Adelphydraena amazonica Perkins & Ribera, 2020

Benetti, Cesar J., Valladares, Luis F., Delgado, Juan A. & Hamada, Neusa, 2021, Morphological remarks on Adelphydraena amazonica Perkins & Ribera, 2020 and new records of two other Hydraenidae from Brazil (Coleoptera), Zootaxa 4966 (1), pp. 61-68 : 62-65

Adelphydraena amazonica Perkins & Ribera, 2020

Figs 1 (male habitus), 2 (aedeagus and male sternite X), 3 (female genitalia), 4 (habitat), 5 (map)

Adelphydraena amazonica Perkins & Ribera, 2020: 36

Studied material. Brazil: Amazonas State , Manaus County, Reserva Florestal Ducke , Igarapé [stream] Acará, (02°57’07’’S, 059°57’27’’W), 08–09.vi.2018, leg. A.E.Z. Short (2 males and 1 female, INPA).

Male description. Habitus as in Fig 1 . Size (in mm, n= 2): BL: 1.40–1.45/0.75–0.80; head width: 0.42–0.43; pronotum length/width: 0.40–0.42/0.61–0.62, pronotum width of the anterior/posterior margins: 0.49–0.50/0.44– 0.46; EL/EW: 0.84–0.88/0.75–0.80. Color: Dark brown, with head base, pronotal disc and elytra darker, antennae, maxillary palps and legs testaceous, with yellowish tarsomeres. Head: Frons finely sparsely punctate with short setae, medially smooth and shiny, laterally microreticulate. Clypeus finely punctate, punctures denser than in frons, bearing short setae in posterior half. Labrum slightly longer than clypeus, with a deep medial U-shaped emargination (7.5–8.0 x length of labrum), slightly opened towards the apex. Mentum subquadrangular, narrowed anteriorly, with anterior lateral margins pointed and slightly curved inward. Pronotum: Subcordiform. Anterior and posterior margins respectively trisinuate and bisinuate, lateral margin denticulate. Disc raised, with two evident shiny areas and a medial row of punctures forming a transverse deep depression. Anterior half with large, deep punctures, smaller than those of posterior half. Lateral areas densely and finely puncturated, areas between punctures shiny. Posterior half with two rows of large punctures, second row contacting with posterior margin of pronotum. PF1 deep, extending posteriorly and reaching PF2, PF3 wide, PF3 and PF4 weakly impressed. Elytra: Markedly convex. Each elytron with 9 rows of punctures, 6 between suture and humeral callus and with a short tenth row of small punctures located between anterior end of fourth and fifth rows. Lateral explanate margin serrate, with two marked spines in its anterior third, narrowing posteriorly and with a small, acute process before suture. Prosternum: Prosternal intercoxal process slightly wider than mesoventral intercoxal process (0.11/ 0.09 mm); prosternal midline length almost 2 x prosternal intercoxal width (0.19/ 0.11 mm). Mesoventrite: Mesosternal intercoxal process subquadrate; posterior margin convex. Metaventrite: Plaques narrow, not contacting and converging anteriorly. Legs: Femora globose, tibiae slightly widened distally. Abdomen: Distance separating coxal cavities approximately 1.2 x mesosternal intercoxal process width (0.12/ 0.09 mm). Ventrites 1-5 with long dense setae, ventrites 6-7 shiny, with sparsely pubescence. Aedeagus as Fig 2 : Parameres of similar shape, large and slender, shorter than main piece; apex of main piece in ventral view curved, hook-shaped, distal lobe globose and developed, similar to those other species in the genus, approximately two times longer than wide. Sternite X and spiculum gastrale as Fig. 2C . Sternite X oval, covered by scattered short setae on its distal half; spiculum gastrale long, tapering basally and distinctly separated from sternite by a short membrane.

Female remarks. The studied specimen is very similar in size (length 1.51 mm, width 0.84 mm) and color to holotype (see Perkins & Ribera 2020). Terminal abdominal segments and spermatheca: Terminal tergite ( Fig. 3a ) elliptical. Disc covered by short setae and with distal margin slightly emarginated. Last abdominal ventrite ( Fig. 3b ) with two plates. Ventral plate heart-shaped, without subapical tufts of setae. Dorsal plate slightly asymmetrical, surpassing the proximal rim of ventral plate and with two slightly impressed elliptical depressions. Spermatheca ( Figs 3c, d ) distinctly long, straight and distally capitate.

Sexual dimorphism. Male ( Fig.1 ) similar to female in external morphology (compare with Fig. 2 in Perkins & Ribera, 2020), but smaller (ca. 1.38-1.45 x 0.75-0.80 mm opposite to female ca. 1.50-1.51 x 0.83-0.84 mm) and with elytral margins slightly wider than in female. Tibiae without sexually dimorphic characters.

Taxonomic remarks. Adelphydraena amazonica has a characteristic chordate pronotum and a developed serrate elytral margin and thus, resembles A. surinamensis and A. spinosa . It also resembles A. spangleri , but this species is considerably bigger and lacks serrate elytral margins. Conversely, the male genitalia of A. amazonica and A. spangleri are similar, especially their main pieces. Based on morphological similarities these four species seem to be closely related, while the fifth known species, A. orchymonti , has a slightly diverging shape. This is congruent with the partial phylogenetic arrangement based on molecular data revealed in Perkins & Ribera (2020).

Distribution and habitat. Specimens were collected in the type-locality of the species, a shaded forest stream at “Ducke Forest Reserve”, nearby Manaus city, Amazonas, Brazil. This typical Amazonian stream is a permanent creek ( Fig. 4a ), which exhibits seasonal water level fluctuations. During the rainy season, the water table increases significantly, frequently overflowing the stream banks and creating lateral swamp pools. The three reported specimens were collected in a temporal lateral pool, close to the stream banks ( Fig. 4b ), filled stream water, leaf litter and exposed roots.

Figures

FIGURE 1. Male of Adelphydraena amazonica Perkins & Ribera. Dorsal (a), lateral (b) and ventral (c) habitus. Scale bar = 0.5 mm.

FIGURE 2. Male of Adelphydraena amazonica Perkins & Ribera, aedeagus in lateral (a) and ventral (b) view, sternite X and spiculum gastrale (c). Scale bars = 0.1 mm.

FIGURE 3. Female of Adelphydraena amazonica Perkins & Ribera, terminal tergite (a), last abdominal ventrite (b) and spermatheca (c, d). Scale bar = 0.1 mm.

FIGURE 4. Habitat of Adelphydraena amazonica Perkins & Ribera. Reserva Florestal Ducke, Manaus County, Amazonas State, Brazil. Igarapé Acará (a) and associated lateral swampy pool (b) where the specimens were collected.