Abstract
This paper focuses on the geographical distribution and habitats of Gyraulus connollyi, snail intermediate host of intestinal flukes of the family Echinostomatidae as reflected by the 969 collection sites on record in the database of the National Freshwater Snail Collection (NFSC) of South Africa. The presence of this species was reported from 13 different types of water-bodies, however, the highest percentage by far was collected in streams and rivers and in habitats of which the water was described as perennial, clear and fresh. A predominantly stony substratum and the presence of vegetation were also reported for the majority of habitats. The effect size was calculated for each variable to determine its importance for the occurrence of this species. An integrated decision tree constructed from the data indicated that temperature, altitude and type of water-body were the most important of the factors evaluated that could have an effect on the geographical distribution of this species. This was supported by the effect size values calculated for each variable. A temperature index calculated for each species in the database ranked G. connollyi seventh out of 53 due to its association with low temperatures. Although human echinostomosis has not yet been diagnosed in Africa, concern is expressed that G. connollyi is able to serve as first intermediate host in the transmission of echinostomosis.
Highlights
This paper focuses on the geographical distribution and habitats of Gyraulus connollyi, snail intermediate host of intestinal flukes of the family Echinostomatidae as reflected by the 969 collection sites on record in the database of the National Freshwater Snail Collection (NFSC) of South Africa
Die getal lokusse waarin die vindplekke geleë is, is in intervalle van gemiddelde jaarlikse lugtemperatuur en reënval, asook gemiddelde hoogte bo seevlak ingedeel om die voorkomsfrekwensie in spesifieke intervalle te illustreer. ’n Temperatuurindeks is vir elke spesie in die databasis aan die hand van die voorkomsfrekwensie in die geselekteerde temperatuurintervalle opgestel en die resultate is gebruik om elke spesie in rangorde te plaas op grond van sy assosiasie met lae tot hoë klimatologiese temperature
The genus Gyraulus has a worldwide distribution and is represented by two species, G. connollyi and G. costulatus in South Africa. While the latter species occurs elsewhere in Africa, G. connollyi is unique to South Africa
Summary
Inligting met betrekking tot die habitats en geografiese verspreiding van G. connollyi wat vanaf 1953 tot die hede dateer, is uit die databasis van die NV onttrek. Alhoewel die meerderheid monsters (64.9%) in habitats wat as standhoudend beskryf is, versamel is (tabel 2), het dit nie betekenisvol van die getal monsters wat uit seisoenale habitats afkomstig was, verskil nie. Alhoewel verreweg die grootste getal monsters (777) van G. connollyi in die temperatuurinterval wat vanaf 16 – 20 OC strek, geval het, verteenwoordig die 185 monsters wat in die temperatuurinterval wat vanaf 10 – 15 OC strek, 4.2% al die Mollusca-spesies in die databasis wat in hierdie interval versamel is (tabel 4). Die voorkomsfrekwensie in habitats wat in die vyf geselekteerde temperatuurintervalle geval het en die temperatuurindekse wat uit hierdie data bereken is, asook die plasing van die spesies in ’n rangorde op grond van hulle assosiasie met lae na hoë temperature, is in tabel 5 saamgevat. Tabel 3 Substratumtipes in die habitats van Gyraulus connollyi soos beskryf tydens versamelings
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