Anthalona mediterranea ( Yalim, 2005 ), 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: 26-32
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|Anthalona mediterranea ( Yalim, 2005 )|
( Figs. 12–15)
Material examined. Numerous specimens, both males and females, from permanent rockpool at Homhill Plateau at top of Mukhadrion Pass, 7.II.1999, Loc. 6A, Socotra Island ( Yemen), Leg. K. Van Damme; Eight specimens from Wadi Zerik, Diksam Plateau, 23.II.1999, Socotra Island ( Yemen), Leg. K. Van Damme; Numerous specimens from temporary rockpool in Wadi Shawqah, Sharjah, United Arab Emirates, 23.II.2005 & 20.III.2006, Leg. K. Van Damme. Specimens raised from dried mud from Wadi Shawqah , Sharjah, UAE (taken 20.III.2006), Leg. K. Van
Damme. All slides and complete animals in tubes, deposited under RBIN IG 31782 INV 96723 View Materials -36.
Socotra, animals were much up to 0.55mm. Colour in life pale yellow-orange to light brown. This colour remains in shedded valves. Body length 1.5–1.56 times height ( Figs 12A,C). Dorsum moderately convex, highest point near middle; posterior margin straight to convex, not expanded in lower portion ( Fig. 12C, 13A). Faint dorsal keel in dorsal view ( Fig. 13B). Maximal ventral extent of rostral tip not reaching ventral maximum of carapace margin ( Fig. 12C). Marginal setae 54–65, anterior group may be very long, but posterior group not strongly different. Ventral carapace margin straight to moderately convex with point just before middle. Posteroventral corner round, with small notch ( Fig.12B).
Head. Ocellus and eye of same size, ocellus may even be larger ( Fig. 12A). Rostrum well developed, broad and obtuse ( Fig. 12D). Aesthetascs of antennules projecting laterally from rostrum, antennule just shorter ( Fig. 12A) or as long as rostrum ( Fig. 12B). Two main head pores ( Fig. 12E, 13D) relatively small, connected. Chitin ring connecting head pores squarer than rounded at anterior and posterior ends. Interpore distances three to four times the diameter of one main pore ( Fig. 12E). PP distance long, about one IP distance, lateral pores at two IP distance from midline and situated posterior to main pores ( Fig. 13D), at one IP distance from posterior pore. Sacks under small pores with diameter four to five times that of a main pore ( Fig. 12E). These sacks divided more than two times, more cauliflower than eight shaped ( Fig. 12E).
Carapace ( Figs 12A–B, 13A–B). With fine striation ( Figs 13A–B), sometimes with faint tubercles. Marginal setae 42–56, differentiated into two groups, anterior group long, median and posterior group shorter by half, posterior setae little longer than median setae. Setae not strongly decreasing in size towards the posteroventral corner but ending more abruptly and followed by fine setules. These setules of similar size, reaching beyond carapace margin in posteroventral corner and continuing in a posterior row of fine long setules.
Labrum ( Fig. 12G). Labral keel shaped as for genus, but with rather convex to wavy margin and an obtuse tip. No proximal denticle on labral keel but sparse group of minute setules here ( Fig. 12G).
First antennae or antennules ( Fig. 12H). About two–2.5 times as long as wide, sensory seta implanted between half and one third of antennular corm from apex. Aesthetascs of similar size, half the length of antennule, two longer by a third compared to the shorter aesthetascs.
Second antennae ( Fig. 12F, 13A). Basal spine minute. Formula as for genus. First exopod seta ( Fig. 12F) not reaching beyond ultimate exopod segment; second exopod seta three times as long as previous. Groups of fine spinules on first and second exopod segments not strongly thickened (vs. A. verrucosa ). True spine on first endopod segment not reaching beyond end of second segment ( Fig. 12F); main terminal spines on endo- and exopod well developed, each as long as their apical segment, exopod spine may be shorter ( Figs 12F, 13A). Terminal setae on antennal exopod as for endopod and with long setules. These swimming setae are relatively short in relation to body, not (or just) reaching beyond dorsum ( Figs 12A–B).
Postabdomen ( Figs 12I–J, 13C). Relatively widest at preanal angle and with rounded dorso-distal margin. About two to 2.5 times as long as wide. Ventral margin shorter than anal and postanal margin together ( Figs 12I–J). Anal margin longer than postanal margin as long as preanal margin. Anal margin slightly concave, postanal margin convex. Distal embayment (dorsal to basal claw) about half of claw width at base. Preanal corner well developed, protruding just beyond maximal dorsal point of postanal margin ( Fig. 12I). Marginal postanal teeth five to six groups. Each distal marginal tooth with four to five adjacent smaller spines on anterior side ( Fig. 13C). These marginal teeth rather long, about two times as long as wide (at base). Lateral setae arranged in fascicles in postanal portion in four to six groups ( Fig. 12I), consisting of six to eight elements in each group, parallel to each other. Distalmost lateral element thicker, in the two distalmost groups, protruding one third of its length beyond dorsal margin of postabdomen ( Fig. 12J). Distalmost lateral spines in postanal portion not reaching beyond the apex of the marginal teeth ( Fig. 12L). Smaller elements per fascicle decreasing in length ( Fig. 13C). Three to four clusters of long marginal elements, and four lateral fascicles in anal portion ( Fig. 12I). Preanal corner bears group of teeth as well ( Fig. 12I).
Terminal claw ( Figs 12I–K). As long as anal margin, moderately curved, implanted with setules along dorsal side. Proximal pecten ending in spine half as long to just as long as width of claw at this point and just before half of claw length ( Fig. 12I). Basal spine ( Fig. 12K) quite slender and one to 1.5 times claw width at base, reaching up to one fourth of claw length. Group of two to three long basal spinules, reaching half of basal spine length ( Fig.12K).
D. Head shield. E. Idem, posterior margin with head pores. F. Second antenna. G. Labral keel, lateral view. H. First antenna. I. Postabdomen (Wadi Zerik). J. Postabdomen (Homhill). K. Idem, detail of basal spine. L. Idem, detail showing lateral fascicle and marginal tooth.
Five pairs of limbs. First limb ( Figs 14B–D). Epipodite round with no projection ( Fig. 14B). First to third endites as for genus. Longest seta in second endite with 12–13 teeth ( Fig. 14B). Shape of these teeth is shown in Fig. 13F (seta on which base is written “en2”). Anterior elements strongly reduced ( Figs 13F, 14D). Outer and distal lobes ( Figs 13E, 14C). ODL with one slender seta, as long as or just longer than largest IDL seta and with short fine setules in distal half ( Figs 13E, 14C); two setae in IDL, modified ( Figs 13E, 14C). On largest IDL seta, one large spine followed by reduced distal part; spine in longest IDL seta shorter than distal part beyond this spine. On shortest IDL seta ( Fig. 13C), two long spines of which proximal is shorter and both shorter than distal part of this seta. A third element present in IDL, remnant of a third seta ( Fig. 14C). Accessory seta present, half size of ODL seta (in Fig. 14B, dotted lines). Anterior setule groups ( Fig. 14B) reduced, with five to ten setules in each group, decreasing in size ventrally. Ejector hooks unequal, relatively large ( Fig. 14B).
Second limb ( Figs 13F, 14E–H). Exopodite ( Fig. 14G) elongate, two times as long as wide, with short seta reaching just beyond exopodite apex; tuft of hairs on exopodite apex; endites ( Fig. 14E) with eight scrapers gradually decreasing in size towards gnathobase, eighth scraper shortest ( Figs 13F, 14E). First two scrapers ( Fig. 14E) relatively slender and finely setulated, first longest. Third scraper ( Fig. 14E) markedly shorter, modified with stronger teeth, and intermediate in size between scrapers two and four. Scrapers four and five ( Fig. 14E) similar, with fine denticles, scraper six ( Figs 13F, 14F) shorter by half and with eight to nine stronger teeth; SEM shows these teeth are much thicker than in following scrapers ( Fig. 13F); final two scrapers decreasing in size towards gnathobase, scraper eight with fine denticles ( Fig. 13F). Gnathobasic ‘brush’ short and round, implanted with short denticles ( Fig. 13F). Gnathobase ( Fig. 14E) as for genus; filter comb ( Fig. 14E) with seven setae of which first two ( Fig. 14H) shorter, third intermediate between these two and fourth filter seta.
Third limb ( Figs 14I–L). Epipodite round without projection; exopodite shape ( Figs 14I–J) as for genus, with six setae; first exopodite seta just longer than second, not thicker ( Fig. 14J); third exopodite seta twice as long as fifth exopodite seta, fourth seta just longer than fifth seta and three times as long as sixth seta ( Fig. 14J). Endite ( Figs 14K–L) as for genus; strongly developed denticles in setae 1’–2’ ( Fig. 14L), long setae in internal endite preceding gnathobase and filter comb setae about as long as last seta on inner side (4”) ( Fig. 14K).
Fourth limb ( Figs 14M–O). Epipodite oval without long projection. Exopodite ( Fig. 14M) with six marginal plumose setae; first three exopodite setae longer than last three and of similar size, fourth seta two thirds length of preceding seta; fifth and sixth setae narrow. Both these setae shorter than the fourth, fifth just longer than sixth ( Fig. 14M). Endite ( Figs 14N–O) as for genus; inner row (1”–3”) adorned with one shorter and three larger setae ( Fig. 14O); filter comb setae of similar length of last inner seta (3”) ( Fig. 14O).
Fifth limb ( Fig. 14P). Epipodite oval without long projection. Exopodite ( Fig. 14P) 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, as long as exopodite width; third shorter than second exopodite seta, fourth exopodite seta a third of preceding seta; inner portion of limb ( Fig. 14P) with broad oval inner lobe and long apical setules; two endite setae of which first longer; this seta just reaching apex of inner lobe; second endite seta shorter by a fourth of latter. Gnathobase as for genus.
Adult male ( Fig. 15). Size 0.3–0.35mm. (n=5), body 1.8 as long as high. Body not widening posteriorly ( Fig. 15A). Postabdomen ( Figs 15B–C) about 2.5 times as long as wide, with well-developed triangular preanal projection. Distalmost spine in each lateral fascicle on postabdomen long and reaching beyond dorsal margin of postabdomen ( Figs 15B–C). Terminal claw thick and short (shorter than anal margin) with small basal spine. Gonopores opening ventrally, adjacent to basal claw and in a subterminal indent. First limb ( Fig. 15E–G) with IDL bearing three setae ( Fig. 15E), of which two modified in distal portion, though less as in females. Third IDL seta naked and as long as two modified setae ( Fig. 15E). ODL seta ( Fig. 15G) longer than IDL setae. Copulatory hook ( Fig. 15E) strongly curved and with long terminal part, in inner side of a broad-based joint. Second limb with modified scrapers as in females, but exopodite seta absent ( Fig. 15H).
Ephippial female and ephippium. Ephippial larger than parthenogenetic female (up to 0.58mm), ephippium light orange brown, never dark brown or black.
Differential diagnosis. A. mediterranea has a rather unusual body shape for this genus ( Fig. 12C): the posterior valve margin is not strongly expanded in its lower (ventral) half and the species is more elongate. Ornamentation of the carapace is peculiar; all specimens examined had dense fine striation, rare in the genus (may also occur in A. harti n. sp.; see also A. lineolata below). The labral keel is unique; instead of a denticle, A. mediterranea has a proximal tuft of small setules ( Fig. 12G). Groups of spinules on the antennal segments are not strongly modified as in A. verrucosa , but fine ( Fig. 12F). The first exopod seta on the second antenna is relatively short, never reach- mediterranea , with the chitin ring around the main pores narrowing towards the ends (not round as in all other Anthalona ). The limbs have no long projections on the epipodites, a character visible through the carapace without dissection. Spines on P1 (IDL) are not as pronounced as in A. verrucosa and the sixth scraper on second limb has eight to nine teeth ( Fig. 13F) in comparison to A. harti .
Distribution and ecology. Anthalona mediterranea was described from Turkey ( Yalim & Ciplak 2005), but the name is not well chosen, as the Mediterranean is just its northern range limit. A. mediterranea has a wide distribution in arid regions: we found it on Socotra Island ( Yemen) and in short-lived temporary pools in the United Arab Emirates, sympatric with Alona cambouei and Karualona spp. Its distribution may extend further south into Africa, where other species occur (e.g., A. harti n. sp., found as north as Spain); it is not unlikely that both may be found sympatrically. Populations from Eastern and Northern Africa should be restudied in detail. We found that Anthalona mediterranea is an inhabitant of temporary rock pools in dry riverbeds in Arabia ( UAE), rich in filamentous algae. It lives in highly arid environments. In permanent rivers on Socotra Island (Wadi Zerik on Diksam Plateau), populations had smaller body sizes than in warm stagnant rockpools (Homhill). We observed A. mediterranea alive by using “Sars’ Method” ( Van Damme & Dumont 2010) for mud from the UAE; populations develop after three weeks to one month of wetting dried mud, the animals feed on detritus and diatoms on sandy substrate and swim freely (but slowly) in the water column.
Remark. Anthalona mediterranea may be identical to the Chinese Alona verrucosa lineolata Chen & Li, 1991 (now Anthalona lineolata comb.nov.), depending on revision of the Chinese populations. More on this taxon below, under Anthalona incertae sedis.
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