Gelidiopsis F.Schmitz, 1895

Holotype species: Gelidiopsis variabilis (Greville ex J.Agardh) F.Schmitz

Currently accepted name for the type species: Ceratodictyon variabile (J.Agardh) R.E.Norris

Original publication and holotype designation: Schmitz, F. (1895). Marine Florideen von Deutsch-Ostafrica. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 21: 137-177.

Description: Thallus arising from stoloniferous bases, forming mat-like growths composed of subcylindrical to compressed, subdichotomous to irregularly branched intertwining fronds, anastomosing occasionally. Construction multiaxial, cortex composed of a single layer of cuboidal or rectilinear cells subtended by progressively larger, increasingly elongate cells. Medulla composed of loosely aggregated elongated filaments in a weak gelatinous matrix. Reproductive structures on swollen terminal branches. Gametangial plants dioecious; spermatangia formed from spermatangial initials produced from cortical cells. Procarpic, carpogonial branches 3-celled, borne on a slightly enlarged supporting cell with a 2-celled auxiliary cell branch, initial division of the zygote oblique or nearly longitudinal, gonimoblast developing outwards from a fusion cell persisting in the mature cystocarp as a large columnar structure. Cystocarps in aggregates on branched fertile axes, ostiolate, never coronate, strongly protruding outwards, most cells forming carposporangia synchronously in a single gonimolobe, tela arachnoidea absent. Tetrasporangia in terminal nemathecia completely encircling the terete unbranched fertile axes. Initials formed terminally in a lateral position. Spores regularly or irregularly cruciately arranged.

Information kindly contributed by M.D. Guiry but may now be outdated.

Taxonomic status: This name is currently regarded as a synonym of Ceratodictyon.

Most recent taxonomic treatment adopted: Schneider, C.W. & Wynne, M.J. (2007). A synoptic review of the classification of red algal genera a half a century after Kylin's "Die Gattungen der Rhodophyceen". Botanica Marina 50: 197-249.

Comments: When Gelidiopsis was first described by Schmitz (1895), he recognized the relationship between it and Ceratodictyon and separated the two genera on the basis of the reticulate form of the thallus and its symbiotic association with a sponge. Gelidiopsis, largely because of a lack of frequent reproduction and a resemblance in outward form to Gelidium, was placed by several authors (Dawson 1953, Taylor 1960, Lawson and John 1982) in the Gelidiaceae. Norris (1987) after an examination of Gelidiopsis variabilis (Greville ex J.G. Agardh) Schmitz and G. intricatum (C. Agardh) Kützing, concluded that the genus was referable to the Gracilariaceae. However, recent molecular-systematics studies (Saunders et al., 1999) indicate that the genus should be placed in the Lomentariaceae. The inclusion of Gelidiopsis in Ceratodictyon, advocated by Norris (1987), was strongly opposed by Price and Kraft (1991) on the basis that the regularly anastomosing branches of C. spongiosum and its symbiotic association with a sponge were sufficient grounds for recognizing Ceratodictyon as a separate genus. Species of Gelidiopsis are known mainly from tropical and subtropical waters, G. variabilis (Greville ex J.G. Agardh) Schmitz and G. intricata (C. Agardh) Vickers are probably the most widely distributed species (see Norris 1987)