ZOOTAXAISSN 1175-5326 (print edition)

ISSN 1175-5334 (online edition)Copyright © 2013 Magnolia Press

Zootaxa 3647 (2): 390–400 www.mapress.com/zootaxa/ Article

http://dx.doi.org/10.11646/zootaxa.3647.2.10http://zoobank.org/urn:lsid:zoobank.org:pub:3EF22751-E494-4282-8E10-2374170ED150

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.

ARTEM Y. SINEV1 & EDYTA ZAWISZA2,3

1Department of Invertebrate Zoology, Biological Faculty, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow 119992, Russia. E-mail: artemsinev@yandex.ru2Instituto de Geofisica, Universidad Nacional Autónoma de México, Ciudad Universitaria, D.F., Mexico 3Institute of Geological Sciences, Polish Academy of Sciences, Warsaw, Poland

Abstract

Cladoceran communities of two lakes of Nevado de Toluca Volcano, Central Mexico, were studied. A new species of Aloninae, Alona manueli sp. nov., is described. It was previously confused with Palearctic Alona intermedia Sars, 1862, but clearly differs from it in the morphology of postabdomen, head shield and head pores, and thoracic limbs. Position of Alona manueli sp. nov. within the genus is unclear, it did not belong to any species-group within Alona s. lato. Other spe-cies recorded in the studied lakes are Alona ossiani Sinev, 1998, Alonella pulchella Herrick, 1884, Chydorus belonging to sphaericus-group, Eurycercus longirostris Hann, 1982 and Pleuroxus cf. denticulatus Birge, 1879.

Key words: cladocera, crater lake, Mexico, Neovolcanic Province, endemic, taxonomy

Introduction

Cladocera of Mexico have been intensively investigated during last decades, and the fauna of the region was recently reevaluated (Elías-Gutiérrez et al. 2008). One of the intensively revised groups is the subfamily Aloninae (Anomopoda: Chydoridae). Several new species and subspecies of the group were recently described from Mexico (Ciros-Pérez. & Elías-Gutiérrez 1997; Elías-Gutiérrez & Suárez-Morales 1999; Kotov et al. 2003; Dumont & Silva-Briano 2000; Elías-Gutiérrez & Valdes-Moreno 2008; Sinev & Silva-Briano 2012). But still, diversity of Mexican cladocera in general, including Aloninae, is underestimated (Sinev & Silva-Briano 2012). Some of Mexican populations of Aloninae are still presumed to be conspecific with Palearctic taxa. This contradicts to “Frey’s non-cosmopolitanism paradigm” (Frey 1982, 1987), now universally accepted by the experts in the cladoceran taxonomy (Kotov et al. 2010), and such taxa should be reevaluated. One of such Mexican doubtful taxa is Alona cf. intermedia, described by Elías-Gutiérrez et al. (1997), from Lago del Sol, State of Mexico as Biapertura intermedia. The description of this species leaves no doubt that this population is not conspecific to the European Alona intermedia Sars, 1962, as it strongly differs from it by the shape of postabdomen and head shield. This lake, together with smaller Lago de la Luna are located in the Nevado de Toluca volcano crater, at altitude 4620 m.a.s.l.

Cladocerans of both lakes were investigated by Elías-Gutiérrez et al. (1997), who reported Alona affinis(Leydig, 1860) and A. cf. setulosa Megard, 1967 from Lago de la Luna, and A. intermedia Sars, 1862 and Ilyocryptus sp. from Lago del Sol. The latter species was lately reveled to be a new species, Ilyocryptus nevadensisCervantes-Martínez, Gutiérrez-Aguirre, M. & Elías-Gutiérrez 2000, this taxon is supposed to be a local endemic (Cervantes-Martínez et al. 2000). Dimas-Flores et al. (2008) reported three species of Cladocera, Daphnia ambigua Scourfield,1947, Alona cf. setulosa and Alonella pulchella Herrick, 1884 from the both lakes, and Eurycercus cf. pompholigodes Frey, 1975 from Lago del Sol only. So far, it is the only record of Nearctic Alonella pulchella in Mexico, but no drawings of the species were provided. According to Bekker et al. (2012), Eurycercuspopulation from Lago del Sol belongs to E. longirostris Hann, 1982 instead of Eurycercus pompholigodes. Recent

390 Accepted by M. Alonso: 25 Mar. 2013; published: 9 May 2013

paleolimnological study of Lago de la Luna (Zawisza et al. 2012) revealed remains of five cladocera species in sediments—Ilyocryptus nevadensis, Alona sp., Daphnia of longispina-group, Alonella pulchella and Chydorus belonging to sphaericus-group.

The aim of present article was to study cladoceran fauna of the lakes Nevado de Toluca to clarify taxonomic status of Alona cf. intermedia populations.

Study site. Lago del Sol (Lake of the Sun) and Lago de la Luna (Lake of the Moon) are located approx. 90 km SW of Mexico City (19º06’13''N, 99º45’20''W) in the Nevado de Toluca volcano crater at high elevation (4,620 m.a.s.l.). According to geological studies (Bloomfield and Valastro 1979, Armienta et al. 2000) the volcano crater developed approx. 11,600 years ago, when the volcano was active for the last time. The lakes in question probably developed soon after this event. The modern climate at the peak of Nevado de Toluca is cold, with summer raining season. The mean annual temperature is 4oC, and the mean annual precipitation is approx. 1,250 mm. The vegetation surrounding the lakes is mainly composed of several species of tussock-growing grasses. In the lower part of the mountain, below the tree line (4,000 m.a.s.l.), the vegetation consists of Pinus and Abies forests (Caballero 1996, Gonzalez 1984). Lago del Sol is the largest lake in the crater, with a surface area ca. 17.5 ha. The maximum depth of the lake is approx. 12 m. The average pH is around 5.8–5.9, and the water conductivity is between 19 and 24 μS/cm. Lago de la Luna is a smaller and shallower lake, with a surface area of 2.5 ha and maximum depth of 8 m. The lake’s water is more acidic, with pH around 4.9, and water conductivity between 17 and 20 μS/cm. The water of both lakes is very clear and cold. The water temperature is quite similar throughout the year, fluctuating between 8 and 11°C. The Secchi Disk transparency usually reaches the bottom (Caballero 1996, Dimas-Flores 2005).

Material and methods

Samples were collected at the beginning of November 2011 by means of planktonic net (50 μm) from the littoral zone of both lakes. Sampling was done in four different sites in the case of Lago del Sol and two sites in case of Lago de la Luna. Immediately after sampling, zooplankton samples were put to plastic jar and preserved in the 70% ethanol. After field work (the same day) samples were moved to laboratory and kept in a fridge at temperature of +5ºC. Animals were selected from the sample under a binocular stereoscopic microscope, placed on slides (in a drop of a glycerol-ethanol mixture), dissected and studied under an optical microscope. Measurements were conducted using an eyepiece-micrometer. Drawings were made by means of camera lucida.

Abbreviations. In the illustrations and text: I–V = thoracic limbs I–V; as = accessory seta of limb I; cbs = copulatory brush seta; e1–3 = endites 1–3 of limb I; ep = epipodite; ex = exopodite; gfp = gnathobase filter plates of limbs II–V; il = inner lobe of limb V; IDL = inner distal lobe of limb I; IP = interpore distance (distance between anterior and posterior major head pores); ms = male seta of limb I; ODL = outer distal lobe of limb I; pep = preepipodite; PP = postpore distance (distance between posterior head pore and posterior border of head shield); s = sensillum.

In the list of collections: ZMMU—Zoological Museum of M. V. Lomonosov Moscow State University, Moscow, Russia.

Results

No specimens of Alona cf. intermedia were found in Lago del Sol, but numerous specimens of this taxon, and exuvia, were found in Lago de la Luna. Other species found in Lago de la Luna were Alonella pulchella and Chydorus sphaericus-group; in Lago del Sol: Alona ossiani Sinev, 1998, Chydorus sphaericus-group, Eurycercus longirostris Hann, 1982 and Pleuroxus cf. denticulatus Birge, 1879. Investigation of morphology of Alona cf. intermedia from Lago de la Luna confirmed their differences from Alona intermedia s. str., so a new species, Alona manueli sp. nov. is described.

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Taxonomy

Order Anomopoda Sars, 1865

Family Chydoridae Stebbing, 1902 emend. Dumont & Silva Briano, 1998

Subfamily Aloninae Dybowski & Grochowski, 1894 emend. Frey, 1967

Tribe Alonini Dybowski & Grochowski, 1894 emend. Kotov, 2000

Genus Alona Baird, 1843

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,

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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.

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.

Description. Parthenogenetic female. General. In lateral view body regular oval (Figs.1A–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. 1E) with 40–50 setae, about 10 anterior setae long, next 5–7 setae very short,

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followed by setae of moderate length, evenly decreasing in length posteriorly. Postero-ventral angle (Fig. 2A) 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.

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.

Head triangle-round in lateral view. In lateral view, rostrum short, pointed downward. Ocellus and eye of similar size. Shape of head shield (Figs. 1C, 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. 1I–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. 2B) 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. 2C, 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,

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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. 2E) 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. 2F) 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. 3A–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. 3C–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. 3E–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 3H–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. 3J–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. 1K) 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. 2G) 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.

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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.

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Postabdominal claw short, shorter than preanal portion of postabdomen, basal spine straight, about 0.25 of claw length.

Antennule (Fig. 2H) 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. 3L–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).

Discussion

Our study adds new data on cladoceran communities of the lakes in the crater of the Nevado de Toluca. Our data confirm the presence of Alonella pulchella here, morphology of studied specimens (Fig. 4A–D) fully agrees with the redescription of the species by Hann & Chengalath (1981). This is a southernmost record of the species and the only record for Mexico. Pleuroxus cf. denticulatus Birge, 1879 is recorded here for the first time, the species were already recorded for the region by Elías-Gutiérrez et al. (1997). The species is not revised at the moment, and exact data on its distribution is absent. The morphology of studied specimens of Pleuroxus cf. denticulatus (Fig. 4 E–H) agrees with that of other Mexican populations (see Elías-Gutiérrrez et al. 2008), but differs from populations from USA (see Flössner & Kraus 1977) in armament of postabdomen. The group of long setules at the distal angle of postabdomen (Fig. 4H) is not present in populations of P. denticulatus s. str. Future studies of this taxon from Mexico are needed to clarification of its status. Records of Alona affinis from the lakes belong to A. ossiani, Palearctic Alona affinis is not present in Mexico (Sinev & Silva-Briano 2012). No specimens of Alona setulosa were found during our study in both lakes, and paleolimnological studies in Lago de la Luna Luna revealed just one species of Alona, A. manueli sp. nov. in sediments (Zawisza et al. 2012, recorded here as Alona sp.). Outer morphology of A. setulosa (see Sinev & Silva-Briano 2012) is quite similar to that of Alona manueli sp. nov., and it is possible that records of A. cf. setulosa all belong to the latter species.

Our data fully confirm the independent status of Alona manueli sp. nov. It differs from Alona intermedia (see Alonso 1996; Hudec 2010) by the general shape and shape of postabdomen, by proportions of antennal segments (in A. intermedia middle segments of both branches are much longer than two others), by the presence of inner setae on endites of limb I, and by the absence of filter plate V and limb VI. Such differences suggest that Alona manueli sp. nov. is not closely related to A. intermedia, and similarities in armement of postabdomen in these species are convergent.

Taxonomic position of Alona manueli sp. nov. is unclear. It is close to Hexalona-branch of Alona s. lato, having main distinctive feature of the group, seven seta on exopodite 3, and numerous other features, like well-developed seta 1 on IDL, which separate it from the groups of Coronatella-branch. It clearly did not belongs to affinis-, costata- and guttata-groups, which have well-developed filter plate V and limb VI, as well as different morphology and armament of postabdomen (for characteristics of the groups see Van Damme & Dumont 2008a,

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Sinev 2008, 2009). Two other groups of Hexalona, quadrangularis (Alona s. str according to Van Damme & Dumont 2008b) and pulchella- groups, lack filter plate V and limb VI, but both of them, unlike Alona manueli sp. nov., have three major head pores, well-developed marginal denticles of postbdomen, and oval, not bilobed, exopodite V. Also, Alona manueli sp. nov. differs from all species of pulchella-group (see Sinev et al. 2012; Sinev & Silva-Briano 2012) by lateral pores located close to midline, by presence of seta “i” and inner setae on endites 1–2 on limb I, by setae 5–6 of exopodite 3 being of same morphology, and by male antennule without lateral aestetascs. From species of quadrangularis-group A. manueli sp. nov. also differs by smaller size, by ventral face of limb I with clusters of thin setules (in quadrangularis-group there are large single setules), by short acessory seta of limb II, and by the smaller size of exopodites III–V.

FIGURE 4. A–D, Alonella pulchella Herrick, 1884 from Lago de la Luna Lake, volcano Nevado de Toluca, State of Mexico, parthenogenetic female: A, lateral view. B, sculpture of valves. C, postero-ventral corner of valves. D, postabdomen. E–H, Pleuroxus cf. denticulatus Birge, 1879 from Lago del Sol lake, volcano Nevado de Toluca, State of Mexico, parthenogenetic female: E, lateral view. F, postero-ventral corner of valves. G, postabdomen. H, distal marginal denticles of postabdomen. Scale bars denote 0.1 mm for A, G and E, F, 0.05 mm for B–D, F, H.

In Hexalona-branch of Alona s. lato there are several species of same status as Alona manueli sp. nov., which did not fit any of established species-groups. Some of them, like A. manueli sp. nov. and Lake Baikal endemic A. setosocaudata Vasiljeva & Smirnov, 1967 (see Sinev & Kotov 2001) are probably strongly derived endemic products of local specialization. A. intermedia is distributed more widely, and probably consist of several sibling-species. Study of such species is essential for ongoing revision of the group.

Alona manueli sp. nov. is so far known only from two lakes within a single volcano crater, and at the moment of our sampling it was absent from one of them. Given relatively short time of lakes existence, it is unlikely that this species is a microendemic of Nevado de Toluca crater, and we expect it to be found in other high altitude lakes in the Neovolcanic province. Numerous endemic species of Alona s. lato and related genera were recently discovered in mountains of South and East Africa (Sinev 2006, 2008, 2009; Van Damme & Eggermonth 2011),

SINEV & ZAWISZA398 · Zootaxa 3647 (2) © 2013 Magnolia Press

South America (Sinev & Coronel 2006; Kotov et al. 2010) and Mexico (Sinev & Silva-Briano 2012). Our data confirms high level of endemism of cladocera in mountainous regions of subtropical and tropical areas.

Acknowledgments

We are grateful to Prof. N. N. Smirnov (Institute for Ecology and Evolution, RAS, Moscow) for the constructive comments and critique of the manuscript. The study was funded by a postdoctoral scholarship granted to the second author by the Universidad Nacional Autónoma de México and partially supported by the grant from Russian Foundation for Basic Research for the first author (grant 12-04-00207-а).

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