Benincandona ibikounlei, 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 : 22-30

Benincandona ibikounlei gen. et spec. nov. Hotèkpo & Martens urn:lsid:zoobank.org:act:E07A2BEF-B462-4BD5-B362-07A0B8E110AB

( Figures 10– 15 , 41E, F )

Etymology

The species is named after Prof. Moudachirou Ibikounlé (Université d’Abomey Calavi, Bénin) in recognition of his contribution to the advancement of scientific research in Benin, and in gratitude for his continued support to the career of SJH.

Diagnosis

CpRl elongated (L/H = 2.4), sub-triangular, with greatest height slightly in front of the middle; LV dorsally extending beyond RV, anterior and posterior margins evenly rounded, valve surface smooth. CpD and CpV narrow, with greatest width in the middle and angular lateral sides, anterior and posterior extremities pointed. A2 with seta X short, not reaching base of aesthetasc Y. Second palp segment of Mx1 with basal W almost equalling L. T3 with seta d2 absent. Hp with ls and ms with slightly diverging positions, narrower lobe ls on Hp with skewed rectangular distal margin, extending well beyond lobe ms.

Type material

Holotype

1 ♂, specimen with soft parts dissected in glycerine in a sealed slide, and with valves stored dry ( INV.159215).

Allotype

1 ♀, soft part dissected as the male ( INV.159216). Valves lost: the decalcified valves could not be preserved during the manipulations.

Paratypes

3 ♂♂ dissected as the holotype ( INV.159217, INV.159218, INV.159219) ; 2 ♀♀ dissected as the male ( INV.159220, INV.159221) .

The holotype male comprises both valves and dissected soft parts, but no illustrations are based on this specimen.

Type locality

Benin, Colline Department, Savalou District, town of Tchetti , located in the Zou catchment area (tributary of the Ouémé catchment area), coordinates: 7° 48.965’N, 1° 40.311’E, Leg.: S.J. Hotèkpo, M. Lagnika and P. Martin collected on 09 August 2016 (Locality code BEN072 in Tables 1 and 2) .

Description of male

CpRl ( Figure 10A ) elongated (L/H ratio = 2.4) and sub-triangular, with anterior margin slightly more broadly rounded than posterior margin, dorsal margin bluntly pointed, with greatest height slightly in front of the middle, anterior part sloping almost straight to anterior margin, posterior part sloping almost straight to posterior margin, ventral margin almost straight; LV slightly overlapping RV along anterior, ventral and posterior sides, dorsally strongly overlapping RV; valves externally smooth. CpV ( Figure 10B ) and CpD ( Figure 10C ) narrow and pointed on both anterior and posterior sides, greatest width in the middle, lateral margins angular in the middle; CpV with LV forming a pronounced overlap over RV in the centre.

LVi ( Figure 10D ) elongated and triangular, with anterior margin slightly more broadly rounded than posterior margin, dorsal margin bluntly pointed, with greatest height in the middle showing an overlap, anterior part sloping almost straight to anterior margin, posterior part sloping almost straight to posterior margin, ventral margin almost straight, with a slight inward curl in the middle; one ventral il and antero-ventral tooth.

RVi ( Figure 10E ) elongated, with anterior margin slightly more broadly rounded than posterior margin, dorsal margin greatest height situated about 1/3 from the rear, anterior part sloping almost straight to anterior margin, posterior part sloping almost straight to posterior margin, ventral margin almost straight; il running submarginally along ventral margin.

A1 ( Figure 11B ) consisting of seven articulated segments, one basal and six distal. Basal segment large with c. 2.5 times as long as basal width, supporting two ventro-subapical setae, more proximal about three times as long as second one; and two setae on the dorsal side situated some distance from each other with the more proximal one slightly longer than the second one. First distal segment length about twice the basal width, with one short dorso-apical seta, no ventral apical seta present. Next (second distal segment) about twice as long as wide, with one dorso-apical seta. Third distal segment slightly longer than the previous one, with one short apical seta on each side. Fourth distal segment also slightly longer than the previous one (more than three time as long as wide) with one short ventro-apical seta and one long dorso-apical seta, reaching beyond tip of sixth distal segment with almost half the total length. Fifth distal segment more than four times as long as wide, with two long dorso-apical setae (almost five times longer than the length of the segment) and one short ventro-apical seta slightly exceeding the middle of the next segment. Sixth distal (terminal) segment, narrow, c. five times as long as wide, bearing one short and two longer setae and one aesthetasc (Ya). Both long setae about 2.5x the length of Ya, length of the short one is about half the length of Ya.

A2 ( Figure 11A ) with a basal segment broad and rounded, mid-ventrally with one seta of medium length, two subapical setae of unequal length, proximal one c. twice the length of the more apical one. Second segment (second protopodite) large and c. twice as long as basal width, set with one short ventro-subapical seta X. No remnant of exopodite visible. Endopodite consisting of four segments with the penultimate segment divided. First endopodal segment long c. five times as long as basal width, carrying one long mid-ventral aesthetasc (Y) (reaching tip of segment) and two ventro-apical setae, one short and one long, hirsute in its distal 4/5. Second endopodal segment (segment 2A) c. twice as long as wide, carrying one stout dorso-apical seta and three t-setae; seta t1 long, narrow and plumose, accompanied by a long and slender, but well-developed aesthetasc y1; setae t2 (ventro-apical) and t3 (centro-apical) hyper-developed into male bristles. Third endopodal segment (segment 2B) smaller than previous segment and almost as long as wide, set with a complex (and sexually dimorphic) apical chaetotaxy ( Figure 40 ): ventro-apically with one short and slender aesthetasc y2 and the claw G3 transformed into short seta of almost equal length; centrally with one short seta z3; dorso-apically, with z1 claw-like, length twice as long as penultimate segment. Claw G2 about 2.5 times as long as z1; z2 seta transformed into long claw, slightly shorter than G1. Fourth endopodal, terminal, segment with one long claw (Gm), one short claw (GM), a long aesthetasc y3 with shorter accompanying seta, with fused part short, and seta g slightly longer than aesthetasc y3.

MdCoxa ( Figure 11C–D ) 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. Remark: asymmetry illustrated possibly resulting from different position in slide.

MdPalp ( Figure 12C ) consisting of four segments. Basal segment ventro-apically with two hirsute setae, S1 (long, reaching tip of terminal segment) and S2 (short and stout, length about one third of the length of S1), in between with the short flagellum-like alpha seta (thin and about as long as S2), and one smooth and medium length, 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 2 setae of sub-equal 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, about as long as the fused claw.

Mx1 ( Figure 12A, B ) with a basal (protopodite) part carrying a large respiratory plate (exopodite), three endites and a two-segmented palp (endopodite). Respiratory plate ( Figure 12B ) elongated, carrying c. 13 plumose respiratory rays, two short distal setae and a group of four shorter proximal setae of unequal length. Palp ( Fig 12A ) with first segment carrying four long dorso-apical setae; terminal segment short and rectangular, carrying also 4 distal setae, some slightly claw-like; chaetotaxy of three endites incompletely illustrated: third endite with two strong teeth carrying lateral spines (Zahnborsten), basally with one lateral seta; sideways directed bristles near base of first endite one long and one short c. half the length of the long one.

T1 ( Figure 15A, B ) basal part (protopodite) carrying respiratory plates (exopodites, not shown), distally set with 4+7 setae of different morphology and length; more proximally with setae d and b of medium length. Prehensile palps ( Figure 15A, B ) one-segmented, distally sigmoid hook-like, both palps set with a short sensory organ and proximally with two subequal setae (also sensory organs); Lpp ( Figure 15A ) slightly narrower than Rpp ( Figure 15B ).

T2 ( Figure 13D ) with 4-segmented endopodite (penultimate segment divided), elongated, without basal setae. Setae d1 and d2 absent. First endopodal segment without any setae, length c. five times as long as basal width. Second endopodal segment (2A) set with one short ventro-apical seta f, length c. 3x basal width. Third endopodal segment (2B) of about the same length/width ratio as the previous segment and with one ventro-subapical seta g, reaching about 1/3 of following segment. Terminal segment about 1.5 times as long as basal width, apically two short setae, h1 ventral and h3 dorsal; and a long slender claw (h2), distally set with short setulae.

T3 ( Figure 13C ) first segment with only one medium length seta d1. Second (knee-) segment without any seta. Third segment about 5x as long as wide, not carrying any seta. Fourth segment narrower, c. 7x basal width and slightly longer than the previous segment, carrying one short subapical seta g. Terminal segment well-separated from penultimate segment, L c. 1.5x basal width and carrying three setae: one long and reflexed (h3), clearly exceeding half of the third segment and two ventrally directed short setae h1 and h2, the former c. half the length of the latter.

CR ( Figure 13A ) with ramus stout; claw Ga well-developed, stout with length ratio ramus/claw Ga = 1.5, setae Sp (posterior seta), Sa (anterior seta) and claw Gp (posterior claw) reduced to small setae.

CRAtt ( Figure 13B ) long and stout, distally bifurcated and subapically with additional lateral branch.

Hp ( Figure 14B–D ) of medium size, with (ls) relatively narrow, with skewed rectangular distal part, reaching well beyond the asymmetrically rounded ms; lobe ‘h’ shorter and sub-rectangular; internal anatomy ( Figure 14C, D ) with postlabyrinthal spermiduct with one circular coil.

Zenker organ ( Figure 14A ) with c. seven spinous whirls, relatively long and with an elongated central tube joining posterior funnel-shaped end plate to anterior end plate.

Description of female

Cp and valves most likely as in the male, without obvious sexual dimorphism (see remark above).

Limbs ( Figure 15C–E ) largely as in the male, but with sexually dimorphic A2 and T1.

A2 ( Figure 15C ) with second endopodal segment undivided, with two t-setae, t1 (long, narrow and plumose) and t2 (thin and smooth); apical chaetotaxy ( Figure 40 ) with z1 claw-like, z2 and z3 being both setae, z1 twice as long as z2 and z3; claws G1, G2, G3 and GM all reaching to 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 15E ) with basal part with c. 10 distal setae of unequal length, setae b and d present, with long additional seta (d’) present close to seta d; respiratory plate hidden on the dissected specimens. Endopodite a broad and short palp, with 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 only (see Table 1).

Figures

FIGURE 10. Benincandona ibikounlei gen. et spec. nov., valves. A. INV.159222. CpRl. B. INV.159222. CpV. C. INV.159223. CpD. D. INV.159224. LVi. E. INV.159224. RVi. Scale bar = 500 µm.

FIGURE 11. Benincandona ibikounlei gen. et spec. nov., limbs (♂). A. A2 (INV.159219, INV.159217, INV.159218). B. A1 (INV.159219, INV.159218). C, D. MdCoxa, (INV.159218). Scale bar = 50 µm.

FIGURE 12. Benincandona ibikounlei gen. et spec. nov., limbs (♂). A. Mx1 (Chaetotaxy incomplete) (INV.159218). B. Mx1, respiratory plate (INV.159218). C. MdPalp (INV.159218). Scale bar. 1 (B), 2 (C), 3 (A) = 50 µm.

FIGURE 13. Benincandona ibikounlei gen. et spec. nov., limbs (♂). A. CR (INV.159219). B. CRAtt (INV.159219). C. T3 (INV.159219). D. T2 (INV.159217). Scale bar = 50 µm.

FIGURE 14. Benincandona ibikounlei gen. et spec. nov., limbs (♂). A. Zenker organ (INV.159219). B–D. Hp (INV.159219). B. External view (drawing). C. Internal view (photograph without interference contrast). D. Internal view (photograph with interference contrast). Scale bar = 50 µm.

FIGURE 15. Benincandona ibikounlei gen. et spec. nov., limbs (A–B ♂ and C–E ♀). A. T1, Lpp (INV.159219). B. T1, Rpp (INV.159219). C. A2 (INV.159216). D. CR (INV.159216). E. T1 (INV.159221). 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.