title: Studies on the biology and trematode infections of Bithynia tentaculata (Linn.) Prosobranchiaa : gastropoda
Creators: name: Sawi Ali, Faisal
Publisher: name: University of Liverpool Repository
Year: 2023

description: The present investigation on the biology of Bithynia tentaculata has two aims. Firstly to report on the life cycle, growth, reproduction and other aspects of the biology of this snail, and secondly to identify the larval trematode infection of the snail and to report on the incidence, seasonal variation and the development of these infections. The study area was a small artificial pond in Sefton Park, Liverpool. The biology of the snail was investigated by regular sampling of the habitat for 22 months, the snails were measured and the breeding activity was assessed. Laboratory experiments were performed on the growth, reproduction and natural diet of the snail. The larval trematode . infection of the snail was investigated and experimental infections were made. A monthly survey of the incidence of these infections was made for 13 months. The following results were obtained on the biology of the snail; 1) Growth of the snails practically ceases in the winter and the wintering population resumes growth in the spring.. The new .'F generation of snails äppears in June and growth is rapid during the summer. 2) The snails begin to breed in mid-April and active breeding is limited to April-June, but sporadic egg-laying occurs in July and August. 3) There is a minimum breeding size of the snails which varied from one year to the next depending on the growth rate. In addition to size, there is a minimum period of five to six months for maturity (oviposition) of the snails. 4) The onset of egg-laying is controlled by temperature, and the snails did not oviposit at 10-120C. 5) The snails show optimal growth when fed on detritus, and algae, growth is retarded on a diet of detritus alone. 6) Winter and unfavourable conditions cause aggregation of " the snails, and organic pollution is detrimental to their distribution within the habitat. 7) The life span of Bithynia tentaculata is about 14 to 23 months, and possibly few survive to breed for a second season. Results obtained on trematode infections of Bithynia tentaculata show the following:. 1) Six species of cercariae infect the snail, a Monostome cercaria, three Gymnocephalous cercariae, a Xiphidiocercaria and a pharyngeal longifurcate monoctome Furcocercaria. ti 2) One of these cercariae (i. e, Cercaria helvetica XIX) is a first record in British freshwater. Existing descriptions of some of the cercariae are expanded, and new descriptions of some developmental stages. are added. 3) The life cycle of Notocotylus imbricatus is traced and metacercarial infectivity is demonstrated soon afer encystment. The development of Notocotylus imbricatus in the snail host is followed and descriptions of the developmental stales are presented. 4) Multiple cercariae infections are generally rare, yet , It certain combinations of double infections are more frequent than expected. 5) The total cercariae infection of the snail, as well as four individual species of cercariae, show biannual peaks of incidence. No biannual peaks of metacercariae infections were detected. 6) Many cercariae infections enter the new generation of snails in their first summer. Some of these infections may mature in the same season, but most of the infections are carried through the winter in an immature state. New infections enter the snails in the spring, but few infections enter the snails in their second summer of life.