Atractides

Martin, Peter, 2016, Larval morphology of benthic and interstitial water mites (Acari: Hydrachnidia) from a Luxembourgian stream, Zootaxa 4139 (4), pp. 451-480 : 463-464

Atractides (s.str.) pumilus (Szalay, 1946)

Material examined. larvae attached to chironomid hosts of emergence traps of the Lurenzgriecht, measurements refer to 5 larvae.

Description. Habitus of the idiosoma distinctively elongated ( Fig. 6 A), larva only a little more narrowed anteriorly than posteriorly. L idiosoma 282–303 (292), W 192–207 (202). Dorsal idiosoma ( Fig. 6 A): Dp long, relatively small and alveolar, L Dp 276–300 (284), W 171–198 (182), Mp2-Amdp 40–46 (43), Mp1-Mp1 62–68 (65), Mp2-Mp2 49–59 (54), Lp1-Lp1 46–49 (48), Lp2-Lp2 74–79 (76), Mp1-Lp 1 12–14 (13), Mp2-Lp 2 17–22 (19), Mp1-Mp 2 25–29 (27), Lp1-Lp 2 24–28 (26), Mp 1 14–18 (17), Mp 2 8–14 (13), Lp1 58–66 (62), Lp2 115–130 (122), Hu 85–107 (97), Mh1 94–112 (102), Mh2 82–103 (88), Mh3 67–77 (73), Mh4 60–71 (65), Lh1 82–89 (85), Lh2 59–65 (62), Lh3 46–55 (51). Ventral idiosoma ( Fig. 6 B): Expp posteriorly rounded; E1 and E2 short and pinlike. Common median L of both CXI-III 177–186 (181), half W CXI-III 9 6–108 (100), C1-C2 36–43 (40), C1- Mmcp 24–29 (26), C4-Pmcp 113–121 (116), C1-C4 54–61 (58), C1 32–38 (34), C 2 29–43 (36), C3 64–82 (73), C4 64–82 (73); L Expp 43–47 (45), W 107–115 (111), E1- E 1 10 –14 (12), E2- E 2 24 –31 (28), E1 1 –2 (2), E2 1 –2 (2), setae V1 often approaching the anterior margin of Expp, V1 34 –38 (36), V2 situated far distally on Expp and near the anteriorlateral angle of Expp, V2 34 –44 (38), V3 44 –52 (48), V4 (without projecting base) 129–195 (164), L of projecting base of V 4 21–27 (24), anterior margin of Expp-Exp 23–24 (24). Gnathosoma: lateral length of base 108–112 (109), ventral width 49–58 (53), chelicera 89–94 (90), chela 18–20 (19), L PII 34–40 (37), W 26–31 (29), L PIII 16–19 (18), W 23–28 (25), long seta PIII L 1 01–107 (104), claw 14–18 (17).

Legs ( Fig. 7 A–E): Integument of all leg segments smooth, L L1 to L3 increasing, lateral leg claws provided with two subapical additional teeth, medial claw without additional teeth ( Fig. 7 E). Leg I ( Fig. 7 A): total L 232– 252 (243), L IL-1 (1se) 29–35 (32), IL-2 (7se) 43–46 (44), IL-3 (4se, 1so, 1eu) 44–49 (47), IL-4 (9se, 2so, 1eu) 54– 56 (55), IL-5 (12se, 1so, 2eu) 61–66 (65), H IL- 1 20–22 (21), IL- 2 19–20 (20), IL- 3 19–20 (19), IL- 4 19–22 (20), IL- 5 18–20 (19). Leg II ( Fig. 7 B, C): total L 253–276 (263), L IIL-1 (1se) 34–38 (36), IIL-2 (7se) 41–44 (42), IIL- 3 (4se, 1so, 1eu) 44–48 (46), IIL-4 (9se, 2so, 1eu) 60–67 (63), IIL-5 (12se, 1so, 2eu) 74–78 (77), H IIL- 1 20–22 (21), IIL- 2 19–20 (20), IIL- 3 19–20 (19), IIL- 4 19–20 (20), IIL- 5 20–22 (21). Leg III ( Fig. 7 D, E): total L 296–313 (302), L IIIL-1 (1se) 46–48 (47), IIIL-2 (6se) 44–48 (46), IIIL-3 (4se, 1so) 52–54 (52), IIIL-4 (9se, 1so) 71–73 (72), IIIL-5 (10se, 1eu) 84–90 (86), H IIIL- 1 19–20 (20), IIIL- 2 19–19 (19), IIIL- 3 19–20 (20), IIIL-4 1 9–20 (20), IIIL- 5 16–17 (16).

Remarks. The larva of the hyporheobiont Atractides pumilus was unknown before ( Gerecke 2003), the small size of the adults is clearly reflected by the larvae in that species. This may be the case for most of the hyporheobiontic species which breed larvae. The species-rich Atractides subgenus Atractides sensu strictu is a good example for our poor knowledge of the larval morphology. Larval descriptions are available for about only 10% of the known species in the Western Palaearctic.

Figures

FIGURE 6. Atractides pumilus, larva. A. dorsal idiosoma, B. ventral idiosoma. Scale bar 100 µm.

FIGURE 7. Atractides pumilus, larva. Setation of L- 5 only visible in IL and detail figures. A. IL, B. IIL, C. IIL- 5, D. IIIL, E. IIIL- 5. Scale bars: B, D 100 µm, A, C, E 50 µm.