Amplinus convexus ( Carl, 1902 )

Korotayeva, A. M. & Golovatch, S. I., 2025, A new record and the first meaningful iconography of the millipede, Amplinus convexus (Carl, 1902) from Costa Rica (Diplopoda: Polydesmida: Aphelidesmidae: Amplininae), Russian Entomological Journal 34 (1), pp. 136-139 : 138

Amplinus convexus ( Carl, 1902)

Figs 1–6 .

Pachyurus convexus Carl, 1902: 633 , plate 11, fig. 57.

Amplinus convexus — Pocock, 1909: 150 (D); Chamberlin, 1933: 18 (R); Hoffman, 1999: 369 (R, L).

Pseudamplinus convexus — Hoffman, 1954: 51 (L); Loomis, 1972: 200 (R).

MATERIAL. 2 ♂♂, 2 ♀♀ ( ZISP MYR _DIP_0000197 & MYR _DIP_0000200), Costa Rica, Heredia Prov., La Selva Biological Station , 10°25′58.9′′N, 84°00′24.4′′W, 20–26. VI .2023, D. V. Logunov leg.

DESCRIPTION. Length ca 62 mm or ca 69 mm, width on midbody pro- and metazona 7.0 and 12.0 mm, and 7 and 10 mm, respectively (♂), or length ca 65 mm and ca 62 mm, width on midbody pro- and metazona 9.0 and 8.9 mm, and 13.9 and 11.6 mm, respectively (♀).

General coloration light brown with contrasting brown prozona and vertex, yellowish paraterga, legs and antennae, and beige venter and epiproct ( Figs 1, 2 ). Smaller ♂ lighter, light brown with contrasting brownish to red-brown prozona. ♀♀ slightly darker than ♂♂.

Tegument shining, metaterga with weak polygonal areations, venter smooth and shining ( Fig. 1 ). Clypeolabral region and vertex bare, epicranial suture evident. Interantennal isthmus 1.2 times as broad as diameter of antennal socket. Antennae short, in situ not completely extending past ring 2 dorsally (♂), or shorter, extending only past 2/3 collum (♀). In length, antennomeres 4-6>3>2>1>7. Metazona below paraterga densely granulate to spinulate, increasingly strongly spinose, but poorly granulate towards telson ( Figs 3, 4 ).

In width, rings 4–15> 1=3> collum> head, trunk increasingly attenuated caudad on rings 16–20. Paraterga set at about ½ midbody height, well-developed, a little thicker and higher on pore-bearing rings than on poreless ones ( Figs 3, 4 ). Paraterga delimited by distinct sulci dorsally and faint sulci ventrally, all sulci being complete. Lateral calluses, or peritremata, and caudal corners of paraterga slightly more strongly developed in ♂ than in ♀. Anterior corners of paraterga invariably broadly rounded, caudal corners sharp in collum, always rounded thereafter, mostly not produced past rear tergal margin, only in rings 17–18 increasingly drawn past rear tergal margin. Ozopores lateral, invisible from above, lying at about half poriferous peritremata. Collum nearly entirely smooth, only laterally next to callus very faintly areolate. Following metaterga poorly, but visibly areolate, polygonal setigerous areations being arranged in three transverse rows across dorsum. Tergal and sternal setae fully abraded, but their insertion points visible. Pleurosternal carinae low, irregular, poorly visible on rings 2–18 (♂) or rings 4–16 (♀). Axial line and transverse middorsal sulci absent. Strictures between pro- and metazona faint and thin, very slightly striolate. Epiproct prominent, flattened dorsoventrally, shovel-shaped and roundly subtruncate, with three tufts of setae at caudal margin. Hypoproct roundly subtrapeziform, slightly excavate at caudal margin between round paramedian papillae, each located near caudal margin and each with a tuft of setae. Limbus entire, thin, without peculiarities.

Sternum between ♂ legs 1 very narrow, coxae being very short and subcontiguous. Sternum between ♂ legs 2 similarly very small, but coxae much larger, nearly normal, a little bulged ventrad and each with an inconspicuous gonopore. Sterna between ♂ legs 3–7 increasingly, but gradually broadened, sterna between ♂ coxae 4–7 each with two small setigerous papillae. Sternum between coxae 7 excavate and broad. Sternum between ♂ coxae 9 almost flat, broad and with 1+1 small setigerous papillae near each coxa. Sterna between following ♂ coxae with weak cross-impressions, each divided transversely in into two and bearing a small setigerous papilla near each coxa, transverse impressions being slightly deeper than axial ones ( Fig. 2 ).

Legs of ♂♂ mostly ca 1.3–1.4, of ♀♀ ca 0.8–0.9 times as long as midbody height. In length, femur> tarsus> prefemur> coxa> postfemur = tibia. Claw light brown, clearly curved ventrad, about third as long as tarsus.

Gonopodal aperture regularly subvoid. 1.5 times as broad as long. Lateral margins clearly, caudal margins slightly, elevated, all margins being granulated, not shifted onto prozonum 7. Aperture taking up most of metazonum 7, only a little broader than sternum 9.

Gonopods ( Figs 5, 6 ) simple, typical of the genus. Coxite very short, about third as long as telopodite, subcylindrical and bare. Prefemorite about 2 times as long as acropodite, as usual densely setose, not very distinctly demarcated from acropodite by an oblique ventral sulcus. Acropodite as usual bipartite, solenomere (sl) being a shorter, slightly sigmoid, mesal branch, vs a longer, curved and similarly acuminate lateral branch (lb). Seminal groove (sg) as usual, running entirely on mesal side of telopodite before moving onto solenomere.

REMARKS. Size variations are considerable, but they seem to be quite natural for A. convexus , one of the largest congeners so far known: body length 70–75 mm, width 7–11 mm (♂), or 80–85 mm, 10–13 mm (♀), respectively [ Carl, 1902], vs length ca 62–69 mm, width 10–12 mm (♂) or length ca 62–65 mm, width 11.6–13.9 mm, respectively (♀) (our samples). Variations in coloration are likewise considerable, but also quite natural, basically from yellowish to brown, sometimes with a pattern of darker brown cingulations on prozona ( Figs 1, 2 ).

The only other congener hitherto recorded from Costa Rica is A. niteus Chamberlin, 1922 , from the “basin of San Juan River”, either Alajuela or Heredia Province [ Hoffman, 1999], a similarly large species (♂ length 65 mm, width 10 mm), but differing readily in polygonal areations on metaterga missing mid-dorsally [ Chamberlin, 1922].

Competing interests. The authors declare no competing interests.

Acknowledgement. We are most grateful to Dmitry V.

Logunov (ZISP) who rendered us his material for treatment.

Figures

Figs. 1–6. Amplinus convexus (Carl, 1902), ♂ from La Selva Biological Station. 1, 2 — habitus, dorsal and ventral views, respectively; 3 — body rings 6–8, lateral view; 4 — caudal part of body, lateral view; 5, 6 — right gonopod, dorsal and venral views, respectively. Photographs taken not to scale. Рис. 1–6. Amplinus convexus (Carl, 1902), ♂ иЗ биологической станции La Selva Biological Station. 1, 2 — обЩий вид, соответственно сверху и сниЗу; 3 — туловиЩные сегменты 6–8, сбоку; 4 — ЗаднЯЯ часть тела, сбоку; 5, 6 — правый гонопод, соответственно сверху и сниЗу. Фотографии снЯты беЗ масштаба.