Alona anamariae, Sinev, Artem Y. & Silva-Briano, Marcelo, 2012

Sinev, Artem Y. & Silva-Briano, Marcelo, 2012, Cladocerans of genus Alona Baird, 1843 (Cladocera: Anomopoda: Chydoridae) and related genera from Aguascalientes State, Mexico, Zootaxa 3569, pp. 1-24 : 9-13

Alona anamariae sp. nov.

( Figs 5–6 )

Etymology. Species names honors Ana Maria Briano-Baéz, a mother of the second author.

Type locality. La Araña dam, Sierra Fría, San Josй de Gracia, Aguascalientes. 29.09.1993, 22° 14' N, 102° 37' W.

Type material. Holotype: parthenogenetic female from the type location, MGU Ml 118.

Paratypes: 9 parthenogenetic females from the type location, MGU Ml 119; 10 parthenogenetic females from a pond near Hacia Tapias Viejas, Jesús María, Aguascalientes, 0 4.09.1993, AYS; 5 parthenogenetic females from Pond beside Los Hoyos town (to highway from Aguascalientes city to SLP city), El. Llano, Aguascalientes, 0 9.08.1988, AYS.

Diagnosis. Parthenogenetic female. Body regularly oval, of moderate height; maximum height at middle of body; in adults height/length ratio about 0.66. Dorsal margin uniformly curved; postero-dorsal and postero-ventral angles broadly rounded. Body moderately compressed laterally. Ventral margin with about 30–35 setae, first 7–8 setae evenly increasing in length, last seta in the group very long, 1.5 times longer than previous. Postero-ventral angle with about 40 short setules, without denticles. Head shield with broadly rounded posterior margin; rostrum short, broadly rounded. Three narrowly connected major head pores, PP about 0.2–0.3 IP. Lateral head pores minute, located about 1.5 IP distance from midline, at the level of anterior major head pore. Labrum of moderate size; labral keel moderately wide, with convex anterior margin, rounded apex, and posterior margin with two clusters of short setules.

Postabdomen short and broad, evenly truncated, length about 2.5 height. Distal margin straight to weakly convex, distal angle not prominent, broadly rounded. Postanal portion of distal margin straight, anal portion weakly concave. Dorsal margin with distal part 1.5 times longer than preanal one, with postanal portion shorter than anal. Preanal angle well-defined; postanal angle not defined. Postabdomen with 5–6 well-developed slender marginal denticles, decreasing in size basally, and with 2–4 groups of marginal setules on anal margin. Seven-eight lateral fascicles of setules; six-seven distalmost fascicles large, with distalmost seta of each fascicle slightly longer than neighboring marginal denticles. Postabdominal claw of moderate length, slightly longer than preanal portion of postabdomen. Basal spine about 0.2 of length of claw.

Antenna I short and broad, with nine terminal aesthetascs. Antennal formula, setae 0–0–3/1–1–3, spines 1–0–1/0–0–1. Seta arising from basal segment of endopodite reaching to the end of endopodite. Spine on basal segment of exopodite longer than middle segment. Apical spines longer than apical segments. Limb I with accessory seta 3 times shorter than ODL seta. IDL with three setae, seta 1 well-developed, about 1/3 length of seta 3. Scrapers of limb II of similar morphology. Exopodite of limb III with seven setae, seta 3 being longest. Exopodite IV with six setae, flaming-torch setae of limb IV with well-developed distal portion. Exopodite V oval, with four setae, filter plate V absent. Epipodites IV and V with very long projections. Limb VI absent.

Male unknown.

Size. In single studied juvenile female of instar I, length is 0.23 mm, height 0.13 mm; in juvenile females of instar II, length 0.28–0.30 mm, height 0.17–0.18 mm; in adult female length 0.33–0.36 mm, height 0.23–0.25 mm.

Description. Parthenogenetic female. General. In lateral view body ( Figs. 5 A–C) regularly oval, of moderate height, maximum height at middle of body, in adults height/length ratio about 0.66. Dorsal margin uniformly curved; postero-dorsal and postero-ventral angles broadly rounded; posterior margin uniformly curved; ventral margin almost straight; antero-ventral angle rounded. Body moderately compressed laterally. Valves without prominent sculpture. Ventral margin ( Fig. 5 D) with about 30–35 setae, first 7–8 setae evenly increasing in length, last seta in the group very long, 1.5 times longer than previous, next 10 setae short, other setae of moderate length. Postero-dorsal angle bears about 40 short setules of similar length, not organised in groups. A row of about 60 setules along the posterior margin on inner side of valve.

Head of moderate size, triangle-round in lateral view, rostrum short, pointing downward. Eye larger than ocellus, both of them relatively large. Distance from tip of rostrum to ocellus in adults slightly greater than that between ocellus and eye. Head shield with maximum width behind mandibular articulation, without any sculpture; rostrum short, broadly rounded; posterior margin of head shield broadly rounded. Three narrowly connected major head pores, PP about 0.2–0.3 IP ( Figs. 5 E–F). Lateral head pores minute, located about 1.5 IP distance from midline, at the level of anterior major head pore. Labrum ( Figs. 6 A–C) of moderate size, labral keel moderately wide (height about 1.7 width), with rounded apex; anterior margin of keel convex, posterior margin with two clusters of very short setules.

Thorax two times longer than abdomen, dorsal surface of abdominal segments not saddle-shaped.

Postabdomen ( Figs. 5 G–H) short and broad, evenly truncated, length about 2.5 height. Ventral margin straight. Basis of claws separated from distal margin by clear incision. Distal margin straight to weakly convex, distal angle not prominent, broadly rounded. Dorsal margin with distal part 1.5 times longer than preanal one, with postanal portion shorter than anal. Postanal portion of distal margin straight, anal portion weakly concave. Preanal angle well-defined, postanal angle not defined. Five-six well-developed slender marginal denticles, increasing in size distally, most with additional spinule near base of denticle, and with two-four groups of marginal setules on anal margin. Seven-eight lateral fascicles of setules, six-seven distalmost fascicles large, with distalmost seta of each fascicle slightly longer than neighboring marginal denticles. Several additional fascicles above the main row in anal portion. Postabdominal claw of moderate length, slightly longer than preanal portion of postabdomen. Basal spine about 0.2 of length of claw.

Antenna I ( Fig. 6 D) short and broad, length about 2 widths, with three clusters of very short setules at anterior face. Antennular sensory seta slender, two times shorter than antenna I, arising at 2/3 distance from the base. Nine terminal aesthetascs, two longest of them about half length of antennule.

Antenna II relatively short ( Fig. 6 E). Antennal formula, setae 0–0–3/1–1–3, spines 1–0–1/0–0–1. Basal segment robust, branches of moderate length and width, basal segments of both branches 1.5 times longer than others. Seta arising from basal segment of endopodite reaching to the end of endopodite. Seta arising from middle segment of endopodite of similar size with apical setae. Spine on basal segment of exopodite longer than middle segment. Apical spines longer than apical segments.

Five pairs of thoracic limbs. Limb I ( Figs. 6 G–F) of moderate size. Epipodite with a finger-like process, 1.5 times longer than epipodite itself. Accessory seta about 1/3 length of ODL seta. ODL with a single long seta. IDL with three setae and two-three clusters of small setules, setae 2 and 3 of similar length, longer than ODL seta, armed with thin setules in distal part, seta 1 of about 1/3 length of seta 3. Endite 3 with four setae of similar size. Endite 2 with three setae (d–f), seta f very long, 1.5 times longer than ODL seta. Endite 1 with two 2-segmented setae, both setulated in distal part, without a flat seta (i). No naked inner setae on endites 1–2. Six rows of thin long setules on ventral face of limb. Two ejector hooks, one of them slightly larger than the other. Maxillar process elongated, with a short seta.

Limb II ( Fig. 6 H). Exopodite elongated, with a single naked seta of about half length of exopodite. Eight scraping setae, armed with spinules of similar shape, increasing in length distally. Distal armature of gnathobase with four elements. Filter plate with seven setae, the posteriormost three times shorter than others.

Limb III ( Figs. 6 I–K). Epipodite oval; exopodite subrectangular, with seven setae. Seta 3 being longest, seta 6 about 1/3 length of seta 3, setae 1 and 4 about 1/4 length of seta 3, other setae short. Seta 6 armed with thick long setules in distal part, seta 7 almost naked, all other setae plumose. Distal endite with three setae, two distalmost members slender, sharp, with distal parts unilaterally armed with minute denticles; basalmost seta much shorter, bilaterally armed with setules. Basal endite with four stiff setae, increasing in size toward the base, a small sensillum near the base of distalmost seta. Four soft setae increasing in size basally (a–d). Gnathobase not clearly separated from basal endite. Distal armature of gnathobase with three elements: an elongated, cylindrical sensillum; thin, bent seta and a sharp spines. Filter plate III with seven setae.

Limb IV ( Figs. 6 L–N). Preepipodite setulated, epipodite with a short process. Exopodite rounded, with six setae. Seta 3 longest, setae 1–2 slightly shorter than seta 3, setae 4, 5 and 6 of 1/2, 2/3 and 1/2 length of seta 3, respectively. Setae 1–4 plumose, seta 1–2 with short setules, almost plumose. Inner-distal portion of limb IV with four setae and small cylindrical sensillum, seta 1 slender,sharp, three flaming-torch setae (2–4) of similar shape, with well-defined distal part, armed with 6–7 long setules, decreasing in size basally. Three soft setae increasing in size basally. Gnathobase with a 2-segmented seta, and a small hillock distally. Filter plate with five setae.

Limb V ( Fig. 6 O). Preepipodite setulated, epipodite oval, with a short process. Exopodite oval, not divided into two lobes, with four plumose setae, decreasing in size basally, seta 4 four-five times shorter than seta 1. Inner limb portion of oval lobe, with setulated inner margin. At inner face, two setae, one equal in length to seta 2 of exopodite, other two times shorter. No filter plate.

Ephippial female and male unknown.

Differential diagnosis. Alona anamariae sp. nov. is a member of the pulchella -group of Alona s. lato and shares all distinctive features of the group. A unique feature of A. anamariae sp. nov. is a very long last seta in the anterior group of setae of ventral margin of valves and short, relatively wide, evenly narrowing distally postabdomen. A. anamariae sp. nov. differs from the most species of the group by the small size. From similarlysized A. altiplana it also differs by the different proportions of setae on exopodites III–IV, and by the shorter postanal denticles of postabdomen. In general morphology and shape of postabdomen A. anamariae sp. nov. is similar to A. barbulata Megard, 1967 , North American species of unclear affinities, but clearly differs from it by the absence of setulation on distal portion of labrum, by the morphology of head shield and head pores (in A. barbulata posterior part of head shield is triangular, lateral head pores are located closely to major pores), and by the morphology of the lateral fascicles of setules on postabdomen (in A. barbulata all setules in the fascicle are of the similar thickness, longest setules are located in the middle of fascicle).

Distribution. A. anamariae sp. nov. so far is known only from Aguascalientes, where it is rare. A. anamariae sp. nov. was not recorded in any previous publications on Mexican Cladocera ( Elías-Gutiérrez et al. 2006) , so we expect it to be an endemic with a limited area of distribution, confined to the Central Plateau of Mexico. The species is encountered in two localities from the east part of the state (dry-hot and high temperature in summer); in contrast, the type locality, La Araña dam, is the only place where this species was found in cold, high altitude area.

Figures

FIGURE 5. Alona anamariae sp. nov. from La Araña dam, Sierra Fría, San Josй de Gracia, Aguascalientes State, Mexico. A – B, juvenile females of instars I and II. C –, parthenogenetic female. C, lateral view. D, ventral margin of valves. E – F, head pores. G – H, postabdomen. Scale bars denote 0.1 mm for A – C and D, 0.05 for E – H.

FIGURE 6. Alona anamariae sp. nov. from La Araña dam, Sierra Fría, San Josй de Gracia, Aguascalientes State, Mexico, parthenogenetic female. A – C, labrum. D, antennule. E, antenna. F, limb I. G, IDL and ODL of limb I. H, limb II. I, exopodite of limb III. J – K, inner portion of limb III. L, exopodite of limb IV. M – N, inner portion of limb IV. O, limb V. Scale bar denotes 0.05 mm.