What is the skeleton of a nurse shark made of?
The skeleton of a nurse shark contains no bone tissue and relies on cartilage to support its body throughout life. This structural difference separates them from bony fish like the cod or tuna.
Questions about Chondrichthyes
Short answers, pulled from the story.
When did jawed vertebrates first appear in the fossil record?
Fossil evidence from Guizhou, China dates back 439 million years to the early Silurian period. Scientists discovered Qianodus and Fanjingshania among these ancient remains as the oldest unambiguous jawed vertebrates known to science.
How many gill clefts do Elasmobranchii members possess?
Members of this group possess five to seven pairs of gill clefts opening individually to the exterior. Males have a grooved inner margin on each pelvic fin called a clasper for sperm transmission.
Where do red blood cells form in cartilaginous fishes?
Red blood cells form in the spleen rather than inside bones because the lack of bone marrow means they must develop elsewhere. Specialized tissues called the epigonal organ and Leydig's organ assist in immune function.
What percentage of live bearing species exhibit capture-induced parturition?
Capture-induced premature birth happens in at least 12% of live bearing species. Eighty-eight species have been documented exhibiting this response so far when sharks or rays are fished.