Belladessus Miller and Short

Miller, Kelly B. & Short, Andrew E. Z., 2015, BelladessusMiller and Short (Coleoptera: Dytiscidae: Hydroporinae: Bidessini), New Genus for Two New Species from Northern South America: Parthenogenetic Diving Beetles?, The Coleopterists Bulletin 69 (3), pp. 498-503 : 499-500

Belladessus Miller and Short , new genus ( Figs. 1–8 )

Type Species. Belladessus femineus Miller and Short , new species, by present designation.

Diagnosis. Belladessus clearly belongs to the tribe Bidessini based on the presence of basal pronotal and elytral striae, club-shaped metatibiae, and spermathecal spine. The genus differs from other bidessine genera in the following character combination: 1) absence of occipital line (Figs, 1, 4); 2) presence of basal pronotal striae ( Figs. 1, 4 ); 3) presence of basal elytral stria ( Figs. 1, 4 ); 4) absence of sutural elytral stria ( Figs. 1, 4 ); 5) absence of transverse carina on elytral epipleuron at humeral angle; and 6) presence of distinct marginal bead on anterior clypeal margin ( Figs. 1, 4 ).

Etymology. The genus name is derived from the words bella, Latin for “pretty,” in recognition of the attractive coloration of the specimens and dessus, a common root for genera in the tribe.

Discussion. The combination of character states in this genus is not particularly similar to any other in Bidessini . Superficially, specimens are similar to some species of Neoclypeodytes Guignot , but that genus has a distinctive occipital line. In Biström’ s (1988) key, Belladessus keys to Uvarus Guignot , but members of that genus do not have the anterior clypeal margin modified as in Belladessus .

The presence of only females in the two type series representing more than 125 specimens is unique in Dytiscidae . About 30 specimens were dissected in search of a male, but none were found, and all the remaining specimens appear to be females externally (protarsi not expanded nor other visible dimorphisms). Females have a reproductive tract typical of Bidessini species, with a well-developed receptacle, spermatheca, and ductwork ( Figs. 3, 6 ), though in the numerous examinations made, none appeared to have sperm in the spermatheca. Presence of a well-developed female reproductive tract does not, by itself, disprove that the species is parthenogenetic (it may simply be a retained attribute), but there appears to be good circumstantial evidence that this species has only females.

The only other species of Dytiscidae thought to possibly be parthenogenetic are in Hydrodytes ( Miller 2002) . However, although only females are known in two species in this group, relatively fewer specimens exist in collections, and there are no series of specimens nearly as long as for Belladessus . There remains some possibility, therefore, that male Hydrodytes simply have not yet been found. Hydrodytes also have well-developed reproductive tracts ( Miller 2001, 2002).

Belladessus also exhibits an interesting biogeographic disjunction: it is known from the Venezuelan Andes and from the central/eastern region of the Guiana Shield. The same pattern was recently observed for the water scavenger beetle genus Guyanobius Spangler (Gustafson and Short 2010) , which also shares a similar ecology: small forested streams and stream pools. While it may seem tempting to claim this is an artifact of collection bias, the region has been subjected to intensive collection efforts for aquatic beetles in the last decade. We have examined more than 100,000 water beetle specimens from northern South America. While we presume the distribution of the genus is certainly more widespread than is currently known, this general biogeographic pattern seems likely to hold and warrants further study.

Figures

Figs. 1–6. Belladessus species morphology. 1–3) B. femineus: 1) Habitus; 2) Left metacoxa, metatrochanter, and metafemur; 3) Female reproductive tract, ventral aspect. 4–6) B. puella: 4) Habitus; 5) Left metacoxa, metatrochanter, and metafemur; 6) Female reproductive tract, ventral aspect. Scale bar = 1 mm for Figs. 1 and 4.

Fig. 7. Distribution of Belladessus species.

Fig. 8. Habitats of Belladessus species. A) Type locality for B. femineus, collecting event SR13-0819-05B, on the summit of Tafelberg Tepui, Suriname, B) Type locality for B. puella, collecting event VZ12-0124-02B, ca. 13 NW Baranitas, Venezuela.