Marine vertebrates 2

cyclostome synapomorphies

single medial nostril, gills supported by unarticulated skeletal elements, velum, keratinous teeth

myxiniformes (hagfish) anatomy

no paired fins, barbels and external gill opening, reduced eyes and lateral line

myxiniformes physiology

isosmotic to surrounding water, excrete ions via slime, have pronephric filtration (embryonic state in vertebrates) making them bad at it

myxiniformes ecology

75 extant species, found more than 50m down in burrows north and south of 30 degree latitudes, tie themselves in a knot to tear food off, oviparous

Petromyzontiformes anatomy

0.1-1.0m in length, buccal funnel, we;; developed eyes, discrete gill openings, branchial basket supporting branchial pouches, large piston cartilage near mouth for feeding

Petromyzontiformes breeding

anadromous, semelparous, produce thousands of eggs deposited in rock nests in rivers, larvae burrow into substrate and filter feed for 3-7 years, then go to ocean and are parasitic for 12-18 months and gain weight, then come back to spawn and die

semelparous

only breed once in their lifetime

anadromous

start in freshwater, go to sea to grow and mature, come back to freshwater to breed

Evolution of jaws

in the Silurian (443 mya) placoderms appear, have dermal bone plates on anterior end, ranged from small benthic scavengers to large pelagic predators, early species were marine 

Placoderms

paired appendages, epaxial and hypaxial regions (dorsal and ventral muscle patterning), claspers indicating internal fertilization, some had tooth bearing plates around jaws

Paired fins and maneuverability

introduce roll (literally roll over), yaw (moving right or left like a radar), and pitch (closer to surface or deeper down)

Gnathostomes

dermal skull bone is homologous to exoskeleton of placoderms, first two gill arches become pre-mandibular and contribute to brain case, second becomes hyoid arch, 3-7 are branchial arches

Chondrichthyan subclasses

holocephalii (ex. ratfish)

elasmobranchs — batoids and selachians (ex. cownose rays, black tip shark)

Chondrichthyes synapomorphies

placoid scales (dermal denticles), cartilaginous skeleton with prismatic calcification, polyphyodont dentition, pelvic claspers, ceratotrichia in fins (keratin and collagen)

Amphistylic

upper jaw is very closely associated with braincase but not fused

holostylic

lower jaw articulates directly with the braincase, upper jaw is fused to braincase, hyoid arch is independent, have tooth plates rather than teeth

Hyostylic

upper jaw is attached to braincase via a ligament but articulates via hyomandibula and ceratohyal

selachians have long ceratohyal and hyomandibula for jaw protrusion during feeding

batoids have jaws pointing downward, reduced ceratohyal with hyomandibula pushing jaw down

Holocephalan anatomy

holostylic, secondary loss of most placoid scales, prominent dorsal fin spine, fleshy operculum, frontal tenaculum (on forehead to grip to pectoral fin), claspers are bifurcate

Chondrichthyan prey sensing

cues in order of distance: odor plume, turbulence (wake), vision (looking at), sound, electrical fields, contact

olfaction - detecting, mechanoreception via lateral line - tracking, vision - orienting for attack, electroreception/mechanoreception - attacking

Light in sharks

lantern sharks are bioluminescent, some catsharks are biofluorescent

Shark modes of reproduction

placental viviparity, ovoviviparity, oviparity

squalus acanthias has two year gestation period, one year in egg in uterus, one year swimming inside still attached to yolk sac

highly K-selected clade — long recovery time after population decline

Gill nets

buoys suspend a large rectangle of net in the water column, gets caught in the gills of fish, dangerous for ram ventilators and coastal species as commercial fleets will cut them loose if damaged and allow them to free float in the ocean

bottom or pelagic long line

line of baited hooks that hangs free floating or on sea floor, can be up to 10 miles long, dangerous for open ocean ecosystems

bottom trawling

big ass bucket net they pull on the floor, bad for bottom of the sea floor

Purse seine

gill net with a draw string on the bottom to make a big santa bag, can easily trap megafauna as bycatch

Industrial shark fishing

finning is removal of fins upon capture and disposal of body at sea, shark fin fishing is legally landed sharks with fins removed and sold separately as part of processing

Magnuson-Stevens Fishery Conservation and Management Act

establishes National Marine Fishery Service

fisheries in federal waters (2-200 mi) are overseen by regional councils nominated by governers and informed by population data

most sharks are highly migratory and managed by NOAA

US endangered species Act of 1973

Prohibits unauthorized taking, possession, sale, or transport of endangered species

NMFS responsible for marine and anadromous fishes, Fish and Wildlife for everything else

smalltooth sawfish first marine fish listed in 2003

Osteichthyes synapomorphies

endochondral bone, gas containing lung derived from embryonic gut, dermal bones form a palate in the mouth, branchiostegal rays support gill chamber

Actinopterygii

fin rays with lepidotrichia, can fine tune location in water, found in every ocean and zone

Measurements

standard length: snout to base of caudal fin

fork length: snout to fork in caudal fin

total length

snout length: eye to tip of mouth

Anguilliform

entire body does lateral undulation, elongate cylindrical body, benthic habitat ex. eels

carangiform

lateral undulation via back half of body, fusiform round body ex. tuna, salmon

ostraciiform

lateral undulation via tail, variable body shape/habitat ex. boxfish

tetradontiform

propelling via pectoral fins, variable body shape and habitat ex. triggerfish, porcupinefish, sunfish

rajiform

propelling via sine wave down the fins horizontally, elongate body shape with suprabenthic habitat, ex. rays

labriform

propel via pectoral fin beating, variable body shape/habitat, ex. wrasses

Buoyancy vs. lift

lift is a force that you apply to water moving over your body, buoyancy can be stagnant

swim bladder (derived) — physoclistous

bubble sealed off in body with two chambers, phalangular tissue in the bubble can receive oxygen from arterial blood via counter current exchange, lactate and hydrogen ions trigger oxygen to be released from hemoglobin and diffuse into swim bladder

Swim bladder (ancestral) - physostomous

outcropping from GI tract that collects gases, gulp air from surface, fart to sink, herring maintain this state

Gas bladder variations

billfish and halfbeaks have vesicular gas bladder made of gas filled vesicles, some fish have completely lost it because they are benthic feeders

Cryptic coloration

I look like the environment

countershading

the way light bounces in the depth im in makes it hard to see me

iridiophores

pigmented cells in the dermis containing carotenoids or other compounds to make yellow, orange, and red, useful for camo in the meso-abyssopelagic

Territoriality

observed more in coastal, reef associated species, raised fins, open mouths, and sound production 

schooling

used for traveling, feeding on plankton, encirclement of streaming to avoid a predator

Migration

classified by its drivers, for it to be a true one you have to return to your starting location.

climactic, alimentary, gametic, refuge

Atlantic Menhaden

depend on currents to wash eggs from off the coast into an estuary, larva swim up a creek and come back for a year, go to the ocean for 2 years to chill

ASMFC uses fecundity and mortality to assess overfishing, life history traits enable informed management

Cod story

Cod - prefer colder waters, exist from shoreline to 300m out, eat benthic inverts and small fish, have 3 dorsal fins and barbel on chin

Cod “landing” peaking in 20th century due to baby boom and technological advancement, exceeded max sustainable yield

Cod wars

Iceland and UK were fighting over fishing rights and expansion of territorial waters, resulted in 200 nautical mile EEZ used today

Sarcopterygians

monobasic fins, first appear in the late Silurian to early Devonian

Coelacanth ecology

110-400m depth, 2m length, diphycercal caudal fin, ovoviviparous

coelacanth physiology

osmoregulate via urea retention, limb coordinate like tetrapods, intracranial joint connecting maxilla to braincase, rostral organ similar to electroreception in sharks, innervated by ophthalmic nerve, large fatty organ associated with lung for buoyancy

Amniote evolution

355 mya, presence of amnion and allantois allow for eggs to be laid on land, diverge into sauropsids and synapsids by late carboniferous

Marine reptiles of Mesozoic

what allows for this: plankton evolution/diversification, new continental margins and reef builders (corals) create Mesozoic marine revolution which cause 14 clades of tetrapods to return to ocean — ichthyosaurs, plesiosaurs, and mosasaurs

Ichthyosaurs

vivparous, streamlined bodies, loss of digits, progressively shorter hypocercal tails, by jurassic infants increase in size and start coming out tail first

Carangiforms in mesozoic

long protruding maxilla, tapering front and back ends, large dorsal fins, high aspect ratio caudal fin, large sclera

Mary Anning

influential in excavation of marine reptile fossils (especially ichthyosaurs) articulated the thesis of what coprolites (fossilized poop) was

Plesiosaurs

Sauropsids, inhabited freshwater to deep oceans, longer necks and shorter tails, flippers as long as trunk, pachyostosis in young and gastroliths, most likely flapped and pushed like penguins to move through water

Pachyostosis

having denser hard bone which allows for sinking for diving

Mosasaurs

squamates, lived in shallow epicontinental seas, lateral undulators, large conical teeth (like crocs), basal taxa were semi aquatic, by end of cretaceous some taxa had lost digits and gained hypocercal tails, moving into habitats caused changes in marine biodiversity

Factors leading to Mesozoic Marine Revolution

Triassic — hot and humid climates accompanied receding glaciation, extant sharks lived in the ocean and coelacanths had a burst of diversification. Mass extinction at the end which caused non-mammalian synapsids to decline and allowed sauropsids to become abundant and diverse

Jurassic — Pangaea split into Gondwana and Laurasia creating shallow seas and coastal environments, arms race between vertebrates and invertebrate prey, neopterygians diversified and giant teleosts lived in oceans, marine reptiles thus joined sharks as apex predators in the sea

Hypocercal tail

vertebrae extends into lower lobe of tail, making it longer than the upper lobe