Compsothamnionella huismanii sp. nov. (Ceramiales, Rhodophyta) from Southern Australia

A new species of Ceramiaceae, Compsothamnionella huismanii sp. nov. is described from southern Australia. It differs from the two other known species of Compsothamnionella (both from Japan) by its much larger cell and overall frond size. Complete post-fertilization details and male structures are described for the first time in the genus. The auxiliary cell is produced from one of the two pericentral cells on the fertile central cell of the female axis. The fertile central cell is the third to fifth cell below the apical cell. Up to five gonimolobe initials are produced from the auxiliary cell, each dividing to produce successively maturing gonimolobes composed of carposporangia of equal size. The apical cell of the fertile, axis, the sterile pericentral cell, and the lateral cell on the hypogenous cell divide to produce involucral branchlets which curve over the developing gonimoblast. The genus Compsothamnionella Itono appears to be closely related to Compsothamnion Naegeli and Antarcticothamnion Moe et Silva. These three genera should be grouped together in the Compsothamnieae, whereas Pleonosporium, Mesothamnion and Spongodonium, which were included in Compsothamnieae by Kylin (1956), should probably be placed in the tribe Spongoclonieae. However further investigation on relationships of these and other genera are necessary before tribal features can be more surely defined. Norris (1985, p. 63) considered that differences in the The genus Compsothamnionella was first described by type of sporangial division were insufficient grounds Itono (1977) in his comprehensive account of Cerafor separating genera and on the basis of the similarmiaceaous algae from southern Japan. A new species ities in their procarp systems, he returned Compsoof this genus has now been recorded from southern thamnionella japonica (Itono) Itono to Pleonosporium Australia. and also transferred Compsothamnionella megashiCompsothamnionella Itono (1977, p. 42) was based on mensis Itono (1977, p. 44) to that genus. At the same Pleonosporium japonicum Itono (1971, p. 229, fig. time and for similar reasons he subsumed Mesotham8A—C), including Callithamnion pedicellatum Itono nion Boergesen (1916, p. 208) into Pleonosporium. (1971, p. 219, fig. 1A—C), which was the tetrasporPost-fertilization stages of Compsothamnionella japonangial phase of the same species. Itono noted that ica beyond the production of an auxiliary cell as well Pleonosporium japonicum differed from Pleonosporas spermatangial material were unknown to both ium borreri (Smith) Naegeli (the type species) by bearItono and Norris. On the basis of close similarity in ing tetrasporangia rather than polysporangia, and other features it is highly probable that these strucfrom Compsothamnion by developing two rather than tures will prove to be the same in C. japonica, the three percentral cells on the central fertile cell of the type species of Compsothamnionella, as those we now female axis. Compsothamnion also produces two auxdescribe for C. huismanii sp. nov. If this is so, the iliary cells (Westbrook 1930, pi. 593, fig. 7) per prodistinctiveness of the genus from Pleonosporium and carp, whereas in Compsothamnionella there is only Mesothamnion cannot be ignored, one. Botanica Marina / Vol. 33 / 1990 / Fase, l Copyright © 1990 Walter de Gruyter · Berlin · New York 10 Gordon-Mills and Wollaston: Compsothamnionella huismanii from southern Australia The state of flux of tribal groupings of genera in the Ceramiaceae is seen in the history of the Compsothamnieae. Schmitz (1889, p. 450) proposed the tribe Compsothamnieae for the genus Compsothamnion Naegeli, based on the apparent lack of whorl-branchlets and rhizoids, and the cystocarp lacking an involucre, and this was followed by Feldmann-Mazoyer (1940). Later Kylin (1956, p. 384) included Compsothamnion, Pleonosporiwn Naegeli, Dasythamnion J. Agardh, Mesothamnion Boergesen, Lophothamnion J. Agardh, Spongoclonium Sonder and Haloplegma Montagne in the Compsothamnieae on the basis of their subterminal procarps with terminal cystocarps and single alternating lateral branch on each axial cell. Hommersand (1963, p. 345) grouped the same seven genera in this tribe. From time to time other authors have placed various genera in Compsothamnieae [e.g. Mazoyerella Gordon-Mills and Womersley (1974), Tanakaella Itono (Moe and Silva 1979), and Compsothamnionella Itono (Itono 1971, p. 42)], each emphasizing different features which supposedly held the genera together. However these were usually vegetative features (e.g. lack of a prostrate system or division of the apical cell) and little attention was given to the all-important development of female reproductive structures. The information and taxonomic groupings presented in this paper places emphasis on the latter, particularly in the type genus, and shows that a reassessment of the Compsothamnieae is essential. Cellulae apicales axium indeterminatorum 10—12 μm diam. , alternation oblique dividentest nunquam superataet cellulae axiales ad 500—600 \im diam.t 2—3 longlores quam latiores elongatans graduatim prope basem thallorum. Ramificatio axium lateralium altera distichaque, cellulae partibus medianis 30—60 μη diam.t 3—4 longiores quam latiores in regionibus superioribus thallorum. Rhizoidea corticalia 2—3 omnia latere inferiore cellula basali later alls exorientia, corticem spongiosamfacientia lateralibus externis. Diametro axium inferiorium 1 — 1.5 mm. Tetrasporangia tetrahaedralia, 40—45 μη diam. , terminalia in pedicellis brevis in partibus inferioribus ramulorum lateralium. Ramuli spermatangialis elongati, cylindricalis in partibus superioribus, ramosi basit 35—45 μηι diam. , longiores quam latiores 2—4 adaxiales incellulis inferioribus ramulorum. Systema procarpii non subterminalis, eel· lulis pericentralibus duabus cellula centrali; cellula supportanti cellula terminali et pericentrali sterili. Cellula auxiliaris usque ad quinque cellulas initiales gonimoloborum. Gonimolobi carposporangiis aequalibus 20 — 25 μm diam.t sequente maturscentes. Filamenta sterilia cellula apicali et cellula sterili pericentrali circum gonimoblastum juvenalem crescant. The new species is named after Dr John Huisman, who has contributed substantially to our understanding of the Ceramiaceae. Material and Methods All materials examined were either herbarium specimens or specimens in liquid preservative, deposited in ADU. Dried fragments were soaked off herbarium sheets with dilute detergent. Microscope slides were prepared after staining with 0.5 — 1 % aqueous aniline blue, acidification in l N HC1 and gradual infiltration with up to 50% Karo Syrup. Illustrations were made using a Leitz drawing arm and photographs were taken with Kodak 2415 panchromatic film using an ISSO filter.