Definitional overview Biology of Fishes

Illicium

The "fishing rod" or modified dorsal fin spine in anglerfish

Esca

The "bait" or fleshy groeth at the tip of the illicium used to lure prey for anglerfish

Bioaccumulation

The process where toxins build up in the tissues of tish over time after consuming contaminated plants or smaller organisms

Bycatch

The incidental capture of non-target species (sharks and rays) while fishing for a different specific species

Phenotypic plasticity

The ability of one genotype (DNA) to produce more than one phenotype (physical appearance) when exposed to different environments.

Hagfish

Craniata < Agnatha < mentioned group

Lampreys

Craniata < Vertebrata < mentioned group

Chimaeras

Craniata < Vertebrata < Gnathostomata < Chondrichthyes < Holocephali < mentioned group

Sharks and Rays

Craniata < Vertebrata < Gnathostomata < Chondrichthyes < Elasmobranchs < mentioned group

Tetrapods

Craniata < Vertebrata < Gnathostomata < Osteichthyes < Sarcopterygii < mentioned group

Coelacanths

Craniata < Vertebrata < Gnathostomata < Osteichthyes < Sarcopterygii < mentioned group

Lungfishes

Craniata < Vertebrata < Gnathostomata < Osteichthyes < Sarcopterygii < mentioned group

Bichirs

Craniata < Vertebrata < Gnathostomata < Osteichthyes < Actinopterygii < Cladistia < mentioned group

Sturgeons

Craniata < Vertebrata < Gnathostomata < Osteichthyes < Actinopterygii < Chondrostei < mentioned group

Gars

Craniata < Vertebrata < Gnathostomata < Osteichthyes < Actinopterygii < Neopterygii < Haleocomorphi < mentioned group

Bowfin

Craniata < Vertebrata < Gnathostomata < Osteichthyes < Actinopterygii < Neopterygii < Halcomorphi < mentioned group

Teleosts

Craniata < Vertebrata < Gnathostomata < Osteichthyes < Actinopterygii < Neopterygii < mentioned group

Ossified

Bone that has been hardened by the deposition of calcium carbonate or other phosphate minerals (defining trait of Osteichthyes)

Calcified cartilage

Cartilage that is strengthened by calcium but lacks the structure of true bone ( found in Chondrichthyes)

Palatoquadrate cartilage

The upper jaw element in cartilaginous fishes; not fused to the cranium (unique to Chondrichthyes)

Ceratotrichia

Stiff, unsegmented, and unbranched fin rays composed of keratin ( specific to sharks, skates, and rays)

Lepidotrichia

Segmented, branched bony fin rays (defining Actinopterygii or Ray-finned fishes)

Placoid Scales

Small, tooth- like scales (dermal denticles) that reduce drag and provide protection (found on sharks and rays)

Heterocercal Tail

A tail fin where the upper lobe is significantly larger than the lower lobe, and the vertebral column extends into the upper lobe ( found in sharks, rays, sturgeon, and bichirs)

Homocercal tail

A symmetrical tail fin where the vertebrae end at the base of the tail (found in most Teleosts)

Metapterygial Axis

A central bony axis in the fin from which other bones or rays radiate

Claspers

Modified pelvic fins used by males for internal fertilization (male Chondrichthyes)

Spiracle

A modified first gill slit located behind the eye that allows fish to take in oxygenated water while resting on the bottom (some sharks and rays)

tentaculum

A unique frontal tentaculum ( a cephalic clasper) on the head of males used during mating (specific to chimaeras Holocephalii )

Obligate air-breather

An organism that must breathe atmospheric air to survive, regardless of water oxygen levels (lungfishes)

Agnatha

Superclass of jawless fish (hagfishes and lampreys)

Gnathostomata

The group of vertebrates that possess jawed mouths

Slime glands

Specialized glands that produce massive amounts of mucus as a predatory defense (primary defense of hagfishes)

Lobed fins

A muscular fleshy appendage supported by the central bony axis that includes bones homologous to the human arm ( humerus, radius, and ulna) ( found in lungfishes, coelacanths, and ancient tetrapods)

Chondrichthyes

Fishes with skeletons made entirely of cartilage rather than hard bone (sharks, rays, and skates)

Osteichthyes

The group of "bony fishes" that have skeletons primarily made of bone tissue

Cellular bone

Bone that contains living cells (osteocytes). These cells sense strain and help the fish repair or remold its skeleton

acellular bone

Bone that lacks living cells. ( found in most advanced types of teleosts, swordfish, and marlin)

Ganoid scales

Hard, diamond- shaped scales that do not overlap. Provide heavy armor like protection ( gars and bichirs)

Cycloid scales

Smooth thin and translucent scales that overall like shingles on a roof. Allow for flexibility and maneuverability ( salmon and carp)

Ctenoid scales

Similar to cycloid scales but they have tiny comb-like teeth (cteni) on the edges. Rough surface reduces drag (perch)

Protocercal

A primitive, pointed tail where the spine extends straight to the tip (hagfish)

Axial skeleton

The core of the fish, including the skull, vertebral column (spine) and ribs

appendicular skeleton

The parts attached to the core specifically the find and the girdles (internal supports) that hold them

Myoseptal tendons

Strong connective tissues that carry the load of swimming muscles directly to the tail ( short fin mako - only the tail oscillates)

Chrondrocranium

A skull made of a single box of cartilage

Tesserae

Tiny calcified tiles that strengthen the cartilaginous jaws of sharks, allowing them to bite through prey without heavy bony skull

Osteons

Circular, tube-like structures in bone.( he,p to make the bill (rostrum) of blue marlin tough

Meckel's cartilage

The piece of cartilage that forms the lower jaw in sharks and rays

Reynolds number

A dimensionless value representing the ratio of inertial forces to fiscal forces. It predicts whether water flow will be smooth or chaotic

Low Re

Dominated by viscosity ( bacteria or ciliates)

High Re

Dominated by inertia ( blue whales or fast moving fish)

Laminar flow

Water particles move in parallel, smooth layers. This occurs at lower Re

Turbulent flow

Chaotic swirling water movement that increases resistance

Drag

The force acting opposite to the relative motion of the fish

Frictional drag

Resistance caused by water to the fish surface (minimized by scales and mucus)

Pressure drag

Resistance caused by the displacement of water as the fish moves through it (minimized by fusiform or streamlined body shape)

Gas Bladder ( Swim bladder)

A gas filled organ used by bony fishes to control buoyancy

Physostimoous

Fish with a connection (pneumatic duct) between the gut and the swim bladder

Physoclistous

Fish that lack this connection And regulate gas via the blood/ gas gland

Static lift (lipids)

Using low-density oils to stay afloat p. (basking shark has a liver that is 20x30% of its body weight filled with oil

Dynamic lift

Created by the angle of attack of wing like pectoral fins

White muscles

Large diameter low vascularizarion anaerobic (burst Swimming fatigues quickly)

Red muscle

High myoglobin, high vascularized, aerobic (sustained swimming fatigue resistant)

Pink muscle

Intermediate structure sustained intermediate speeds

Thunniform

High speed movement where thrust is generated almost entirely by the caudal fin (tuna)

Rete Mirabile

A net of blood vessels that act as a countercurrent heat exchanger. (Tunas, lamnid, sharks) it keeps muscles warmer than the surrounding water and increases power output

Fusiform

A spindle shaped body ( tapered at both ends) that is most efficient shape for reducing pressure drag

Aspect ratio

The ratio of a fins height to its width. A high aspect ratio tall tin fins is found in high speed efficient swimmers like tuna

Caudal peduncle

The narrow neck of the body just before the tail fin. Fast fish have lateral keels here to reduce turbulence

Angulliform

Very efficient swimmers at low speeds or designed for moving across a substrate

Globiform

Substrate specialists, with some capable of self-inflation

Sagittiform

Ambush predators with high acceleration

Compressiform

Are highly maneuverable

Depressiform

Closely associated the substrate often partially covered with bottom materials and a generally ambush predators

Generating thrust: BCF

Body and/ or caudal fin locomotion

Generating thrust: MPF

Median/ and or paired fish locomotion

Neutral buoyancy

A state where a fish's density is equal to the surrounding water. The fish neither sinks nor rises and can maintain its position with little to no energy expenditure

Negative buoyancy

Occurs when the force of gravity outweighs the force of lift ( benthic fish are naturally negatively buoyant)

Positive buoyancy

Occurs when the force of lift/ buoyancy outweighs gravity, causing the fish to rise

Static lift

Lift generated by low-density inclusions (like oil) that does not require movement (pelagic elasmobranchs use oily livers to provide static lift)

Hydrodynamic lift

Lift generated by the movement of water over a surface often requiring the fish to keep swimming

Bernoulli's principle

Pressure differences created by the angle of attack

Gas gland

A specialized tissue associated with the swim bladder that secretes lactic acid and CO2 into the blood to trigger gas release into the bladder

oval

A modified vascularized area in physoclistous fish where gases can be reabsorbed back into the blood to reduce buoyancy

Salting out

A physical phenomenon where adding a solute (like salt or ions) to a solution decreases the solubility of gases causing them to precipitate out

Bohr effect

A decrease in the oxygen- binding affinity of hemoglobin in response to lower pH (acidic conditions). This is a standard response in all vertebrates

Root effect

A specialized version of the Bohr effect found only in fish. It involves a decrease in both the oxygen binding affinity and the total oxygen carrying capacity of hemoglobin at low pH. (Allows fish to dump oxygen into the swim bladder even against high pressure)

Countercurrent exchange

A mechanism where two fluids flow in opposite directions to maintain a concentration gradient along their entire length ( used in the rete mirabile to maintain high gas pressure and acidic conditions near the gas gland)

Barotrauma

Tissue damage or injury caused by rapid changes in environmental pressure ( fish moves up the water column too quickly without releasing gas from the swim bladder, so it over expands and causes injury)

Glycolysis

The gas gland metabolizes glucose producing lactic acid

Dissociation

Lactic acid becomes lactate + and H+ lowering the blood pH

Heterotrophs

Organisms that cannot produce their own food and must take in organic substances ( nutrients and oxygen) to survive.

Hypoxia

A condition where oxygen levels are below the normoxic (normal) range making it difficult for fish to breathe

Anoxia

A total lack of oxygen in the environment

Partial pressure

The measure of oxygen concentration in water or air. Oxygen is much more limited in water (1%) compared to air (21%)

Operculum

The bony flap that covers and protects the gills in bony fishes

Gill arches (Holobranchs)

The structural backbones of the gills that support the filaments

Filaments

the red fleshy parts of the gills

Lamellae

Are the tiny plate like structures on the filaments where actual gas exchange occurs