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icthyology > introduction > Flashcards

introduction Flashcards

1
Q

3 major groups of living fish

A

cyclostomes, chrondichthyes, Osteichthyes

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2
Q

Cyclostomes

A

Jawless fish
Myxini (hagfishes) ~ 70 species
NO: vertebrae, paired fins,
jaws, or scales
Petromyzontida (lampreys) ~ 38 spp
have simple vertebrae
no jaws, paired fins, scales

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3
Q

Chondrichthyes

A

(cartilaginous fishes) ~ 1000 spp
* Elasmobranchii
– Sharks (403)
– Skates & rays (534)
* Holocephali (chimaeras) (33)
– OWN the top predator niche

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4
Q

Osteichthyes

A

(bony fishes) ~ 34,000 + spp
* Sarcopterygii (lobe-finned fishes) (8)
* Actinopterygii (ray-finned fishes) (34,000 +)

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5
Q

where are fish found

A

41% freshwater – why so many?
* 1% diadromous
* 58% saltwater
– 44% in shallow water near continents
– 1% lighted open ocean (epipelagic)
– 5% unlighted open ocean (deepwater pelagic)
– 7% ocean bottom (deepwater benthic)
* Highest diversity in the tropics

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6
Q

conservation

A

Note that ~ 86% of all fish species are found
on or near continents
– Potential for human impacts
* Freshwater fishes: 20-35% extinct or declining
– 35% of 1000 North American species
* Marine fishes: ~ 5% extinct or declining (est)
– most exploited species overfished
– ecological/economic extinction

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7
Q

Systematics

A

Basis of any taxonomic discipline
* Classification system of hierarchically
arranged names
– Reflects current evolutionary hypotheses about
relationships among taxa
– Can (and do) change as we learn more
* Natural classification
– Based on evolutionary relationships
– Allows predictions based on group membership
* Example: Family Centrarchidae

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8
Q

taxonomy

A

Describing, naming, arranging into system of
classification, devising ID keys

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9
Q

Systematics

A

Focuses on determining relationships among
species or higher taxa

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10
Q

Approaches to classification

A

Cladistics (phylogenetic systematics)
– Basis of modern systematics (Hennig, 1950)
– Two types of characters:
* apomorphies (derived)
* plesiomorphies (ancestral)
– synapomorphies – shared derived characters
– autapomorphies – define single taxa

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11
Q

Common body forms

A

Elongate, moderate, deep, rounded, compressed slightly, compressed strongly, depressed deeply

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12
Q

Morphology: caudal fin types

A

A. heterocercal – vertebral column extends into
upper lobe (sharks, sturgeon)
B. protocercal – undifferentiated (lampreys, eels)
C. homocercal – most bony fishes
– Forked, rounded, truncate, lunate, etc.
D. diphycercal – lungfish, coelocanth

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13
Q

Inferring ecology from morphology

A
  • rover-predator
  • lie-in-wait (fast-start) predator
  • surface-oriented fish
  • bottom rover
  • bottom clinger
  • deep-bodied fish
  • eel-like fish
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14
Q

Fish locomotion: using fins

A
  • oscillation of pectoral fins
    – wrasses, surfperch, most deep-bodied fishes
    at times
  • oscillation of median fins (eg, dorsal
    and anal)
    – ocean sunfish, porcupinefish
  • undulation of pectoral fins
    – skates and rays
  • undulation of dorsal or anal fins
    – bowfin, knifefishes
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15
Q

mouth

A

inferior, subterminal, terminal, supraterminal, superior

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16
Q

scale types

A

placoid – toothlike, with enamel
& dentine layers
– Chondrichthyes
– rough surface improves
hydrodynamics
– origin of chondrichthyan (& all
vertebrate) teeth
* cosmoid – bone & cosmine
– lungfishes & coelocanths
– from fusion of placoid scales
– highly modified in recent
lungfishes
ganoid – bone & ganoine
– platelike, non-overlapping
– Articulate with ball-and-socket
joint
– Found in primitive
actinopterygians (bowfin,
gars, paddlefish, sturgeons)
cycloid
– Trout, minnows, herring
– smooth margin
* ctenoid
– spiny-finned teleosts
– toothed margin improves
hydrodynamics

17
Q

conodonts

A

Class Conodonta
* late-Cambrian to late
Triassic
– earlier “protoconodonts”
not chordates
* abundant tooth-like
fossils
– ‘conodont elements’
– biostratigraphy
* soft body not found
until 1980s

18
Q

Ostracoderms

A

= “shell-skinned”
* not a clade! Paraphyletic …
* late Cambrian to late Devonian
* bony shield over head/thorax - endodermal bone
* small (to ~ 30cm)
* many with hypocercal tail
– reverse heterocercal
* Four distinct superclasses
– Pteraspidomorphi
– Anaspidomorphi
– Theolodonti
– Osteostracomorphi
* likely sister taxon to jawed vertebrates
* generally benthic, poor swimmers
* likely deposit feeders, but w/ muscular feeding pump
* a few deep-bodied forms (C) used water column

19
Q

Types of jaw suspension

A
  • Autostylic – mandible not
    supported by hyoid arch
    – lungfishes, tetrapods,
    (holocephalans)
  • Amphistylic – mandible
    partly supported by hyoid
    arch
    – primitive sharks
  • Hyostylic – mandible mainly
    supported by hyoid arch
  • most chondrichthians
    and all actinopterygians
20
Q

Placoderms

A
  • presumed most primitive jawed fishes
  • possible ancestor to chondrichthyans
  • BUT, appear later in fossil record than
    Acanthodians
  • late Silurian – early Carboniferous
    – ecological replacement by Chondrichthyes?
    “plate-skinned”
  • ornamented, bony plates over anterior body
  • diverse and successful!
    – 25-30 families
    – 200 genera
  • d/v compressed
    – benthic
  • some very large
    – Dunkleosteus to 6m
21
Q

Acanthodians

A

Acanthodians – “spiny sharks”
* oldest jawed vertebrates – before Placoderms
– late Ordovician to early Permian
* NOT closely related to sharks
* now considered the earliest bony fishes
* share with bony fishes:
– operculum
– branchiostegal rays
– three otoliths
* stout median and paired spines
* multiple paired fins in some (fin-fold theory?)
* mostly small (20cm to 2.5m)
* streamlined – water column feeders
* diverse: 9 families, ~ 60 genera

22
Q

SC Holocephali

A
  • upper jaw fused to cranium
    – autostylic suspension
    – (holostylic – a version of
    autostylic)
  • teeth as continual growing
    plates
    – anterior bladelike, rear
    crushing
  • operculum covers 4 gill slits
  • separate anal & urogenital
    openings
  • tenaculae
  • mostly scaleless
  • long pointed tail
  • oviparous, few eggs, long development
  • adult size 60-200 cm
  • benthic, moderate depths (80-2600m)
  • main food = hard-shelled inverts
  • swimming
    – body undulations
    – pectoral fin flapping
23
Q

Osteichthyes

A
  • appeared 425 mya during the Silurian
  • probably evolved initially in freshwater
  • dominant by 380 mya (mid-Devonian)
  • Ostracoderms had just died out
  • Acanthodians, placoderms, elasmobranchs
    were radiating at the same time
    – so origins of bony fishes unclear
24
Q

coelacanth

A
  • large size (to 2m L)
  • lobed fins (which?)
  • diphycercal tail
  • scales – thick, bony, ± cosmoid
  • hollow spines (coel – acanth)
  • gular plate
  • occipital joint
  • autostylic jaw suspension
  • fat-filled swim bladder
  • spiral valve intestine
  • osmoregulation – concentrate urea
  • nocturnal
  • moderately deep
    – 100-400m
  • congregate in caves
    in daytime
    – possible limiting
    factor
  • feed drifting, in
    ‘head-down’ position
25
Q

dip-noan

A

double breather

26
Q

Polypteriformes

A

shared characteristics
* gular plates
* spiracles
* autostyly
* ganoid scales
* external gills when young
* modified heterocercal tail
* spiral valve intestine
autapomorphies
* fin structure
– paired
– median
* respiration
– exhale thru spiracles
– recoil aspiration
* only 4 gill arches

27
Q

SC Chondrostei, Order Acipenseriformes

A

Sturgeons and paddlefishes

28
Q

Acipenseriformes-characteristics

A
  • cartilaginous skeleton
  • heterocercal tail
  • reduced squamation
  • jaw suspension similar to sharks
  • no branchiostegal rays
  • electrosensory organs
  • single dorsal fin far back on body
  • large and long-lived
    – to 118 y (Beluga)
  • 4 barbels
  • 5 rows of
    bony scutes
29
Q

Order Lepisosteiformes

A
  • backwater areas of lakes
    & rivers—low O2
    – facultative air breathers
  • Characteristics
    – elongate cylindrical bodies
    – ganoid scales
    – median fins set far back …
    – swimbladder/lung
    – spiral valve intestine
    – opisthocoelous vertebrae
    – ossified skeleton
    – tail moderately
    heterocercal
30
Q

Teleost diversity

A
  • 96% of all fishes, most fisheries
  • Diversity of habitats/niches, esp vs
    – chondrichthyans
    – relict bony fishes
  • Four major groups (subdivisions) of teleosts:
    – Elopomorpha (true eels, tarpons)
    – Osteoglossomorpha (mooneyes, bonytongues, etc)
    – Otocephala (clupeids, minnows, catfishes)
    – Euteleostei (all the rest!)
31
Q

Teleosts: defining characteristics

A
  • uroneural bones support the fully homocercal tail
  • mobile maxilla & premaxilla, allowing upper jaw protrusion
  • cycloid / ctenoid scales
  • operculum with 4 bones
32
Q

Teleosts: trends in evolution

A
  • lighter weight bone and scales
  • more efficient 2-pump respiratory system
  • gas bladder more specialized as hydrostatic
    organ (rather than lung)
  • separation of biting and chewing function of
    jaw, using pharyngeal teeth to chew
  • fully homocercal tail
  • location of paired fins shifts, particularly in the
    more advanced teleosts
33
Q

Superorder Ostariophysi

A
  • 68% of all freshwater fish species
  • Defining characters:
    – Weberian apparatus
  • lacking in milkfishes (most primitive order)
    – alarm substance (shreckstoff) & alarm response
34
Q

Percomorph fishes - Characters

A
  • pelvic fins far forward, or lost
  • pectoral fins high on body
  • fin spines (sometimes reduced)
  • very flexible skull and jaw
  • upper & lower pharyngeal teeth
  • physoclistous swimbladder, or none
  • pelvic fins usually: 1 spine, 5 rays
  • spine usually w/ 24 vertebrae
  • small spines on head and operculum (usually)
  • well-developed eyes
  • ctenoid scales (usually)
35
Q

Order Perciformes

A
  • largest order of vertebrates,
    19 suborders, 160 families,
    ~13,000 spp
  • nearly half of all fishes!
  • most occupy richest
    habitats:
    – shallow, lighted surface
    waters of oceans & lakes
    – dominant spp of coral reefs
    Characters (percimorph plus)
  • 2 dorsal fins: 1 spinous, 1
    soft-rayed, often joined;
    never an adipose fin
  • absence of certain bones,
    including epipleurals
36
Q

Devonian

A

age of fish 408 mya
contains hagfishes, lampreys, conodonts, ostracoderms, Placoderms, Elasmobranches, Holocephali, Acanthodians, Actinopterygians, Sarcopterygians.
during Paleozoic era

icthyology (2 decks)

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