GEOGRAPHICAL DIFFERENTIATION OF CYPR INUS (MESOCYPRINUS) MICRISTIUS:REGAN
YANG JUN-XING; CHEN YIN-RUI (Kunming Institute of Zoology, Academia Sinca, 650107)
The carp Cyprinus (Mesocyprinus) micristius Regan is a primitive species of thegenus Cyprinus. It is distributed only in the Dianchi Lake, Fuxian Lake and XingyunLake of Yunnan, China. Now the carp is extinct in the Dianchi Lake and theXingyun Lake, only a small population being survived in the Fuxian Lake. Basedon the data obtained from examination of 200 specimens and from monthly sur-vey in the Fuxian Lake in the duration of 28 monthes, the present paper deals withthe geographical differentiations in morphology, living space, feeding habit, age andgrowth, breeding biology. Morphological, ecological and distributional data indi-cate that Cyprinus (Mesooprinus) ml'cristius has differentiated into two subspecies,they are: C. (M. ) micristius micristius Regan and C. (M.) micristius fuxianensisYang et al. The former subspecies is endemic to the Dianchi Lake and the latterone is distributed in the Fuxian Lake and the Xingyun Lake. Subspecies ismorphologically differentiated mainly in body death, head length, interorbitalwidth, eye diameter, caudal peduncle and lateral line scales, predorsal scales,branched dorsal fin rays (Table I ). Morphological ) micristiusml'crl'stius is endemic to the Dianchi Lake which is a shallow lake with dense aquat-ic vegetation. In adaptation to manoeuvre flexibly in the dense aquatic vegetationof the Dianchi Lake, C. (M.) micristius micristius evolved a shorter.deeper body and caudal peduncle, a lagger head and eye, more branched dorsalfin rays (Table I ). By contrast, C. (M.) micristiusfuxianensis mainly lives in theFuxian Lake which is a deep lake with rare aquatic vegetation and it hascorrespondingly evolved a poor manoeuvring swimming function.The stomach contents of 42 specimens of C.(M.) mciristius fuxianensis con-sists mainly of mollusc, larvae of Chironomidae, zooplankton and filamentousalgae (Table 2, 3 ). The stomach contents of I I spedmens of C. (M.) micristiusmicristius consists mainly of shrimp, larvae of Chironomidae, and filamentousalgae (Table 2). It is obvious that subspecies are differentiated in staples of diets.Subspecific differentiations are also shown in age and growth. C. (M.) micrl'stiusfuxianensl's growes more quickly than C. (M.) micristius micristius (Table 4).C. (M. ) ml'crl'stius micristl'us layes eggs on sandy ground, with smaller ripeeggs and a higher relative feCundity (Table 5 ), being younger to reach primaryreproductive maturity. C. (M.) micristiusfuxlenensis layes eggs on aquatic plants,with larger ripe eggs and a lower relative feCundity (Table 5); being elder toreach primary reproductive maturity. All of these are subspedfic differentiations inbreeding ecology.In summary, the two subspaces are differentiated in morphology, living space,feeding habit, age and growth, breeding biology. All of these differentiations are re-sulted from geographical isolation and adaptation to different development process. of the lakes.