Ancyronyx minerva Freitag & Jaech , 2007

Freitag, Hendrik & Balke, Michael, 2011, Larvae and a new species of Ancyronyx Erichson, 1847 (Insecta, Coleoptera, Elmidae) from Palawan, Philippines, using DNA sequences for the assignment of the developmental stages, ZooKeys 136, pp. 47-82 : 52-57

Ancyronyx minerva Freitag & Jaech, 2007 Figs 311 A–L

Ancyronyx minerva Freitag & Jäch, 2007: 50-53 (adult description); Freitag and Pangantihon 2010: 133 (first record Mindoro).

Material examined.

2L (0.21, 0.24) (PCSD) "PHIL.: Palawan, P. Princesa Panaguman R., Marufinas 10°15'09"N, 118°58'03"E 15.6.2001, leg. Freitag (PR1)C-R".1♀ (CFP) "PHIL.: Palawan, P.Princesa; Concepcion, Tagpaya, Camp Aga, Taranaban R. trib.; mount.creek c.8km upstr. Highw., dist. prim. forest; riffle; rocks, boulders, roots; c.450m asl 10°05'N, 119°01'E, 26.4.1995 leg. Pangantihon (16f)M"; 2L (0.28, 0.29) (CFP) "PHIL.:Palawan, P.Princesa, Sta. Cruz, Calatobong Riv., Nat.Highw. km29; rocks CPOM, riffe & side pools; heavy metal soil,sec.veget.,25m asl, 9°56'41"N, 118°44'56"E 14.11.1995, leg.Freitag (124)"; 42 exs, 3L (0.27, 0.28, 0.30) (PCSD, NMW) "PHIL.: Palawan, P. Princesa, Iwahig, Balsahan Riv., upstr.dam; riffle, boulders, gravel, wood, moss; 9°46'36"N, 118°39'55"E 24.1.1995, leg. Freitag (20)M"; 2L (2 × 0.27) (CFP) "PHIL.: Palawan, P. Princesa, Irawan River, 6km NW of PPC, 2km upstream of water plant 9°49'N, 118°39'E 06.4.1994, leg. Freitag (60)M"; 1L (0.27) (ZSM [FR025]) "PHIL.: Palawan, P. Princesa, Iwahig, Salomon Riv.; rural near sec. forest, riffle, boulders, gravel, wood; 9 °46'59"N, 118°40'53"E 24.1.1994, leg. Freitag (159)M"; 2♂♂, 1♀, 4exs., 1 L (0.26) (CFP) "PHIL: Palawan, P.Princesa, Bgy. Montible, rd. km 29, Iwahig River, big mount. river, boulders, CPOM; 9°41'20"N, 118°37'29"E 24.11.2007, leg. Freitag (130)M"; 1♀, 4 exs., 1 L (0.24) (ZSM [FR001], ZMUC) "PHIL.: Palawan, Aborlan; Cabigaan, Talakaigan R.; mount.Riv. upst.dam, riffle, rocks, boulders, CPOM, forest, c.50m asl, 9°26'50"N, 118°26'49"E 25.2.1995, leg. Freitag (154)M"; 2♂♂, 1♀, 11 L (2 × 0.22, 2 × 0.25, 2 × 0.26, 3 × 0.27, 2 × 0.28) (SMTD) "PHIL.: Palawan, Narra, 7 km N town centre, downstr. Estrella Falls, mountain riv.; sec. forest; gravel, boulders, submerged wood, riffle; c. 50m asl., c. 9°20'N, 118°23'E 16.4.2010, leg. Freitag & Pangantihon (180a)"; 12 exs. (CFP) "PHIL.: Palawan, Narra, 5 km W town proper, Taritien River, riffle, boulders, leaf litter; c. 100m asl. 9°19'11"N, 118°22'35"E 17.4.2010, leg. Freitag et al. (182a)"; 1♂ (CFP) "PHIL.: Palawan, Rizal, Campung-ulay, Kalitawan Riv.; HW km 212.2, sec. veget/forest; slightly polluted, submerged wood in run, c. 30m asl. 9°19'11"N, 118°22'35"E 02.7.2010, leg. Freitag (186)"; 7 exs. (ZSM) "PHIL.: Palawan, Rizal, Ransang, Ransang Riv., E of HW km 223; sec. veget. Caingin; submerged wood, c. 50m asl. 9°19'11"N, 118°22'35"E 02.7.2010, leg. Freitag (184b)"; 1♀ (CFP) "PHIL.: Palawan, Rizal, Punta Baja, Malambunga Riv.; HW km 202.1, farmland; submerged wood in run, c. 10m asl. 9°19'11"N, 118°22'35"E 02.7.2010, leg. Freitag (187a)";

Larval description (based on 6th instar).

Colour as in Fig. 3, predominantly dark-brown; legs, antennae, posterior and lateral head portions yellowish. Most anterior portion of pronotum with yellowish band reaching up to the lateral margins, this pale band slightly extended posteriad along the midline. Meso- and metanotum and abdominal segments at medioposterior margin with broadly subtriangular yellow pattern. A light colour pattern might by present or lacking at the apex of abdominal segment IX, but never extends anteriad up to more than 0.2 posterior.

HW c. 0.27 mm; entire larva about 3.0 mm long. Body torpedo-like elongate, subsemicircular in cross section, dorsally vaulted, ventrally almost flat. Posterolateral margins of abdominal segments I–VIII moderately produced (Fig. 11A). These projections either not, or only slightly overreaching posterior segment margins. Posterolateral edge of these projections with long posteriad-directed trichoid tooth, overreaching middle of subsequent abdominal segment when that retracted (11B). Spiracles (Figs 11 A–C) present laterally on mesothorax and abdominal segments I–VIII, surrounded by glabrous areas. Dorsal side densely covered with setiferous tubercles (Fig. 11B). Ventral side smoother, with scattered setae (Fig. 11D). Retractable portions of body segments without setae and tubercles (Figs 11A, E).

Head (Figs 3; 11 F–I) exposed, distinctly prognathous, sides subparallel in posterior half, with lateral clumped, not exposed stemmata in a glabrous area, lined by a irregular row of six long acuminate setae on each side (Fig. 11F). Frontal suture U-shaped, rather inconspicuous; frontoclypeal suture arcuate (Fig. 11G). Clypeus distally glabrous, with subbasal fringe of fasciculate setae originated from tubercles (Fig. 11G). Ventral side (Fig. 11H) with almost glabrous median portion, lateroposteriorly with tubercles. Gula with concentrically arranged asperities. Antenna (Fig. 11I) three-segmented, c. 1/3 as long as head, basally connected to a segment-like membranous peduncle. Peduncle stout, bald, partly retracted into head capsule; scape slightly longer than peduncle about as long as broad, with dorsolateral fringe of branched trichoid setae; pedicel cylindrical, more than two times as long as scape and c. three times as long as broad, with few apical trichoid setae; flagellum and sensorium cylindrically elongate, subequal in length; apex of flagellum with cylindrically elongate sensillum. Labrum (Fig. 11G) subrectangular, c. 2.5 times as wide as long, with a subapical fringe of ramose setae and scattered trichoid and truncate (sensory) setae, proximal portion glabrous. Mandibles with distal portion subfalcate; apex tridentate; incisory margin densely setose; outer margin glabrous, with one elongate, ramose squamose seta (Fig. 11I). Maxilla (Figs 11H, I) moderately broad; cardo stout, divided, lateral portion with one median lanceolate seta; stipes subtrapezoidal, glabrous, with few lanceolate and one latero-subapical trichoid seta; maxillary palpus four-segmented, approx. as long as stipes broad, distal segment subglobular with several apical sensilla of various shape; predistal segment with lateroapical trichoid seta; galea and lacinia subequal in length and shape, shorter than palpus, apically with acuminate setae. Labium as in Figs 11H, I; mentum (postmentum) broad (about 1.5 times of stipes), with median groove most depressed posteriorly, with one pair of moderately long trichoid setae sublaterally at anterior 0.25, one pair of subbasal spinose setae and one pair of short subapical lateral spines; submentum (prementum) short, subrectangular, with one laterobasal pair of setae; ligula inconspicuous with various setae and pegs; labial palpi short, with short and stout palpifer; apical segment similar to that of maxillary palpi, preapical segment with lateral tuft.

Pro-, meso- and metathorax (Figs 3; 11E, F) subtrapezoidal, slightly narrower anteriorly, broader than long; with lateral rim distinctly produced laterad. Pronotum longest, with rather inconspicuous round signa (glabrous areas) in posterior half. Meso- and metathorax distinctly shorter than prothorax. Venter of prothorax (Fig. 11E) with five sclerites: two oblique anterior (fused episternum and basisternum), two lateral (pleuron), and one posteromedial sclerite (sternellum), posterior portions of lateral sclerites strongly extended mesad, meeting posteromedial sclerite; posteromedial sclerite with posterior fringe of short setae; procoxal cavity closed posteriorly; anterior and lateral portions glabrous, few setiferous tubercles in posterior portions. Venter of meso- and metathorax (Fig. 11E) with six sclerites: two large anterior (divided basisternum), two subcircular sclerites anterolateral (divided pleuron), two meso-posterolateral sclerites (divided pleuron); coxal cavities open posteriad; setiferous tubercles sparse on median portion; lateral portions almost glabrous. Posterior margin of anterior sclerites with fringe of setiferous tubercles.

Legs (Figs 11E, F) moderately long (compared to larvae of other genera), but much shorter than in adults, similar in shape and length, with scattered ramose squamose sensilla and additional trichoid sensilla at femora and tibiae. Coxae large, subtrapezoidal; trochanter shorter, subtriangular; femora subconical, broadest distal; tibiae subcylindrical, longest segment, narrower than femur, broadest basally. Claws elongate, strongly bent (basal to distal part in rectangular angle) with one subbasal trichoid tooth.

Abdomen (Figs 3; 11 A–D, J–L). Segment IX with large, ventral, subtrapezoidal operculum (Fig. 11J). Segments I–VIII similar in shape, subrectangular in dorsal view. Retractable anterior portion with squamose asperities (Fig. 11A); posterior margin dorsally and ventrally with a rim of squamose setae (Fig. 11D). Remaining median portions of terga covered with setiferous tubercles, most densely at the sagittal area, forming slightly elevated dorsosagittal carinae at the posterior portions of segments I–VIII and the subanterior portion of segment IX (Fig. 11K). Ventral sclerites of segments I–VIII subrectangular, increasingly fused with pleural sclerites from 1st to 8th segment (pleural sclerites not distinguishable in segments VII and VIII); ventral sclerite of segment I with sagittal ridge in anterior third (Fig. 11E). Segment IX (Figs 11 J–L) elongate, conical, apex not emarginate. Operculum (Fig. 11J) c. double as long as broad, medially depressed, rugose, laterally with rim of trichoid setae, with a pair of hooks inserted at median dorsal (inner) side (Fig. 11L). Gill chamber with long, ramose gill tufts overreaching the opercular margin (Fig. 11L).

Variation between larval instars.

Almost the entire material studied belongs to the final instar stage. The two presumably prefinal instar specimens do not vary conspicuously from the description above. The legs appear slightly broader and shorter in relation to the body and their setae patterns are slightly different.

Distribution.

Only known from Palawan and Mindoro (Freitag & Pangantihon, 2010).