Sundown89 is away for two weeks in Iceland, and has asked me to post this week's Oddity Ark. He wrote it ahead of time- I'm just posting it. On a side note though, I am so proud of Sun' for continuing ImpurestCheese's Impurest's Guide to Animals. These are always interesting, and it's a nice way to cap off a week. Cheers for continuing this, Sun', and safe travels! -Cbishop/FicOPedia. And if you want to request an issue on an amazing animal, fabulous fungus, perplexing plant or awesome paleofauna, don’t hesitate to leave a request in the comments.

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Oddity Ark #97 (#277)

Domain: Eukaryota

Kingdom: Animalia

Phylum: Chordata

Class: Chondricthyes

Order: Carcharhiniformes

Family: Scyllorhinidae

Genus: Poroderma

Species: africanum

Related Species: The pyjama shark is one of two species within the genus Poroderma, the other species being the leopard catshark (Poroderma pantherinum) (1).

Range: The pyjama shark is found in nearshore waters off the coast of South Africa.

IUCN Status: The pyjama shark is currently listed as ‘Least Concern’ on the International Union for Conservation of Nature (IUCN).

Settle in, its time to blog about sharks…

The pyjama shark is a small shark that reaches a maximum length of 1.1m and a weight of 7kg. As the name suggests, the pyjama shark has stripes on its back and flanks that range from the tip of the nose to the upper lobe of its tail. Pyjama sharks have two dorsal fins positioned further towards the back of the animal and an elongated upper lobe of the caudal fin. The pyjama sharks have a pair of short barbels on its snout that are used to detect chemical cues within the water current and are used in tandem with vibrations picked up by the lateral line and electroreception to navigate through its habitat.

Pyjama sharks are slow swimmers and primarily nocturnal predators, feeding on a range of smaller fish, crustaceans, and molluscs. The shark does alter its hunting behaviour during the chokka squid (Loligo reynaudii) spawning season, hunting during the day, hiding within squid egg masses bursting out to snatch female squid as they descend to deposit their eggs (2). The pyjama shark is predated upon by larger shark species such as the broadnose sevengill shark (Notorynchus cepedianus) (3) and copper sharks (). When threatened and away from a hiding point, the pyjama shark coils up covering its head with its tail.

Pyjama sharks mate throughout the year, with the male delivering bites to the female until he can anchor himself in a position where he can insert his claspers and fertilize her eggs. Female pyjama sharks lay a rectangular 10cm long egg on the sea floor, which is tethered to a rock or strand of kelp by the long tendrils on the four corners of the egg case. The egg hatches six months after being laid, with a single 15cm long pup produced (4). Pyjama sharks reach sexual maturity upon reaching a certain length, with males mature at a length of 70cm or longer, and females mature at a length of 80cm or longer.

Five to Save #20: Sharks

Typically, as animals tethered to the upper trophic levels of a food web, sharks are at risk from changes in their habitats. The removal of animals within the upper trophic levels causes knock off effects on the rest of the food web, causing an influx of mesopredators, decimation of herbivores within the lower trophic levels, and an overall depletion of biodiversity. It is imperative for the health of ocean biospheres to protect the predators that help maintain the lower trophic levels of their environment.

Basking Shark (Cetorhinus maximus) – Endangered

Threats: Shipping – The second largest extant fish species, the basking shark typically cruises at the surface and is largely unaware of shipping around it. Because of this, the species is at risk from boat strikes from both commercial and recreational shipping, with frequent fatal strikes occurring within British waters in particular.

Caribbean Reef Shark (Carcharhinus perezi) – Endangered

Threats: Invasive Species – The Caribbean reef shark is subject to a range of threats such as overfishing, reef bleaching and mining, but one of the most unusual threats is the introduction of red lionfish (Pterois volitans) to the Caribbean Sea (5). Lionfish are venomous, and have no natural predators within their introduced range, causing a boom in the population and a depletion in the lower trophic levels and outcompete the mesopredators reef sharks feed upon.

Grey Reef Shark (Carcharhinus amblyrhynchos) – Endangered

Threats: Aquaculture – One of the most common aquarium sharks, the grey reef shark is often wild caught, sometimes illegally. It is speculated that at the current rate of live capture (as well as other factors), that the population will be 0.1% of the pre-exploitation population within the next 20 years (6).

Northern River Shark (Glyphis garricki) – Vulnerable

Threats: Dams – One of the few sharks that can moves from saltwater to freshwater habitats, the northern river shark is subject to a wide range of threats. Modifications in river courses have an impact on the shark’s ability to move between saltwater and freshwater, potentially trapping it in prey scarce waters, or those impacted by runoff from agriculture, logging and mining.

Tope (Galeorhinus galeus) – Critically Endangered

Threats: Over Harvesting – This species has a long history of being overfished, both purposely and by accident. When released when accidentally caught mortality as the shark travels back to its preferred depth can be as high as 70%. Tope has the highest percentage of vitamin A in its liver and is the most commonly hunted fish for use in fish oil tablets (7).

References

1. www.arkive.com

2. Smale M.J.; Sauer, W.H.H. & Hanlon, R.T. (1995). "Attempted ambush predation on spawning squids Loligo vulgaris reynaudii by benthic pyjama sharks, Poroderma africanum off South Africa". Journal of the Marine Biological Association of the United Kingdom. 75 (3): 739–742.

3. Ebert, D.A. (December 1991). "Diet of the seven gill shark Notorynchus cepedianus in the temperate coastal waters of southern Africa". South African Journal of Marine Science. 11 (1): 565–572

4. Pollom, R.; Gledhill, K.; Da Silva, C.; McCord, M.E.; Winker, H. (2020). "Poroderma africanum". IUCN Red List of Threatened Species. 2020

5. Benkwitt, C.E. (2015) Non-linear effects of invasive lionfish density on native coral-reef fish communities. Biol Invasions 17, 1383–1395

6. Robbins, W.D.; Hisano, M.; Connolly, S.R. & Choat, J.H. (2006). "Ongoing collapse of coral reef shark populations". Current Biology. 16 (23): 2314–2319

7. Fish Bulletin No. 64. The Biology of the Soupfin Galeorhinus zyopterus and Biochemical Studies of the Liver". Repositories.cdlib.org.

Picture Credits

1. IMG_2845-1024x768.jpg (1024×768) (saveourseas.com)

2. OIP.tPfj4wNEA6luiLHIW-5YHwAAAA (474×428) (bing.com)

3. Pyjama-Sharks-Credit-Jean-Tresfon-1.jpg (1200×798) (fishingindustrynewssa.com)

4. basking-sharks-have-family-feeding-frenzies-at-known-eating-spots-study-finds-136442958511202601-200203143037.jpg (4224×2369) (bt.com)

5. reefshark27.jpg (1200×895) (reefguide.org)

Next week we have @arctika subbing in for ‘they who are absent’ with a strangely charismatic bird (that also stinks). And if you want to see more amazing animals and plants, please check out the Oddity Arkive or past issues. And if you want even more animals, please check out dearly departed Impurest Cheese’s Guide to Animals which can be found here, or on the blog of @ficopedia (be careful he’s having a nap at the moment).

If you still have a yearning for learning, please check out the master list of Mr Monster’s Martial Arts Journey.