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In the most primitive gastropods, however, the stomach is a more complex structure. In these species, the hind part of the stomach, where the oesophagus enters, is chitinous, and includes a sorting region lined with cilia. [1] In all gastropods, the portion of the stomach furthest from the oesophagus, called the "style sac", is lined with cilia.
Gastropods have the greatest numbers of named mollusk species. However, estimates of the total number of gastropod species vary widely, depending on cited sources. The number of gastropod species can be ascertained from estimates of the number of described species of Mollusca with accepted names: about 85,000 (minimum 50,000, maximum 120,000). [9]
In many marine gastropods where the siphon is particularly long, the structure of the shell has been modified in order to house and protect the soft tissue of the siphon. This shell modification is known as the siphonal canal. For a gastropod whose shell has an exceptionally long siphonal canal, see Venus comb murex.
The scaly-foot gastropod is an obligate symbiotroph throughout post-settlement life. [24] Throughout its post-larval life, the scaly-foot gastropod obtains all of its nutrition from the chemoautotrophy of its endosymbiotic bacteria. [26] [24] The scaly-foot gastropod is neither a filter-feeder [5] [24] nor uses other mechanisms for feeding. [5]
Some gastropods, for example the freshwater apple snails (family Ampullariidae) [7] and marine species of genus Strombus [8] can completely regenerate their eyes. The gastropods in both of these families have lens eyes. Morphological sequence of different types of multicellular eyes exemplified by gastropod eyes: [9]
The gastropod shell is part of the body of many gastropods, including snails, a kind of mollusc. The shell is an exoskeleton , which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium storage.
The excretory system of gastropods removes nitrogenous waste and maintains the internal water balance of these creatures, commonly referred to as snails and slugs. The primary organ of excretion is a nephridium. Drawing of excretory system of Lymnaea meridensis; renal tube and ureter in renal region extending between pericardium and mantle collar
In gastropods in many ancient lineages, the gills are bipectinate, having an overall shape that is similar to a bird's feather, with narrow filaments projecting either side of a central stalk. Gastropods such as abalone and keyhole limpets have two gills, which is believed to be the arrangement in the earliest fossil gastropods. The water ...