Ichthyology Exam 1

Chondrichthyes shared characteristics?

-Simple cranium (No sutures)

-Cartilaginous skeleton

-Lepidotrichia

-Spiral valve intestine

-Oil filled liver

-Males have claspers

-Internal fert

-Placoid scaled

2 subclasses of chondrichthyes?

-Holocephali

-Elasmobranchi

Shared characteristics of elasmobranchs?

-Upper jaw not fused to cranium

-Multiple rows of teeth

-5-7 gill openings

-Snout extends past mouth

How do sharks remain buoyant without a swim bladder?

They have an oil filled liver

How do sharks respirate?

-Ram ventilation and buccal pumping

Shark scale type?

Placoid

Shark jaw suspension?

Hyostylic

How do sharks osmoregulate?

They are isosmotic with seawater (same salinity)

What is the metabolic rate like in sharks?

Low

What threatens shark populations?

-Low reproduction rates and shark fin trade.

What industry is helping bring awareness to sharks?

Ecotourism

Characteristics of Chimaeriformes?

-Autostylic jaw suspension

-Tooth plates

-Operculum covers 4 gill slits

Separate anal and urogenital openings

-Tenaculae

-Mostly scaleless

-Pointed tail

Where are ratfish found?

Benthic zones

How many species of fish are there?

Over 35,000

What are the broad characteristics of a fish?

-Poikilothermic

-Vertebrates

-Paired fins

-Gills

Scales

What are the three major living groups of fish?

-Cyclostomes (jawless fish)

-Chondrichthyes (Cartilaginous fish)

-Osteichthyes (Bony fishes)

What 2 groups make up the cyclostomes?

Mxyini (hagfishes)

Petromyzontida (lampreys)

What 2 groups make up chondrichthyes?

Elasmobranchii (Sharks, skates, and rays)

Holocephali (chimaeras)

What 2 groups make up Osteichthyes?

Sarcopterygii (lobe-finned fishes)

Actinopterygii (ray finned fishes)

Characteristics of Myxini (Hagfishes)?

-No vertebrae

-No paired fins

-No jaws

-No scales

Characteristics of Petromyzontida (lampreys)?

-Simple vertebrae

-No jaws

-No paired fins

-No scales

What 2 groups make up the gnathostomes?

-Chondrichthyes

-Osteichthyes

Characteristics of Chondrichthyes?

-Have jaw and paired fins

-Cartilaginous

-No bones

-Placoid scales

Characteristics of Osteichthyes?

-Ray and lobe-finned fish

-Most modern fish

-Jaws and paired fins

-Bony skeleton and flattened scales

What percent of fish are freshwater?

41%

What percent of fish are diadromous?

1%

What percent of fish are saltwater?

58%

Define diadromous

Fish that migrate between salt and freshwater

Define epipelagic

The uppermost layer of the ocean.

Define deep-water pelagic

unlighted open ocean

Define benthic

Ocean bottom

86% of all fish are found?

Near or on continents

20-35% of freshwater fish species are?

Extinct or declining

5% of all marine fish species are?

Extinct or declining.

What are the three species concepts?

Morphological

Biological

Evolutionary

What is taxonomy?

Describing, naming, and classification of species.

What is systematics?

Determining the relationships among species or higher taxa.

What are cladistics?

Phylogenetic systematics. (Family tree)

What are apomorphic characteristics?

Derived. Unique to a group.

What are plesiomorphic characters?

Ancestral.

What are synapomorphies?

Shared derived characteristics

What are autamorphies?

Shared derived characteristics.

What is a monophyletic group?

A group with a single common ancestor and all of its descendants.

What is a paraphyletic group?

A group with a common ancestor but not all descendants

What is a polyphyletic group?

A group that does not all share a single common ancestor.

What is anagenesis?

The amount of time and differentiation separating taxa.

What are the fossil jawless fishes?

Conodonts

Ostracoderms

What are the fossil gnathostomes?

Acanthodians

Placoderms

Fossil Chondrichthyes

Fossil Osteichthyes

When was there the most fish diversity?

The Devonian period. Approx 400 mya.

Periods of the conodonts?

Late Cambrian to late Triassic.

Ostracoderms means?

Shell skinned

Are ostracoderms a clade?

No. They’re paraphyletic.

Ostracoderm periods?

Cambrian to late Devonian.

Ostracoderms are known for their?

Endodermal bone. (Bone covering head)

Jaws evolved from?

The neural crest

Type of jaw suspension where the mandible is not supported by the hyoid arch?

Autostylic

What fish have autostylic jaws?

lungfishes

Type of jaw suspension where the mandible is supported by the hyoid arch?

Amphistylic

Type of jaw suspension where the mandible is mainly supported by the hyoid arch?

Hyostylic

What fish have hyostylic jaw support?

chondrichthyans and actinopterygians

Synapomorphies of gnathostomes?

-jaws

-Paired fins

-Skeletal bone

3 semi-circular canals

-dentine based teeth

5 classes of gnathostomes?

-Placodermi

-Chondrichthyes

-Acanthodii

-Sarcopterygii

-Actinopterygii

Where are ostracoderms found and how do they swim?

-Benthic

-Poor swimmers

Ostracoderms are a sister group to?

Gnathostomes

What is the most primitive jawed fish?

Placoderms

What was placoderm skin like?

Covered by bony plates

When are the first fossils of Chondrichthyes from?

Late Silurian

What are the 2 classes of Chondrichthyes?

-Elasmobranchs (Sharks, skates, and rays)

-Holocephalans (Ratfishes)

What are the synapomorphies of Elasmobranchs and Holocephalans?

-Cartilaginous skeleton (Limited calcification)

-Pelvic claspers

-Teeth not fused. (replaceable)

-Ceratotrichia (Unsegmented epidermal fin rays)

-Spiral valve intestines

How were early elasmobranchs different from modern elasmobranchs?

-Terminal mouths

-Multicuspid teeth

-Amphistylic jaw suspension

-Some lack claspers

-Stiffer fins

Characteristics of fossil holocephalans?

-Single opercular opening

-Autostylic jaw suspension

-Flat tooth plates that were slowly replaced

-Formerly very diverse

What are the oldest jawed vertebrates?

Acanthodians (Spiny sharks)

What is the time range of Acanthodians?

Late Ordovician to early Permian

What characters do Acanthodians share with bony fish?

-Operculum

-Branchiostegal rays

-Three otoliths

Osteichthyes (bony fish) evolved when?

Silurian but became common in the Devonian

Synapomorphies of Osteichthyes?

-Lung

-Bone

Flexible jaw

-Bony scales

-Fin rays (Lepidotrichia)

Class Sarcopterygii split off from?

Actinopterygians

Characteristics of Sarcopterygii (Lobefins)?

-Lobed fins with bony support

-Jaw suspension

-Gas bladder

-Heavy scales (Cosmoid in lungfish)

-Heterocercal tail

Three major extant lines of Sarcopterygii?

-Actinistia

-Dipnoi

-Tetrapodomorphs

What is special about Dipnoi (Lungfish)?

They have lungs and aestivation that allow them to breath air and live out of water for extended periods of time.

Tiktaalik was discovered in?

2006

Actinopterygii (Ray-finned fishes) originated when?

Late Silurian.

What are the trends in early ray finned fishes?

-Light scales

-Homocercal tail

-Branchiostegal rays

-Flexible jaws

-Flexible fins

Evolutionary trends in teleosts?

-Homocercal tail

-Reduction in bony elements (Scales and vert)

-Hydrostatic swim bladder

-Position of dorsal and paired fins

-Very flexible jaw

Plesimorphies of hagfish and lampresys?

-Body form

-No scales

-Jawless

-Primitive immune system

-Horny teeth

Characteristics of Myxini?

-3 pr barbels

-Single nostril

-No vertebrae

-70-200 slime glands

-Slime made of protein and carbs

Hagfish are caught for?

Food and “eel leather”.

Characteristics of Petromyzontida?

-Persistent notochord

-Surrounded by cartilaginous pipe

-Dorsal projections partly enclosing nerve cord

Lampreys feed in what 2 ways?

-Parasitically

-Filter feeding

Tuna tail type?

Lunate

Describe placoid scales. What types of fish have them?

-Toothlike, with enamel and dentine. Improves hydrodynamics.

-Sharks

Describe ganoid scales. Who has them?

-Platelike. Bone and ganoine.

-Ancient bony fish.

Describe cycloid scales. What fish have them?

-Smooth and overlapping

-Trout, minnows, herring.

Describe ctenoid scales. What fish have them?

-Light scales with a toothed margin for hydrodynamics.

-Spiny-rayed fishes

Describe cosmoid scales. What fish have them?

-Made of bone and cosmine

-Lungfish and coelocanths

What is the purpose of the lateral line?

Mechanoreception

What is the electrosensory organ found in sharks?

Ampullae of Lorenzini

When did Osteichthyes appear?

Silurian period

Characteristics of bony fish?

-Jaws and paired fins

-Bony skeleton

-Bony operculum covering gill arches

-Lepidotrichia

-Inner ear with 3 pairs of otoliths

General characteristics of Coelocanths?

-Large size (2m)

-Lobed fins

-Diphycercal tail

-Thick cosmoid scales

-Fat filled swim bladder