Miscellanea Zoologica Hungarica 11. 1997 (Budapest, 1997)

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

The form of leg 4 endopod in the females of the cyclopids and the form and setation of the female caudal rami in Baikalian harpacticoid copepods (Morarid) are suspected by Boxshall & Evstigneeva (1994) to be significant tactile part of the specific mate recognition system (SMRS). Gophen's observations (1979) on the mating process of "M. leuckarti" [it was later identified by Van de Velde as M. ogunnus Onabamiro, 1957 (Defaye 1995)] from Lake Kinneret show, that the male usually grasps with its geniculate antennulae the female at her furcal setae close to the rami at first, later his hold moves toward the genital segment, and finally he attaches to the fourth leg of the female. On the other hand, Mesocyclops species often show sexual dimorphism in both the caudal armature of the leg 4 coxa and the spinulation at the insertion of furcal setae. Sexual dimorphism of these features has also been observed in M. dussarti Van de Velde, 1984 and M. thermocyclopoides Harada, 1931 (Van de Velde 1984, Holynski 1994). Males of M. isabellae Dussart & Fernando, 1988 and M. dadayi sp. n. are still unknown. I suspect, that the spinule armature of the furcal rami and the spinule pattern on the leg 4 coxa of Mesocyclops female can also serve as tactile signals in the SMRS. If it is so, we should expect these characters to be similar (or identical) in the very closely related allopatric forms, but differentiated in the sympatic ones. M. dussarti Van de Velde, 1984 is a West African (Sahel) species with pluvial relict populations in Tassili-n-Ajjer, and a southern record from Lualaba - upper reach of R. Zaire - (Van de Velde 1984); M. dadayi sp. n. is known only from its Indian type locality; the area of M. isabellae Dussart & Fernando, 1988 includes the Indian subcontinent (Dussart & Fernando, 1988) and Sri Lanka (my unpublished data); there are uncertainties about the distribution of the genuine M. thermocyclopoides Harada, 1931 - I identified this species from Malaysia, Vietnam, Burma and Taiwan. The zoogeographical and morphological characteristics in this case just fit in the predicted way. To confirm the hypothesis about the function of these characters, it would be necessary to analyze the ornamentation of the leg 4 coxa and the furcal rami in other, supposedly closely related allopatric species-pairs. Of course, several other morphological structures on the furca, abdominal segments, and leg 4, can also play a more or less significant role in the SMRS, modifying the importance of any single feature in itself. Key to the Afro-Asian Mesocyclops belonging to the Thermocyclopoides-circle. (M. arcanus - supposed also to belong to the Thermocyclopoides-ckc\e, but unknown to me in nature - is not included in this key. Another, not yet described species from South-India and Sri Lanka, closely related to M. woutersi and M. dissimilis, has been omitted as well.) 1. Pediger 5 laterally naked 2 - Pediger 5 laterally pilose 3 2. Medial expansion of leg 4 basis distally with minute spinules on caudal surface; dorsal furcal seta shorter or only a little longer than posterolateral one M. kieferi Van de Velde, 1984 Transverse ducts of female genital system ("posterior margin of the proximal part of the receptaculum seminis") directed at acute angle ("V-shaped") to one another before the connection with copulatory duct; copulatory duct curved like a comma; caudal surface of the antennary basis with simple ("leuckarti-type") spinule ornamentation: abdominal segments dorsally and ventrally adorned with rows of spinules. Distribution: sub-Saharan Africa, Yemen, Israel, Sri Lanka, Brazil? (probably recently introduced). - Medial expansion of leg 4 basis distally with hairs; dorsal furcal seta at least twice longer than posterolateral one M. tobae Kiefer, 1934