Hydroscapha granulum (Motschulsky, 1855)

Falamarzi, Shahram, Pütz, Andreas, Heidari, Mohammad & Nasserzadeh, Hiva, 2010, Confirmed occurrence of Hydroscapha granulum in Iran, with notes on its biology (Coleoptera: Myxophaga: Hydroscaphidae), Acta Entomologica Musei Nationalis Pragae 50 (1), pp. 97-106 : 99-104

Hydroscapha granulum (Motschulsky, 1855)

( Figs. 1–19 )

Redescription. Measurements: Length of fore body (i.e., the distance between the anteri- or margin of the head and the posterior margin of the elytra): 0.6–0.7 mm. Elytral length: 0.40–0.45 mm.

Colouration: Body uniformly dark brown ( Fig. 18 ).

Antenna: Antennomere 2 long, 2.0 times longer than wide. Antennomere 8 ca 3.0 times longer than wide ( Fig. 13 ).

Male: Sternite V ( Fig. 14 ) with two tufts of setae at posterior margin; posterior margin slightly sinuate. Sternite VI without distinctly defined tufts of setae sublaterally. Posteromedian portion of sternite VII ( Fig. 12 ) slightly convex between lateral tufts of setae. Posterior margin of sternite VII without defined median projection, arrangement of postero-lateral setae irregular. Aedeagus ( Fig. 10 ) straight in lateral view, subapically narrow, gradually narrowing apicad.

Female: Sternite VI simply rounded posteriorly. Tergite VI apically rounded.

Variation. Some superficial differences were observed in the shape of the male genitalia. In some cases, the aedeagus seems slightly wider in the apical portion ( Fig. 11 ). Differences were also observed in the length of the elytra ( Fig. 17 ) and in the chaetotaxy of the surface around the tufts of setae on male sternite V ( Figs. 14–16 ).

Distribution. Distribution of Hydroscapha granulum is still insufficiently known for two reasons: (1) the beetles are easy to overlook and are therefore rather rare in the collections; (2) the taxonomic status of H. crotchi Sharp, 1874 and H. mauretanica Peyerimhoff, 1922 remains unclear. Hydroscapha crotchi was considered as a synonym of H. granulum by d’ORCHYMONT (1945) and LÖBL (1994), but is considered as a separate species occurring in Spain and Corsica by LÖBL (2003) and AUDISIO & LÖBL (2004a). Hydroscapha mauretanica from Algeria was considered as a possible synonym of H. granulum by LÖBL (1994) based on the fact that it was diagnosed from the latter species only by the slightly different proportions of the elytra (this character is variable within Hydroscapha species as illustrated in Fig. 17 ). Below, we list only the records not concerning H. crotchi and H. mauretanica .

EUROPE: Spain ( JÄCH et al. 1999), France ( d’ORCHYMONT 1945, RICHOUX & DOLEDEC 1987, LÖBL 2003), Italy ( LÖBL 2003), Serbia ( LÖBL 1994), ‘Yugoslavia’ ( LÖBL 2003, AUDISIO & LÖBL 2004b; may concern the Serbian record), Bulgaria ( HINTON 1969, JOOST 1979), Greece ( d’ORCHYMONT 1945, LÖBL 2003).

ASIA: Turkey ( Anatolia: d’ORCHYMONT 1945, LÖBL 2003); Azerbaijan (Länkäran: REITTER 1887, LÖBL 2003), Iran (Khuzestan, Andimeshk, 32°41′N, 48°15′E: LÖBL 1994; Fars, Mazandaran: this paper).

Distribution of Hydroscapha granulum and the species which may be its synonyms are illustrated in Fig. 19 .

The list of collecting sites in Iran is given in Table 1. Our study provides the first record of Hydroscaphidae in Fars and Mazandaran provinces. Several hydraenid species ( Hydraena sp. , Ochthebius sp. , Limnebius sp. ) were collected in the same microhabitats together with the Hydroscapha specimens. We also collected Sphaerius sp. ( Myxophaga , Sphaeriusidae ) at localities 2, 9 and 12. Some (possibly parasitic) mites ( Figs. 4–6 ) were observed on exposed abdominal tergites of one Hydroscapha specimen at the locality of Shaldan (loc. 1) and between algal filaments in Khavis.

Notes on biology. The egg is large in proportion to the female’s abdomen (length up to 0.2 mm; width about 0.12 mm; Fig. 1 ) and only one is developed and deposited at the time. Eggs are oval, smooth, dark brown and without sculpture on surface. We observed them attached to the algae few days after keeping beetles in rearing boxes, and dissected them also from the female body.At least three larval stages ( Figs. 7–9 ) were observed in the examined alive larval specimens. All larval stages are elongate, dark grey and strictly aquatic. Presence of larvae together with adults was detected almost in all localities (no. 2, 3, 6, 9–14). Both adults and larvae can be found in large numbers in suitable streams, especially on the rocks covered by algae in the marginal shallows ( Fig. 3 ) (see also FIKÁČEK & FALAMARZI (2010: Figs. 13–14 ) for photographs of localities of Shaldan and Reykan). An air bubble was observed under the elytra of the adults and extending behind the elytra ( Fig. 2 ). Females were observed to attract the males by moving elytra up and down.

During our study, Hydroscapha granulum was found in four different types of microhabitats, which partly correspond with those mentioned by other authors for other Hydroscapha species. Observed habitat preferences and their comparison to data of previous authors are provided in Table 2.

Figures

Figs. 1–9. Iranian specimens of Hydroscapha granulum (Motschulsky, 1855) and their typical habitat. 1 – egg size in comparison to female beetle (locality no. 6); 2 – air bubble under elytra; 3 – typical habitat of the species (rocks covered by algae, locality no. 12); 4–6 – mites (possibly parasitic) infecting Hydroscapha adults at localities 6 and 12 (4, 5 – mites on abdominal tergites; 6 – microscopic slide of the mite, scale bar 0.1 mm); 7–9 – habitus of different larval instars.

Figs. 10–18. Morphology of Iranian Hydroscapha granulum (Motschulsky, 1855). 10–11 – aedeagus, lateral view; 12 – sternite VII; 13 – antenna; 14–16 – male, sternite V; 17 – different proportions of elytra in two specimens from the same stream (localities 12 and 13); 18 – H. granulum in natural habitat (locality 9).

Fig.19. Known distribution of West-Palaearctic Hydroscapha derived from the published data (see the text for details). Asian records are mapped by full circles, Spanish record of H. granulum (Motschulsky, 1855) by JÄCH et al. (1999) by an empty circle. Species whose synonymy with H. granulum requires revision are mapped in dotted line.