Litarachna cawthorni, Wiles & Chatterjee & Troch, 2002

Wiles, P. R., Chatterjee, Tapas & Troch, Marleen De, 2002, Two new and one known marine water mite (Acari: Hydrachnidia: Pontarachnidae) from South-East Africa, Journal of Natural History 36 (16), pp. 1987-1994 : 1989-1991

Litarachna cawthorni new species

(gure 2)

Male. Idiosoma 324 long, 316 broad; glandularia free in integument; eye pigment well developed. Venter with epimera I–IV fused and EpI–EpI separate medially; suture EpI/EpII complete, EpII/EpIII and EpIII/EpIV incomplete; posterior margin of EpIV strongly concave with two pairs of apodemes not extending beyond the gonopore. E2 absent, large V3 gland without seta located behind the posterior margin of EpIV anterior to L2. Gonopore surrounded by sclerotized ring 24 long, 22 broad; four pairs of small genital setae on sclerotized ring and many (27–32 pairs) of perigenital setae free in integument around the gonopore. Anus located at posterior margin of body, posterior to V1 and V2. L3 fused with seta of V3 on same platelet (5possible acetabular plate of Cook, 1986: gure 284) anterior to two pairs of wheel-like structures behind posterior epimera. Pedipalp PII with large ventral projection, PIV with strongly developed ventral tubercules; length PI–PV, 10, 47, 14, 47, 16. Chelicera with claw-like chela. Legs with two long distal (swimming?) setae on IV-Leg-5; length I-Leg-3–6, 18, 19, 29, 35; II-Leg-3 –6, 19, 20, 32, 38; III-Leg-3 –6, 19, 22, 35, 41; IV-Leg-3–6, 23, 36, 45, 45.

Female. Similar to male but larger, body 359 long, 302 broad and with a diVerent genital eld. Gonopore oval, sclerotized anteriorly and posteriorly, 60 long, 32 broad and lacking setae; three pairs of wheel-like structures present behind posterior epimera. Length I-Leg-3–6, 20, 21, 30, 38; II-Leg-3–6, 20, 23, 34, 39; III-Leg-4–6, 20, 25, 47; IV-Leg-3–6, 26, 43, 49, 51.

Nymph. Similar to adult but lacking gonopore, with smaller posterior EpIV apodemes, a reduced ventral projection to PII and the gland V3, complete with seta, fused to L3 located on a platelet well posterior to EpIV. Two pairs of wheel-like structures present behind posterior epimera. Length PI–PV, 4, 15, 10, 19, 6. Legs with two long distal setae (swimming setae?) on IV-Leg-5; length I-Leg-3–6, 12, 12, 16, 20; II-Leg-3–6, 10, 12, 17, 20; III-Leg-3 –6, 12, 7, 21, 26; IV-Leg-3–6, 15, 22, 27, 29.

Material examined. HOLOTYPE S366, Kenya, Gazi Bay (4ss22¾S, 39ss30¾E), 16–19 July 1996, paratype 1 S340, paratypes 2 and 3 S368NN, paratype 4 S 369N.

Etymology. This species was named after Professor Mike Cawthorn, University of Buckingham, Clore Laboratory, Buckingham MK18 1PQ, UK, for his help in water mite research.

Remarks. A male, one female and three nymphs were in the collection examined. The nymphs are ascribed to the new species based on the pedipalp having a small, but clearly developed, PII ventral projection. The positions of ventral glands, however, diVer to those adults where seta V3 is fused to L3 and the separate V3 gland lies anterior to E4 behind EpIV. In nymphs the V3 gland and seta are fused with L3 and located well posterior of E4. A similar chaetotaxy is apparent in adults of Litarachna demhami . These observations are not consistent with Cook’s (1986) genital platelet hypothesis (see Discussion below). L. cawthorni most closely resembles L. sabangensis Viets, 1984 ( Viets, 1984) from the Philippines and L. kamui Uchida, 1935 from Japan ( Uchida, 1935), both of which have a ventral projection to PII. The greatly indented posterior margin of EpIV of L. cawthorni clearly diVers from the straight posterior margin of EpIV in L. sabangensis and the large PII ventral projection contrasts to the small projection of L. kaumi .