Anthalona harti harti, DAMME, KAY VAN, SINEV, ARTEM YU & DUMONT, HENRI J., 2011

DAMME, KAY VAN, SINEV, ARTEM YU & DUMONT, HENRI J., 2011, Separation of Anthalona gen. n. from Alona Baird, 1843 (Branchiopoda: Cladocera: Anomopoda): morphology and evolution of scraping stenothermic alonines, Zootaxa 2875 (1), pp. 1-64 : 18-22

Anthalona harti harti n.ssp.

( Figs 8–9 )

Alona verrucosa Sars, 1901 in Alonso (1996: fig. 141)

(?) Alona verrucosa Sars, 1901 sensu Jenkin (1934 : fig. 18); Rey & St-Jean (1968: fig. 26); Harding (1957: figs 20–28);? Alona alonopsiformis Brehm, 1933 sensu Dumont et al. 1984 ( Fig. 1 in Dumont et al. 1984)

Etymology. Named in honor of Dr Rob Hart, professor at the Department of Zoology and Entomology, University of Natal, Pietermaritzburg, limnologist and specialist of South African Cladocera . Dr. Hart was with H.J. Dumont in the field during the survey of the Okavango, from which samples this African species is described.

Material examined. Holotype. Single adult parthenogenetic female in slide labeled “ Anthalona harti harti n. sp. holotype ” from Maun, Botswana, Thalamakani River, 19.VII.2006, Leg. H.J. Dumont. Accession number RBIN 31782, INV 96706 . Paratypes. Six slides with four dissections, one with one complete and one with two complete parthenogenetic females. Accession numbers RBIN 31782, INV 96707 - 12. One tube with seven adult parthenogenetic females in ethanol, complete, from type locality, accession number RBIN 31782, INV 96716 .

Additional material. Two dissected and one complete adult parthenogenetic females, Moremi, Chiefs Island , Hippograss, Okavango, 20.7.2006, Leg. H.J. Dumont, UG Collection, Accession Number RBIN 31782, INV 96713-15. Adult parthenogenetic females from Georgia, Abkhazia, ponds of Tzitrusovyi collective farm, coll N.N. Smirnov, no date, kept at MGU .

Description. Parthenogenetic female. Habitus. ( Figs 8A–B ). 0.3–0.34 mm. Length of body 1.45–1.5 times as long as wide. Colourless and transparent. Dorsum convex, highest point at middle; posterior margin expanded in lower (ventral) portion ( Fig. 8B ). Angle of posterior margin with imaginary ventro-dorsal axis through posterodorsal corner is 15–20°. Maximal posterior point situated in ventral quarter of body ( Fig. 8B ). Maximal ventral extent of rostral tip reaching ventral maximum of carapace margin ( Fig. 8B ). Ventral carapace margin straight. Posteroventral corner round, without notch ( Fig. 8E ), sometimes faint notch present.

Head. Ocellus smaller than eye (latter about 1.3 times larger). Well developed rostrum, broad and obtuse ( Fig. 8D ). Aesthetascs of antennules projecting laterally from rostrum, antennule shorter than rostrum ( Fig. 8F ). Head shield narrow with fornix not strongly developed ( Fig. 8D ). Two main head pores ( Fig. 8C ) relatively large, connected. Chitinous ring connecting head pores rounded and main pores relatively large ( Fig. 8D ). Interpore (IP) distance twice the diameter of one main pore ( Fig. 8C ). PP distance short, one third to half of IP distance, lateral pores at one IP distance from midline ( Fig. 8D ). These lateral pores are situated parallel to anterior pore or just anterior from it, but never far, maximally half IP distance. Sacks under small pores with diameter 1.5-two times that of a main pore ( Fig. 8C ). These sacks divided two times and eight-shaped ( Fig. 8C ). Posterior margin of head shield rounded(!), not subdivided.

Carapace ( Figs 8A–B ). Ornamentation with broad striation ( Fig. 8B ), sometimes with faint tubercles. Few specimens with fine striation as in A. mediterranea . Marginal setae 30–45, differentiated into three groups. Anterior group longer than posterior group, median group shortest. Posterior setae followed by fine setules ( Fig. 8E ). These setules of similar size, reaching beyond carapace margin in posteroventral corner and continuing in a posterior row of fine long setules ( Fig. 8E ).

Labrum ( Fig. 8H ). Labral keel with straight to convex margin and obtuse ventral tip. Strong, single proximal denticle on labral keel, bent downwards ( Fig. 8H ).

First antennae or antennules ( Fig. 8F ). About two–2.5 times as long as wide, sensory seta implanted at one third from apex. Aesthetascs of similar size, half length of antennule; the inner aesthetasc of each antennule longer than the others by one third to a fourth.

Second antennae ( Fig. 8G ). Basal spine short. Antennal formula as for genus. First exopod seta on antenna narrow ( Fig. 8G ), may reach ultimate exopod segment; second exopod seta less than two times as long as first. True spine on first endopod segment not reaching beyond tip of second segment; main terminal spines on endo- and exopod well developed ( Fig. 8G ). Endopod apical spine as long as apical segment, exopod spine a third longer than its segment. Terminal setae on antennal exopod as for endopod and with long setules. These swimming setae are longer than body, reaching beyond dorsum ( Fig. 8A ).

Postabdomen ( Figs 8I–J ). Relatively widest at preanal angle and with rounded dorso-distal margin ( Fig. 8I ). About two to 2.5 times as long as wide. Ventral margin shorter than anal and postanal margins together. Anal margin longer than postanal margin as long as preanal margin ( Fig. 8I ). Anal margin slightly concave, postanal margin forming a straight line between anal margin and distal angle of postabdomen. This postanal margin forms an angle of about 25° with an imaginary dorsal axis connecting preanal corner with dorsalmost point of postanal margin. Distal embayment (dorsal to basal claw) about as deep as length of claw width at base ( Fig. 8I ). Preanal corner well developed, may protrude just beyond maximal dorsal point of postanal margin. Five marginal postanal teeth ( Fig. 8I ). Each distal marginal tooth with four to five adjacent smaller elements on its anterior side, partly merged. These marginal teeth rather long, about twice as long as wide (at base). Lateral setae in four to five fascicles in postanal portion, consisting of six to eight elements in each group, parallel to each other ( Figs 8I–J ). Distalmost lateral spine thicker; in the two distalmost groups, protruding one third of its length beyond dorsal margin of postabdomen ( Fig. 8L ). Distalmost lateral spiniform elements per fascicle in postanal portion reach apex of marginal teeth or beyond, but do not extend by half their length beyond the latter ( Fig. 8L ). Smaller elements per fascicle decrease in length, but are longer than half of the distalmost (and largest) element in each group ( Fig. 8L ). Three to four clusters of long marginal teeth, and four to five lateral fascicles in anal portion. Preanal corner rarely bears teeth ( Figs 8I–J ).

Terminal claw ( Figs 8I–K ). As long as or just longer than anal margin ( Fig. 8I ), implanted with setules along dorsal side. Proximal pecten ending with spine up to two thirds as long as width of claw at this point and implanted just before half of claw length ( Fig. 8I ). Basal spine ( Fig. 8K ) strong, about as long as claw thickness at base and reaching up to one fourth of claw length. Group of two to three long basal spinules, reaching up to half of basal spine length ( Fig. 8K ).

First maxilla ( Fig. 9K ) as for genus.

Five pairs of limbs. First limb ( Figs 9A–C ). Epipodite round with long projection ( Fig. 9A ), but not reaching beyond limb margin. First to third endites as for genus. Longest seta in second endite with seven to nine teeth ( Fig. 9A ); shortest seta in the same endite is between half and one third of previous seta. Anterior elements ( Fig. 9B ) well developed, longer than wide. ODL ( Fig. 9C ) with one slender seta, just longer than largest IDL seta and with short fine setules in distal half ( Fig. 9C ); two setae in IDL ( Fig. 9C ), modified. On largest IDL seta, one large spine followed by reduced distal part ( Fig. 9C ); this spine in longest IDL seta is longer than distal part beyond it. On shortest IDL seta ( Fig. 9C ), two long spines of similar size and longer than distal part of this seta. A third element present in IDL, remnant of a third seta. Accessory seta present, two-thirds the size of ODL seta ( Fig. 9C ). Anterior setule groups ( Fig. 9A ) with five to seven setules in each group, decreasing in size ventrally. Ejector hooks ( Fig. 9A ) unequal, anterior one about half as long and thick as posterior one.

Second limb ( Figs 9D–E ). Exopodite ( Fig. 9D , ex) elongate, two times as long as wide, with short seta reaching just beyond exopodite apex; two rows of denticles on exopodite apex; endites with eight scrapers decreasing in size towards gnathobase, eighth scraper shortest ( Fig. 9D ). Soft seta present near base of first scraper ( Fig. 9D , ss). First two scrapers relatively slender and finely setulated, first longest. Third scraper markedly shorter, modified with stronger teeth, and smaller than scrapers two and four. Scrapers four and five ( Fig. 9D ) similar, with fine denticles, scraper six ( Fig. 9E ) shorter by a third and with six to seven stronger teeth; final two scrapers decreasing in size towards gnathobase, scraper eight thick, with longest denticles. Gnathobasic ‘brush’ short and round, implanted with short denticles. Gnathobase as for genus; filter comb ( Fig. 9D ) with seven setae of which first two shorter, third intermediate between these two and fourth filter seta.

Third limb ( Figs 9F–K ). Epipodite round with projection, not reaching centre of exopodite; exopodite shape ( Fig. 9G ) square, with six setae as for genus; first exopodite seta one third longer than second, not thicker; third exopodite seta twice as long as fifth exopodite seta, fourth seta 0.6 times fifth seta and about two times as long as sixth seta ( Fig. 9K ). So, fifth seta is much longer than fourth seta in third exopodite (1.6 its length) ( Fig. 9K ). Endite ( Figs 9H–J ) as for genus and with strongly developed denticles in setae 1’–2’ ( Fig. 9H ), setae in internal endite preceding gnathobase increasing towards gnathobase ( Fig. 9I ), filter comb setae twice as long as last seta on inner side (4”) ( Fig. 9H ).

Fourth limb ( Figs 9L–N ). Epipodite oval with long projection ( Fig. 9L ). Variable in size, from reaching centre of exopodite up to almost the exopodite margin, but never beyond. Exopodite ( Fig. 9L ) with six marginal plumose setae; first three exopodite setae longer than last three and of similar size (third is longer just by a tenth of second seta), fourth seta 0.6 length of preceding seta ( Fig. 9M ); fifth and sixth setae narrower than previous. Both these setae of different lengths: fifth longest ( Fig. 9M ), about 1.4 times of length fourth or sixth. Endite ( Fig. 9N ) as for genus.

between setae three and four; four exopodite setae, first (dorsal) two longest, oriented dorsally, as long as exopodite width; third shorter than second exopodite seta (0.9 times its length), fourth exopodite seta 0.6 times length of preceding seta; inner portion of limb with broad oval inner lobe and long apical setules; two endite setae (1’–2’) of which first longer; this seta reaching beyond apex of inner lobe; second endite seta about 0.9 times as long as 1’. Gnathobase as for genus.

Adult male. We did not encounter males of this species. As described in Alonso (1996: Fig. 141), the male is maximally 0.23mm long, dimensions length/height about 1.7 with straight dorsum, postabdomen with well developed preanal corner and long lateral fascicles (distal spines in the three distalmost groups reaching over the margin by half their lengths). Basal spine relatively long, one third of terminal claw.

Ephippial female unknown.

Differential diagnosis. The African Anthalona harti is very similar to A. verrucosa and belongs to the same complex. We distinguish two subspecies, the second is decribed below. A. harti harti has distal lateral fascicles that do not reach beyond the marginal teeth as in A. verrucosa (or A. harti occidentalis ) and a basal spine on its terminal claw that is relatively short (as long as or shorter than the claw width at base). A. harti harti has longitudinal (rarely fine or rarely verrucae) striation on the carapace and a ventral portion of the valves that is expanded posteriorly. The postabdomen shape (in postanal part) is more angular than round, which sets it apart from the other taxa. The main distal spine of each lateral fascicle is short, not two times as long as the adjacent fascicles as in A. harti occidentalis . Main head pores large and situated about two pore diameters from each other, in comparison to the West African subspecies, where pores are just one diameter apart. A. harti differs from A. mediterranea in having a single denticle on the labrum and an expanded posteroventral carapace margin. The denticle on the labrum is oriented down in both A. harti subspecies, not straight forward (see also the key). Two important and undeniable character on the limbs for A. harti are: 1) the long fifth seta on the third limb (1.6 times fourth seta) and 2) second limb with sixth scraper with six to seven strong denticles (mostly more in other species).

Distribution and ecology. Okavango, South Africa, distribution most likely extends to East Africa and Mediterranean. We found one population from the Mediterranean Black Sea coast that can be positively identified as A. harti harti (Georgia) , and we can identify specimens figured in Alonso (1996: 141) from a single locality in Spain (Valdecaballeros, Badajoz) as this species as well. They have a clear downward denticle on the labrum, a sixth scraper with seven large teeth and identical head pores to the South African populations. Records in between, from Eastern Africa, should be rechecked, but from the figures, specimens found in the African Rift, depicted in Jenkin (1934; Lake Naivasha, Kenya), by Rey & St-Jean (1968; Chad) and from Harding (1957; Tanzania) all correspond in characters to A. harti n. sp. and most likely to subspecies A. harti harti n.ssp. Not much known about ecology. Populations on which our description was based, originate from pools and swamps of the Okavango river delta, rich in vegetation and cladoceran faunas. Alonso (1996) mentions abundant vegetation in permanent, clear waters with low conductivities for the Spanish population. In any case, these animals seem quite abundant chydorids for African freshwater bodies and floodplains and can be considered widespread and common.

Figures

FIGURE 1. Anthalona acuta n. sp. Parthenogenetic females from temporary dune pools at the Lençóis Maranhenses, Brazil. A. Habitus. B. Idem. C. General body outline. D. Front of head. E. Labral keel, lateral view. F. First antenna. G. Second

FIGURE 8. Alona harti harti ssp.n. from Southern Africa. Parthenogenetic females from Thalamakani River, Okavango Delta, Botswana. A. Habitus, lateral view. B. Idem, body outline. C. Head pores. D. Head shield. E. Posteroventral valve corner. F.

FIGURE 9. Alona harti harti ssp.n. from Southern Africa. Parthenogenetic females from Thalamakani River, Okavango Delta, Botswana. A. First limb, anterior view (ODL and IDL omitted). B. Idem, anterior view to show soft setae. C. Idem, IDL, ODL and accessory seta. D. Second limb. E. Idem, scraper six. F. Third limb, exopodite. G. Idem, setules omitted. H. Idem, endo-