Streptocephalus wolof, Sainz-Escudero & Alonso & Sánchez-Vialas, 2022

Sainz-Escudero, Lucía, Alonso, Miguel & Sánchez-Vialas, Alberto, 2022, Diversity and distribution of Anostraca in temporary ponds in Western Africa with description of a new species of Streptocephalus Baird, 1852 (Pancrustacea: Branchiopoda: Streptocephalidae), Zootaxa 5213 (4), pp. 388-412 : 397-399

Streptocephalus wolof sp. nov.

( Figs. 6–9 )

Etymology. The name wolof refers to the ethnic group native to Senegal, Gambia, and in a lesser extent, to Mauritania. Most of the known geographic range of the newly described species overlaps with the Wolof ethnic distribution. The name is a noun in genitive case.

Type material. Holotype. Male: Senegal, Tambacounda, 6 km west of Koutenabe , 93 m, 14 º 15′34.38″N, 12 º 35′42.38″W, 16-VIII-2015 (white label, printed); MNCN 20.04 /20321 (white label, printed) ; Holotypus, Streptocephalus wolof Sainz-Escudero, Alonso & Sánchez-Vialas , des. 2022 (white label printed).

Paratypes. 20males, 15 females: Senegal, Saint-Louis, 2 km north of Podor , 9 m, 16 º 40′17.43″N, 14 º 57′55.29″W, 18-VIII-2015 (white label, printed); MNCN 20.04 /20269–20.04/20289 and 20.04/20327–20.04/20340 (white label, printed). Twenty-six males , 50 females: Senegal, Ziguinchor, Diembéreng , 9 m, 12 º 28′00.61″N, 16 º 47′02.16″W, 13-VIII-2015 (white label, printed); MNCN 20.04 /20290–20.04/20302 and 20.04/20341–20.04/20403 (white label, printed). Thirteen males , 22 females: Senegal, Matam, 1.9 km south-east of Bokiladji, 30 m, 15 º 02′48.91″N, 12 º 43′49.78″W, 17-VIII-2015 (white label, printed); MNCN 20.04 /20303–20.04/20320 and 20.04/20404- 20.04/20420(white label,printed). Five males: Senegal, Tambacounda, 6km west of Koutenabe , 93 m, 14 º 15′34.38″N, 12 º 35′42.38″W, 16-VIII-2015 (white label, printed); MNCN 20.04 /20321–20.04/20326 (white label, printed). All paratypes labelled : “ Paratypus, Streptocephalus wolof Sainz-Escudero, Alonso & Sánchez-Vialas , des. 2022 (white label printed) ( Table 2 ).

Description. Male. Head ( Fig. 6A ) round. Nuchal organ visible. Eyes spherical with diameter as long as its corresponding eyestalk.

First antennae filiform, 2 times longer than basal joint of second antenna ( Fig. 6A ). Distal end with 3 subdistal setae, approximately 2–2.5 times longer than antennular thickness ( Fig. 6B ).

Frontal appendage ( Fig. 6C ) consisting of 2 slightly curved long and pointed branches, reaching half-length of distal antennomere, with 2 small tips at inner margin, one close to base and other approximately in its half. Single acute basal projection in its ventral surface, whose length is about one-third of the latter.

Second antennae ( Fig. 6D ) reaching thoracopod IX or X when extending backwards. Proximal and distal antennomeres subcylindrical, similar in length, 2 times as long as broad. Inner longitudinal row of 12 or 13 small papillae (sp) from medial part of proximal antennomere to medial part of distal antennomere. Medial part of distal antennomere with transversal row of 5–7 small papillae. Small papillae consist of a conical base with 1 apical small sensory seta. Apical joint (aj) oriented ventrolaterally, at distal end of basal joint, approximately as long as distal antennomere. Hand (according to Maeda-Martínez et al. 1995b) with 2 sharp and smooth rami. Longest ramus (anterior primary ramus, “thumb) 2 times longer than distal antennomere, slightly curved at end of proximal third; small subtriangular blunt (spur) present in its proximal part. Shorter ramus (posterior ramus, “finger) 0.6 times of anterior primary ramus length, and dorsally bent; proximal part with a small rounded protruding structure followed by short thickening.

Labrum ( Fig. 6E ) subtrapezoidal, without distal protuberances; terminal fleshy process straight, tapering distally. Two setulose pads placed ventrally midway and in the base of fleshy process.

Phyllopodia with gross structure, typical of the genus ( Figs. 7A–E ). Eleven pairs of thoracopods. First thoracopod ( Fig. 7A ) 2 times shorter than seventh thoracopod ( Fig. 7C ); eleventh thoracopod ( Fig. 7E ) 0.8 times longer than seventh thoracopod; rest of thoracopods subsimilar in size. Praepipodite (PE) oval, with serrated outline in all thoracopods. Epipodite (EP) wide, with undulated margin ( Figs. 7A, C ) in the tenth anterior thoracopod; eleventh thoracopod epipodite elongated, with serrated extreme ( Fig. 7E ). Exopodite (EX) oval, bordered by plumose marginal setae; first thoracopod small ( Fig. 7A ), not sticking out from endopodite; rest of thoracopods ( Figs. 7C, E ) of similar size to endopodite. Endopodite (EN) broad, covered by short plumose setae in its outer margin, and provided with a more or less marked depression in the middle ( Figs. 7A, C, E ). Endites from first to tenth thoracopods: first endite with 2 submarginal spine-like setae on anterior surface, proximal one long and thin, provided with denticles, and distal one shorter, spiniform, with a basal tiny spine-like seta ( Figs. 7A, C ); second endite with a long spiniform proximal seta, submarginal on anterior surface, with a basal tiny seta ( Figs. 7A, C ); third endite with 2 unequal submarginal spinelike seta on anterior surface and three plumose setae on posterior surface ( Figs. 7B, D ); 4 endite with 2 unequal submarginal spinelike seta on anterior surface and 2 plumose setae on posterior surface ( Figs. 7B, D ); fifth endite with 3 unequal submarginal spinelike seta on anterior surface and 2 plumose setae on posterior surface ( Figs. 7B, D ). Endites to eleventh thoracopod ( Fig. 7E ): first endite with submarginal spine-like setae very reduced; second endite with 2 small spines on anterior surface and 3 plumose setae on posterior surface; third and fourth endites with 2 small spines in anterior surface and 2 plumose setae on posterior surface; fifth endite with 1 small spine in anterior surface and 2 plumose setae on posterior surface.

Abdominal segments ( Fig. 8A ) typical of the genus. First, second, and third segments with 2 small cuticle projections, one at each side, close to posterior margin (pointed with arrow in Fig. 8A ).

Genital segments ( Fig. 8B ) slightly expanded and partially fused. First segment ventrally smooth. Second segment with linguiform outgrowths 2 times shorter than basal part of gonopods, placed posterolaterally on ventral surface. Basal part of gonopods non-retractile, reaching the end of third abdominal segment; spinulated appendix located in its basal inner side and 2 rounded expansions in its distal end. Everted part of gonopods twice longer than basal part, provided with longitudinal rows of spines.

Cercopods ( Fig. 8C ) of the type “spinose cercopods sensu Maeda-Martínez (1995b), sclerotized, with short spine-like setae replacing the marginal plumose setae on the distal half. Cercopods as long as the last 4 abdominal segments. Anus terminal.

Female. First antennae ( Fig. 9A ) filiform 4 times longer than eye diameter, and 2 and a half longer than second antenna. Distal end as in male.

Second antennae ( Fig. 9A ) broad with rounded end, little longer than eye plus stalk. Distal surface and margins bearing short setae. One small marginal beak on anterior edge close to distal end.

Thoracopods as in male.

Abdominal segments ( Fig. 9C ) with smooth surface. Some of them bearing warty outgrowths provided with sensillae (in fourth and sixth segments in the figure).

Genital segments ( Fig. 9C ) completely fused. Brood pouch elongate, fusiform extending to middle of fourth abdominal segment; end provided with an angular flat expansion directed posteriorly ( Fig. 9D ).

Eggs subspherical; surface covered by wide protruding keeled ribs delimiting polygonal fields ( Fig. 3A ). Diameter around 200 µm.

Cercopods ( Fig. 9E ) broad in the base, margined on both sides by feathery setae gradually shortening to their acute end. Length as last four abdominal segments plus telson.

Size. Total body length of the holotype (MNCN 20.04/20321), (including cercopods setae): 7.48 mm. Largest female specimen recorded: 10.56 mm.

Geographic distribution. Streptocephalus wolof is known from the following localities in Senegal: 2 km north of Podor, Diembéreng, 1.9 km south-east of Bokiladji, 6 km east of Koutenable and Diabal ( Table 2 ). Future studies could likely extend its distribution to the neighboring countries Mauritania, Gambia, Mali, Guinea, and Guinea-Bissau. The previous recorded populations identified as S. zeltneri in Senegal [Lingure and Palagu ( Monod 1969; Hamer et al. 1994b; Maeda-Martínez et al. 1995b)] require revision as they were not examined by us, and therefore, we were unable to confirm its taxonomic identity. However, we tentatively treated these records as S. zeltneri until additional studies confirm its identity ( Fig. 1 ).

Remarks. The new species is closely related to Streptocephalus zeltneri . Both species cannot be distinguished based on adult morphological characters, and consequently they can be considered as cryptic species ( Marrone et al. 2017). However, they differ on the basis of the eggs macrosculpture. Eggs of S. wolof present their surface covered with carinated ribs, delimiting polygons of variable number of sides ( Fig. 3A ). This trait was consistent in each revised population that contained mature females.

Streptocephalus wolof is the most commonly found and widespread Anostraca species in Senegal, occurring in several ecoregions (including the Sahelian and Sudanian savannas, and the Guinean forest savanna close to the Guinean forest) ( Fig. 1 ). The studied specimens of S. wolof were found during the rainy season in temporary ponds, both with transparent and turbid waters, often in syntopy with amphibian larvae, as Sclerophrys xeros ( Tandy, Tandy, Keith & Duff-MacKay, 1976), Kassina senegalensis ( Duméril & Bibron, 1841) , K. fusca Schiøtz, 1967 , Ptychadena bibroni ( Hallowell, 1845) , and Phrynobatrachus francisci Boulenger, 1912 ( Fig. 5 ).

Figures

FIGURE 1. Different sampled water masses with presence of Anostraca across Senegal: A, Tilagne, Sahel eco-region, habitat of Branchinella chudeaui; B, Bandafassi, Sudanian savanna, habitat of Streptocephalus zeltneri; C, Bokiladji, Sahel eco-region, both are habitats of Streptocephalus wolof sp. nov.; D, Gourel Yoba, Sudanian savanna, habitat of Streptocephalus sudanicus.

FIGURE 3. Electronic scanning microscope images of the eggs of: A, Streptocephalus wolof sp. nov., 2 km north of Podor; B, Streptocephalus zeltneri, Bandafassi; C, Streptocephalus sudanicus, Gourel Yoba; D, Branchinella (B.) chudeaui, Tilagne Tokossel. Scale bar indicates 100 µm for each egg sample.

FIGURE 5.A, temporary pond in Diembéreng, habitat of Streptocephalus wolof sp. nov.; B, several living male specimens of S. wolof sp. nov. from the same pond figured in A; note the presence/absence of the red coloration in the cercopods; C, habitus of a female specimen from the same pond figured in A; note the brood pouch coloration and the red color extended over the cercopods and the last abdominal segments.

FIGURE 6. Streptocephalus wolof sp. nov., male from Diembéreng, Ziguinchor, Senegal: A, head dorsal view; B, tip of first antenna; C, frontal appendage, lateral view; arrow points acute projection; D, second antenna, dorsal view; E, labrum lateral view. Aj = apical joint, sp = small papillae, apr = anterior primary ramus, pr = posterior ramus, s = spur. Scale bars = 0.5 mm.

FIGURE 7. Streptocephalus wolof sp. nov., male from Diembéreng, Ziguinchor, Senegal: A, first thoracopod; B, detail of endites 3–5 of first thoracopod; C, seventh thoracopod; D, detail of endites 3–5 of seventh thoracopod; E, eleventh thoracopod. EX = exopodite, EN = endopodite, EP = epipodite, PE = preepipodite, 1–5 = endites. Scale bars = 0.5 mm.

FIGURE 8. Streptocephalus wolof sp. nov., male from Diembéreng, Ziguinchor, Senegal: A, genital and abdominal segments., arrow points small cuticle projections; B, gonopods; C, cercopods. lo, lateral linguiform outgrowts; sia, spinulated inner appendix; bp, basal part of gonopods; ep, everted part of gonopods. Scale bars = 0.5 mm.

FIGURE 9. Streptocephalus wolof sp. nov., male from Diembéreng, Ziguinchor, Senegal: A, head, dorsal view, arrow points a marginal beak; B, tip of first antenna; C, genital and abdominal segments; D, gonopore, lateral view; E, cercopods, ventral view. Scale bars: A–C, E = 0.5 mm; D = 0.2 mm.