Electron microscopical investigations on two loricate choanoflagellates (Choanoflagellida),Calotheca alatagen. et sp. nov. andSyndetophyllum phyllumgen. et comb, nov., from Indo-Pacific localities

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Abstract
CALOTHECA alata gen. et sp. nov. and SYNDETOPHYLLUM pulchellum gen. et comb. nov. [Parvicorbicula pulchella] are loricate choanoflagellates whose loricae are built up only from broad costal strips. The lorica of both taxa consists of 2 transverse costae and 2 sets of longitudinal costal strips. S. pulchellum further possesses a compound pedicel mostly formed by 4 diverging costal strips that are attached to the posterior lorica end. The most interesting new observation is the morphological adaptations towards linkage of costal strips to each other. In C. alata one end of each anterior transverse costal strip is shaped so as to secure the neighboring costal strip in a fixed position, whereas in S. pulchellum and anterior groove of each longitudinal costal strip helps to establish a firm contact between anterior transverse and longitudinal costal strips. Both taxa described offer points of resemblance with the recently established genus Stephanacantha, which is typified by Stephanacantha campaniformis. The locations at which C. alata and S. pulchellum have been found suggest that both species are confined to warmer waters of full salinity. The known lower temperature limit of C. alata is 15.degree. C, whereas that of S. pulchellum is 10.degree. C.