Alona salina Alonso, 1996

Sinev, Artem Y., Alonso, Miguel & Sheveleva, Natalia G., 2009, New species of Alona from South-East Russia and Mongolia related to Alona salina Alonso, 1996 (Cladocera: Anomopoda: Chydoridae), Zootaxa 2326, pp. 1-23 : 15-20

Alona salina Alonso, 1996

( Figs. 9–11 )

Alona sp. — Alonso, 1990: 224 –225, fig. 2a–b. Alona salina Alonso, 1996: 335 –337, fig. 150.

Material examined. Parthenogenetic and ephippial females, adult and juvenile males (over 250 specimens in total) from Laguna de la Dehesilla, 39º25’19.08”, N, 2º50’26.47”E, neighborhood of Mota Del Cuervo, Castilla La Mancha, Spain, 0 1.05.1999.

Description. Parthenogenetic female. General: In lateral view body regular oval, moderately high in adult ( Fig. 9 C), lower, irregular oval in juveniles ( Fig. 9 A–B). Maximum height in adult at the middle of the body; in juveniles, in the second quarter of the body. In juveniles of both instars height /length ratio about 0.60; in adults 0.64–0.68. Dorsally arched, without any depression at the border of valves and head shield. Posterodorsal and posteroventral angles broadly rounded. Posterior margin convex. Posterodorsal angle with about 50 setules of similar size, much thicker than in two previous taxa, separated into several groups. A row of about 100 smaller setules along the posterior margin ( Fig. 9 E), at some distance from it on inner side of carapace. Ventral setae as in two previous species. Anteroventral angle rounded. Carapace covered by narrow longitudinal lines and hexagons, clearly visible under optic microscope ( Fig. 9 D).

Head relatively small, triangle-round in lateral view, rostrum short, pointing downward. Eye larger than ocellus. Distance from tip of rostrum to ocellus equal or slightly greater than that between ocellus and eye.

Head shield with gently polygonal structures ( Fig. 9 A–F). Three narrowly connected major head pores, connection between them more narrow than in two previous species ( Fig. 10 A–B). Middle pore slightly smaller than others, located at the middle between others. PP about 0.6–0.8 IP. Lateral head pores slightly elongated, located about 1.1–1.2 IP distance from midline, at the level between the middle and anterior major head pores. Labrum ( Fig. 10 C–E) as in two previous species.

Postabdomen ( Fig. 9 G–H) wider than in two previous species, weakly narrowing in postanal portion, with broadly rounded dorsodistal angle. Length about 2.3–2.5 height. Ventral margin almost straight. Inflated basis of claws bordered from distal margin by clear incision. Distal margin almost straight. Dorsal margin with distal part about 1.8–2.0 times longer than preanal one, with postanal and anal portion subequal in length. Postanal portion of distal margin weakly convex, anal portion concave. Preanal angle moderately defined, postanal angle not defined or weakly defined. Preanal margin almost straight.

Postabdomen with 8–10 clusters of small marginal denticles and setules, decreasing in size basally, along preanal and anal margin; 8–10 lateral fascicles of setules; 6 or 7 fascicles in postanal portion wide, with setules two times longer than marginal denticles, fascicles in anal portion much smaller. First setules in postanal fascicles more thick than others. Postabdominal claw of moderate length, slightly shorter than preanal portion of postabdomen. Basal spine thin, about 1/4 of length of claw, a cluster of long setules located near its base.

Antennule ( Fig. 10 F) same as in A. floessneri sp. nov. Antenna ( Fig. 10 G) same as in two previous species.

Thoracic limbs: five pairs. Limb I as in two previous species ( Fig. 10 H–I), but IDL setae 2 and 3 more strong and robust. Setae of endite III slightly differentiated in size. Limb II as in two previous species ( Fig. 10 J). Limb III as in two previous species ( Fig. 10 K–L), but seta 5 of exopodite armed with long, thick setules. Limb IV as in two previous species ( Fig. 10 M–N), but setae 6 and 4 of exopodite almost as long as seta 5. A small sensillum on inner portion of the limb between bases of two basalmost flaming-torch setae, this structure was not observed in two previous species. Limb V as in two previous species ( Fig. 10 O).

Ephippial female ( Fig. 11 A) with higher body than parthenogenetic female, ephippium dark yellowbrown, with prominenet sculpture in shape of longitudinal lines thicker than on the rest of valves, in some specimens irregular polygons are present in lower portion of ephippium.

Male. General shape of juvenile males of instar I ( Fig. 11 B) and II ( Fig. 11 E) similar to that of juvenile females of same instar. General shape of adult male ( Fig. 11 I) similar to that of instar II juvenile female, body height/body length = 0.63–0.65. Ocellus and eye of same size as in female.

Postabdomen. In juvenile males of instar I similar to that of juvenile female ( Fig. 11 C), with sperm duct openings located before the middle of ventral margin. In juvenile males of instar II, shorter than that of female ( Fig. 11 F), with clear step on ventral margin in region of gonopores. Armament of postabdomen and postabdominal claw same as in female in both juvenile instars. In adult male, postabdomen short, with almost parallel margins in distal portion, dorso-distal angle broadly rounded ( Fig. 11 J). Preanal angle not defined, postanal angle well-defined. Distal part of postabdomens 1.3 times longer than preanal. Sperm duct openings located almost at the end of postabdomen. Clusters of short setules in place of marginal denticles, lateral fascicles of setules same as in female. Postabdominal claw 1.5 times shorter than that of female, basal spine of same size as in female.

Antennule. In instar I male same as in female. In instar II male antenule broader than in female, with anlage of male seta, aestetascs same as in female ( Fig. 11 G). In adult male antennule much shorter than in female ( Fig. 11 K), with 10 terminal and 2 lateral aesthetascs as long as terminal ones. Male seta arising at 1/3 length from tip, about 1/3 of antennule length.

Thoracic limb I. In instar I male with short anlage of copulatory hook, IDL same as in female ( Fig. 11 D). In instar II male, copulatory hook curved ( Fig. 11 H). Ventral face of limb with anlage of copulatory brush seta and a peculiar hillock above it, not present in any other instar. IDL with anlage of male seta, other setae same as in female. In adult male, limb I more stout than that of female ( Fig. 10 L), with U-shaped copulatory hook. Copulatory brush present. Row of about 15 short setules on ventral face of limb under copulatory brush ( Fig. 11 M). IDL seta 1 absent, setae 2 and 3 setae subequal in length, much thinner than in female, male seta thick, curved, as long as seta 2.

Size. In the studied population, instar I juvenile females length 0.29–0.32 mm, height 0.19–0.20 mm; instar II, length 0.35–0.38 mm, height 0.23–0.24 mm; adult female, length 0.39–0.61 mm, height 0.27–0.34 mm; instar I juvenile males, length 0.29–0.30 mm, height about 0.19 mm; instar II, length 0.31–0.33 mm, height 0.19–0.22 mm; adult males length 0.36–0.39 mm, height 0.22–0.24 mm.

Our data on morphology of Alona salina fully agree with those in the previous reports ( Alonso 1990, 1996) with one exception. Alonso (1996) mistakingly reported that the antenna of A. salina lack seta on the middle segment of exopodite. This seta is present. The morphology of ephippium of A. salina agrees with that reported by Vandekerkhove et al. (2004).

Distribution and ecology. A. salina is known from permanent and temporary subsaline and saline water bodies on the Iberian Peninsula. Alonso (1996) considers it an Iberian endemic, typical of the Spanish endorheic systems. According to Boronat et al. (2001), it occurs at the wide diapason of salinities ranging from 5.7 to more that 100 mg /l. In the Iberian Peninsula, A salina coexists with halo-tolerant cladocerans namely Daphnia magna , Daphnia akinsoni Baird, 1859 , Moina brachiata and Dunhevedia crassa King, 1853 , but also with true halophyle cladocerans such as Moina salina and Daphnia mediterranea Alonso, 1985 ( Alonso 1998) .

Figures

FIGURE 9. Alona salina Alonso, 1996, Laguna de la Dehesilla, A – B—juvenile females of instar I and II. C – Hparthenogenetic female: C—lateral viev, D—valve, E—posteroventral angle of valve, F—head shield, G – Hpostabdomen. Scale bars: 0.1 mm for A – D, F; 0.05 mm for E, G – H.

FIGURE 10. Alona salina Alonso, 1996, Laguna de la Dehesilla, parthenogenetic female. A – B—head pores. C-Elabrum. F—antennula. G—antenna. H – I—limb I and its ODL and IDL. J—limb II. K – L—exopodite and inner portion of limb III. M – N—exopodite and inner portion of limb IV. O—limb V. Scale bars: 0.1 mm for C – E, G; 0.05 mm for A – B, F, H – O.

FIGURE 11. Alona salina Alonso, 1996, Laguna de la Dehesilla, gamogenetic individuals. A—ephippial female. B – D—juvenile male of instar I: B—lateral view, C—postabdomen, D—inner portion of limb I. E – H—juvenile male of instar II: E—lateral view, F—postabdomen, G—antennula, H—inner portion of limb I. I – M—adult male II: I—lateral view, J—postabdomen, K—antennula, L – M—inner portion and endite 3 of limb I. Scale bars: 0.1 mm for A – B, E, I; 0.05 mm for and C – D, F – H, J – M.