Aquatic Anatomy and Fin Structure Quiz

Fish Anatomy

• Fish anatomy is vital to understand fish physiology and potential abnormalities/diseases.
• Fish are cold-blooded aquatic vertebrates, their body temperature varies with the surrounding water temperature.
• Fish breathe via gills and move using fins.

Fish Classification

• Fish are classified based on the nature of their skeletal structure,
• Bony fish (Teleosts): Have bony skeletons. This group includes most known fish species. Examples: Tilapia nilotica (Nile tilapia), Catfish, Carp, Bass, Trout.
• Cartilaginous fish (Chondrosts): Have cartilaginous skeletons. Examples: Sharks, Rays, Skates.
• Jawless fish: A separate group with no jaws. Examples: Hagfish, Lampreys (eel-shaped, slime-producing marine fish).

Fish Classification by Habitat

• Freshwater fish: Live in fresh water. Examples: Tilapia, Carp, Catfish
• Marine fish: Live in saltwater. Examples: Shark, Seabass, Seabream
• Brackish water fish: Live in water with moderate salinity. Examples: Mugil, Salmon, Eel.

Fish Classification by Migration

• Non-migratory fish: Do not migrate. Example: Tilapia
• Migratory fish: Migrate for spawning. Examples: Salmon, Eel

Fish Classification According to Diet

• Herbivorous: Eats plants and algae. Example: Tilapia
• Carnivorous: Eats meat and other animals. Example: Shark
• Omnivorous: Eats both plants and animals. Examples: River carpsucker

External Features of Fish

• The fish body is divided into three regions: head, trunk, and tail.
• The head includes the snout (region from eye to lips), occiput (region from eye to gill cover), nuchal region (from occiput to dorsal fin) and isthmus (region between the two gill covers).
• The body of the fish consists of three regions (head, trunk, and tail).

Parts of the Head

• Snout: The region from the eye to the lips.
• Occiput: The region from the eye to the beginning of the gill cover.
• Nuchal region: The region from the occiput to the beginning of the dorsal fin.
• Isthmus: The region between and below the two gill covers.

Fish Length Measurements

• The fish is measured in several ways such as: snout length, body depth, standard, and fork lengths.

Parts of the Head (continued)

• Mouth: (Detailed description of mouth shapes found in various kinds of fish is elsewhere)
• Nostrils (Nares): External openings of the nose, located on the dorsal surface of the head (snout region). They lead to a nasal sac and enable the fish to detect chemicals.
• Eyes: Present in a bony cavity (myodome); no eyelids in bony fish, but one in cartilaginous fish. The eye lens is round.
• Ear: Only inner ear; has a sensitive structure (otolith) that helps with balance and hearing.
• Barbels: Sensory appendages near the mouth with a cartilaginous core and skin covering (found in catfish and carp). Used for detecting food and other stimuli.
• Gill cover (Operculum): A bony plate covering the gills in bony fish. It protects and supports the gill filaments.
• Branchiostegal membrane: Connects the two opercula ventrally and covers the gill opening ventrally. It aids in stability.

Trunk Regions

• Breast region: A triangular region caudal to the isthmus.
• Abdomen (belly): Extends from the pelvic fin to the beginning of the anal fin.
• It contains openings like the anus and vent or urogenital opening.

Tail Regions

• Tail (caudal) peduncle: The fleshy part between the anal fin and tail fin (site of blood sampling).
• Tail fin: Described elsewhere

Lateral Line System

• A system of sense organs made up of hair-like sensory units (neuromasts) that're located in the head (forming a sensory organ) and on the side of the trunk and tail.
• The lateral line opens to the water through pores. This allows the fish to detect water currents, vibrations, and other small changes in their environment.

Fish Skeleton

• Axial skeleton: Consists of the skull, vertebral column, pectoral girdle, and pelvic girdle
• Appendicular skeleton: Consists of fish fins
• Dermal skeleton: Consists of the scales

Fish Scales

• Placoid scales: Small scales with pointed ends resembling teeth (found in sharks).
• Ganoid scales: Rhomboid scales covered with a layer (found in gar)
• Cycloid scales: Almost circular with smooth edges (found in salmon).
• Ctenoid scales: Round with serrated edges (found in perch).

Fish Skin

• The primary barrier against the environment.
• Slime protects from pathogens and injury and helps decrease friction and loss of body fluids
• Contains mucous glands, pigmented cells giving the fish color, and alarm cells
• Forms pockets for scales

Active Locomotors System

• Red muscles: Narrow, contain fat and myoglobin, aerobic metabolism, used for slow, sustained movement.
• White muscles:: Broad, lack fat, and myoglobin, anaerobic metabolism, used for rapid, short movement. They are predominant in the bulk of the fish body.

Body Shape & Form of Fish

• Fish body shapes are adapted for different swimming styles. Some common shapes include fusiform, compressed, depresse, leptocephalii, eel-like, thread-like, ribbon-like.

The Digestive System of Fish

• Details on mouth types (e.g., superior, vertical, inferior, terminal, subterminal), and shapes (e.g., opposing jaws, half-beak, sword-like, needle-like)
• Description of teeth (e.g., carnivorous, herbivorous, bony, cartilaginous)
• The digestive system includes the mouth, teeth, tongue, pharynx, esophagus, stomach (some fish lack a stomach), pyloric caecae, intestines.

The Liver

• Color varies depending on diet
• Number of lobes varies depending on fish type
• Functions in bile production, digestion, and other metabolic processes.

The Pancreas

• Located in places like the mesentery, and pyloric caecae, unlike in mammals where it's a single organ.
• Secretes digestive enzymes into the duodenum

The Peritoneum

• A thin membrane lining the abdomen protects internal organs. The two layers are black especially in herbivorous bony fishes.

The Urogenital System

• Kidneys: These are mixed organs with a role in blood formation (cranial) and urine production (caudal).
• Ureters: These tubes carry urine from the kidneys to the urinary bladder (if present) and then out of the body. Various locations of each part Note on different function for cranial and caudal kidneys.

The Reproductive System

• Testes and Ovaries: Location within the coelomic cavity
• Sperm storage and Egg discharge Details on processes like spawning. Note on differences in male and female sex organs

The Gills

• Located between the buccal cavity and opercular cavity
• Functions: respiration, osmoregulation, and excretion.
• Gill rakers: sieve to prevent ingestion of small particles.
• Gill arches: provide support, contain arteries (afferent and efferent).
• Gill lamellae (filaments): thin structures that increase the surface area for gas exchange. This is where oxygenation/deoxygenation occurs.

Swim Bladder

• Location, types (physoclist, physostomic, single, double chambered)
• Pneumatic duct present in some fish types
• Function: buoyancy control, sound production, excretion and depth determination.

How Fish Swim

• Techniques for propulsion and maintaining buoyancy
• The role of the swim bladder and myomeres.
• The support of the fins and muscles for maintaining position and direction

Fish Cardiovascular System

• Heart structure (sinus venosus, atrium, ventricle, bulbus arteriosus) and function.
• Blood vessels (arteries and veins) and their function.