Miscellanea Zoologica Hungarica 11. 1997 (Budapest, 1997)

Nesemann, H.; Forster, R.: First record of Limnatis nilotica from Oman (Hirudinea: Hirudinidae)

Family Hirudinidae Limnatis nilotica (Savigny, 1822) Material: Wadi in Nizwa, 3 spec, 19. march 1996; Wadi near Sumail, 2 spec, 19. march 1996, leg. R. Forster, det. H. Nesemann. The size of the leeches is presented in Table 1. Table 1. Sizes of the collected individuals no. of specimen locality body lenght (mm) body width (mm) diameter of the caudal sucker (mm) 1 Nizwa 32 7,0 5,5 2 Nizwa 33 4.5 5,0 3 Nizwa 32 5,0 5,5 4 Sumail 34 4,0 5,5 5 Sumail 9,5 1,5 2,0 Notes: The living adults are unicoloured dark greyish-brown with one pair of broad marginal orange stripes. There are neither regularly arranged black spots nor lines on the dorsal surface of the body. In contrast to the adults the juvenile specimen from Sumail bears dorsally six longitudinal black lines, as in many mediterranean populations of this species (Figs. 1-2). The genital pores of all investigated specimens are separated by five annuli (Fig. 6). A closely related species Limnatis pallida (Tennent, 1859) known from Sri Lanka and Pakistan (Harding & Moore 1927, Sawyer 1986), was listed from several localities for the fauna of Saudi Arabia (Kinzelbach & Riickert 1984). Its systematic position is insufficiently investigated, because L. paluda should differ from L. nilotica only by some uncertain characters. Nevertheless our material from Oman clearly belongs to L. nilotica because of the presence of metameric colour markings and prominent marginal stripes. Habitat: The water bodies inhabited by L. nilotica are characterized by Witenberg & Izak (1967) as rainpools along wadis. Bromley (1994) summarized the habitats as springs, wells, water-troughs, small streams, ponds, ditches and reservoirs, where mammals come to drink, and/or where amphibians can be found. Al-Safadi & El-Shimy (1993) have mentioned L. nilotica as widespread species in most perennial waterbodies of Yemen. The investigated wadis in Oman are permanent water-bodies with extended lentic regions and a depth of 2 - 10 cm on average, and in some parts up to 30 cm. They are strongly sunlit, the water-temperature is about 25 - 30 °C. The substratum consists of rocks, stones, pebbles and sand without any muddy zones covered by numerous green algae. The wadi near Nizwa was remarkably polluted by blood of slaughtered animals. The benthic fauna of the wadi near Sumail comprises numerous individuals of the freshwater-snail Melanoides tuberculatus (O. F. Müller, 1774) and the triclad Dugesia sp. In the wadi near Nizwa two gastropods M. tuberculatus, Radix natalensis (Krauss, 1848) and several unidentified Heteroptera could be found frequently.