Alona aguascalientensis, 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 : 2-9

Alona aguascalientensis sp. nov.

( Figs 1–4 )

Etymology. Species named after its terra typica, Aguascalientes State of Mexico.

Type locality: Pond beside highway Villa Hidalgo city—Aguascalientes city, Aguascalientes state. Mexico, 0 4.09.1990, 21° 52' N; 102° 22' W.

Type material. Holotype: parthenogenetic female from the type location, MGU Ml 120.

Paratypes: 18 parthenogenetic females, 2 males, 1 juvenile male of instar II from the type location, MGU Ml 121; 15 parthenogenetic females from Pond in La Tacuacha farm. Aguascalientes, 0 4.09.1990, AYS; 1 parthenogenetic female from Mesa Montoro mountain, Calvillo, Aguascalientes, 0 6.10.1990, AYS; 7 parthenogenetic females from Pond beside Mesa Montoro. Calvillo, Aguascalientes, 0 6.10.1990, AYS; 19 parthenogenetic females from Pool in El Mitote farm. El Llano, Aguascalientes, 21.07.1988, AYS; 6 parthenogenetic females from Pond beside highway Aguascalientes city – SLP city, El Llano, Aguascalientes, 28.09.1991, AYS; 1 parthenogenetic female from Pond in Los Conos town, El Llano, Aguascalientes, 18.01.1989, AYS; 6 parthenogenetic females from Pond 1, beside El refugio pond, Asientos, Aguascalientes, 0 1.09.1990, AYS; 3 parthenogenetic females from Pond Laguna Seca. San Josй de Gracia, Aguascalientes, 19.01.1989, AYS; 1 parthenogenetic female from Pond near road to Los Arquitos town (in El Cariñan farm), Jesús María, Aguascalientes, 0 7.07.1988, AYS; 8 parthenogenetic females from Pond near La Tomatina town. Jesús María, Aguascalientes, 12.12.1989, AYS; 5 parthenogenetic females from Pond near Vista town. Jesús María, Aguascalientes, 0 7.10.1989, AYS; 18 parthenogenetic females, 1 male from Pond beside El refugio pond, Asientos, Aguascalientes, 0 1.09.1990, AYS; 17 parthenogenetic females from Pond 1, 1 km from El Refugio town, Asientos, Aguascalientes, 15.02.1991, AYS; 20 parthenogenetic females from Pond 1, near Túnel de Potrerillos town, Rincón de Romos, Aguascalientes, 11.08.1990, AYS; 7 parthenogenetic females from Pond 3, near Túnel de Potrerillos town. Rincón de Romos, Aguascalientes, 11.08.1990, AYS.

Diagnosis. Parthenogenetic female. Body regularly oval, of moderate height, maximum height at middle of body, in adults height/length ratio 0.59–0.63. Dorsal margin uniformly curved; postero-dorsal and postero-ventral angles broadly rounded. Body moderately compressed laterally. Postero-dorsal angle with about 80 short setules not organized in groups, and frequently with 1–2 small triangular denticles. Ventral margin with about 35–45 setae. Head shield with broadly rounded, slightly wavy posterior margin; rostrum short, broadly rounded. Three major head pores, connection between anterior and middle pore from well-developed, narrow interrupted; connection between middle and posterior pore absent; PP about 0.4–0.6 IP. Minute lateral head pores located about 1.2–1.3 IP distance from midline, at the level of anterior major head pore. Labrum of moderate size; labral keel wide with convex or wavy anterior margin, rounded apex and posterior margin without any setules.

Postabdomen of moderate width, with almost parallel margins in postanal portion, length about 2.5 height. Distal margin straight to weakly convex, distal angle not prominent, broadly rounded. Dorsal margin with almost straight postanal portion and weakly concave anal portion. Distal part 1.7–1.8 times longer than preanal one, with postanal portion slightly longer than anal. Preanal angle well-defined, postanal angle not defined. Postabdomen with 8–9 well-developed marginal denticles of similar size, and with three-four groups of marginal setules on anal margin. Eight-ten lateral fascicles of setules, six-seven distalmost fascicles large, with distalmost seta of each fascicle 1.5 times longer than marginal denticlees. Postabdominal claw of moderate length, slightly longer than preanal portion of postabdomen. Basal spine about 0.3 of length of claw.

Antennule of moderate size, 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 of same length with endopodite. Spine on basal segment of exopodite shorter than middle segment. Apical spines slightly 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. Exopodite V oval, with four setae, filter plate V absent. Epipodites IV and V with very short projections. Limb VI absent.

Male. Body of adult low oval, height/length ratio about 0.58. Both eye and ocellus of similar size with these of female, eye larger ocellus. Postabdomen short, strongly narrowing distally in anal portion, subrectangular in postanal portion. Gonopores located at the end of postabdomen, above the base of claws. Distal margin convex, distal angle broadly rounded. Preanal angle well-defined, prominent, postanal angle not defined. Distal part of postabdomen 1.2–1.3 times longer than preanal, anal and postanal portions which are of similar length. Wide clusters of short setules in place of marginal denticles. Lateral fascicles of setules same as in female. Postabdominal claw very short, 2.5 times shorter than preanal portion of postabdomen, basal spine very long, about 2/3 of claw length.

Antennule with two lateral aesthetascs and about ten terminal ones. Male seta arising at 1/4 length from tip, about 1/5 of antennule length. Limb I with U-shaped, copulatory hook, its distal portion little longer than basal one. A group of about ten thick setules, followed by group of five thinner setules, located under copulatory brush on ventral face of limb. IDL seta 1 very small, setae 2 and 3 thinner and 1.5 times shorter than in female, male seta large, hook-like, almost as longer as seta 3.

Size: In juvenile females of instar I, length is 0.26–0.27 mm, height 0.15–0.16 mm; in juvenile females of instar II, length 0.31–0.34 mm, height 0.18–0.20 mm; in adult female length 0.37–0.46 mm, height 0.22–0.28 mm. Length of single studied juvenile male of instar II was 0.34 mm, height 0.20 mm; in two studied adult males, length was 0.36 and 0.37 mm, height 0.21 mm in both specimens.

Description. Parthenogenetic female. General. In lateral view body regularly oval, of moderate height ( Figs. 1 A–C, 2A–B), maximum height at middle of body, in adults height/length ratio 0.59–0.63. 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 (Fig. 2C).Valves without prominent sculpture. Ventral margin ( Fig. 1 D) with about 35–45 setae, first 8–11 setae long, next 10 setae short, other setae of moderate length. Postero-dorsal angle ( Figs. 1 E–H) bears about 80 short setules of similar length, not organized in groups, and frequently – 1–2 small triangular denticles. A row of about 80 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. 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, slightly wavy. Three major head pores ( Figs. 1 I–J, 2D–E), connection between anterior and middle pore from well-developed, narrow to interrupted, connection between middle and posterior pore absent; PP about 0.4–0.6 IP. Lateral head pores minute, located about 1.2–1.3 IP distance from midline, at the level of anterior major head pore. Labrum ( Figs. 3 A–B) of moderate size; distal labral plate without setulation; labral keel wide (height about 1.5 width), with rounded apex; anterior margin of keel convex or wavy, posterior margin without any setules.

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

Postabdomen of moderate width, with almost parallel margins in postanal portion, length about 2.5 height (Figs. 2F–G, 3C–D). Ventral margin weakly convex to 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 1.7–1.8 times longer than preanal one, with postanal portion slightly longer than anal. Postanal portion of distal margin almost straight, anal portion weakly concave. Preanal angle well-defined, postanal angle not defined. 8–9 well-developed marginal denticles of similar size, most with one-two additional spinules near base of denticle, and with three-four groups of marginal setules on anal margin. Eight-ten lateral fascicles of setules, sixseven distalmost fascicles large, with distalmost seta of each fascicle 1.5 times longer than marginal denticles. Several additional fascicles above the main row in anal portion. Postabdominal claw (Fig. 2H) of moderate length, slightly longer than preanal portion of postabdomen. Basal spine about 0.3 of length of claw.

Antenna I ( Fig. 3 E) of moderate size, length about 2.5 widht, with three clusters of long thin setules at anterior face. Antennular sensory seta slender, three times shorter than antennula, arising at 2/3 distance from the base. Nine terminal aesthetascs, two longest of them about 2/3 length of antennula.

Antenna II relatively short (Figs. 2I, 3F–G). 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 of same length as endopodite. Seta arising from middle segment of endopodite of similar size of apical setae. Spine on basal segment of exopodite shorter than middle segment. Apical spines slightly longer than apical segments.

Thoracic limbs: five pairs. Limb I ( Figs. 4 A–B) of moderate size. Epipodite ovoid. Accessory seta about 1/3 length of ODL seta. ODL with a long seta, armed with minute setules in distal part. IDL with three setae and twothree clusters of small setules; setae 2 and 3 only slightly shorter than ODL seta, armed with large, thick 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) shifted to limb base. No inner setae on endites 1–2. Six rows of thin long setules on ventral face of limb. Two ejector hooks, one of them larger than the other. Maxillar process elongated, with a short seta.

Limb II ( Figs. 4 C–D). Exopodite elongated. Eight scraping setae (1–8), armed with spinules of similar shape, increasing in length distally. Distal armature of gnathobase with four elements. Filter plate with seven setae, the posteriormost seta three times shorter than others.

Limb III ( Figs. 4 E–F). Epipodite oval; exopodite subrectangular, with seven setae. Seta 3 being longest, setae 4 and 6 about 1/4 and 1/3 length of seta 3, respectively, other setae short. Seta 6 armed with thick long setules in distal part, seta 7 naked, all other setae plumose. Distal endite with three setae, two distalmost members slender, sharp, with distal parts unilaterally armed with sharp 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 four elements: an elongated, cylindrical sensillum, a thin, bent seta, and two sharp spines. Filter plate III with seven setae.

Limb IV ( Figs. 4 G–H). Preepipodite setulated, epipodite with short process. Exopodite rounded, with six setae. Seta 3 longest, setae 1–2 slightly shorter than seta 3, setae 4, 5 and 6 of 1/3, 1/2 and 1/3 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 reduced distal part, armed with 5–6 short setules only, 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. 4 I). Preepipodite setulated. Epipodite oval, with short process. Exopodite oval, not divided into two lobes, with four plumose setae, decreasing in size basally; seta 4 four 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 1.5 times shorter. No filter plate.

Ephippial female. Unknown.

Male. Body of instar II juvenile male ( Fig. 1 K) of same shape as in juvenile female of same instar. Body of adult male ( Fig. 1 L) slightly lower than in female, height/length ratio about 0.58. Both eye and ocellus of size as in female, eye larger than ocellus.

Postabdomen of instar II juvenile male ( Fig. 3 H) of similar shape with that of female, ventral margin with clear step in the region of gonopores. Gonopores located at 1/3 length of ventral margin from to the end of postabdomen. Armament of postabdomen same as in female. Postabdominal claw same as in female. In adult male, postabdomen ( Fig. 3 J) short, strongly narrowing distally in anal portion, subrectangular in postanal portion. Gonopores located ventrally at the end of postabdomen, close to the base of claws. Distal margin convex, distal angle broadly rounded. Preanal angle well-defined, prominent, postanal angle not defined. Distal part of postabdomen 1.2–1.3 times longer than preanal, anal and postanal portions of similar length. Wide clusters of short setules in place of marginal denticles. Lateral fascicles of setules same as in female. Postabdominal claw very short, 2.5 times shorter than preanal portion of postabdomen, basal spine very long, almost straight, about 2/3 of claw length.

Antennule of instar II juvenile male ( Fig. 3 I) broader than in female, with 9 terminal aesthetascs and a very small anlage of male seta. In adult male, antennule ( Fig. 3 K) broad, length about two widths. Aesthetascs were poorly preserved in all available specimens, there are two lateral aethetascs, number of terminal aesthetascs and their length is unclear. Male seta arising at 1/4 length from tip, about 1/5 of antennule length.

Limb I of instar II juvenile male ( Figs. 4 I–J) with U-shaped copulatory hook; ventral face of limb with an anlage of copulatory brush seta and a peculiar hillock above it, not present in adult male. A row of about ten short setules on the ventral face of limb below the copulatory brush. Setae of endites same as in female. IDL with anlage of male seta; other setae (1–3) same as in female. In adult male, limb I ( Figs. 4 K–L) more massive than in female, copulatory hook U-shaped, its distal portion little longer than basal one. A group of about ten thick setules, followed by group of five thinner setules, located under copulatory brush on ventral face of limb. Endite 3 more broad than in female, its seta 1 much thinner and slightly longer than in female. IDL seta 1 very small, setae 2 and 3 thinner and 1.5 times shorter than in female, male seta large, hook-like, almost as long as seta 3.

Differential diagnosis. Alona aguascalientensis sp. nov. is a member of the pulchella -group of Alona s. lato and shares all distinctive features of the group. An unique feature of A. aguascalientensis sp. nov. is the presence of denticles on posteroventral corner of valves, which are never present in any other species of the group. It has moderately elongated, narrow postabdomen and clearly differs by its shape from A. azorica Frenzel & Alonso, 1988 , A. anastasia Sinev, Alonso, Miracle & Sahuquillo, 2012 , A. nigra Smirnov, 1996 , A. altiplana Kotov, Sinev & Berrios, 2010 , A. setulosa and A. anamariae sp. nov., which have shorter and broader postabdomens. A. aguascalientensis sp. nov. differs from A. karelica Stenroos, 1897 and A. bromelicola Smirnov, 1988 by the presence of long basal spine of the postabdominal claw. A. aguascalientensis sp. nov. differs from A. glabra Sars, 1901 , A. archeri Sars, 1888 , A. cambouei Guerne & Richard, 1893 , and A. pulchella King, 1853 by weakly protruding distal angle of postabdomen and postanal marginal denticles of postabdomen being of the same size. A. aguascalientensis sp. nov. have morphology of major head pores rare for the group, with connection between central and posterior pores always absent, while connection between anterior and central pores present or interrupted. Most species of the group have either fully connected or fully disconnected major head pores, except A. azorica Frenzel & Alonso, 1988 and A. anastasia Sinev, Alonso, Miracle & Sahuquillo, 2012 wich show a similar pattern as A. aguascalientensis sp. nov..

Distribution. So far it is known only from Aguascalientes. This quite distinctive species was not recorded in any works on Mexican cladocera (Elias-Gutierres et al. 2008b), so we expect it to be an endemic with limited area of distribution, confined to the Central Plateau of Mexico. The species is encountered in a wide range of water bodies of Aguascalientes State, from the dry-hot low altitude (1850 m.a.s.l.) to the cold-high altitude region, but is not recorded from the subtropical region.

Figures

FIGURE 1. Alona aguascalientensis sp. nov. pond beside highway Villa Hidalgo city—Aguascalientes city, Aguascalientes State, Mexico. A – B, juvenile females of instar I and II. C – J—parthenogenetic female. C, lateral view. D, valve. E – H, posteroventral angle of valves. I – J, head pores. K, instar II juvenile male. L, adult male. Scale bars denote 0.1 mm for A – C, K – L and D; 0.05 mm for E – J.

FIGURE 3. Alona aguascalientensis sp. nov. pond beside highway Villa Hidalgo city—Aguascalientes city, Aguascalientes State. Mexico. A – E, parthenogenetic female. A – B, labrum. C – D, postabdomen. E, antennule. F – G, antenna. H – I, instar II juvenile male. H, postabdomen. I, antennule. J – K, adult male. J, postabdomen. K, antennule. Scale bars denote 0.1 mm for F, 0.05 for A – E, G – K.

FIGURE 4. Alona aguascalientensis sp. nov. pond beside highway Villa Hidalgo city—Aguascalientes city, Aguascalientes State. Mexico. A – I, limbs of parthenogenetic female. A, limb I. B, IDL and ODL of limb I. C, limb II. D, exopodite of limb II. E, exopodite of limb III. F, distal part of inner portion of limb III. G, exopodite of limb IV. H, inner portion of limb IV. I, limb V. J – K, limb I of instar II juvenile male. L – M, limb I of adult male. Scale bar denotes 0.05 mm.