Harveyella Mirabilis Research Articles

Molecular phylogenetics supports a clade of red algal parasites retaining native plastids: taxonomy and terminology revised.

Parasitism is a life strategy that has repeatedly evolved within the Florideophyceae. Historically, the terms adelphoparasite and alloparasite have been used to distinguish parasites based on the relative phylogenetic relationship of host and parasite. However, analyses using molecular phylogenetics indicate that nearly all red algal parasites infect within their taxonomic family, and a range of relationships exist between host and parasite. To date, all investigated adelphoparasites have lost their plastid, and instead, incorporate a host-derived plastid when packaging spores. In contrast, a highly reduced plastid lacking photosynthesis genes was sequenced from the alloparasite Choreocolax polysiphoniae. Here we present the complete Harveyella mirabilis plastid genome, which has also lost genes involved in photosynthesis, and a partial plastid genome from Leachiella pacifica. The H.mirabilis plastid shares more synteny with free-living red algal plastids than that of C.polysiphoniae. Phylogenetic analysis demonstrates that C.polysiphoniae, H.mirabilis, and L.pacifica form a robustly supported clade of parasites, which retain their own plastid genomes, within the Rhodomelaceae. We therefore transfer all three genera from the exclusively parasitic family, Choreocolacaceae, to the Rhodomelaceae. Additionally, we recommend applying the terms archaeplastic parasites (formerly alloparasites), and neoplastic parasites (formerly adelphoparasites) to distinguish red algal parasites using a biological framework rather than taxonomic affiliation with their hosts.

A PHYLOGENETIC STUDY OF PARASITIC GENERA PLACED IN THE FAMILY CHOREOCOLACACEAE (RHODOPHYTA)1

Red algal parasites are common and have a unique type of development in which parasite nuclei are transferred to host cells and “control” host cell development. Previous phylogenetic studies have concentrated on parasites closely related to their hosts, termed adelphoparasites. A second set of parasites, usually classified in a different family or tribe from their host, termed alloparasites, have not been studied phylogenetically. This study concentrates on the wholly parasitic family, the Choreocolacaceae (Gigartinales). Using small subunit rDNA sequence data, we found that all the parasites studied are within the same family as their host. Our data support the placement of Holmsella, species of which parasitize Gracilaria and Gracilariopsis, in the order Gracilariales and suggest that Holmsella is an old parasitic genus. Most other species of the Choreocolacaceae parasitize species of the Rhodomelaceae. The one exception is the hyperparasitism between Harveyella mirabilis (Reinsch) F. Schmitz et Reinke (Rhodomelaceae) and the parasite Gonimophyllum skottsbergii Setchell (Delesseriaceae). The parasites Bostrychiocolax australis Zuccarello et West and Dawsoniocolax bostrychiae (Joly et Yamaguishi‐Tomita) Joly et Yamaguishi‐Tomita are placed within the tribe Bostrychiae as are their hosts. Harveyella mirabilis has a single origin and has switched hosts several times during its passage between the Atlantic and Pacific Oceans. Evidence does not support the continued recognition of the family Choreocolacaceae. Our results also indicate that the distinction between adelphoparasites and alloparasites is unwarranted, with a continuum between newly evolved parasites closely related to their hosts and parasites less closely related to their hosts.

Morphology and systematics of the red algal parasite Dawsoniocolax bostrychiae (Choreocolacaceae, Rhodophyta)

Abstract The vegetative and reproductive development of the parasitic red alga Dawsoniocolax bostrychiae (Joly et Yamaguishi-Tomita) Joly et Yamaguishi-Tomita, a parasite on Bostrychia, was studied. The thallus is a colourless multiaxial pustule which forms secondary pit connections with cells of its host. Reproductive structures develop from outer cortical cells. Tetrasporangia are tetrahedrally or cruciately cleaved. A four-celled carpogonial branch is borne on an intercalary supporting cell, which also functions as the generative auxiliary cell. After fertilization, the carpogonium fuses with the supporting (auxiliary) cell. The mature carposporophyte consists of a central fusion cell supporting a hemispherical cluster of gonimoblast filaments bearing terminal carposporangia. Carposporophyte development is similar to Harveyella mirabilis (Reinsch) Schmitz et Reinke and Leachiella pacifica Kugrens. Spermatangia develop in globose clusters formed by divisions in several planes of the spermatangial initia...

The structure and formation of host-parasite pit connections between the red algal alloparasiteHarveyella mirabilis and its red algal hostOdonthalia floccosa

Harveyella mirabilis is a colourless red algal alloparasite which grows on and within its photosynthetic hostOdonthalia floccosa. Cells ofHarveyella establish secondary pit connections (PCs) with other parasite cells and with cells of the host. Small, uninucleate conjunctor cells are produced by parasite cells and remain connected to them by PCs. Conjunctor cells may fuse with either an adjacent host or parasite cell, with the parasite-conjunctor cell PC becoming either a host-parasite or parasite-parasite secondary PC. Occasionally the conjunctor cell does not fuse with an adjacent cell (either host or parasite) and degenerates. The secondary pit plug which forms between a parasite cell and its conjunctor cell always develops with two structurally distinct surfaces characteristic of a host-parasite pit plug. Only if the conjunctor cell fuses with another parasite cell will the structure of the pit plug be altered to that of a parasite-parasite pit plug. Fungal hyphae also invade the region of infection, andHarveyella cells respond by producing nonfunctional conjunctor cells that grow towards adjacent hyphae. Evidence suggests that secondary PCs may be induced to form mechanically, by the physical presence of another cell, rather than in direct response to a message received from an adjacent cell. The mechanism of secondary PC formation described here is similar to that reported for the closely related alloparasiteHolmsella and may be common to a number of red algal parasitic associations.

Carbon economy and nutrition of the alloparasitic red alga Harveyella mirabilis

Rhodomela confervoides (Huds.) Silva (Ceramiales: Rhodophyta) infected with the alloparasitic Harveyella mirabilis (Reinsch) Reinke (Cryptonemiales: Rhodophyta) was investigated with particular regard to rates of carbon fixation, patterns of soluble and insoluble assimilates, and transfer of reduced carbon from the photoautotrophic basiphyte to the fully heterotrophic epiphyte by means of 14C-labelling experiments. Gross carbon input by photosynthesis in Rh. confervoides accounted for about 53 μg Cd-1 when based on a biological unit (average individual of 200 mg fresh weight). Some 3% of the remaining net carbon gain (equivalent to about 0.7 μg Cd-1) was transferred from Rh. confervoides to its alloparasite, H. mirabilis (biological unit ≥0.5 mg fresh weight). Chromatographic examination showed that soluble 14C was translocated to and stored by H. mirabilis as mannosidoglycerate (=digeneaside) and probably a variety of amino acids. A certain proportion of soluble radiocarbon imported is converted by H. mirabilis to glycerolgalactoside (=floridoside). The bulk of imported 14C was recovered from the polymeric fraction, mainly from floridean starch.

On Choreocolax odonthaliae Levring (Cryptonemiales, Rhodophyceae)

Abstract The structure and development of the female reproductive system in Choreocolax odonthaliae show strong resemblance with Harveyella mirabilis. This has led to the merger of these two species of parasitic red algae and the reduction of C. odonthaliae to a synonym of H. mirabilis.

The biology of Harveyella mirabilis (Cryptonemiales, Rhodophyceae). III. Spore germination and subsequent development within the host Odonthalia floccosa (Ceramiales, Rhodophyceae)

A field and laboratory study of the parasitic red alga Harveyella mirabilis has revealed that spore germination and subsequent development of the parasite is dependent on the presence of a suitable host. Initial spore germination occurs in host wounds that are inflicted primarily by grazing isopods and amphipods. Rhizoidal cells intrusively grow into the walls between host cells and establish secondary pit connections with host cells. Subsequent development is characterized by rapid proliferation of the rhizoidal cells within the host, a rupturing of the host's outer wall region, and the final development of a colorless reproductive pustule. Several alternate substrata were used in a study of spore germination requirements, but only those that contained freeze-dried, powdered Odonthalia floccosa and O. washingtoniensis were successful in inducing the germination of Harveyella spores.

The biology of Harveyella mirabilis (Cryptonemiales, Rhodophyceae). IV. Life history and phenology

A 20-month field study of the reproductive biology of the parasitic red alga Harveyella mirabilis was undertaken to investigate the effects of environmental parameters on the reproductive periodicity of Harveyella in the intertidal habitat. In the northeast Pacific, tetraspores have been observed in the late winter - early spring; apparently they are produced in response to increased available sunlight and water temperature. Gametogenesis appears to be temperature sensitive; it occurs between a narrow temperature range (9–11 °C). Carpospores are produced in the late summer when both water temperature and day length reach a peak. The phenology of H. mirabilis in the North Atlantic differs from that which is observed in the North Pacific in the timing of gametogenesis and carposporogenesis. The significance of this is discussed in relation to the possible effects of differences in seawater temperature on gametogenesis.

The biology of Harveyella mirabilis (Cryptonemiales, Rhodophyceae). II. Carposporophyte development as related to the taxonomic affiliation of the parasitic red alga, Harveyella mirabilis

Abstract Carposporophyte development in the parasitic red alga Harveyella mirabilis is similar to that described in the red algal families Callymeniaceae (Cryptonemiales), Phyllophoraceae and Gigartinaceae (Gigartinales), but is unlike that of the Rhodomelaceae (Ceramiales) as previously reported. A large intercalary-borne supporting cell of the four-celled carpogonial branch acts as an auxiliary cell. The diploidized nucleus in the carpogonium is transferred to the juxtaposed auxiliary cell by means of a short connecting filament. A series of post-fertilization events gives rise to the gonimoblast, composed of horizontal and erect gonimoblast filaments with terminally-borne carpospores. Upon maturation the carpospores are released through ostioles in the female gametophyte. Whether Harveyella mirabilis should be systematically grouped with the Cryptonemiales or Gigartinales is discussed in regards to the positioning of the auxiliary cell.

The biology of Harveyella mirabilis (Cryptonemiales, Rhodophyceae). I. Cytological investigations of Harveyella mirabilis and its host, Odonthalia floccosa

The life history of Harveyella mirabilis, a presumed parasite on Odonthalia floccosa, has been investigated cytologically. These studies confirm that both species conform to a “Polysiphonia-type” life history. Chromosome counts made from reproductive and vegetative stages revealed a diploid number of 12 and a haploid number of 6. Diploid and haploid chromosome numbers of 10 and 5 respectively were found in Odonthalia floccosa. In contrast to mitosis in some higher plants and animals, a study of the mitotic time course in Harveyella mirabilis demonstrated a relatively long metaphase period, a fact which could be significant in considering the mechanics of cell division.

Harveyella mirabilis (Schmitz and Reinke)

Journal Article Harveyella mirabilis (Schmitz and Reinke): With Plates III and IV Get access HARRY H STURCH, PH.C, R.N. HARRY H STURCH, PH.C, R.N. Search for other works by this author on: Oxford Academic PubMed Google Scholar Annals of Botany, Volume os-13, Issue 1, March 1899, Pages 83–102, https://doi.org/10.1093/oxfordjournals.aob.a088728 Published: 01 March 1899