Physiological Impairment as a Result of Bile Accumulation in an Apex Predator, the Tiger Shark (Galeocerdo cuvier Péron & Lesueur, 1822)

Physiological adaptations have evolved to help sharks face rapid periods of feast. Tiger sharks are generalist apex predators that rely on a high-lipid/protein diet. To achieve a satisfactory nutritional condition, proper lipid absorption and hepatic storage are needed. Bile secretion in sharks is low and sporadic but increases during short periods of fasting. The present study describes a physiological impairment caused by bile accumulation in juvenile tiger sharks, possibly due to prolonged fasting. These evidences suggest that, even though sharks have adaptations that prevent them from dying from starvation, alarming physiological alterations might occur. Future studies are needed to assess how such a condition can affect wild populations, as well as possible sublethal consequences that could impact their long-term survival.

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Density of Nocturnal Mammals in a Forest Patch in Bangladesh

10.20944/preprints202008.0014.v1 ◽

2020 ◽

Author(s):

Hassan Al-Razi ◽

Sabit Hasan ◽

Tanvir Ahmed ◽

Sabir Bin Muzaffar

Keyword(s):

Distance Sampling ◽

Apex Predators ◽

Slow Loris ◽

Forest Patch ◽

Term Survival ◽

Wide Range ◽

The Common ◽

Nocturnal Mammals ◽

Severe Disturbance

Tropical forests harbor complex communities that are linked together by biotic relationships. Asian forests in particular have lost many apex predators due to habitat loss. We studied a small forest patch in northeastern Bangladesh, Satchari National Park, to determine density and diversity of nocturnal mammals and evaluate their relationships. Transects were walked from February 2015 to July 2016 and density was estimated using distance sampling. Nine species of mammals (5 arboreal and 4 ground-dwelling) were encountered. Densities of the common palm civets, Paradoxurus hermaphrodites, Bengal slow loris, Nycticebus bengalensis, were the highest (19.48 and 15.03 individuals/km2). Density of small Indian civets, large Indian civets and Indian mongoose were lower (2.31-5.55 individuals/km2). Unexpectedly, a wide range of nocturnal mammals co-existed in this forest patch, in spite of fragmentation and severe disturbance. We did not find any significant association between any of the species studied, although this could be an artifact of low sample size. Conservation in Bangladesh remains a challenge due to high human population density. Thus, strict conservation measures are needed to permit the long-term survival of these species.

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Caspases and apoptosis

Essays in Biochemistry ◽

10.1042/bse0380009 ◽

2002 ◽

Vol 38 ◽

pp. 9-19 ◽

Cited By ~ 121

Author(s):

Guy S Salvesen

Keyword(s):

Cysteine Proteases ◽

Signalling Pathways ◽

Term Survival ◽

Mature Adult ◽

Intracellular Signalling Pathways ◽

Adult Cell ◽

Caspase Family ◽

Cell Fragments ◽

Pro Inflammatory Cytokines

The ability of metazoan cells to undergo programmed cell death is vital to both the precise development and long-term survival of the mature adult. Cell deaths that result from engagement of this programme end in apoptosis, the ordered dismantling of the cell that results in its 'silent' demise, in which packaged cell fragments are removed by phagocytosis. This co-ordinated demise is mediated by members of a family of cysteine proteases known as caspases, whose activation follows characteristic apoptotic stimuli, and whose substrates include many proteins, the limited cleavage of which causes the characteristic morphology of apoptosis. In vertebrates, a subset of caspases has evolved to participate in the activation of pro-inflammatory cytokines, and thus members of the caspase family participate in one of two very distinct intracellular signalling pathways.

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