Transcript Subphylum Vertebrata – Early Vertebrates and

Bony Fishes – Diversity and Taxonomy
 Clade Osteichthyes: fishes exhibiting ossified skeletons (bone replaces
cartilage during development), swim bladders (or lungs), and shared
cranial and dental features; most with homocercal tails
 Class Actinopterygii: the ray-finned fishes (most diverse of vertebrates, ~27,000
species); earliest forms include paleoniscids (Paleozoic)
 Bichirs: possess lungs, heavy ganoid scales; found in Africa (freshwater)
 Sturgeons and Paddlefishes: freshwater and anadromous species; large bodied; source of
caviar (many species endangered as a result of overfishing)
 Gars and Bowfin (early neopterygians): found in the Great Lakes and the Mississippi River
basin; gars piscivorous
 Teleosts: modern bony fishes (~96% of fishes); light, flexible scales (cycloid or ctenoid);
adaptations of fins (rays and spines) and swim bladder increased maneuverability;
adaptations of lower jaw suspension allowed rapid jaw protrusion (allows suction feeding);
extra set of jaws (pharyngeal jaws) in some taxa used for crushing shells
 Class Sarcopterygii: the lobe-finned fishes
 Early Forms: all had lungs and gills; including rhipidistians (freshwater and coastal
taxa with fleshy fins; most diverse in late Paleozoic; gave rise to early tetrapods)
 Lungfishes: six extant species (African and South American species able to survive
through dry seasons in mud beds); functional lungs
 Coelacanths: peak diversity in Mesozoic; one extant genus (Latimeria) discovered off
South Africa (1938) and Comoro Islands, and then Sulawesi, Indonesia (1998);
diphycercal tail; deep sea habitat; largest eggs of a fish (9 cm diameter)
Fig. 24.1
Fig. 24.2
Fig. 24.18 and 24.19
Fig. 24.20
Fig. 24.22 and Fig. 24.23
Bony Fishes – Form and Function
 Calcified bones: including operculum (covers gills), otoliths (ear bones that control
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balance; fish can get sea sick!), and fin rays (allow maneuverability)
Teleosts with fin spines (anti-predation); many with modifications of fins (esca of
anglerfishes, suckers, venomous spines, membranous fins of flying fish)
Swim bladder: gas-filled sac for buoyancy control; some fill via bloodstream (but
only slowly; limited depth ranges), others adjust via mouth and must live
near surface (ex. anchovies); some lack or is vestigial (tunas, flatfishes);
good target for echolocation; stores gases and can function as a lung;
sound production (ex. croakers); Weberian ossciles increase hearing ability
Multiple gills: gill rakers trap prey; gas exchange at gill filaments (thin and full of
blood capillaries); gills accomplish excretion along with kidneys
Flattened, flexible scales (cycloid or ctenoid)
Locomotion: anguilliform (body undulation, ex. eels); carangiform and thunniform
(trunk musculature, ex. jacks, tunas); fin-movements (ex. boxfish)
Body forms: Fusiform (torpedo shaped; tunas, etc.); Laterally compressed (flatfishes, butterflyfishes, etc.); Snake-like (eels); Globular (benthic groups);
Tubular (ex. trunkfish)
Reproduction: sexual dimorphism, sex reversal, and hermaphrodites common
(ex: wrasses, groupers); some monogamous (butterflyfishes); most with
pelagic, planktonic larval stages; some brood benthic eggs and larvae (ex.
damselfishes); some with live birth (ex. surfperches, seahorses – males
with pouch)
Fig. 29.8
Fig. 24.15
Fig. 24.27
and
Fig. 24.28
Fig. 24.29
Fig. 31.20
Fig. 24.30
Fig. 24.16
Fig. 24.17
Fig. 24.24
Fig. 24.25
Fig. 24.35
Bony Fishes – Feeding and Evolutionary Ecology
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Feeding modes: filter feeders (ex. anchovies), grazers (ex. surgeonfishes), suction-feeding planktivores (ex. many damselfishes),
piscivores (ex. groupers, tunas), crushers (ex. most wrasses);
most parrotfishes ingest coral and digest zooxanthellae; goatfishes detect prey in sediment with barbels; most butterflyfishes
ingest coral polyps; winnowing (ex. surfperches)
Evolutionary Ecology
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Tunas and billfishes: very fast, powerful (cross entire oceans); red muscle for
endurance (high in oxygen and myoglobin); counter-current heat
exchange, rete-mirabile allow endothermy (warm-blooded: 2-10° C
above ambient); high predation rates and high metabolism; bills for
predation (marlin dangerous!)
Deep-sea fishes: adapted for life with little food; lack muscle; counterillumination: photophores on ventral surface to match downwelling light
Coloration and Mimicry: color patterns involve countershading, cryptic
coloration, warning coloration, species recognition (poster coloration),
disruptive coloration, mimicry (incl. aggressive mimicry)
Fig. 24.26
Bony Fishes – Schooling, Migrations, and Fisheries
 Schooling behavior: grouping with biosocial attraction (vs. simple
aggregation)
 Coordination with nearest neighbors largely mediated via lateral-line sense
(experiments with blinds, glues, nerve oblation, etc.)
 Reduces predation via confusion effect and reduction of predator/prey
encounters
 Other functions? Note salmon homing theory (incr. success?)
 Migrations
 American and European eels: spawn in Sargasso Sea (catadromous)
 Salmon (anadromous): adults in ocean; migrate from river mouth to natal
streams via olfaction (imprinting); from ocean to river mouth via suncompass, magnetic cues?
 Diurnal migrations: ex. blacksmith (note ecological importance)
 Fisheries and Aquaculture
 Fish an important source of protein; human population now ~7 billion; over-
fishing a result of increased fishing technology; size-limits and quotas less
effective than reserves (allow fish a chance for reproduction); people eating
fish from lower trophic levels & under-utilized species (ex. deep-sea forms)
 Aquaculture: successful farms include tilapia, salmon, shrimp, and lobster; later
eat fish meal (contribute to overfishing); coastal wetlands used/spoiled
Fig. 33.22
Fig. 24.33
 Fig. 24.37
Fig. 24.34
Fig. 24.38