Water mites from Pacific Islands (Acari: Hydrachnidia) Author Smit, Harry text Zootaxa 2004 588 1 20 journal article 10.5281/zenodo.157984 60404471-0240-4f7a-8003-84f1fdf3af34 1175­5326 157984 837CA240-5C28-4A26-B68F-3AD322FE62B9 Unionicola pacifica n. sp. ( Figs. 18 –24) Material examined Holotype male: rock pools along Vaiola Road, Savaii, Western Samoa , 13º 38.357 S , 172º 15.352 W , 18 October 2003 . Paratypes : 2 females , same data as holotype . Other material: 1 male , 3 females (all lacking legs and/or palp), same data as holotype . Diagnosis PIV with three well developed tubercles; seta of seta­bearing tubercle much shorter that tubercle; lateral tubercles of PIV as long as seta­bearing tubercle, medial tubercle of PIV longer than other two tubercles; genital field with two pairs of five acetabula. Description Male: body 445 long and 391 wide. Body soft. Posterior apodemes of anterior coxal plates extending halfway third coxal plates ( Fig. 18 ). Posterior margin of fourth coxal plates with short projections at posterior margin. A pair of glandularia lying in the secondary sclerotisation medial of these projections, with very long associated setae. Genital field terminal, with five pairs of acetabula, the anterior pair lying next to each other, the posterior three pairs lying behind each other. Lengths of PI­PV: 20, 100, 40, 84, 68. PIV with a relatively stout seta­bearing tubercle, seta much shorter than tubercle; lateral tubercles of PIV as long as seta­bearing tubercle, medial tubercle of PIV longer than other two tubercles ( Fig. 19 ). Lengths of I­leg­4­6: 243, 180, 160; I­leg­6 slightly bowed ( Fig. 20 ). First and second legs with long "rillborsten". Lengths of IV­leg­4­6: 203, 292, 251. Third and fourth legs with stiff swimming setae. IV­leg­5 with three and IV­leg­4 with two swimming setae. Swimming setae of third leg hardly distinguishable from the long normal setae of this leg. Female: body 502 (607) long and 389 (462) wide. Body soft. Posterior apodemes of anterior coxal plates extending halfway third coxal plates ( Fig. 21 ). Posterior margin of fourth coxal plates with short projections at posterior margin. Coxal plates with reticulation. A pair of glandularia lying in the secondary sclerotisation medial of these projections, with very long associated setae (but lost in one of the illustrated females). A pair of glandularia tubercles at posterolateral corners of body. Genital field terminal, with five pairs of acetabula, the anterior pair lying next to each other, the posterior three pairs lying behind each other ( Fig. 22 ). Anterior platelet of genital field with two medial setae, posterior platelet with one medial seta. Lengths of PI­PV: 24, 136, 64, 114, 85; palp (Figs. 23–24) as in male. Length of I­leg­4­6: 292, 215, 192. Lengths of IV­leg­4­6: 251, 340, 300; legs as in male. Etymology Named after its occurrence in the Pacific. Remarks The new species is close to a number of species occurring in New Caledonia , New Zealand and/or Australia with a PIV with three well­developed tubercles, i.e. U. longiseta Walter , U. pseudoannulata Cook , U. neoaffinis Cook and U. billieaehonore Crowell. In U. neoaffinis the seta on the tubercle of PIV is almost as long as the tubercle, in all other species the tubercle is much longer than the seta. However, in U. billieaehonore this character has not been described, but this species has much slender tubercles on PIV compared to the new species. Leg segments are much shorter in the new species compared to the remaining two species. IV­leg­6 of the male of the new species is 300 long, in U. longiseta and U. pseudoannulata this segment measures 523–570 and 502–531 respectively. Moreover, also the palp segments of the new species are shorter than in these two species. Finally, the tubercles of PIV are very slender in U. longiseta , while they are relatively stout in the new species. I have not assigned the new species to a subgenus. Probably it keys out in Mitchellatax Vidrine , given the bowed I­leg­6, but the first leg is not setose, as in U. pseudoannulata . FIGURES 18–20. Unionicola pacifica n. sp. , holotype male. 18 = ventral view; 19 = palp; 20 = Ileg­4­6. Scale lines: 50 µm. FIGURES 21–22. Unionicola pacifica n.sp. ; paratype females. 21 = ventral view; 22 = genital field. Scale lines = 50 µm. Unionicola pacifica n.sp. ; paratype female. 23 = palp; 24 = palp. Scale lines = 50 µm.