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%).
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