|
Family Cassidae - helmet and bonnet shells
|
Order |
: |
|
||
Class |
: |
Gastropoda |
||
No. of Genera in Ref. |
: |
|||
No. of Species in Ref. |
: |
|||
Environment |
: |
Fresh : No |
Brackish : No |
Marine : Yes |
||
Aquarium |
: |
|||
First Fossil Record |
: |
|||
Remark |
: |
Shell medium sized to very large, often thick and solid, elongate-ovate to cylindrical or globose in shape, with a large body whorl and rather small, conical spire. Sculpture variable, ranging from nearly smooth to ridged or nodular, with both axial and spiral elements; axial varices sometimes present. Periostracum very weak to absent. Aperture elongate, with a short siphonal canal recurved dorsally. Outer lip thickened, often denticulate inside. Inner lip with a well-developed, usually shield-like callus which may be confined to the columellar area or forms a flange along left side of body whorl. Operculum quite small and thin, corneous, narrowly oval with nucleus near the anterior end, or fan-shaped with nucleus halfway down the inner margin. Head large, with a narrow and short extensible snout and filiform tentacles with the eyes at their outer bases. Foot large, more or less rounded anteriorly and posteriorly, with a thick epidermis. Sand dwelling, slow moving carnivorous animals, ranging from intertidal levels to considerable depths. Feed almost exclusively on echinoderms, sea urchins or starfish, mainly at night and often while both predator and prey are buried in the sand. Cassids first squirt neurotoxic saliva over their prey to paralyse the spines, protected by the thick skin of their foot. Then, the snout of predator is pushed through the unprotected anus, or through a hole rasped by radula in the test of the victim which may also be crusted under the weight of its predator. Sexes separate, fertilization internal; shell of the female frequently larger than that of the male. Eggs laid in large masses of numerous, small horny capsules, forming irregular or cylindrical, tower-like structures. Each capsule contains several hundred eggs, most of which often serve as food for the developing embryos. Hatching gives planktonic larvae, or crawling juveniles, depending upon the species. Cassids are commonly collected for food and their large decorative shells are popular in the shell trade. Some of the larger species are used as raw material for lime or for cameo-carving (Ref. 348). |
||
Etymology |
: |
|||
Division |
: |
|||
Reproductive guild |
: |
|||
Typical activity level |
: |
|||
Main Ref. |
: |
|||
Coordinator |
: |
|||