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Lecture 4 Chondrichthyes I — Shark Diversity Inaugural Day Ichthyology Lecture

Lecture 4 Chondrichthyes I — Shark Diversityfishesofgeorgia.uga.edu/content/ICH4050/deadpesco/...Typically sharks, skates, and rays usually have 5, sometimes 6 or 7 external gill

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Page 1: Lecture 4 Chondrichthyes I — Shark Diversityfishesofgeorgia.uga.edu/content/ICH4050/deadpesco/...Typically sharks, skates, and rays usually have 5, sometimes 6 or 7 external gill

Lecture 4 Chondrichthyes I — Shark Diversity

Inaugural DayIchthyology Lecture

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Lecture 4 Chondrichthyes I — Shark Diversity

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SHARK

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Cartilaginous fishes: Sharks, skates, rays, chimaeras (ratfishes)• Date to Silurian – 450 MYA; major radiations in the

Paleozoic and Mesozoic (including the branch that includes modern sharks, skates and rays; talk more in a few weeks)

• Today: overview of the diversity of extant Chondrichthyians, major traits and adaptations – especially of the elasmobranchs

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Ages of RockbyRay Troll

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Superclass Gnathostomata

Placodermi {extinct}

ChondrichthyesCartilaginous fishes

Acanthodii {extinct}

SarcopterygiiLobe-finned fishes, tetrapods

ActinopterygiiRay-finned fishes

Classes:Jawed vertebrates

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Class Chondrichthyes (cartilaginous fishes) Subclass Elasmobranchii (sharklike fishes) Infraclass Euselachii (modern sharks and rays)

Subclass Holocephali Superorder Holocephalimorpha (chimaeras)

Living chondrichthyans are in 2 major groups:

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Class Chondrichthyes (cartilaginous fishes) Subclass Elasmobranchii (sharklike fishes) Infraclass Euselachii (modern sharks and rays)

Subclass Holocephali Superorder Holocephalimorpha (chimaeras)

Living chondrichthyans are in 2 major groups:

9 orders of ‘sharks’ - > 403 species

4 order of ‘skates and rays’ - > 534 species

Plus many undescribed spp; rays most diverse

1 order - 33 species

970 EXTANT species 8

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Modern elasmobranchs generally large >1 m with a calcified but seldom ossified skeleton. They differ from bony fishes in that:1) Skull lacks sutures 2) teeth are NOT fused to the jaws but are instead embedded in the connective tissue of the jaws. 3) Teeth, which have the same embryonic origin as and may be derived from placoid scales are replaced serially; such replacement is less common in osteichthyans. 4) The biting edge of the upper jaw is formed by the palatoquadrate cartilage, rather than by the maxillary or premaxillary bones. The palatoquadrate is free from the brain case, creating a protrusible upper jaw during feeding (amphistylic condition). 5) The mouth is subterminal (= ventral). Nasal openings are ventral and incompletely divided by a flap into incurrent and excurrent portions; bony fishes generally have completely separated, dorsally-positioned nasal openings. 6) Fin rays in elasmobranchs are soft, horny, unsegmented ceratotrichia. (from Helfman et al. )

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Typically sharks, skates, and rays usually have 5, sometimes 6 or 7 external gill slits. The first gill slit of elasmobranchs is often modified as a spiracle, supported by the hyoid arch and first functional gill arch.

Elasmobranchs lack lungs and gas bladders, but possess large, buoyant livers and spiral valve intestines.

Internal fertilization is universal to the group; males possess pelvic-fin derived intromittent organs (myxopterygia or claspers) and females either lay eggs or nourish embryos internally for several months before giving birth.

Chloride ions, and metabolic waste products in the form of urea and trimethylamine oxide (TMAO, an ammonia derivative), are concentrated in the blood and serve in osmotic regulation.

A single cloaca serves as an anal and urogenital opening. (from Helfman et al. Ch 12)

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Class Chondrichthyes (cartilaginous fishes) Subclass Elasmobranchii (sharklike fishes) Infraclass Euselachii (sharks and rays and related fossils) Division Neoselachii (includes modern sharks and rays) Subdivision Selachii (sharks 9 Orders)

Subdivision Batoidea (skates and rays 4 Orders)

have (1) gill openings on the sides of the body; (2) the anterior edge of the pectoral fin not attached to the side of the head; (3) anal fin present in galeomorphi but absent in squalomorphi (except for the 5 species of hexanchiformes); and (4) have small lateral spiracles compared with large dorsal spiracles in rays.

(1) gill openings ventral; (2) anterior edge of enlarged pectoral fin attached to the side of the head; (3) anal fin absent; (4) intake of water for breathing chiefly through an enlarged dorsal spiracle (except in water column species).

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Phylogenetic Relationships among living chondrichthyans

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Sharks

HeterodontiformesBullhead sharks 1 family, 9 spp

OrectolobiformesCarpet sharks 7 families, 32 spp

LamniformesMackerel sharks 7 families, 15 spp

CarcharhiniformesGround sharks 8 families, >224 spp

SquatiniformesAngel sharks 1 family, 15 spp

PristiophoriformesSaw sharks 1 family, 9 spp

SqualiformesDogfish sharks 6 families, > 97 spp

HexanchiformesSix-gill sharks 2 families, 5 spp

> 403 spp in 9 orders

> 75% of species in 2 orders

EchinorhiniformesBramble sharks 1 genus, 2 spp

SelachiiGaleomorphi

Squalomorphi

Anal Fin Present

Anal Fin Absent

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Class Chondrichthyes (cartilaginous fishes) Subclass Elasmobranchii (sharklike fishes) Infraclass Euselachii (sharks and rays) Division Neoselachii Subdivision Selachii (sharks) Superorder Galeomorphi (Anal Fin Present) Order Heterodontiformes (8 species, marine): Heterodontidae (bullhead, horn sharks) Order Orectolobiformes (32 species, marine): Parascyllidae (collared carpet sharks),

Brachaeluridae (blind sharks), Orectolobidae (wobbegongs), Hemiscylliidae (bamboo sharks), Stegostomatidae (zebra sharks), Ginglymostomatidae (nurse sharks), Rhincodontidae (whale sharks)

Order Lamniformes (15 species, marine): Odontaspididae (sand tiger sharks), Mitsukurinidae (goblin sharks), Pseudocarchariidae (crocodile sharks), Megachasmidae (megamouth sharks), Alopiidae (thresher sharks), Cetorhinidae (basking sharks), Lamnidae (mackerel sharks)

Order Carcharhiniformes (224 species, mostly marine): Scyliorhinidae (cat sharks), Proscylliidae (finback cat sharks), Pseudotriakidae (false cat sharks), Leptochariidae (barbeled hound sharks), Triakidae (houndsharks), Hemigaleidae (weasel sharks), Carcharhinidae (requiem sharks), Sphyrnidae (hammerhead sharks)

Superorder Squalomorphi (Anal Fin Absent-except Hexanchiformes) Order Hexanchiformes (5 species, marine): Chlamydoselachidae (frill sharks), Hexanchidae

(cow sharks) Order Echinorhiniformes (2 species, marine): Echinorhinidae (bramble sharks) Order Squaliformes (97 species, marine): Squalidae (dogfish sharks), Centrophoridae

(gulper sharks), Etmopteridae (lantern sharks), Somniosidae (sleeper sharks), Oxynotidae (rough sharks), Dalatiidae (kitefin sharks)

Order Squatiniformes (15 species, marine): Squatinidae (angel sharks) Order Pristiophoriformes (5 species, marine): Pristiophoridae (saw sharks)

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http://www.marinebiodiversity.ca/shark/english/key/key1.htm

http://www.marinebiodiversity.ca/shark/english/index.htm

http://www.flmnh.ufl.edu/fish/sharks/sharks.htm

 Florida Museum of Natural History

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Orectolobiformes, carpet sharks, 32 species, mouth well in front of eyes, but variedambush predators on octopi, invertebrates and fishes

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Orectolobis ornatusBanded wobbegong

Class: Carlilagenous Fishes (Chondrichthyes) Order: Carpetsharks (Orectolobiformes) Family: Wobbegongs (Orectolobidae) Genus: Orectolobus (Orectolobus)

Order - OrectolobiformesFamily - GinglymostomatidaeGenus - GinglymostomaSpecies - cirratum

Ginglymostoma cirratumNurse Shark

Orectolobiformes — carpet sharks, 7 families, 32spp

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Rhincodon typusWhale Shark

Class: Carlilagenous Fishes (Chondrichthyes) Order: Carpetsharks (Orectolobiformes) Family: Rhincodontidae Genus: Rhincodon typus

The whale shark was first described and named by Andrew Smith in 1828, based on a specimen harpooned in Table Bay, South Africa. Historically, there have been many synonyms (alternative scientific names) for family, genus and species names. The first scientific printing of the genus name appeared as Rincodon, despite Smith's desired name of Rhineodon. However, in 1984 the International Commission on Zoological Nomenclature suppressed previous generic variations in favor of genus name Rhincodon, and the family name Rhincodontidae.

Orectolobiformes — carpet sharks, 7 families, 32spp

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Rhincodon typusWhale Shark

Class: Carlilagenous Fishes (Chondrichthyes) Order: Carpetsharks (Orectolobiformes) Family: Rhincodontidae Genus: Rhincodon typus

Orectolobiformes — carpet sharks, 7 families, 32spp

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BLUE SHARKOrder - CarcharhiniformesFamily - CarcharhinidaeGenus - Prionace glauca

TIGER SHARKOrder - CarcharhiniformesFamily - CarcharhinidaeGenus - Galeocerdo cuvier

GREAT HAMMERHEADOrder - CarcharhiniformesFamily - SphyrnidaeGenus - Sphyrna mokarran

Carchariniformes— ground or requiem sharkslack gill rakers--largest group, 8 families, 49 genera, > 224 spp mouth extends behind eye

...as of Nelson 2006, in family Sphyrinidae, to paraphrase Archie Carr “..any damned fool knows a hammerhead..”

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Lamniformes— mackerel sharks7 families, 10 genera, 15spp. pelagic

Order: LamniformesFamily: LamnidaeGenus: Lamna ditropis

Order: LamniformesFamily: OdontaspididaeGenus: Carcharias taurus

Order - LamniformesFamily - LamnidaeGenus - Carcharodon carcharias

MEGAMOUTH SHARKOrder - LamniformesFamily - MegachasmidaeGenus - Megachasma pelagios

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6m Greenland Shark

Squaliformes, dogfish sharks6 families, 24 genera, >97spp no anal fin

PRICKLY DOGFISH

Order: Squaliformes Family: OxynotidaeGenus: Oxynotus bruniensis

GREENLAND SHARK

Order: SqualiformesFamily: SomniosidaeGenus: Somniosus microcephalus

Although the Greenland shark is poisonous if eaten fresh, it is edible when the meat has been dried. The flesh of the shark contains high concentrations of urea and trimethylamine oxide TMAO, which is said to be intoxicating, inducing an alcoholic affect. For this reason, natives of Greenland are known to call someone who is drunk "shark-sick." SPINY DOGFISH

Order: Squaliformes Family: SqualidaeGenus: Squalus acanthias

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Hexanchiformes, six-gill sharks2 families,4 genera 5 spp

FRILL SHARK

Order: HexanchiformesFamily: ChlamydoselachidaeGenus: Chlamydoselachus anguineus

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dae

dae

Batoidea ____> 534 spp in 4 Orders

PristidaeSawfishes, 7 spp

Pristiformes1 family, 7 spp

Torpedinidae, NarcinidaeElectric rays, 59 spp

Torpediniformes2 families, 59 spp

Myliobatidae, Dasyatidae, 8 othersStingrays,183 spp

Myliobatiformes10 families, 183 spp

RajiformesRajidae, Rhinobatidae, 2 other families w/5 spp

285 spp

RajidaeSkates, 238 spp

RhinobatidaeGuitarfishes, 42 spp

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Subdivision Batoidea (skates and rays) Order Torpediniformes (59 species, marine): Torpedinidae (torpedo

electric rays), Narcinidae (numbfishes) Order Pristiformes (7 species, marine and freshwater): Pristidae

(sawfishes) Order Rajiformes (285 species, marine): Rhinidae (bowmouth

guitarfishes), Rhynchobatidae (wedgefishes), Rhinobatidae (guitarfishes), Rajidae (skates)

Order Myliobatiformes (183 species, marine and freshwater): Platyrhinidae (thornbacks), Zanobatidae (panrays), Hexatrygonidae (sixgill stingrays), Plesiobatidae (deepwater stingrays), Urolophidae (round stingrays), Urotrygonidae (American round stingrays), Dasyatidae (whiptail stingrays), Potamotrygonidae (river stingrays), Gymnuridae (butterfly rays), Myliobatidae (eagle rays)

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Rajiformes, skates and rays

anterior edge of enlarged pectoral fin attached to side of head

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Rhynchobatidae — wedgefishes 1 genus 4 spp

WHITESPOTTED GUITARFISHOrder - RajiformesFamily - RhynchobatidaeGenus - Rhybchobatus djiddensis

RAJIFORMES. wedgefishes can be large, up to 3m and > 200kg

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SawfishesPristiformes1 Family, 2 genera7 spp.up to 7m!*note pectoral fins

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LESSER ELECTRIC RAYOrder - TorpediniformesFamily - NarcinidaeGenus - Narcine brasiliensis

Electric Rays 2 families> 59spp “Numbfishes”

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SPOTTED EAGLE RAY

Order: MyliobatiformesFamily: MyliobatidaeGenus: Aetobatus narinari

Myliobatiformes — stingrays 10 families >200 spp1 to 2 caudal spines, mostly marine, freshwater exceptions

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600 kgGiant Freshwater Stingray, Himantura chaeophraya

up to 2m disk width, 600kg!! rivers in Thailand,Borneo,New Guinea, Australia

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MANTA

Order: MyliobatiformesFamily: MobulidaeGenus: Manta birostris

Devil rays—”only living vertebrate with three pairs of functional limbs” cephalic pair -anterior subdivision of pectorals. Uses cephalic fins to guide plankton, fishes, crustaceans into terminal mouth.

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River Stingrays- Potamotrygonidae, 20 spp.

Restricted to low salinity, have lost the ability to survive in more than 15 ppt salinity

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Subclass Holocephali! Superorder Holocephalimorpha (6 extinct orders

and modern chimaeras (also known as ratfishes and rabbitfishes), from Late Devonian to present (much reduced diversity after Permian).

!! ! Order Chimaeriformes (modern chimaeras) (33

species, marine): Callorhinchidae (plownose chimaeras), Rhinochimaeridae (longnose chimaeras), Chimaeridae (shortnose chimaeras or ratfishes)

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Most characters that define elasombranchs also describe Holocephalans-indicating a common but unknown ancestor.

What they share: 1) cartilaginous skeleton, 2) sutureless skull, 3)ceratotrichial fins, 4) spiral valve intestine, 5) lack lungs and gas bladders, 6) use oil-filled liver for buoyancy, 6) direct development without a larval stage.

Differences include: 1) upper jaws immovable attached to the braincase (holostylic condition-hence “whole head” for “Holocephali”, 2) teeth are continually growing, crushing plates instead of serially replaced dentition, 3) Chimaeras have 3 pairs of tooth plates-two pair of vomerine and palatine plate pairs in the upper jaws and a large mandibular pair on the bottom (hence rabbitfish)-anterior plates are blade-like and posterior are flattened for crushing hard prey items, 4) 4 internal gill openings covered by gill flap, 5) lack spiracular gill opening, 6) No cloaca, separate anal and urogenital openings, 7) males with shark-like pelvic claspers, extensions of the pelvic fins and pre-pelvic stout spines called tenaculae used to anchor the female during copulation, 8) males also have a frontal tenaculum on the head used to grasp the females pectoral fin during copulation, 9) generally lack scales-except for denticles on midline of back and claspers of male. They are oviparous-laying few 10cm eggs in horny shells. First dorsal spine is poison laden, erectable, not fixed (Helfman et al.)

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Didier and Seret, 2002, Cybium 26(3)225-233.

DIDIER & SÉRET Chimeroid fishes of New Caledonia

bital canal. In Hydrolagus trolli the preopercular and oral canals branch together from the infraorbital canal and share a short common branch (Fig. 2A), and occasionally appear to fork together from the infraorbital canal. Variations on this pattern are rare, with the only exception being MNHN 1998-680 in which the oral and preopercular canals on one side of the head branch separately from the infraorbital canal. The trunk canal is nearly straight, sometimes with gentle undulations in the mid-trunk region.

Secondary sexual characteristicsPresent only in sexually mature males these features are

shown in figure 6. The frontal tenaculum, located medially on the head just anterior to the eyes, is relatively slender at its base and curves gently to terminate in a large, spinous bulb which rests in a pouch of skin atop the head. The distal bulb bears 8-10 overlapping rows of denticles along the underside of the bulb. Dorsal surface of the tenaculum upturned distally with denticles extending onto the dorsal surface along the upturned edge. Paired prepelvic tenacula articulate with anterior edge of pelvic girdle and each is concealed in a slit-like pouch on the ventral surface of the body just anterior to the pelvic fins. Prepelvic tenacula spatulate, curved along the lateral edge, with an indentation along the distal edge and a prominent medial point. A fleshy fold of skin partially covers the lateral side of the blade. 4-5 prominent denticles along medial edge. Paired pelvic clasp-ers are large with a muscular base and fleshy, bulbous tips covered in a shagreen of fine denticles. Pelvic claspers are bifurcate, divided distally for 1/3 their length, with a third, fleshy lobe that lies along the dorsal side of the me-dial cartilaginous arm. The medial arm is slender, bent at its distal end, with a small fleshy tip, and the lateral arm is more robust with a large fleshy tip. The clasper groove runs the length of the pelvic clasper and into a hollow central groove within the lateral arm of the clasper. Pelvic claspers dark purplish with paler fleshy tips varying from purplish to white;. reaching to, and usually beyond, distal edge of pel-vic fins. An anal pad is present in females. Sexual maturity probably reached at about 650 mm BDL in males and 550 mm in females.

EtymologyNamed for Ray Troll, an artist of fishes, and one of the

few true chimaeroid lovers of the world. This fish is named in his honor for his valiant efforts to increase ratfish aware-ness worldwide.

RemarksHydrolagus trolli is presently known from deep water

fishing grounds off New Zealand and New Caledonia in depths ranging from 612-1707 m. It looks similar, in shape and color, to the eastern north Atlantic species Hydrolagus

pallidus Hardy & Stehmann, 1990; so a side-by-side com-parison was necessary to confirm the distinction between these two species. Both are relatively large-bodied species with a pale bluish or grayish color, they share a pointed snout and dark margin around the eye and have preopercular and oral canals that may branch together. However, H. pal-lidus is generally a larger-bodied species with larger head and eye (EYL 31.1-38.3 mm; 20-24% HDL), reaches sexu-al maturity at greater sizes than H. trolli (TL > 1000 mm; BDL > 700 mm), usually has canals that branch separately rather than together, and has a spine that is usually longer than the first dorsal fin. Additionally, H. trolli can be distin-guished from H. pallidus by a more pointer snout and nar-rower head, more obvious dark ring around the eye and deeper blue color, turning brown or purplish in fixative whereas H. pallidus usually turns pale to whitish in fixative.

Cybium 2002, 26(3) 231

Figure 6. - Secondary sexual characteristics of adult males of Hydolagus trolli sp. n. A: Frontal tenaculum in dorsal and lateral view. B: Prepelvic tenaculum in dorsal view showing denticles along medial edge and fold of skin on lateral surface. C: Pelvic clasper in ventral (left) and dorsal (right) views. Arrow indicates dashed line marking the location of the clasper groove.

(1) The Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103, USA. [[email protected]](2) Antenne IRD, laboratoire d’Ichtyologie générale et appliquée, Muséum national d’Histoire naturelle, 43 rue Cuvier, 75231 Paris Cedex 05, FRANCE. [[email protected]]

CHIMAEROID FISHES OF NEW CALEDONIA WITH DESCRIPTION OF A NEW SPECIES OF HYDROLAGUS

(CHONDRICHTHYES, HOLOCEPHALI)

by

Dominique A. DIDIER (1) & Bernard SÉRET (2)

ABSTRACT. - Three species of chimaeroid fishes are reported from deep waters around New Caledonia: Chimaera phantasma, Rhinochimaera pacifica and Hydrolagus trolli n. sp., which is described from 23 specimens collected from New Caledonia and New Zealand at depths of 612 - 1707 m. The new species is distinguished from all other members of the genus by its blue-gray coloration, distinctly pointed snout, first dorsal fin concave along its posterior edge with a pale margin, preopercular and oral lateral-line canals usually sharing a common branch, males with a robust frontal tenaculum with the distal bulb upturned at its distal edge, denticles extending onto the dorsal surface and bifid pelvic claspers with the distal 1/3 divided and pale colored, fleshy distal lobes.

RÉSUMÉ. - Chimères de Nouvelle-Calédonie et description d’une nouvelle espèce du genre Hydrolagus (Chondrichthyes, Holocephali).

Trois espèces de chimères sont signalées dans les eaux profondes de Nouvelle-Calédonie: Chimaera phantasma, Rhinochimaera pacifica et Hydrolagus trolli sp. n., qui est décrite à partir de 23 spécimens collectés en Nouvelle-Calédonie et en Nouvelle-Zélande, entre 612 et 1707 m de profondeur. Cette nouvelle espèce se distingue de ses congé-nères par sa coloration gris-bleu, son museau nettement pointu, le bord postérieur de sa première nageoire dorsale concave et liseré de blanc, les canaux préoperculaires et oraux de la ligne latérale avec une branche commune, le tenaculum fron-tal des mâles robuste avec un bulbe distal retroussé et portant des denticules cutanés qui s’étendent sur sa face dorsale, les ptérygopodes bifides, leur tiers distal étant divisé en lobes charnus de couleur claire.

Key words. - Chondrichthyes - Holocephali - Chimaeroid - Chimaera - Rhinochimaera - Hydrolagus - PSW - New Caledonia - New species.

A large variety of chimaeroids are present in the south-ern Pacific Ocean. In particular, many new species have recently been discovered around New Zealand and Australia due to concentrated efforts in surveying these faunas (e.g., Paulin et al., 1989; Last and Stevens, 1994).

In the same way, France has been carried out a series of deep sea exploratory cruises in the South-West Pacific (Richer de Forges, 1993; Séret, 1997; Séret et al., 1997). These cruises revealed a high diversity of deep water fishes in the New Caledonian zone and also provided samples of a number of chondrichthyan fishes (Séret, 1994; Séret in Grandperrin et al., 1997, 1999) including the chimaeroids herein described. The biogeographical significance of the New Caledonian chondrichthyan fauna in the tropical Australasian region has been pointed out by Last and Séret (1999).

At present there are at least 5 undescribed species of Chimaera and 5 new species of Hydrolagus known from southern Pacific Ocean. All of the recently discovered spe-cies of chimaeroids belong to the family Chimaeridae and

Cybium 2002, 26(3): 225-233.

the two genera are distinguished by an anal fin anterior to the ventral caudal fin lobe (Chimaera) or absence of a sepa-rate anal fin (Hydrolagus). In addition to the discovery of new species, deep ocean trawling surveys are an important source for determining the geographic ranges of many spe-cies. Chimaera phantasma Jordan & Snyder, 1900 and Rhinochimaera pacifica (Misukuri, 1895) are newly report-ed from waters off New Caledonia. These records represent range extensions for both of these species.

MATERIAL AND METHODS

Specimens were collected by bottom trawl around New Caledonia during the HALIPRO 2 and HALICAL 1 cruises of 1995 and 1996. A total of 10 chimaeroid specimens were collected: 3 specimens of Rhinochimaera pacifica, 4 speci-mens of Chimaera phantasma, and 3 specimens of a previ-ously undescribed species of Hydrolagus. This new species of Hydrolagus has also been collected from deep water fish-

Hydrolagus trolli 38

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Subclass Holocephali Superorder Holocephalimorpha ! Order Chimaeriformes chimaeras/ratfishes, 3 families,ca. 33 spp

chimerical \ky-MER-ih-kuhl; -MIR-; kih-\, adjective:

1. Merely imaginary; produced by or as if by a wildly fanciful imagination; fantastic; improbable or unrealistic.

Chimerical is ultimately derived from Greek khimaira, "she-goat" or "chimera," which in Greek mythology was a monster having the head of a lion, the body of a goat, and the tail of a dragon.

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http://www.youtube.com/watch?v=M2r1qChVtQIRatfish Rule

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• endoskeleton calcification

• pelvic claspers

• placoid scales

• teeth usually not fused to jaws, replaced serially

• fin rays soft, unsegmented ____________________

• biting edge of upper jaw formed by palatoquadrate

• swimbladder and lung absent

• usually high concentrations of urea and trimethylamine oxide in blood (osmoregualtion)

• intestinal spiral valve

Chondrichthyan characteristics include:

Key synapomorphies

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Placoid scales

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REPLACEMENT DENTITON

Tiger Shark Teeth

In bony fishes teeth attached directlyto bone, IN sharks teeth embedded inconnective tissue-and only on jawmargins, not other structures in mouth.Basically enlarged scales embryologicallyReplacement occurs regardless of use,nonfunctional teeth in interior rows grow and move forward, displacing or replacing functional teeth. Turnover rates for sharks in captivity range from 2 days to 8 or 10 to 28, giving an estimate of the order of 30,000 IN A LIFETIME

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Rays and Skates usually with crushing ‘pavement teeth’

Barn-door skate Raja laevis Mitchill 1817

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1. Large size

2. Marine

General Chondrichthyan Traits

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Freshwater exceptions…

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3. Mobile!

Local nearshore 100’s km bull, nurse, bonnetheadCoastal 1000’s kms along continental shelves, sandbar, blacktip duskyOceanic -- 10s of 1000‘s km migrate across ocean basins whale, white, blue

Oil-based buoyancy (livers up to 90% oil) allows for large vertical migrations-without adjusting air bladders-sharks essentially neutrally buoyant. Reduced skeletal density -55% density of bone.

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4. PredatoryTop of Food Webscarnivores or scavengers

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Sawfishes and saw sharks - Pristid sawfishes (Rajiforms), pristophorid sawsharks (Pristophoriformes) – bladelike snouts with lateral teeth – slash to stun prey

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Cookie cutter sharks, Isistius brasiliensis ectoparasitic elasmobranch-ventral surface covered with photophores_____ ______, shark bites from above attacking prey attracted to the light, spinning and removing a plug of flesh!

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Filter Feeders

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ICHTHYILLITERACY OF THE DAY

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5. Internal fertilization

Whitetip reef sharks; from Pratt and Carrier 2001

Claspers, MaleSand-Tiger Shark(Lamniformes)Myxopterygia

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6. Direct development and precocial young

7. Low fecundity, late maturation

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I All nutrition from yolk sac

A. Yolk sac viviparity (= lecithotrophic viviparity, ovoviparity): all living orders except heterodontiforms, lamniforms, and rajiforms

B. Yolk sac oviparity (= lecithotrophic oviparity): all living holocephalans, all Heterodontiformes, some Orectolobiformes, some Carcharhiniformes and all

Rajiformes

II Some nutrition from mother (= matrotrophy)

A. Nutrition from uterine secretions (= histotrophy): many squaliforms and carchariniforms, and all myliobatiforms

B. Nutrition from eating unfertilized eggs (= oophagy): all lamniforms and some carchariniforms (includes embryophagy of Carcharias taurus) and pseudotriakids

A summary of embryonic development and nutrition in chondrichthyans. From Nelson (2006), after Musick and Ellis (2005).

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MODES OF EMBRYONIC NUTRITION

The alternative condition is egg-laying (oviparity), with the embryo deriving ALL nutrition from its large yolk reserves. About 40% of living elasmobranchs are oviparous, including bullhead sharks (Heterodontiformes), many nurse sharks (Orectolobiformes), as well as all skates (Rajiformes). Clutch sizes among oviparous sharks and batoids both average about 60 eggs per year (Musick and Ellis 2005).

Shark and skate egg cases large (2-4cm) horny keratonoid shell protecting a single embryo, attached to seaweed or other structure-the embryo develops weeks up to 15 months.

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In about half of live-bearing species, the developing embryo is retained in the uterus and nourished with yolk provided by a yolk sac that is attached directly to the digestive system of the embryo (termed variously yolksac-, lecithotrophic-, or aplacental-viviparity, and also ovoviviparity)-many species including frill, cow, dogfish, angel, some carcharhinids and orectolobids (tiger and nurse), whale shark (up to 300 embryos-most fecund shark known), sawfishes and torpedo rays.

Some ovoviviparous sharks have evolved an additional form of nourishment- oophagy- in which the young feed on ovulated eggs after exhausting yolk reserves (threshers, whites, makos, sand tigers. Sand tigers carry this further the first embryo to consume its yolk, eats its siblings (embryophagy) before assuming an oophagus existence. At birth, litter size in sand tigers is 2 large (1m) young, one in each uterus.

About 70% of living sharks and all ray species bear live young

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Extra Credit Tiny Desk Lecture

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The most complex development pattern is placental viviparity, in which the spent yolk sac attaches to the uterine wall to form a yolk-sac placenta. The stalk of the yolk sac forms an umbilical cord, attached to the embryo between the pectoral fins, transporting nutrients and oxygen to the embryo and metabolic wastes to the mother. In some sharks such as hammerheads and sharpnose, the cord diversifies and develops outgrowths (appendicula) that serve as sites for exchange of materials, including uptake of nutrients, from the “uterine milk”. In myliobatoid stingrays and manta rays, nourishment is obtained solely from ‘uterine milk’ without a placental connection-termed uterine viviparity.

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Part III Taxonomy, phylogeny, and evolution222

than for most bony fi shes, except perhaps the electrogenic elephantfi shes (Mormyridae; see Chapter 14). The ratio of brain to body weight in sharks is actually more comparable to that of “higher animals” such as some birds and marsupi-als (Fig. 12.13A). Within feeding types and habitat zones, many sharks have larger brains than ecologically compara-ble bony fi shes such as pelagic, predatory billfi shes and tunas, which in fact have relatively large brains relative to other teleosts (Lisney & Collin 2006) (Fig. 12.13B). Requiem and Mackerel sharks have large forebrains and complex cerebellums; eagle rays and other stingrays have the most complex brains (Northcutt 1977).

Reproduction and developmentA few generalizations can be made about shark reproduc-tion (Carrier et al. 2004; Musick & Ellis 2005). Ages at

in the inner ear has been implicated as a component of geomagnetic orientation (Vilches-Troya et al. 1984).

It has been noted that the ampullary electroreceptors are geometrically centered around the mouth of many elasmo-branchs. This positioning could allow a shark or ray to home precisely on a potential food source solely by elec-troreception, effectively aligning the food in the “sights” of its receptor fi eld and then engulfi ng the prey. In this way, sharks can detect prey buried in the sand or sit motionless in the dark and snap up prey that swim nearby (Kalmijn 1982; Tricas 1982).

Extreme sensitivity to environmental stimuli is of no use to an animal unless the information can be collected, proc-essed, and acted upon. Such integration is the role of the central nervous system, particularly the brain. Not surpris-ingly, the ratio of brain to body weight in sharks is greater

(A)

(B)

10,000

1000

100

10

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0.10.001 0.01 0.1 1 10 100

100

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1000 10,000 100,000

Body weight (kg)

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Elasmobranchs

Birds

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in w

eigh

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bra

in m

ass

(g)

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Teleosts

Figure 12.13Brain size in sharks. (A) Sharks have relatively large brains for their body size, overlapping in this respect with birds and mammals as much as with bony fishes. (B) Among pelagic, predatory fishes, many sharks have relatively large brains for their body mass. (A) from Springer and Gold (1989), based on Northcutt (1977) and Moss (1984), used with permission; (B) after Lisney and Collin (2006).

Helfman et al.

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Part III Taxonomy, phylogeny, and evolution222

than for most bony fi shes, except perhaps the electrogenic elephantfi shes (Mormyridae; see Chapter 14). The ratio of brain to body weight in sharks is actually more comparable to that of “higher animals” such as some birds and marsupi-als (Fig. 12.13A). Within feeding types and habitat zones, many sharks have larger brains than ecologically compara-ble bony fi shes such as pelagic, predatory billfi shes and tunas, which in fact have relatively large brains relative to other teleosts (Lisney & Collin 2006) (Fig. 12.13B). Requiem and Mackerel sharks have large forebrains and complex cerebellums; eagle rays and other stingrays have the most complex brains (Northcutt 1977).

Reproduction and developmentA few generalizations can be made about shark reproduc-tion (Carrier et al. 2004; Musick & Ellis 2005). Ages at

in the inner ear has been implicated as a component of geomagnetic orientation (Vilches-Troya et al. 1984).

It has been noted that the ampullary electroreceptors are geometrically centered around the mouth of many elasmo-branchs. This positioning could allow a shark or ray to home precisely on a potential food source solely by elec-troreception, effectively aligning the food in the “sights” of its receptor fi eld and then engulfi ng the prey. In this way, sharks can detect prey buried in the sand or sit motionless in the dark and snap up prey that swim nearby (Kalmijn 1982; Tricas 1982).

Extreme sensitivity to environmental stimuli is of no use to an animal unless the information can be collected, proc-essed, and acted upon. Such integration is the role of the central nervous system, particularly the brain. Not surpris-ingly, the ratio of brain to body weight in sharks is greater

(A)

(B)

10,000

1000

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0.10.001 0.01 0.1 1 10 100

100

100

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Body weight (kg)

Mammals

Elasmobranchs

Birds

Fish

Bra

in w

eigh

t (g)

Log10 body mass (kg)

Log 10

bra

in m

ass

(g)

Sharks

Teleosts

Figure 12.13Brain size in sharks. (A) Sharks have relatively large brains for their body size, overlapping in this respect with birds and mammals as much as with bony fishes. (B) Among pelagic, predatory fishes, many sharks have relatively large brains for their body mass. (A) from Springer and Gold (1989), based on Northcutt (1977) and Moss (1984), used with permission; (B) after Lisney and Collin (2006).

Helfman et al.

Part III Taxonomy, phylogeny, and evolution222

than for most bony fi shes, except perhaps the electrogenic elephantfi shes (Mormyridae; see Chapter 14). The ratio of brain to body weight in sharks is actually more comparable to that of “higher animals” such as some birds and marsupi-als (Fig. 12.13A). Within feeding types and habitat zones, many sharks have larger brains than ecologically compara-ble bony fi shes such as pelagic, predatory billfi shes and tunas, which in fact have relatively large brains relative to other teleosts (Lisney & Collin 2006) (Fig. 12.13B). Requiem and Mackerel sharks have large forebrains and complex cerebellums; eagle rays and other stingrays have the most complex brains (Northcutt 1977).

Reproduction and developmentA few generalizations can be made about shark reproduc-tion (Carrier et al. 2004; Musick & Ellis 2005). Ages at

in the inner ear has been implicated as a component of geomagnetic orientation (Vilches-Troya et al. 1984).

It has been noted that the ampullary electroreceptors are geometrically centered around the mouth of many elasmo-branchs. This positioning could allow a shark or ray to home precisely on a potential food source solely by elec-troreception, effectively aligning the food in the “sights” of its receptor fi eld and then engulfi ng the prey. In this way, sharks can detect prey buried in the sand or sit motionless in the dark and snap up prey that swim nearby (Kalmijn 1982; Tricas 1982).

Extreme sensitivity to environmental stimuli is of no use to an animal unless the information can be collected, proc-essed, and acted upon. Such integration is the role of the central nervous system, particularly the brain. Not surpris-ingly, the ratio of brain to body weight in sharks is greater

(A)

(B)

10,000

1000

100

10

1

0.10.001 0.01 0.1 1 10 100

100

100

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1000 10,000 100,000

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Mammals

Elasmobranchs

Birds

Fish

Bra

in w

eigh

t (g)

Log10 body mass (kg)

Log 10

bra

in m

ass

(g)

Sharks

Teleosts

Figure 12.13Brain size in sharks. (A) Sharks have relatively large brains for their body size, overlapping in this respect with birds and mammals as much as with bony fishes. (B) Among pelagic, predatory fishes, many sharks have relatively large brains for their body mass. (A) from Springer and Gold (1989), based on Northcutt (1977) and Moss (1984), used with permission; (B) after Lisney and Collin (2006).

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10 SEC

30 SEC 2 MIN

8. Large brain, acute nonvisual senses

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Carcharhinus plumbeus

Sharks attracted to energized electrode

Sphyrna lewini

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Ampullae of Lorenzini (after Stephano Lorenzini)

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Ampullae of Lorenzini. Many biological activities have as an integral component the generation of weak electricity. Most notable are muscular contraction, such as heart function and breathing, nerve conduction, and the voltage created by ionic differences between protoplasm and water. A resting flatfish (Pleuronectiformes) creates a low frequency d.c. (direct current) bioelectric field with a strength of more than 0.01 uv/cm (1 hundredth of a microvolt) measured 25 cm away.

Experiments have shown that predatory sharks use weak electrical cues, and ignore strong olfactory cues, to home in on prey. The electrical sensitivity of large sharks is truly amazing. Human sensitivity is on the order of 0.1 volt. Sharks have demonstrated detection thresholds of 1 x 10-9 V/cm or 1 billionth of a volt, approximately 10 times more sensitive than the 0.01 mv output from prey. Such sensitivity would be sufficient to detect the electrical output of a standard D-cell flashlight battery several km away (assuming no background geomagnetic interference), or the bioelectric output of a human 1-2 m away.

Sharks have an additional channel for sensory input that is anatomically and developmentally related to distant-touch and hearing, namely electroreception (Collin and Whitehead 2004). Input for electroreception begins at numerous small pores spaced precisely on the shark's head, snout, and mouth. The pores lead to conductive, jelly-filled canals which terminate in ampullary receptor cells termed ampullae of Lorenzini. The receptor cells, which are anatomically similar to hair cells of the lateral line, fire in response to weak electric fields, sending through afferent fibers via the lateral line nerve to regions in both the mesencephalon and telencephalon of the brain. The function of the ampullae, which are an obvious external feature on most sharks, remained a substantial mystery prior to the discovery of electroreceptive capabilities in sharks.

(from Helfman et al.)68

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Kalmijn 1966: • skates react to currents as low as 0.01 microvolts (uV)/cm = 0.0000001 V• we react to 0.1 V• we are 1 million times less sensitive

Fish produce a D.C. electric fieldof 0.05 uV detectable 25 cm away

= 5X a skate’s sensitivity

LAB EXPERIMENTS ON ELECTRICAL SENSITIVITY

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flatfish in sediment—attracted

flatfish in sediment inside agar block—attracted

Meat in sediment inside agar block—attracted to odor

flatfish in sediment—inside agar block, plastic (electrical) shieldNO ATTRACTION

Two Electrodes in sediment—attracted

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5 nV = 0.000000005 V @ 30 cm, ultimately 1x10-9 or 0.0000000001 V/cm!

Bites at activated pole = 40at control pole = 8at odor source = 2

FIELD EXPERIMENTS

(you wanna talk about nannotechnology?)

Feeding attacks by blue shark Prionace glacuca on electrically simulated prey; os = odor source

d1 = electrodes passing a current of 8 microAmps

d2 = control electrode

Kalmijn 1982 Science

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