Parasitism Of Placobdelloides Siamensis (Oka,1917) (Glossiphoniidae: Hirudinea) In Snail-Eatingturtles, Malayemys Spp., And The Effects Of Hostand Aquatic Environmental Factors

Abstract

The Siam Shield Leech, Placobdelloides siamensis, is a common leech found onMalayemys turtles in Thailand. Sixty Snail-eating Turtles (29 Malayemys macrocephalaand 31 M. subtrijuga) were caught over twelve months (February 2017 – January 2018) todetermine host characteristics (body size, weight and sex), parasitism (prevalence,intensity and density) and seasonal aquatic environmental factors (conductivity, nitratenitrogen, dissolved oxygen, pH, salinity and total dissolved solids). There was nosignificant difference of infection rate between species and sex in both turtle species.Leech prevalence indicated that all turtle individuals were infected throughout year, whilethe infection rate was significantly higher in larger and heavier turtles mainly on thecarapace with an average number of leech approximately 474.80 ± 331.38 individuals forindividual host infection and 76.53 ± 20.27 individuals for infection per 100 g body weight.The high level of leech parasitism also caused a rot wound and shell hole which causedthe host to die. Aquatic environmental factors did not influence the infection of leeches inboth turtle species. Therefore, the factors that influenced the infection rate of P. siamensiswere based on only host body size and weight without effect from season. In addition, this study also showed two new hosts, including Cyclemys oldhamii and Heosemys grandis and the widespread distribution from northern, north-eastern, western, central and southern Thailand were reported