Transcript Chap 16 PP
Subphylum Vertebrata 3 types of fishes (jawless (agnathan), cartilaginous (gnathostome), and bony (gnathostome) Jawless fishes (Agnatha) - A” = without, “gnath” = jaw; jawless fishes, i.e. hagfish (Class Myxini) and lamprey (Class Petromyzontida) Class Chondrichthyes – cartilaginous fishes - sharks, skates, and rays (Subclass Elasmobranchii); chimaeras (Subclass Holocephali) Bony fishes (formerly Class Osteichthyes) - Class Actinopterygii, ray finned fishes and Class Sarcopterygii, lobe-finned fishes Class Myxini – hagfishes (aka slime eels) primarily bottom dwellers within mud in deeper water scavenge on decaying fish carcasses produce large amounts of mucus can tie themselves in knots while feeding Class Petromyzontida - lampreys mainly live in freshwater, but some migrate to ocean Some parasitize fish by attaching to side and sucking blood Class Chondrichtyes – sharks, skates, rays Sharks well adapted for fast swimming and predation skin is sand paper like; placoid scales rows of teeth are actually modified scales Have specialized electrical sensory cells called ampullae of Lorenzini The largest shark (also largest fish) is the whale shark Check out www.flmnh.ufl.edu/fish/sharks/ISAF/ISAF.htm Figure 8.08a Figure 8.12a Male claspers Shark Reproduction - all elasmobranchs reproduce via internal fertilization - fetal development occurs in one of 3 ways; oviparous, ovoviviparous, or viviparous development Oviparity - embryos are contained within an egg case and development occurs outside the female often for several months - embryo nourished by yolk within egg - developed young “hatch” externally fully formed - all skates and some sharks are oviparous Ovoviviparity - eggs are retained within uterus, young are nourished by yolk within egg - young hatch within uterus and are “born” live - most sharks and rays are ovoviviparous - many species exhibit intrauterine cannibalism; sand tiger shark embryos eat smaller siblings, others eat undeveloped eggs - common ovoviviparous species include nurse, mako, great white, thresher, whale, and dogfish sharks Viviparity - young are retained within uterus and nourished in some way by a uterine attachment (approaches placental mammals) - familiar species are hammerhead and bull sharks Figure 8.04 Class Chondrichthyes – skates and rays dorsoventrally flattened; most live on bottom sting rays have a poison tipped spine at base of tail skates do not have a poisonous spine electric rays have electric producing organs most have molar like teeth for crushing shell fish Manta rays and eagle rays “fly” through water using pectoral fins Figure 8.06b Subclass Holocephali – chimaera/ratfish Bony fish – The Osteichthyes approx 23,000 species; about 96% of all fish species and half of all vertebrates have rounded and flattened scales; cycloid, ctenoid, ganoid an operculum covers gills caudal fin usually homocercal fins consist of thin, flexible membrane covering bony spines or fin rays have gas filled swim bladder to adjust buoyancy myriad shapes and forms adapted to almost every type of marine habitat 2 groups; lobe-finned (Class Sarcopterygii) and ray-finned fishes (Class Actinopterygii) Lobe-finned fishes (Sarcopterygii) Extant species include lung fishes and coelacanths Tetrapods evolved from ancestral lineage within this group Paired fins are stout and fleshy allowing for weight bearing movement Pg. 164 Figure 8.08b Swim bladder either fills through direct link to esophogus and “breathes” or bladder is filled by gas exchange from blood vessels 4 gill arches contain anterior facing gill rakers and posterior facing gill filaments with lamellae for gas exchange for respiration. Figure 8.16a Figure 8.16b Figure 8.19 Lateral line picks up vibration; allows fish to sense proximity of other fish, structures Fish Migration Some migrations involve daily feeding migrations to and from feeding areas The most spectacular ones involve breeding migrations Anadromous fishes – live in ocean and migrate to freshwater rivers to spawn (salmon) Catadromous fishes – live in freshwater and migrate to ocean to spawn (freshwater eels) Bony Fish Reproduction The vast majority reproduce by external fertilization, and external development (oviparity) A few species fertilize internally with internal development (ovoviviparity); guppies, surfperch (book example)