Premium
Nuclear Behavior and Morphogenetic Changes in Fission and Conjugation of Aspidisca costata (Dujardin)
Author(s) -
DILLER WILLIAM F.
Publication year - 1975
Publication title -
the journal of protozoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 0022-3921
DOI - 10.1111/j.1550-7408.1975.tb05855.x
Subject(s) - biology , nucleus , fission , contractile vacuole , ciliata , anatomy , cytoplasm , microbiology and biotechnology , genetics , vacuole , physics , quantum mechanics , neutron , protozoa
SYNOPSIS Nuclear behavior and accompanying cytoplasmic changes have been traced in conjugation and binary fission in Aspidisca costata , a fresh water hypotrich. Cases of autogamy in singles also have been found. In conjugation the animals pair with left ventral sides apposed, at an angle of ∼ 100°, connected by a broad bridge. After 2 maturation divisions 4 potential gametic nuclei are formed. Thereafter 1 of 2 alternative plans is followed. The essential difference between them is the occurrence in Scheme B of degeneration of 2 products of the 2nd prezygotic division, thus reducing to 2 the 4 potential gametic nuclei–all viable in Scheme A. Single or double synkarya are thus generated, respectively, in each conjugant, certain of them necessarily by autogamy. After 1 or 2 postzygotic divisions, 4 final nuclei are formed: 1 macronuclear anlage, 2 micronuclei, and a degenerate nucleus. The exconjugants at 1st are astomatous, although a new complete set of cirri (exclusive of the anterior “tooth”) arises during conjugation. A later reorganization in the exconjugants must restore the buccal apparatus and probably also replaces the cirri and tooth. The morphogenetic changes in fission have been observed. All the cirri are replaced, in 2 sets, at each cycle. These originate in a single locus, a pouch anterior to the contractile vacuole. A new adoral zone of membranelles (AZM) arises for the opisthe, as a new tooth. The old AZM and the old tooth are retained by the proter. It is suggested that the tooth is the homolog of the 1/I cirrus of other hypotrichs.