Miscellanea Zoologica Hungarica 11. 1997 (Budapest, 1997)

Hołyńska, M.: A new representative of Mesocyclops thermocyclopoides-circle (Copepoda: Cyclopoida) from India

basis; intercoxal sclerite of P4 with hair rows on the caudal surface; dorsum of genital double somite densely haired in proximal half only; armature of P4 coxa; copulatory duct with ring-like structures; furca with hairs on medial and ventral surface; pediger 5 laterally and dorsally haired; position and connection of copulatory pore with transverse ducts. The first six characters distinguish M. dadayi from its supposedly closest relative, M. dussarti Van de Velde, 1984. Discussion One of the characteristics of the Asian Mesocyclops fauna is the domination of the speciose and widely distributed Thermocyclopoides-ckcle. The species belonging to this complex share a polythetic character assemblage (small outgrowths on the intercoxal sclerite of leg 4; medial expansion of the leg 4 basis proximally and distally pilose; pediger 5 laterally pilose; receptaculum seminis with short and wide, not strongly curved lateral arms; no spine on the medial expansion of leg 1 basis; no spinule group proximal to the insertion of the exopod seta on the frontal surface of the antennary basis), and distinct rows of spinules on the frontal surface of the maxilla, a feature with relatively strong diagnostic value in itself (Holynski & Fiers 1994). It seems rather obvious, that the polythetic character-set is a mixture of features evolved at different times, partly perhaps even before the appearance of the direct ancestor of the Thermocyclopoides-ckcle. Within the Palaeotropical Mesocyclops the spiny armature on the maxillary coxa is present, with one exception, only in those species, where the above mentioned polythetic character set also appears, supporting the naturalness of the polythetically defined Thermocyclopoides-ckcle. The exception is M. ruttneri Kiefer, 1981: the specimens from South India - referred to in our previous paper (Holynski & Fiers 1994) as M. cf. papuensis - North Vietnam, and United States display great variability (no spinules, few small spinules, distinct rows of medium sized spinules) in this character. Phylogenetic relationships between M. ruttneri Kiefer, 1981 and Thermocyclopoides-ckcle, as in the genus Mesocyclops on the whole, are still unclear. Here I prefer the term "circle" (Holynski 1992) over "group", the latter is too neutral, not necessarily implying any phylogenetic relations among its members, and on the other hand the term "clade", which refers to strictly monophyletic (holophyletic) taxa. "Circle" can be applied to both holophyletic and paraphyletic groups. Besides those species mentioned before (Holynski & Fiers 1994), my later examinations have revealed M. granulatus Dussart & Fernando, 1988, M. isabellae Dussart & Fernando, 1988, M. tobae Kiefer, 1934, M. microlasiiis Kiefer, 1981, M. dissimilis Defaye & Kawabata, 1993, and M. dadayi sp. n. to be members of the circle. Although I did not observe original material of M. arcanus Defaye, 1995, M. notius, Kiefer, 1981, and M. australiensis (Sars, 1908), the published descriptions suggest that they belong to the complex as well. Structure of the Thermocyclopoides-ckcle is not known yet, therefore my hypotheses on the polarities have been based upon the character distribution in - and even outside - the whole Thermocyclopoides-ckcle rather than on one or two arbitrarily chosen "outgroup"species. Among the 14 described species of the Thermocyclopoides-ckcle, the irregular hairiness on dorsum of the pediger 5 and presence of hairs on proximal half of genital double somite