Alona kolwezii, Damme & Dumont, 2008

Damme, Kay Van & Dumont, Henri J., 2008, The ‘ true’ genus Alona Baird, 1843 (Crustacea: Cladocera: Anomopoda): position of the A. quadrangularis-group and description of a new species from the Democratic Republic of Congo, Zootaxa 1943, pp. 1-25 : 11-15

Alona kolwezii n. sp.

Figs 6–7

Material examined. Holotype, undissected, parthenogenetic female, mounted in glycerol on a glass slide, labelled “ Alona kolwezii holotype ”; deposited at Royal Belgian Institute for Natural Sciences , Brussels ( RBIN) under accession number IG 30.556 . Paratypes, five slides, with fully or partially dissected females, labelled “ A. kolwezii paratypes ”, RBIN accession number IG 30.556 . Sample with adult females in ethanol (70%) in glass tube, with same data as holotype, under same accession number. Type locality. Mulungwishi stream (10°37’00” S, 26°42’00” E), close to Lulua River, vicinity Lufupa, Katanga Region, SE of DR-Congo, Leg. K. Martens, 14.10.1981, picked from sample 81.067 at UG Zooplankton Collection, Ghent University , Department of Biology , Limnology Research Group .

Additional material. Four adult parthenogenetic females, stagnant pond next to stream with clay bottom, devoid of aquatic plants, between Lubondo and Kolwezi, Lualaba River Basin, Katanga region, DR-Congo, 06.10.1981, Leg. K. Martens, sample 81.015 (labelled “pond CPA, Zaire-Kolwezi”). Specimens in UG Zooplankton Collection .

Etymology. Named after the city of Kolwezi in DR Congo, Katanga Region, near the Lualaba River and situated equidistant from both localities of the new species. Sample series collected by Dr. K. Martens from which this species derives, are originally labelled as “Zaire-Kolwezi”.

Description of adult parthenogenetic female. Habitus. Medium-sized animals ( Figs 6A–C; 0.50– 0.60mm), colour in life unknown. In lateral view carapace rectangular, posterodorsal angle not pronounced and posterior margin relatively straight ( Figs 6A–C). Posteroventral corner with shallow notch ( Fig. 6A). Head. Eye larger than ocellus ( Fig. 6A). Rostrum blunt, aesthetascs projecting beyond it ( Fig. 6A). Three main head pores of same size with narrow connection between them, small pores more than half distance between midline and lateral margin of head pores ( Fig. 6F). Carapace. Ornamentation not pronounced, large striation present. Marginal setae in different size groups, longest group on frontal margin of carapace and just before middle ( Fig. 6A). Posteroventral corner with row of 55–60 setae ending abruptly towards posteroventral corner and followed by small spiniform setae ( Fig. 6I). Head. Eye larger than ocellus ( Fig. 6A). Rostrum blunt, aesthetascs projecting beyond it ( Fig. 6A). Three main head pores of same size with narrow connection between them, small pores more than half distance between midline and lateral margin of head pores ( Fig. 6F). Antennules ( Fig. 6F). About three times as long as wide, sensory seta implanted between one third and half from base of antennule. Rows of setules on dorsal margin. One aesthetasc longer than others. Antennae ( Fig. 6G). Coxal setae long. Exopod with group of smaller spines on second segment. Setae: 113/003, spines: 001/101 (structures on exo/endopod) Terminal setae subequal in length. First endopod spine just shorter than penultimate endopod segment, apical spines longer than ultimate segments; first exopod seta not reaching apex of third exopodal segment. Labrum ( Figs 6D–E). Lacking lateral projections, labral keel with convex margin, small to large ventral notch and two to three (one minute) ventral groups of setules; also two lateral groups of setules present.

Postabdomen ( Figs 6J–L). Moderate, with parallel dorsal and ventral margins, not expanded in postanal portion. Postanal portion expanded, postanal margin less than twice as long as anal margin. Postanal angle about 90°. Postanal marginal teeth 10–11, long pyramidal, serrated on the anterior margin. Lateral fascicles with setules decreasing in size anteriorly; posteriormost thicker and larger than others of its group and reaching half its length beyond the dorsal margin of the postabdomen, to the apex of the marginal teeth (posterior groups; Fig. 6L). Terminal claw ( Fig. 6K). Relatively long and slender, about as long as anal margin ( Fig. 6J) and slightly curved. Basal spine ( Fig. 6K), more than two times claw width and less than half of claw length. Row of basal spinules along the dorsal half of the terminal claw, no strong spines.

Five pairs of limbs. First limb ( Figs 7A–D). First endite with three setae, the first seta well developed and plumose ( Fig. 7A). Anterior soft seta present, small ( Figs 7A–B). Second endite with three setae, first two with small pecten. One anterior soft seta present and an additional minute element near its base ( Figs 7A–B). Third endite with four setae, similar in length ( Fig. 7A). IDL ( Fig. 7C) with three setae, of which one smaller and naked, two larger, subequal, unilaterally armed with fine denticles in the distal half. IDL with three setae, ODL ( Fig. 7C) with one single, long seta, implanted on one side with minute denticles in distal half. At base of ODL, a projection. Accessory seta on sixth endite strongly developed and plumose, about as long as ODL seta ( Fig. 7C). Setule rows on anterior and ventral part of limb corm ( Fig. 7D set) consisting of 15–17 long singular setules, two ventralmost groups with two setules. Ejector hooks well-developed, subequal in size ( Figs 7A). Gnathobase I with short setulated process ( Fig. 7A). Second limb ( Figs 7E–I). Exopodite well developed with setulated seta implanted subapically and of about same length as exopodite itself and group of fine setules ( Figs 7E–F); exopodite seta half the size of first scraper ( Fig. 7E). Endites with eight scrapers, first three long, following five gradually decreasing in size towards gnathobase while increasing in thickness ( Fig. 7E). Denticulation of scrapers is fine, last three with relatively thicker denticles ( Fig. 7E). Additional small soft seta at the inner base of the first scraper ( Figs 7H–I) and minute sensillum at base of third scraper ( Fig. 7H). Gnathobasic hillock not expanded, with fine setules. Small sensillum close to gnathobasic setae. Gnathobase typically with three elements, of which the first bears a bent seta, second a thick seta, third small and naked. Filter comb ( Fig. 7G) with seven setae, of which the first three shorter. First filter seta ( Fig. 7G) shortest, thicker, with long setules in distal half, implanted on all sides. Third limb ( Figs 7J–O). Epipodite ovalround, without projections. Exopodite ( Figs 7J–L) with seven setae, of which two on posterior and five on ventral margin. First two exopodite setae long, first shorter than second ( Fig. 7J). Third exopodite seta longest, about four times the length of the exopodite itself, following two short setae of similar size (4–5 in Fig. 7L); sixth and seventh setae relatively narrow, fifth longest; all exopodite setae plumose, except for sixth (heterogenous setulation) ( Fig. 7K). Endite ( Fig. 7M) with typical alonine arrangement: close to the exopodite, a row of three well-developed setae, of which the first are unilaterally armed with short denticles in the distal half and have a small reduced seta in between, and a third, thicker seta with fine long setules (1”–3” in Fig. 7M). Between the latter row and the gnathobase, five naked setae, of which the first is most reduced ( Fig. 7O). The gnathobase ( Fig. 7N) consists of a subapical large bottle shaped sensillum, a group of setules, and three apical gnathobasic setae: one large seta, bent over the endopodite and implanted with fine setules, and two smaller straight setae, lacking larger setulation. On the inner side of the endite ( Fig. 7M), four similar plumose (1”–4”) setae. Filter comb s strongly developed, consisting of seven long setae with fine plumose setulation ( Fig. 7M). Fourth limb ( Fig. 7P). Pre-epipodite round, implanted with long marginal setules and larger than the oval-round epipodite. Exopodite ( Fig. 7P) square and large, bearing six setae of which first four strongly plumose and similar in morphology, opposed to the last two (5–6 in Fig. 7P), which are much narrower and smaller, implanted with short setules. At dorsal base of third exopodite seta, a small naked, oval-round process, between third and fourth scraper a setulated hillock ( Fig. 7P). Anteroventral margin of exopodite straight and implanted with row of small setules on its margin. Endopodite ( Fig. 7P) with four developed marginal setae, of which first scraper-like; the following three long “flaming torch” setae (1”–4”). Between scraper and first ft-seta, a minute reduced element. Towards gnathobase, adjacent to last ft-seta, a round naked seta ("s" in Fig. 7P). Gnathobase with one large seta, and two smaller basal naked reduced elements, one spiniform. On the inner side, a row of three long plumose setae (1”–3” in Fig. 7P) on a separate endite, is followed by five slender filter comb setae with fine setulation. Fifth limb ( Figs 7Q–R). Pre-epipodite and epipodite oval-round and of similar size, pre-epipodite with long setules. Exopodite a large flap ( Fig. 7Q), with incision and convex margin in ventral middle. Four plumose setae in a 3+1 arrangement, first three setae long, oriented dorsally, fourth seta very short (less than a fourth of the third seta). Between third and fourth seta, the exopodite margin is implanted with long setules, largest group in ventral half. Ventral portion of the exopodite widely round. Inner lobe large, with slightly convex dorsal margin, bearing thick long setules on its ventral margin ( Fig. 7Q). Two inner setae long (1’–2’ in Fig. 7Q), first one bent over the inner lobe, second (2’) half the proceeding seta (1’), both with long setules. Gnathobase reduced, two naked elements (reduced setae?) and a setulated process ( Figs 7Q–R). Sixth limb absent.

Male and gamogenetic female. Unknown.

Distribution. A. kolwezii n.sp. is now only known from samples from South Congo in two different localities in the Katanga region. Both are located east and west of the Lualaba River, the largest headstream of the Congo River. It is likely that the species has a wider distribution in the Congo Basin, its further occurrence in the Afrotropical region remains unknown.

Ecology. Found in bottom samples from a stream environment or stagnant pool connected to stream, with leaf litter, sandy and clay substrate. Sympatric with Macrothrix sp. , Alona mediterranea and two undescribed species of the A. verrucosa - (see Sinev & Hollwedel 2005) and A. affinis -groups (see Sinev, 1997).

Remarks. A. kolwezii is closer in morphology to A. boliviana than to A. quadrangularis in having more than ten long setules on the anterior margin of the P1, a short seta on exopodite II, a postabdomen with straight dorso-distal margin, relatively shorter terminal claw or basal spine. The new species differs from A. boliviana by a smaller body size (0.5-0.6mm), a low posterodorsal angle (unlike quadrangularis or boliviana , body is actually relatively arched in kolwezii with a more affinis- like habitus), second antennae with group of fine spinules on the exopod, no strong spines; on postabdomen, the longest spines of lateral fascicles reach the apex of marginal teeth; P1 with more than 14 setules on the anterior margin. We refer to Table 1 for additional differences between the three species.