Considering just this aspect, they appear to be evolutionarily closer to nematodes than to annelids. Pelecypoda or Lamellibranchiate or Bivalvia Gk. The mantle cavity is modified in different groups of Molluscs. The epithelial lining of the pericardium usually contains glandular tissue and constitutes the pericardial gland. Watch this of mussels feeding.
Sexes separate; external sexual dimorphism in some species. By the modification of foot, they can creep, leap, burrow, float or swim. Indistinct head and a radula, jaws, eyes and tentacles absent. The ventricles are located on the lateral side of the hindgut and continue as a single aorta. These findings have led researchers to study conotoxins for possible medical applications.
Dentalidae: i Comparatively larger and stronger species. Habitat: Marine, found in Australian oceans, from shallow water 200 m to mostly in deep water 3000 m. The shell is mostly located externally, although a few forms with internal shell. The key innovation found in the species of the phylum Annelida is the coelom, an internal body cavity completely covered by the mesoderm, a feature also present in arthropods, molluscs, echinoderms and chordates. The carbonate of lime from the circulating blood is separated by the epithelial cells of the mantle edge. Nuculoida: i Shell small to triangular and equivalve. In hermaphroditic Streptoneura, single hermaphroditic gland ovotestis is present.
Classification with Characters : Class 1. Reproduction in cephalopods is different from other mollusks in that the egg hatches to produce a juvenile adult without undergoing the trochophore and veliger larval stages. Like all other organ systems, the excretory system in Gastropods exhibits great diversities. Habitat: Mostly terrestrial or freshwater, a few are marine. Lankester 1901-1909 , Pelseneer 1906 first divided the phylum into 5 classes: i Amphineura, ii Scaphopoda, iii Gastropoda, iv Pelecypoda and v Cephalopoda. Incirrata: i 8 arms with suckers present.
As regards the existence of renal organs in Solenogastres there exist two opposite and contradictory views. Examples: Jewel boxes Pseudochama, Chama. A ventral muscular foot is present which helps in locomotion and may be secondarily modified in some forms. Respiratory system: cutaneous or branchial. This includes digestive, nervous, excretory, reproductive, and respiratory systems.
But in Aplysia, Lamellaria the shell is completely enclosed by mantle. In all Opisthobranchia excepting Acteon and in all Pulmonata excepting Amphibola operculum is absent. Eyespots are absent in these animals. In other Gastropods typical molluscan larval stages are observed and the larvae may possess certain special organs such as the contractile sinuses blister-like extension of the integument assisting larval circulation and the larval kidneys. Head incopspicuous, but eyes and tentacles absent.
These muscles originate from the shell and extend to the median wall of the pallial groove. Unless you thought of an octopus or one of the insects in the rainforest pavilion, chances are you thought of an animal in the phylum Chordata. The two types of larval forms, viz. Like humans, many animals lose some of these features as they develop. In the artificial production of pearls, a small fragment of shell covered with mantle pieces is inserted between the shell and the mantle of an oyster and a pearl is formed around the graft. Multiple gills 6-80 pairs located in the mantle grove.
The diversity of the arthropods comes from their ability to adapt their hard into almost any shape or function. Mostly non-marine gastropods, some bivalves and cephalopods are hermaphrodites. Number and Size of Molluscs: The phylum Mollusca is noted for its numerical abundance. Paludina possesses two kidneys in embryonic stage, but in course of development, the kidney of the right side disappears. For example, these toxins may be used to induce paralysis in muscles in specific health applications, similar to the use of botulinum toxin. These particles trigger a defense process in the organism and are gradually covered by layers of calcium carbonate secreted by the oyster, thus producing pearls.