Glub Glub Exam 2

Weird Scales: Deciduous

easily shed, defensive; some halfbeaks, herrings, anchovies

Weird Scales: “Spine” Scales

long, defensive spines; puffers, surgeons, stingrays, dogfish

Weird Scales: Scutes

Shield spines, defensive/protection (herrings) or steering

Keel Scutes

lateral (caudal) paired (left + right)

Finlet Scutes

dorsal/ventral; jacks, tunas

Weird Scales: Dermal Skeleton

fused scale plates, defense; ideal for protection, not speed; boxfishes, pipefishes, armored catfishes

Median (unpaired) Fins

Dorsal, anal, adipose (“fat fin”), caudal

What supports the fins?

Fin Rays

Fin Ray Types: Cartilage Rods

lampreys; unsegmented (one rod = one fin ray support), not branched

Fin Ray Types: Ceratotrichia

chrondrichthyes; protein fibers (elastin + collagen); unsegmented, not branched

Fin Ray Types: Actinotrichia

Actinopterygii (ray-finned fishes), other bony fishes; elastin + collagen fibers (homologous to ceratotrichia); branching

Fin Ray Types: Lepidotrichia

most bony fishes; hard, bony fibers; actinotrichia may be found at tips

Spines v. Soft Rays - Spines

hard, pointed, solid, unbranched

Spines v. Soft Rays - Rays

soft, not pointed, segmented, often branched

Adipose Fin

has very fine actinotrichia, or no rays; possibly vestigial; 5 families (not all homologous)

Locomotion: Undulation v. Oscillation - Undulation

use whole body like eel or have a really big fin like knifefish (whole body, partial body, long fin)

Locomotion: Undulation v. Oscillation - Oscillation

up, down, left, or right movement typically with fin

Locomotion: Anguilliform

body undulators; eels, most sharks, most larvae

Lcomotion - Posterior Undulators: Sub Carangiform

whole back half; salmon; hard to move straight

Locomotion - Posterior Undulators: Carangiform

back third; jacks, herring; move mostly straight

Locomotion - Posterior Undulators: Thunniform

tail and peduncle only; makos, tunas, billfish; move straight

Locomotion: Ostraciiform

tail oscillators; boxfishes, elephantfish, torpedo rays

Locomotion - Median Fin Oscillators: Tetraodontiform

rear dorsal/anal; puffers

Locomotion - Median Fin Oscillators: Balistiform

rear dorsal/anal; triggers

Locomotion - Median Fin Oscillators: Diodontiform

rear dorsal/anal; porcupines

Locomotion: Rajiform

pectoral undulators; rays and skates

Locomotion: Labriform

pectoral oscillators; wrasses, parrotfishes, chimaeras

Specialized Locomotion: Seafloor Walking

Modified ventral fins; sea robins, frogfishes, batfishes

Specialized Locomotion: Land Crawling

modified ventral fins (very muscular like lobe-fins); body undulators; mudskippers, lungfishes, walking catfishes, snakeheads

Specialized Locomotion: Jumping

needlefishes, tunas, salmon, mullet

Specialized Locomotion: Flying

flying fish, halfbeaks, hatchetfish

Cardiovascular System Route

Heart → Gills → Brain/eyes → Trunk muscles and organs → Heart

Cardiovascular System: Heart

4 chambers - Sinus venosus, atrium, ventricle, conus/bulbus arteriosus

Heart: Sinus Venosus

receives venous blood (low on oxygen); pushes into atrium

Heart: Atrium

pumps into ventricle (elastic like balloon)

Heart: Ventricle

Pumps into conus/bulbus arteriosus; thickest muscle

Heart: Conus/Bulbus Arteriosus

pushes into gills

Blood: Plasma

water, chemical solutes

Blood: Red Blood Cells

nucleated, yellow-red coloured, oval-shaped or round (just lampreys)

Blood: White Blood Cells

immune response, clotting, particle removal

Blood: Lymph

comes from veins (blood plasma), fluid recycling, fat transport, immune response

Gas Bladder

most bony fishes; located dorsal trunk coelom - above intestines (underneath vertebrae), below/beside kidneys

Gas Bladder Types: Physostomas (open-type)

ancestral (gar, salmon, carp catfish); crude lungs and buoyancy; bladder connects to esophagus; “open swim bladder”, “air gulping”

Gas Bladder Types: Physoclistous (closed)

derived; most teleosts; buoyancy only; bladder fully enclosed - seals during larval stage

Digestion Enhancements

increased absorptive surface area

Digestion Enhancements: Typhlosole

agnathans; fold inside intestine (intestinal wall fold)

Digestion Enhancements: Spiral Valve

elasmobranchs; internal screw-shaped intestine

Digestion Enhancements: Pyloric Caecae

2^o stomach pouches

Digestion Enhancements: Long/coiled Intestines

herbivorous or detritivore bony fishes

Mauthner Cells

“instant reaction” neurons; escape response (like jerking hand away from burn); hindbrain → spinal cord; lampreys, most other fishes (not hagfish)

Step 1: stimulus
Step 2: “C-start” Body Twist (avoidance)
Step 3: Tail extension (flight)

Mechanoreception

physical pressure; ciliated sensory “hair cells” within lateral line system and inner ears; detects unidirectional water flows (currents), oscillatory water flows (vibrations), sound pressure waves (hearing)

Mechanoreception: Equilibrium and Balance - Inner Ears

fluid-filled semicircular canals (full of hair cells); otolithic organ (=utricle) - teleosts and CaCO₃ “earstone” floating on hair cells; lamprey = 2 canals, elasmobranch = 3 canals, teleost = 3 canals + utricle, myxine = 1 canal

Mechanoreception: Lateral Line System - Neuromast

organs (one per skin/scale pore); bundled hair cells embedded in gelatinous cupula

Neuroamast: Canal Neuromasts

pore scales, dermal bones (head), shielded; more common for: adult fish, fast swimmers, moving waters

Neuromast: Superficial Neuromasts

integument, exposed; more common for: baby fish, sedentary fish, calm waters

Hearing (bony fishes)

inner ear otolith organs; earstone types - 1. utricle, 2. saccule, 3. lagena; sound waes vibrate the otoliths; elasmobranchs - sand particles in maculae replace the otoliths

Hearing: Gas Bladder Enhancements

sound waves vibrate (extended) gas bladder; amplifies ear sensors

Hearing: Otophysan Fishes

ear and gas bladder connected with series of bones; enhanced hearing; most FW fish, Weberian Apparatus

Weberian Apparatus

for hearing; tiny vertebrae bones connecting gas bladder to inner ear

Hearing: “-ophysic” Enhancements

gas bladder extensions; different types - laterophysic (anterior “horns” connect to lateral line system), otophysic (similar but connects to inner ear), otolaterophysic (connects to inner ear and lateral line)

Electroreception: Passive

electrical fields coming from environment; ampullary; 16% of fishes; ampullary organs derived from (ancestral) lateral line: Ampullae of Lorenzini (chondrichthyes, non-teleost bony fishes) or independently evolved (3 times) - osteoglossiformes (bony tongues), gymnotiformes (knifefishes), siluriformes (catfishes); embedded in skin, usually around head, conductive gel-filled pore, open to exterior, electroreceptors at base; primary function = prey detection

Electroreception: Active

Tuberous; 1.5% of fishes; tuberous organs - passive sensors optimized for receiving fish’s own active electro-generation; embedded in skin, usually around head, conductive gel-filled pore, sealed form environment, electroreceptors at base; functions are prey detection and communication

Vision: Pupil Differences - Elasmobranchs

adjustable diameter, primary shape varies - slit-shaped (most sharks), circular-shaped (deep sea sharks), cresent-shaped (batoids - stingray)

Vision: Pupil Differences - Teleosts and Lampreys

pupil diameter fixed, no dilating

Vision: Lens Differences

denser and rounder than land vertebrates; limited shape adjusting; fishes move whole lens to focus - eyes can be smaller

Vision: Sclera (outer “white” eye) Differences

possible sclerotic bones - mostly teleosts, stabilizes eye - fast-swimming fishes

Vision: Choroid Differences

possible tapetum lucidum - “eyeshine”, light reflecting layer under retina, enhances low light visibility (for nocturnal or deepwater fishes and sharks)

Chemoreception

smell (olfaction) and taste (gustation); smell uses communication, predator/prey communication, habitat/territory identification; taste uses food recognition and food acceptance

Olfaction

external nostrils (nares) - blind sensory sacs (most fishes) or route into oral cavity (chimaeras, lungfishes, hagfish)

Olfaction: Agnathans

one nostril

Olfaction: Gnathostomes

two nostril pairs; each par has an incurrent nostril and excurrent nostril, olfactory sac, chemical detection

Olfaction: Gnathostomes - Olfactory Sac

olfactory epithelium layer - folded into “rosette”, more folding = better smell

Olfaction: Gnathostomes - Chemical Detection

amino acids (short peptide chains), hormones

Gustation: Receptor Cells

high density taste buds (30-100 clusters) or solitary cells

Gustation: Mouth Areas

jaws, vomer, tongue, gills, lips, barbels

Gustation: Body Areas

integument, fins

Osmoregulation

maintains internal water and solute balance

Osmoregulation: Fish Organs

gills, kidneys

Kidneys

ventral to spine, dorsal to gas bladder; paired, elongate, flattened; often fused into dark tissue layer; length of trunk

Kidneys: Pronephros

“head kidney”; anterior, “first kidney” - young fish, supplanted by mesonephros

Kidneys: Mesonephros

“trunk kidney”; posterior, primary renal functions

Hypotonic

lower concentration outside - osmotic flooding

Isotonic

same concentration inside and outside - osmotic balance

Hypertonic

higher concentration outside - osmotic dehydration

Osmoregulation: Fish urine is mostly…

water, nitrogenous waste (ammonia); two limits: (1) fish urine cannot be more concentrated than blood, (2) <50% nitrogenous wastes removed by kidneys (gills excrete the rest)

Marine Osmoconformers

body solute balance - seawater solute balance (isotonic); SW osmoconformers match ambient SW’s solute content (hagfish only); stenohaline - narrow salinity tolerances; body solute balance does not equal seawater solute balance (all vertebrates are osmoregulators); SW ray-finned fish keep tissues fresher than seawater and SW elasmobranchs and lobe fins keep tissues saltier than seawater

Elasmobranchs Stink

store excess urea; CO(NH₂)₂ in body tissues - TMAO (stabilizes protein denaturing from urea toxicity); slightly hyperosmotic to seawater (water passively enters gills); purge excess salts via rectal gland; saline drains into intestines; FW elasmobranchs - reduced rectal gland, low urea production

Sarcopterygians (lobe-fins)

Coelacanths (marine, urea + TMAO), lungifhses (FW, urea + TMAO when hibernating); lobe-fin process unrelated to Elasmobranchs (convergent evolution)

FW Teleosts (+ Lampreys)

Body fluids are hyperosmotic; osmotic goals: retain salts, pump out water; (1) minimal drinking, (2) urinate a lot, (3) gills absorb salts

SW Teleosts (+ Lampreys)

body fluids are hypoosmotic; osmotic goals: excrete salts, drink water; (1) lots of drinking, (2) minimal urination, (3) gills excrete salts; teleost blood salinity ~9ppt (same as us)

Gonochoristic Gender

gender is chromosome controlled (>90% of fish species); sex chromosome types XX and XY system (elasmobranchs, most bony fishes) or ZZ + ZW (females ZW, some bony fishes); autosomal chromosomes may also affect gender

Environmentally Controlled Gender

water temperatures, seasons, hormones, food, social status; lampreys (no chromosome control), various bony fishes (some flounders); masculinization and feminization; environmental may also affect genetically controlled genders

Gender Types in Fish: Dioecious

separate sexed individuals

Gender Types in Fish: Monoecious

bi-sexual individuals (hermaphrodites)

Fish Gonads

visually paired - but may be unequal-sized or only one gonad might work

Fish Gonads: Testes (sperm organs)

aboves intestines, below gas bladder, smooth texture, creamy-white colour, 0-2 sperm flagella

Fish Gonads: Testis (single)

lampreys - fused embryologically; hagfish - loss of left-side ovary; various fishes (guppy)

Fish Gonads: Ovaries (egg organs)

same place as testes; mass may increase with body size - maximum 70% of body weight; eggs spherical or elongate, contain oil-filled yolk, and may have attachment structures (stalks, spines, filaments); unspawned eggs are reabsorbed

Fish Gonads: Ovary (single)

lampreys - fused embryologically, hagfish - loss of left-side ovary; various fishes (needlefish)

Fish Fecundity

number of eggs released by female per spawning event; extremes: 1-2 eggs (some livebearing sharks), millions of eggs (ocean sunfish, tarpons); may increase with body size but decreases with bigger egg sizes (bigger females) and more parental care