Carabhydrus niger Watts, 1978

Hendrich, Lars & Watts, Chris H. S., 2009, Taxonomic revision of the Australian predaceous water beetle genus Carabhydrus Watts, 1978 (Col. Dytiscidae, Hydroporinae, Hydroporini), Zootaxa 2048 (1), pp. 1-30 : 18-19

Carabhydrus niger Watts, 1978

( Figs 9 , 22, 23 , 28 , 32, 33 )

Carabhydrus niger Watts, 1978: 27 ; Zwick (1981: 170); Watts (1985: 23); Lawrence et al. (1987: 334); Larson & Storey (1994: 895, 900); Nilsson (2001: 144); Watts (2002: 32, 44).

Type locality: Cave 35, Murrindal, Victoria, Australia .

Type material: Holotype: 1 male: “ Cave 35 Murrindal Victoria 27.III.1964 E.Hamilton-Smith ”, “SAM B50580”, “ Holotype Carabhydrus niger Det.C.Watts 1976 ” [hw label by Chris Watts] ( SAMA) . Paratype: 1 male: “ Cave 35 Murrindal Victoria 12.IV.1963 E.Hamilton-Smith ”, “SAM B50306”, “ Paratype Carabhydrus niger Det. C. Watts 1976 ” [hw label by Chris Watts] ( SAMA) .

Additional material studied (85 specimens): New South Wales: 1 ex., C NSW, 3 km W Albion Park, North Macquarie Road at creek crossing, 20 m, 30.X.2006, 34.34.337S 150.43.456 E, L. & E. Hendrich leg. ( NSW 87 ) ( CLH) ; 1 ex., C NSW, 13 km NNW Dungog, Williams River, Tillegra Bridge , 109 m, 19.X.2006, 32.19.078S 151.41.250 E, L. & E. Hendrich leg. ( NSW 84 ) ( ZSM) ; 1 ex., NSW EPA Survey MRHI TOWA 15, Wallagaraugh River , 37.15.21S 149.39.42E, 4.III.1996, Joanne Ling leg. ( AM) ; 1 ex., NSW EPA Survey MRHI Murchison River (m1), Stony Creek , 35.39.26S 147.45.32E, 19.III.1996, Natacha Waddell leg. ( AM) ; 1 ex., NSW EPA Survey MRHI Murchison River (m1), Stony Creek , 35.39.26S 147.45.32E, 22.XI.1995, Natacha Waddell leg. ( AM) ; 1 ex., Delegate River , I.1938, F.E. Wilson leg. ( NMV) ; 1 ex., Williams R 10 km N Dungong, 16.VIII.1977, C. Watts leg. ( SAMA) ; 1 ex., Namoi River 4 km N of Bendermeer, 7.XII.2002, 30.50.47S 151.09.52 E, A. Glaister leg. ( SAMA) ; 1 ex., Boyne Creek mt Yadboro Rd , 26.XI.2001, 35.23.45S 150.16 21 E, A. Glaister leg. ( SAMA) . Victoria: 1 ex., Mitta Mitta River, 3 km below Dartmouth dam site, Loc. I-SB 2, 31.I.1975 ( NMV) ; 1 ex., Cobungra River, Anglers Rest , 4.II.1974, A. Neboiss leg. ( NMV) ; 5 exs., Sardine Creek 30 km N Orbost, 30.XI.1998, C. Watts leg. ( SAMA) ; 1 ex., Junction Macalister- Wellington Rivers , 6.XII.1977, N.M.V.Survey Dept G.R.E.S. Mc 20 no 4 ( SAMA) ; 1 ex., Thomson River Low Saddle, Tck , 3.V.1977, N.M.V. Survey Dept G.R.E.S.115 no2 ( SAMA) ; 1 ex., Jordan R –BB Ck Junction, Jericho , 12.XI.1977, N.M.V.Survey Dept G.R.E.S.710 no ( SAMA) . Tasmania: 1 ex., Australia , Tasmania, 4.4 km SE Weldborough, Nothofagus Forest , 460 m, 12.-14.II.1980, A. Newton & M. Thayer leg. ( ANIC) ; 2 exs., Tasmania, Douglas Creek , 4 km S Mt. Oakleigh, 41.51S 146.03E, 880 m, 12.-15.II.1991, Kicksampling, A. Calder, W. Dressler leg. ( ANIC) ; 5 exs., NW Tasmania, 12 km SW Mawbanna Black River Picnic Area , 31.I.1998, L. Hendrich leg. (Loc. 22/63) ( CLH) ; 5 exs., NW Tasmania, 2 km W Mawbanna Detention River , 45 m, 1.II.1998, 40.57S 145.29E, L. Hendrich leg. (Loc. 23/64) ( CLH, NMW) ; 1 ex., NW Tasmania, Detention River , 2.5 km SW Mawbanna, 45 m, 12.XII.2006, 40.57.317S 145.29.380 E, L. & E. Hendrich leg. (TAS 141) ( ZSM) ; 35 exs., NW Tasmania, Detention River 4 km W Montumana, 21.I.2000, C. Watts leg. ( SAMA) ; 11 exs., NW Tasmania, Detention River 2 km W Montumana, 27.XI.2000, C. Watts leg. ( SAMA) ; 8 exs., NW Tasmania, Black River 9 km NW Mawbanna, 21.I.2000, C. Watts leg. ( SAMA) ; 1 ex., NW Tasmania, Black River 5 km NW Mawbanna, 27.XI.2000, C. Watts leg. ( SAMA) ; 7 exs., S. Esk River , 1976, R. Norris leg. ( SAMA) ; 1 ex., Mersey River, Mole Creek Karst National Park , 19.I.2000, C. Watts leg. ( SAMA) .

Re-description: Measurements: TL = 2.95–3.1 mm, TL-H = 2.7–2.9 mm, MW = 1.3–1.35 mm.

Color ( Fig. 9 ): Dark brown to almost black except of anterior part of clypeus, mouthparts, ventral surface of head and thorax, and basal and apical margins of sterna 4–6, dark rufous, inner and outer edge of epipleura black. Antennae and legs yellowish brown, without infuscation, palest on pro- and mesocoxa, trochanters, base and apex of femora and tibiae, and pro- and mesotarsi.

Sculpture: Head anterior to dorsal impression with deep punctures separated by a distance about equal to their own diameters, and a few sparse, minute punctures; interspaces smooth and shiny without microreticulation except frontal foveae coarsely reticulate and anterior margin of clypeus with transverse lines; head posterior to transverse impression with coarse punctures medially and laterally posteriad to eyes. Pronotum similar to C. mubboonus . Elytron with dual and coarse punctuation, more dense than pronotum; interspaces smooth basally but medially. Evident microreticulation covering apical half in female but not visible in male, epipleuron with dense, more or less contiguous punctures. Ventral surface similar to C. mubboonus .

Structure: Head broad, lateral margins of clypeus somewhat produced laterally above base of antenna; frontal fovea distinct, ovate; dorsal surface with a strong transverse impression between posterior margins of eyes; maxillary and labial palpi each with apical palpomere fusiform.

Pronotum in dorsal aspect cordiform with point of maximum width at about anterior third of length, lateral margin in dorsal aspect more or less evenly rounded except shortly sinuate before obtuse posterolateral angle; lateral bead sharply defined, narrow; basal margin slightly lobed medially; disc broadly convex in apical half, flattened basally and narrowly flattened adjacent to lateral margin; disc with a pair of longitudinal impressions, each extending from convex mediolateral portion of disc almost to hind margin and strongly limited on outer side by a more or less carinate ridge, mesal margin less distinct; all specimens with one to several additional shorter and more irregular rugae or impressions as well as larger punctures along basal margin adjacent to the major impressions. Scutellum visible, short and broad.

Elytra together elongate-oval with point of maximum width behind middle, sides converging basally; disc of each elytron with a shallow medial and a shallow sublateral, longitudinal groove each bearing unserial larger punctures, and a much less evidently defined lateral groove adjacent to lateral margin; mesal groove beginning approximately opposite basolateral impression of pronotum, well defined on basal two-thirds, becoming shallower apically; sublateral groove interrupted and formed by several serial deeper depressions, starting slightly mesad of humeral angle, more narrower and shallower than mesal groove.

Ventral surface, similar to C. mubboonus but legs larger and hind legs more slender; metatibia straight, evenly broadened from base to apex, natatorial setae absent from ventral face (face bearing apical spurs) in both sexes, present on mesal face but differing in degree of development between sexes, longer metatibial spur about two-thirds length metatarsomere 1; metatarsomeres elongate; metatarsal claws equal.

Male: Antenna broadened, antennomeres 5–7 slightly and progressively widened, 8–10 about as wide as long, and 11 strongly fusiform. Profemur with anteroventral margin bearing four basal and a medial, short, stout spines. Protibia with mesal margin bearing a low, obtuse, subapical tooth and a basal row of short, pale setae. Protarsomeres 1–3 slightly dilated, tarsomere 1 with a pair of large oval scales in addition to numerous small adhesive setae. Mesofemur clavate, ventral margin flattened and bearing a brush of elongate golden setae; with inner margin of mesotibia without subapical tooth. Metatibia with basal natatorial setae of mesal face elaborated into a brush of long, yellow setae. Paramere sclerotized, broad, ovate, shorter than aedeagus, glabrous except for a long apical seta; aedeagus ( Figs 22, 23 ) in ventral aspect of C. niger with deep, broad subapical notch on each side delimiting broad, and an apically bilobed and broadly rounded apex.

Female: Metatibia with a small group of natatorial setae arising in basal half of mesal face. Females are shorter than males. Measurements: TL = 2.95–3.00 mm, TL-H = 2.20–2.25 mm, MW = 1.00– 1.10 mm.

Differential diagnosis: In color and shape of body C. niger superficially resembles C. mubboonus and C. monteithi although the latter has a narrower appearance due to the pronotum being more strongly sinuate laterally with the lateral margins more or less parallel before the right-angled hind angles. Specimens of C. mubboonus have the elytral grooves deeper and broader than C. niger . Furthermore, C. niger is larger than both species being more slender and elongate than C. mubboonus . From C. monteithi and C. mubboonus it differs clearly by the form of the median lobe. In ventral aspect the aedeagus of C. niger ( Fig. 22 ) has a deep, broad subapical notch on each side delimiting broad, and an apically bilobed and broadly rounded apex, whereas in C. monteithi ( Fig. 18 ) and C. mubboonus ( Fig. 20 ) it has a narrow subapical notch on each side, with apex subtriangular and not broadly rounded.

Distribution: The most widespread species of the genus ( Fig. 28 ). South-eastern Australia from Albion Park south of Sydney to the Victorian Alps of eastern Victoria and northern Tasmania.

Habitat: Occurring in streams and slow flowing larger rivers at an altitude from 20 m to 880 m, from more or less open country to closed-canopy forest sites. Most specimens were found in low-gradient stream or river sections where the substrate was entirely coarse sand, larger pebbles and wood yet the current was strong enough to clean the bottom of silt and leaves. In this habitat the beetles were found in areas of slow, laminar flow, generally along the inside edge of curved larger pools and runs ( Figs 32, 33 ). In NW Tasmania few specimens were observed moving around, almost all were captured by disturbing the sand and pebbles then vigorously sweeping the area with a stout aquatic net.

Figures

FIGURES 5–9. Habitus of Carabhydrus. 5—Carabhydrus turaki sp.n. (holotype, female); 6—C. stephanieae (paratype); 7—C. mubboonus (female); 8—C. janmillerae sp.n. (paratype, female); 9—C. niger (female) (scale bar 1 mm) (Photos: L. Hendrich).

FIGURES 20–27. Median lobe of aedeagus in ventral and lateral view (scale bar 0.2 mm): 20, 21–Carabhydrus mubboonus; 22, 23—C. niger; 24, 25—C. plicatus; 26, 27—C. storeyi sp.n.

FIGURES 28–29. Distribution of the genus Carabhydrus in Australia.

FIGURES 30–35. Habitats of 30,31—C. andreas, Gibraltar Falls, downstream and upstream (ACT), November 2006; 32—C. niger, NW Tasmania, Detention River, 2.5 km SW Mawbanna, December 2006; 33—C. niger, 13 km NNW Dungog, Williams River, Tillegra Bridge, October 2006; 34, 35—C. innae sp.n., Thomson River in Baw Baw National Park (Victoria) (Photos L. Hendrich).

FIGURES 10–19. Median lobe of aedeagus in ventral and lateral view (scale bar 0.2 mm): 10, 11—Carabhydrus andreas and 12, 13—C. innae sp.n.; 14, 15—C. innae sp.n. right paramere (14) and first two mesotarsal segments (15) in dorsal view (scale bar 0.2 mm). Median lobe of aedeagus in ventral and lateral view: 16, 17—C. janmillerae sp.n. and 18,19—C. monteithi.