Agarophyton Gurgel, J.N.Norris et Fredericq, 2018

Gurgel, Carlos Frederico D., Norris, James N., Schmidt, William E., Le, Hau Nhu & Fredericq, Suzanne, 2018, Systematics of the Gracilariales (Rhodophyta) including new subfamilies, tribes, subgenera, and two new genera, Agarophyton gen. nov. and Crassa gen. nov., Phytotaxa 374 (1), pp. 1-23 : 8

Agarophyton Gurgel, J.N.Norris et Fredericq , gen. nov.

TYPE: Agarophyton chilensis (C.J.Bird, McLachlan et E.C.Oliveira) Gurgel, J.N.Norris et Fredericq , comb. nov.

BASIONYM: Gracilaria chilensis C.J.Bird, McLachlan et E.C.Oliveira 1986: 2929 , figs. 2–13).

HOLOTYPE: NRCC-9131(a), ♀, Bird et al. (1986, fig. 2).

TYPE LOCALITY: Penco, Bahía de Concepción, Provincia de Concepción, Región del Biobío, Chile.

HETEROTYPIC SYNONYM: Gracilaria sordida W. A. Nelson (1987: 90, figs. 6–9).

DIAGNOSIS: Algae with slender, cylindrical thalli; base crustose; main axis branching variable, subdichotomous to irregular, sometimes secund; secondary branches when present abundant, of variable lengths, also irregularly distributed along the main axes; cortical cells radially elongated, abrupt transition between cortex and medulla. Tetrasporangia cruciately divided. Spermatangial conceptacles of multiple kinds; forming shallow pits developed from cortical cells and flanked by elongated club-shaped cortical cells next to shallow, chilensis - type of conceptacles sensu Yamamoto (1984); to spermatangial resembling verrucosa -like conceptacles but without the cortical cell development as seen in Gracilaria subgen. Corallopsis keeping a clear separation between medullary cells and spermatangial-parent cells; to more morphologically complex cases of fused medullary conceptacles resembling the henriquesiana - type sensu Yamamoto (1984). Gonimoblast mass ampulliform or obpyriform, not completely filling the cystocarp cavity; inner gonimoblasts subglobose to oval, smaller outer gonimoblasts gradually giving rise to distinct radial chains of carposporangia at different stages of maturity, outer mature carposporangia obpyriform. Tubular nutritive cells either present or absent, when present tubular cells restricted to gonimoblast cells in vicinity of carpogonial fusion cells linking directly to inner pericarp cells or cortical cells. New tubular cells added at margin of gonimoblast mass as the cystocarp enlarges and carposporophyte develops a v-shaped concave base. New tubular cells particularly prominent along junction between carposporophyte base and pericarp. Multinucleate gametophytic cells enlarging, becoming deeply stained and interconnected by prominent pit connections in the vicinity of fused tubular cells. Pericarp cells contacted by gonimobast tubular cells not fusing with neighboring cells. Cells of sterile gonimoblasts large and pseudoparenchymatous.

EPITHET: The generic name, Agarophyton is formed from Malayan and Greek words. Agar- is derived from the Malay “agar-agar” (a gelatinous substance from seaweed; see: McHugh 2003) which we have joined with an “- o - “ to the Greek - phyton, thus the name means “agar-plant.” The type species, A. chilensis , and other species of this genus are currently the main sources of agar in the world ( Zemke-White & Ohno 1999).

REMARKS: In addition to the generitype, two other species are recognized to belong in Agarophyton . A fourth and still undescribed species in this genus has been recognized by Cohen et al. (2004) from specimens collected in New Zealand and southern Australia.

PERTINENT SPECIES IN AGAROPHYTON :