Eugene N. Kozloff

POST-COPULATORY STORAGE OF SPERM IN THE SEMINAL BURSA OF THE ACOEL FLATWORM OTOCELIS LUTEOLA

Summary Copulation in the acoel Otocelis luteola may result in mutual or one-sided insemination. Fifty specimens cultured with a species of Navicula were allowed to mate in pairs for a period of 6 h, 50 were allowed to mate in pairs for 24 h, and nine were allowed to mate freely for 24 h. All wows were then isolated in separate containers that were examined at frequent intervals in order to record the number of eggs and young. The number of progeny produced by worms that had been inseminated ranged from 1 to 65, and one worm had progeny as late as 55 days after mating. This study shows that O. luteola is able to store viable sperm in its seminal bursa for several weeks.

Association and distribution of the ciliate Orchitophrya stellarum with asteriid sea stars on the west coast of North America

The association of the scuticociliate Orchitophrya stellarum with 3 species of asteriid sea stars from the west coast of North America was studied by flushing the gonopore region with seawater and spawning the sea stars, along a latitudinal gradient of 2549 km between Pigeon Point, California, and Kodiak, Alaska. Asterias forbesii and A. rubens from the Isles of Shoals, New Hampshire (east coast), were also sampled. The ciliate was found on the aboral surface of both sexes of reproductively ripe Evasterias troschelii, Leptasterias spp., and Pisaster ochraceus with a maximum intensity of association occurring at Cape Arago, Oregon, and Clallum Bay and Manchester Dock, Washington. A survey of gonad smears and hematoxylin and eosin-stained sections indicated that the ciliate was only present in males. Spring-spawning E. troschelii and P. ochraceus are more negatively impacted by the ciliate than are winter-spawning Leptasterias spp. as judged by a skewed sex ratio and sex size differences, which may be associated with seasonal differences in water temperature affecting the growth rate of O. stellarum. The external morphology of O. stellarum appears to be similar throughout the geographical range surveyed.

Monoxenic cultivation of an acoel turbellarian, Parotocelis luteola Kozloff

Abstract Twelve species of diatoms, grown bacteria-free in enriched sea water, have been tested individually for their capacity to support the growth and reproduction of the acoel Parotocelis luteola. Two pennate diatoms, Navicula pavillardi and Nitzschia dissipata, proved effective, permitting indefinite cultivation. At temperatures between 19 and 21°C, P. luteola attains sexual maturity in three weeks. This acoel is among the few invertebrates other than protozoa which have been successfully maintained under monoxenic conditions, and is the only turbellarian which has been so cultivated.

Differentiation, dedifferentiation, and redifferentiation of reproductive structures of the acoel flatworm Otocelis luteola, and notes on longevity of this species

Summary The acoel Otocelis luteola, when cultivated with either of two species of Navicula, reaches maximum size and sexual maturity in 13 to 20 days. The proximal portion of the vagina and its opening are the first reproductive structures to appear. When a small invagination of the ventral epidermis forms the definitive genital pore and genital atrium, the opening of the vagina is displaced to the dorsal side of the atrium. The male copulatory organ, an eversible cirrus that will occupy part of the seminal vesicle and join the genital atrium, develops soon afterward, and the distal portion of the vagina, apparently without a lumen, becomes evident. After sperm have been formed, they are delivered by right and left channels to the seminal vesicle; a conspicuous sperm-filled space thus develops around the cirrus. The sclerotized nozzle of the seminal bursa is distinct by this stage, and enlarging oocytes soon become conspicuous. During final stages of differentiation, oocytes enlarge further. The granule-filled distal portion of the vagina arches over the seminal vesicle, reaching the seminal bursa. In a worm that has been inseminated, active sperm will be seen in one or more spaces within the bursa, which is otherwise rather vaguely delimited. If a mature specimen is starved, it regresses to a stage similar to that of one that has just hatched. Most reproductive structures are resorbed in an order inverse to that in which they differentiated. The cycle of differentiation and dedifferentiation has been repeated as many as seven times, and can perhaps be repeated indefinitely. Furthermore, some mature worms, after being isolated, remained normal for two years and were sexually competent when mated.