Codiolum

Abstract: The internal transcribed spacer regions of the nuclear ribosomal DNA cistron of green algal endophytes, previously identified as Chlorochytrium inclusum Kjellman and Codiolum petrocelidis Kuckuck, were sequenced. Culture studies have implicated marine Chlorochytrium and Codiolum-like cells in the life histories of a number of macrophytic green algae. The identity of the endophytes was resolved by comparing DNA sequences from unicells endophytic in the foliose red alga Mazzaella splendens (Setchell et Gardner) Hommersand and in the crustose phase of Mastocarpus papillatus (J. Agardh) Kylin, with sequences from species of Acrosiphonia, Urospora, Ulothrix, and Monostroma. All endophyte isolates were more closely related to species of Acrosiphonia than to those of Urospora, Ulothrix, or Monostroma. The results support previous culture studies, and conclusively identify the endophytes obtained in the field as alternate life history phases of one or more Acrosiphonia species in southern British Columbia, Canada.

Abstract: Culture studies on the morphology, development and, in some cases, on the life-histories of green shell-boring algae, have shown that in Britain there are at least six species which could be confused under the name Gomontia polyrhiza Born, et Flah. Of these six species it has been possible to identify only four, namely Eugomontia sacculata and Entocladia perforans and Codiolum stages in the life-histories of Codiolum polyrhizum and Monostroma grevillei. The possibility that there are as yet unidentified life-histories involving more shell-boring Codiolum stages has been suggested.

Abstract: We investigated the host specificity of Acrosiphonia's (Codiolales, Chlorophyta) endophytic sporophyte phase, previously identified as Chlorochytrium inclusum and Codiolum petrocelidis. In southern British Columbia, Canada, 'Chlorochytrium inclusum' is abundant in the foliose red alga, Mazzaella splendens, whereas 'Codiolum petrocelidis' densely colonizes the red algal crust, Petrocelis franciscana. Examination of foliose and crustose algae revealed a wide range of alternate hosts for Acrosiphonia sporophytes. Three foliose red algae, M. heterocarpa, M. sanguinea and Sparlingia pertusa, and two crustose algae, Ralfsia pacifica and Hildenbrandia occidentalis, are newly reported hosts for 'Chlorochytrium' and 'Codiolum'. This is the first study to report 'Codiolum' colonization of a brown alga (= Ralfsia), and foliose brown and green algae have never been reported to be colonized by 'Chlorochytrium'. 'Codiolum' demonstrated a greater affinity for Petrocelis than for other coexisting crustose algae, and 'Chlorochytrium' colonized some foliose red algal species more frequently than others. Endophyte density data suggest that variations in structural composition among host species (i.e. how closely appressed the filaments are in crusts, and the compactness in the cells of the cortex and medulla of foliose red algae) may be important in determining the ease of penetration by the endophyte. Host cell wall composition is suspected to play a role in preferential colonization by 'Chlorochytrium'. Carrageenophytes and carragar-producing hosts were colonized by higher densities of 'Chlorochytrium' than were agarophytes. The hypothesis that host life history phases might be differentially susceptible to colonization by endophytes was not supported in our study; among host species with an alternation of generations neither the gametophytes nor the sporophytes seemed to be consistently more heavily colonized.

Abstract: This study employs molecular and field sampling techniques to understand the complex life history of the filamentous green alga, Acrosiphonia, in southern British Columbia, Canada. The DNA sequences of the nuclear ribosomal internal transcribed spacer (ITS) regions conclusively identify the unicellular green algal endophytes, 'Chlorochytrium inclusum' and 'Codiolum petrocelidis', as the alternate life history phases of one or more Acrosiphonia species. 'Chlorochytrium inclusum', a spherical unicell, was found abundantly in the foliose red alga Mazzaella splendens, whereas 'Codiolum petrocelidis', a stalked unicell, densely colonises 'Petrocelis franciscana' (= crustose tetrasporophytic phase of Mastocarpus papillauts). The DNA sequence data supported previous culture studies and Kornmann's hypothesis that the two morphologically different endophytes are alternate phenotypes of the sporophyte of a single Acrosiphonia species. The relationship of Acrosiphonia's endophytic sporophyte and filamentous, free-living gametophyte in nature revealed similar dynamics for three environmentally variable field sites. Filamentous Acrosiphonia plants were seasonally abundant (spring and summer) with fertile cells developing almost immediately after Acrosiphonia's appearance in the rocky intertidal zone. The unicellular sporophytes colonised M. splendens and 'Petrocelis' one to three months later, and showed higher tolerance to abiotic factors than Acrosiphonia's gametophyte: high summer temperatures (which correlated with death of the filamentous free-living plants) were survived and they overwintered in their hosts. Endophytes matured primarily in winter, zoospore release occurred throughout winter and spring and Acrosiphonia's life cycle is completed with subsequent zoospore germination and establishment of filamentous gametophytic plants. The two red algal hosts, M. splendens and 'Petrocelis1, were abundantly available for endophyte colonisation in spring and summer. A number of factors, e.g. herbivory, winter storms and senescence, however, were identified to produce fluctuating seasonal abundance patterns of the hosts, thus potentially affecting endophyte survival. I suggest the endophytes have evolved a strategy whereby duration in the host is synchronised with seasonality of the host. An investigation of possible hosts for Acrosiphonia's sporophyte established a wide range of hosts. However, 'Codiolum' showed a greater affinity for 'Petrocelis' than for other crusts, and 'Chlorochytrium' colonised foliose red algae characterised by loosely compacted cells in the cortex and medulla and carrageenansand carragars as cell wall constituents e.g. M. splendens, M. heterocarpa and Schizymenia pacifica, more readily than others. A bet-hedging strategy is proposed for Acrosiphonia's life history. Not only have two morphologically different phases adapted to a seasonally variable environment, but the sporophytic phase of at least one Acrosiphonia species can colonise two alternate hosts (crustose and foliose red algae), and low host specificity is evident for both endophytes.