| The classification system has been widely accepted that Onchidiidae belongs toMollusca, Gastropoda, Pulmonata, Stylommatophora, Onchidioidea, Onchidiidae.Onchidiidae is one of the higher clades of pulmonates. Its systematic is in a state ofconfusion; and the internal anatomy of most species is still largely unknown. Aftermany years of succession, the classification of Onchidiidae including six genera(Onchidium, Platevindex, Paraoncidium, Peronia, Onchidella, Onchidina) has beenwidely accepted. The name of most onchidiid is unknown, and the diversity of onchidiidis still confused. So it’s more difficult to discover new species. The research ofsystematic of onchidiidae has been carried out by Chinese and US experts since recentyears.According to the record, there are4genera in China (Onchidium, Platevindex,Paraoncidium, Peronia). Onchidiid are fostered in laboratory. All anatomicalobservations were made under a dissecting microscope and drawn with a camera lucida.In addition, dissected organs were prepared for scanning electron microscopy (SEM)using critical point drying. Each species of onchidiid has its characteristic. Dendritic gillis the characteristic of Peronia verruculatum that are different from other species. Boththe color, number of dorsal eyes, location of female aperture and pneumostome arerange from different species.Dissecting the degistive gland, we can find that the sytle of the intestion, the rectalgland present of absent, the consist of the stomach usully can be used in theclassification of onchidiid.The intestine of the Peronia verruculatum is type Ⅰ,Onchidium struma is type Ⅲ, Paraoncidium reevesii and Platevindex mortoni are typeⅡ. The rectal gland of O.struma is well developed and highly coiled; P.mortoni is welldeveloped and not coiled. The rectal gland are absent in P.verruculatum and P.reevesii.Onchidiid are hermaphrodite, There is on accessory in Platevindex mortoni thatmake it differ from the other three species. The penis of the Onchidium struma is spiral,and the other three are straight. The beginning of the flagellum of Peronia verruculate and Paraoncidium reevesii is a large expanded structure with thick wall look like acurved moon. The flagellum of the P.verruculate and O.struma are coiled, and that ofthe P.reevesii is snaking trail and not coiled.The penis is protected by the penial sheath, with a rigid stalk covered with hooks.The base of the hooks are round, each of the point of the hooks is head down. The entirestalk of Onchidium struma is covered with hooks, the hooks are conical.The radula of onchidiid with4genera which contain10groups are compared onthe basis of scanning electron microscopic observation and morphologicalmeasurements. Results indicate the radula is flaky and developed. Each row of theradula in the buccal mass is consisted of a rachidian too th and two almost symmetrichalf rows of lateral teeth, without marginal teeth. The thirty row of the radula wasmeasured for the standard. Radular formula of Onchidium struma varies from75:1:75to107:1:107, Peronia verruculate varies from52:1:52to79:1:79, Platevindex mortonivaries from89:1:89to105:1:105, Paraoncidium reevesii varies from66:1:66to94:1:94among sampling individuals. The base of the rachidian teeth and the first cusp of therachidian teeth showed significant interspecific differences in morphology. It can beused for species identification and taxonomy not only interspecific but also within thespecies to in onchidiid.Perpendicular plate of polyacrylamide gel electrophoresis was used to investigatetwo isozymes (SOD、EST) in2kinds of tissues (foot, hepatopancreas). The variation ofelectrophoresis patterns of EST and SOD were parallel to the morphologicalcategorizing: same species had common characteristic bands although variant bandswere found in some individuals. The characteristic electrophoretograms of SOD andEST could be applied as molecular markers to identify the different species inOnchidiid.Onchidella sp. is new discovered in Chinese mailand, it differ from the4geners inchina. |
PDF Full Text Request