Bosminopsis africanus

(Figs. 1 – 2)

Parthenogenetic female. Morphology (Fig. 1 A – D) fully conforms to that described earlier for other populations from SE Asia (Garibian et al. 2021 b). Description of adult male. Body (Fig. 1 E – F) short, transparent (width to length ratio 0.66 – 0.67). Dorsal margin of body humpbacked, dorsal margin of carapace straight. Head (Fig. 1 G – H) relatively large, with a smooth rostrum, eye relatively large, labrum rounded and naked. Valves. Posterior portion straight. Postero-ventral angle with a single long seta (seta Kurzi) and a single welldeveloped mucro (Fig. 2 D: arrow), but sometimes the latter absent in largest adults (Fig. 2 C: arrow). Ventral valve portion with several short spines. Antenna I (Fig. 2 A) movable, frontal sensory seta attached somewhat closer to base than tip. On inner margin of its proximal part, there are three tufts of short setulae and a short male seta. Distal part with nine aesthetascs of subequal size, and few minute spines located at the inner margin. Antenna II with a single seta on coxopodite (Fig. 2 B, arrow) its length c. a. 1 / 3 basal segment length. Apical seta of basal segment (Fig. 2 B, arrow) relatively long (longer than proximal endopod segment). Distal endopod segment bears a long additional seta (Fig. 2 B, arrow). Postabdomen (Fig. 2 E) as in parthenogenetic female, ventral edge slightly curved, preanal and anal margins straight, postanal angle absent. Postabdominal claw bears a single basal spine comparable in size with the former. Limb I (Fig. 2 F – G) with outer distal lobe bearing two setae of different size, inner distal lobe with a copulatory hook and a seta (Fig. 2 F – G: arrow). Inner distal lobe of limb III (Fig. 2 H) as in parthenogenetic female: it bears six soft setae. Size. In our material, female length 0.19 – 0.4 mm, adult male length 0.29 – 0.31 mm.

Material examined here. Many parthenogenetic females and three males from a large un-named reservoir, South Vietnam (10.459098 ° N, 104.937477 ° E) collected on 07.04.2023 by A. A. Kotov, P. G. Garibian and Vietnamese colleagues. Sample is now kept in the research collection of A. A. Kotov, A. N. Severtsov Institute of Ecology and Evolution, Moscow, Russia, accession number AAK M- 7790.

(Figs 2 – 5) Africa: Daday 1908: 212 (Bosminella Anisitsi var. africana); Daday 1910: 140 – 141, 152, 154, Pl. 8: Figs 1 – 2 (Bosminella Anisitsi var. africana); Brehm 1913: 36 – 39, Figs 3 – 6 (deitersi); Dumont & Verheye 1984: 315, Fig. 3 (deitersi); Kořínek 1984: 47 – 48, Figs 22 – 23 (deitersi). Asia: Brehm 1963: 170 – 171, Figs 16 – 19 (deitersi); Uéno 1966: 103 – 104, Figs 31 – 40 (deitersi); Mamaril & Fernando 1978: 133, Figs 98 – 99 (deitersi); Idris 1983: 33, 35, Figs 16 (deitersi); Rane 1984 a: 668 (deitersi), 668 – 669, Figs 1 – 3 (devendrai); Rane 1984 b: 714 (deitersi); Michael & Sharma 1988: 99 – 100, Fig. 30 a – e (deitersi); Venkataraman 1988: 232, Fig. 2 (deitersi); Venkataraman 1995: 384, Figs 49 – 52 (deitersi); Maiphae, 2014: 34 – 35, Fig. 19 (deitersi).

Redescription based on the specimens from Thailand. Parthenogenetic female. Body in lateral view subovoid, depression between head and valves absent (Figs. 2 A, B). Dorsal margin regularly convex, postero-dorsal and postero-ventral angles rounded in old adults (Fig. 2 A), but expressed in smaller adults (Fig. 2 B) and juveniles (Fig. 2 C). Ventral margin from slightly convex to almost straight; anterior margin of valves slightly convex. Head relatively large, with a low ocular dome, reticulation maximally expressed on its anterior face (Fig. 2 B). Compound eye of moderate size, ocellus absent. Lateral and dorsal head pores absent. Labrum with fleshy and round main body (Fig. 2 A). Valve subovoid. Antero-ventral portion of valves with a series of setae (Fig. 2 A). Ventral margin slightly convex, with a series of small spinules and a long seta. Postero-ventral angle of valves with a single short mucro and sometimes with one additional relatively long spinule (Figs. 3 G – M). Antennae I in their proximal portions fused together and with rostrum (Fig. 3 A); lateral portions directed downwards and slightly curved (Fig. 3 B). Fused portion of antennae I with two antennular sensory setae. Distal portion of each antenna I with nine aesthetascs. Antenna II coxal portion bearing a single long seta and a single minute seta on a conical elevation. Both exopod and endopod short, consisting of three segments. Antennal formula: setae 0 - 0 - 3 / 1 - 1 - 3; spines 0 - 0 - 1 / 0 - 0 - 1 (Figs. 3 C, D). All antenna II setae equal in size (Fig. 3 C). Maxilla as a small lobe with three setulated setae (Fig. 4 A). Limb I large, epipodite with two long finger-like projections (Fig. 4 B, epp). Outer distal lobe (Fig. 4 B, odl) with two long setae covered by setules. Inner subdistal lobe (in terms of Kotov, 1997 a) bearing only a single setulated seta (Fig. 4 B, sdl). Inner portion of limb corm with three soft setae, two equal in size and third one short; a bunch of long spinules on limb corm. Two ejector hooks different in size, robust, armed with small denticles (Fig. 4 B, ejh). Maxillar process (Fig. 4 B, mxp) bearing a single setulated seta. Limb II small, epipodite with a single short finger-like projection (Fig. 4 C, epp). Inner portion with six anterior setae (1 – 6) and two posterior setae (Fig. 4 C, pos). Distal armature of gnatobase with three setae of different size (Fig. 4 D, dag), filter plate with five setulated setae (Fig. 4 C, fpl). Limb III epipodite with a single finger-like projection (Fig. 4 E, epp); exopodite rectangular (Fig. 4 E, ext), bearing seven (two lateral and five distal) setae (Fig. 4 E, 1 – 7). Inner-distal portion with three anterior seta, seta 1 long, seta 2 shorter than seta 1 and seta 3 very small (Fig. 4 F, 1 – 3). Proximal endite with two anterior setae of same size (Fig. 4 F, 4 – 5). Posterior face of limb with six long soft setae (Fig 4 E, a – f) plus a seta of unclear homology (?). Distal armature of gnatobase with three setae (Fig. 4 F). Filter plate with five setae of similar size (Fig. 4 E: fpl). Limb IV epipodite supplied with a long finger-like projection. Exopodite semicircular, with eight long soft setae (Fig. 4 G, 1 – 8), seta 2 with very short setulation; inner distal portion with four anterior setae (Fig. 4 H, 1 – 4); distal most setae extra thick; posterior portion with four soft setae (Fig. 4 G, a – d). Distal armature of gnathobase reduced (Fig. 4 H, dag), filter plate with four setae of similar size (Fig. 4 G, fpl). Limb V with a small, ovoid preepipodite (Fig. 4 I, pep) and epipodite with a long finger-like projection (Fig. 4 I, epp). Exopodite (ext) ovoid, with five soft setae (1 – 5) covered by long setules. Inner distal portion of limb as a densely setulated flat lobe bearing two soft setae. Distal armature of gnathobase (Fig. 4 I, dag) with two setae, filter plate with two long setae. Postabdomen compressed laterally, slightly narrow distally, without an especial inflated basis of postabdominal setae (Fig. 3 N), which are shorter than postabdomen (Fig. 2 A). Ventral margin straight. Preanal margin almost straight or slightly concave, without setules. Preanal angle expressed. Anal margin curved and postanal margin convex; both margins with series of a small spines. Postabdominal claw regularly curved, its basal spine long (about 2 / 3 of postabdominal claw length, or longer). Juvenile female. Body with lower posterior portion, head relatively high. Dorsal head pore present only in instar I (Fig. 6). Postero-ventral margin of carapace with a single long mucro-like spine and a single long spinule (Figs. 3 E, F). Ephippial female. Most of the body similar to parthenogenetic female, but dorsal portion of valves modified into ephippium (Figs. 2 D, F). Ephippium ovoid, sculptured with large polygons, with strong medial keel and paired lateral keels (Figs. 2 E, F). Ephippial chamber with a single egg. Adult male. Unfortunately, only a single slide was available making impossible a detailed description. Body elongated, dorsal contour of head humped, dorsal contour of carapace almost straight, a slight depression between head and carapace. Head large, with specially large eye; ocular dam expressed; rostrum smooth (Fig. 2 G). Valve armed as in female; postabdomen similar to that of the female. Antenna I free in proximal portion; frontal seta long, located in middle of antenna I body. Antenna II with a long (as long as endopod), curved additional male seta on endopod apical segment. Limb with a well-developed copulatory hook. Size. Parthenogenetic female 0.19 – 0.4 mm; ephippial female 0.30 – 0.32 mm; male 0.25 mm. Variability. We have compared populations from Thailand with other populations from different regions. All studied populations from Laos, India and Vietnam have same features as populations from Thailand (Fig. 5 A – U). Juvenile stages with a single long mucro or mucro plus an additional relatively long spine on postero-ventral portion of valves; posterior portion of limb III with six soft setae.

Diagnosis. Female. Body of parthenogenetic adult mostly subovoid (Figs. 2 A, B), juvenile female with lower posterior portion (Fig. 2 C). Postero-dorsal projection very short or absent. Reticulation in general not distinct, but well-expressed on head anterior face. Head with a small ocular dome; proximal parts of antennae I in females fused with each other and rostrum (Fig. 3 B). Exopod and endopod of antenna II with three segments (Figs. 3 C, D). Valves of adult with a single short mucro-like spine (Figs. 2 A, B), juvenile female with a single long mucro and a short mucro-like spine (Figs. 3 E – M). Maxilla I with three setae (Fig. 4 A). Five pairs of thoracic limbs (Figs. 4 B – I) as in other species of B. deitersi group, but inner-distal portion of limb III with six posterior (soft) setae (Fig. 4 E: a – f). Postabdomen without an especial basis of postabdominal setae; basal spine on postabdominal claw very large (longer than half of claw length) (Fig. 3 N). Ephippial female egg chamber sculptured by large polygons (Figs. 2 D, F), lateral keels not so sharp as in B. deitersi and not so large as in B. zernowi. Adult male (Fig. 2 G) has a shallow depression between head and valves; postero-ventral angle with a single mucro; limb I with a copulatory hook relatively large and thick, and blunt tip.

Differential diagnosis. Populations of Bosminopsis from SE Asia belonged to Bosminopsis deitersi species group. We have concluded that all studied populations belong to a single species, Bosminopsis africanus, initially described from Africa (Daday 1908), see below. Most part of North and East Eurasia is inhabited by another member of this group, B. zernowi. Original detailed drawings of this taxon are represented here (Figs 6 C, 7 – 9), but we do not represent here its redescription as it was already given previously (Garibian et al. 2021). Adequately described members of the B. deitersi group (Kotov, 1997 a; Garibian et al., 2021) are morphologically similar. Taxon from Oriental zone differs from B. zernowi in several features like a single long mucro-like (plus, sometimes, a relatively long additional spine) on postero-ventral portion of juvenile female valves; only one strong mucro-like spine in adult female; posterior portion of limb III with six soft, long setae (a – f); seta 1 of distal endite significantly longer than seta 2 (See Table 2). B. deitersi also have a single mucro-like spine on valves at adult and juvenile stages (Fig. 6 A). However, B. deitersi and B. zernowi have seven soft setae (a – g) on posterior portion of limb III and seta 1 have same size than seta 2 on distal endite of limb III. See Table 2 for some other characters.

Distribution. B. africanus was recorded (as B. deitersi) from many African countries (see Synonymy). We found this taxon in India, Myanmar, Cambodia, Thailand, Laos, Vietnam, Philippines, Malaysia and Papua New Guinea. Analysis of literature data (see Synonymy) confirms that is widely distributed through whole Oriental zone. It is present in the water bodies of different types, from large rivers, man-made reservoirs and large natural lakes to small ponds. But it is absent in temporary water bodies, probably resting eggs do not pass alive through drying.

Type locality. “ Nyassa ” (Daday 1908) = Lake Victoria, Tanzania. Type material. Lost. Absent in the Collectio Dadayana, the Hungarian Natural History Museum, Budapest, Hungary (Forró & Frey 1982). Material examined here. See Table 1.