DESCRIPTIONOF ILYOCRYPTUSNEVADENSIS (BRANCHIOPODA, ANOMOPODA),A NEWSPECIESFROM A HIGHALTITUDECRATER LAKEINTHEVOLCANONEV ADODETOLUCA,

BY

ADRI` NCERVANTES-MARTÍNEZ, MARTHA GUTIÉRREZ-AGUIRRE andMANUEL ELÍAS-GUTIÉ RREZ 1) El Colegiode laFrontera Sur, Unidad Chetumal, Km 2CarreteraChetumal-, ZonaIndustrial #2, Chetumal, 77000 , Mexico

ABSTRACT

Anewspecies of acladoceranfrom a crater-lake,located at 4120m a.s.l.in the volcano Nevado deT oluca,Mexico, is here described. It belongs to the genus Ilyocryptus ,andis distinguished mainly bya combinationof features,including an incomplete moulting; the anal opening is locatedon the distalend of the postabdomen, which is armed with moveable lateral spines along most of its length; andwith no lobe formation. The shell bears bifurcate defensive spines. This record constitutes the ŽrstŽ ndof an ilyocryptid in a highaltitude crater-lake. This record also increases the number of speciesknown from Mexico to three, and to ninein theNew World.Most of theAmerican forms differfrom the European ones, such conŽ rming again the non-cosmopolitanism of most of these cladocerans.

RESUMEN

Se describeuna nueva especie de cladócero procedente de un lagocrá ter, localizado a 4120metros sobreel nivel del mar en elvolcá n Nevadode T oluca,Mé xico. Pertenece al gé nero Ilyocryptus y se distingueprincipalmente por una combinació n decaracterísticas que incluyen una muda incompleta; laabertura del ano localizada en el ladodistal del postabdomen, el cual se encuentra armado con espinasmó viles laterales a lolargo de la mayor parte de su longitud y sinformació n deló bulos dorsales.En la concha se observan espinas defensivas bifurcadas. Estos organismos constituyen elprimer registro de un iliocrí ptido en un lago crá ter de gran altitud e incrementanel nú mero de especiesconocidas para Mé xico a tres.En el caso del nuevo mundo alcanza nueve, la mayoría de ellasdiferentes a laseuropeas, por lo que se conŽ rma una vez má s elno cosmopolitanismo de la mayoría deestoscladó ceros.

1) Correspondingauthor; e-mail: [email protected] c KoninklijkeBrill NV ,Leiden,2000 Crustaceana 73(3):311-321 ® 312 A.CERVANTES-M.ET AL.

INTRODUCTION Incomparison with othercladocerans, ilyocryptids havereceived little attention bycladocerologists. Theywere part ofmacrothricids until the family Ilyocryptidae was proposedrecently bySmirnov (1992 ).It nowincludes onlythe genus Ilyocryptus ,basedon the presenceof abi-segmentedŽ rst antenna,a uniquefeature amongcladocerans. The genus has beenknown for about 150 years (Štifter, 1991). Sofar, nine species havebeen reported from Europe (Mordukai-Boltovskoi & Chirkova,1973; Negrea, 1987; Š tifter, 1988,1991; Smirnov, 1989; Alonso, 1996): Ilyocryptus acutifrons G.O.Sars, 1862; I. agilis Kurz, 1878; I. sordidus (Liévin, 1848); I. cornutus Mordukhai-Boltovskoi& Chirkova,1972; I.alexandrinae Negrea,1987; I.silvaeducensis Romijn,1919; I. spinosus Stifter, 1988; I. cuneatus Stifter, 1988;and I.raridentatus Smirnov,1989. Additionally ,Gündü z (1990, 1996)describedtwo more species fromTurkey ( I. samsuni and I.anatolicus ) and conŽrmed the presenceof I. sordidus inthat country. Ilyocryptus vitali Chirkova, 1982was describedfrom the KolaPeninsula, Russia. Recently, I. smirnovi Kotov &Timms, 1998was discoveredin Australia. Sevenspecies are knownfrom North America (Williams, 1978;Š tifter, 1988;and Elí as-Gutié rrez et al., 1997): I. agilis; I. sordidus; I.brevidentatus Ekman,1905; I. cuneatus; I. gouldeni Williams, 1978; I. spinifer Herrick,1882; and Ilyocryptus sp.Elí as-Gutié rrez et al., 1997.The last recordhas beenassigned to the newspecies describedhere. From South America, three additional species havebeen reported ( I.brevidentatus , I. elegans Paggi, 1992, and I.paranaensis Paggi,1989). European species, suchas the Žrst three reportedfrom North America, need further revision, because non-cosmopolitanism has beenestablished forchydorids (Frey ,1987)andthen extended to macrothricids andilyocryptids (Frey,1988; Š tifter, 1988;Kotov & Timms, 1998).In Mexico, recordsare conŽned to I. spinifer anda taxonrelated to I. agilis,accordingto Elí as- Gutiérrez et al. (1999).In this paper,a newspecies of Ilyocryptus is described.It seems to berelated to I.brevidentatus ,originallydescribed from South America.

MATERIAL AND METHODS Faunasamples werecollected fromthe littoral zoneof lake LaLunaon June 4, 1994.Up to 200l ofwater wereŽ ltered using50 mmmesh planktongauze. Samples wereŽ xedin 4%formaldehyde solution. The organisms weredissected with tungstenneedles. Drawings were made with the aid ofa camera lucida attached to aNikonLabophot-2 microscope. LakeLa Lunais located in the crater ofthe volcanoNevado de ,State ofMexico, Mexico (19 ° 06¢13¢¢N 99° 45¢20¢¢W)at analtitude of4680 m above sea level. It is acircular formationwith the followingenvironmental parameters