ULTRASTRUCTURE OF SWARMERS IN THE LAMINARIALES (PHAEOPHYCEAE). I. ZOOSPORES¹

Abstract

Zoospores of 17 species in 14 genera of Laminariales, collected in the northeast Pacific Ocean, were studied by electron microscopy. These zoospores are unique in the brown algae in lacking both an eyespot in the single chloroplast and any associated swelling at the base of the shorter, posterior flagellum. Spores of all species examined possess a distal whiplash portion on the longer, mastigoneme‐bearing anterior flagellum. This appendage may sometimes be as long as the mastigoneme‐bearing portion of the flagellum, but it is only seldom preserved in the preparations for electron microscopy. A microtubular cytoskeleton is probably responsible for maintaining the shape of the spore. It consists of a short band of about 10 microtubules between the two basal bodies, scattered tubules converging at the anterior of the spore, a band of 7–9 tubules directed anteriorly from the anterior basal body, and a band directed posteriorly from the posterior basal body. These anterior and posterior bands may form one continuous band looping around the periphery of the spore. Variation with possible taxonomic significance was found in the ultrastructure of vesicles which apparently contain adhesive material, and which are extruded through the plasmalemma when the zoospores settle.

Sperm Mitochondrial DNA Elimination in the Zygote of the Oogamous Brown Alga Undaria pinnatifida (Laminariales, Phaeophyceae)

“…In brown algae, mitochondria of motile cells like sperm, gametes, and zoospores have tube structures in their mitochondrial cristae (Henry and Cole 1982). In U. pinnatifida, sperm mitochondria with tubular structures were observed in the cytoplasm of the fertilized egg; these appeared to be digested.…”

Exposure to ultraviolet radiation delays photosynthetic recovery in Arctic kelp zoospores

“…In unicellular chlorophytes Dunaliella salina Teod., cells with larger Chl antenna was found to incur significantly higher rate of photodamage (Baroli and Melis 1998). Zoospores with only one chloroplast per cell (Henry and Cole 1982) are more susceptible to photodamage compared to multi-cellular life history stages. Incident UV-B radiation can easily penetrate through the thin plasmalemma of zoospores damaging the chloroplast.…”

Propagules of marine macroalgae: Structure and development

“…Flagella are ephemeral organelles and when motile cells cease movement they are usually withdrawn into the cytoplasm (Fig. 3) (J6nsson & Chesnoy, 1974;Swanson & Floyd, 1978;Henry & Cole, 1982). The axoneme is resorbed leaving the basal bodies which function as centrioles.…”

“…comm. ;9phillips et al, 1990;~°Henry & Cole 1982;HClayton 1990;~2Ramon 1973. 1963;2Evans & Christie 1970;3phillips 1988;Wan den Hoek 1978;5Burr & West 1970;6Meinesz 1980;7MacRaild & Wormers|ey 1974 Derbesiales, motile reproductive cells possess 1, 2 or 4 flagella (Tables II, III). Brown algal zooids are typically heterokont and, with the exception of some species in the Dictyotales, have two laterally inserted flagella.…”

“…In many red algae adhesive vesicles distinguished by having an electron dense core have been described (Tsekos, 1981(Tsekos, , 1983(Tsekos, , 1985Hymes & Cole, 1983;Delivopoulos & Kugrens, 1984). Discharge of peripheral adhesive vesicles, observed in a wide range of algal species, generally occurs on contact with a substratum (Micalef & Gayrat, 1972;Oliveira, Walker & Bisalputra, 1980;Henry & Cole, 1982;Pueschel & Cole, 1985).…”