Observations on marine Chaetophoraceae (Chlorophyta) III. The structure, reproduction and life history of Endophyton ramosum

Abstract

Endophyton ramosum, an endophytic marine chaetophoracean alga endemic to the northern Pacific Ocean, has been studied using herbarium, field-collected and cultured specimens. It is distinct from other marine chaetophoracean taxa because of its strictly endo-phytic habit, unique vegetative structure and absence of pseudoparenchyma and setae under all growth conditions tested. The alga is typified from material found growing in Iridaea flaccida (Rhodophyta, Gigartinales); its host range is much narrower than previous reports have indicated. Some isolates of the alga have a life history involving an isomorphic alternation of phases, with quadriflagellate zoospores and biflagellate anisogametes, while other isolates have an asexual life history, producing quadriflagellate zoospores only. The life history, and the structure and developmental patterns of the sporangia and gametangia, are nearly identical to those previously observed in several other marine chaetophoracean species. Endophyton ramosum belongs to a marine chaetophoracean assemblage that is closely related to the Ulvaceae on the basis of the structural and reproductive characteristics of its members.