NEMATOCYST ANALYSIS OF CYANEA-CAPILLATA AND CYANEA-LAMARCKII (SCYPHOZOA, CNIDARIA)

Nematocysts of red-pigmented Cyanea capillata medusae and blue-pigment ed Cyanea lamarckii medusae from the Swedish west coast were examined by light and scanning electron microscopy. In addition to homotrichous isorhizas and heterotrichous microbasic euryteles, a new heterotricho us microbasic rhopaloid nematocyst was identified. Nematocyst nomencla ture is considered in the light of new SEM information; and changes in the definitions of isorhiza and anisorhiza nematocysts are suggested. In both species, the distribution of nematocysts on the marginal tent acles differed from that on the curtain-like oral-arms and exumbrella. On the tentacles the nematocysts occurred densely in batteries, but o n the oral-arms they were diffusely scattered or appeared in batteries of varied size; generally they were dense only at the oral rim or nea rby the rim. On the exumbrella nematocysts were loosely scattered or i n small batteries. Nematocysts were more dense at the margin of the be ll. Unexpectedly, nematocysts, particularly medium and large A-isorhiz as, increased in size with increasing size of the medusae. Differences in size and distribution between morphologically identical nematocyst s of the two Cyanea medusa species even of similar diameter were obser ved, thus strengthening the opinion that each is a valid species.