THE ECOLOGY OF CHONDRUS CRISPUS AT PLYMOUTH, MASSACHUSETTS. I. ONTOGENY, VEGETATIVE ANATOMY, REPRODUCTION, AND LIFE CYCLE

Carpospores and tetraspores germinate and the germlings develop similarly. A prostrate holdfast of regular or irregular outline is formed if the spore makes direct contact with the substrate. If not, rhizoids grow from the few-celled germling unilaterally in no apparent relation to light or gravity, forming a prostrate holdfast if they encounter a solid substrate, and, in any case, eventually an erect shoot of different anatomy. Tetrasporophytes have been grown to reproductive maturity from single spore cultures in the laboratory. The ontogeny of the procarp and subsequent postfertilization events are described from field material. Only a single putative male plant was found when plants bearing procarps were numerous at Plymouth. Evidence from this study and from other reported observations places in doubt the expected role of fertilization in the diphasic, cytological alternation of Chondrus. CHONDRUS CRISPUS IS PLACED among the diplobiontic red algae (Rhodophyta). It is generally believed to be morphologically triphasic and cytologically diphasic, with free living gametophytic and sporophytic generations of similar size and structure (MacFarlane, 1968). The third phase, the carposporophyte, is diminutive and produced within the tissues of the female gametophyte. The gametophytic generation is assumed to be heterothallic or dioecious, with separate but morphologically similar male and female plants. Thus, in nature, one expects to find in time, in any well established population, three similar but distinct types of plants: (1) the male gametophyte, forming spermatangia and releasing spermatia; (2) the female gametophyte, forming carpogonia; and (3) the tetrasporophyte, forming and releasing tetraspores. Through a complicated series of postfertilization events, the carposporophyte is produced within the tissues of the female gametophyte, and forms and releases carpospores. The gametophytes are monoploid; the carposporophyte and tetrasporophyte are diploid, and meiosis is assumed to occur in the formation of tetraspores in the normal expression of the full cycle. Chondrus crispus yields hydrocolloids of commercial importance. Despite its usefulness to man, its full life history has not yet been securely elucidated. Various published observations sug1 Received for publication 3 October 1972. This work was supported in part under contract with the Raytheon Environmental Research Laboratory, New London, Connecticut. 2 Present address: Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543. The data in this paper are from part of a Ph.D dissertation submitted to Cornell University in 1971. gest anomalies in the cycle from that generalized above. As part of a detailed study of Chondrus crispus in the laboratory and in the field at Plymouth, Massachusetts (Prince, 1971; Prince and Kingsbury, 1973), opportunity was presented to make observations of significance toward a fuller understanding of the ontogeny, anatomy, and life cycle of Irish Moss on the North American east coast. The frequency and methods of sampling the natural population for reproductive analysis and the detailed culture conditions employed in growing the spores are described elsewhere in the series (Prince and Kingsbury, 1973). ONTOGENY FROM SPORE TO MATURE THALLUS -Carpospores and tetraspores obtained from nature were allowed to attach to glass slides. Sporelings were grown at 12 C, approximately 130 ft-c illumination, and under a photoperiod of 16 hr light, 8 hr dark. Spores are released as single, separate cells; tetraspores are 3-5 ,u smaller in diam than carpospores. Both types of spores have a delicate wall enclosing a granular protoplast containing a single, parietal, dissected rhodoplast and a central nuclear region as seen under a compound microscope (Fig. 1). Germination and early ontogeny of Chondruts spores have been described by Chemin (1937), Chen and McLachlan (1972), Ring (1970), Rosenvinge (1931), and Weber (1960). The material from Plymouth agrees generally with the earlier descriptions; we are able to present some additional details. There are two basic developmental patterns depending on whether the spore makes firm contact with the substrate or not. Carpospores and tetraspores behave similarly. Spores which make an initial firm attachment to