Studies of the relationships between the ascidian Diplosoma virens and its associated microscopic algae. I. Photosynthetic characteristics of the algae.

Abstract

The microscopic algae contained within the cloacal cavity of the ascidian Diplosoma virens have a high photosynthetic capacity [up to 5.3 µgC (µg chl a)^-1 h^-1], giving thecolony a high photosynthesis: respiration ratio (maximum 8.0-8 5). Photosynthesis is saturated at a quantum flux density of 120 × 10¹⁵ quanta cm^-2 s^-1 (400-700 nm) and occurs at its maximum at temperatures between 30 and 35º C. The photosynthetic capacity is inhibited by chloramphenicol but not by cycloheximide. This is interpreted as indicating an affinity of these algae with the prokaryotes rather than the Chlorophyta, in spite of their possession of chlorophyll b (chlorophyll a : b ratio = 6.0) as an accessory pigment. In this and other respects the algae resemble those (Prochloron) described from other didemnid ascidians. Use of a buffered extraction medium has allowed separation from the animal tissue of photosynthetically active algal cells.