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The Epaulette shark (Hemiscyllium ocellatum) is a small benthic egg-laying elasmobranch. It is native to the Great Barrier Reef above Australia and is notable for foraging in tidal pools, withstanding harsh temperatures, and long periods of hypoxia and anoxia [1-3]. Sea surface temperatures in the Great Barrier Reef have already warmed by about 1 degree Celsius since 1910 [3].

Epaulette shark individuals were reared under temperatures 4℃ higher than average known rearing temperatures [4]. Measures of skeletal muscle development, oxidative stress, and protein degradation biomarkers were used to understand the potential effects of chronically elevated incubation temperatures on individual shark metabolic demand and viability.

1. Randall et al., 1990. Crawford House, Bathurst, Australia.

2. Heupel and Bennett 1998. Mar. Freshw. Res. 49, 753–756.

3. Heinrich et al., 2016.  ICES Journal of Marine Science, Vol.73, 3, 633–640.

4. Wheeler et al., 2021. Scientific Reports, 11,454.

GSL+WGA+DAPI Skates 10_17_19.xlef_B42E_1

Elevated temperature effects on Little Skate pectoral fin structure and glycosylation patterns

The Little Skate (Leucoraja erinacea) is another benthic elasmobranch species ranging in the western Atlantic from Cape Hatteras to southeastern Canada [1]. The little skate is a non-migratory species, but the waters of the northwestern Atlantic exhibit seasonal temperature shifts, meaning these populations experience temperature variability in their current life history. The Gulf of Maine is the specific study location of Little Skates for this chapter. All seasons in the Gulf of Maine have shown shifts in length and average temperatures, with summer conditions extending by two days per year since 1982, spring conditions occurring two weeks earlier since 2006, and fall conditions occurring later since 2005 [2-4].

Little Skate individuals were reared under temperatures 5℃ higher than ambient rearing temperatures. Pectoral fins were analyzed to detect changes in fin morphology and cellular glycosylation to assess adaptive changes in structure and cell communication resulting from changing energetic demands on individuals. 

1. Frisk and Miller. (2006). Canada Journal of Fisheries and Aquatic Sciences. 63, 5, 1078-1091

2. Friedland et al. (2015). Cont. Shelf Res. 102,  47-61

3. Staudinger et al. (2019).  Fisheries Oceanography. 28, 5, 532-566

4.  Thomas et al. (2017). Elementa- Science of the Anthrop. Vol. 5

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The Port Jackson Shark (Heterodontus portusjacksoni) is a small benthic shark species located along the southern coastline of Australia. This shark is unique in that it has both resident and migratory populations along the coast of Australia, which can migrate up to 700 km at a time [1]. Southern Australian waters are warming at different rates along the coastline, with the southeastern coast warming faster and more invariably due to the warming of the East Australia current, while the mid-southern coastline near Adelaide is warming slowly and more stably [2,3]. Sharks for this study were taken specifically from Adelaide South Australia and Jervis Bay, NSW located on the southeastern coastline.

Port Jackson shark individuals from Adelaide, South Australia, and Jervis Bay, New South Wales, were reared at their respective ambient and projected end-of-century (EOC) temperatures from eggs to early juvenile stages. Skeletal muscle was analyzed to assess adaptive changes in morphology that provide insight into how changes in metabolic and energetic demand influence structural changes in metabolic machinery.  

1. Powter, D. M., and Gladstone, W. (2008). Marine and Freshwater Research 59, 444–455.

2. Gervais et al. (2021). Global Change Biol. 27, 14, 3200-3217.

3. Suthers et al. (2011). Deep Sea Research. 58, 5, 538-546.


Comparative effects of hypoxia on proteolytic processes in two Fundulus species

Hypoxia (oxygen deficiency) is a commonly studied stressor in the biomedical field related to pathological conditions, yet hypoxia is also an environmental stressor. Many marine organisms employ behavioral or physiological strategies to combat changing hypoxia levels. Yet, the concern for the increased frequency of acute hypoxia is increasing due to potential climate change effects on ocean chemistry. Hypoxia can induce protein degradation to protect cells from apoptosis (cell death) and has yet to be studied in the context of potential physiological mechanisms employed by known hypoxia-tolerant marine species. By studying a known hypoxia-tolerant marine species, Fundulus heteroclitus, and a lesser-known yet closely related species, Fundulus majalis, we might elucidate further the extent to which hypoxia-induced protein degradation is used and the dependence on these mechanisms for contributing to hypoxia tolerance.

Photo Credit: NCFishes

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