Blackwell Publishing AsiaMelbourne, AustraliaPREPhycological Research1322-08292006 Japanese Society of PhycologyDecember 20065514246Original Article Verosphacela silvae sp. nov.G. Alongi et al. Phycological Research 2007; 55: 42–46 Verosphacela silvae sp. nov. (Onslowiaceae, Phaeophyceae) from the Mediterranean Sea Giuseppina Alongi, Mario Cormaci and Giovanni Furnari* Department of Botany, University of Catania, via A. Longo 19, 95125 Catania, Italy SUMMARY We describe Verosphacela silvae sp. nov., from the Mediterranean Sea. It consists of horizontal filaments living on the lower face of the red alga Peyssonnelia rubra (Greville) J. Agardh, from which erect filaments up to 1.5 mm high rise and grow upright after passing through the thallus of the supporting species. There are both horizontal and erect filaments growing by apical cells. In the subapical cells, 1–2 longitudinal divisions occur (more frequently in the erect filaments) but no secondary transverse divisions occur. Erect filaments bear lateral propagules on a stalk of one to three (rarely more) cells. Propagules, with neither apical cells nor arms, consist of seven cells. Zoidangia are borne at the apex of erect laterals. The new species differs from V. ebrachia Henry mainly in habit, propagules and zoidangia. In addition, distinct from V. ebrachia, filaments of V. silvae never penetrate between the cuticle and the cell wall of the supporting alga. Moreover, propagules of V. silvae consist of seven cells, whereas those of V. ebrachia consist of 9–13 cells, and zoidangia are terminal on laterals in V. silvae, whereas in V. ebrachia they are sessile on both axes and laterals. Key words: Aeolian Islands, Mediterranean Sea, Onslowiaceae, Phaeophyceae, Verosphacela silvae. INTRODUCTION The monotypic genus with the species Verosphacela ebrachia (Onslowiaceae, Phaeophyceae) was described by Henry (1987) for a brown alga, collected at Vero Beach, Florida, USA, superficially endophytic in Spatoglossum schroederi (C. Agardh) Kützing. It showed ‘branched filaments growing by prominent apical cells, subapical cells becoming divided by one or two longitudinal divisions, and propagules without an apical cell or arms, usually germinating from a basal cell’. According to Henry (1987), the genus Verosphacela is related to the genus Onslowia Searles (Searles & Leister 1980), from which it differs mainly in its propagules, which lack an apical cell (whereas propagules of Onslowia have four meristematic apical cells). Searles placed Onslowia in the Sphacelariales because of the apical mode of growth, occasional longitudinal division of vegetative cells and the production of propagules, and in the Sphacelariaceae because of the occurrence of longitudinal vegetative cell divisions (Searles & Leister 1980). However, Henry (1987) placed both Onslowia and his new genus Verosphacela in the Choristocarpaceae (Sphacelariales) since they share with Choristocarpus a simple vegetative construction and propagules without the peculiar lenticular apical cell (always present in the development of propagules of Sphacelaria). Prud’homme van Reine (1982) opposed the inclusion of Choristocarpaceae within the Sphacelariales, but in 1993 (Prud’homme van Reine 1993) he placed the family in the ‘Sphacelariales (s.l)’, ‘because at the moment no other place in the classification system of brown algae can be suggested.’ De Reviers and Rousseau (1999) considered Choristocarpaceae incertae sedis. Finally, Draisma and Prud’homme van Reine (2001), on the basis of the molecular phylogenetic study by Draisma et al. (2001) in which it was demonstrated that Onslowia and Verosphacela are not monophyletic with the Choristocarpaceae, proposed placing these two genera in the new family Onslowiaceae. This new family differs from Choristocarpaceae in the occasional occurrence of longitudinal cell walls in the filaments (filaments strictly uniseriate in Choristocarpaceae) and in propagules lacking a large conspicuous apical cell (propagules with a large conspicuous apical cell in Choristocarpus). Moreover, Draisma and Prud’homme van Reine (2001) considered both Choristocarpaceae and Onslowiaceae incertae sedis ‘until additional DNA sequences resolve their currently obscure systematic position’. However, these families may both require accommodation in a separate order (Draisma 2002; Draisma et al. 2003). In the course of our floristic research on Mediterranean macroalgae, some specimens of a brown alga showing characteristics of the genus Verosphacela were *To whom correspondence should be addressed. Email: g.furnari@unict.it Communicating editor: K. Kogame. Received 2 March 2006; accepted 12 June 2006. doi: 10.1111/j.1440-1835.2006.00445.x Verosphacela silvae sp. nov. 43 14° 49’ E 14° 52’ E N 38° 35’ N M E D I T E R R A N E A Grotta Racina N S E A 38° 32’ N 0 Fig. 1. 2 km Map of Salina Island. Arrow indicates the type locality (Grotta Racina). collected at Salina Island (Aeolian Islands, Tyrrhenian Sea) (Fig. 1). A unique combination of characters indicates that this alga should be described as a new species: Verosphacela silvae sp. nov. MATERIALS AND METHODS Plants of Verosphacela were collected in June 2004 by SCUBA at 25 m depth at Grotta Racina (Salina Island, Aeolian Islands): 38°33′24.80′′N – 14°48′06.02′′E, on a thallus of Peyssonnelia rubra (Greville) J. Agardh. All observations were made on material preserved in 4% formaldehyde-seawater. Sections of the thallus of P. rubra were made by razor blade. Photographs were taken with a Nikon D1 digital camera and processed using Adobe Photoshop 6.0. RESULTS Verosphacela silvae Alongi, Cormaci et G. Furnari sp. nov. (Figs 2–13) Thalli filamentis prostratis laxe implexis, in sustinentis speciei thalli infera superficie insidentibus, ex quibus erecta filamenta ramosa usque ad 1.5 mm alta atque usque ad 25 µm lata oriuntur quae postquam sustinentis speciei thallum perforaverunt crescunt. Repentia erectaque filamenta, ex singula cellula apicali crescentia, cum subapicalium cellularum longitudinalibus divisionibus, frequentioribus in erectis filamentis, sed nullis secundariis transversalibus divisionibus. Filamenta erecta saepe veris phaeophyceanis pilis terminantia. Propagula ex septem cellulis constantia nec cellulis apicalibus nec brachiis instructa. Filamenta lateralia erecta zoidangia terminalia ferentia. Verosphacela silvae Alongi, Cormaci et G. Furnari sp. nov. (Figs 2–13) Thalli consisting of loosely matted horizontal filaments living on the lower face of a supporting algal species from which erect branched filaments up to 1.5 mm high and up to 25 µm in diameter arise and grow upright after passing through the thallus of the supporting species. Both horizontal and erect filaments, growing by apical cells, with 1–2 longitudinal divisions of subapical cells, more frequent in the erect ones, and no secondary transverse divisions. Erect filaments frequently terminating with true phaeophycean hairs. Propagules with seven cells ovoid to pyriform with neither apical cells nor arms. Zoidangia borne at the apex of erect laterals. Etymology: the specific name honours Dr P.C. Silva as a token of our esteem and friendship towards him. Holotype: CAT 2671 (the Herbarium of the Department of Botany, University of Catania, Italy), specimens with zoidangia and propagules, collected by M. Catra on 2 June 2004 on Peyssonnelia rubra. Type locality: Grotta Racina, Salina Island (Aeolian Islands), 25 m depth. Distribution: known only from the type locality. Vegetative organization Thalli of this species were found only on a thallus of Peyssonnelia rubra (Fig. 2) collected at Salina Island (Mediterranean Sea). They consist of a system of horizontal filaments (Figs 3–5) that are irregularly branched (Fig. 5), growing parallel to the lower face of P. rubra among its rhizoids. From this system erect filaments 44 G. Alongi et al. simple or irregularly ramified and frequently terminate with true phaeophycean hairs (Fig. 7). Both horizontal and erect filaments have apical cells which form subapical cells (primary segments) that do not form secondary transverse divisions but may divide once longitudinally (Fig. 6) and the resulting cells may each divide once or twice more. Such longitudinal divisions are frequent in erect filaments but are rare in the horizontal ones (Fig. 5). Erect filaments bear lateral propagules provided with a stalk of one to three (rarely more) cells (Fig. 7). The propagule initial undergoes two transverse divisions. The lowermost of the three resulting cells remains undivided; the central cell undergoes only one longitudinal division producing two cells while the uppermost cell undergoes two longitudinal divisions perpendicular to each other, producing four cells. Thus, the propagule eventually consists of seven cells and neither apical cells nor arms are differentiated. Some propagules germinate in situ, generally producing a filament before they are completely developed (Figs 8,9). Consequently, such propagules appear intercalary. Reproductive structures Both uni- and plurilocular zoidangia are subsphaerical, 40–60 µm in diameter and borne terminally on laterals (Figs 10,11). In plurilocular zoidangia (Fig. 11) locules are not easily detectable except for a faint peripherical reticulation so that they are hardly distinguishable from the unilocular ones. Faint scars of loculi in the internal wall are detectable in empty plurilocular zoidangia (Fig. 12). After the release of zoids, laterals can continue their growth by penetrating the empty zoidangium (Fig. 13). DISCUSSION Figs 2–4. Verosphacela silvae Holotype. 2. Habit on Peyssonnelia rubra. Arrows indicate erect filaments. 3. Radial section of P. rubra showing a horizontal filament (hf) of V. silvae from which erect filament arise (ef), after having traversed the thallus of P. rubra. 4. Horizontal (hf) and erect filaments (ef) of V. silvae detached from P. rubra, with an immature propagule (p). arise that pass through the thallus of P. rubra and emerge from its upper face (Fig. 3). Erect filaments are simple in the portion traversing the thallus of P. rubra, but ramify at the point from which they emerge (Figs 3,4). Erect filaments, up to 1.5 mm high, are The occurrence of branched filaments growing by prominent apical cells, subapical cells without transverse divisions but becoming divided by one or two longitudinal divisions, and propagules without an apical cell or arms show that our species undoubtedly belongs to the genus Verosphacela. V. silvae differs from V. ebrachia, the only other species of this genus, mainly in habit, propagules and zoidangia. V. silvae shows filaments growing parallel to the lower face of the supporting alga (Peyssonnelia rubra) among its rhizoids and never penetrating between the cuticle and the cell wall. Moreover, it shows a well developed system of erect filaments that emerge from the upper face of the supporting alga after having penetrated its thallus between cells. Even though the species was found only on P. rubra, it is reasonable to conjecture that it may occur on other algae. The unusual habit of V. silvae is similar to that of Polysiphonia perforans Cormaci, G. Verosphacela silvae sp. nov. 45 Figs 5,6. Verosphacela silvae Holotype. 5. Horizontal (hf) and erect filaments (ef) of V. silvae detached from P. rubra. 6. Apical region of an erect filament. Arrow indicates a segment with a longitudinal division. Furnari, Pizzuto and Serio (Cormaci et al. 1998). By contrast, V. ebrachia shows filaments spreading across lower portions of the host (Spatoglossum schroederi) growing between the cuticle and the cell wall and only occasionally penetrating between cells of the host. Propagules of V. silvae are provided with a stalk of one to three (rarely more) cells, whereas in V. ebrachia, they are borne on a one-celled stalk (and they were not observed in field material, but were obtained only in culture). Moreover, mature propagules of V. silvae consist of seven cells whereas those of V. ebrachia consist of 9–13 cells. This is the result of the different pattern of cell divisions of the propagules; in V. silvae the propagule initial undergoes only two transverse divisions, producing three cells, the lowermost of which remains undivided, the central undergoing only one longitudinal division and the uppermost two longitudinal divisions. Conversely, in V. ebrachia the propagule initial undergoes two or three transverse divisions producing three or four cells, respectively, the lowermost of which remains undivided, while each of the other two or three cells undergoes two longitudinal divisions, resulting in a propagule with nine or thirteen cells, respectively. Moreover, it should be noted that in situ germination observed in some propagules of V. silvae (see above) was not described in V. ebrachia. Zoidangia of V. silvae are similar in shape and size to those of V. ebrachia (subspherical, 40–60 µm in diameter in the former species, globose to obovate, 50– 70 µm in diameter in the latter), and in both species it is difficult to distinguish unilocular zoidangia from the plurilocular ones. However, in V. silvae both kinds of zoidangia are terminal on laterals whereas in V. ebrachia they are sessile on both axes and laterals. Moreover, it should be noted that in V. ebrachia propagules were obtained only in culture at 25 and 30°C under long-day (12 h or more) conditions (Henry 1987), whereas at the depth where V. silvae was collected (−25 m), the seawater temperature in June 2004 was 18°C (Decembrini F., pers. comm.). 46 G. Alongi et al. Figs 7–13. Verosphacela silvae Holotype. Details of erect filaments. 7. Mature propagules. Arrows indicate a phaeophycean hair. 8. Propagules germinated in situ (gp) and an empty plurilocular zoidangium. 9. Propagule germinated in situ (gp) and a unilocular zoidangium (uz). 10. Mature unilocular zoidangium. 11. Nearly mature plurilocular zoidangium (pz) and phaeophycean hairs. 12. Empty plurilocular zoidangium (pz). Arrows indicate faint scars of loculi in the internal wall of the zoidangium. Erect filaments continuing their growth through empty zoidangia. ACKNOWLEDGMENTS We thank Dr Franco Decembrini of the Consiglio Nazionale delle Ricerche (CNR), Istituto per l’Ambiente Marino Costiero (IAMC), Sezione di Messina (Italy) for information on seawater temperature. We are grateful to Dr Eric C. Henry for his suggestions. This work was supported by a Grant of the University of Catania, Italy (ex 60%). REFERENCES Cormaci, M., Furnari, G., Pizzuto, F. and Serio, D. 1998. Polysiphonia perforans sp. nova (Ceramiales, Rhodophyta) from the Mediterranean Sea. 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