Hydroporus bithynicus, Hernando, Carles, Aguilera, Pedro, Castro, Agustín & Ribera, Ignacio, 2012

Hernando, Carles, Aguilera, Pedro, Castro, Agustín & Ribera, Ignacio, 2012, A new interstitial species of the Hydroporus ferrugineus group from north-western Turkey, with a molecular phylogeny of the H. memnonius and related groups (Coleoptera: Dytiscidae: Hydroporinae), Zootaxa 3173, pp. 37-53 : 38-43

Hydroporus bithynicus sp. n.

( Figs 1–6 )

Type locality. Turkey, Bolu province, stream between Yeniçaga and Mengen.

Type material. HOLOTYPE ( MNCN): male, labelled “ TURKEY 0 5 BOLU 24.4.2006 / Rd. 750 btw Yeniçaga & Mengen / fast stream in mixed forest / 844 m N40º50'49'' E32º03'47.5'' / Hernando,Aguilera,Castro&Ribera leg.”, plus printed red Holotype label. Aedeagus extracted and mounted in DMHF on a transparent label pinned with the specimen. PARATYPES ( IBE, MNCN, NMW, BMNH, CAC, CCH, CHF): 5 males, 3 females, same data as holotype with paratype labels. One male paratype was used for DNA extraction, voucher No. MNCN-AI782 (ref MNCN-ADN collection 24128).

Diagnosis. Hydroporus bithynicus sp. n. has to be included among the species of the H. ferrugineus subgroup sensu Fery (1999) as it has uniform pale colour, lateral depressions at the base of the pronotum with a deeper punctation, a dorsally symmetric male aedeagus and the female gonocoxa do not have an angularity on the inner side ( Fery 1999). Of the known species of the H. ferrugineus subgroup, H. bithynicus sp. n. is the flattest, narrowest and more parallel sided. The eyes are also smaller than in the other two species, which is particularly evident in ventral view. The aedeagus has also a characteristic shape, unlike H. ferrugineus and H. sanfilippoi Ghidini, 1958 (see Fery 1999: figs 68, 70).

Description. Total length 3.7–4.0 mm, maximum width 1.7–1.8 mm. Body elongate, narrow, sides parallel; lateral outline almost continuous; pronotum slightly wider than base of elytra, as wide as maximum width of elytra ( Fig. 1 ). Colour uniformly testaceous, ventral side darker.

Head ( Figs 1 , 2 ): wide; surface finely microreticulated, with polygonal, isodiametric cells; covered with very fine, dense punctation; space between punctures 2–3 times wider than their diameter. Two small clypeal fossae; periocular area slightly depressed. Eyes small, not prominent. Maximum diameter of eye (seen from above) ca. 11– 12 ommatidia (15–16 in H. sanfilippoi ); surface of ommatidia transparent, pigmented area below cuticle smaller than area covered by ommatidia ( Fig. 2 ).

Pronotum ( Figs 1 , 2 ): transverse; sides strongly bordered, slightly arched. Surface microreticulate, stronger and with larger cells than on head; punctation on disk sparser and stronger than on head; near posterior angles punctation denser, with a more rugose appearance. Anterior margin with irregular row of coarse punctures. Anterior angles with a group of very long setae. Hind wings apparently well developed.

Elytra ( Fig. 1 ): parallel sided, maximum width behind middle; surface covered with dense and strong punctation; microreticulation strong, cells wider than on pronotum and head, isodiametric. Without regular rows of punctures; with some isolated coarser punctures with setae less erect that those of regular punctures, forming loose series on the elytra. Margins with a series of very long setae, from shoulder to apex.

Ventral darker than dorsal side; metaventrum and first two or three abdominal ventrites dark brown; surface of metaventrite covered with regular, coarse and sparse punctation, space between punctures ca. 3 times wider than their diameter; covered by strong reticulation, cells slightly transverse ( Fig. 3 ). Abdominal ventrites with weaker punctation, more disperse; surface microreticulated, with smaller cells than on metaventrite ( Fig. 3 ). Posterior margin of metacoxal process slightly sinuate, medially protruded backwards ( Fig. 3 ).

Male: pro- and mesotarsi slightly dilated; claws unmodified. Aedeagus as in Figs 4-6 .

Etymology. Named after Bithynia, ancient kingdom of the NW coast of Anatolia and Roman province. The specific epithet is an adjective in the nominative singular.

Distribution and habitat. So far only known from the type locality, a fast-flowing stream in a well preserved mixed forest in north-west Turkey ( Figs 7–9 ). All specimens were found in a small pool with upwelling spring water (ca. 1 m diameter, few centimetres deep) on the side of the river. The pool had a stony substratum without vegetation, with some algal and bacterial grow, and was fed by underground water upwelling through the bottom ( Figs 7, 9 ).

The habitat and the external morphology, in particular the reduced eye size and pigmentation and the presence of long sensory setae on pronotum and elytra, suggest that the species is an inhabitant of the interstitial water, only accessible in particular circumstances – in this case, an upwelling spring. The other two species of the group, although with an apparently less modified morphology (they are less flat, with larger eyes) have been reported from similar habitats, or, in the case of H. ferrugineus , from deep inside caves ( Franciscolo 1979; Foster & Friday 2011). The specimen of H. sanfilippoi sequenced here (Table 1) was collected in the small pools of a minuscule stream formed by upwelling water while there was heavy rain: short after the specimen was collected the rain stopped and the stream dried out completely. Only after some additional rain during the next days it was flowing again, and more specimens could be found. The preference for very small running water bodies or interstitial habitats seems to be shared between the species of the H. ferrugineus , memnonius and longulus groups (see below), and has been suggested as a possible reason for the abundance of the local endemics in the group ( Fery 2009; Hájek & Fikáček 2010).

Figures

FIGURE 1. Habitus of Hydroporus bithynicus sp. n. (paratype male, NMW, photo: M. Brojer).

FIGURES 2 – 3. Hydroporus bithynicus sp. n. (paratype male, DNA voucher specimen MNCN-AI 782); 2) head and pronotum; 3) detail of the metacoxa (photos: A. Castro).

FIGURES 4 – 6. Hydroporus bithynicus sp. n. (paratype male, DNA voucher specimen MNCN-AI 782); 4) median lobe of the aedeagus, lateral view; 5) median lobe of the aedeagus, ventral view; 6) right paramere, lateral view. Scale bar: 1 mm (photos: A. Castro).

FIGURES 7 – 9. Habitat of Hydroporus bithynicus sp. n.; 7) detail of the spring in which all specimens were found; 8) general view of the stream between Yeniçaga and Mengen; 9) two of the authors (P. Aguilera and C. Hernando) next to the spring (photos: I. Ribera).