OCCASIONAL PAPERS OF THE FARLOW HERBARIUM OF CRYPTOGAMIC BOTANY HARVARD UNIVERSITY, CAMBRIDGE, MASSACHUSETTS No. 3 July 1972 Siphonoclathrus, a New Genus of Chlorophyta (Siphonales: Codiaceae) from Panama Sytv1a A. Earte and Joyce RepemMsky YouNG OCCASIONAL PAPERS OF THE FARLOW HERBARIUM OF CRYPTOGAMIC BOTANY No. 1. No. 2. No. 3. Sylvia A. Earle: Hummbrella, a New Red Alga of Uncertain Taxonomic Position from the Juan Fernandez Islands (June 1969). I. Mackenzie Lamb: Stereocaulon arenarium (Sav.) M. Lamb, a Hitherto Overlooked Boreal-Arctic Lichen (June 1972). Sylvia A. Earle and Joyce Redemsky Young: Siphonoclathrus, a New Genus of Chlorophyta (Siphonales: Codiaceae) from Panama (July 1972). SIPHONOCLATHRUS A NEW GENUS OF CHLOROPHYTA (SIPHONALES: CODIACEAE) FROM PANAMA SYLVIA A. EARLE FARLOW HERBARIUM, HARVARD UNIVERSITY CAMBRIDGE, MASSACHUSETTS JOYCE REDEMSKY YOUNG SMITHSONIAN TROPICAL RESEARCH INSTITUTE BALBOA, CANAL ZONE Summary A new genus and species of Chlorophyta (Siphonales: Codiaceae), Siphonocla- thrus stri, collected at Galeta Reef, Panama, 9°24’18”N latitude, 79°51’53”W longitude, is described and illustrated. Introduction A new genus and species of green algae, Division Chlorophyta, desig- nated here as Siphonoclathrus stri, was obtained by the authors while diving at Galeta Reef, Panama, 9°24’18’’N latitude, 79°51’53’’W longi- tude, on June 30 and July 1, 1971. During the following year, it was observed and collected repeatedly in all seasons. At first sight, the plant was recognized as new for the area, and subsequent investigation showed that it was an undescribed plant in the order Siphonales, closely related to the genera Udotea and Flabellaria, but distinctly different from any known genus. Ecology Plants were found growing on limestone and shells in 5 to 10 m depth at Galeta Reef near the Galeta field station of the Smithsonian Tropical Research Institute. The habit of the plant resembles that of Caulerpa verticillata, in that both form a delicate green mat on hard substrates, and the branching blades of both species create small, sometimes cir- cular, cuplike patterns. Caulerpa verticillata is darker green in life, how- ever, and often is taller, with many whorls of branches formed along a single stalk. In our collections, the two species occurred together, some- times intertwining on a single rock on protected and exposed areas of the reef, ys SIPHONOCLATHRUS Light intensity at the time of the original collection was low, the water turbid because of recent stormy weather. The visibility at the site may exceed 10 m, however, during extended periods of calm. The annual range of water temperature at the site is 26°C to 29.8°C, based on measurements taken from the surface to 11 m depth. The salinity ranges from 33.6 ppt to 38.8 ppt. Systematic Discussion Superficially, Siphonoclathrus appears to be related to Microdictyon (Siphonocladales), because both genera have small, green, translucent, monostromatic, net-like blades. Siphonoclathrus (Figs. 1-8) is clearly in the order Siphonales, however, as shown by the siphonous filaments with constrictions at the base of dichotomous branches (Figs. 7-8) characteristic of many members of the order, and by the possession of numerous small, discoid chromatophores, in contrast to the reticulate chromatophores characteristic of the Siphonoc’adales. The order Siphonales and its various subgroups are discussed by A. and E. S. Gepp (1911) and Egerod (1952). Siphonoclathrus appears to have characteristics consistent with the family Codiaceae Kiitzing orth. mut. Hauck. It resembles the genus Udotea Lamouroux 1812 in that plants consist of a stipe and frond or fronds, the frond flabelliform or infundibuliform, sometimes proliferous. Some, but not all species of Udotea have papillae on the blade filaments, as in Siphonoclathrus. Siphonoclathrus differs from Udotea in that it lacks calcification, and because of its unique monostromatic net-like blades. While calcification alone is perhaps not a valid generic feature in itself as shown by Egerod (1952), it is a valuable distinguishing trait that should be considered in combination with other characteristics. Siphonoclathrus is probably most closely related to the genus Flabel- laria Lamouroux 1913, in the subfamily Flabellarieae, described by Gepp and Gepp, 1911, with both genera characteristically consisting of uncalci- fied stipe and frond (or fronds), the frond flabelliform and thin, composed of filaments free or slightly held together by a few simple lateral branch- lets. Siphonoclathrus differs from Flabellaria in that fronds are net-like and commonly funnel-form (Fig. 5). Siphonoclathrus, gen. nov. Plants gregarious, erect, uncalcified, with thallus consisting of a rhizoidal base, a stipe of siphonous branching filaments, and flat or funnel-form monostromatic blade or blades borne terminally or laterally, composed of slightly adherent, dichotomously branching siphonous fila- SIPHONOCLATHRUS 3 ments; filaments with projections that touch and adhere to adjacent filaments, creating a mesh or net-like appearance. Constrictions and thickenings of the cell wall occur at the point of branching. Growth occurs at the blade margin, sometimes creating a conspicuous band or growth zone. Colonies of plants are apparently formed vegetatively through exten- sions of the rhizoidal base. Sexual reproduction unknown. Siphonoclathrus stri, sp. nov. Plants gregarious, erect, to 2 cm high, clear, pale green, attached with a rhizoidal base to limestone or shell; stipes usually branching, com- posed of adherent filaments (Fig. 6). Flat or funnel-form monostro- matic blades, to 5 mm wide, develop laterally or terminally on the stipe, sometimes growing together at a point of contact, and occasionally pro- liferating new blades from old. Blade filaments 2.5 to 3 » wide, with numerous lateral projections 2 to 3 » wide, 0.5 to 30 u long, that touch adjacent filaments, forming a mesh. Siphonoclathrus gen. nov. Plantae gregariae, erectae, haud calcareae, e basi radicanti surgentes, stipite filamentoso ramificantique et apice aut lateribus lamina (vel laminis pluribus) plana aut infundibuliformi, monostromatica praeditae, quae filamentis leviter cohaerentibus et dichotome ramosis composita est. Filamenta laminam reticulatam formantia, sese lateraliter ramulis brevissimis tangentia. Lamina in latere crescens, interdum zonam meri- stematicam sat conspicuam formans. Coloniae plantarum formantur, ut videtur, modo vegetativo extensione baseos rhizoidali. Reproductio sexualis ignota. Sipronoclathrus stri sp. nov. Plantae gregariae, erectae, ad 2 cm altae, pellucidae, pallide virides, basi rhizoidali saxo calcareo vel conchis affixae; stipites vulgo rami- ficantes, e filamentis cohaerentibus 2.5 » usque 3, latis contexti. Laminae monostromaticae planae aut infundibuliformae, ad 5 mm latae, lateraliter aut terminaliter e stipite oriuntur, interdum puncto commissurae con- ferruminatae et nonnunquam laminas secundarias e vetustioribus effer- entes, Filamenta laminae 2.5 » ad 3 » lata, ramulis brevissimis 2 » ad 3 » latis munita, qui filamenta adjacentia tangunt et ita reticulum interstitiis formant. Type collection: Plants collected by Sylvia A. Earle and Joyce Redemsky Young, June 30, 1971, on limestone in 8 m depth, Galeta Reef, Carib- bean Sea, Panama, collection number SE71101. 4 SIPHONOCLATHRUS Holotype: Deposited in the Farlow Herbarium of Cryptogamic Botany, Harvard University, Cambridge, Massachusetts. Syntypes: Deposited in the U. S. National Herbarium, Washington, D.C.; Algal Herbarium, University of California, Berkeley. The name, Siphonoclathrus, is derived from the Latin siphon, mean- ing a tube or siphon, to describe the basic structure of the plant, and the Latin clathrus, meaning a structure pierced with openings, as in a grating or trellis, referring to the net-like appearance of the blades. The specific epithet, stri, is an arbitrary assemblage of letters. Acknowledgements We are indebted to Dr. Ira Rubinoff and the Smithsonian Tropical Research Institute for use of laboratory facilities at Galeta, Panama; to Dr. Paul C. Silva and the University of California at Berkeley for use of essential library and herbarium reference materials; to the Farlow Herbarium, Harvard University, for publication funds, and to Dr. I. Mackenzie Lamb for reviewing the manuscript and preparing the Latin diagnoses. The Federal Water Quality Administration and the Inter- national Women’s Fishing Association provided research funds for Mrs. Young. References EGEROD, L. E. 1952. An analysis of the siphonous Chlorophyta, with special reference to the Siphonocladales, Siphonales, and Dasycladales of Hawaii. Univ. California Publ. Bot. 25 (5): 325-454. GEPP, A. and E. S. GEPP. 1911. Codiaceae of the Siboga expedition. Siboga-Expeditie Monogr. 62. Leiden. 150 pp. + 22pls. LAMOUROUX, J. V. 1812. Extrait d’un memoire sur la classification des polypiers coralligénes non enti¢rment pierreux. Nouv. Bull. Sci. Soc. Philom. Paris. 3: 181-188. . 1813. Essai sur les genres de la famille des thalassiophytes non articulées. Ann. du Mus. d’Hist. Nat. Paris. 20: 21-47, 115-139, 267- 293. 7 pls. FIG. 1. Photomicrograph of a small blade of Siphonoclathrus stri showing general form and net-like structure. FIG. 2. Photomicrograph of a small blade of Siphonoclathrus stri showing growth area along margin. FIG. 3. Photomicrograph of a small Siphonoclathrus stri plant from the original collection. FIG. 4. Photomicrograph of the holotype of Siphonoclathrus stri. FIG. 5. Camera lucida drawing showing habit of a single infundibuliform plant. FIG. 6. Camera lucida drawing of stipe filaments. FIG. 7. Camera lucida drawing of blade filaments of Siphonoclathrus stri showing branching habit. FIG. 8. Camera lucida drawing of blade filaments showing chromatophores and thickenings and constrictions at point of branching. ; = ere ET aa =e +e A Rtg, eae pane eye! ct ; * *3S PEE ery ean Pa en aire - cc any os “ee. i hae ae Ds gt OS ed Ong ae - nets Oh ener t ek Mead Roce cs sae ae rf ate> Jie