WFB 232 Ichthyology
Ichthyology – Introduction to Fishes
Vertebrate classes:
Agnatha
Chondrichthyes
Osteichthyes
Amphibia
Reptilia
Aves
Mammalia
# species
85
850
23,000
2,600
6,500
8,600
4,100
% of vertebrates
<1%
2%
> 50% of all vertebrates are fishes
50%
6%
14%
19%
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
salt lakes
0.01
groundwater
lakes
atmosphere
rivers
Total
97.11
2.2%
0.6
0.01
0.001
0.0001
2.81
Fish distribution in habitat:
freshwater
saltwater
move between (anadromous, catadromous)
41%
58%
1%
WFB 232 Ichthyology
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
WFB 232 Ichthyology
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
skeleton
paired fins
gill arches
gill arches
nostril(s)
jaws
fins with spines
pectoral fins
pelvic fins
tail
scales
mouth
Primitive
cartilaginous
absent
absent
not joined to brain case
1, median
absent
absent (trout)
horiz. base low on
body (minnows)
far back on belly (pikes)
heterocercal
cycloid (herring)
front of head (trout)
Advanced
ossified (calcified bone) - may be lost
present
present
firmly joined to brain case
paired
present
present (perches) - but may be lost (killifish)
vert. base high on body (basses)
forward, attached to pectoral girdle (sculpins)
symmetrical
ctenoid (sunfish) - absence is specialization
up- or down-turned (suckers, killifish)
WFB 232 Ichthyology
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)
WFB 232 Ichthyology
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.
WFB 232 Ichthyology
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
WFB 232 Ichthyology
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
WFB 232 Ichthyology
Orders of fishes, with selected families
Class/subclass
Myxini
Number of
Order
Families
Myxiniformes
1
Cephalaspidomorphi Petromyzontiformes
Chondrichythes
Holocephali
Elasmobranchii
Chimaeriformes
Heterodontiformes
Orectolobiformes
Carchiniformes
Lamniformes
Hexanchiformes
Squaliformes
Squantiniformes
Pristiophoriormes
Rajiiformes
Sarcopterygii
Coelocanthimorpha Coelacanthiformes
Dipnoi
Ceratodontiformes
Lepidosireniformes
Actinopterygii
Chondrostei
Polypteriformes
Acipenseriformes
Neopterygii
Semionotoformes
Amiiformes
Div. Teleostei
Representative
families
Myxinidae
Common
names
hagfish
1
Petromyzontidae
lamprey
3
1
7
7
7
2
3
1
1
9
Chimaeridae
Heterodontidae
Rhincodontidae
Cetorhinidae
Hexanchidae
Squalidae
Squantinidae
Pristiophoridae
Rajidae
chimaeras
bullhead sharks
whale sharks
ground sharks
basking sharks
cow sharks
dogfish
angel sharks
saw sharks
skates, rays
1
1
2
Latimeriidae
Ceratodontidae
Lepidosirenidae
coelacanth
1
Australian lungfish
1
S. Am., African lungfish 5
1
2
1
1
Polypteridae
Acipenseridae
Lepisosteidae
Amiidae
birchirs, reedfish
sturgeons, paddlefish
gars
bowfin
Hiodontidae
Megalopidae
Albulidae
Anguillidae
mooneye
217
tarpon
8
bonefish
29
eels
738
swallowers, gulpers
26
herrings
357
milkfish
35
carp, shiners
2,662
suckers
hatchetfish
1,343
catfish
2,405
knifefish
62
pikes
5
mudminnows
5
smelt
236
salmon, trout, ciscoes 66
whitefish, chubs
lightfish, dragonfish 321
jellynose fish
12
lizardfish
219
lanternfish
241
Osteoglossiformes
6
Elopiformes
2
Albuliformes
3
Anguilliformes
19
Saccopharyngiformes 4
Clupeiformes
4
Gonorynchiformes
4
Cypriniformes
6
Characiformes
Siluriformes
Gymnotiformes
Esociformes
10
31
6
2
Osmeriformes
Salmoniformes
13
1
Stomiiformes
Ateleopodiformes
Aulopiformes
Myctophiformes
9
1
12
2
Clupeidae
Cyprinidae
Catostomidae
Characidae
Ictaluridae
Esocidae
Umbridae
Osmeridae
Salmonidae
Ateleopodidae
# species
in order
43
41
31
8
31
208
16
5
74
12
5
456
10
26
5
1
WFB 232 Ichthyology
Lampridiformes
Polymixiiformes
Percopsiformes
Ophidiiformes
Gadiformes
Batrachoidiformes
Lophiiformes
7
1
3
4
12
17
16
Mugiliformes
1
Atheriniformes
5
Beloniformes
5
Cyprinodontiformes 13
Stephanoberyciformes 9
Beryciformes
14
Zeiformes
6
Gasterosteiformes 11
Synbranchiformes
Scorpaeniformes
Perciformes
Pleuronectiformes
Tetraodontiformes
Totals: 5 classes
57 orders
3
20
128
6
9
ribbonfish, oarfish
19
beardfish
5
trout-perch
9
cusk-eels
355
Gadidae
cod, hake
482
Batrachoididae toadfish
69
Lophidae
anglerfish
297
Ogvocephalidae batfish
Mugilidae
mullets
80
silversides, grunion 285
needlefish, flying fish 191
Cyprinodontidae livebearers
807
Poeciliidae
guppies
whalefish
86
squirrelfishes
123
John Dories
39
Gasterosteidae
sticklebacks
257
Pegasidae
seamoths
Syngnathidae
pipefish, seahorses
Indostomidae
I. paradoxus
Synbranchidae
swamp eels
87
Cottidae
scorpionfish, sculpin1,271
Dactylopteridae flying gunards
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)
Pleuronectidae
flounder, flatfishes 570
Balistidae
triggerfishes
339
Ostraciidae
cowfish, boxfish
Tetraodontidae puffers
Molidae
molas (ocean sunfish)
Polymixiidae
Percopsidae
478 families
~26,000 species
WFB 232 Ichthyology
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
whale
tuna
copepod
sea urchin sperm
speed
10 m/s
10 m/s
20 cm/s
0.2 mm/s
Re
300,000,000
30,000,000
300
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
WFB 232 Ichthyology
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