Diabetogenic effects of streptozotocin on endocrine pancreatic islets, adrenal and carbohydrate profiles in turtles, Lissemys punctata punctata (Bonnoterre) (Reptilia: Chelonia)
H. P. Sarkar, Supriti Sarkar, B. R. Maiti
Italian Journal of Zoology
Vol. 80, Iss. 1, 2013
Diabetogenic effect of streptozotocin was not adequately studied in chelonians. This topic was investigated in the current article. Objective of the current study was to investigate the role of streptozotocin on B- and non B-cells of the endocrine pancreas, adrenal and carbohydrate profiles in soft-shelled turtles. A single intramuscular injection of streptozotocin at a dose of 200 mg/kg body wt once, after 7 days caused increase of necrotic B-cell population followed by ultrastructural degeneration. Insulin immunoreactivity of B-cells (insulin-IR B cells) was reduced with a fall in serum insulin level. It also caused necrosis of A-, D- and PP-cells with decrease of their cell size and nuclear size, and ultrastructural degenerations. Glucagon-immunoreactivity of A-cells (glucagon-IR-A-cell) was not altered. Adrenal corticosterone and norepinephrine levels were increased with decrease of epinephrine level. Serum glucose level was elevated with a fall in liver glycogen level. But muscle glycogen level was elevated with a fall in blood lactate level. These changes were no longer observed after 14 days of single dose of SZ treatment. Insulin level was elevated with a fall in corticosterone and epinephrine levels. Serum glucose, liver and muscle glycogen, and blood lactate levels were reversely altered in 14 days of SZ treatment to those of 7 days of treatment. The findings suggest that streptozotocin (SZ) initially causes diabetes with disturbance in adrenal hormone production and carbohydrate metabolism after 7 days treatment and that, the diabetogenic effects are subsided subsequently after 14 days of SZ treatment in turtles.
Ferreira, I. M., Kasuya, T., Marsh, H. and Best, P. B. (2013), False killer whales (Pseudorca crassidens) from Japan and South Africa: Differences in growth and reproduction. Marine Mammal Science. doi: 10.1111/mms.12021
Age and reproductive information for 65 false killer whales stranded in South Africa in 1981 are compared with similar material from 156 animals examined from drive fisheries in Japan in 1979 and 1980. Sizes at birth, sexual maturation, and physical maturity all indicated that both sexes were 10%–20% larger in Japan than South Africa. Females reached sexual maturation at similar ages (8–10.5 yr) in both populations, and although sample sizes were too small to establish male ages at puberty precisely the ranges in Japan (10.5–18.5 yr) and South Africa (5.25–17.5 yr) were not inconsistent. The initial ovulation rate for females from South Africa was 65% lower (and the apparent pregnancy rate 82% lower) than those from Japan and there were fewer animals ≤2 yr old within the school, but the magnitude of these differences suggests that the stranded school’s reproductive performance was probably impaired. Collectively these comparisons and the literature indicate substantive size differences between false killer whales in different populations, although the patterns of growth appear similar. Firm conclusions about any geographical differences in reproduction require additional data.
Blair, D., McMahon, A., McDonald, B., Tikel, D., Waycott, M. and Marsh, H. (2013), Pleistocene sea level fluctuations and the phylogeography of the dugong in Australian waters. Marine Mammal Science. doi: 10.1111/mms.12022
We investigated phylogeography, demography, and population connectivity of the dugong (Dugong dugon) in Australian waters using mitochondrial control region DNA sequences from 177 Australian dugongs and 11 from elsewhere. The dugong is widespread in shallow Indo-West Pacific waters suitable for growth of its main food, seagrass. We hypothesized that the loss of habitat and creation of a land barrier (the Torres Strait landbridge) during low sea level stands associated with Pleistocene glacial cycles have left a persisting genetic signature in the dugong. The landbridge was most recently flooded about 7,000 yr ago. Individual dugongs are capable of traveling long distances, suggesting an alternative hypothesis that there might now be little genetic differentiation across the dugong’s Australian range. We demonstrated that Australian dugongs fall into two distinct maternal lineages and exhibit a phylogeographic pattern reflecting Pleistocene sea-level fluctuations. Within each lineage, genetic structure exists, albeit at large spatial scales. We suggest that these lineages diverged following the last emergence of the Torres Strait landbridge (ca. 115 kya) and remained geographically separated until after 7 kya when passage through Torres Strait again became possible for marine animals. Evidence for population growth in the widespread lineage, especially after the last glacial maximum, was detected.
Stable isotope turnover and variability in tail hairs of captive and free-ranging African elephants (Loxodonta africana) reveal dietary niche differences within populations
Jacqueline Codron, Kevin Kirkman, Kevin J. Duffy, Matt Sponheimer, Julia A. Lee-Thorp, Andre Ganswindt, Marcus Clauss, Daryl Codron
Canadian Journal of Zoology, Published on the web 17 January 2013, 10.1139/cjz-2012-0155
Many herbivore species expand their dietary niche breadths by switching from browse-rich diets in dry seasons to grass-rich diets in rainy seasons, in response to phenological changes in plant availability and quality. We analyzed stable isotope series along tail hairs of captive and free-ranging African elephant (Loxodonta africana (Blumenbach, 1797)) to compare patterns of seasonal dietary variability across individuals. Results from elephants translocated from the wild into captivity, where their diets are semicontrolled, revealed tail hair growth rates of 0.34 mm/day, on average, and relatively rapid isotope turnover through the transition from wild into captivity. Sampling hairs at 10 mm increments thus archives dietary chronologies at a resolution suitable for tracking diet switches at seasonal, and even subseasonal, scales. Hairs of free-ranging elephants showed extensive carbon isotopic variability within individuals, consistent with seasonal switches between C3-browsing and C4-grazing. Similarly extensive, but asynchronous, shifts in nitrogen isotope ratios were also observed, suggesting an influence of factors other than seasonality. Across individuals, switching patterns differed across habitats, and across age classes, with older, larger animals including increasing amounts of C3 browse into their diets. These results demonstrate how stable isotope approaches characterize complex patterns of resource use in wildlife populations.
Continental phylogeography of an ecologically and morphologically diverse neotropical songbird, zonotrichia capensis
Lougheed SC, Campagna L, Dávila JA, Tubaro PL, Lijtmaer DA, Handford P
BMC Evolutionary Biology 2013
The Neotropics are exceptionally diverse, containing roughly one third of all extant bird species on Earth. This remarkable species richness is thought to be a consequence of processes associated with both Andean orogenesis throughout the Tertiary, and climatic fluctuations during the Quaternary. Phylogeographic studies allow insights into how such events might have influenced evolutionary trajectories of species and ultimately contribute to a better understanding of speciation. Studies on continentally distributed species are of particular interest because different populations of such taxa may show genetic signatures of events that impacted the continent-wide biota. Here we evaluate the genealogical history of one of the world’s most broadly-distributed and polytypic passerines, the rufous-collared sparrow (Zonotrichia capensis).
We obtained control region DNA sequences from 92 Zonotrichia capensis individuals sampled across the species‘ range (Central and South America). Six additional molecular markers, both nuclear and mitochondrial, were sequenced for a subset of individuals with divergent control region haplotypes. Median-joining network analysis, and Bayesian and maximum parsimony phylogenetic analyses all recovered three lineages: one spanning Middle America, the Dominican Republic, and northwestern South America; one encompassing the Dominican Republic, Roraima (Venezuela) and La Paz (Bolivia) south to Tierra del Fuego, Argentina; and a third, including eastern Argentina and Brazil. Phylogenetic analyses suggest that the Middle American/northwestern South American clade is sister to the remaining two. Bayesian and maximum likelihood coalescent simulations used to study lineage demographic history, diversification times, migration rates and population expansion together suggested that diversification of the three lineages occurred rapidly during the Pleistocene, with negligible gene flow, leaving genetic signatures of population expansions.
The Pleistocene history of the rufous-collared sparrow involved extensive range expansion from a probable Central American origin. Its remarkable morphological and behavioral diversity probably represents recent responses to local conditions overlying deeper patterns of lineage diversity, which are themselves produced by isolation and the history of colonization of South America.
Evolution of bone compactness in extant and extinct moles (Talpidae): exploring humeral microstructure in small fossorial mammals
Meier PS, Bickelmann C, Scheyer TM, Koyabu D, Sánchez-Villagra MR
BMC Evolutionary Biology 2013
Talpids include forms with different degree of fossoriality, with major specializations in the humerus in the case of the fully fossorial moles. We studied the humeral microanatomy of eleven extant and eight extinct talpid taxa of different lifestyles and of two non-fossorial outgroups and examined the effects of size and phylogeny. We tested the hypothesis that bone microanatomy is different in highly derived humeri of fossorial taxa than in terrestrial and semi-aquatic ones, likely due to special mechanical strains to which they are exposed to during digging. This study is the first comprehensive examination of histological parameters in an ecologically diverse and small-sized mammalian clade.
No pattern of global bone compactness was found in the humeri of talpids that could be related to biomechanical specialization, phylogeny or size. The transition zone from the medullary cavity to the cortical compacta was larger and the ellipse ratio smaller in fossorial talpids than in non-fossorial talpids. No differences were detected between the two distantly related fossorial clades, Talpini and Scalopini.
At this small size, the overall morphology of the humerus plays a predominant role in absorbing the load, and microanatomical features such as an increase in bone compactness are less important, perhaps due to insufficient gravitational effects. The ellipse ratio of bone compactness shows relatively high intraspecific variation, and therefore predictions from this ratio based on single specimens are invalid.
Ecosystems, March 2013, Volume 16, Issue 2, pp 269-283
Whole-Stream Metabolism Responds to Spawning Pacific Salmon in Their Native and Introduced Ranges
Peter S. Levi, Jennifer L. Tank, Janine Rüegg, David J. Janetski, Scott D. Tiegs, Dominic T. Chaloner, Gary A. Lamberti
Pacific salmon (Oncorhynchus spp.) perform important ecological roles in stream ecosystems by provisioning nutrients as resource subsidies and modifying their physical habitat as ecosystem engineers. These contrasting roles result in concurrent nutrient enrichment and benthic disturbance, where local environmental characteristics potentially determine which effect predominates. Whole-stream metabolism quantifies the functional response to salmon and may identify patterns in enrichment and disturbance not apparent from structural measurements alone. We measured ecosystem respiration (ER) and gross primary production (GPP), along with chemical and physical characteristics, in seven Southeast Alaska streams and two Michigan streams, before and during the salmon run. These streams in the native and introduced ranges of salmon differed in environmental characteristics, from geomorphology at the reach scale to climate at the biome scale. Salmon consistently increased ER across streams and biomes, from an average (±SE) of 1.92 ± 0.23 g O2 m−2 d−1 before salmon to 6.30 ± 1.08 g O2 m−2 d−1 during the run. In the cobble-bottom streams of Southeast Alaska, GPP doubled from 0.29 ± 0.05 g O2 m−2 d−1 before salmon to 0.66 ± 0.16 g O2 m−2 d−1 during the run. In contrast, GPP responded inconsistently to salmon in the sand-bottom Michigan streams, increasing in one and decreasing in the other. Patterns in ER and GPP among streams and time periods were predicted by stream water nutrients (for example, ammonium, soluble reactive phosphorus) rather than by physical characteristics (for example, light, sediment size, and so on). This study demonstrates that salmon can periodically override physical controls on ER and GPP and enhance whole-stream metabolism via their dual ecological roles as both resource subsidies and ecosystem engineers.
Biological Invasions, March 2013
Multi-event models reveal the absence of interaction between an invasive frog and a native endangered amphibian
Hugo Cayuela, Aurélien Besnard, Pierre Joly
Among the multiple factors involved in the decline of amphibians, competition with alien species remains understudied. In Western Europe, non-native marsh frogs (Pelophylax ridibundus and other sister species) have been widely imported for gastronomic purposes and have then often escaped from captivity. Apart from closely related species, the impact of the subsequent colonization of non-native species on native amphibians is still unknown. In this study, we analysed the response of a threatened species, the yellow-bellied toad (Bombina variegata), faced with the presence of alien frogs in mountain rivers in France. We studied the co-occurrence pattern of the native toad and the alien frog, while taking into account co-dependence of the detection rates in both species. We tested three main scenarios to explain a non-random pond occurrence for each species and to establish their respective habitat preferenda: (1) a pond-area-dependent scenario, predicting different responses from each species for a given pond size, (2) a fish-dependent scenario, predicting different responses from each species given the presence of fish in ponds, and (3) a floodplain-width-dependent scenario, predicting different responses from each species given the geomorphological characteristics of the floodplain. Taking into account site-specific covariates, we concluded that introduced frogs do not currently have an impact on the native population of the yellow-bellied toad.
Population Ecology, February 2013
A simulation model of the Devils Hole pupfish population using monthly length-frequency distributions
Maria Christina Dzul, Stephen James Dinsmore, Michael Carl Quist, Daniel Bailey Gaines, Kevin Patrick Wilson, Michael Roy Bower, Philip Michael Dixon
The Devils Hole pupfish, Cyprinodon diabolis, is a federally-endangered fish that is endemic to Devils Hole, a discontiguous part of Death Valley National Park in Nye County, Nevada. Due to its status, Devils Hole pupfish monitoring must be non-obtrusive and thereby exclude techniques that require handling fish. Due to a recent decline in pupfish abundance, Devils Hole pupfish managers have expressed a need for a model that describes population dynamics. This population model would be used to identify vulnerable life history stage(s) and inform management actions. We constructed a set of individual-based simulation models designed to explore effects of population processes and evaluate assumptions. We developed a baseline model, whose output best resembled both observed length-frequency data and predicted intra-annual abundance patterns. We then ran simulations with 5 % increases in egg-larval, juvenile, and adult survival rates to better understand Devils Hole pupfish life history, thereby helping identify vulnerable life history stages that should become the target of management actions. Simulation models with temporally constant adult, juvenile, and egg-larval survival rates were able to reproduce observed length-frequency distributions and predicted intra-annual population patterns. In particular, models with monthly adult and juvenile survival rates of 80 % and an egg-larval survival rate of 4.7 % replicated patterns in observed data. Population growth was most affected by 5 % increases in egg-larval survival, whereas adult and juvenile survival rates had similar but lesser effects on population growth. Outputs from the model were used to assess factors suspected of influencing Devils Hole pupfish population decline.
Salmon consumption by Kodiak brown bears (Ursus arctos middendorffi) with ecosystem management implications
M.B. Van Daele, C.T. Robbins, B.X. Semmens, E.J. Ward, L.J. Van Daele, W.B. Leacock
Canadian Journal of Zoology, Published on the web 07 February 2013, 10.1139/cjz-2012-0221
The ecological role of large predators in North America continues to spark heated public debate. Although brown bears (Ursus arctos L., 1758) and the salmon (genus Oncorhynchus Suckley, 1861) they feed on have declined in many areas, the Kodiak archipelago is famous for large brown bears and abundant salmon. Salmon have generally been managed for maximum sustained yield in a fisheries sense, but those levels may be well below what is necessary for maximum ecosystem productivity. Consequently, we used stable isotopes and mercury accumulated in hair to estimate intake of salmon by Kodiak brown bears (Ursus arctos middendorffi Merriam, 1896). Salmon intake increased from subadult males (592 ± 325 kg·bear−1·year−1) to adult males (2788 ± 1929 kg·bear−1·year−1) and from subadult females (566 ± 360 kg·bear−1·year−1) to adult females (1364 ± 1261 kg·bear−1·year−1). Intake within each group increased 62% ± 23% as salmon escapement increased from 1 500 to 14 000 kg·bear−1·year−1. The estimated population of 2300 subadult and adult bears consumed 3.77 ± 0.16 million kg of salmon annually, a mass equal to 6% of the combined escapement and commercial harvest (57.6 million kg). Although bears consume a small portion of the total mass of adult salmon, perpetuation of dense populations of large bears requires ecosystem-based management of the meat resources and environments that produce such bears.