Chapter 6 Marine Vertebrates Although occupying a single subphylum, vertebrates rival nearly all other phyla in terms of diversity and ecology. They occupy all marine habitats and are important players in nearly all marine food webs. Copyright © 2004 Jones and Bartlett Publishers

Vertebrate Features All vertebrates possess the standard chordate features as well as All vertebrates possess the standard chordate features as well as –segmental ossification of the notochord –a musculature that is segmented into myomeres –and a closed circulatory system with hemoglobin contained within red blood cells that cannot leave the blood vessels. Chapter 6

Vertebrate Features Fig. 6.1 Generalized structure of a chordate. Fig. 6.1 Generalized structure of a chordate. Chapter 6

Marine Fishes Fishes, which include about 50% of all living vertebrates, are a diverse assemblage that is difficult to characterize but which usually live in water, swim with fins, possess scales, and use gills supplied with a countercurrent circulation for gas exchange. Fishes, which include about 50% of all living vertebrates, are a diverse assemblage that is difficult to characterize but which usually live in water, swim with fins, possess scales, and use gills supplied with a countercurrent circulation for gas exchange. Chapter 6

Marine Fishes Fig. 6.3 Phylogenetic relationships of vertebrate classes, with emphasis on modern fish groups. Class names are in color. Fig. 6.3 Phylogenetic relationships of vertebrate classes, with emphasis on modern fish groups. Class names are in color. Chapter 6

Marine Fishes Chapter 6

Marine Fishes Agnatha—The Jawless Fishes Agnatha—The Jawless Fishes –Agnathans are living jawless fishes that are distinguished from other vertebrates by their lack of a jaw, paired fins, and scales. –Hagfishes are marine benthic scavengers that possess unique slime glands, whereas lampreys are anadromous creatures that often parasitize teleosts as adults. Chapter 6

Marine Fishes Chondrichthyes Chondrichthyes –The sharks, rays, and chimeras of class Chondrichthyes are mostly marine fishes that often grow to large sizes, retain metabolic waste products (urea and trimethylamine oxide [TMAO]) to achieve osmotic equilibrium with seawater, and possess a characteristic heterocercal caudal fin. Chapter 6

Marine Fishes Chondrichthyes Chondrichthyes Chapter 6 Fig. 6.9 A pelagic great white shark, Carcharodon. Lift is obtained from its herterocercal tail and the large pectorals extending from the flattened underside of the body.

Marine Fishes Chondrichthyes Chondrichthyes –Chondrichthyans reproduce via internal fertilization –They possess internal embryos that develop inside egg cases –The egg cases are deposited in the environment or are born live after completing their development inside their mothers, both with and without the benefit of a placental attachment to her blood supply. Chapter 6

Marine Fishes Chondrichthyes Chondrichthyes Chapter 6 Fig Developing swell-shark embryo, Cephaloscyllium, enclosed in a tough, protective egg case.

Marine Fishes Osteichthyes—The Bony Fishes Osteichthyes—The Bony Fishes –Many thousands of species of bony fishes are marine, and all but one are ray-finned. Chapter 6

Marine Fishes Chapter 6 Fig Some representative body types of nine common orders of marine fishes. Osteichthyes— The Bony Fishes

Marine Fishes Osteichthyes—The Bony Fishes Osteichthyes—The Bony Fishes –The only exception is the lobe-finned coelacanth, first collected in the western Indian Ocean but now known from Indonesia as well. Chapter 6

Marine Fishes Osteichthyes—The Bony Fishes Osteichthyes—The Bony Fishes –Fishes swim via thrust generated by highly coordinated movements of many different fins and fin combinations, including lateral movements of the caudal fin, lateral movements of the caudal fin, flapping or undulating pectoral fins, flapping or undulating pectoral fins, fanning of the pectoral fins, fanning of the pectoral fins, or sculling movements of the dorsal and anal fins. or sculling movements of the dorsal and anal fins. Chapter 6

Marine Fishes Osteichthyes— The Bony Fishes Osteichthyes— The Bony Fishes Chapter 6 Fig Examples of body shape specialization for three different swimming modes. Adapted from Webb 1984.

Marine Tetrapods Air-breathing tetrapods that have returned to a sometimes full-time life in the sea includes representatives of reptiles, birds, and mammals. Air-breathing tetrapods that have returned to a sometimes full-time life in the sea includes representatives of reptiles, birds, and mammals. All are hypoosmotic to seawater, and two groups are homeothermic. All are hypoosmotic to seawater, and two groups are homeothermic. Chapter 6

Marine Tetrapods Marine Reptiles Marine Reptiles –About 100 species of sea snakes, seven species of sea turtles, and one representative each of iguana and crocodile are truly marine (other reptiles are estuarine). Chapter 6

Marine Tetrapods Marine Reptiles Marine Reptiles Chapter 6 Fig Some marine reptiles (b) sea snake (a) marine iguana, Amblyrhynchus of the Galapagos Islands (c) green sea turtle, Chelonia

Marine Tetrapods Marine Reptiles and Birds Marine Reptiles and Birds –All marine reptiles, and the closely related sea birds, eliminate excess salts via their kidneys and specialized salt glands contained in their mouths, nostrils, or orbits. Chapter 6

Marine Tetrapods Marine Birds Marine Birds – “Marine” birds range from those that are nearly full-time residents of the sea, such as penguins, to other species that simply visit the shoreline to feed, such as some ducks, geese, and coots. Chapter 6

Marine Tetrapods Marin e Birds Marin e Birds Chapter 6 Fig Bill shapes and pursuit patterns of birds that feed at sea.

Marine Tetrapods Marine Mammals Marine Mammals –Three orders of mammals can be found in the sea, including Carnivora (sea otters and pinnipeds), Carnivora (sea otters and pinnipeds), Sirenia (manatees and dugong), Sirenia (manatees and dugong), and Cetacea (whales, dolphins, and porpoises). and Cetacea (whales, dolphins, and porpoises). Chapter 6

Marine Tetrapods Marine Mammals Marine Mammals –Carnivora (sea otters and pinnipeds) Chapter 6 Fig. 6.31a One type of pinniped: harbor seals, Phoca.

Marine Tetrapods Marine Mammals Marine Mammals – Sirenia (manatees and dugong), Chapter 6 Fig Manatee cow and calf (Trichechus).

Marine Tetrapods Marine Mammals Marine Mammals – Cetacea whales whales dolphins dolphins porpoise s porpoise s Chapter 6 Fig A few species of cetaceans, showing the immense range of body sizes at maturity.

Breath-Hold Diving in Marine Mammals All air-breathing tetrapods are capable of diving deeper and longer than humans, and some species, such as elephant seals, sperm whales, and emperor penguins, can dive to more than 1000 m for longer than an hour. All air-breathing tetrapods are capable of diving deeper and longer than humans, and some species, such as elephant seals, sperm whales, and emperor penguins, can dive to more than 1000 m for longer than an hour. Chapter 6

Breath-Hold Diving in Marine Mammals Fig Comparison of oxygen stores in blood (B), muscles (M), and lungs (L) for several different mammals. Fig Comparison of oxygen stores in blood (B), muscles (M), and lungs (L) for several different mammals. Chapter 6

Vertebrate Sensory Capabilities Chemoreception Chemoreception –Chemoreception is very important to marine fishes, and they may possess some of the most sensitive noses of any animal. –Tetrapods all close their nostrils while under water and therefore rely on their sense of smell very little. Chapter 6

Vertebrate Sensory Capabilities Electroreception and Magnetoreception Electroreception and Magnetoreception –The ability to detect weak electric and electromagnetic fields has been demonstrated in bacteria, cartilaginous and bony fishes, some birds, and possibly some whales. Chapter 6

Vertebrate Sensory Capabilities Vision Vision –Aquatic vision requires alterations to terrestrial visual systems to compensate for the quality and quantity of light available under water. –Marine vertebrates focus by moving the lens within the eye (rather than changing its shape) and detect light with altered ratios of photoreceptor cells and unique visual pigments. Chapter 6

Vertebrate Sensory Capabilities Visio n Visio n Chapter 6 Fig Cross-section of a fish eye. Note the solid, round lens that is focused by being moved toward or away from the retina by the retractor muscle.

Vertebrate Sensory Capabilities Equilibrium Equilibrium Chapter 6 Fig Anatomical location (left) and general structure of a labyrinth/otolith organ of a bony fish.

Vertebrate Sensory Capabilities Sound Reception—Fishes Sound Reception—Fishes –Most marine fishes use lateral lines and labyrinth organs for detecting water-borne sounds. Chapter 6

Vertebrate Sensory Capabilities Sound Reception—Tetrapods Sound Reception—Tetrapods –Most marine tetrapods use anatomic systems for hearing that are very similar to those seen in terrestrial species. –Because sound travels about five times faster in water, cetaceans have evolved alternative routes for sound conduction to the sensory hair cells in their cochlea. Chapter 6