Alona manueli, Sinev, Artem Y. & Zawisza, Edyta, 2013

Sinev, Artem Y. & Zawisza, Edyta, 2013, Comments on cladocerans of crater lakes of the Nevado de Toluca Volcano (Central Mexico), with the description of a new species, Alona manueli sp. nov., Zootaxa 3647 (2), pp. 390-400 : 392-397

Alona manueli sp. nov.

( Figs. 1–3 )

Biapertura intermedia . Elías-Gutiérrez, Ciros-Perez, Gutierrez-Aguirre & Cervantes-Martinez 1997: 71–72, Figs. 23–29 Alona intermedia . Elías-Gutiérrez, Suárez-Morales, Gutiérrez-Aguirre, Silva-Briano, Granados-Ramírez, Garfias-Espejo 2008: Figs. 40, 1–3

Etymology: the species name honors prominent Mexican carcinologist Dr. Manuel Elías-Gutiérrez, an author of the first record of the species.

Type locality: Lago de la Luna lake in the crater of the volcano Nevado de Toluca, State of Mexico, Mexico (19°06'13''N 99°45'20''W)

Type material. Holotype: partehnogenetic female from the type location, ZMMU, Ml-122.

Paratypes: 8 parthenogenetic females from the type location, ZMMU, Ml-123. Single male and several parthenogenetic females from the type location were dissected for the analysis of appendages, not deposited afterward.

Diagnosis. Parthenogenetic female. Body regularly oval, of moderate height, maximum height at middle of body, in adults height/length 0.63–0.70. Dorsal margin uniformly curved; postero-dorsal and postero-ventral angles broadly rounded. Body moderately compressed laterally. Postero-ventral angle with about 20 short setules organized in groups, without denticles. Ventral margin with about 40–50 setae. Head shield with broadly rounded distal angle; rostrum short, broadly rounded. Two major head pores with narrow connection between them, PP = 0.8–1.2 IP. Lateral head pores minute, located at about 0.7 IP distance from midline, at level between major head pores. Labrum of moderate size; labral keel moderately wide, with convex anterior margin and rounded or blunt apex; anterior margin of keel convex, posterior margin without any setules. Postabdomen moderately short and broad, subrectangular, maximum height at the middle of postanal margin. Length about 2.4–2.5 height. Ventral margin straight. Distal margin conveх, distal angle broadly rounded. Dorsal margin convex in postanal part and concave in anal part, with distal part about 1.7–1.8 times longer than preanal one, anal and postanal portions of similar length. Preanal angle well-defined, postanal angle not defined. Preanal margin almost straight. Postabdomen with 7–8 very short postanal marginal denticles, each denticle with 2–5 spinules, and with 3–4 groups of marginal setules on anal margin. 12–14 well-developed lateral fascicles of setules, posteriormost setae of postanal fascicles very thick and long, about 1.5–2 width of postabdominal claw base. Postabdominal claw weakly curved, slender, little longer than preanal margin of postabdomen. Basal spine moderately short, thin, about 0.2 length of claw itself. Antennule of long and narrow, 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 shorter than endopodite. Spine on basal segment of exopodite shorter than middle segment. Apical spines longer than apical segments. Limb I with accessory seta 4 times shorter than ODL seta. IDL with three setae, seta 1 well-developed, about 1/4 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 bilobed, with four setae, filter plate V absent. Epipodites IV and V with long projections. Limb VI absent.

Male. Body low oval, height/length ratio about 0.66. Eye of same size as in large females, larger than ocellus. Postabdomen similar in shape to that of female, but more narrow. Gonopores located at some distance from the end of postabdomen. Ventral margin straight, with defined step at the location of gonopores. Distal margin convex, distal angle broadly rounded. Preanal angle well-defined, postanal angle not defined. Distal part of postabdomen two 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 short, shorter than preanal portion of postabdomen, basal spine straight, about 0.25 of claw length. Antennule without lateral aethetascs. Male seta arising at 1/3 antennule length from tip, about 1/3 of antennule length. Limb I with U-shaped copulatory hook, its distal portion 1.5 times longer than basal one. A row of about 20 thick, moderately long setules located under copulatory brush on ventral face of limb. IDL without seta 1; setae 2 and 3 of similar length, much thinner and shorter than in female, male seta large, hook-like, almost as long as seta 3.

Description. Parthenogenetic female. General. In lateral view body regular oval ( Figs.1 A–B, D–E), moderately high, maximum height at middle of body, a height-to-length ratio 0.63–0.7 in adults, juvenile females with lower body than adult females. Body moderately compressed laterally. Dorsal margin uniformly curved; postero-dorsal and postero-ventral angles broadly rounded; posterior margin weakly curved; ventral margin almost straight; antero-ventral angle rounded. Valves with well-developed linear sculpture in dorsal and posterior portions. Ventral margin of valves ( Fig. 1 E) with 40–50 setae, about 10 anterior setae long, next 5–7 setae very short, followed by setae of moderate length, evenly decreasing in length posteriorly. Postero-ventral angle ( Fig. 2 A) bears about 20 short setules of enequal length, organised into 2–3 groups. A row of about 200 setules of unequal length, with very long setules separated by shorter ones, along the posterior margin on inner side of valve.

Head triangle-round in lateral view. In lateral view, rostrum short, pointed downward. Ocellus and eye of similar size. Shape of head shield ( Figs. 1 C, F–H) as usual for the genus, with maximum width behind the mandibular articulation. Rostrum short, broadly rounded. Posterior part of head shield with broadly rounded distal angle. Two main head pores of similar size with narrow connection between them ( Figs. 1 I–J), PP = 0.8–1.2 IP in adults. Lateral head pores minute, located at about 0.7 IP distance from midline, at level between main head pores.

Labrum ( Fig. 2 B) of moderate size; labral keel moderately wide, height-to-width ratio of about 1.5, with rounded or blunt apex; anterior margin of keel convex, posterior margin without any setules.

Thorax two times longer than abdomen. Middle abdominal segment not saddle-shaped, no abdominal joint.

Postabdomen ( Fig. 2 C, D) moderately short and broad, subrectangular, maximum height at the middle of postanal margin. Length about 2.4–2.5 height. Ventral margin straight. Distal margin conveх, distal angle broadly rounded. Dorsal margin convex in postanal part and concave in anal part, with distal part about 1.7–1.8 times longer than preanal one, anal and postanal portions of similar length. Preanal angle well-defined, postanal angle not defined. Preanal margin almost straight. 7–8 very short postanal marginal denticles, each denticle with 2–5 spinules, and with 3–4 groups of marginal setules on anal margin. 12–14 well-developed lateral fascicles of setules, posteriormost setae of postanal fascicles very thick and long, about 1.5–2 width of postabdominal claw base. Distal postanal fascicles narrow, consisting of 4–6 setules only, other fascicles of moderate width.

Postabdominal claw weakly curved, slender, little longer than preanal margin of postabdomen. Basal spine moderately short, thin, about 0.2 length of claw itself. Four-five small spines located near the base of claw before the basal spine.

Antennule ( Fig. 2 E) long and slender, length about 3 width, with four clusters of setules on inner face. Antennular sensory seta slender, three times shorter than antennule, arising at 2/3 distance from the base. Nine aesthetascs of similar size, about half-length of antennule, projecting beyond anterior margin of the head shield.

Antenna ( Fig. 2 F) with antennal formula setae 0-0-3/1-1-3, spines 1-0-1/0-0-1. Basal segment massive, branches of moderate length, basalmost segments of both branches 1.5 times longer than others. Seta arising from basal segment of endopodite thin, reaching tip of distal segment. Seta arising from middle segment of endopodite of similar size with apical setae. Apical setae of similar size and thickness. Spine on basal segment of exopodite slightly shorter than middle segment. Apical spines longer than apical segments.

Thoracic limbs: five pairs.

Llimb I ( Fig. 3 A–B) of moderate size. Epipodite oval, without projection. Accessory seta short, 4 times shorter than ODL seta. ODL seta with very short setules in distal part. IDL with 3 setae, seta 1 sharp, about length of ODL seta, setae 2 and 3 of moderate thickness, armed with thin setules in distal part, seta 3 almost as long as ODL seta, seta 2 about 2/3 length of ODL seta. Endite 3 with four setae subequal in length. On endite 2 there are three outer setae of different length, two longest of them (e–f) longer than ODL seta and inner naked seta on anterior face. Endite 1 with two 2-segmented setae (g–h), a flat, geniculated seta (i) shifted to the limb base, and inner naked setae on anterior face. Maxillar process long and narrow, with a single setulated seta. Four-five rows of long setules on ventral face of limb. Two slender ejector hooks, one of them slightly longer than other.

Limb II triangle-rounded ( Fig. 3 C–D). Exopodite elongated, of irregular shape, with short seta.

Inner portion of limb with eight scraping spines increasing progressively in length distally, armed with denticles of similar size. No inner setae near base of scraper 1. Distal armature of gnathobase with four elements. Filter plate II with seven setae, two posteriormost members considerably shorter than others.

Limb III. ( Fig. 3 E–G) Epipodite oval. Exopodite subquadrangular, with seven setae. Seta 3 longest, setae 6 about 1/3 length of seta 3, other setae short, more than two times shorter than seta 6. Setae 1–5 plumose, seta 6 armed bilaterally with hard setules, seta 7 with short thin setules at the middle. Distal endite with 3 setae and two small sensillae located between their base, two distalmost setae (1–2) scraping, slender, sharp, with denticles in distal part, basalmost seta (3) shorter, flattened, geniculated, bilaterally provided with setules. Basal endite with 4 setae (a–d). Four slender sharp inner setae; a small sensillum near the basalmost of them. Gnathobase with sensillum, small spine and a geniculated seta. Filter plate III with seven setae.

Limb IV ( Fig 3 H–I). Pre-epipodite setulated; epipodite with finger-like projection 1.5 times longer than epipodite itself. Exopodite subquadrangular, with six plumose setae. Seta 3 being longest, setae 1–2 slightly shorter than seta 3, seta 5 about 2/3 length of seta 3, setae 4 and 6 about 1/2 length of seta 3, seta 4 shorter than seta 6. Inner portion with four setae and small bottle-shaped sensillum. Scraping seta slender, sharp, flaming-torch setae of similar shape, decreasing in size basally; a small sensillum located between bases of setae 3 and 4. Three inner setae of similar length with filter plate setae. Gnathobase with two-segmented seta, sensillum and a small hillock distally. Filter plate IV with five setae.

Limb V ( Fig. 3 J–K). Preepipodite setulated, epipodite oval, with finger-like projection two times longer than epipodite itself. Exopodite of moderate size, separated into two lobes, with four plumose setae evenly decreasing in length basally, seta 4 short three times shorter than seta 1. Inner lobe moderately broad, widening distally. At inner face, two setae, distal seta 1.5 times longer than basal seta, large triangular hillock and a small sensilla-like structure are located near its base. Filter plate V absent.

Male. Only one specimen was available for this study. Body ( Fig. 1 K) lower than in female, height/length ratio about 0.66. Both eye and ocellus of size as in female, eye larger than ocellus.

Postabdomen ( Fig. 2 G) similar in shape to that of female, but more narrow, length about 3 maximum heighs. Gonopores located at some distance from the end of postabdomen. Ventral margin straight, with defined step at the location of gonopores. Distal margin convex, distal angle broadly rounded. Preanal angle well-defined, postanal angle not defined. Distal part of postabdomen two 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 short, shorter than preanal portion of postabdomen, basal spine straight, about 0.25 of claw length.

Antennule ( Fig. 2 H) short and moderately broad, length about two widths. All aesthetascs terminal, their number and length unclear due the poor preservation. Male seta arising at 1/3 length from tip, about 1/3 of antennule length.

Limb I ( Figs. 3 L–N) more massive than in female, copulatory hook U-shaped, its distal portion 1.5 times longer than basal one. A row of about 20 thick, moderately long 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, armed with thin setules. IDL without seta 1, setae 2 and 3 of similar length, much thinner and shorter than in female, male seta large, hook-like, almost as long as seta 3.

Size. In single studied females of first juvenile instar, length 0.34 mm, height 0.22 mm; in three females of second juvenile instar, length was 0.44–0.45 mm, height 0.29–0.31. In adult females length 0.49–0.64 mm, height 0.34–0.40 mm (according to Elías-Gutiérrez et al. (1997), length of adult females from Lago del Sol was 0.48–0.50 mm). Length of single studied adult male was 0.39 mm, height 0.26 mm.

Differential diagnosis. Alona manueli sp. nov. is a species of Alona s. lato of unclear affinities, it clearly differs from most species of Alona s. lato by very small marginal denticles of postabdomen and by two major head pores. In many features it is similar to European Alona intermedia , but clearly differs from it by the shape of its postabdomen (in A. intermedia it is widening distally, maximum height close to the end of postabdomen), proportions of antenna segments (in A. intermedia middle segments of both branches are much longer than two others), and by absence of filter plate V and limb VI. From species of affinis -group, which also have two head pores, A. manueli sp. nov. clearly differs by its smaller size, shape and armament of postabdomen, and armament of IDL (in species of affinis-group IDL seta 1 is very large, claw-like).

Figures

FIGURE 1. Alona manueli sp. nov. from Lago de la Luna Lake, volcano Nevado de Toluca, State of Mexico. A, juvenile female of instar I. B – С, juvenile female of instar II: B, lateral view. C, head shield. D – K, adult parthenogenetic female: D – E, lateral view (D—holotype). F, ventral margin of valves. G – I, head shield. J – K, head pores. L, adult male, outline of the body. Scale bars denote 0.1 mm for A – E, G – I, L and F, 0.05 mm for J – K.

FIGURE 2. Alona manueli sp. nov. from Lago de la Luna Lake, volcano Nevado de Toluca, State of Mexico. A – F, adult parthenogenetic female. A, posteroventral corner of valves. B, labrum. C – D, postabdomen. E, antennule. F, antenna. G – H, adult male. G, postabdomen. H, antennule. Scale bar denotes 0.05 mm.

FIGURE 3. Alona manueli sp. nov. from Lago de la Luna Lake, volcano Nevado de Toluca, State of Mexico. A – K, 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 – G, inner portion of limb III. H, exopodite of limb IV. I, inner portion of limb IV. J, exopodite of limb V. K, inner portion of limb V. L – N, limb I of adult male. L, ventral margin of the limb. M, IDL and copulatory hook. M, copulatory hook. Scale bar denotes 0.05 mm.