Fish exam 2

Origin of gills

Origin of gills

Pharyngeal arches (used as feeding apparatus in more basal species

Volume vs surface area

Ratio of surface area to volume decreases as overall size increases.

Function of gills

Allows fish to “breathe”; water is drawn in through the mouth and forced out through the operculum, travelling through the gills on the way out (fish can only make use of dissolved oxygen in water, not O in H2O). Gill lamellae increase respiratory surface area and orient flow of blood stream against water

Structure of gills

Located in the branchial basket; gill rakers support gill arches which in turn support gill filaments (gill lamellae on stuck off of gill filaments)

Counter current exchange

Water being forced over gill filaments moves in the opposite direction as blood flow, therefore maximizing the amount of oxygen that can be diffused into blood (least oxygenated blood exchanges with least oxygenated water, but there’s still a gradient so it diffuses)

Environmental factors affecting fish respiration

Temperature, solutes, turbulence vegetation, microbial activity

How icefish live without hemoglobin

Water is very cold and therefore incredibly high in oxygen, no hemoglobin so blood does not freeze

Why whales didn’t evolve gills

Whales are endothermic and having gills means blood needs to come in contact with the water (same temp as water). Because whales are mammals, their anatomy is set up to insulate blood and keep it warm.

Origins of swim bladder

Evolved from lungs (lungs first)

Reasons for lung evolution in fish

Air has more oxygen than water and is more advantageous, especially with dissolved oxygen fluctuations in water (not for land exploration.

Swim bladders role in bouyancy

Provides an upward force equal to the force of gravity and the mass of water pushing fish down; allows them to “hover” in the water

Physostomus fishes

Fish in which the swim bladder is connected to the digestive tract; fish gulp to inflate the swim bladder (more primitive)

Physoclistous fishes

No connection between swim bladder and gut; is filled by oxygen in the bloodstream

Function of gas gland and rete mirabile

The gas gland secretes lactic acid into the bloodstream in the rete mirabile. Under acidic conditions, hemoglobin in blood releases oxygen, creating a high concentration of O2 in rete mirabile, causing diffusion into bladder.

How countercurrent exchange works in swim bladder

The blood flow in the rete creates a sideways U, as air diffuses out of the bladder and moves through the bloodstream, it diffuses back into the inflowing vessel.

Relationship between depth, pressure, and volume

Higher depth = higher pressure, therefore at higher depth more oxygen is needed to inflate (increase volume) the swim bladder (why deep-water fish have longer rete mirabile)

Barotrauma

When fish are rapidly pulled from deep water, pressure decreases and gasses expand; swim bladder expands rapidly and pushes stomach out of mouth.

Autostylic jaws

Upper jaw is fixed to the cranium and only the lower jaw moves (ex. chimeras and us)

Amphistylic jaw suspension

Another modified pharyngeal arch, the hyomandibula connects the jaw joint (no extant fish have this)

Hyostilic jaw suspension

Upper jaw is attached to the braincase only by ligaments, allowing for the protrusion of the jaws (ex. modern sharks)

Suction feeding

By dropping the lower jaw and increasing the volume in the mouth, the pressure decreases and creates a vacuum.

Mouth size, bite force, and suction force tradeoffs

Large mouth can fit large prey but a smaller mouth has more suction; suction requires less precision in prey capture but results in lower bite force.

Pharyngeal jaws

Jaws in the back of fishes throats’ that are used to chew food or pull food from back of mouth to esophagus (oral jaws for capture and pharyngeal jaws for processing). Moray eels have highly protrusible jaws called raptorial jaws used in prey capture.

Suspensorium; allows lower jaw to drop, enlarging mouth cavity for suction and extending jaws

Hyoid series; helps to extend oral cavity and branchiostegal rays seal water backflow into gills

Neurocranium; houses the brain and connects to jaws via muscles and ligaments

Branchial basket; supports the gill filaments and maintains proper orientation to blood flow. Also holds pharyngeal jaws.

3 regions of neurocranium

Ethmoid (front near nose; smell), Orbital (middle; sight), Occipital (back, hearing)

Alternative strategies to suction feeding

Ram feeding (hit things really fast) and filter feeding

Buccal pumping

Method of breathing in which fish open mouth, creating a suction and having water flow in, and then close the moth, forcing water out over the gills (normal system of fish breathing).

Ram ventilation

Have to move through the water to breathe; water passes over gills.

Tuna physiology

generate heat through metabolic activity, allowing for higher swimming speeds.

Regional endothermy

Swordfish and some sharks: Certain parts of body are kept at higher temperatures than the water through countercurrent exchange system. These areas (brain, eyes, muscle) are warmer and therefore are able to perform better than if they were colder.

limitations caused by humans reliance on sight

It is hard to understand how species that do not rely on salt perceive the world.

Difference between apes and humans

Apes have a better immune system and sense of smell, less neurons

Umwelt

Different organisms use sensory organisms to perceive the world and therefore each perceives a different world.

taste perception in catfishes

Catfishes have taste receptors all over their body, primary sense is taste.

Sexual dichromatism

Brightly colored males, usually the product of sexual selection. Also maybe species recognition.

Aposematic coloration

Coloration to warn potential predators of venom or poison.

Batesian mimicry

Coloration used by harmless species to mimic species that are venomous or poisonous (aposematic coloration); lots of mimicry in larval species but not adult because more vulnerable to predation?

Camouflage

Coloration to blend into surrounding habitat.

Aphotic vs dysphotic zone

Dysphotic zone has some light (not enough for photosynthesis) while aphotic zone has no light.

Cave and deep river fish

Lack of pigment and little/no eyes

Deep sea fishes

eye loss is rare due to bioluminescence, make their own light (example. anglerfish)

2 ways that bioluminescence can appear in fishes

Innate: light from chemical reactions in one’s own cells

Symbiotic: Light is generated by photosynthetic bacteria within host organism

Chemoreception vs mechanoreception

taste and smell (chemical reactions) vs touch, hearing, and lateral line

Sound as waves

Vibrations passing through a transmission medium (air, water); amplitude=intensity and frequency=pitch

Function of the mammalian ear

Sound waves enter the ear canal and strike the eardrum, which transmit to the inner ear. Vibrations move fluid in inner ear that stimulates hair cells and sends an electric signal to the brain.

Function of semicircular canals

Maintain balance and positional awareness; detect and give sensory responses to rotational movement.

Consequences of hagfish/lampreys only have 2 canals

no. fucking. idea.

Hearing in fishes

Fish lack true ears, sound perception is mediated by otoliths (dense bony structures in skull)

Otolith structure and function

Dense bony structures within the skull. Sound vibrations travel through the flesh, but the otoliths vibrate less because of density. This creates a shear which stimulates hair cells in the otolithic membrane (have 3 of them)

Other uses of otoliths

Aging fish (growth rings) and track migration pathways through stable isotope analysis.

Lateral line system

Main system in fishes used to detect vibrations and water movement. Pores alongside fish that lead to an internal canal.

Canal neuromasts

Small clusters of hair cells associated with laterosensory canals (usually bony tubes). Respond to the flow of water through tubes and allows assessment of directionality based on canal orientation.

Superficial neuromasts

Small clusters of hair cells scattered across the surface of the head and body. Sense of flow of water, but not highly specific.

Cranial lateral line system

Complex lateral line system involved in sensing movement near the head. Supported by a series of dermal bones to enclose the canals or support nerves or neuromasts (includes infraorbital bones).

Lateral line difference from hearing

Senses changes in water, technically waves, but not sound

Electroreception

Detection of natural electric stimuli (absent from hagfish, most teleosts, and tetrapods)

Galvani experiment

Movement could be induced in dissected frog legs by supplying an electric current

Action potentials

How nerves and muscles operate; occurs when an excitable cell depolarizes its membrane, resulting in the propagation of the charge along the length of the cell (charge is carried by ions, not free flowing electrons)

Electrocardiogram

Shows voltage change in comparison to contractions of the heart (more muscular activity=more change in voltage)

Ampullary organ structure

Made up of a pore on the surface of the skin, a gelatinous and highly conductive substance, receptor cell(s), and a sensory organ.

Ampullae of Lorenzini

Pores that detect electric fields (the shark guys); evolved from neuromasts of the laterosensory system.

Discovering electroreception

Bullhead experiment: catfish and metal rod, strong charges means run away weak charges they attack

Shark: More attracted to electric current than smell and sight.

Explanations for electroreception in lamprey and not hagfish

Either more primitive OR an adaptation to their particular niches

Electroreception in other vertebrates

Dolphins, aquatic salamander, monotremes; probably retained primitive characteristics

Electroreception in teleosts

Notopteridae and Siluriformes are electroreceptive only. Mormyridae and Gymnotiformes are electroreceptive and electrogenic.

Electrogenesis

Fish species capable of generating a strong electric discharge.

4 groups of fish with strong electric discharge

Electric eel, electric rays, stargazers, electric catfish

Electrolyte structure

Excitable cells that are arranged in a series, allowing a charge to be propagated through them, increasing the voltage.

Electric organs

Use ions to transmit a charge throughout the cell, as ions are transferred through excitable cells, the charge is amplified.

Weakly electric fishes

Fish that use a continuous weak discharge of electricity to sense their surroundings and communicate. Charge starts in the electric organ; emanates from tail and is received by electroreceptors in the head (most similar to sonar)

2 groups of weakly electric fishes

Mormyridae and Gymnotiformes (both live in deep muddy river systems in the tropics)

Tuberous electroreceptors

Receptors used to pick up ones’ own EOD. Also used to pick up EODs of other fish species for communication and recognition. (less sensitive than ampullary organs.

Other groups that have electric discharge

skates and several catfish species; hard to determine function because they have very elaborate mating behaviors and are probably not used for navigation

Measuring EOD

uses a tool called an oscilloscope to show voltage change over time as a waveform; can also use an audio interface (kinda janky tho). All of these factors make it hard to measure in the field.

EOD waveform

A graph in the form of a wave that pictures the electric force discharged by fishes.

Signal cloaking

Make it hard for catfishes to pick up on EOD< Do this by having a biphasic EOD, which have less energy at a lower frequency. This allows for electric fish to have a “louder signal at higher frequencies. Ampullary organs are keyed into low frequency electric fields of prey, cloaking them from the ampullary organs of catfishes.

Monophasic vs biphasic EOD

Monophasic EOD has one wave while biphasic have 2. Electric eels do not need to hide EOD because they can defend themselves with discharge. Only electric eels and some mimics have monophasic EOD.

Why we see EOD character displacement

It reinforces species recognition and limits hybridization.

EOD’s possible relation to speciation

Different EODs could be a form of reproductive isolation