Gyratrix hermaphroditus Ehrenberg, 1831

Artois, Tom J. & Tessens, Bart S., 2008, Polycystididae (Rhabditophora: Rhabdocoela: Kalyptorhynchia) from the Indian Ocean, with the description of twelve new species, Zootaxa 1849, pp. 1-27 : 7-9

Gyratrix hermaphroditus Ehrenberg, 1831 species complex

Known distribution. Cosmopolitan and euryhaline, found from pure marine to pure limnic habitats.

New localities in the Indian Ocean. Zanzibar Island ( Tanzania): beach between the Institute of Marine Sciences and the Floating Restaurant, Ulva -like algae with sand, from rocks beside a stair from the beach to the dike, lower eulittoral at low tide (03/08/1995); off Maruhubi Palace ruins, sand flat, coarse sand with some detritus, relatively dry with many crab holes (05/08/1995); same locality, open beach with relatively fine sand (05/08/1995). Seychelles: Mahé, Grande Anse (Beolière), mangrove area, fine sediment from the upper eulittoral (19/12/1992); same locality, between two mangrove areas, relatively fine sand (15/12/1992), coarse sand (Amphioxus sand) from 19 m deep from an unknown locality in the Seychelles; Mahé, Baie Beau Vallon, little pool between granite rocks, fine sand (27/12/1992). McKenzie Point, Mombasa ( Kenya): fine, clear sand near to a mangrove area; very fine sand from a rock pool (12/10/1992); between rocks near the Four Seasons restaurant, dry coarse sand from the upper eulittoral (19/10/1992), same locality, fine sand with shell gravel, upper eulittoral (19/10/1992). Kanamai ( Kenya): tide pool, coarse shell gravel with very fine sand, mid-eulittoral (20/10/1992). La Réunion: Cap la Houssay, surf zone, coarse sand with pieces of coral (30/10/1992); Sabine les Bains, very coarse sand from a tide pool (02/11/1992). South-west Sulawesi ( Indonesia): Samolana, Kudingareng Keke, Galesong, Kajangan, all in coral sand from the eulittoral up to 20 deep, all between 30/09/1984 and 22/10/1984.

Material. Four whole mounts from Zanzibar, four whole mounts from the Seychelles, six whole mounts from Kenya, four whole mounts from La Réunion and four whole mounts from Indonesia.

Remarks. The pioneering researches of Reuter (1961), Heitkamp (1978), L’Hardy (1986) and especially Curini-Galletti & Puccinelli (1989,1990, 1994, 1998), Puccinelli & Curini-Galletti (1987), Puccinelli et al. (1990) and, more recently, Timoshkin et al. (2004) have shown that this “species” is actually a large complex of cryptic species. These species differ from each other in karyotype and detailed construction and dimensions of the hard parts in the male system. The organisation of the female system can also differ, some of the species are eyeless and their colour can vary (see Graff 1905, 1911; Artois & Schockaert 2001). The morphological and karyological diversity is not yet fully understood on a worldwide base, and the complex has not formally been split up. It could well be that the species complex is not monophyletic, and that some of the species are more closely related to Gyratrix proavus Meixner, 1929 or Gyratrix proaviformis Karling & Schockaert, 1977 .

The measurements of the stylet, sheath and stalk of the new material are given in Table 3 . They all fall within the range known from the rest of the world. These measurements once again illustrate the huge variation occurring within this species complex. No clear delimitation of cryptic species can be made, probably because of the confounding effect of the existence of multiple sympatric cryptic species, which is known to occur in a very high degree in the species complex (Curini-Galletti & Pucinelli 1990).