2026 Bony Fish Vocabulary

Flashcards covering external anatomy, scales, internal digestive and respiratory structures, circulation pathway, and reproductive terminology of bony fishes (Osteichthyes).

Osteichthyes

The taxonomic class comprising bony fishes within the phylum Chordata.

Dorsal and Anal Fins

Unpaired fins that act as stabilizers to prevent rolling and yawing (side-to-side motion) while swimming.

Pectoral and Pelvic Fins

Paired fins used primarily for steering, fine movement, balancing, and dynamic braking.

Caudal Fin

The tail fin serving as the primary source of forward propulsion, which is homocercal in most bony fish.

Caudal Peduncle

The tapered region packed with myomeres that attaches the tail fin to the fish's body.

Scales

Protective bony structures embedded in the skin of fish.

Cycloid Scales

Thin and flexible, round to oval-shaped overlapping structures featuring smooth posterior margins and visible growth rings.

Ctenoid Scales

Thin and flexible, round to oval-shaped overlapping structures possessing tiny comb-like projections called ctenii along their posterior margins.

Ctenii

Tiny comb-like projections located along the posterior margins of ctenoid scales.

Ganoid Scales

Thick, non-overlapping diamond-shaped structures that interlock like armor.

Placoid Scales

A type of scale exclusive to cartilaginous fish.

Buccal Cavity

The mouth or oral cavity; the space at the beginning of the digestive tract where food enters the body.

Liver

An organ that produces bile to aid in fat digestion and detoxifies metabolic waste; primary system association is digestive.

Gallbladder

A sac-like organ that stores and concentrates bile before releasing it into the intestine; primary system association is digestive.

Hepatopancreas

A composite organ fulfilling functions of both liver and pancreas by secreting digestive enzymes and bile; primary system association is digestive.

Spleen

An organ that recycles old red blood cells and produces white blood cells; primary system association is circulatory/immune.

Rectum

The digestive structure that collects leftover waste before it leaves the body.

Anus

The final opening where solid waste exits the body.

Gill Rakers

Firm comb-like projections that strain the water to remove debris and food particles.

Gill Filaments

Very vascular thread-like structures in the gill assembly.

Gill Arches

The bony support structures of the gills.

Lamellae

Plate-like structures that serve as the actual location of gas exchange in bony fishes.

Single Circulation Pathway

A circulatory pattern in bony fishes where deoxygenated blood passes through the heart once during each complete circuit of the body.

Venous Blood

Blood that moves towards the heart.

Arterial Blood

Blood that moves away from the heart.

Gametes

Reproductive cells.

Gonads

Reproductive organs.

Oviparous

The reproductive strategy characteristic of most bony fishes, in which eggs are spawned externally.