Ichthyology and Fish Biology Vocabulary

A detailed 90-card vocabulary set covering fish anatomy, classification, physiology, adaptations, sensory systems, and chondrichthyan biology based on lecture material.

Dermal bone

Also known as membrane bone, it forms directly through ossification of mesenchyme without passing through a cartilaginous stage.

Endochondral bone

Also known as cartilage bone, it is formed initially within a cartilaginous matrix and is evolutionarily younger than dermal bone.

Linnaean classification obligatory levels

The seven obligatory ranks of taxonomy: Kingdom, phylum, class, order, family, genus, and species.

Cycloid scales

Round, flat, and thin elasmoid scales found on fishes such as trout, minnows, and herrings.

Ctenoid scales

Elasmoid scales primarily found on spiny-teleosts, characterized by tiny comb-like projections on their posterior exposed edge.

Ctenii

Tiny comb-like projections found on the posterior exposed edge of ctenoid scales.

Rete mirabile

A counter-current exchange system for gas composed of a looping bundle of arterial and venous capillaries.

Fish habitat distribution percentages

The breakdown of fish species habitats: 41.2% freshwater, 58.2% marine, and 6% diadromous.

Apomorphic character

A specialized, evolutionarily derived trait that is new and distinct from an ancestral condition.

Plesiomorphic character

An older, ancestral, primitive trait passed down from ancestral conditions.

Poikilotherm

An organism whose internal body temperature varies directly with the surrounding environment.

Homeotherm

An organism that maintains a stable, constant internal body temperature within a narrow range regardless of surroundings.

Endotherm

An animal that generates its primary body heat internally through high metabolic activity.

Ectotherm

An animal that relies on external environmental sources to absorb heat and regulate its body temperature.

Physostomous gas bladder

A type of gas bladder that retains a open physical connection to the esophagus via a pneumatic duct.

Pneumatic duct

The connecting tube between the esophagus and the gas bladder in physostomous fishes.

Physoclistous gas bladder

A type of gas bladder that has completely lost its connection to the esophagus.

Head skeleton functional units

The 5 structural units of the fish head skeleton: cranium, suspensorium, jaws, opercular apparatus, pectoral girdle

Abdominal vertebrae

Vertebrae located in the trunk region of a fish that bear ribs.

Caudal vertebrae

Vertebrae located in the tail region of a fish that feature a closed hemal arch to protect major blood vessels.

Hemal arch

A ventral closed arch on caudal vertebrae that protects major blood vessels running through the tail.

Gas bladder functions

The four main physiological functions: hydrostatic balance, sound production, sound reception, and respiration.

Notothenioid glycoproteins

Proteins circulating in the bloodstream of arctic Notothenioids that function as antifreeze to prevent bodily fluids from freezing.

Five defining traits of fish

Poikilothermic, aquatic chordates, appendages developed as fins, chief respiratory organs are gills, and body covered with scales.

Shark body shape

Morphology characterized by a large pointy-snouted head, large pectoral fins, and a body ending in a long pointed rat-like tail.

Skates and rays body shape

A dorso-ventrally flattened body shape typical of flatfishes.

Chondrichthyes skeleton

A skeleton constructed entirely out of cartilage, which is lighter than bone.

"Fish" vs. "Fishes"

'Fish' refers to multiple individuals of a single species; 'fishes' refers to individuals of multiple different species.

Phylum Chordata characteristics

Four essential diagnostic traits: pharyngeal openings, notochord, dorsal hollow nerve cord, and post-anal tail.

Rover-predators

A body shape category of active fish adapted for continuous search and pursuit of prey in open water.

Lie-in-wait predators

A body shape category of fish adapted for ambushing prey with sudden bursts of speed from a resting position.

Surface-oriented fish

A body shape category adapted for feeding and swimming near the top layer of the water column.

Bottom fish

A body shape category optimized for resting or feeding directly on or near the aquatic substrate.

Deep-bodied fish

A body shape category flattened laterally to optimize maneuverability in dense or complex environments.

Eel-like fish

A body shape category characterized by an elongated, highly flexible body for snaking through crevices.

Subclass Holocephali

Chimeras or ratfish; characterized by no gill slits, no placoid scales, a persistent notochord, no spiracle, and no cloaca.

Vertebrate and fish species counts

There are approximately 60,000 total vertebrate species, with roughly 30,000 of them being fish species.

Subclass Elasmobranchii

The subclass of cartilaginous fishes comprising sharks, skates, and rays.

Tapetum Lucidum

A reflective tissue layer behind or in the retina that bounces light back through photoreceptors to increase sight sensitivity in dim or turbid water.

Manta ray leaping

Behaviors performed to avoid predators, perform mating rituals, shed parasites, demonstrate fitness, or consume surface zooplankton.

Diadromous fish

Fishes that migrate between freshwater and saltwater habitats at specific stages of their life cycle.

Lateralis system

A specialized sensory mechanoreceptive network used to detect vibrations, water movements, and pressure gradients.

Neuromast

The individual sensory receptor unit of the lateral line, consisting of sensory hair cells and supporting cells.

Cupula

A gelatinous dome-shaped structure covering neuromast cilia that sways with water movement to stimulate hair cells.

Lateralis canal

A sub-epidermal, fluid-filled tube along the body sides and head housing neuromasts and shielding them from direct hydrodynamic drag.

Lateralis mucous

A specialized viscous fluid within the lateralis canal that transmits external pressure waves to neuromasts.

Intrauterine cannibalism

The condition where developing shark embryos feed on their siblings or unfertilized eggs inside the maternal uterus.

Adelphophagy

A form of intrauterine cannibalism where early-hatching embryos actively hunt and eat smaller embryos in the same uterus.

Oophagy

A form of intrauterine cannibalism where developing embryos eat unfertilized nutrient-rich eggs produced by the mother.

Oviparous

Egg-laying animals whose embryos develop externally using nourishment solely provided by the egg yolk.

Ovoviviparous

Animals that retain yolk-nourished eggs internally until hatching, giving live birth without direct placental nourishment.

Viviparous

Animals that produce live young following internal embryonic development supported by continuous direct maternal nourishment.

Shark bite distribution

The lower legs are the most frequently bitten area on humans, accounting for 32% of shark bites.

Shark attack fatality rate

Roughly 2% of recorded shark attacks on humans since the year 2000 have resulted in fatalities.

Threatening posture in sharks

An agonistic display characterized by side-to-side head movements, dropped pectoral fins, and a hunched back.

Pectoral fin attachment distinction

Sharks have moderate pectoral fins separate from the head, whereas skates and rays have enlarged pectoral fins fused to the head.

Palatoquadrate

The cartilaginous upper jaw element in sharks.

Meckel's Cartilage

The cartilaginous lower jaw element in sharks.

Claspers

Paired copulatory structures in male sharks formed by backward extensions of the pelvic fin basal skeleton.

Whale shark

The largest shark species and non-mammalian vertebrate, reaching 41-46 ft in length and 47,000-66,000 lbs in weight.

Filter-feeding sharks

The three planktivorous shark species: whale sharks, basking sharks, and megamouth sharks.

Great White Shark max size

Reaches maximum sizes exceeding 20 feet in total length and weighing over 7,000 lbs.

Squalamine

A broad-spectrum steroidal antibiotic found in sharks that acts effectively as a bacteriocide, fungicide, and antiprotozoal.

Cookiecutter shark

A small parasitic shark that uses suctorial lips to seal against prey and rotates to scoop out neat, circular plugs of flesh.

Pristiformes vs. Pristiophoriformes

Sawfishes (Pristiformes) lack rostral barbels, whereas saw sharks (Pristiophoriformes) possess prominent barbels.

Shark retinal rods

Photoreceptors that dominate the shark retina, granting exceptional sensitivity to motion and contrast in dim or murky water.

Shark retinal cones

Photoreceptors responsible for color vision that are scarce or single-type in sharks, causing most to be colorblind.

Subphylum Craniata

Vertebrate group possessing a cranium, neural crest cells, a brain with sense organs, gill slits, and a multi-chambered heart with RBCs, do not have jaws

Heterocercal tail

An asymmetrical caudal fin where the vertebral column bends upward into an elongated upper lobe, generating thrust and lift.

Homocercal tail

A symmetrical caudal fin with equal lobes where the backbone ends at the base, directing thrust purely horizontally.

Somersault effect

The rotational force produced by a heterocercal tail pushing down and back, counteracted by horizontal planing pectoral fins.

Modern Chondrostei

Primitive ray-finned fishes having a secondarily derived cartilaginous skeleton, heterocercal tail, spiral valve, ganoid scales, and spiracles.

Class Actinopterygii

The ray-finned fishes; characterized by fins attached via fin elements, branchiostegal rays, and a single dorsal fin in basal lineages.

Teleostei

An advanced ray-finned fish division comprising approximately 95% of all living fish species.

Weberian Apparatus

A chain of small bones providing a direct physical connection between the gas bladder and the inner ear.

Gill arch components

The functional branchial assembly consisting of the structural gill arch, inner-facing rakers, and outer-facing filaments.

Gill rakers

Projections on the inner curvature of the gill arch that protect filaments from debris and trap food in filter feeders.

Gill filaments

Highly vascularized, delicate strands extending from the outer edge of the gill arch where respiratory gas exchange occurs.

Photophores

Specialized light-producing glandular cell organs found on deep-sea fishes like lantern fish.

Troglobitic fish

Fishes adapted exclusively to subterranean dark caves, showing complete eye loss, reduced pigment, and heightened tactile senses.

Water oxygen solubility factors

The physical relationship where dissolved oxygen concentration in water decreases as both temperature and salinity increase.

Facultative air breathers

Fishes that rely on gills for aquatic breathing but gulp atmospheric air when environmental oxygen becomes depleted.

Obligatory air breathers

Fishes that must regularly breathe atmospheric oxygen to survive and will drown if prevented from surfacing.

Air-breathing organs in fishes

Structures used for atmospheric gas exchange including lungs, vascularized gas bladders, modified gut regions, mouth linings, and skin.

Ram ventilation

Respiration achieved by forward swimming with an open mouth to continuously force water over the gills without active pumping.

Osteichthyes

The broad taxonomic group whose name directly translates to 'bony fishes'.

Dipnoi lungs

Complex lungs in lungfish subdivided into smaller air sacs to increase surface area, homologous to tetrapod lungs.

Dorsal vs. Ventral air-sac evolution

Ventral air-sacs evolved into functional lungs in Sarcopterygii, whereas dorsal air-sacs evolved into buoyancy swim bladders in Actinopterygii.

Class Sarcopterygii

Lobe-finned fishes characterized by fleshy-lobed fins, cosmine-covered scales, and ventral gut outpocketings.

Order Amiiformes

An order of primitive bony fishes represented today by a single living extant species, the Bowfin (Amia calva).