Hydroporus tibetanus Zaitzev, 1953

Jia, Fenglong, Zhao, Shuang & Fery, Hans, 2012, Hydroporus sejilashan sp. n., a new diving beetle of the acutangulus - complex from Xizang, China (Qinghai-Tibet Plateau), and notes on other taxa of the genus (Coleoptera, Dytiscidae, Hydroporinae), Zootaxa 3223 (1), pp. 55-67 : 61-62

Hydroporus tibetanus Zaitzev, 1953

Hydroporus tibetanus was described by Zaitzev (1953: 169; see also the English translation Zaitzev 1972: 179) from Amdo ( China, Qinghai [Tibet]; ca. 32.27N 91.68E; altitude ca. 4700 m; star "a" in Figs. 13–14 ) as "closely related to" Hydroporus nigrita (Fabricius, 1972) and, thus, was treated as member of the nigrita -group by Nilsson (2001: 163). Zaitzev seemingly overlooked the shape of the metacoxal lines and the setation on the metatrochanters; he wrote "... dorsum and venter more shining; body markedly more weakly shagreened [compared with H. nigrita ] ..." Shaverdo (2004: 260) studied the two syntypes of H. tibetanus (ZISP), designated a male lectotype ( Fig. 4 ) and found out that—due to the widely smooth elytra—this species belongs to the planus - group and, in particular, to the acutangulus -complex because of the parallel metacoxal lines and the setal fringe on each metatrochanter. We have also studied the types of this taxon and can confirm Shaverdo's observations, but want to add that the base of the median lobe as well as the right paramere of the lectotype are both damaged. Additionally, it must be mentioned that the lectotype lacks the posterior claw of the left protarsus (the anterior claw is present and clearly not strongly curved near base), the anterior claw of the right protarsus, the last three tarsomeres of the left mesotarsus, the last three tarsomeres of the left metatarsus and the complete right metatarsus. We want to point to the fact that the lectotype is reticulated more or less as typical H. acutangulus : entire surface shiny; pronotum smooth on disc, reticulate laterally; elytra smooth in first third, behind with some indistinct short lines between punctures, before apex with distinct small meshes, but also here not matted. In the female paralectotype the elytral reticulation with small meshes is already present in the second third and becomes more impressed towards the apex; the smooth areas on the pronotum are even more extended than in the male. The entire upper surface appears by no means less shiny than that of the male.

After Zaitzev's description (1953), no subsequent specimens of H. tibetanus have been collected. The species was only listed in some catalogues ( Hua 2002, Nilsson 1995, 2001, 2003, 2011, Nilsson & Fery 2006) or treated in overviews of members of the nigrita - or planus -groups ( Fery & Pesic 2006, Guéorguiev 1966, Shaverdo 2004). Recently, however, we have studied several specimens which we could determine as this species. The collecting data are as follows: 3.7.1999, Sichuan, Ganzi (= Garzê) Tibetan Autonomous Region, Batang County, Shaluli Mountains, 57 km NE Batang, pools, ca. 4500 m, A. Pütz leg. (CAP, CHF) (star "b" in Figs. 13–14 ). These specimens are similar to the lecto- and paralectotype of H. tibetanus in most respects, in particular, their upper surface is shiny in both sexes. They are, however, somewhat darker than the types. Some females are reticulated on the entire elytra and large parts of the pronotum. Other females have the upper surface reticulated as the female paralectotype of H. tibetanus . The median lobe of the males in ventral view ( Fig. 8 b) is similar to that of the lectotype of H. tibetanus ( Fig. 8 a). We are not absolutely sure about the identity of Pütz' specimens, but since no other material from the region around Amdo has become available, we assume that this population belongs to H. tibetanus . Measurements: Lectotype (male): TL: 3.2 mm, MW: 1.6 mm, TL/MW: 2.00; paralectotype (female): TL: 3.2 mm, MW: 1.65 mm, TL/MW: 1.94; specimens from Ganzi: TL: 2.95–3.3 mm, MW: 1.5–1.7 mm, TL/MW: 1.9–2.03.

We prefer not to present a key to species at this time because any key for this group would be rather primitive and not very useful. Construction of a key for this species group should be postponed until the variability of all group members is known sufficiently. We compare below the new species with the types of H. tibetanus as well as with specimens from the population of H. tibetanus from Ganzi:

- Hydroporus sejilashan sp. n. is larger and slightly less elongate than H. tibetanus .

- In dorsal view the sides of the pronotum are less curved in H. sejilashan sp. n. In H. tibetanus the base of the pronotum is not broader than the base of the elytra.

- The new species has the entire surface reticulated and matt. Hydroporus tibetanus has a shiny surface (also in reticulated areas) and in the males and most females the reticulation of the elytra is restricted to the apex.

- Hydroporus sejilashan sp. n. has the dorsal and ventral surface almost totally black, only the tarsi and first antennomeres are dark brownish. The lectotype of H. tibetanus has the tarsi somewhat lighter, the antennomeres are all more or less uniformly brown, and the elytra are dark brown; the female paralectotype and the specimens from Ganzi, however, are generally darker than the lectotype.

- The punctation of the surface is distinctly coarser in H. tibetanus , and also denser on head; in the posterolateral depression of the pronotum and before the posterior margin (except centrally) it is very coarse and longitudinally deformed; the punctures of the irregular puncture line behind the anterior pronotal margin are also very coarse and in part longitudinally deformed. In the new species, however, the punctation is generally simple and by far not so coarse in the respective areas. Due to the coarser elytral punctation, the elytral puncture lines appear slightly less distinct in H. tibetanus .

- The first three protarsomeres are more dilated in H. sejilashan sp. n.; especially the second protarsomere is almost two times as broad as long and the third one more or less of round shape; the differences between male and female protarsomeres are obvious. In the lectotype of H. tibetanus the second protarsomere is only one and a half times as broad as long and the third one is more elongate; differences between the protarsomeres of males and females are rather slight. The male mesotarsomeres of the new species are also broader than those of the females and broader than those of H. tibetanus .

- Antennomeres five to eleven are slightly longer in the new species.

- The median lobe of H. sejilashan sp. n. is in ventral view slightly narrower in the apical third and more pointed (compare Figs. 6 a with 8a–b). In lateral view ( Fig. 6 b) a comparison is impossible because the median lobe of the lectotype of H. tibetanus is partly destroyed. A comparison with that of a male from Ganzi ( Fig. 8 c) shows that the lobe of the new species is less bent near the base and slightly broader in apical third.

Figures

FIGURE 13. Distribution of: Hydroporus acutangulus (circles), Hydroporus polaris (squares), Hydroporus tuvaensis (triangle), Hydroporus tibetanus (stars), and Hydroporus sejilashan sp. n. (encircled star); the circle with question mark refers to the type locality of Hydroporus sumakovi (see text). Red squares indicate capitals of countries / provinces or other important and well-known cities.

FIGURE 14. Distribution of (enlarged map): Hydroporus tuvaensis (triangle), Hydroporus tibetanus (stars), and Hydroporus sejilashan sp. n. (encircled star). Red squares indicate capitals of countries / provinces or other important and well-known cities.

FIGURES 1 – 5. Habitus of: (1) Hydroporus acutangulus, (2) Hydroporus polaris, (3) Hydroporus tuvaensis, (4) Hydroporus tibetanus (lectotype), (5) Hydroporus sejilashan sp. n.

FIGURES 6 – 10. (6) Median lobe of Hydroporus sejilashan sp. n. in ventral (a) and in lateral view (b); (7) left paramere of Hydroporus sejilashan sp. n.; (8) median lobe of Hydroporus tibetanus in ventral view: (a) lectotype, (b) specimen from Ganzi; same in lateral view: (c) specimen from Ganzi; left paramere of Hydroporus tibetanus; (9) specimen from Ganzi, (10) lectotype.