Anthalona harti occidentalis, DAMME, KAY VAN, SINEV, ARTEM YU & DUMONT, HENRI J., 2011
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publication ID |
https://doi.org/ 10.11646/zootaxa.2875.1.1 |
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persistent identifier |
https://treatment.plazi.org/id/0390471D-FFEE-1836-FF22-D3E56E2EC9B6 |
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treatment provided by |
Felipe |
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scientific name |
Anthalona harti occidentalis |
| status |
subsp. nov. |
Anthalona harti occidentalis n.ssp.
( Figs 10–11 View FIGURE 10 View FIGURE 11 )
Alona verrucosa in Dumont et al. (1981)
Alona cf. verrucosa in Chiambeng et al. (2006: Fig. 5 View FIGURE 5 )
Material examined. Holotype. One adult parthenogenetic female mounted in glass slide labelled “ Anthalona harti occidentalis n. ssp. holotype ”; from Lake Télé, Mali, 29.II.1976; sample 02.206; Sahara Expedition II, sample 144 in UG Collection, Leg. H.J. Dumont.
Paratypes. One slide with one complete female labelled “ Anthalona harti occidentalis n. ssp. paratype ” same data as holotype and one slide with one dissected female. Tube containing three females in ethanol from type locality. All material deposited at Royal Belgian Institute for Natural Sciences , Brussels ( RBIN) under accession number RBIN IG 31782 INV 96717 (holotype) , INV 96718 - 96719 and INV 96722 (paratypes).
Additional material. two adult parthenogenetic females from Yoke River Dam, Muyuka, along the road to Kumba, Cameroon, Leg. G.Y. Chiambeng, 25.VII.2000, one of these specimens deposited under RBIN IG 31782 INV 96720 .
Description. parthenogenetic female. Habitus ( Figs 10A–C View FIGURE 10 ). 0.3–0.310 mm. Length of body 1.5–1.6 times as long as wide. Colourless, transparent. Dorsum moderately convex, highest point in middle; posterior margin expanded in lower (ventral) portion ( Fig. 10A View FIGURE 10 ). Angle of posterior margin with imaginary ventro-dorsal axis through posterodorsal corner is 15–20°. Maximal posterior point situated in ventral quarter of body. Maximal ventral extent of rostral tip not reaching ventral maximum of carapace margin ( Fig. 10B View FIGURE 10 ). Ventral carapace margin straight to slightly deeper near middle. Posteroventral corner round ( Fig. 10E View FIGURE 10 ), may have shallow notch.
Head. Ocellus smaller than eye, diameter latter about 1.6 times the ocellus. Well-developed rostrum, broad and obtuse as in A. harti harti . Aesthetascs of antennules projecting laterally from rostrum, antennule itself shorter than rostrum ( Fig. 10C View FIGURE 10 ). Two main head pores ( Fig. 10D View FIGURE 10 ) relatively large, connected. Chitin ring connecting head pores round. Interpore (IP) distance about one time the diameter of a main pore ( Fig. 10D View FIGURE 10 ). PP distance about one IP distance, lateral pores at two IP distance from midline. These lateral pores are situated just anterior to anterior pore, but never far, maximally one IP distance ( Fig. 10D View FIGURE 10 ). Sacks under small pores with diameter about two times that of a main pore. These sacks divided, eight-shaped ( Fig. 10D View FIGURE 10 ).
Carapace ( Fig. 10B View FIGURE 10 ). Tubercles rare, mostly striation or no ornamentation. Marginal setae 22–30, differentiated into three groups. Anterior group longest than posterior group, median group shortest. Posterior setae followed by fine setules ( Fig. 10E View FIGURE 10 ). These setules of similar size, reaching beyond carapace margin in posteroventral corner and continuing in a posterior row of fine long setules ( Fig. 10E View FIGURE 10 ).
Labrum ( Fig. 10F View FIGURE 10 ). Labral keel with convex margin and obtuse tip. Strong, single proximal denticle on labral keel.
Antennules. About 2.5 to three times as long as wide, sensory seta implanted at one third from apex. Aesthetascs not studied.
Second antennae ( Fig. 10G View FIGURE 10 ) with first exopod seta on antenna narrow ( Fig. 10G View FIGURE 10 ), just longer than apical exopod segment; second exopod seta twice as long as first. True spine on first endopod segment reaching just beyond tip of second segment; main terminal spines on endo- and exopod well developed, longer than their apical segments (about 1.3 times its length). Terminal setae on antennal exopod as for endopod and with long setules. These swimming setae longer than body, reaching beyond dorsum ( Fig. 10C View FIGURE 10 ).
Postabdomen ( Fig. 10H View FIGURE 10 ). Relatively widest at preanal angle and with round dorso-distal margin. About two to 2.5 times as long as wide. Ventral margin shorter than anal and postanal margins together. Anal margin as long as postanal margin, both shorter than preanal margin. Anal margin slightly concave, postanal margin convex. Distal embayment shallow, about half as deep as claw width at base. Preanal corner not protruding beyond maximal dorsal point of postanal margin. Five to six marginal postanal teeth. Each distal marginal tooth with four to five adjacent smaller spines on its anterior side, partly merged. These marginal teeth about two times as long as wide (at base). Lateral setae arranged in fascicles ( Fig. 10H View FIGURE 10 ), five groups in postanal portion, consisting of six to seven elements in each group, parallel to each other. Distalmost lateral spiniform element thicker and longer; in the two distalmost groups, protruding half of its length beyond dorsal margin of postabdomen. Most distal lateral elements per fascicle in postanal portion ( Fig. 10J View FIGURE 10 ) reaching beyond apex of marginal teeth. Smaller elements per fascicle shorter in length than distal (largest) element by about half ( Fig. 10J View FIGURE 10 ). Two to three marginal clusters and four to five lateral fascicles in anal portion. Preanal corner bears no marginal teeth ( Fig. 10H View FIGURE 10 ).
Terminal claw ( Figs 10H–I View FIGURE 10 ). As long as or just longer than anal margin, implanted with setules along dorsal side. Proximal pecten ending in stronger spine up to two thirds as long as width of claw at this point and implanted just before half of claw length. Basal spine ( Fig. 10I View FIGURE 10 ) strong, less than claw thickness at base and reaching about a fifth of claw length. Group of three to four basal spinules, not reaching up to half of basal spine length ( Fig.10I View FIGURE 10 ).
Five pairs of limbs. First limb ( Figs 11A–C View FIGURE 11 ). Epipodite round with projection reaching beyond limb margin ( Fig. 11A View FIGURE 11 ). First to third endites as for genus. Longest seta in second endite with ten to eleven teeth ( Fig. 11A View FIGURE 11 ); shortest seta in the same endite about one third of previous seta. Anterior elements well developed for genus, longer than wide ( Fig. 11C View FIGURE 11 ). ODL with one slender seta, just longer than largest IDL seta and with short fine setules in distal half ( Figs 11B View FIGURE 11 ); two setae in IDL, modified. On largest IDL seta, one large spine followed by reduced distal part ( Fig. 11B View FIGURE 11 ); this spine in longest IDL seta longer than distal part beyond it ( Fig. 11B View FIGURE 11 ). On shortest IDL seta, two long spines of which second is largest and longer than distal part of this seta ( Fig. 11B View FIGURE 11 ). Anterior setule groups ( Fig. 11A View FIGURE 11 ) with seven to ten setules in each group, decreasing in size ventrally (first three groups long). Ejector
Second limb ( Figs 11D–E View FIGURE 11 ). Exopodite ( Fig. 11D View FIGURE 11 , ex) elongate, twice as long as wide, with short seta reaching just exopodite apex; denticles on exopodite apex; endites with eight scrapers decreasing in size towards gnathobase, eighth scraper shortest ( Fig. 11D View FIGURE 11 ). First two scrapers relatively slender and finely setulated, first longest. Third scraper ( Fig. 11F View FIGURE 11 ) markedly shorter, modified with stronger teeth, smaller than scrapers two and four. Scraper four with reduced seta near base ( Fig. 11F View FIGURE 11 , arrow). Scrapers four and five similar, with fine denticles ( Fig.11D View FIGURE 11 ), scraper six ( Fig. 11E View FIGURE 11 ) shorter by a third of previous and with seven strong teeth; final two scrapers ( Fig. 11D View FIGURE 11 ) decreasing in size towards gnathobase, scraper eight thick and with longest denticles. Gnathobasic ‘brush’ short and round, with short denticles. Gnathobase ( Fig. 11D View FIGURE 11 , gn) as for genus; filter comb ( Fig. 11D View FIGURE 11 ) with seven setae of which first two shorter, third about as long as previous two.
Third limb ( Figs 11G–H View FIGURE 11 ). Epipodite round with projection, reaching over margin of exopodite; exopodite shape ( Fig.11H View FIGURE 11 ) square, with six setae as for genus; first exopodite seta shorter than second, not thicker; third exopodite seta 1.7 length of fifth exopodite seta, fourth seta 0.6 times fifth seta and about two times as long as sixth seta. So, fifth seta is much longer than fourth seta in third exopodite (1.6 its length) ( Fig. 11H View FIGURE 11 ). Endite ( Figs 11J–I View FIGURE 11 ) as for genus, filter comb setae twice as long as last seta on inner side (4”).
Fourth limb ( Fig. 11K View FIGURE 11 ). Epipodite oval with long projection reaching beyond margin. Exopodite with six marginal plumose setae; first three exopodite setae longer than last three and of similar size; fourth seta 0.7 length of preceding seta; fifth and sixth setae narrower than previous. Both these setae of the same lengths as fifth Endite as for genus.
Fifth limb ( Fig. 11L View FIGURE 11 ). Epipodite oval with long projection, reaching almost half its length over margin of exopodite. Exopodite shape broadly oval, about two times as long as wide, with straight margin between setae three and four; four exopodite setae, first (dorsal) two longest, oriented dorsally, first about 1.4 times exopodite width; third shorter than second exopodite seta (0.7 times its length), fourth exopodite seta 0.4 times length of preceding seta; inner portion of limb (Fig.) with broad oval inner lobe and long apical setules; two endite setae (1’–2’) of which first longer; though not reaching beyond apex of inner lobe; second about 0.8 times as long as seta 1’. Gnathobase as for genus.
Differential diagnosis. Anthalona harti occidentalis n.ssp. is very close to A. harti harti , but in second antenna, the first endopod spine is much longer than second segment (in h. harti it is of similar size). This West African subspecies has broad longitudinal or no striation on the carapace and a ventral portion of the valves that is expanded posteriorly. Head pores closer to each other than in A. harti harti , and distal lateral fascicles on postabdomen reach beyond marginal teeth in postabdomen. The second limb has strongest modified scrapers of all Anthalona , sixth scraper thick with seven teeth and all limbs with long epipodites reaching over the limb margins; P4ex setae four to six are of similar lengths in A. harti occidentalis , which is not the case in A. harti harti .
Distribution and ecology. West African subspecies, in plankton samples from Lake Télé, Mali and in a river sample from Cameroon.
Remark. We prefer to keep occidentalis and harti as two subspecies here, because the differences are small and our knowledge of distribution and variability in the West African subspecies is limited because of a low number of specimens. In future, these may well be regarded as two different species.
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