Ancyronyx montanus Freitag

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 : 66-69

Ancyronyx montanus Freitag sp. n. Figs 7, 816 A–P17A–K

Type material.

Holotype ♂ (NMW [FR012]) "PHIL.: Palawan, P.Princesa; Concepcion, Taranaban R. trib.;mount.creek c.8km upstr.; dist. prim. forest; riffle;rocks, boulders,roots; c.450m asl 10°05'N, 119°01'E, 28.1.1995 leg. Freitag (16f)M", terminal parts of abdomen incl. aedeagus glued separately, two tarsi lacking. Paratypes: 1♀ (NMW), 1L (0.37) (ZSM [FR038]): same data as holotype; 2♂, 4L (0.30, 0.31, 0.36, 0.37) (SMTD, UPLB, NMW, CFP) "PHIL.: Palawan, Roxas, Bgy.Dumarao downstr. New Rizal Falls, sec. forest, c. 120m asl; boulders, sand, CPOM; 10°28'10"N, 119°19'52"E 05.12.1994, leg. Freitag (135)M".

Adult description.

Body 1.82-1.88 mm long (CL), 0.79-0.83 mm broad (EW), 2.2-2.4 times as broad as wide (CL/EW). Body form elongate, moderately convex dorsally.

Colouration (Fig. 7) predominantly dark brown to black; legs pale brown to dark brown, (articulations slightly darker); claws and antennae pale brown (distal antennal segment darker); elytra without pale patches; ventral side slightly paler than dorsal, but still dark brown.

Head (Figs 7; 16A, B) 0.41-0.45 mm broad (HW); ID 0.28-0.26 mm; labrum (Fig. 16A) micropunctate, moderately densely covered with long and trichoid setae; frons (Fig. 16A) punctate; clypeus (Fig. 16A) reticulate, moderately densely pubescent; frontoclypeal suture almost straight, slightly impressed. Eyes protruding (Figs 16A, B). Antennae (Fig. 16A) 11-segmented, slender, very slightly longer than head broad. Gula (Fig. 16B) microreticulate, moderately pubescent; gular sutures inconspicuous.

Pronotum (Figs 7; 16C) 0.54-0.65 mm long (PL), 0.52-0.57 mm broad (MW), slightly longer than wide (PL/MW), widest at about posterior 0.2, distinctly narrower than elytra, anteriorly attenuate; anterior margin slightly acuate; margin between pronotum and hypomeron inconspicuous; anterior transverse groove distinct and moderately deeply impressed, medially shallower; anteriorly and posteriorly of transverse groove gently vaulted; posterolateral oblique grooves shallow, inconspicuous; pronotal surface entirely distinctly reticulate; hypomeron reticulate. Prosternum (Fig. 16D) reticulate; prosternal process distinctly narrower medially, medially impressed, posterior margin obtuse.

Scutellum subpentagonal, anteriorly slightly impressed, glabrous. Elytra (Figs 7; 16E) elongate, 1.16-1.35 mm long (EL), c. 1.6-1.8 times as long as wide (EL/EW), almost parallel-sided in anterior 0.1-0.7, posteriorly roundly convergent to apices; elytral apices separately rounded; with c. 10 longitudinal, quite regular, deeply impressed rows of punctures (five strial rows between suture and shoulder); punctures large and deeply impressed; interstices and intervals convex, granulous; lateral elytral gutter moderately broad; humeri prominent. Mesoventrite (Fig. 16D) very short, with longitudinal impression, with few deep punctures. Metaventrite (Fig. 16F) prominent, with distinct discrimen, subanteriorly and medially impressed along the groove, lateral parts punctate to reticulate; anepisternum 3 prominent, with two irregular rows of punctures. Hind wings present; venation not examined.

Legs slightly longer than body; pro- and mesocoxae large, globular; metacoxae only slightly protruding laterally; femora, tibiae, and tarsi (except distal tarsal segment) covered with elongate setiferous tubercles; tibiae distally with a distinct rim of setae; claws (Fig. 16G) well developed, rather gently curved; base of each claw with three teeth, distal one largest, basal one shortest.

Ventrites 1-4 almost glabrous, posteromedially punctate, reticulate anteriorly and laterally; ventrite 5 (Figs 16 H–J), moderately densely covered with short adpressed setae emerging from flat tubercles; lateral projection small and inconspicuous.

Sternite IX (spiculum gastrale) as in Fig. 16K; apical margin almost straight, only very slightly emarginate; paraprocts short, not reaching apical margin.

Aedeagus (Figs 16 L–N) very similar to that of Ancyronyx punkti (see Freitag & Jäch, 2007: Figs 13a, b), but distinctly larger, 440-490 µm long. Median lobe moderately long and slender, distinctly widened subapically (c. 80 µm broad), slightly curved ventrad, with numerous distinct microtube-like structures ending sublateroapically; ventral sac weekly sclerotized; fibula well sclerotized, conspicuous in transillumination (Fig. 16L); corona well developed. Phallobase asymmetrical, slightly widened ventrally, with conspicuous, strongly sclerotized margin; basolateral (penile) apophyses rather short. Parameres elongately subtriangular with basal margin strongly emarginate (lateral view, Fig. 16N), reaching about basal 0.63 of aedeagus, not contiguous ventrally.

Ovipositor (Fig. 16O). Total length c. 620 µm. Stylus slender, slightly bent outwards (partly broken off in specimen examined). Coxite long and slender, distal portion distinctly elongate, with several comparably long, lanceolate setae, most densely set at apex; mesal margin densely pubescent; basal portion c. half as long as distal portion, with same type of setae in distinct patterns as in Fig. 16O. Valvifer about as long as coxite; fibula (mesal, longitudinal sclerotisation) genus typical as in Fig. 16O.

Secondary sexual characters. Sternite VIII in female (Fig. 16P) with median strut apically widened, almost truncate, posterior portion slightly pubescent; sternite VIII in male weakly sclerotized, median strut distinctly shorter than in female. Ventrite 5 in female subtriangular (Fig. 16I), in male (Fig. 16J) shorter and suboval. Tergite VIII in female (Fig. 16Q) longer than broad; condyles more or less straight and prominent; reticulations only conspicuous laterally. Tergite VIII in male (Fig. 16R) broader than long, reticulation more developed than in female covering apical half; basal half patterned with lines of asperities; condyles not distinctly curved, overreaching anterior margin.

Adult differential diagnosis.

Ancyronyx montanus superficially resembles dark specimens of Ancyronyx patrolus (Freitag & Jäch 2004: Fig. 4), from which it can be easily distinguished by the larger size, slenderer body (EL/EW), the entirely reticulate pronotal surface that lacks any glabrous areas, the medially narrowed prosternal process and its genital characters.

Larval description (based on 6th instar).

Colour as in Fig. 8: very similar to that of Ancyronyx patrolus , but overall darker and somewhat shiny; legs entirely pale brown to yellowish. Mouthparts and surrounding portions not distinctly darker than dorsal and ventral head portions. Without pale pattern at dorsal thoracic and abdominal segments; only apex of abdominal segment slightly paler. Ventral side pale brown.

HW 0.37-0.41 mm; entire larva up to 3.3 mm long. Body shape as in Ancyronyx patrolus , except for the following: entire body more vaulted in cross section; dorsal sagittal area flat, with rather indistinct sagittal line, without carina at all thoracic and abdominal segments. Setiferous tubercles at dorsal side rather flat, not as elevated as in the other species (Fig. 17A), those of ventral side very flat and inconspicous (Fig. 17B). Setae originated from tubercles (Figs 17 A–C) lanceolate to trichoid and distinctly longer than in the previous species. Posterolateral abdominal projections comparably small, attenuate, distinctly larger at anterior abdominal segments (Figs 8, 17C). Trichoid teeth not reaching middle of subsequent abdominal segment when that retracted.

Head (Figs 8, 17D-F) basically as in the previous species, but with the following varying characters: broadest posterior 0.25, laterally slightly convex. Glabrous area with stemmata not exposed. With few long, trichoid setae on lateral sides and one dorsolateral pair of long double setae (Figs 17 D–F). Entire head more or less densely covered with squamose to fascicular setae originated from slightly elevated tubercles and additionally with several moderately long trichoid setae (Figs 17 E–F). Frontal suture V-shaped. Fasciculate setae at subbasal fringe of clypeus very long, overreaching labrum (Fig. 17E); labrum with large fasciculate setae (Fig. 17E). Gula, maxillae and labium (Fig. 17F) almost as in Ancyronyx minerva , but with few squamose setae and shorter maxillary and labial palpi. Mandibles as in Fig. 17E. Antennae (Fig. 17E) almost as in Ancyronyx patrolus , scapus with large plumose setae.

Pro-, meso- and metathorax as in Figs 8 and 17G, H. Thoracic terga with small round signa in sublateral portions; sagittal line rather inconspicuous. Thoracic venters (Figs 17G, H) with asperities and irregularly distributed setiferous tubercles; anterior sclerites and posterior portion of lateral sclerites of prothorax (Fig. 17G) densely covered with tubercles. Posteromedial sclerite bald and rugulose. Meso- and metathorax with scattered setiferous tubercles at distal portions of all sclerites, lateral sclerite portions densely covered with asperities (Fig. 17H). Legs (Fig. 17I) similar to those of Ancyronyx patrolus , but with comparably long and slender femora (c. as long as tibiae); coxae with distinct asperities; other surfaces rather glabrous. Claws slender and long, moderately bent (Fig. 17I).

Abdomen (Figs 8; 17 A–C, J–K) without any elevations or carinae at dorsal sagittal area; segments I–VI with a pair submedian trichoid setae, that are distinctly longer than surrounding lanceolate to trichoid setae (Fig. 17A). Ventral sclerite of first segment without sagittal ridge (Fig. 17H). Apex of segment IX distinctly emarginate (Fig. 17K). Operculum (Fig. 17J) subovate, medially slightly impressed, with scattered lanceolate setae in apical and lateral portions.

Variation between larval instars.

The two specimens of prefinal instar stage vary most conspicuously from the above description by the overall paler brown colour, the more conspicuous dorsal setiferous tubercles that let the pronotal signa appear clearly as well as the slightly crested (in cross-section subtriangular) abdominal segment IX.

Larval differential diagnosis.

The species is easily distinguishable from other Palawan species by the lack of any dorsosagittal carinae or elevations, the dark, shiny dorsal colour, its rather large size and the rather shallow dorsal tubercles bearing comparably long, lanceolate to trichoid setae.

Distribution.

Only known from the type locality in central Palawan and one site in northern Palawan (Fig. 20).

Etymology.

The species is named in reference to the remote mountainous river habitats where it was exclusively recorded from.