Georissus (Neogeorissus) maritimus, Fikáček & Delgado & Gentili, 2012

Fikáček, Martin, Delgado, Juan A. & Gentili, Elio, 2012, The Hydrophiloid beetles of Socotra Island (Coleoptera: Georissidae, Hydrophilidae), Acta Entomologica Musei Nationalis Pragae 52, pp. 107-130 : 109-112

Georissus (Neogeorissus) maritimus sp. nov.

( Figs. 1–7 , 15–16, 19–20 )

Type locality. Yemen, Socotra Island, ca. 3 km NE of Shuab, 12°34.1′N 53°23.9′E, 3 m a.s.l.

Type material. HOLOTYPE: J ( NMPC): ‘ YEMEN: Socotra island / ca. 3 km NE of Shuab / mangrove, Avicennia marina / 12°34.1′N 53°23.9′E; 3 m a.s.l. / saline, 20-21.vi.2012 // Socotra Expedition 2012 / J. Bezděk, J. Hájek, V. Hula, / P. Kment, I. Malenovský, / J. Niedobová & L. Purchart leg. ’. PARATYPES: 4 JJ, 1 ♀, 41 spec. ( BMNH, IRSNB, NHMW, NMPC, KSEM, 5 spec. in DNA grade kept in NMPC): same label data as the holotype.

Description. Body narrowly elongate, weakly convex in lateral view. Body length 1.20– 1.60 mm (holotype 1.40 mm), width of head 0.30–0.40 mm (holotype 0.35 mm), maximum width of pronotum 0.45–0.60 mm (holotype 0.55 mm), maximum width of elytra 0.65–0.85 mm (holotype 0.75 mm). Coloration of elytra brown to piceous, pronotum dark brown with paler anterior portion, head piceous to black.

Head ( Fig. 2 ). Clypeus weakly convex, with few weakly developed granules anteromedially, anterior margin with elevated bead without distinct granules; each side of clypeus with deep pit anterolaterally; lateral portion of clypeus posteriorly divided from mesal portion by high ridge without granules, ridges bent laterad and bearing more or less distinct granules more anteriorly. Frons elevated above clypeus, bearing large elongate rhomboid plate mesally reaching to posterior part of frons; laterally of mesal plate with high and wide ridge on each side; posterior part of median rhomboid and longitudinal ridges connected by group or large and low granules posteriorly; frons with two pairs of deep pits, one situated anteromesally, second laterally. Clypeus and median portion of frons with weak mesh-like microsculpture. Antennal club with three antennomeres.

Prothorax ( Figs. 3–4 ). Pronotum 1.15× as wide as long, with maximum width at midlength; lateral portions rounded, without distinct projections. Median portion with two closely situated submedian ridges throughout, delimiting shallow median groove; each lateral lobe divided from mesal portion by longitudinal ridge falling into separate granules posteriorly. Anterior half of pronotum without granules, only bearing small pits intermixed with sparsely arranged punctures. Posterior half of pronotum without distinct bulges, with sparsely arranged large but low granules throughout the surface. Pronotum with two pairs of deep pits, one anteriorly and the other posteriorly of lateral lobe. Whole surface between granules with weak meashlike microsculpture. Ventral portion of prothorax with extremelly large antennal grooves, otherwise corresponding with G. crenulatus (Rossi, 1794) .

Mesothorax. Elytra ( Figs. 1, 5 ) combined 1.25× as long as wide, 1.75× as long as pronotum; base of elytra ca. as wide as maximum width of pronotum, maximum width of elytra in anterior third, then weakly narrowing posteriad to posterior fifth, apex strongly narrowed. Elytra completely devoid of granules, interstices without microsculpture. Elytral suture and intervals 1–7 evently convex, interval 8 reduced, interval 9 slightly elevated; lateral portion with suboval depression at anterior third across intervals 8–9; all intervals more convex posteriorly than anteriorly. Elytral series 1–11 regular, serial punctures small but sharply impressed. Lateral-most portion of elytron declined, hence elytra laterally without clear projections. Median pentagonal protuberance of mesoventrite flat, with distinct pits.

Metathorax. Metaventrite ca. 1.2× as long as mesoventrite, flat, with few scattered indistinct granules along posterior margin and four deep pits along anterior margin; lateral portions divided from mesal part by longitudinal ridges. Metathoracic wings absent in specimens examined for this character (n=5).

Abdomen ( Fig. 6 ) gradually narrowing posteriad. Ventrite 1 flat mesally, with lateral portion declines and divided by ridge; median portion with sparsely arranged punctures, without granules; posterior margin of ventrite 1 with pair of large tubercles facing enlarged granules of ventrite 2. Ventrites 3–4 with weakly developed granules along anterior margin.

Male genitalia ( Fig. 7 ). Aedeagus 0.35–0.45 mm long. Parameres 1.6× as long as phallobase, their combined width narrower than maximum width of phallobase; parameres nearly parallel-sided throughout except subbasally, subbasally slightly constricted; apex rounded at outer margin, bluntly pointed mesally; apex with numerous large pores, ventral portion of paramere with numerous sparsely arranged micropores. Median lobe 0.70× length of parameres, narrowly triangular apically, apex sharp, gonopore situated subapically, struts ca. 0.25× as long as apical portion of median lobe. Phallobase widening posteriad, without large posterior opening.

Differential diagnosis. Based on the evenly convex elytral intervals, Georissus maritimus sp. nov. may be easily diagnosed from the species of the G. costatus and G. caelatus species groups sensu DELÈVE (1967a,b). It may be easily distinguished from the majority of the species with equally elevated elytral intervals by the absence of a median rhomboid impression on the pronotum, which it shares with the African species G. sordidus Grouvelle, 1915 and G. bicolor Grouvelle, 1909 . The latter two species may be however immediately distinguished from G. maritimus sp. nov. by much larger and wider pale-coloured body, morphology of male genitalia and the sculpture of the abdomen (see DELÈVE 1967a), as well as by the sculpture of the pronotum which lacks any bulges in the posterior half in G. maritimus sp. nov. In fact, Georissus maritimus sp. nov. seems to be unique among all described species of the genus by its pronotal sculpture, i.e. the combination of the absence of a median rhomboid depression, absence of granules in anterior half of the pronotum and absence of elevated granulate bulges posteriorly. By the extremely long and narrow parameres and posteriorly widening phallobase, The new species resembles G. alticosta Grouvelle, 1909 (which has costate even elytral intervals), G. alluaudi Delève, 1967 (which has the pronotum with a rhomboid central depression), G. acutecostatus Fairmaire, 1898 and G. biroi Delève, 1969 (both with costate even elytral intervals).

Etymology. The species name refers to the type locality of this species, which is on the bank of a brackish lagoon situated at the estuary of a temporary stream to the Arabian Sea.

Collection circumstances. The type series was collected at night on a sandbar between the sea and a brackish lake in an estuary of a temporary stream ( Figs. 19–20 ). The specimens were collected on places without vegetation which were wet due to the seepage of the subsurface water. The surrounding vegetation (which usually began within ca. 2 meters of the sites with Georissus maritimus sp. nov.) consisted of the low succulent shrubs of Arthrocnemum macrostachyum (Moric.) Moris (Amaranthaceae) , Limonium socotranum (Vierh.) Radcl. -Sm. ( Plumbaginaceae ) and isolated groups of mangrove trees Avicennia marina (Forssk.) Vierh. (Avicenniaceae) . No specimen of Georissus maritimus sp. nov. bore the substrate layer on the body dorsum.

Distribution. Known only from the type locality.

Note. The unique morphology of G. maritimus sp. nov. makes it impossible to assign this species to any of the species groups proposed by DELÈVE (1967a,b) and it seems to be rather isolated from the known species of the genus. Further studies are thus necessary to understand the geographic origin of the species.

Figures

Figs. 1–6. Georissus maritimus sp. nov. (paratypes). 1 – pronotum and elytra in dorsal view; 2 – head, dorsal view; 3–4 – detail of pronotum (3 – dorsal view; 4 – dorsolateral view); 5 – elytron, dorsolateral view; 6 – abdomen.

Figs. 7–8. Genitalia of Socotran endemic Georissus species. 7 – G. maritimus sp. nov. (a, b: two different ventral views of the same aedeagus; c: lateral view); 8 – G. nemo sp. nov., ventral view.

Figs. 15–22.Socotran endemic Georissus species and their habitats. 15–16 – G. maritimus sp. nov.(15 – dorsal view; 16 – lateral view). 17–18 – G. nemo sp. nov. (17 – dorsal view; 18 – lateral view). 19–20 – the sand tongue 3 km NE of Shuab, type locality of G. maritimus sp. nov. (19 – general view of the habitat; 20 – satellite view showing the position of the locality); 21–22 – the stream at Arhar, type locality of G. nemo sp. nov. (21 – general view of the habitat; 22 – satellite view showing the position of the locality).