Canthysellus Baca and Toledo

Baca, Stephen M. & Toledo, Mario, 2015, CanthysellusBaca and Toledo (Coleoptera: Noteridae: Noterini), a New Genus of Burrowing Water Beetle from South America, The Coleopterists Bulletin 69 (3), pp. 477-488 : 479-480

Canthysellus Baca and Toledo , new genus

Type Species. Noterus buqueti Laporte, 1834 , here designated.

Diagnosis. Canthysellus is distinguished from other genera of Noterini by the following combination of characters: (1) prosternal process broad ( Figs. 4, 5 ); (2) prosternal disc with a short, closely-spaced, linear series of stout setae anterior to procoxal cavities ( Figs. 4a, b, 5a ); (3) lateral bead of pronotum distinct, broad; (4) posterior metatibial spur serrate ( Fig. 6b ).

Comparative Diagnosis. In certain ways, Canthysellus is very similar to the genera Canthydrus Sharp and Suphisellus Crotch. Canthysellus superficially resembles many members of Canthydrus in body shape, however, the serrate posterior metatibial spur and isolated tuft of setae on the prosternum distinguishes Canthysellus from Canthydrus . Canthysellus shares more diagnostic characters with Suphisellus , including the distinct linear series of stiff setae on the prosternum and a serrate posterior metatibial spur. However, Canthysellus lacks the key synapomorphy of Suphisellus , i.e., the lateral crease, or interrupted bead, subtending the lateral margins of the pronotum. Following Miller’ s (2009) survey of female genitalia, the female genitalia of Canthysellus , with long laterotergites, non-dentate gonacoxae, and pointed gonacoxasternites, are similar to that of both Suphisellus and Canthydrus . However, the laterotergites of Canthysellus are much more slender and each gonacoxasternite is with only one elongate apodeme rather than two, similar to the genitalia of the genus Suphis Aubé. Canthysellus does not otherwise share many diagnostic characters with Suphis , and in comparison these are clearly distinct genera (see Miller 2009). Note: Miller (2009) mistakenly diagnoses Canthysellus (as Liocanthydrus ) as having a nonserrate [posterior] metatibial spur, but an examination of his character matrix shows that this spur was correctly coded as serrate in the phylogenetic analysis.

Description. Medium sized beetles, TL = 2.65– 3.50 mm; body form convex, robust, broadly attenuate posteriorly. Color and appearance: Shiny, elytra superficially iridescent. Color of head and pronotum ranging from yellow to reddish brown; color of elytra dark reddish brown to nearly black, with elytral maculae appearing as interrupted transverse bands or spots, color similar to head and pronotum, but often slightly lighter. Color of venter yellowish brown to reddish brown with noterid platform and sutures darkened. Head: Eyes well-developed. Antennae with 11 antennomeres, length ca. 0.75X head width, antennomeres XII–X expanded, subserrate, each with sensory field extending ca. half length of antennomere to anterodistal angle; antennomere XI length ca. 1.5X length of antennomere X, attenuate, with sensory field extending ca. midlength to apex. Apical maxillary palpomeres nearly fusiform, with apices slightly bifid and with small sensory field. Microsculpture fine, consisting of small isodiametric cells and evenly spaced micropunctures. Thorax: Pronotum glabrous, anterior margin subtended by series of punctures producing sparse, slender setae; lateral margins and pronotal bead with sparse setose punctation. Lateral pronotal bead broad, ceasing at anterolateral angles, attenuate posteriorly. Elytra glabrous, with series of fine punctures extending laterally at elytral base and 3 longitudinal series of fine, sporadic punctures, 1 medial, 1 discal, and 1 lateral submarginal; medial series more distinct than others; punctures more sporadic in distal half of elytra, many punctures bearing very fine setae of varying length, especially along lateral margins and in distal half of elytra; elytra and pronotum with fine reticulate microsculpture. Prosternum narrow, glabrous, with tuft of short, longitudinal series of stiff setae on prosternal disc, anterior to procoxae and prosternal process ( Figs. 4, 5 ). Prosternal process broad, triangular, narrow between procoxae, broad posteriorly, with lateral margins bordered by bead; posterior margin subtruncate, sinuate. Posterior lobes of noterid platform extending posteriorly just beyond 1 st visible abdominal ventrite (ventrite II); lobes rounded at apex, bearing small, transverse line of stout setae; surface of noterid platform and prosternal process setose, setae produced from punctures ( Figs. 4, 5 ). Protibia with very large spur, strongly curved posteriorly; with fringe of stout setae arising along lateral margin, reduced and discontinuous at apex. Metafemur with series of closely spaced setae on distal third of anteroventral margin, ceasing at anteroapical angle ( Figs. 6, 7 ). Posterior metatibial spur serrate. Abdomen: Ventral surface glabrous, with nearly indistinct microsculpture consisting of slender, laterally elongate cells; ventrites III and IV fused, suture indistinct; ventrites IV–VI with sparse, slender setae on lateral margins; ventrites V and VI with sparse line of setae extending medially from lateral margin, line discontinuous, not reaching median. Ventrite VII with several long, slender setae near apex. Pygidium modified with very small spur at apex; spur fused, not articulate. Males: Protarsomeres I–III weakly dilated, with 3–4 distinct adhesive discs, protarsomeres IV and V slender. Mesotarsomeres I and II weakly dilated with 3 adhesive discs, mesotarsomeres III–V slen- der. Ventral sclerite of genital capsule bifurcate, lacking setae or setae indistinct at apices. Aedeagus asymmetrical; median lobe dorsally curved, divided ventrally by large groove, left side broad in lateral aspect, composing the greater part of the aedeagus, groove ceasing and sides meeting at or before apex; left lateral lobe broad, attenuate to rounded or weakly lobed apex, with dense tuft of setae produced subapically on inner surface; right lateral lobe broad, subtriangular, but with ventral margin broadly rounded. Females: Pro- and mesotarsi not dilated, slender and without adhesive discs. Female genitalia as in Fig. 11 ; laterotergites very long, slender; gonacoxae short, not dentate; gonocoxosternites broad, apically pointed, with a single anterior apodeme.

Biology. Members of Canthysellus can be found in a variety of aquatic habitats, including the vegetated margins of forested ponds, detrital pools, streams, and morichales. Fig. 13 depicts two sites in which members of Canthysellus were collected.

Distribution. Canthysellus is restricted to the NeotropicsandisknowntooccurinBrazil (Amazonas), French Guiana, Guyana, Peru, Suriname, and Venezuela ( Fig. 12 ).

Classification. Following Miller (2009), though under the mistaken identity of Liocanthydrus (see Gomez et al 2013; Baca et al 2014), Canthysellus is treated as a member of Noterini , a tribe most distinctly characterized by the large spur and setal fringe of the protibia (the latter secondarily lost in Suphis ). As was mentioned earlier, this genus is very similar to the genera Canthydrus and Suphisellus . The morphological analysis conducted by Miller (2009) placed Canthysellus (as Liocanthydrus ) as sister to Suphisellus in a monophyletic group comprised of Suphis , [ Canthysellus ], and Suphisellus , though with relatively low support. Given the similarity, we presume that Canthysellus is closely related to the genera Suphisellus , Suphis , and Canthydrus , however, further phylogenetic analysis is needed to confidently infer relationships among these genera.

Figures

Figs. 4–5. Canthysellus species, pro- and metasterna and metacoxae (noterid platform) with studies of prosternal setae. 4) C. buqueti, male, a and b = variation of prosternal setae; 5) C. peruanus, paratype, male, a = enlarged view of prosternal setae. Scale bar = 0.5 mm.

Figs. 6–7. Canthysellus species,hind legs.6) C.buqueti, male, a = setae of inner margin of metatibia, b = posterior metatibial spur, serration is diagnostic of the genus; 7) C. peruanus, paratype, male, a = setae of inner margin of metatibia. Scale bars = 0.25 mm

Fig. 11. Canthysellus buqueti, female genitalia. Scale bar = 0.25 mm.

Fig. 13. Habitats of Canthysellus species. a) Type locality of C. sipaliwini, Suriname: Sipaliwini District, stream near the Kutari River, collecting event SR13-0816-02A, b) Example habitat of C. buqueti; Suriname: Sipaliwini District, summit of Tafelberg Tepui, collecting event SR13-0816-02A.

Fig. 12. Distribution map of Canthysellus species.