Benincandona cebios, Hotèkpo & Schön & Martens, 2024

Hotèkpo, Sourou Joseph, Schön, Isa & Martens, Koen, 2024, An endemic species flock of Candonidae Kaufmann, 1900 (Crustacea, Ostracoda) from wells in Benin (Africa), with the description of a new subfamily, a new genus and five new species, Zootaxa 5503 (1), pp. 1-72 : 41-51

Benincandona cebios gen. et spec. nov. Hotèkpo & Martens urn:lsid:zoobank.org:act:24C55080-D65E-467E-8CCB-EACDD6CCF559

( Figures 24–31 , 41K–N )

Etymology

The species is named after CEBioS, the Belgian project “Capacities for Biodiversity and Sustainable Development”, which funded various field trips in Benin, the first visits of SJH to Brussels, and provided a microscope for work in Benin through the GTI program, the “Global Taxonomic Initiative”.

Diagnosis

CpRl elongated (L/H = 2.2), sub-triangular, with greatest width slightly behind the middle; LV dorsally extending beyond RV, anterior margin bluntly pointed and with anteroventral part straight, posterior margin asymmetrically rounded towards the ventral side, valve surface smooth in the anterior and posterior part, with slight ridges in the middle section. CpD and CpV narrow, with greatest width in the middle and evenly rounded lateral sides, posterior extremities bluntly rounded compared with anterior end pointed. A2 with seta X short, just reaching base of aesthetasc Y. This aesthetasc Y distally asymmetrically bifurcated. Second palp segment of Mx1 with L c. 2.1x basal W. T3 with seta d2 short. Hp with ls and ms with overlapping positions, lobe ls broad, distally rounded, extending beyond lobe ms with circa half of its length.

Type material

Holotype

1 ♂, with soft parts dissected in glycerine in a sealed slide, and with valves stored dry ( INV.159244).

Allotype

1 ♀, dissected and stored as the male ( INV.159245).

Paratypes

5 ♂♂ dissected and stored as the holotype ( INV.159246, INV.159247, INV.159248, INV.159249, INV.159250) ; 4 ♀♀ dissected and stored as the male ( INV.159251, INV.159252, INV.159253, INV.159254) ; 3 ♂♂ carapaces stored dry in micropalaeontological slides ( INV.159255, INV.159256, INV.159257) ; 1 ♀ carapace stored dry in micropalaeontological slide ( INV.159258) .

Type locality

Benin • Borgou Department, Tchaourou District , town Badékparou, located in the Okpara catchment area (tributary of the Ouémé catchment area) , coordinates: 9°13.297’N, 2°33.745’E, Leg.: S.J. Hotèkpo and M. Lagnika collected on 11 October and 06 November 2022 (Locality code BEN065 in Table 1 and 2).

Other material investigated

See Table 1 for a list of localities where the present species was collected.

Description of male

CpRl ( Figure 24A–C ) elongated (L/H ratio=2.0) and sub-triangular, dorsal margin bluntly pointed, with greatest height slightly behind the middle, anterior part of dorsal margin sloping almost straight to anterior margin, passing into it with a blunt angle, anteroventral part of anterior margin straight, posterior part of dorsal margin sloping to ventral margin, the latter almost straight; LV overlapping RV along anterior, ventral and posterior sides, dorsally strongly overlapping RV; valve surface smooth in the anterior and posterior parts, with slight ridges in the middle section. CpD and CpV ( Figure 24J, K ) narrow and pointed on both anterior and posterior sides, greatest width in the middle, lateral margins rounded.

LVi ( Figure 25A, C, D, G ) elongated and sub-triangular, dorsal margin bluntly pointed, with greatest height slightly behind the middle, anterior part of dorsal margin sloping almost straight to anterior margin, passing into it with a blunt angle, anteroventral part of anterior margin straight; posterior part of dorsal margin sloping towards ventral margin, the latter almost straight; one ventral il without antero-ventral tooth. CMS ( Figure 25G ) as in the type species.

RVi ( Figure 25B, E, F ) elongated, with dorsal margin partly straight and with greatest height well behind the middle, anterior part of dorsal margin sloping almost straight to anterior margin, passing into it with a blunt angle and with anteroventral part straight, posterior part of dorsal margin sloping towards ventral margin, the latter almost straight; il running submarginally along ventral margin.

A1 ( Figure 27B ) consisting of seven articulated segments, one basal and six distal. Basal segment with two ventro-subapical setae, one long and one shorter, the latter about one third of the length of the longer seta, and two shorter setae on the mid-dorsal side, situated some distance from each other. First distal segment about three times as long as the basal width, with one short dorso-subapical seta. Second distal segment with about the same length/ width ratio as the previous segment, set with one short dorso-apical seta. Third distal segment also with about the same length/width ratio as the previous segment, carrying one short apical setae on each side. Fourth distal segment more than three times as long as wide, and set with two short setae as on the previous segment. Fifth distal segment more than five times as long as wide, set with one short ventro-apical seta and two long dorso-apical plumose setae. Sixth distal segment narrow, more than four times as long as wide, with four apical structures: one aesthetasc Ya of intermediate length, two long but unequal length plumose setae, about twice and 1.5x the length of Ya respectively, and one short plumose seta, about half the length of Ya.

A2 ( Figure 27A ) with basal segment (first protopodite) broad and rounded, mid-ventrally with one seta of medium length, subapically with two setae of unequal length, proximal one c. five times the length of the more apical one (plumose). Second segment (second protopodite) large and c. twice as long as basal width, set with one short and plumose ventro-subapical seta X. No remnant of exopodite visible. Endopodite consisting of four segments (penultimate segment divided). First endopodal segment large and stout, c. three times as long as basal width, carrying one long mid-ventral aesthetasc Y (tip clearly exceeding half of segment) and two ventro-apical setae, one short and one large and stout, hirsute in its distal 4/5. Second endopodal segment (segment 2A) c. twice as long as wide, carrying one stout dorso-apical plumose seta and three t-setae; seta t1 long, narrow and plumose, accompanied by a long and slender, but well-developed aesthetasc y1; setae t2 and t3 respectively ventro and centro-apical, hyper-developed into male bristles. Third endopodal segment (segment 2B) smaller than previous segment and about 1.5x as long as wide, set with a complex (and sexually dimorphic) apical chaetotaxy ( Figure 40 ): ventro-apically with one slender aesthetasc y2 and claw G3 transformed into short seta of almost equal length; centrally with one short plumose seta z3; dorso-apically, z1 claw-like, length about 1.7x as long as penultimate segment. Claw G2 about 2.5 times as long as z1 with G1 slightly shorter; z2 seta transformed into long claw, reaching tip of G1. Fourth, terminal segment (segment 3) with one long claw (Gm), one short claw (GM), a long aesthetasc y3 with shorter accompanying seta, with fused part short, and a seta g (slightly exceeding tip of aesthetasc y3).

MdCoxa ( Figure 27C ) elongated, proximally sharply pointed, medially widened, distally with an obliquely widened end, set with a series (6–7) of strong teeth, interspaced with setae; subapically with a short seta.

MdPalp ( Figure 28C ) with four segments. Basal segment ventro-apically with two hirsute setae (S1 & S2); S1 long, reaching tip of terminal segment and S2 short and stout, length about one fifth of the length of S1; in between with the short flagellum-like alpha seta (thin and about twice the length of S2), and one smooth and medium size, more proximal seta. Second segment of sub-triangular shape, dorso-apically with two setae of unequal length; ventro-apically with a group of four long setae, one of these being the beta-seta. Third segment with two unequal dorso-subapical setae, two mid-dorsal setae, one of which being the gamma seta, and ventro-apically with one seta of medium length. Terminal segment sub-rectangular, apically set with one large claw, fused with the segment over its entire distal margin, accompanied by one smooth lateral seta on each side, slightly shorter than fused claw.

Mx1 ( Figure 28A, B ) with first palp segment carrying four long dorso-apical setae; terminal segment short and rectangular, carrying four distal setae, some slightly claw-like. Respiratory plate ( Figure 28B ) elongated, carrying c. 16 plumose respiratory rays, two short distal setae and a group of about seven shorter proximal setae of unequal length.

T1 ( Figure 31A, B ) consisting of basal part (protopodite), carrying respiratory plates (exopodites) represented by three plumose setae, two short and one medium length. Protopodite ( Figure 31B ) distally set with almost 10 plumose setae of different morphology and length; more proximally set with d, d’ and b setae. Prehensile palps asymmetrical with Rpp ( Figure 31B ) slightly more swollen than Lpp ( Figure 31A ); one-segmented, distally sigmoid hook-like, both palps set with a short sensory organ and proximally with two subequal setae.

T2 ( Figure 29B ) with 4-segmented endopodite (penultimate segment divided), generally elongated. First basal segment without setae d1 and d2. First segment of endopodite elongated (length almost 4x the basal width), without seta. Second endopodal segment (segment 2A), with length c. 3x basal width, set with one short ventro-apical seta f. Third endopodal segment (segment 2B) of about the same length/width ratio as the previous segment, ventro-subapically set with a g-seta. Terminal segment about 1.5 times as long as basal width, apically with two short setae (h1 and h3) and a long and slender claw (h2), distally set with short setulae.

T3 ( Figure 29A ) with first segment carrying only one subapical seta d1, of medium length. Second (knee-) segment with short seta d2. Third segment about 5x as long as wide, not carrying any seta. Fourth segment narrower and at least 5x basal width, carrying one short subapical seta g. Terminal segment well-separated from penultimate segment, length about twice as long as basal width, carrying three setae: one long and reflexed (h3), almost reaching knee-segment and two short ventrally directed and curved setae h1 & h2, the latter slightly exceeding tip of the former.

CR ( Figure 29D ) with stout ramus; claw Ga well-developed, stout with length slightly exceeding half the length of ramus, setae Sp, Sa and claw Gp reduced to small setae; seta Sp situated about at one-fifth length of ramus from distal end, Sa dorso-subapical and Gp ventro-subapical.

CRAtt ( Figure 29C ) long and stout, distally bifurcated, subapically with additional lateral branch.

Hp ( Figure 30B–D ) with robust lobe ls, apically rounded, reaching well beyond symmetrically rounded lobe ms, both lobes overlapping, not diverging; lobe ‘h’ shorter and sub-rectangular; internal anatomy ( Figure 30C, D ) with postlabyrinthal spermiduct with one circular coil.

Zenker organ ( Figure 30A ) long and slightly broad, with c. seven spinous whirls.

Description of female

Cp and valves ( Figures 24D–I , 26A–G ) as in the male, without obvious sexual dimorphism.

Limbs ( Figure 31C–E ) largely as in the male, but with sexually dimorphic A2 and T1.

A2 ( Figure 31C ) with second endopodal segment undivided, with t1-seta (long, narrow and plumose) and t2- seta (thin and smooth); apical chaetotaxy ( Figure 40 ) with z1 claw-like, z2 and z3 being both setae, z1 about twice as long as z2, and z3 slightly shorter than z2; claws G1, G2, G3 and GM all reaching about the same point; seta g and aesthetasc y3 as in the male. Small claw Gm in female homologous to large claw in the male.

T1 ( Figure 31E ) with basal part with c. 10 distal setae of unequal length and morphology, setae d and b present, with long additional seta (d’) present close to seta d; respiratory plate represented by two long and one short rays. Endopodite with a broad palp, carrying three subequal but short apical setae (h1–h3).

Measurements: See Table 3.

Differential Diagnosis: See Table 4.

Ecology and distribution

This subterranean species is presently known from its type locality and from a second, closely situated station, only (see Table 1).

Figures

FIGURE 24. Benincandona cebios gen. et spec. nov., valves (A–C, J–K ♂; D–I ♀). A–I. CpRl (A–C. INV.159255, D–I. INV.159258). J. INV.159256. CpD. K. INV.159257. CpV. Scale bars. 1 (B, E, J, K) = 500 µm; 2 (A, C, D, F, H, I) = 200 µm.

FIGURE 25. Benincandona cebios gen. et spec. nov., valves (♂). A, C, D, G. LVi (INV.159244). B, E, F. RVi (INV.159244). G. CMS. Scale bars. 1 (A, B) = 500 µm; 2 (C–F) = 200 µm; 3 (G) = 50 µm.

FIGURE 26. Benincandona cebios gen. et spec. nov., valves (♀). A, C, D, G. LVi (INV.159253). B, E, F. RVi (INV.159253). G. CMS. Scale bars. 1 (A, B) = 500 µm; 2 (C–F) = 200 µm; 3 (G) = 50 µm.

FIGURE 27. Benincandona cebios gen. et spec. nov., limbs (♂). A. A2 (INV.159244). B. A1 (INV.159244). C. MdCoxa (INV.159248). Scale bar = 50 µm.

FIGURE 28. Benincandona cebios gen. et spec. nov., limbs (♂). A. Mx1-palp (INV.159244). B. Mx1, respiratory plate (INV.159248). C. MdPalp (INV.159244). Scale bars. 1 (B), 2 (A), 3 (C) = 50 µm.

FIGURE 29. Benincandona cebios gen. et spec. nov., limbs (♂). A. T3 (INV.159244). B. T2 (INV.159244). C. CRAtt (INV.159244). D. CR (INV.159244). Scale bar = 50 µm.

FIGURE 30. Benincandona cebios gen. et spec. nov., limbs (♂). A. Zenker organ (INV.159247). B–D. Hp (INV.159244). B. External view (drawing). C. Internal view (photograph without interference contrast). D. Internal view (photograph with interference contrast). Scale bar = 50 µm.

FIGURE 31. Benincandona cebios gen. et spec. nov., limbs (A–B ♂ and C–E ♀). C. A2 (INV.159245). D. CR (INV.159245). E. T1 (INV.159245). A. T1, Lpp (INV.159244). B. T1, Rpp (INV.159244). Scale bar = 50 µm.

FIGURE 40. Diagrams of apical views of the A2 of Benincandona, showing position of (sub-) terminal claws, setae and aesthetascs of the terminal (small circle) and penultimate segment (large circle). For explanations of codes, see Material and Methods (Abbreviations used in text and figures).

FIGURE 41. Benincandona gen. et spec. nov., CpRl. (A, C, E, F, G, I, K, N, O, Q ♂ and B, D, H, J, L, M, P, R ♀). A–D. B. martini. E–F. B. ibikounlei. G–J. B. sakitii. K–N. B. cebios. O–R. B. trapezoides. Scale bar = 500 µm.