Torrenticola elliptica Maglio, 1909

Martin, Peter, 2016, Larval morphology of benthic and interstitial water mites (Acari: Hydrachnidia) from a Luxembourgian stream, Zootaxa 4139 (4), pp. 451-480 : 457-460

Torrenticola elliptica Maglio, 1909

Material examined. Larvae reared from females from the Lurenzgriecht and larvae from emergence collections from the Lurenzgriecht in 2002; if not otherwise indicated, measurements refer to 5 larvae.

Description. Character as stated in generic diagnosis. Coxal plates III without posterior projections.

Habitus of the idiosoma rounded ( Fig. 2 A), only slightly more narrowed anteriorly than posteriorly, in unengorged individuals posterior idiosoma slightly intended. L idiosoma 220–233 (226), W 188–193 (189). Dorsal idiosoma ( Fig. 2 A): Dp relatively large and alveolar, shape anteriorly slightly tapered, posteriorly rounded, L Dp 185–198 (190), W 148–155 (150), L of eye capsule 148–155 (150), Mp2-Amdp 37–41 (39), Mp1-Mp 1 28–32 (30), Mp2-Mp2 48–52 (50), Lp1-Lp 1 14–17 (16), Lp2-Lp2 68–73 (70), Mp1-Lp1 7–9 (8), Mp2-Lp 2 14–17 (16), Mp1- Mp2 32–36 (34), Lp1-Lp2 34–37 (36), Mp 1 10–13 (12), Mp 2 12–18 (14), Lp1 35–39 (37), Lp2 86–94 (89), Hu 47–51 (48), Mh1 78–83 (80), Mh2 65–72 (68), Mh3 55–65 (61), Mh4 42–45 (44), Lh1 51–55 (53), Lh2 55–59 (56), Lh3 38–42 (40). Ventral idiosoma ( Fig. 2 B): almost completely covered by coxal plates, setae V1 and V2 dislocated on the CXII+III, V3 and V4 dislocated from ventral to the dorsal idiosoma. Both CXI separated from each other and from CXII+III, common median L of both CXI 73–78 (75), max. L CXI 118–130 (124), max. W CXI 43–45 (44), common median L of both CXII-III 100–113 (105), max. W CXII-III 93–100 (96), C1-C2 43–50 (46), C1-Mmcp 25–28 (27), C4-Pmcp 85–98 (94), C1-C4 68–75 (71), C 1 9–15 (11), C 2 22–30 (25), C 3 25–28 (26), C 4 12–14 (13); Expp strip-like, bearing two pairs of setae E1 and E2 ( Fig. 2 E), Exp located slightly posteriorly, Expp L 8–9 (8), W 24–28 (26), E1-E 1 8–12 (11), E2-E 2 18–23 (21), E1 4–7 (6), E 2 7–10 (8), V 1 15– 19 (17), V 2 15–18 (16), V 3 23–28 (25), V4 98 –120 (108). Gnathosoma (n=4): lateral L of base 57–59 (58), chelicera ( Fig. 2 D) L 53–56 (55), W 15–17 (16), chela L 13–14 (14), ppalpus ( Fig. 2 C) L PII 23–23 (23), W 24–24 (24), L PIII 17–19 (18), W 19–20 (20), claw L 8–10 (9).

Legs (n=5): Leg I ( Fig. 3 A, B): total L 230–244 (236), L IL-1 (1se) 29–32 (31), IL-2 (6se) 37–39 (38), IL-3 (4se, 1so) 49–52 (50), IL-4 (8se, 2so) 58–61 (59), IL-5 (12se, 1so, 1eu) 57–60 (58), H IL- 1 21–23 (22), IL- 2 20–21 (20), IL- 3 19–20 (20), IL- 4 18–23 (19), IL- 5 15–16 (16). Leg II ( Fig. 3 C, D): total L 245–253 (249), L IIL-1 (1se) 32–34 (33), IIL-2 (7se) 36–38 (37), IIL-3 (4se, 1so) 47–49 (48), IIL-4 (8se, 2so) 66–67 (66), IIL-5 (12se, 1so, 1eu) 64–65 (65), H IIL- 1 21–22 (22), IIL- 2 20–21 (21), IIL- 3 17–19 (18), IIL- 4 18–18 (18), IIL- 5 16–16 (16). Leg III ( Fig. 3 E, F): total L 321–332 (327), L IIIL-1 (1se) 6 8–71 (70), IIIL-2 (6se) 55–57 (56), IIIL-3 (4se) 57–58 (57), IIIL-4 (8se, 1so) 76–78 (77), IIIL-5 (12se) 65–68 (66), H IIIL- 1 19–20 (20), IIIL- 2 18–20 (19), IIIL- 3 16–17 (17), IIIL- 4 17–18 (18), IIIL- 5 15–16 (15). Leg claw consisting of one short empodium and two longer ambulacra ( Fig. 3 G), the latter with one large median tooth and two small lateral teeth.

Remarks. There are some descriptions of Torrenticola species, mainly from North America (e.g. Prasad & Cook 1972; Smith 1982). From European species only larvae of T. anomala (Koch, 1837) and T. amplexa (Koenike, 1908) are hitherto described ( Wainstein 1980; Tuzovskij 1982; Müller 2015), another illustration of Torrenticola sp. larvae derives from Müller & Meidl (2013). Thus, the description of larval T. elliptica is only the third European species of that genus which is known out of about 70 species (de Jong 2013). Therefore, the diagnosis for that genus has to remain preliminary.

One interesting general finding that results from the description of the larva of T. elliptica is that in Torrenticola also CXI may be separated from CXII+III. In all other known larval Torrenticola descriptions CXI (except of the Torrenticola sp. larvae in Müller & Meidl 2013) is completely fused with the other coxal plates. The widely fused coxal plates, the extent of the ventral sclerotization, the characteristic Expp and the rounded Dp makes it easy to distinguish between the Torrenticola and the other larvae treated here.

Figures

FIGURE 2. Torrenticola elliptica, larva. A. dorsal idiosoma, B. ventral idiosoma, C. palpus, D. chelicera, E. excretory pore plate. Scale bars: A, B 100 µm, C, D, E 50 µm.

FIGURE 3. Torrenticola elliptica, larva. Setation of L 5 only visible in detail figures. A. IL, B. IL- 5, C. IIL, D. IIL- 5, E. IIIL, F. IIIL- 5, G. claws of IIIL- 5. Scale bars: A, C, E 100 µm, B, D, F, G 50 µm.