Phycodrys denticulatus (Tokida) J.M.Freese & C.E.Lane

Freese, Jillian M. & Lane, Christopher E., 2021, Reorganizing parasitic Delesseriaceae: taxonomic revision of Asterocolax, Phytotaxa 525 (2), pp. 124-136 : 130-132

Phycodrys denticulatus (Tokida) J.M.Freese & C.E.Lane comb. nov. ( Figs 5–7 )

DESCRIPTION: Thallus parasitic on Phycodrys fimbriata (Kuntze) Kylin. The parasitic thallus is yellow in color, 2 mm in diameter, with several cylindrical irregular branches, branches no longer than 3 mm, emerging from a small hemispherical cushion. The protologue description can be found in Tokida (1934).

BASIONYM: Polycoryne denticulata Tokida (1934) , Transactions of the Sapporo Natural History Society vol. 13, p. 199, Fig.1 .

HETEROTYPIC SYNONYM: Asterocolax denticulatus (Tokida) Feldmann & Feldmann

TYPE LOCALITY: Robben Island , Sakhalin, Russia (coll. Tokida, 1934)

SEQUENCED SPECIMEN: Collected in the Stefansson Sound Boulder Patch in July 2016 at 70˚19.25’ N , 147˚35.1’ W, Barrow , Alaska, USA, deposited NY03684214 , NY03384216 (coll. A. Muth , 2016, JF02 ) .

ETYMOLOGY: The specific epithet maintains the original nomenclature assigned to the description of the parasite by Tokida (1934).

REFERENCES: Tokida 1934; Feldmann & Feldmann 1951

DNA SEQUENCES: MH754750

REMARKS: Identification of the sequenced specimen as ‘ Asterocolax’ denticulatus was based on the morphological description of the parasite from Tokida (1934) and its occurrence on Phycodrys fimbriata .

Figures

FIGURE 1: Bayesian Inference tree for the ITS1, 5.8S, ITS2 DNA sequence alignment of Asterocolax, their hosts, and related species. Parasites are in bold with arrows pointing at their host. Phylogenetic tree includes proposed nomenclatural changes and previous Asterocolax species nomenclature. Values on the arrows represent sequence similarity (% pairwise identity) between host and parasite. The type species of Asterocolax described by Feldmann & Feldmann (1951) is indicated by ⊕. The values on nodes refer to Bayesian posterior probabilities (left) and bootstrap values (right). The lack of sequence divergence between of the Asterocolax gardneri sequences from California infecting Phycodrys isabellae (*) is not representative of the original figure (Goff et al. 1997, Fig. 1). The new species described in this study are indicated by § and ‡. Data generated in this study are denoted by underlined text.

FIGURES 5–7: Phycodrys denticulatus FIGURE 5: Mature parasitic pustule of Phycodrys denticulatus on its host Phycodrys fimbriata. Thallus is yellow in color with several round branches. Scale bar = 1 mm. FIGURE 6: 5 µm cross section of plastic embedded Phycodrys denticulatus stained in aniline blue. Tetraspores (*) occur along the branches of Phycodrys denticulatus and divide tetrahedrally or obliquely cruciate. Tetraspores average 40 x 60 µm. Scale bar = 100 µm. FIGURE 7: 5 µm cross section of Phycodrys denticulatus infecting Phycodrys fimbriata stained in aniline blue. Given the parasites immediate infection of host cells, it is near impossible to differentiate parasite cells from infected host cells. The medullary cells in the parasite thallus and the likely infected cells underlying the developing parasite thallus are conspicuously larger than uninfected host cells and filled with floridean starch granules. The cell walls of these extremely large medullary cells are also thicker than uninfected cells, a probable response to infection. Scale bar = 100 µm.

FIGURES 2–4: Polyneura latissimicola FIGURE 2: Mature parasitic pustule of Polyneura latissimicola on its host Polyneura latissima. Thallus is yellow in color with numerous conical branches. Scale bar = 1 mm. FIGURE 3: 5 µm cross section of plastic embedded Polyneura latissimicola carposporophyte, stained in aniline blue. Cystocarps occur at the basal ends of Polyneura latissimicola branches. Released carpospores are spherical to ovoid in shape and average 10 µm in diameter. Scale bar = 100 µm. FIGURE 4: 5 µm cross section through Polyneura latissimicola and its host, Polyneura latissima stained in aniline blue. It is difficult to determine the spread of the infection throughout the host and differentiate between parasite and host cells. Much of the parasite thallus is composed of large cells many of which contain numerous floridean starch granules. The cortical cells of the parasite thallus are notably smaller than other cells composing the parasite structure or uninfected host cells and lack many of the starch granules found in the medullary cells. Scale bar = 100 µm.