Redescriptions and SSrRNA gene sequence analyses of two marine species of aspidisca (Ciliophora, Euplotida), with notes on the morphogenesis in A. orthopogon

Abstract

Based on the living observation and silver impregnation methods, two poorly defined marine euplotid ciliates, Aspidisca orthopogon Deroux and Tuffrau, 1965 and Aspidisca aculeata (Ehrenberg, 1838) Kahl, 1932, from coastal waters near Qingdao (Tsingtao), northern China, were investigated. Improved diagnoses and morphometric data are provided for both species. As an additional contribution, the morphogenesis in Aspidisca orthopogon during binary fission was re-examined and can be summarized as follows: 1) the parental adoral zone of membranelles and paroral membrane are retained by the proter; 2) the oral primordium of the opisthe develops hypoapokinetally in a sub-surface pouch below the posterior part of the adoral zone of membranelles; 3) five frontoventral-transverse cirral anlagen are formed de novo, initially as primary primordia, and develop into 3:3:2:3:1 cirri from left to right respectively in both dividers; 4) the leftmost frontoventral cirrus is generated from an independently formed cirral anlage in both dividers.