Nilotonia (Cookonia), 2008

Goldschmidt, Tom, 2008, Taxonomical, ecological and zoogeographical studies on anisitsiellid water mites (Acari: Hydrachnidia: Anisitsiellidae Koenike, 1910) from Madagascar, Zootaxa 1954 (1), pp. 1-120 : 48-50

Nilotonia (Cookonia) subgen. nov.

Typus subgeneris: Nilotonia (Cookonia) anjozorobe sp. nov.

Derivatio nominis: Cookonia — the subgenus is named after Dr. Dave Cook (Paradise Valley, USA), who made the present study possible, to honour his life-long work on water mites.

Diagnosis: Large dorsal plate covering most of dorsum, including Dgl-3 to -5 (mostly also Dgl-6 and Lgl- 4, see below), dorsal plate without ridges or traces of fusion of smaller platelets; capitular bay relatively wide, shallow; coxae closely approached or fused; medial margin of Cx-III short, rounded Cxgl-2 lying between Cx-II and Cx-III, Cxgl-4 at anterior margin of Cx-III; suture between Cx-III and Cx-IV reaching far medial, but incomplete; coxal field caudally and laterally extended by secondary sclerotization (forming unified — or nearly unified — ventral plate, not including Vgl-2 and -4); Cx-III/IV form narrow genital bay, medial margin of Cx-IV caudally diverging, caudal corner rounded-rectangular; legs without swimming hairs, bearing strong setae; leg-I to -III bear claws with one dorsal and one ventral clawlet, leg-IV-6 with two small, peg-like terminal setae and one mid-sized sub-terminal seta; capitulum of characteristic shape, short and high (nearly rectangular); P2 with ventral seta far laterally, P5 bearing long claws; cheliceral claw large with very broad blade.

Remarks: The character state of Nilotonia (Cookonia) subgen. nov. could be interpreted as a transition from the stronger sclerotized subgenera of Nilotonia Thor, 1905 — like Mamersonia (K. Viets, 1954) and Telotaolana subgen. nov. — towards Mamersella K. Viets, 1929 . In Nilotonia (Mamersonia) testudinata Cook, 1966 from Liberia as well as in N. (Mamersonia) monoscutata ( Bader, 1995) and N. (Mamersonia) similis ( Bader, 1995) from Trinidad, their extended dorsal sclerotization is comparable to Cookonia . Also in the strongly sclerotized venter, the shape of the coxal field and the legs Cookonia corresponds with the diagnosis of Mamersonia given by Goldschmidt (2004b). However, beside the different structure of the dorsal plate (in Mamersonia, the development of the dorsal shield by fusion of several smaller dorsal plates is still visible), Cookonia is mainly differentiated from N. (Mamersonia) by the shape of the gnathosoma: The capitulum is characteristic due to its short, compact — nearly rectangular — shape; P4 is curved in the dorso-distal part (in one species nearly club-shaped) and medio-distally rounded, P5 bears very long and slender terminal claws; and the cheliceral claws are large with a very broad blade. Cookonia also shows general similarities with Mamersella (Neomamersella) tototaensis Cook, 1966 from Liberia (West Africa), mainly in the dorsal plate, legs and gnathosoma — especially the long and slender terminal claws of P5 ( Cook 1966; see also Figs 121, 122 ). However, in many details the differences are too strong to propose closer relationships: In M. tototaensis Dgl-2 to -5 are fused with dorsal shield (in Cookonia Dgl-3 to -5 (mostly also Dgl-6 and Lgl-4)); Cxgl- 4 are missing (in Cookonia present at anterior margin of Cx-III); Vgl-3 are far caudal from Cx-IV (in Cookonia very close) and Vgl-2 are fused with the ventral shield (separate in Cookonia ). However, M. tototaensis and Cookonia seem to have intermediate character states of Mamersella and Nilotonia . For the discussion of the systematic position of Mamersella (Neomamersella) tototaensis see discussion in the chapter on Platymamersopsis .

Figures

FIGURES 121, 122. Mamersella (Neomamersella) tototaensis Cook, 1966, female holotype (FMC Lib 82): 121, leg-II; 122, leg-IV. Scale bar = 100 µm.