Author: Bee Smith
Tasselled wobbegongs
Eucrossorhinus dasypogon
Our last Elasmobranch of the Month for 2024 is the tasselled wobbegong. This species proves how ‘weird’ sharks are just as cool and deserving of attention as the more well-known ones and is the ultimate example of how far sharks can diverge from the typical ‘shark-like’ body plan!
Image Credit Andy Murch Sharks and Rays
Key Features & Appearance
The tasselled wobbegong is one of 12 species of wobbegong sharks. Wobbegongs are a group of small sharks with flattened heads and bodies, broad fins, and intricate camouflaging patterns. This body form is perfectly adapted to their lifestyle, where they wait motionless on the seafloor for prey to swim by before ambushing it.
Wobbegongs can rest on the seafloor thanks to their amazing ability to pump water over their gills to obtain oxygen, a process called buccal pumping. In contrast, many other shark species must keep swimming throughout their entire lives in order to pass water over their gills. Wobbegongs belong to the carpet shark group, and many other species within this group can buccal pump, such as nurse sharks and zebra sharks; however, the whale shark (the world’s largest shark species) is also in this group and does not have this ability.
The tasselled wobbegong’s scientific name “Eucrossorhinus dasypogon” means ‘well-fringed nose with a shaggy head’, named after the ‘tassels’ of complex dense branching dermal lobes along the front of its head. This fringing helps to break up the outline of its body which aids its camouflage, and they also have a particularly ornate mottled pattern to help with this. However, these tassels aren’t just to help them hide, these lobes are covered in sensory organs and so also serve the purpose of detecting small movements which helps them find their prey. This fringe makes this species the most specialised member of its group for their stealth and ambush lifestyle!
Image Credit Andy Murch Sharks and Rays
Habitat & Distribution
This species is found throughout the Western Pacific, such as in Eastern Indonesia, New Guinea, and Northern Australia around the Great Barrier Reef. They are found at shallow depths from 40m/113ft and spend their lives around reefs, both on the continental shelf and offshore. They are nocturnal, spending daytime resting in caves and ledges on reefs and then venturing out to feed at night.
Diet
As mentioned, they are nocturnal predators that use an ambush technique. In addition to just waiting for prey to pass by, they are known to wave their caudal fin whilst keeping the rest of their body still in order to attract prey. Another technique is to let small fish and crustaceans settle on top of them in order to attract larger prey which they can then ambush!
So what do they prey on? They have a varied diet of invertebrates, fish, and sharks. With powerful jaws, a jaw structure which facilitates dislocation, and sharp teeth that point inwards, they are able to hold onto large prey before swallowing it whole. In fact there is a documented case of a 1.3m/4.3ft tasselled wobbegong managing to catch and swallow a 1.0m/3.3ft brownbanded bamboo shark!
Image Credit Andy Murch Sharks and Rays
Reproduction
They are ovoviviparous, meaning that babies develop inside the mum inside eggs, nourished by egg yolk, then hatch inside the womb and are later given birth to as live young - 8 inch long adorable miniature versions of the adults! They are then thought to have lifespans as long as 25-30 years.
Threats
This species is not targeted by any commercial fisheries, and is rarely caught as bycatch. However, their preference for reef habitats means they are threatened by reef degradation due to pollution, overfishing, destructive fishing, coastal development, and warming oceans.
Status
The International Union for Conservation of Nature (IUCN) has assessed this species as Least Concern.
Fun Fact
They can walk! Well, they are known to “crawl” along the ocean floor using their pectoral fins. This slow shuffling movement allows them to move to new hunting spots without attracting the attention of potential prey.
Works Cited
Eucrossorhinus Dasypogon (no date) Discover Fishes. Available at: https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/eucrossorhinus-dasypogon/ (Accessed: 05 December 2024).
Ceccarelli, D.M. and Williamson, D.H. (2012) ‘Sharks that eat sharks: Opportunistic predation by Wobbegongs’, Coral Reefs, 31(2), pp. 471–471. doi:10.1007/s00338-012-0878-z.
Wobbegongs - five species encountered in Queensland (queensland primary industries and fisheries) (no date) (Queensland Primary Industries and Fisheries). Available at: https://web.archive.org/web/20090614190228/http:/www.dpi.qld.gov.au/cps/rde/dpi/hs.xsl/28_12484_ENA_HTML.htm (Accessed: 05 December 2024).
Comments