ISSN:
1432-234X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary Phyllodoce trochophores have a system of large, multipolar, nerve-like cells similar to the larval reticulum of the much-studied larva of Lopadorhynchus. The Phyllodoce reticulum is described here by means of light and electron microscopy and Golgi-Cox preparations. The cells appear to be secretory, and contain numerous large vesicles approximately 1 ώm in diameter. Their nuclei are large and distinctive, with a dense, granular nucleoplasm containing unusual hollow tubules, 40 nm in diameter, arranged in tangled masses and parallel arrays. The cells are nerve-like in that they possess surface processes that ramify irregularly throughout the larval tissues and thinner, basal processes that run along the larval nerves. They differentiate in close association with nerve cells of conventional type, the principal centres being in the apical region, on either side of the apical organ, and in the oral region, on either side of the mouth. The latter are centres of nerve differentiation in species with a metatroch. Phyllodoce larvae lack a metatroch, but the band itself could have been lost secondarily during evolution without loss of the neural elements associated with it. The precise function of the reticular system is not known. Basal processes connect it to the larval nerves, suggesting its cells receive neural input and, presumably, release their secretion from surface processes. There is no obvious evidence of secretory release during the larval phase, but the system disappears entirely at metamorphosis, suggesting a role in this process, possibly related to the histolysis of larval tissues.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00312215
