Affiliation of the parasiteHerpodiscus durvillaeae(Phaeophyceae) with the Sphacelariales based on DNA sequence comparisons and morphological observations

Abstract

The phylogenetic affinities of the brown alga Herpodiscus durvillaeae, an obligate parasite of Durvillaea antarctica (Fucales, Phaeophyceae) endemic to New Zealand, were analysed using combined partial nuclear encoded ribosomal DNA (26S) and plastid encoded RuBisCO (rbcL) gene sequences. Results from phylogenetic analyses place this species within the order Sphacelariales. Molecular data were supported by two morphological features characteristic for the Sphacelariales sensu stricto: the presence of apical cells and the transitory blackening of the cell wall with sodium hypochlorite solution ('Eau de Javel'). However, the strongly heteromorphic life history distinguishes H. durvillaeae from all other members of the Sphacelariales of which the life cycle is known. This variability in life history provides a new systematic character for the order and should be taken into account in any comprehensive systematic revision of the Sphacelariales.

Algal Parasite Herpodiscus durvillaeae (Phaeophyceae: Sphacelariales) Inferred to have Traversed the Pacific Ocean with its Buoyant Host

“…, South , Adams , Heesch et al. ). The parasitic sporophytes are perennial, but emerge as epiphytic filaments during winter months, forming velvet‐like red‐brown patches on the surface of the host thallus (Heesch et al.…”

“…The parasitic sporophytes are perennial, but emerge as epiphytic filaments during winter months, forming velvet‐like red‐brown patches on the surface of the host thallus (Heesch et al. ). H. durvillaeae thalli grow outward in largely ring‐like circular or elliptical formations (Fig.…”

“…, South , Heesch et al. ) but its host, D. antarctica , is broadly distributed around the high latitudes of the Southern Hemisphere, occurring on most sub‐Antarctic islands and along the coasts of New Zealand and Chile (Fraser et al. ).…”

“…Herpodiscus durvillaeae specific primers were developed for chloroplast rbc L and ribosomal LSU based on published sequences (Heesch et al. , GenBank accessions ), and with particular reference to sequences from various Durvillaea species (from Fraser et al. ) to ensure that host DNA would not be amplified.…”

“…Herpodiscus durvillaeae is an endophytic phaeophycean parasite of southern bull-kelp, Durvillaea antarctica, with a heteromorphic life history, occurring in New Zealand (Lindauer et al 1969, South 1974, Adams 1994, Heesch et al 2008. The parasitic sporophytes are perennial, but emerge as epiphytic filaments during winter months, forming velvet-like red-brown patches on the surface of the host thallus (Heesch et al 2008). H. durvillaeae thalli grow outward in largely ring-like circular or elliptical formations (Fig.…”