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Variations in Cystocarp Structure in Pterocladia (Gelidiales: Rhodophyta)

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Title:Variations in Cystocarp Structure in Pterocladia (Gelidiales: Rhodophyta)
Date Issued:Jan 1991
Publisher:University of Hawai'i Press
Citation:Santelices B. 1991. Variations in Cystocarp structure in Pterocladia (Gelidiales: Rhodophyta). Pac Sci 45(1): 1-11.
Abstract:Unilocular cystocarps distinguish Pterocladia from the morphologically
similar Gelidium, which exhibits bilocular cystocarps. Unequally developed
locules, regarded as exceptional, have been found in two species assigned
to Pterocladia. This study describes the patterns of morphological variation
found during cystocarpic development in Pterocladia musciformis Taylor and
in P. capillacea (Gmelin) Bornet & Thuret. About 70% of the cystocarps of
P. musciformis are Gelidium-type. The remaining exhibit unequally developed
locules with a longitudinal septum displaced off-center, sometimes producing
spores on only one side of the cystocarp and with one or a few ostioles only on
the most protruding face of the frond or blade. In a Brazilian population of
Pterocladia capillacea the internal cystocarpic structure changes with age. Young
cystocarps exhibit the typical structure of the genus. In more mature cystocarps
the septum is located close to the middle of the cystocarp, splitting the cavity,
which then appears as two unequallocules. A few ofthese larger cystocarps show
pericarps protruding equally on both surfaces of the frond and with ostioles on
each surface. It is concluded that the origin of the placenta seems to be the only
consistent reproductive difference that distinguishes Gelidium from Pterocladia.
It spite of the comparative scarcity of gametophytes, this distinction is the only
important one. Under this concept, the new combination Gelidium musciforme
is proposed. The pattern of cystocarpic development exhibited by Pterocladia
capillacea is clearly different from the one shown by P. lucida (R. Brown) J.
Agardh, the type species of the genus. However, additional studies of interspecific
and intraspecific variation in cystocarpic development in the genera
Pterocladia and Gelidium seem desirable before erecting a new genus.
Appears in Collections: Pacific Science Volume 45, Number 1, 1991

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