Long forgotten record of a freshwater leech on Madagascar indicates a host-associated dispersal event from continental Africa

Abstract

Madagascar houses a peculiar and largely endemic biota, having ancient Gondwanan affinities. However, the faunal composite of many invertebrate groups on the island is poorly known. For a long time, it was believed that the freshwater leech fauna of Madagascar contains a salifid species (Salifidae) only. Here, we report on a historical record of Placobdelloides multistriatus (Johansson, 1909) (Glossiphoniidae), a widespread African species, from Andrahomana, Southern Madagascar. Franz Sikora (1863-1902), an Austrian traveler and collector, who visited Andrahomana in 1899 to excavate fossils from a cave, collected the leech sample. The two specimens were obtained from an unspecified turtle species. We assume that P. multistriatus may have arrived to Madagascar relatively recently (i.e., in the Late Pleistocene or Holocene) via a long-distance dispersal event from continental Africa with its reptilian hosts such as the Nile crocodile and marsh terrapin. Based on a review of the body of available literature, two more freshwater leech species are known to occur on Madagascar: Linta be Westergren & Siddall, 2004 (Salifidae) and Alboglossiphonia sp. (Glossiphoniidae). Our findings indicate that Madagascar houses at least three freshwater leech species and that some additional taxa may have been overlooked there due to the scarcity of sampling efforts in the island’s freshwater bodies.