WFB 232 Ichthyology
Ichthyology – Introduction to Fishes
Vertebrate classes: # species % of vertebrates
Agnatha 85 <1%
Chondrichthyes 850 2% > 50% of all vertebrates are fishes
Osteichthyes 23,000 50%
Amphibia 2,600 6%
Reptilia 6,500 14%
Aves 8,600 19%
Mammalia 4,100 9%
physiological and sensory modalities in fish that are not present in other taxa
osmoregulation
buoyancy control
respiration (air and water)
mechanosensory – lateral line
electroreception
electric generation
light production
Characteristics and constraints of the aquatic environment
salinity - must deal constantly with osmoregulation - into or out of body
temperature - water has high thermal capacity, 4x that of air
motion - from still water, with little oxygen exchange, to torrential currents
gas saturation - water contains (relative to air) very little oxygen; methods for withdrawal must be specialized;
too little, fish must achieve oxygen elsewhere; too much results in gas bubble diseases
pressure - increases 1 atm for every 33’ of depth (= 10 m)
consequence for buoyancy and gas bladders
few fish are neutrally buoyant – use air or fat to compensate
fish need much less skeletal support than terrestrial animals, due to support surrounding body
viscosity - much higher effort required to swim in water than air
fastest swimming speed (tuna) - 21m/s in short bursts; killer whale does 15m/s
little effort required to prevent sinking
light - attenuates rapidly with depth; thus deep-sea fish may create own light
sound - propagates rapidly in water (400x as well as in air)
provides medium of communication by vibration, but with little directionality
Distribution of aquatic habitats
Salt water Fresh water
oceans 97.10% ice, snow 2.2%
salt lakes 0.01 groundwater 0.6
lakes 0.01
atmosphere 0.001
rivers 0.0001
Total 97.11 2.81
Fish distribution in habitat:
freshwater 41%
saltwater 58%
move between (anadromous, catadromous) 1%
Taxonomy
Objectives:
Learn how species are defined and named; understand how taxonomic nomenclature is used
Begin to know the classes, orders, and representative families and species in each order of fishes
Learn to ‘read’ taxonomic descriptions
Recognize primitive (older) versus advanced (recent) traits in fishes
Classification = hierarchical grouping of organisms (i.e. a process, an operation)
Systematics = the study of relationships
Taxonomy = the science of biological nomenclature (formal rules for use)
Taxonomic hierarchy: (note standardized endings)
Phylum: Chordata
Subphylum: Vertebrata
Superclass: Gnathostomata
Class: Actinopterygii (formerly Osteichthyes)
Order: Cypriniformes
Suborder: Cyprinoides
Family: Cyprinidae
Subfamily: Cyprininae
Genus: Cyprinus
Species: carpio
standardized endings (well-established in ichthyology)
Order: -formes
Suborder: -oides
Family: -idae
Subfamily: -inae
Tribe: -ini
Only genus and species are underlined or italicized with only the generic term capitalized.
phylogenetic systematics – objective is to make the classifications non-arbitrary, and informative about evolutionary relationships
cladograms: each branch represents monophyletic group - all from common ancestor
if polyphyletic, then subsequent categories based on false assumption
all members share one or more derived characters
problem is to determine whether a given character is homologous or convergent
plesiomorphies – primitive character states
apomorphies – advanced character states
autoapomorphies – specialization unique to one taxon
synapomorphies – shared specializations
Taxonomic relationships defined on the basis of
morphometrics - usually measurements as ratio against SL, to account for absolute size
meristics - counts, with ranges - may vary with environment
anatomical traits - shape, presence/absence of structures
color patterns - highly variable, change with maturity, subjective, fade in preservative
karyotypes - changes in number and shape of chromosomes
biochemical methods - look directly at genetic material
Authorship of scientific names
In original genus: Amia calva Linnaeus – usually followed by date
In new genus: Lepisosteus osseus (Linnaeus)
right of priority – given to first full written description, usually with type specimen from a type locality
the description makes it a nominal species
original species name must not be changed, even if genus is changed
- unless previously used for another animal (nomen praeoccupatum)
- if previously described, later description becomes junior synonym
hybrids denoted with an x - Rutilus rutilus x Abramis brama
Nomenclature (International Code of Zoological Nomenclature)
pronounciation:
ch = k (e.g., ichthyology) – there is no ‘k’ in Latin
initial c = s (e.g., Cyprinidae)
genus and species always italicized; genus is always capitalized, species name is not capitalized
Neogobius melanostomus
genus and subspecies can be abbreviated after they have been mentioned once in a text
N. melanostomus
N. m. caspia
subgenus is usually in parentheses
Dreissena (Pontodreissena) polymorpha
Characteristics of the classes of extant fishes
Character Primitive Advanced
skeleton cartilaginous ossified (calcified bone) - may be lost
paired fins absent present
gill arches absent present
gill arches not joined to brain case firmly joined to brain case
nostril(s) 1, median paired
jaws absent present
fins with spines absent (trout) present (perches) - but may be lost (killifish)
pectoral fins horiz. base low on vert. base high on body (basses)
body (minnows)
pelvic fins far back on belly (pikes) forward, attached to pectoral girdle (sculpins)
tail heterocercal symmetrical
scales cycloid (herring) ctenoid (sunfish) - absence is specialization
mouth front of head (trout) up- or down-turned (suckers, killifish)
Taxonomy of Fishes
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
SUPERCLASS AGNATHA
Class Myxini
Order Myxiniformes (hagfishes)
Class Cephalaspidomorphi
Order Petromyzontiformes (lamprey)
SUPERCLASS GNATHOSTOMATA
Class (Placodermi)
Class (Acanthodii)
Class Chondrichthyes
Subclass Holocephali
Order Chimaeriformes (chimaeras)
Subclass Elasmobranchii
9 orders (sharks, rays, skates)
Class Sarcopterygii
Subclass Coelacanthimorpha
Order Coelacanthiformes (coelacanths)
Subclass Dipnoi
Order Ceratodontiformes (Australian lungfish)
Order Lepidosireniformes (S. American, African lungfish)
Class Actinopterygii - (rayfins, higher bony fishes)
Subclass Chondrostei
Order Polypteriformes (birchirs, reedfish)
Order Acipenseriformes (sturgeons, paddlefishes)
Subclass Neopterygii
Order Semionotoformes (Lepisosteiformes) (gars)
Order Amiiformes (bowfin)
Division Teleostei
35-38 orders (modern body fishes)
Example of a taxonomic description (adapted from Berg, 1949)
Round goby, Neogobius melanostomus (Pallas, 1811). D1 VI (V‑VII); D2 I + 14‑16 (13‑16); A I + 11‑13 (11‑14); P 18‑19 (17‑20). [ = the anterior dorsal fin has 5‑7 spines, usually 6, and the posterior dorsal fin has one spine and 13‑16 soft rays. The anal fin has one spine and 11‑14 soft rays, and the pectoral fins have 17‑20 soft rays.] Scaled on the parietal region, nape, back (all), throat (all or most), abdomen, pectoral fin peduncles, and one quarter of the gill covers. Scales on the middle and anterior nape are cycloid. Head is as wide as or wider than deep; depth is 0.9‑1.2 times the width. Head length 4.2‑4.5 of total body length. Angle of the jaw below the anterior quarter of the eye. Lower jaw not prominent. Snout 1.1‑1.4 times the orbit diameter. Upper lip narrows slightly to the rear. Usually 6, rarely 7, transverse suborbital series of pit organs. Ventral fins reach or almost reach the vent. Pelvic disk is 0.6‑0.8 times the abdomen length. If present, the anterior membrane width is very shallow, with rounded, lateral lobes. Caudal peduncle depth is about two‑thirds its length. Lacks a gas bladder and chemoreceptors.
Fish Anatomy
Objectives: become acquainted with the general external and internal structures of fishes, and how they vary functionally and taxonomically
become familiar with parts of fish and associated terminology
learn to recognize fishes by similarities and differences in structure
External anatomy
Head
mouth
mouth position – superior, terminal, sub-terminal, inferior
teeth types and locations;
mostly on mandible (lower jaw), premaxilla and maxilla (upper jaw) – Bond Fig. 2-20
generally protrusible in derived bony fishes
frenum - bridge of skin binding lips to snout or chin in non-protrusible jaw
additional (or seasonal) structures include barbels, tubercules, kype, cirri
sensory pores
nares
Body shapes – which taxa have each, what are the advantages of each type?
fusiform
sagittaform
anguilliform
compressiform
depressiform
filiform
Fins – what are each used for? how does their presence or location vary among taxa?
paired fins: pelvic – some modified to disk (gobies) or claspers (sharks)
placement may be abdominal, subabdominal, jugular, mental (under chin)
pectoral
single fins: dorsal - one or two; rarely three; may be modified to disk
(medial) anal – may be modified to intromittent organ (gonopodium)
caudal – rounded, lobed, truncate, emarginated, forked; homocercal or heterocercal
adipose – in only a few orders
peduncles (base of fin or tail where they attach to body)
supporting structures:
ceratotrichia – cartilaginous elements in elasmobranch fins
lepidotrichia – rays (double, segmented elements) sometimes modified to spines (ossified, single)
Skin and scales – which are more advanced, or primitive?
presence, absence, or partial covering of scales
functions of scales
types of scales: placoid, ganoid, cycloid, ctenoid, scutes
skin pigmentation: melanophores
Internal anatomy
Internal organs
GI tract (stomach, intestine, pyloric caecae), reproductive organs, kidneys, liver, gall bladder, spleen
gas bladder may be present or absent, connected or not to other organs
physoclistous – closed gas bladder
physostomus – gas bladder has open connected to esophagus
Body musculature
hypaxial muscles
epaxial muscles
myomeres
Osteology
Skull
premaxilla, maxilla, dentary, palatine may all have teeth attached
operculum: opercle, subopercle, preopercle, interopercle
otoliths – ear bones
branchial arches - usually 5 pairs - bear gill rakers on inner surface
fifth arch may be modified to pharyngeal teeth
breathing apparatus (see diagrams in Bond)
Vertebral column
Vertebrae composed of centrum, with neural spine, neural arch, neural canal
zygopophysis, basapophysis – small locking projections add rigidity, connection with ribs
hemal spine, hemal arch (only near tail), hemal canal
dorsal ribs, or epipleurals, project from pleurals
Caudal skeleton
urostyle – last vertebra, modified into plate
hypurals - modified from hemal arch, connected to end of vertebral column and caudal elements
epurals – remnant from hemal spine, one or more free bones above hypurals
Appendicular skeleton
pterygiophores articulate with fin rays
pectoral girdle – cleithrum, scapula, coracoid bones
pelvic girdle – simple system to support fins
Orders of fishes, with selected families
Number of Representative Common # species
Class/subclass Order Families families names in order
Myxini Myxiniformes 1 Myxinidae hagfish 43
Cephalaspidomorphi Petromyzontiformes 1 Petromyzontidae lamprey 41
Chondrichythes
Holocephali Chimaeriformes 3 Chimaeridae chimaeras 31
Elasmobranchii Heterodontiformes 1 Heterodontidae bullhead sharks 8
Orectolobiformes 7 Rhincodontidae whale sharks 31
Carchiniformes 7 ground sharks 208
Lamniformes 7 Cetorhinidae basking sharks 16
Hexanchiformes 2 Hexanchidae cow sharks 5
Squaliformes 3 Squalidae dogfish 74
Squantiniformes 1 Squantinidae angel sharks 12
Pristiophoriormes 1 Pristiophoridae saw sharks 5
Rajiiformes 9 Rajidae skates, rays 456
Sarcopterygii
Coelocanthimorpha Coelacanthiformes 1 Latimeriidae coelacanth 1
Dipnoi Ceratodontiformes 1 Ceratodontidae Australian lungfish 1
Lepidosireniformes 2 Lepidosirenidae S. Am., African lungfish 5
Actinopterygii
Chondrostei Polypteriformes 1 Polypteridae birchirs, reedfish 10
Acipenseriformes 2 Acipenseridae sturgeons, paddlefish 26
Neopterygii Semionotoformes 1 Lepisosteidae gars 5
Amiiformes 1 Amiidae bowfin 1
Div. Teleostei Osteoglossiformes 6 Hiodontidae mooneye 217
Elopiformes 2 Megalopidae tarpon 8
Albuliformes 3 Albulidae bonefish 29
Anguilliformes 19 Anguillidae eels 738
Saccopharyngiformes 4 swallowers, gulpers 26
Clupeiformes 4 Clupeidae herrings 357
Gonorynchiformes 4 milkfish 35
Cypriniformes 6 Cyprinidae carp, shiners 2,662
Catostomidae suckers
Characiformes 10 Characidae hatchetfish 1,343
Siluriformes 31 Ictaluridae catfish 2,405
Gymnotiformes 6 knifefish 62
Esociformes 2 Esocidae pikes 5
Umbridae mudminnows 5
Osmeriformes 13 Osmeridae smelt 236
Salmoniformes 1 Salmonidae salmon, trout, ciscoes 66
whitefish, chubs
Stomiiformes 9 lightfish, dragonfish 321
Ateleopodiformes 1 Ateleopodidae jellynose fish 12
Aulopiformes 12 lizardfish 219
Myctophiformes 2 lanternfish 241
Lampridiformes 7 ribbonfish, oarfish 19
Polymixiiformes 1 Polymixiidae beardfish 5
Percopsiformes 3 Percopsidae trout-perch 9
Ophidiiformes 4 cusk-eels 355
Gadiformes 12 Gadidae cod, hake 482
Batrachoidiformes 17 Batrachoididae toadfish 69
Lophiiformes 16 Lophidae anglerfish 297
Ogvocephalidae batfish
Mugiliformes 1 Mugilidae mullets 80
Atheriniformes 5 silversides, grunion 285
Beloniformes 5 needlefish, flying fish 191
Cyprinodontiformes 13 Cyprinodontidae livebearers 807
Poeciliidae guppies
Stephanoberyciformes 9 whalefish 86
Beryciformes 14 squirrelfishes 123
Zeiformes 6 John Dories 39
Gasterosteiformes 11 Gasterosteidae sticklebacks 257
Pegasidae seamoths
Syngnathidae pipefish, seahorses
Indostomidae I. paradoxus
Synbranchiformes 3 Synbranchidae swamp eels 87
Scorpaeniformes 20 Cottidae scorpionfish, sculpin 1,271
Dactylopteridae flying gunards
Perciformes 128 Percichthyidae temperate bass 9,293
Centrarchidae sunfish
Percidae perch, bass
Sciaenidae drum
Mullidae goatfishes
Cichlidae cichlids
Mugilidae mullets
Gobiidae gobies
(also: bluefishes, remoras, blennies, mackerels,
dolphins, snappers, tunas, swordfish)
Pleuronectiformes 6 Pleuronectidae flounder, flatfishes 570
Tetraodontiformes 9 Balistidae triggerfishes 339
Ostraciidae cowfish, boxfish
Tetraodontidae puffers
Molidae molas (ocean sunfish)
Totals: 5 classes 57 orders 478 families ~26,000 species
Swimming
Objectives
Understand the physical characteristics of water that affect the ability to swim
Understand the various modes of fish propulsion, factors that affect their efficiency, and representative species that use them
physical properties of water
density – 830 x more than air
viscosity – 70 x more than air
boundary layer
turbulence
Reynolds number (Re) (dimensionless variable)
Re = LVr/m
L = length of object
V = velocity of object
r = density of fluid
m = viscosity of fluid
Examples of Re:
animal speed Re
whale 10 m/s 300,000,000
tuna 10 m/s 30,000,000
copepod 20 cm/s 300
sea urchin sperm 0.2 mm/s 0.03
unavoidable issues when swimming:
flow changes to turbulent at Re ~ 2,000
boundary layer changes to turbulent as Re goes from 5x105-5x106
turbulent flow is a consequence of
decreasing viscosity
increasing density of liquid
increasing speed
increasing length
for efficient swimming
avoid separation of boundary layer from surface
maximize laminar flow in boundary layer
minimize turbulent flow in wake
solutions:
streamline body (tapering)
aspect ratio of about 0.25
max. thickness of body 1/3 back
drag reduction - keep body rigid
slime layer to reduce frictional drag
rough surface (cteni) keeps boundary layer attached
Swimming modes
“kick and glide”
active - sustained for hours or days
burst - only for up to 30 secs
large fishes have greater difference between burst and active than small fishes
active swimming accomplished using red muscle along sides of fish
- high myoglobin and mitochondrial enzymes
burst swimming with white muscle
- great contractile speeds, low endurance
Body/caudal fin propulsion
Medial/paired fin propulsion
non-swimming locomotion
burrowing
wriggling
‘walking’
push-and-hold
walking on bottom vics
leaping
gliding
hitchhiking
passive drift
jet propulsion