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Natural History of Sharks, Skates, and Rays Phylogeny of Holocephali MARE 394 Dr. Turner

Natural History of Sharks, Skates, and Rays Phylogeny of Holocephali MARE 394 Dr. Turner Summer 2008. Chimaeroid Fishes. Exclusively marine – inhabit all oceans except Arctic & Antarctic Deep water dwelling – 500+m Live on or near bottom Local migrations for breeding

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Natural History of Sharks, Skates, and Rays Phylogeny of Holocephali MARE 394 Dr. Turner

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  1. Natural History of Sharks, Skates, and Rays Phylogeny of Holocephali MARE 394 Dr. Turner Summer 2008

  2. Chimaeroid Fishes Exclusively marine – inhabit all oceans except Arctic & Antarctic Deep water dwelling – 500+m Live on or near bottom Local migrations for breeding Males, females, juveniles form distinct groups

  3. Chimaeroid Ecology Prey on benthic inverts & small fishes Tooth plates used to crush crustaceans, mollusks, & echinoderms – some soft-bodied prey Sharks major predators Mature at 3-4 yrs

  4. Chimaeroid Toothology Holocephalans characterized by ever-growing, nonreplacable hypermineralized tooth plates 6 tooth plates in 3 pairs; 1 lower – 2 upper Mandibular (lower) and vomerine (anterior upper) form beaklike bite Tooth plates typically only fossil remains

  5. Subclass Holocephali Distinguished from other chondrichthyan fishes by morphological features: Mode of fusion of lower jaw to cranium Possession of non-replaceable, hypermineralized tooth plates

  6. Extant Holocephali 33 described species Several new but undescribed; total probably < 45 species All belong to Order Chimaeriformes 3 Families

  7. Order Chimaeriformes Family Callorhichidae 1 Genus, 3 species Family Rhinochimaeridae 3 Genus, 8 species Family Chimaeridae 2 Genus, 22 species

  8. Family Callorhichidae Prominent, plow-shaped snout, torpedo-like body, heterocercal tail, large anal fin Enclosed lateral line canals underneath the skin Plow-nose Chimaeras or elephantfish Most primitive living Chimaera

  9. Family Rhinochimaeridae Long, tapering fleshy snout extending anterior to the head Long-nose chimerians or spookfish Large bodies, elongate spearlike snout, narrow tail with elongate filament Inhabit deep waters; 1000-2000m

  10. Family Chimaeridae Conical fleshy snout bluntly pointed at tip Short-nose chimerians or ratfish Lateral line canals on the snout expanded with wide dilations Compressed, elongate bodies tapering to whip-like tail

  11. Chimaeroid Morphology Slender fishes 60cm – robust fishes >1m Skin scaleless in adults; embedded denticles in small juveniles Single gill opening; adults lack a spiracle 2 dorsal fins, caudal, paired pect & pelvic

  12. Chimaeroid Dimorphism Sexual dimorphism; males possess 2° sexual characteristics: -front tenaculum, paired preprelvic tenacula, and paired pelvic claspers Front tenaculum – small club-like structure on head anterior to eyes unique to chimaeras; used to grasp pectoral fin of ♀ during copulation

  13. Chimaeroid Dimorphism

  14. Chimaeroid Reproduction Embryonic development only described in 2 species Internal fertilization; ♂ transfer sperm via pelvic claspers All chimaroids are oviparous; 2 egg capsules simultaneously – one from each oviduct; several pairs per season

  15. Chimaeroid Egg Capsules

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