (SW), but it is also sometimes found in fresh water (FW) rivers. This study aims to evaluate the effects of FW exposure on the stress, osmoregulatory, and physiological responses of the grass puffer. The grass puffers were captured from a local wetland and acclimated to SW (35‰) or FW in the laboratory. In the stress responses, plasma glucose concentrations and the abundances of hepatic and branchial heat shock proteins were higher in the FW group than in the SW group. FW acclimation led to a significant increase in the protein abundance and the specific activity of branchial Na(+)/K(+)-ATPase (NKA). Immunochemical staining showed that the NKA immunoreactive (NKIR) cells of the FW and SW puffer were distributed mainly in gill filaments. Although the number of NKIR cells was similar in the two groups, the protein levels of proliferating cell nuclear antigen (PCNA) of nuclear fractions were elevated in the gills of the FW puffer. The induction of gill PCNA might contribute to cell proliferation which would maintain the amount of NKIR cells or repair DNA when exposed to FW, an osmotically stressful environment. Hence, activation of stress responses would provide the osmoprotection associated with FW adaptation of the grass puffer. Changes of branchial NKA expression and activity for osmoregulatory adjustment were required for stable blood osmolality and muscle water content. Based on our findings, the grass puffer was suggested to be a euryhaline teleost with SW preference.

Living birds represent the only extant sauropsid group in which pulmonary air sacs pneumatize the postcranial skeleton. Notable in this regard is an extraordinary degree of variability, ranging from species that are completely apneumatic to those characterized by air within the entire postcranial skeleton. Although numerous factors (e.g., body size) have been linked with "relative" pneumaticity, comparative studies examining this system remain sparse. This project sought to (1) characterize whole-body patterns of skeletal pneumaticity in distantly related neognath birds and (2) evaluate putative relationships among relative pneumaticity, body size and locomotor specializations. Pneumaticity profiles were established for 52 species representing 10 higher-level groups. Although comparisons reveal relatively conserved patterns within most lower-level clades, apparent size- and locomotor-thresholds do impart predictable deviations from the clade norm. For example, the largest flying birds (vultures, pelicans) exhibit hyperpneumaticity (i.e., pneumaticity of distal limb segments) relative to smaller members of their respective clades. In contrast, skeletal pneumaticity has been independently lost in multiple lineages of diving specialists (e.g., penguins, auks). The application of pneumaticity profiling to extinct archosaurs reveals similar trends in body size evolution, particularly when examining patterns of pneumaticity in a size-diverse assemblage of pterosaurs (flying "reptiles"). As a fundamental organizing system, skeletal pneumaticity may play a role in relaxing constraints on body size evolution by allowing volumetric increases without concomitant increases in body mass. Not only might this be critical for taxa (birds, pterosaurs) exploiting the energetically costly aerial environment, but could be beneficial for any large-bodied terrestrial vertebrates such as the dinosaurs.