BIOE 127 Midterm 2

pitch

up and down

yaw

left and right; on the x-axis

roll

rolling

laterally compressed body form

increased depth, decreased width

increases maneuverability

dorsal-ventrally compressed body form

decreased depth, increased width (think ray)

best for benthic lifestyle

fusiform body form

torpedo shaped, think your typical fish

high speed swimming and energetically efficient (reduces drag)

elongated body form

eel-like; think “hagfish”

allows forward and backward movements in and out of tight spaces and in soft bottom of seafloor

ovate body form

oval-like; help deter predation due to body depth exceeding predators’ gape limit

sub-circular body form

think puffer fish; usually individuals will have outward predator defense (spines, armor, toxins) and are able to maneuver efficiently/hover

superior mouth position

mouth opening towards top of head

lower jaw longer than upper jaw

prey on food items near waters surface (insects, plankton, leaves)

• ex: arowana or hatchetfish

terminal mouth position

mouth placed in middle/tip of head

upper and lower jaws equally long

pelagic feeding — chasing prey or catching them when immediately in front of mouth

• ex: surfperches

inferior mouth position

mouth positioned on ventral side of fish head

allows for efficient benthic feeding on small inverts and crustaceans as well as detritus and algae

• ex: suckers, rays, chimaera

Carangiform swimming

movement via tail

larbiform

swim via pectoral fins and use caudal as rutter

• will swim carangiform in emergencies

energetically efficient

anguilliform

use most of body (think move like snake) to swim

common in elongate animals

ostraciform

use ALL fins to swim while body stays still

gill rakers

stiff protrusions on the gill arches that allow food to be caught

large prey corresponds to thicker rakers

small prey corresponds with finer rakers

protect the gill filaments from being tangled up with food and allow them to conduct efficient oxygen exchange

filter feeding mechanisms

steps:

• fish catches prey in its mouth and it is caught onto the gill rakers in its mouth

• fish have muscle spasm to bring prey from rakers to front of mouth

• swallow prey once in front of mouth

can be a ram or suction feeder

large gape and wide mouth relative to body size

most filter feeding organisms will have small prey and therefore fine gill rakers

pelvic fin placements

thoracic, abdominal, mantle

thoracic pelvic fin

underneath pectoral fin

abdominal pelvic fin

much behind the pectoral fin

mantle pelvic fin

near to the chin

finlets

small, flexible fins that create turbulence in water to allow faster swimming

keel

on the side of the caudal peduncle allowing pitch control and stability in fast-swimming fish

cirri

fleshy flaps used often for chemoreception and camouflage (look like kelp bits on seahorses)

preadaptation

a trait can evolve because it served one particular function but subsequently can come to serve another

• results in shifts of a trait function during evolution

pectoral preadaptations

pectoral fins run length of body (flying fish, rays, chimaera)

• generates lift in animals

pelvic fin preadaptations

suctioning pelvic fin in clingfishes

• adhesion to substrate

• modified both the pelvic and pectoral fins

claspers

• modified pelvic fin in sharks that work to clasp onto the female genetalia for insemination

caudal fin preadaptations

heterocercal tail (asymmetrical increasing top fork — thresher sharks)

• animal stuns prey with whip-like tail

hypocercal tail (asymmetrical increasing size of bottom fork — flying fish)

• allows animal to beat tail against the water to increase its speed while giving it increased upward thrust — increases air time

anal fin preadaptations

internal fertilization via intromittent organ (surfperches)

• male organ derived from anal fin specialized for sperm delivery (gonopodium)

dorsal fin preadaptations

flat (lacking) dorsal

• defensive locking mechanism allowing for adhesion to individuals or substrates

spines & pterygiophores

• defensive and connect spines/rays to vertebral column

lures

• attract prey via light or yummy looking item

angler fish lure parts

illicium: modified, flexible, elongated spine extending over head that fish can control (wiggle)

esca: bioluminescent, fleshy bulb lure to attract prey

snout preadaptation

elongated (sawfish)

• uses elongated snout to stun prey

stereo chemoreception (hammerhead)

• allows animal larger chemorecpetive radius and better directional distinction

strouhal number

0.25-0.35 = efficient swimmin

product of the frequency of tail flapping times the jet’s width (length of tail flapping range).

forces acting on a fish

drag, lift, weight, thrust, medial (per fin)

scale types

placoid, ganoid, cycloid

placoid scales

characteristic of chondrichthyes

dermal denticles

reduced turbulence and drag

scales in mouths of earliest known verts that evolved into teeth

ganoid scales

surface covered in ganoine (mineralized tissue); found on primitive fishes (older lineages)

cycloid scales

a loss of ganoine; soft-rayed

• ctenoid — spiny-rayed fish scales

buoyancy

maintenance of vertical position within the water column; potentially energetically costly

many fishes had lungs that eventually evolved to lose their respiratory function and turn into gas bladders

chemical buoyancy

maintenance of high levels of low density lipid content in livers to maintain buoyancy

• occurs in pelagic elasmobranchs (sharks and rays)

• does not compress allowing for quick changes in depth

• 20-30% of body weight

• incredibly energetically costly but can be metabolized during starvation

cartilage incredibly buoyant as well (55% less dense than bone), assisting in buoyancy

gas bladder (swim bladder)

used to regulate buoyancy (by changing size) and sound production/detection in some fish species

respiratory gas bladder

connected to the gut

continuous gulping to stay buoyant

vascularized and subdivided

• adapted for gas exchange

Physostomous gas bladder

more primitive sac

derived from the outpocket from the gut

vascularized

maintains connection to the gut via pneumatic duct

pathway:

• gas enters via gulping and/or diffusion from gas gland

• gas exits through the pneumatic duct

puck reflex

sphincter opens, bladder connected to gut, burps air

physoclistous gas bladder

sealed off from gut, no pneumatic duct

gas enters and exits via blood through countercurrent exchange (gas gland/rete mirable and ovale)

• excess gas offloaded via gills

active movement of oxygen from rete mirable to swim bladder

found in more derived (evolutionarily young) teleost groups

gas bladder components

gas gland, rete mirable, ovale/pneumatic duct

gas gland

inflates swim bladder through diffusion

flows from dorsal aorta to gas gland into bladder

pathway:

• secretes lactic acid (dissociates H+ & lactate)

• hemoglobin dump O2 via Bohr and Root effects, raising partial pressure of oxygen

• reduces the solubility of gases in solution, leading to formation of gas bubbles (including CO2)

• drives gas bubbles into swim bladder

rete mirable

looping bundle of venous and arterial capillaries that generates a concentration gradient

blood travels through rete mirable, travels to gas gland, and oxygen enters swim bladder

ovale/pneumatic duct

removes gas

• deflation of swim bladder occurs via diffusion rather than active transport

pathway:

• muscles contract or relax to exposed the vascularized area for gas reabsorption

• allows gas bubbles to exit the swim bladder

blood flow to the region is controlled

Bohr effect

bloods affinity for hemoglobin decreases as acidity (and CO2 concentration ) increases

• more acidity, less bonding to hemoglobin

root effect

hemoglobin will dump oxygen at a speedy rate when acidity increases

when pH increases (becomes less acidic) O2 rebinds relatively slowly in comparison

Ram feeding

goes towards prey with its open mouth

• free gill membranes (not joined to isthmus or each other)

prey size limited by gape size

more tubular and narrow mouth cavity

Suction feeding

gill membranes joined/united but not joined to isthmus

wide gape

more conical and wide mouth cavity

biting feeding

teeth modified/evolved for prey type

use teeth to handle prey

sometimes have pharyngeal jaw to grab prey from mouth and retract it into pharynx/digest it

Nototheniidae — antarctic ice fishes

predominantly benthic, some species pelagic — all lack swim bladders like their ancestors

large proportion of skeleton is cartilaginous (less dense than bone)

contain blubber layer under their skin with lipid deposits throughout as well as fat cells between muscle fibers

respiratory constraints

less oxygen present than in air (~1% compared to ~20%)

seawater contains 25% less oxygen than freshwater

• less solubility due to increased salts

oxygen is lowest in warm marine environments

high density and viscosity means more energy required to move water against respiratory surfaces

suction respiration

two linked chambers, buccal cavity and operculum (gill cavity)

pathway:

• open mouth brings water in and expands the gill cavity while the actual valve to let it through to the opercula closed

• close mouth, open operculum valve, contract buccal cavity

• water rushes through operculum valve over gills to allow for exchange

ram respiration

fish keeps mouth open while swimming forward to force water to rush over gills and participate in gas exchange

gills

efficient oxygen extraction from water through countercurrent exchange over large surface area (from filaments)

gill countercurrent exchange

• blood in the lamellae flow in opposite direction of water

• as blood picks up O2 from the water, the blood moves towards an area of water with a higher concentration of oxygen

aerial respiration

evolved 400 mya and has arisen 38 separate times

>370 extant fishes breathe air

• amphibious fishes:

  • supported gill structures to prevent collapse

  • percolate water in gill and mouth chambers

  • often scaleless skin that is well vascularized for gas exchange

• Labyrinthine plates

Labyrinthine plates

highly vascularized chamber that can hold air and allow for gas exchange in aerial breathing fish

facultative air-breather

supplements respiratory needs with air (Australian lungfish)

obligate airbreathers

require access to air in order to sufficiently exchange gases (African and South american lungfish)

heart placement & circulation

heart ventrally and posteriorly positioned behind the gills in all fishes

sharks have conus arteriosus whereas teleost fish have a bulbus arteriosus that is more flexible in order to deal with pressure constraints giving continuous blood supply

Endothermic fishes

large body size

circulatory system is modified to allow for countercurrent exchange to retain heat

• loss of contractile fibers in the eye to minimize heat exchange (produces heat)

• veins and arteries go more towards inner body than outer body, veins and arteries next to one another to minimize heat exchange as blood flows through body

osmoregulation in freshwater fishes

inside of fish is much saltier than aquatic environment (hyperosmotic)

water always is going through the gills (fish always peeing ammonium)

• fish always losing salts to become less hyperosomotic to environment

chloride cells:

• cells in the gills that are packed with mitochondria that actively pump in salt from the environment

osmoregulation in saltwater fishes

inside of fish is much less salty than surrounding environment — hypoosmotic

• always losing H2O so it must drink water

• must pee minimally to avoid losing salts and water

chloride cells:

• in gills; pump out salts from their bodies to remain at safe osmolarity in body from high salt content they’re drinking

osmoregulation in sharks

osmolarity in body is higher than that of the seawater

• excrete urea (not very toxic compared to ammonia), can accumulate high concentrations to allow internal self to remain at high osmolarity

chloride cells:

• actively pump in salts from environment to maintain high internal osmolarity

bulbous arteriosus

necessary in fish as it stretches to absorb the shock of the ventricle contracting

if this were not present to absorb the shock, the high pressure pulse would burst the capillaries in the gills

niche partitioning

species evolve to exploit specific niches in order to lower competition for territory and foraging — causes variation between closely related species when it comes to feeding strategies and mechanisms (diversification)

methods for measuring diet

• stable isotope analysis (nitrogen or carbon)

• stomach content analysis

• DNA/Metabarcoding gut/feces analysis

• biochemical markers (fatty acid profile)

methods for measuring growth

• scales

• otolith

• eye lens

growth — scale analysis

scales have rings that form rings (circuli) that grow continuously

• winter months have slower growth and more densely packed circuli (annuli) whereas summer months have more broadly spaced ones.

• each couple forms a year of life for the fish

growth — otolith analysis

otolith grow continuously over the course of fish life (one layer a day)

by taking out otolith, cutting in half, one can look at layers and (same as scales) find the tightly packed and more spaced out rings to estimate age of fish in years

growth — eye lens

radiocarbon analysis of elasmobranch eye lens

gonochoristic sexual systems

each organism is either male or female with the corresponding gametes and their sexual organs remain the same throughout their entire lifetime

hermaphrodites

either simultaneous or sequential

sequential hermaphrodites

born with one gonad, switch to other later in life

protandrous or progynous

protandrous hermaphrodites

male first, then female

ex: clownfish — start off as males with dominance hierarchy, females are the largest and highest role. as one passes on, the next most dominant male will change to the dominant female. no cheating!

progynous hermaphrodites

female first, then male

sequential hermaphrodites

tends to occur in species where it is rare to find member of opposite sex of same species

no present sex chromosomes

environmental sex determination

found only in the minidia minidia species

temperature of the water determines the sex of offspring

unisexual

all female populations or populations that reproduce asexually

do not have costly sex

cost of sex

males

• are only “useful” for fertilization but require much energy to pass on their genes to offspring

hybridogenetic unisexual

female requires male (of closely related but different species) for initial fertilization but none of his genes are actually expressed or passed down in the offspring

• small portion of his genome is passed into species offspring and (due to their asexual nature) will last within the species for 100s of years

gynogenetic unixual

sperm acts as a trigger for fertilization but is not passed on through the genome

parthenogenetic unisexual

selfing; sperm not required for fertilization or development

• theses populations will become sexual for one generation before reverting back to asexual reproduction (genetic diversification)

fitness

= viability + fecundity + longevity + mating success

females (usually) limited by

# of eggs &/or pregnancies

males (usually) limited by

# of females mated

intrasexual competition

sperm competition

lead to the emergence of ornaments — costly to make and cause individual to be more vulnerable to predators

ex: swordtail — longer tail is more attractive but decreases male’s swimming ability

intersexual competition

males want to mate with females but females are choosy

shark developmental strategies

vivipary, ovovivpary, and ovipary

vivipary

give birth to full live young that developed and were nourished in the mothers body through a placental-like sac/connection

ovovivipary

develop their eggs which hatch inside the mothers body to give birth to live young

ovipary

lay fertilized eggs in the water

parental care

in species that have present parental care:

• most care is done by male fish due to the high energy costs at beginning to produce eggs (female must recoop)

• usually uniparental

• found in species that mostly do external fertilization

  • internally fertilizing species usually see females doing most of parental care

• mouth brooding

• forehead brooding

• armpit brooding

• pelvic brooding

done to protect young from predation rather than provide nutrients, though some species may also do that

superfetation

broods fertilized at different times