Athanasios Athanasiadis

The genus Mesophyllum (Melobesioideae, Corallinales, Rhodophyta) on the northern Pacific coast of North America

Abstract We have re-examined the types and representative collections of taxa previously associated with or closely related to the genus Mesophyllum in the NE Pacific. The following five species are distributed between the Aleutian Islands and southern California (La Jolla): M. aleuticum Lebednik, sp. nov., M. vancouveriense (including Litholhamnion phymatodeum f. aquilonium), M. conchatum, M. lamellatum and M. crassiusculum (Foslie) Lebednik, comb. nov. (including Lithothamnion aculeiferum). All species exhibit a predominantly coaxial arching hypothallium, superimposing growth of new lamellae, a cuticle that covers the terminal meristem, raised conceptacles, and simple (unbranched) spermatangial structures. The five species differ in the following characters: (1) growth form (M. lamellatum and M. conchatum occur mainly epiphytically with the larger part of their thallus unattached, whereas the other species grow mainly attached, adhering strongly to the substrate); (2) perithallial stratification(not seen in M. lamellatum); (3) size of subepithallial meristematic cells (distinctly longer than cells below in M. conchatum, M. lamellatum and M. crassiusculum); (4) epithallial cell shape (roundish to squarish in M. lamellatum and M. conchatum, but generally flattened in the other three species); (5) perithallial protuberances (present in M. vancouveriense and M. crassiusculum); (6) degenerating conceptacles (in M. aleuticum, M. conchatum and M. lamellatum); (7) embedded conceptacles (in M. vancouveriense, M. crassiusculum and M. conchatum); and (8) the pore cell morphology of multiporate conceptacles. Tn addition, we have observed dumbbell-shaped carposporangial chambers displaying peripheral development of carposporangia in four of the species and lunate (in transverse section) spermatangial mother cells in M. vancouveriense, M. conchatum and M. lamellatum; we suggest that these distinctive morphologies may be new characters in the taxonomy of the genus. Each species is formally described and its features are illustrated, tabulated and discussed. A dichotomous key is given, and we emphasize the need for further examinations to establish the reproductive structures of gametangial plants of M. crassiusculum, and the distribution of this species and M. lamellatum.

Re-instatement of Leptophytum and its type Leptophytum laeve : taxonomy and biogeography of the genera Leptophytum and Phymatolithon (Corallinales, Rhodophyta)

In a recently published examination of the newly re-discovered holotype of Leptophytum (Lithophyllum) laeve, the characters of the holotype specimen were judged to be taxonomically inadequate. Consequently, an epitype was selected which was determined to belong to Phymatolithon lenormandii, rendering Leptophytum and its type L. laeve junior synonyms of Phymatolithon and P. lenormandii, respectively. We have re-studied the holotype specimen in Stockholm, and in this paper we demonstrate that it is consistent with the protologue and exhibits features that are fully consistent with the modern circumscription of Leptophytum laeve, based on population studies. Our results demonstrate that the holotype specimen is taxonomically adequate and that the selection of an epitype was not necessary. Accordingly, we propose the reinstatement of Leptophytum Adey 1966, based on its type L. laeve (Foslie) Adey (basionym: Lithophyllum lenormandii f. laeve Foslie 1891). The genera Leptophytum and Phymatolithon Foslie are sim...

The genus Leptophytum (Melobesioideae, Corallinales, Rhodophyta) on the Pacific coast of North America

A. Athanasiadis and W.H. Adey. 2006. The genus Leptophytum (Melobesioideae, Corallinales, Rhodophyta) on the Pacific coast of North America. Phycologia 45: 71–115. DOI: 10.2216/04-38.1 We provide a first account of the genus Leptophytum on the Pacific coast of North America, after re-examining the types and representative collections of species previously associated with Leptophytum, Mesophyllum and Lithothamnion of the Melobesioideae. Six species are recognized, distributed between Alaska (Port Clarence) and Baja California (Isla Magdalena), viz.: Leptophytum tenue (Kjellman) comb. nov. from Port Clarence and Orcas Island in Puget Sound (Washington State), L. adeyi from Tatoosh Island (Washington State), L. lamellicola sp. nov. from California (Monterey and San Mateo Counties) and southern Vancouver Island, L. julieae sp. nov. from SW and SE Vancouver Island and the Queen Charlotte Islands, L. foecundum var. sandrae var. nov. from southern Vancouver Island and Seattle (the typical variety foecundum being restricted to the Arctic and North Atlantic Oceans), and L. microsporum (Foslie) comb. nov. from southern California (Santa Catalina I.) to Baja California (Isla Magdalena). All species display the following characters, which unite them with North Atlantic congeners: noncoaxial (or predominantly noncoaxial) hypothallium, flattened epithallial cells, shedding conceptacles, and no perithallial protuberances. Sexual species (L. lamellicola and L. tenue in the North Pacific, and L. laeve and L. elatum in the North Atlantic) develop predominantly simple spermatangial mother cells with few branched ones occurring centrally or in other places on the chamber floor. Chambers of carposporangial conceptacles display a flattened floor with peripheral development of carposporangia. The NE Pacific species differ from each other in: (1) thallus adhesion (L. lamellicola and L. julieae grow partly unattached), (2) hypothallial growth (patches of coaxial cells occur regularly in L. lamellicola and less frequently in L. foecundum, L. tenue and L. microsporum), (3) perithallial stratification (present in L. lamellicola, L. julieae and L. foecundum), (4) size of subepithallial meristematic cells (distinctively elongateovate in L. julieae), (5) embedded multiporate conceptacles (present in L. lamellicola, L. julieae and L. microsporum), and (6) pore cell morphology of multiporate conceptacles. Each taxon is formally described, and its features are illustrated, tabulated and discussed. A dichotomous key to the six NE Pacific species is also provided together with an emended generic description that encompasses nine Northern and three Southern Hemisphere species.

(1577) Proposal to conserve the name Lithophyllum laeve Strömfelt against L. laeve Kützing (Corallinales, Rhodophyta) with a conserved type

Leptophytum Adey (in Hydrobiologia 28: 323. 1966) was originally established to accommodate two widely distributed North Atlantic-Arctic species; viz. its type Leptophytum laeve (Stromfelt) Adey and Leptophytum foecundum (Kjellman) Adey. Subsequent studies have added to the genus a total of 15 species from temperate regions in both the Southern and Northern Hemispheres (Adey in Kgl. Norske Vidensk. Selsk. Skr. 1: 1-46. 1970; Zaneveld & Sanford in Blumea 26: 205-231. 1980; Steneck & Paine in Phycologia 25: 221-240. 1986; Chamberlain in Br. Phycol J. 25: 179-199. 1990; Chamberlain & Keats in Phycologia 33: 111-133. 1994). Woelkerling (The Coralline Red Algae: 217. 1988) treated Leptophytum as being of uncertain status because the whereabouts of the type material of Leptophytum laeve (= Lithophyllum laeve Stromfelt) was unknown. Dilwel & Wegeberg (in Phycologia 35: 470-483. 1996) reported the discovery by W. J. Woelkerling of the holotype of Stromfelts Lithophyllum laeve in the Swedish Museum of Natural History in Stockholm (S), and after a study concluded that this element along with the original description of Str6mfelt (l.c.) were inadequate to define the identity of the species. Therefore, these authors selected an epitype from new material collected at the type locality Eyrarbakki (South Iceland). Unfortunately, the epitype selected and described by Diiwel & Wegeberg shows key characteristics of the lectotype of Phymatolithon lenormandii (Areschoug) Adey, rendering Leptophytum laeve and Leptophytum junior synonyms of Phymatolithon lenormandii and Phymatolithon Foslie, respectively. We have recently re-examined the holotype of Lithophyllum laeve Str6mfelt and shown that this element is in agreement with the protologue, matching not the selected epitype but all later descriptions of Leptophytum laeve as circumscribed in the literature of the 20th century (Adey & al. in Eur. J. Phycol. 36: 191-203. 2001) (see Table 1). A distinctive statement in the protologue, that the sporangia of Lithophyllum laeve Str6mfelt were twice as big as those of Phymatolithon lenormandii, is a characteristic definitively present in the holotype and clearly distinguishes these two species. Multiporate conceptacle roofs are also present in the holotype, and these numerically fall in the middle of the extensively described size and sporangial number (pore) range for Leptophytum laeve, at roughly twice the dimensions and pores of Phymatolithon lenormandii, and well beyond the maximum size range known for the latter species. Additionally, pore cells of multiporate conceptacles of the holotype are specialized and in agreement with those described for this species and not for Phymatolithon lenormandii (Adey & al. l.c.). The epitypification of Str6mfelts Lithophyllum laeve by Dtiwel & Wegeberg has resulted in this name being presently typified by two heterogeneous elements, i.e., the holotype and the epitype, each apparently belonging to a different species and genus. Only the holotype is in agreement with the protologue, and since only this element provides key characteristics that unequivocally refer to our understanding of Lithophyllum laeve Stromfelt, the selected epitype by Diiwel & Wegeberg is both unwarranted and in serious conflict with the protologue. Nevertheless, the epitype cannot just be rejected, as

On the occurrence of Mesophyllum expansum (Philippi) Cabioch et Mendoza (Melobesioideae, Corallinales, Rhodophyta) in the Mediterranean Sea, the Canary Isles and the Azores.

We reviewed literature records, examined herbarium specimens and studied new collections referred to as Mesophyllum lichenoides from the Mediterranean and the North Atlantic, and report for the first time the presence of Mesophyllum expansum in the Canaries and the Azores. Both gametophytes and tetrasporophytes of M. expansum occur in the Canaries, while we found only tetrasporophytes (and sterile thalli) of the species in all other regions. We further consider the presence of M. lichenoides further south than Atlantic France in need of confirmation. A comparative study between these two species points to the number of rosette cells as the most reliable and easily diagnosed character, M. expansum most often having 9–11 and M. lichenoides 6–8 cells.

Lithothamnion carpoklonion sp. nov. (Melobesioideae, Corallinales, Rhodophyta) from Puerto Rico, Caribbean Sea: an epiphytic encrusting coralline alga producing conceptacle protuberances

Abstract A new species of the globally reported genus Lithothamnion is described. Lithothamnion carpoklonion grows in shallow-sheltered waters off La Parguera, Puerto Rico (Caribbean Sea) attached to mangrove prop roots in association with other encrusting algae. The new species has requisite generic characters in addition to developing dorsal protuberances formed by superimposition of uniporate (carpogonial) or multiporate conceptacles. It is suggested that by this unique mode of conceptacle production, enhanced fertilization and spore dispersal are achieved simultaneously as vegetative (perithallial) growth is reduced.

A study of the original material of Lithothamnion engelhartii Foslie (Corallinales, Rhodophyta)

Abstract Eight collections of the type material of Lithothamnion engelhartii from Cape Jaffa and Kingston (South Australia) were re-examined and two disparate entities were shown to be included. Some specimens exhibit embedded conceptacles in the thallus where the perithallium dominates. The other specimens lack embedded conceptacles and the thallus is formed by unattached-superimposed lamellae where the hypothallium prevails. The lectotype selected here fits the second description and is in agreement with most other type specimens and recent material collected at Eyre Peninsula (South Australia). The lectotype specimen displays dorsiventral organization lacking perithallial protuberances. The hypothallium is polystromatic with coaxial to non-coaxial regions and forms a relatively thin ascending perithallium. Subepithallial cells are elongate and support single flattened epithallial cells. Multiporate conceptacles are bisporangial, develop in dense aggregations, and do not become embedded in the thallus (except via superimposition of new lamellae). Pore canals are conical to pyriform and develop differentiated cells lining the canals along the base. Syntype material exhibits simple spermatangia, and this character, together with the presence of elongate basal pore cells and the lack of a predominantly coaxial hypothallium, suggests an affiliation with the temperate species of Leptophytum from the NE Pacific.

Leptophytum flavescens comb. nov. (Corallinales, Rhodophyta), an Arctic endemic from the sublittoral of NW Spitsbergen, North Norway, and western Novaya Zemlya, with epitypification of L. laeve

ABSTRACT Type material of Lithothamnion flavescens Kjellman, originally described from Karlsøy (Troms) and Karmakul Bay (Novaya Zemlya), is re-examined and a lectotype is selected. Type specimens and other collections from NW Spitsbergen and North Norway possess distinctive characters of the genus Leptophytum, including the development of flattened epithallial cells, short subepithallial cells, and simple spermatangial structures. Leptophytum flavescens (Kjellman) comb. nov. resembles the generitype Leptophytum laeve, differing in having: (1) a thicker perithallium, to 900 µm (vs. 350 µm in L. laeve), that embeds older conceptacles, and (2) non-differentiated (in size or shape) pore cells of multiporate roofs. An epitype for L. laeve is also selected, which consolidates the status of this species and the genus, in agreement with the current literature and all publications prior to 1996.

Hydrolithon abyssophila sp. nov. (Hydrolithoideae, Corallinales), a bisporic coralline from the insular shelf edge of Puerto Rico and the Virgin Islands (US)

Abstract A new species of Hydrolithon is described from mesophotic habitats, between 30 and at least 76 m depth, off La Parguera, Puerto Rico, and St Thomas, Virgin Islands (Caribbean Sea). Its encrusting thallus covers corals and rocks. Hydrolithon abyssophila sp. nov. is distinctive in developing bisporangia that are about twice as large as its congeners and in lacking both perithallial protuberances and trichocytes in horizontal or vertical groups. It reproduces primarily by uninucleate bispores that presumably recycle the parental phase. Unfertilized carpogonia were observed in one collection suggesting the rare occurrence of gametophytic reproduction in the species.

Capensia fucorum (Esper) gen. et comb. nov. (Mesophyllaceae, Corallinales, Rhodophyta), a hemiparasite on Gelidium from South Africa

Abstract Capensia fucorum (=Mesophyllum capense) is described as the first hemiparasitic coralline genus and species infecting a non-coralline host (species of Gelidium). Amongst coralline algae, Capensia also exhibits a unique thallus organisation displaying sympodial branching at the margin and a monostromatic hypothallium with gradually ascending and descending filaments in the main thallus. Sympodial branching occurs from the ventral side of hypothallial cells and guarantees close adhesion to the host, while older hypothallial filaments are displaced dorsally to form the perithallium. Haustoria develop as terminal cells of descending filaments and penetrate the first and occasionally second cortical layer of the host. Capensia is monotypic with restricted distribution on Gelidium capense and Gelidium pteridifolium from South Africa. The generitype Capensia fucorum (= Millepora fucorum Esper) is originally described from the Cape of Good Hope. The new hemiparasitic genus, like its synonym, belongs to Mesophyllaceae and its closer relationship remains to be identified, starting the search in members of this family co-occurring with Capensia in South Africa.