Fish Skeletal System

Fish Skeletal System

• The exoskeleton is the stable outer shell of an organism.
• The endoskeleton is a support structure inside the body.
• The axial skeleton includes the skull, vertebrae, and ribs.
• The appendicular skeleton includes pectoral and pelvic girdles.
• The notochord acts as the primary axial support, replacing the vertebral column.
• Arcualia are small cartilaginous structures surrounding the notochord.
• The otic capsule houses the inner ear and aids in balance and orientation.
• The branchial arch supports the gill region, allowing effective respiration.
• Cartilaginous fish have flexible skeletons made of cartilage instead of bone.

Bony Fish

• Filled with gas to regulate buoyancy, bony fish feature a swim bladder.
• Bony fish skeletons consist of 150 bones.
• The vertebral column, jaw, ribs, cranium and intramuscular bones are all part of the 150 bones making up the bony fish skeleton.
• Scales are part of the endoskeleton.
• The skull is a double structure consisting of one box of bone enclosed by another.
• In cartilaginous fishes, the structure that forms the skull is the chondrocranium.
• In bony fish, the neurocranium replaces the chondrocranium.
• The branchial arc forms the splanchnocranium, also known as the visceral skeleton
• The dermatocranium is composed of dermal roofing bones.
• The vertebral column has a large spool-shaped structure called the centrum.
• The first two trunk vertebrae are modified and lack ribs.
• The tail vertebrae possess a ventral portion that forms a hemal arch.
• The hemal arch surrounds the blood vessels.
• Pectoral fins attach to a bony girdle with fused elements and a skull.
• The pelvic fins attach to the pelvic girdle, composed of two pelvic plates fused along the midline.

Functions of Fins and Vertebrae

• The caudal fin ray provides stability and propulsion for steering and moving forward.
• The hypural supports the caudal fin and aids in tail movement and propulsion.
• Vertebrae function as the backbone, providing structural support and flexibility.
• The neural spine protects the spinal cord and serves as an attachment point for muscles.
• The hemal spine protects blood vessels and serves as a muscle attachment site.
• The ray of the posterior dorsal fin supports the posterior section of the dorsal fin for stability.
• The ray of the anterior dorsal fin supports the anterior section of the dorsal fin for stability.
• The radial cartilage provides flexibility and support to the fins.

Skull

• The operculum covers and protects the gills for efficient respiration.
• The skull houses and protects the brain and sensory organs.
• The upper jaw captures prey for manipulation.
• The lower jaw grasps and processes food.
• The clavicle supports the pectoral girdle and aids in fin movement.
• The pelvic girdle supports pelvic fins and allows for maneuverability.
• The pelvic fin ray provides stability and directional control.
• The pectoral fin ray allows for maneuverability, stopping, and hovering.
• Ribs protect internal organs and provide structural support.
• The anal fin ray provides stability and prevents rolling.

Bones of the Fish Skull

• Supraoccipital Crest: muscle attachment; skull structural support
• Parietal: protects brain; cranial roof.
• Operculum: bony plate that protect gills; aids in respiration.
• Suboperculum: secondary protective structure for gills
• Supracleithrum: connects skull to pectoral girdle, aiding fin movement
• Cleithrum provides structural support and is an attachment point for muscles
• Preoperculum supports the operculum and is involved in jaw movement
• Scapula supports pectoral fin movement
• Basalia supports fin structure and assists in movement
• Pelvis connects to pelvic fins
• Interoperculum assists operculum movement for respiration
• Branchiostegal Rays support gill membranes and aid in respiration
• Quadrate connects the jaw to the skull and enables jaw movement
• Angular facilitates jaw articulation and supports jaw muscles
• Dentary is the lower jawbone used for feeding and prey capture
• Maxilla is part of the upper jaw and assists in food intake
• Endopterygoid supports the roof of the mouth and aids in jaw movement
• Premaxilla forms part of the upper jaw and holds teeth
• Lacrimal is a small bone near the eye providing structural support
• Ethmoid (Nasal) supports the nasal cavity and provides sensory function
• Frontal forms part of the skull and protects the brain
• Parasphenoid provides structural support to the skull and braincase
• Metapterygoid connects to the jaw and helps in mouth movements