“We counted the number of vertebrae, the rows of teeth, the number of valves within the intestines, and examined the microscopic details of the dermal denticles (skin teeth), for any such differences,” commented Dahl. Once they realized it was a single species, the team underwent a full morphological study of zebra sharks encompassing morphometric and meristic measurements. Explained Dahl: “Both of these genes have been successful for distinguishing closely related species and could be an indicator of speciation.” Turns out this morph was not a new species and the zebra shark remains a single species based on genetic data from the COI and ND4 markers. Today’s ‘Quordle’ Answers And Clues For Thursday, June 22ĭoes this new beige color morph mean there is a new species of shark? This possibility was evaluated by DNA barcoding using the COI (cytochrome c oxidase subunit 1) and ND4 (mitochondrial NADH dehydrogenase subunit 4) markers. Thus, it is a possibility that the specimen described by Nakaya was the very first encountered sandy morph, which may be different from the color morph here described from off the coast of East Africa. Uniformly colored zebra sharks aren’t exactly new (they’ve been observed off the coast of Australia recently, for example) and in 1973 scientist Kazuhiro Nakaya described a uniformly colored specimen that he referred to as albino even thought the color of the iris was inconsistent with the lack of pigmentation in true albinos (this shark had a dark brown color instead of the tell-tale pink true albinos have). Zebra sharks are well-known species due to a wide distribution across the Indian and Western Pacific oceans and being quite easy to identify from your average grey-looking shark. Known as carpet sharks due to these animals having a marbled or mottled appearance similar to that of fancy carpet designs, they vary with how they look, the habitat they choose, and their size. Zebra sharks are one of the most iconic of the carpet shark (Orectolobiformes) species, a diverse group originating in the early Jurassic period approximately 200 million years ago that is known for their drastic color changes from juvenile to adulthood. The third diagram shows carpet sharks related to the whale shark, sharing similar characteristics and all having the nurse shark as a root.Sandy zebra shark in a bucket at the Danish National Aquarium Den Blå Planet. This furthers the second diagram, continuing the Orectolobiformes branch. Furthermore, the third diagram shows the relatives of the whale shark: nurse sharks, bamboo sharks, wobbegongs, and zebra sharks. The diagrams above show this order, indicating that it is in this branch where the whale shark begins to emerge. This is otherwise known as the order of the whale shark. Because of the filter feeding of plankton, different orders of sharks begin to arise, one of them being the Orectolobiformes. The filter feeders emerge sometime during the Tertiary Period, 65 to 35 million years ago. After these sharks come the filter feeders. The Hexanchiformes, Chlamydoselachiformes, and frilled sharks reside in deep waters, living during the Jurassic and Cretaceous periods. From this, the first modern sharks begin to appear: the sixgill, sevengill, and frilled. The adaptive radiation that gave way for modern species of sharks occurred about 200 million years ago. These mass extinctions allow adaptive radiation to occur for the sharks, since extinctions remove predators from their habitats. As the mass extinctions begin to occur, the sharks survive through all of them. Sharks then begin to emerge at around the time of 455 or 425 million years ago. This is shown in the first diagram above, where ostracoderms are the root of the cladogram. The evolution of sharks begins about 510 million years ago, where the first fish, ostracoderms, arrived. The whale shark may have a very limited past, but its roots as a shark and relatives can be found and observed.
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