Macrelmis rodrigoi, Almeida & Fernandes & Rini, 2020

Almeida, Maria Do Livramento Sampaio De, Fernandes, André Silva & Rini, Rafael Bold-, 2020, A new species of Macrelmis Motschulsky, 1859 (Coleoptera: Elmidae) and new records of Elmidae from Roraima State, northern Brazil, Zootaxa 4718 (2), pp. 277-284 : 278-281

Macrelmis rodrigoi sp. nov.

( Figs 2–6 )

Diagnosis. Body parallel-sided, robust. Pronotum wider than long, without gibbosities; median longitudinal impression well visible, extending from basal 1/4 to apical 1/4; sublateral carina extending from base to anterior margin; elytral base wider than pronotum; elytral apices together forming nearly flat to broadly rounded margin with small and shallow medial sulcus. Aedeagus with median lobe straight, in dorsal view, tapering from base to rounded apex, 1.5 times longer than the parameres; phallobasis shorter than median lobe

Description: Holotype: male. Length: 3.0 mm; maximum width 1.2 mm (across apical 1/4 of elytra); pronotal length 0.9 mm; pronotal width 1.0 mm; elytral length 2.1 mm. Body parallel-sided, robust.

Color ( Figs 2, 3 ): Cuticle dark brown, except for: antennae, tarsomeres, tarsal claws, mouth parts rufo-testaceus; golden tomentum and setae over the body.

Head: Covered with granules. Eyes rounded. Antenna 11-segmented, filiform, first, second and last segments elongate; last segment with subtriangular apex. Labrum subretangular, anterior angles rounded. Clypeus subrectangular, covered with fine, sparse golden setae. Maxillary palpus with last segment rounded and larger than remaining segments combined. Labial palpus with last segment rounded and larger than remaining segments combined.

Thorax ( Figs 2, 3 ): Pronotum slightly wider (1.0 mm at base, 0.7 mm on apex) than long (0.9 mm); granulated, with coarser granules near lateral margin; covered with short and sparse golden setae; median longitudinal impression well visible, shallow; lateral margin crenate; sublateral carinae narrow, strongly raised, extending along entire length; anterior angles sharp, projected. Hypomeron granulate. Elytra 2.1 mm long, 1.2 mm wide; intervals slightly convex near base; lateral margin crenate; humeral angle subquadrate; accessory stria 1/4 as long as elytra; apices together forming nearly flat to broadly rounded margin with small and shallow medial sulcus; epipleura with sparse fine granules. Scutellum convex at base, forming V-shape angle at apex. Prosternum granulate with anterior margin truncate; prosternal process longer than wide, extending beyond front coxae, lateral margins nearly straight, apex rounded; metaventrite wider than long, 1.7 times longer than mesoventrite, metaventrite with median groove extending from near posterior to near anterior margin. Legs slender; coxae granulate; tibiae granulate, with apical fringes of tomentum as follows: pro-tibiae with one outer fringe extending from apex to middle; meso-tibiae with two fringes, outer extending from apex to middle, inner on distal 1/4; meta-tibiae with one posterior fringe on distal 1/4.

Abdomen: ventrites granulate, more tomentose laterally, except of ventrite V; ventrites IV and V with posterior angles produced.

Genitalia ( Figs 4-6 ): Median lobe straight, in dorsal view, tapering from base to rounded apex, 1.5 times longer than the parameres; parameres slender, outer margin straight, inner margin gradually narrowing in apical 3/5 and straight in apical 1/3; phallobasis shorter than median lobe; in dorsal view nearly straight from apex to base, base diagonally excavated at right side; in lateral view, basal 2/5 nearly straight, apical 3/5 bent ventrally.

Female. Unknown.

Plastron: Present on entire surface of the body, except: antennae, mouthparts, tarsi and tarsal claws.

Intraspecific variation. The specimens examined showed no significant morphological variation.

Etymology. The specific epithet honors Rodrigo Lopes Borges, a friend and student of biology, who devoted himself to Elmidae during his undergraduate studies but passed away due to cancer.

Distribution. Roraima State, Brazil ( Fig. 1—P1 ).

Type series. Holotype: male, Brazil, Roraima State, Amajarí municipality, Igarapé Geladeira (P1) (03°47’02” N / 61°45’03” W), R. Boldrini , 18.XII.2014, aquatic sampling D net, litter submerged and rocks ( INPA) . Paratype: two males, same data as holotype ( UFRR) .

Taxonomical notes. Macrelmis rodrigoi sp. nov. is herein placed as a member of the amazonica species group Passos, Miranda & Nessimian 2015, along with Macrelmis amazonica ( Hinton, 1945) , Macrelmis terea ( Hinton, 1946) , Macrelmis thorpei ( Hinton, 1946) and Macrelmis tityra ( Hinton, 1946) for having aedeagus with rounded apex and significantly longer than parameres. However, in another excerpt of their paper, Passos, Miranda & Nessimian 2015 present a diagnostic table to distinguish Macrelmis species groups, where they stated a proportion of 1/3 for what we suppose should be the maximum expected size for the parameres in relation to the aedeagus. Therefore, based on the fact that Passos, Miranda & Nessimian 2015 erected the amazonica species group based on M. amazonica and also included M. thorpei as a member, both species pursuing parameres much longer than the referred 1/3 of the aedeagus, we assumed that the table presented on their work is wrong or misexplained. Even we would like to emphasize our concern about species group arrangement based on as few characteristics from a single structure as established by Passos, Miranda & Nessimian 2015 and that it is an artificial division, it is still useful for identifying species of larger elmid genera like Macrelmis . However, the groups should not be taken as taxonomic categories and may be avoided once natural grouping, based on thorough systematic revision, become available.

Regarding the species of the amazonica species group, the new species can be distinguished from M. amazonica by having paremeres slightly constricted pre-apically; from M. terea by having aedeagus narrower than broad, nearly of the length as basal lobe; from M. thorpei by having aedeagus in dorsal view without constriction and 1.5 times longer than parameres (dorsal view); and from M. tityra by having parameres longer, extending beyond midlength of main lobe. It differs from species of all other species groups by having penis with broadly rounded apex and 1.5 times longer than parameres, absence of any constriction in dorsal view or folded structures ventraly on aedeagus ( Figs 4, 5, 6 ). It also differs from the remaining species without assignment to any species groups, Macrelmis bispo Barbosa, Fernandes & Oliveira 2013 , Macrelmis elicioi Monte & Mascagni 2012 , Macrelmis germaini ( Grouvelle 1896) , Macrelmis immsi ( Hinton 1936) , Macrelmis saltensis Manzo 2003 and Macrelmis steineri Spangler 1980 by the size and shape of aedeagus, parameres and by lacking any remarkable feature like distinctive hair, setae or sponge like structures on the male genitalia.

Figures

FIGURE 1. Sampled sites where Elmidae species were collected in Roraima State, Brazil.

FIGURES 2–3. Habitus of Macrelmis rodrigoi sp. nov., male: 2) dorsal view; 3) ventral view.

FIGURES 4–6. Macrelmis rodrigoi sp. nov., male genitalia: 4) ventral view; 5) dorsal view; 6) lateral view.