Page 4 - Basso_et_al_2011_Phycologia_L_crispatum

Basso et al.: Lithothamnion crispatum Hauck 147
dorsiventrally organised (Fig. 1); haustoria are unknown.
In the lectotype, a crustose portion of the thallus is 200–
500 mm thick, with a hypothallium (ventral region) 50–
100 mm thick, composed of plumose filaments running
more or less parallel to the thallus surface (Figs 2, 3). The
mean size of hypothallial cells is 19 mm in length and
10 mm in diameter. The ventral filaments curve toward the
thallus surface to form a zoned perithallium (peripheral
region). Perithallial cells measure 4.5–23.5 mm in length
and 7–18 mm in diameter (Fig. 4). Epithallial cells occur
singly: they are flattened and flared (Figs 5, 6) and
measure 3–5.5 mm in length and 7–14.5 mm in diameter.
Subepithallial initials longer or as long as their inward
derivatives (Fig. 6), Cells of adjacent hypothallial and
perithallial filaments connected by cell fusions (Figs 1–4).
Secondary pit connections and trichocytes have not been
observed. Data on measured characters in the lectotype
are summarized in Table 1.
Features evident in the lectotype are also present in the
various representative specimens examined. Plants are
nongeniculate, attached or unattached as rhodoliths,
forming more or less globose or irregularly shaped thalli
(Figs 7–9). Crustose portions of plants and lamellae are
monomerous, dorsiventrally organized and have similar
features and proportions (but greater ranges) of hypothal-
lial and perithallial filaments, subepithallial and epithallial
cells (Figs 10–12). Data on measured characters are
summarized in Table 1.
As in the lectotype (Cabioch & Mendoza 1998, fig. 28),
all the other Mediterranean and western Atlantic rhodoliths
(da No´ brega Farias 2009; da No´ brega Farias et al. 2010
and this study) possess cylindrical protuberances flaring
distally into curly margined, funnel-like or cup-shaped tips
(Figs 7–9, see also Hauck 1878, pl. 3, figs 1, 2; Bressan &
Babbini 2003, p. 164, figs A, C, E). In some Mediterranean
specimens, a zone of large perithallial cells occasionally
occurs at the surface (Fig. 10).
REPRODUCTIVE ANATOMY: In the lectotype one single
buried and empty tetra/bisporangial conceptacle was detect-
ed (Fig. 13). The conceptacle chamber is 306 mm in diameter
and 153 mm high. Tetraspores and bispores were not
observed. The conceptacle roof is slightly protruding above
the surrounding thallus surface, 20–50 mm thick, and
composed of four to six layers of cells (Figs 13, 14). A
section through the roof shows depressions on top of pore
canals and surrounding pore cells (Fig. 14). Filaments lining
the pore canals differ from other roof cell filaments in usually
consisting of only two to three cells: the uppermost is a
disintegrated cell, which overlies a wedge-shaped cell and one
or two lowermost squat to elongate cells (Figs 13, 14). An
immature tetra/bisporangial conceptacle in surface view
shows depressions resulting from disintegration of the
uppermost cell of the filaments surrounding the pore canal
r
Fig. 4. Longitudinal section showing cell fusions (arrows) between cells of adjacent perithallial filaments. LM photograph, EE3 slide
10. Scale bar 5 25 mm.
Fig. 5. Surface view of epithallial cells showing median lamella (arrow). SEM photograph, stub 8506b1C. Scale bar 5 20 mm.
Fig. 6. From bottom to top: upper perithallial cells, subepithallial initials (i) and flared epithallial cells (e). Note fusions (arrow) between
cells of adjacent perithallium filaments. LM photograph, EA2 slide 4. Scale bar 5 25 mm.
(Fig. 15). Each pore is bordered by six to seven rosette cells
(Figs 15, 16).
The features of the multiporate conceptacle chamber in
the lectotype are evident in the various representative
specimens examined, showing some additional details and
the complete range of biometric variability of the species
(Figs 17–26). In the Mediterranean material, the size of
multiporate conceptacle chambers spans 270–720 mm in
diameter and 100–315 mm in height. Remains of sterile
filaments in mature conceptacles (Figs 19, 20), presumed to
be originally interspersed among tetra/bisporangia, persist
after tetra/bispores have been shed. Conceptacle roofs are
slightly protruding above or flush with surrounding thallus
surface. Variably raised rims are present or absent (Figs 17,
21; Basso 1995, pl. 5, fig. 5 as L. philippii; Bressan &
Babbini 2003: 164, fig. D). Roofs of mature tetra/
bisporangial conceptacles in surface view are pitted with
depressions (Figs 17, 18, 21), resulting from the disintegra-
tion of the uppermost rosette cells surrounding the pore
canal. Each pore canal is bordered by five to seven rosette
cells in surface view (Figs 17, 21, 22). Depressions over pore
canals locally reduce the roof thickness (Figs 23, 24).
Filaments lining the pore canals of mature conceptacles
usually two to three cells long. As described for the
lectotype, they are composed of an uppermost disintegrated
cell (Figs 23–26), a wedge-shaped cell and one or two squat
to elongate cells (Fig. 26).
The lectotype specimen lacked gametangial material.
Gametangial plants from representative material are,
however, dioecious. Spermatangial (male) conceptacles are
uniporate with mature conceptacle roofs slightly raised
above the surrounding thallus surface (Figs 27, 28). Male
conceptacles chambers measure 297–450 mm in diameter
and 135–198 mm in height, with a pore canal up to 207 mm
long and 60 mm in diameter. Spermatangial systems are
borne on the floor, walls and roof of the mature male
conceptacle chamber. Those across the chamber floor are
dendroid (branched) while those on the walls and roof are
simple (unbranched) (Figs 28, 29).
Presumed female/carposporangial conceptacles are unipo-
rate with mature chambers measuring 477–675 mm in diameter
and 243–297 mm in height and pore canals up to 216 mm in
length and 54 mm in diameter (Fig. 30). Although empty, they
are considered as carposporangial since their diameter is much
larger than that described for the female conceptacle of L.
superpositum (Keats et al. 2000; Harvey et al. 2003).
DISCUSSION
Tetrasporangial conceptacle roof pitted with depressions,
originating from degeneration of uppermost cells in
filaments bordering the pore canals, is a unique diagnostic
feature which distinguishes L. crispatum Hauck from other