Benincandona sakitii, 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 : 30-41

Benincandona sakitii gen. et spec. nov. Hotèkpo & Martens urn:lsid:zoobank.org:act:E0E5C90D-997A-49D8-9FF4-A7E7D8B1AE90

( Figures 16–23 , 41G–J )

Etymology

The species is named after Prof. Nestor G. Sakiti who initiated, in collaboration with Prof. Claude Boutin, subterranean biology research in Benin, in gratitude for his continued support to the career of SJH.

Diagnosis

CpRl elongated (L/H = 2.0), sub-triangular, with greatest height slightly behind the middle; LV dorsally extending beyond RV, anterior margin bluntly pointed and with anteroventral part almost straight, posterior margin asymmetrically rounded towards the almost straight ventral side, valve surface set with polygonal ridges in midventral and central part. CpD and CpV narrow, with greatest width in the middle and evenly rounded lateral sides, anterior margin sharply and posterior margin bluntly pointed. A2 with seta X (medium length) reaching beyond middle of aesthetasc Y in males, beyond tip of aesthetasc Y in females (long). This aesthetasc Y distally asymmetrically bifurcated. Second palp segment of Mx1 with L c. 1.5x basal W. T3 with seta d2 about 2/3 of L of seta d1. Hp with ls and ms with overlapping positions, narrower lobe ls on Hp with skewed rectangular distal margin, extending beyond lobe ms with more than half of its length.

Type material

Holotype

1 ♂, with soft parts dissected in glycerine in a sealed slide, and with valves stored dry ( INV.159225).

Allotype

1 ♀, dissected and stored as the male ( INV.159226).

Paratypes

3 ♂♂, dissected and stored as the holotype ( INV.159227, INV.159228, INV.159229) ; 3 ♀♀ dissected and stored as the male ( INV.159230, INV.159231, INV.159232) ; 3 ♂♂ carapaces stored dry in micropalaeontological slides ( JSH0344 , INV.159235, INV.159236) ; 1 ♀ carapace stored dry in micropalaeontological slide ( INV.159227)

Type locality

Benin, Borgou Department, Tchaourou District , town of Badékparou located in the Okpara catchment area (tributary of the Ouémé catchment area) , coordinates: 9°13.314’N 2°33.790’E, Leg.: S.J. Hotèkpo and M. Lagnika collected on 11 October 2022 (Locality code BEN066 in Tables 1 and 2).

Other material investigated

See Table 2 for a list of localities where the present species was collected.

Description of male

CpRl ( Figure 16A–C, G ) elongated (L/H ratio = 2.0) and sub-triangular, dorsal margin bluntly pointed, with greatest height 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 almost straight, posterior part of dorsal margin sloping towards ventral margin, the latter almost straight; LV overlapping RV along anterior, ventral and posterior sides, dorsally strongly overlapping RV; valve surface set with polygonal ridges in midventral and central part. CpD ( Figure 16I–K ) narrow and sharply pointed at anterior margin, more bluntly pointed at posterior side, greatest width in the middle, lateral margins rounded.

LVi ( Figure 17A, C, D, G ) elongated and sub-triangular, dorsal margin bluntly pointed in the centre, with greatest height behind the middle, anterior part of dorsal margin sloping almost straight to anterior margin, passing into it with a blunt angle, anteroventral part almost straight, posterior part of dorsal margin sloping towards ventral margin, the latter almost straight; one ventral il without antero-ventral tooth. CMS ( Figure 17G ) as in the type species.

RVi ( Figure 17B, E, F ) elongated, dorsal margin 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, anteroventral part straight, posterior part of dorsal margin sloping towards ventral margin, the latter almost straight; il running submarginally along ventral margin.

A1 ( Figure 19B ) consisting of seven articulated segments, one basal and six distal. Basal segment c. three times as long as basal width, supporting two long ventro-subapical setae with the more apical slightly shorter than the other one; and two medium length setae on the dorsal side (one illustrated here), situated some distance from each other. First distal segment about twice the basal width, with one short dorso-apical seta. Second distal segment about the same length/width ratio as the previous segment with one very small dorso-apical seta. Third distal segment about three times as long as basal width, set with one very small apical seta in each side. Fourth distal segment about twice the basal width, with one short ventro-apical seta and one medium length dorso-apical seta, reaching beyond tip of sixth segment with more than the half the total length. Fifth distal segment about four times as long as wide, with two long dorso-apical setae and one short ventro-apical seta clearly exceeding the next segment. Sixth distal segment narrow, c. four times as long as wide, with four apical structures: one aesthetasc Ya of intermediate length, two long setae about twice the length of Ya and one short seta, about one third the length of Ya.

A2 ( Figure 19A ) with a basal segment (first protopodite) 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 protopodite large and stout, c. twice as long as basal width, set with one long ventro-subapical seta X. No remnant of exopodite visible. Endopodite consisting of four segments with the penultimate segment divided. First endopodal segment large, more than five times as long as basal width, carrying one long aesthetasc Y (distally asymmetrically bifurcated) on the mid-ventral side (slightly under tip of segment) and two ventro-apical setae, one short and one large, 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 aesthetasc y1; setae t2 and t3 hyper-developed into male bristles, t2 ventro-apical, t3 centro-apical. 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 slender aesthetasc y2 and claw G3 transformed into short seta of almost equal length; centrally with one short seta z3; dorso-apically with z1 claw-like, length about twice as long as penultimate segment. Claw G2 and G1 about 2.5 times as long as z1, with z2 seta transformed into long claw, reaching tip of G2. Fourth, terminal, endopodal 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 almost as long as aesthetasc y3.

MdCoxa ( Figure 19C–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 positions in slide.

MdPalp ( Figure 20C ) consisting of four segments. Basal segment ventro-apically with two hirsute setae: one long (S1), reaching tip of terminal segment and one short and stout (S2), length about one fifth of the length of S1; in between with a short flagellum-like alpha seta (thin and about 1.5x length of S2); more proximally, one smooth, medium-length seta. Second segment of sub-triangular shape, dorso-apically with two setae of unequal length, ventro-apically with a group of four setae (long and unequal size). Third segment with two unequal dorso-subapical setae, two mid-dorsal setae, one of which being the gamma seta, and ventro-apically with three 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, slightly shorter than the fused claw.

Mx1 ( Figure 20A, B ) palp with first segment carrying four long dorso-apical setae; terminal segment short and rectangular, carrying also four distal setae, some slightly claw-like. Respiratory plate ( Figure 20B ) elongated, carrying c. 15 plumose respiratory rays, two short distal setae and a group of four shorter proximal setae of unequal length.

T1 ( Figure 23A, B ) with basal part (protopodite) carrying respiratory plates (exopodites not shown), distally set with 3+7 setae of different morphology and length including two plumose; more proximally set with d and d’ setae, length of the setae d’ being 1.5x the length of d. Prehensile palps clearly asymmetrical with Rpp ( Figure 23B ) slightly more swollen than Lpp ( Figure 23A ); one-segmented, distally sigmoid hook-like, both palps set with a short sensory organ and proximally with two subequal setae.

T2 ( Figure 21B ) with 4-segmented endopodite (penultimate segment divided), elongated, without basal setae (d1 and d2). First endopodal segment without any setae, length c. four times as long as basal width. Second endopodal segment with length c. 4x basal width, set with one short ventro-apical seta f. Third endopodal segment with about the same length/width ratio as the previous segment and with one ventro-subapical seta g, about 1/3 the length of following segment. Terminal segment about 1.5 times as long as basal width, apically two short setae, h1 ventral and h3 (length being the half of the length of h1) dorsal and a long slender claw (h2), distally set with short setulae.

T3 ( Figure 21A ) with first segment carrying only one medium length seta d1. Second (knee-) segment set with d2-seta. Third segment about 4x as long as wide, not carrying any seta. Fourth segment narrower, c. 7x basal width, slightly longer than the previous segment, carrying one short subapical seta g. Terminal segment well-separated from penultimate segment, length about twice basal width and carrying three setae: one long and reflexed (h3), tip clearly reaching base of the third segment, and two ventrally directed and curved setae h1 & h2, the former c. half the length of the latter.

CR ( Figure 21C ) with stout ramus; claw Ga sigmoid, well-developed and stout, length ratio of ramus and claw Ga approximately 1.6; setae Sp (ventro-subapical), Sa (dorso-apical) and claw Gp (first ventro-subapical) reduced to small setae.

CRAtt ( Figure 21D ) long and stout, distally bifurcated and subapically with additional lateral branch; rounded fist-shaped apical end.

Hp ( Figure 22B–D ) with elongated lobe ls, apically rounded and with a pronounced hump-shaped ventral protrusion, reaching well beyond asymmetrically rounded medium shield (ms), both lobes overlapping, not diverging; lobe ‘h’ shorter and sub-rectangular; internal anatomy ( Figure 22C, D ) with postlabyrinthal spermiduct with one circular coil.

Zenker organ ( Figure 22A ) elongated, with c. seven spinous whirls, with an elongated central tube joining posterior funnel-shaped end plate to anterior end plate.

Description of female

Cp and valves ( Figures 16D–F, H ; 18A–G ) as in the male, without obvious sexual dimorphism.

Limbs ( Figure 23C–E ) largely as in the male, but with sexually dimorphic A2 and T1.

A2 ( Figure 23C ) with second endopodal segment undivided, with two t-setae, t1 (long, narrow and plumose) and t2 (thin and smooth); apical chaetotaxy ( Figure 40 ) with z1claw-like, z2 and z3 being both setae, z1 twice as long as z2 and z3; 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 23E ) with basal part with c. 10 distal setae of unequal length; d, d’ and b setae present; respiratory plate reduced to about three rays, two short, one medium size about twice as long as others. Endopodite with a broad and short palp, set 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 and a second, closely situated station, only (see Table 2).

Figures

FIGURE 16. Benincandona sakitii gen. et spec. nov., valves (A–C, G, I–K ♂; D–F, H ♀). A–H. CpRl, (A–C, G: INV.159235, D–F, H: INV.159237). I–K. INV.159236, CpD. Scale bars. 1 (B, E, I) = 500 µm; 2 (A, C, D, F, G, H, J, K) = 200 µm.

FIGURE 17. Benincandona sakitii gen. et spec. nov., valves (♂). A, C, D, G. LVi (A, C, D. INV.159225; G. INV.159227). B, E, F. RVi (INV.159225). G. CMS. Scale bars. 1 (A, B) = 500 µm; 2 (C–F) = 200 µm; 3 (G) = 50 µm.

FIGURE 18. Benincandona sakitii gen. et spec. nov., valves (♀). A, C, D. LVi (A, C, D. INV.159226). B, E, F, G. RVi (INV.159226). G. CMS. Scale bars. 1 (A, B) = 500 µm; 2 (C–F) = 200 µm; 3 (G) = 50 µm.

FIGURE 19. Benincandona sakitii gen. et spec. nov., limbs (♂). A. A2 (INV.159225). B. A1 (INV.159225). C, D. MdCoxa (INV.159228). Scale bar = 50 µm.

FIGURE 20. Benincandona sakitii gen. et spec. nov., limbs (♂). A. Mx1-palp (INV.159225). B. Mx1, respiratory plate (INV.159227). C. MdPalp (INV.159227). Scale bar. 1 (B), 2 (C), 3 (A) = 50 µm.

FIGURE 21. Benincandona sakitii et spec. nov., limbs (♂). A. T3 (INV.159225). B. T2 (INV.159225). C. CR (INV.159225). D. CRAtt (INV.15922). Scale bar = 50 µm.

FIGURE 22. Benincandona sakitii gen. et spec. nov., limbs (♂). A. Zenker organ (INV.159227). B–D. Hp (INV.159225). B. External view (drawing). C. Internal view (photograph with interference contrast). D. Internal view (photograph without interference contrast). Scale bar = 50 µm.

FIGURE 23. Benincandona sakitii gen. et spec. nov., limbs (A, B ♂ and C–E ♀). A. T1, Lpp (INV.159228). B. T1, Rpp (INV.159228). C. A2 (INV.159226, INV.159231). D. CR (INV.159232). E. T1 (INV.159226). 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.