Hydroscapha saboureaui Paulian, 1949

Perkins, Philip D. & Bergsten, Johannes, 2019, New Myxophagan water beetles from Madagascar (Coleoptera: Torridincolidae, Hydroscaphidae), Zootaxa 4657 (1), pp. 57-96 : 81-85

Hydroscapha saboureaui Paulian

Figs. 25 (habitus), 27 (aedeagus), 29, 31 (terminal abdominal segments), 39 (map)

Hydroscapha saboureaui Paulian, 1949: 371 .

Type Material. Holotype (male): Labels ( Fig. 25 ): “ S. Ankavandra sables VII 49 R P// Hydroscapha saboureaui n.sp. Type// MNHN EC 7800 ” ( MNHN). Type locality notes in original description: “ 60 km. au sud d/Ankavandra, sur la piste de Miandrivazo, dans une mare tres superficielle formee par suintement sur le sable; l/eau, surchauffee, cache par un dense tapis d’algues colle au sable.”

Differential diagnosis. Habitus as in Fig. 25 (imaged pre-dissection). Slightly smaller in size than H. andringitra (length to elytral apices ca. 0.79 vs. 0.82 mm), but with a larger aedeagus, which has a much larger internal sac ( Figs. 27, 28 ). The total body length, including the telescoping terminal abdominal segments is slightly greater in H. saboureaui (ca. 1.14 vs. 0.99 mm). The two species also have distinctive differences in the terminal abdominal segments of males (see comparative notes following) and in females ( Figs. 29–33 ).

Description (holotype male): Size (mm): length to elytral apices 0.79, total length 1.14 (variable due to telescoping last abdominal segments), width 0.51. Color brown, with legs, palpi and antennae lighter, testaceous in parts.

Habitus as illustrated ( Fig. 25 ). Aedeagus and terminal abdominal segments as illustrated ( Figs. 27 , 29, 31 ). Dorsum very finely sparsely punctate and with very indistinct short sparse setae. Body shape and configuration of ventral morphology typical for genus (material for making slide mounts unavailable).

Comparative notes: The aedeagi of the two Malagasy species differ most notably in the size of the internal sac (= endophallus), which in H. saboureaui is at least twice as large as the sac of H. andringitra . In addition, the shape of the aedeagal apex differs slightly in the two species, with H. saboureaui being slightly wider at the area of the distal extreme of the internal sac ( Figs. 27, 28 ).

The following differences are seen in the abdominal sclerites of males of the two species:

Ventrite VI: In H. saboureaui the apical notch is shallower and the ventrite has lateral setae; in H. andringitra the notch occupies more of the ventrite, and lateral setae are lacking.

Tergite IX: In H. saboureaui the apical indentation is slightly narrower, setae are restricted to the apical area, behind which the cuticle is microreticulate and does not have setae. In H. andringitra the apical indentation is wider, the setae at the apex are slightly longer, and the area posterior to the apex has setae and is not microreticulate.

Ventrite VII: This is the most curious of the differences. In H. andringitra ventrite VII is truncate apically, and lacks the distinctive two clusters of long setae seen in other species of Hydroscapha . The apical margin is sclerotized, not membranous, indicating that the apical portion was not accidentally removed during dissection. Also, the habitus images ( Fig. 26 ), which were taken pre-dissection, show that the setal clusters of ventrite VII are not present. Additional specimens are needed to confirm that this is the actual condition, or if it is a deformity.

Tergite VIII: The tergite has a shorter broader shape in H. saboureaui and with basal corners rounded ( Fig. 29 ). In H. andringitra the shape is more elongate and lateral sides are sinuate before acuminate basal corners ( Fig. 30 ).

In females, the shapes of the terminal abdominal segments differ in the two species ( Figs. 31, 32 ).

The first three abdominal ventrites of the H. saboureaui holotype appear to be longer than those of the H. andringitra holotype ( Figs. 25 , 26 ). However, this might be due to some telescoping of segments in the later species. More specimens are needed to make reliable comparisons.

Historical perspective. Over time, various numberings and designations have been used for the terminal abdominal segments of Hydroscaphidae (see below). In many species of the genus, including the two Malagasy species, the penultimate ventrite is deeply notched ( Figs. 29, 30 ); herein, this is considered to be ventrite VI (= sternite VIII). The segment considered ventrite VII ( Figs. 29, 30 ) is held within the cavity formed by sternite VIII (= ventrite VI)) and tergite VIII.

Reichardt & Hinton (1976), in a comprehensive paper, elected to use the anatomical, non-homologous, terms “last visible sternite” (= ventrite VI), and “invaginated sternite” (= ventrite VII) for the male ventral terminal segments. Also, in reference to the terminal abdominal structures of females, they stated that, “We have not attempted to homologize any of these structures with the parts of the genitalia in other beetles.”

Löbl (1994) labeled the deeply notched male ventrite of two species as “sternite V” (his figure 12) for one species and “sternite VI ” (his figure 18) for the other species. Löbl referred to the last male segments as “segment génital.”

Fikáček and Šípková (2009) considered these segments to be “sternite VI ” (the deeply notched ventral segment) and “sternite VII ”, respectively.

In two more recently published papers, Hall and Short (2010) and Short et al. (2015) the sixth visible ventral abdominal segment is treated as sternite VIII. These differences are due to anatomical numbering (= ventrite VI) versus morphological numbering (= sternite VIII).

Figures

FIGURE 25. Hydroscapha saboureaui, habitus and labels of holotype.

FIGURES 26. Hydroscapha andringitra, habitus of holotype.

FIGURES 27–28. (27) Hydroscapha saboureaui, male genitalia of holotype, lateral view; (28) Hydroscapha andringitra, male genitalia of holotype, dorsal and lateral views.

FIGURES 29–33. (29–30) Hydroscapha males, ventrites and tergites. (29) H. saboureaui, holotype; (30) H. andringitra, holotype. (31– 33) Hydroscapha females, terminal abdominal segments. (31) H. saboureaui, last abdominal segments, right side, dorsal aspect (from Paulian 1949); (32) H. andringitra, last abdominal segments, right side, dorsal aspect; (33) H. andringitra, last visible ventrite.