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In 15 of the 16 icefish species, the beta subunit gene has been completely deleted and the alpha subunit gene has been partially deleted. [13] One icefish species, Neopagetopsis ionah, has a more complete, but still nonfunctional, hemoglobin gene. [14] Red blood cells (RBCs) are usually absent, and if present, are rare and defunct. [15]
The ocellated icefish (Chionodraco rastrospinosus) is a fish of the family Channichthyidae. [3] [4] It lives in the cold waters off Antarctica and is known for having transparent haemoglobin-free blood. [5] [6] C. rastrospinosus live in the Southern Ocean up to a depth of 1 km. They are most commonly found on the seabed at 200–400 m.
Agnatha (/ ˈ æ ɡ n ə θ ə, æ ɡ ˈ n eɪ θ ə /; [3] from Ancient Greek ἀ-(a-) 'without' and γνάθος (gnáthos) 'jaws') is a paraphyletic infraphylum [4] of non-gnathostome vertebrates, or jawless fish, in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct (conodonts, anaspids, and ostracoderms, among others).
The Southern Ocean has supported fish habitats for 400 million years; however, modern notothenioids likely appeared sometime after the Eocene epoch. [3] This period marked the cooling of the Southern Ocean, resulting in the stable, frigid conditions that have persisted to the present day. [3]
The blood is pumped by three separate hearts: two branchial hearts pump blood to the cuttlefish's pair of gills (one heart for each), and the third pumps blood around the rest of the body. Cuttlefish blood must flow more rapidly than that of most other animals because haemocyanin carries substantially less oxygen than haemoglobin.
Starfish have sensory cells in the epithelium and have simple eyespots and touch-sensitive tentacle-like tube feet at the tips of their arms. Sea urchins have no particular sense organs but do have statocysts that assist in gravitational orientation, and they too have sensory cells in their epidermis, particularly in the tube feet, spines and ...
Worms (Old English for serpent) typically have long cylindrical tube-like bodies and no limbs. Marine worms vary in size from microscopic to over 1 metre (3.3 ft) in length for some marine polychaete worms (bristle worms) [42] and up to 58 metres (190 ft) for the marine nemertean worm (bootlace worm). [43]
The taxonomic term Bivalvia was first used by Linnaeus in the 10th edition of his Systema Naturae in 1758 to refer to animals having shells composed of two valves. [3] More recently, the class was known as Pelecypoda, meaning "axe-foot" (based on the shape of the foot of the animal when extended).