Laccophilus rakouthae, Manuel & Ramahandrison, 2020

Manuel, Michaël & Ramahandrison, Andriamirado T., 2020, Four new species of the diving beetle genus Laccophilus Leach, 1815 from Madagascar (Coleoptera, Dytiscidae, Laccophilini), Zootaxa 4822 (4), pp. 482-502 : 494-499

Laccophilus rakouthae sp. nov.

Figures 31, 33 , 35, 36, 39, 40 .

Type locality. Madagascar, former province of Antananarivo, Ankaratra massif, ca. 1.7 km North-West of Manjakatompo, GPS coordinates S19°22’ E47°19’, altitude 1,700 m .

Type material. Holotype (♂): ” Madagascar. Ex-prov. / Antananarivo. ca. 1.7 km NW / Manjakatompo. 04 VII 2018 / Ramahandrison leg. // S19°22’ E47°19’. Alt. 1,700m. / Large pond full of helophytes / (étang des Tilapia) ( MANS1 ) / Ankaratra massif” [pr], ” Holotype, Laccophilus rakouthae sp. nov., Manuel & Ramahandrison 2020” [red, pr] ( MNHN) . Paratypes ( CMM, NMPC) : 3♂♂, 2♀♀, “ Madagascar. Ex-Prov. / Antananarivo. Manjakatompo / 13 VII 2018 / Ramahandrison leg. // S19°22’ E47°20’ / Alt. 1,600m. Small uncultivated / rice paddy field ( MANS2 ). / Ankaratra massif”. All paratypes with the respective printed red label .

Description of holotype. Habitus ( Fig. 31 ) oval, with lateral sides widely rounded, posteriorly progressively tapered to rather broadly rounded apex; lateral outline continuous between pronotum and elytra; maximum body width at about 40% of total body length and about 30% of elytral length; dorsal surface evenly and rather strongly convex; in lateral view maximum height about halfway between first third and half of total length.

Colouration. Dorsal surface of head rufo-testaceous. Pronotum rufo-testaceous, broadly darkened in middle along anterior and posterior margins. Elytron dark brown with well-delimited testaceous transverse subbasal band ( Fig. 31 ), extending from lateral margin to shortly before suture, its anterior outline moderately and posterior outline strongly sinuous; along lateral margin with well-delimited testaceous area (continuous with subbasal band), its inner outline irregular, towards midlength of body extending farther from lateral margin; sublaterally in posterior half with few isolated small pale spots; apical region paler and with rather well-defined subapical yellow spot. Ventral surface entirely rufo-testaceous, except abdominal ventrites II–VI progressively darker ( Fig. 33 ). Antennae with antennomeres I–VIII testaceous and antennomeres IX–XI brown; maxillary palps testaceous with apex of apical palpomere brown; labial palps entirely testaceous. Anterior and median legs testaceous; posterior legs rufo-testaceous.

Head. Anterior outline of clypeus widely rounded. Surface shiny, with double reticulation; large meshes irregular and of variable sizes, rather indistinct, more weakly impressed than small meshes; with sparse micropunctures; larger punctures present along inner eye margins and in two irregular transverse rows sub-laterally on frons.

Pronotum. Lateral margins evenly and very weakly arcuate. Surface shiny, with double reticulation; large meshes irregular and of variable size, more conspicuous than on head; small meshes rounded, more weakly impressed than on head; punctation inconspicous except along anterior and lateral margins with sparse, moderately large and weakly impressed punctures.

Elytron. Surface shiny, with double reticulation; large meshes in discal region weakly impressed but distinct, in scutellar region more strongly impressed, in posterior third indistinct; small meshes irregularly polygonal, of rather homogeneous sizes, larger and more strongly impressed than on pronotum; punctation inconspicuous beyond rather indistinct discal puncture row.

Ventral surface. Prosternal process narrowly lanceolate, strongly convex, with apex acutely pointed. Metacoxal lines anteriorly subparallel. Apical abdominal ventrite strongly convex, in posterior two thirds almost tectiform; sublaterally close to anterior margin, on right side with oblique carina and on left side with distinct protuberance; posterior margin widely emarginated, medially with apex slightly produced. Entire ventral surface very shiny; on metaventrite, metacoxal apophysis and abdominal ventrites with very fine regular microstriae; on elytral epipleura with obsolete polygonal reticulation; on metacoxal plate with well-impressed reticulation, meshes longitudinally elongated; on abdominal ventrites with oblique striae, denser on ventrites I–III; surface impunctate except on antero-medial prosternal region, anterior region of metaventrite and apical abdominal ventrite with rather small shallow punctures. Inner region of metacoxal plate with semi-circular stridulation apparatus consisting of about forty fine parallel striae.

Legs. Pro- and mesotarsi slightly broadened, with four transverse rows of small adhesive setae.

Aedeagus. Median lobe in lateral view as in Fig. 35 , in ventral view as in Fig. 36 ; parameres as in Figs. 39– 40 .

Females. Pro- and mesotarsi not broadened, without ventral adhesive setae.

Variability. The elytral colour pattern varies with respect to width of the transverse subbasal pale band, degree of extension of the lateral pale area, and number and sizes of small pale spots in the posterior third and the apical region.

Measurements. Holotype: TL = 3.6 mm, TL without head = 3.4 mm, MW = 2.0 mm, ratio TL/MW = 1.77. Paratypes: TL = 3.6–3.8 mm (3.66±0.08), TL without head = 3.35–3.5 mm (3.41±0.05), MW = 2.0– 2.05 mm (2.03±0.03), TL/MW = 1.78–1.85 (1.81±0.03).

Differential diagnosis. This species is very similar to L. transversovittatus , notably in terms of dorsal colour pattern ( Figs. 31 and 32 ), colouration and structures of the ventral surface ( Figs. 33 and 34 ), including aspect of the male stridulatory file, and shape of the left paramere ( Figs. 39 and 41 ). It differs from L. transversovittatus by larger size ( L. transversovittatus : specimens examined in this study, TL = 3.10–3.50 mm; Biström et al. 2015: TL = 3.2–3.5 mm), broader habitus (compare Fig. 31 and Fig. 32 ), and distinctly different shapes of the right paramere (compare Fig. 40 and Fig. 42 ) and of the median lobe of aedeagus (compare Figs. 35–36 and Figs. 37–38 ). The median lobe in lateral view is much straighter than in L. transversovittatus , looking like the median lobe of the African species L. occidentalis (see Fig. 375 in Biström et al. 2015). L. rakouthae differs from L. occidentalis by larger size (total length of L. occidentalis 2.8–3.3 mm according to Biström et al. 2015), broader habitus, and median lobe in lateral view with the dorsal outline slightly more strongly curved and the dorso-apical protuberance more distinct.

Habitat. This species was collected at only two sites, with altitudes respectively of 1,630 m and 1,720 m, in an area (Manjakatompo Ankaratra natural resources reserve) that has been intensively explored by us and others. We can reasonably state that it is locally very rare and/or ecologically specialised. However, quite amazingly, both sampling sites are located in the most degraded part of the massif (degraded secondary forest for one site; agricultural landscape for the other site). Both are eutrophic densely vegetated lentic water bodies, strongly impacted by human activities (notably fish farming and frequentation by zebus), with clear water, a clay bottom and moderate abundance of decaying vegetal material. One of the sites (Étang des Tilapia, Figs. 51, 52 ) is a large pond with a dense and extended belt of helophytes and abundant submerged aquatic vegetation, whereas the other site ( Fig. 50 ) is a smaller artificial pond among rice fields close to the township of Manjakatompo, with lesser development of helophytes and aquatic plants. We strongly suspect that these two sites, in which we sampled only a few specimens of L. rakouthae sp. nov., do not reflect the true habitat preferences of this species, which possibly may instead be a species associated with streams (as is usually the case for L. transversovittatus ). More field work in this area is clearly needed to better understand the ecology of L. rakouthae .

Distribution. So far known only from Manjakatompo in the Ankaratra massif, central Madagascar ( Fig. 53 ).

Derivatio nominis. This species is dedicated to Prof. Bakolimalala Rakouth (Département de Biologie et Ecologie végétales, Université d’Antananarivo). The species name is a noun in the genitive singular.

Figures

FIGURE 53. Map showing the distribution of known localities of the newly described species. Red dot: L. leguyaderi; Blue dots: L. bergsteni; Magenta dot: L. bergsteni and L. rakouthae; yellow dot: L. makay. Names of corresponding protected areas or massifs indicated in italics above dots.

FIGURES 31–34. Habitus (31, 32) and ventral surface (33, 34) of: (31, 33) Laccophilus rakouthae sp. nov. (31, holotype; 33: male paratype); (32, 34) Laccophilus transversovittatus (male specimens from Isalo massif). Scale bar: 1 mm.

FIGURES 35–42. Median lobe of aedeagus in lateral (35, 37) and ventral (36, 38) view and left (39, 41) and right (40, 42) parameres of: (35, 36, 39, 40) Laccophilus rakouthae sp. nov. (holotype); (37, 38, 41, 42) Laccophilus transversovittatus (specimen from Isalo massif). Scale bar: 0.1 mm.

FIGURES 47–52. Habitats of Laccophilus makay sp. nov. (47–49) and Laccophilus rakouthae sp. nov. (50–52). (47) Spring on sandy bank of river Andranomanitsy (Makay massif, 500 m); (48) Large pool with clear water, sandy bottom and masses of tree roots (Makay massif, 550 m). (49) Shadowed pool with sandy bottom and lots of orange deposit, beneath rock wall in a canyon (Makay massif, 540 m; type locality of L. makay); (50) Small uncultivated rice paddy field, in agricultural landscape (Ankaratra massif, Manjakatompo, 1,650 m); (51) Large eutrophic pond full of helophytes, surrounded by degraded forest (Ankaratra massif, Manjakatompo, Étang des Tilapia, 1,700 m; type locality of L. rakouthae); (52) Close-up view of the margin of the same pond.