Atractides

Gerecke, Reinhard, 2003, Water mites of the genus Atractides Koch, 1837 (Acari: Parasitengona: Hygrobatidae) in the western Palaearctic region: a revision, Zoological Journal of the Linnean Society 138, pp. 141-378 : 165-167

SUBGENUS ATRACTIDES S.S.

Diagnosis: No pronounced sexual dimorphism in setation of I- and II-L; ventrodistal tip of I-L-5 not extending beyond dorsodistal margin of the segment (I-L-5 dL> vL) S-2 not extremely inflated, and I-L-6 not strongly shortened; P-1 subquadratic or only slightly elongated (L/H <1.5); chelicera robust (L/H <8.0).

Discussion: The subgenus is a typical paraphylum, a dumping ground used when species groups with welldefined common characters are separated. Within it, several groups of related species emerge and are discussed in the sections concerning the respective species. It is too early, and the geographical area considered is too restricted, for further taxonomic decision-making. Atractides is a highly diverse water mite subgenus and remains a complicated study subject with many characters appearing many times in numerous combinations within clearly distant species groups.

ATRACTIDES SPINIPES KOCH, 1837

( FIGS 11G AND 14A–I )

Type series: Missing. Locus typicus of the first description: southern Germany, Rheinland Pfalz , Schwarzbach near Zweibrücken. Neotype ♂, here designated: Germany, D453/4, Bad.-Württ. ( TÜ) Schönbuch , Goldersbach bei Teufelsbrücke, 390 m, 5.10.1995 –Steine–, dissected (gnathosoma separate, palps and both I-L lateral) mounted on slide in Hoyer’s fluid; Paraneotypes: 1/ 6/0, deposited at SMF. Further paraneotypes: 6/35/0, same collecting site, various collecting dates, in Gerecke collection, Tübingen.

Rejected species classifications. CSM: 6 slide-mounted females labelled as A. spinipes (nos. 316, 673, 676, 678, 680 from Black Forest , 672 unclear) . NHMB: ex Piersig collection, without locality specification, 2 ♂, 1 ♀ : Megapus spinipes Koch coll. Piersig; IX/40–41 [old nrs: 480/480a], ♂, two slides with idio- /gnathosoma, completely desiccated, various legs missing; IX/42–43 [old nrs: 481/481a], ♂, two slides with idio-/gnathosoma, idiosoma in good state, gnathosoma + r. I/II-L desiccated, but partly interpretable; IX/07–08, ♀, two slides with idio-/gnathosoma, idiosoma in good state, palps and I-L strongly crushed, gnathosoma and chelicerae desiccated; Megapus spinipes Koch ♀ Lüneburg. Heide coll. Koenike IX/05–06, two slides with idio-/gnathosoma, idiosoma damaged at both Cx-3, one I-L missing, gnathosoma and the other I-L desiccated but not crushed. NHUB: Lüneburger Heide, Böhme in der Böhme , H.Müller leg. VII, 1901: 1056, ♂ , with air bubbles, genital field inclined, Cx-1 + 2 damaged; 1059, ♂, in reality ♀, some leg segments missing, genital field strongly inclined; 1057 ♀, undissected, legs distorted; Bad Eilsen, in der Aue Koenike leg, 2.8.07: 1062? ♀ undissected. SMNH: 6274, Megapus ♂ ? spinipes (C.L.Koch) Jylland : Letbaek Mölle vid Nörholm, Sig.Tistrup. 14∞C Kl.2c.m. leg. J.K. Tindal 16.6.1918 dorsum and several legs absent, in reality ♀. MMB: (partly mounted together with specimens of other genera/species) 163, Velké Losiny potok 20.8.1957 ♀ ; 181, Pritok Moràvky n Mûsy 3.8.1950 ♀; 369, Potok Ratibor 4.7.1950 ♂, 3 ♀; 370, Oravice nad Tristenov 5.7.1950 ♀ 378, Potok pod Kubinskov Melov 6.7.1950 ♀; 395, Orava v Nizné 10.7.1950 3 ♀; 472, Potok jezerny n Vet. Kartovic Beskydy 23.8.1950 ♀; 598, Studen y ¢ p. v Podbietu 16.7.1951 ♀; 616, Váh n Kralovan, 19.7.1951 ♀; 812, Pramen y ¢ pot. pod Javornikem 17.8.1953 3 ♀.

Description: The preparations from the various collections provide some idea about the character combinations interpreted by early researchers as diagnostic for this species. An important common feature of most specimens listed is that they are juveniles: idiosomal sclerites are weakly sclerotized, the sclerite rings surrounding glandular openings and their accompanying seta are nearly invisible, and in many cases appendages are distorted. Some common morphological features (to the extent that they are visible) are: integument striated (7–10/10 Mm) glandularia diameter about 20 Mm, Vgl-1/2 unfused, excretory pore unsclerotized. In view of the problematic definition of A. spinipes , the individual preparations merit the following remarks.

CSM: All specimens juvenile, some damaged by crushing. Except for 676 ( A. pennatus ) they have characters typical for A. nodipalpis . In several cases deformations are due to juvenility and weak sclerotization. NHMB IX/42–43: Cx-4 asymmetric, insertion area of right IV-L deformed; genital plates fused anteriorly and posteriorly by weak bridges including the pre- and postgenital sclerites, regarding setation similar to females (no median setae on the level of Ac-1 and -2, a group of 5–6 setae anteriorly from Ac-1, gonopore rather large, not well confined).

NHMB IX/40–41: genital field similar, genital skeleton in situ. NHMB IX/ 05–06, NHMB IX/07–08: palps rather thick, probably a mounting artefact. NHUB 1056: Cx-4 with protruding posterior angles, genital field with weakly sclerotized anterior and posterior bridges between acetabular plates similar to NHMB IX/42–43, but with male-typical setae medially from Ac-1 and Ac- 3, and normally shaped gonopore. I-L-5 longer and with higher HB than in NHMB IX/42–43, I-L-6 strongly tied up centrally; P-2 without ventral protrusion, but P-4 male-typical, strongly thickened at the level of insertion of the proximoventral seta, ventral setae placed close together (3: 2: 3) sword seta strong, on the level of the proximoventral seta, dorsal hairs densely arranged.

NHUB 1057, 1059: juvenile ♀, dorsal L P-3/4 130/135 Mm; 1062?: dorsal L P-3/4 117/135 Mm. SMNH 6274: rather old specimen (integument leathery, extended postcoxal idiosoma) but with weak sclerotization and small glandularia (<20 Mm); genital field rather small, with female-typical genital plates bearing round, triangularly arranged Ac, genitalia small, gonopore short; P-2 ventrally without protrusion but with rugose surface and pointed ventrodistally, P-3 with hyaline ventrodistal area, P-4 with a large medial sword seta.

MMB: Only a few collecting sites provided on the slides have been published unequivocally (370, 395, 598: Láska, 1963). On the other hand, I was unable to examine preparations of the specimens published earlier ( Láska, 1955a, 1957, 1959) and am unable to understand Láska’s morphological concept of A. spinipes . From his only comment on morphology ( Láska, 1966: 98) one can deduce that he followed the key of K. Viets (1936): equal dorsal length of P-3 and P-4, male genital field with anterior and posterior incisions, female acetabula not arranged in a triangle). The females he filed under this name are heterogeneous with regard to integument structure (mainly striated, but specimens with lineated integument on preps 369, 616, 812; in his 1966 paper he states that the integument should be papillate), position of the sword seta on P-4 (near the proximal or distal ventral hair) and shape of the genital plate (Ac in a more or less triangular arrangement). In most cases, the length ratio of P-3/4 does not fit the diagnosis provided by K. Viets (1936). The main part of the material falls within the range of variability found in A. nodipalpis ; some specimens are probably aberrant representatives of different species. The two males in Láska’s collection are obviously juveniles. One of them (369) is weakly sclerotized, with a genital field of female aspect and a strange sclerotized structure within the idiosoma that could be interpreted as an early stage of a developing Gsk, but also as an artefact due to folded integument. The other male (472) is most probably a hermaphrodite as described above ( Fig. 13E,F ), with genital plates nearly unfused medially, the Gsk present, but a female-type palp.

Neotype series

General features dorsal integument: striated (8–9/10); muscle attachments: unsclerotized coxal field: little protruding anterior edges of Cx-1–3

I-L: S-1 and -2 similar in dimensions and shape, narrow interspace, with bluntly rounded tips; I-L-6 stout and weakly curved excretory pore: smooth; Vgl-1: fused to Vgl-2

palp: weak sexual dimorphism

Males

Neotype, in parentheses 4 paraneotypes genital field: anterior margin convex, posterior margin weakly indented palp: P-2 ventral margin convex, ventrodistal edge right-angled, but not protruding; P-3 ventral margin slightly convex; P-4 ventral margin 1: 1: 1, sword seta halfway between ventral hairs idiosoma L/W 380 (360–405)/280 (260–290); glandularia 26

coxal field L 220 (210–230), Cx-3 W 252 (229–252), Cx-1 + 2 mL 90 (81–92), IL 162 (153–162), W 202 (184–202)

I-L-5 dL 114 (109–116), vL 83 (81–87), dL/vL 1.37 (1.32–1.37), HA-HC 28 (26– 32), 35 (33–35), 41 (19–41), dL/HB 3.26 (3.11–3.52)

S-1 L 60 (54–60), L/ W 10.0 (8.6–10.0), S-2 L 55 (52–55), L/ W 7.9 (6.8–7.9), interspace 8 (8–10), L S-1/2 1.09 (1.04–1.11)

I-L-6 L 87 (85–91), HA-HC 22 (21–22), 19 (17–20), 18 (17–18), dL/HB 4.58 (4.40–5.35); L I-L-5/6 1.31 (1.27–1.31)

genital field L/W 72 (65–78)/72 (67–74), Ac-1–3 L 24, 19, 24

gnathosoma vL 83 (76–90), chelicera L 143 (138–143), L/H 5.30 (5.30–5.52), bS/claw 2.33 (2.21–2.33)

Figures

Figure 11. Morphology of Atractides. Malformations. A, A. octoporus ♀ (Goldersbach), genital field with reduced number of left Ac; B, A. nodipalpis ♂ (Brigach, S Germany), genital field with reduced Ac-1/2; C, D, A. nodipalpis (Brigach) C, genital field with reduced left Ac-1 and right Ac-2; D, palp, medial view; E; F, A. nodipalpis intersex (Goldersbach) E, genital field with genital skeleton in situ; F, palp, medial view. G, A A. spinipes ♀ (Goldersbach) with ventral seta on I-L-5 similar in shape to blade setae S-1 and -2; H, A. nodipalpis ♂ (Goldersbach) with doubled I-L-6, quadrupled S-1 and -2, and doubled claws on left I-L-6. Scale bars = 100 µm.

Figure 13. Comparison of palps and I-L of both the largest and smallest specimens in a population of A. nodipalpis in Goldersbach. A–D, males, E–H females. A, B, G, H, I-L-5 and -6; C–F palps. Scale bar = 100 µm.

Figure 14. Atractides spinipes, neotype series. A–E, neotype ♂, F–I paraneotype ♀. A, ♂ idiosoma, ventral view; B, ♂, I-L-5 and -6; C, ♂ palp, medial view; D, ♂ palp, lateral view; E, ♂ gnathosoma and chelicera, lateral view; F, ♀, genital field; G, ♀, I-L-5 and -6; H, ♀ palp, medial view I ♀ palp, lateral view. Scale bars = 100 µm.