Understanding Sharks and Rays: Skeleton Characteristics
Characteristics of Sharks and Rays
Sharks and rays are cartilaginous fishes with a skeleton made primarily of cartilage. Some of the key characteristics of sharks and rays include:
- Strong jaws lined with teeth
- Body dorsoventrally flattened, fusiform (spindle shaped) with heterocercal tail
- Paired fins
- No swimming bladder or lungs
- Pelvic fins in males often modified to form claspers
- Gill arches internal to gills
- Lateral-line system
- Paired nostrils
- Internal nares absent
- Separate sexes
- Internal fertilization and direct development
- Oviparous, oviparous, or ovoviviparous
Examples of sharks and rays include the Spiny dogfish, Ray (Raja), and Chimaera.
Characteristics of Ray-Finned Fishes
Ray-finned fishes, on the other hand, generally lack paired fins and have some unique characteristics compared to sharks and rays:
- No internal nares
- Air sacks usually function as swimming bladder
- Skeleton usually well ossified
- Blind olfactory sacs (do not open into the mouth)
- Tail homocercal
Examples of ray-finned fishes include Tilapia, Clarias, and Polypterus.
Key Distinction: Sharks and Rays vs. Ray-Finned Fishes
The key distinction between sharks and rays and ray-finned fishes lies in their skeletal composition. While ray-finned fishes have skeletons made of calcified (hard) bones, sharks and rays have skeletons made primarily of cartilage, providing them with a smooth and flexible tissue.
This cartilaginous skeleton allows sharks and rays to move more freely and efficiently in the water, adapting to their aquatic lifestyle. In contrast, the ossified bones of ray-finned fishes provide structural support but may limit their flexibility in movement.
Understanding these skeletal features is essential in differentiating between these two groups of aquatic organisms and illustrates how their unique anatomical adaptations contribute to their survival in their respective habitats.