1. Sensory Structures in Tadpole Larvae of the Ascidians Microcosmus exasperatus Heller and Herdmania momus (Savigny).
- Author
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Svane, Ib and Young, Craig M.
- Subjects
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LARVAE , *PYURIDAE , *SEA squirts , *EPITHELIAL cells , *ANIMAL morphology - Abstract
In this paper we describe the larval morphology of two species from the ascidian family Pyuridae, Microcosmus exasperatus and Herdmania momus. with special emphasis on components of the cerebral vesicle. Larvae have not previously been described for any species in the large genus Microcosmus. Besides a difference in size (larvae of H momus are about 40% larger than those of M. exasperatus). larvae of the two species differ primarily in the number and arrangement of sensory structures. Both species possess a well-developed statocyte but only H. momus has an ocellus. The absence of an ocellus in M. exasperatus is unique among pyurid ascidians. An auxiliary vesicle was found situated on the left side of the cerebral vesicle in both species. However, unlike the larvae of H. momus and other pyurid species, there is no apparent communication between the auxiliary and cerebral vesicles of M. exasperatus. Epithelial cells in the auxiliary vesicles of both species carry modified cilia about 2 µm in diameter; auxiliary vesicles of H. momus also have simple cilia with axonemes in a 9 + 0 microtubule configuration. In H. momus the membranes of the epithelial cells are highly convoluted and extend into the lumen of the auxiliary vesiele. Morphological arrangements of auxiliary vesicles and globular cilia reported so far in ascidian tadpoles are contrasted and discussed. [ABSTRACT FROM AUTHOR]
- Published
- 1991
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