Glossary

Descriptions below adapted from W. A. Nelson, J. Brodie & M. D. Guiry (1999). Terminology used to describe reproduction and life history stages in the genus Porphyra (Bangiales, Rhodophyta). Journal of Applied Phycology 11: 407-410.

“Asexual blade-phase spores: In areas of the blade where female gametes are produced, regular packets of spores are formed by a series of mitotic divisions, apparently developing without prior fertilization. Two types of asexual spores produced by the blade phase are known:
(1) Agamospores – formed by mitotic cleavage of blade cells, without fertilization; these germinate into conchocelis.
(2) Neutral spores – formed by mitotic cleavage of blade cells, without fertilization; these germinate into blades. Kornmann & Sahling (1991) used the absence of trichogynes to distinguish asexual spores produced by the blade-phase from zygotospores. As yet there has been insufficient work to assess whether this is a reliable character for differentiation of sexual and asexual blade regions, or of ploidy levels. It is known that the extent of trichogyne development varies greatly between species. Packets of asexual spores in Porphyra blades have been called aplanosporangia. This is a term applied to non-motile spores in the Chlorophyta, and Kornmann (1994) considered that, because all red algal spores are non-motile, the term aplanospore was not appropriate for the asexual spores in Porphyra. He instead proposed the use of agamospore and neutral spore to replace aplanospore.

Blade archeospore – formed by differentiation of a vegetative cell, which releases a single cell product that germinates into the blade/foliose phase. Previously referred to as monospores, this term is no longer considered to be appropriate and is reserved for use where single spores are produced by an unequal cell division (Magne, 1991).

Conchocelis archeospore – formed by differentiation of a vegetative cell, which releases a single cell product, which germinates into the conchocelis phase. These were previously referred to as monospores, a term that is now considered to be inappropriately applied to this spore type.

Conchocelis phase – the microscopic, sporophyte phase, which has been generally assumed to be diploid. The assumption that all conchocelis is diploid needs to be questioned, given that apogamy has been established in a number of life histories in culture where authors found no change in chromosome number in blade and conchocelis. Kornmann and Sahling (1991) refer to specific groups of species of Porphyra as being heteromorphic and monophasic and others as being heteromorphic and biphasic.

Conchospores/conchosporangia – differentiated filaments, which can be distinguished by color, shape, branching. Each sporangium releases a single product, which germinates to form the foliose/blade phase. Meiosis is documented to occur as the conchospore germinates.

Endospores/conchosporangia – arranged spores of indefinite number encased in a distinct envelope, fanned by mitotic divisions of a blade cell.

Female gametes – cells of the blade that differentiate to function as gametes prior to fertilization. In some species, trichogynes or prototrichogynes are produced from these cells. These are receptive extensions of the female cells onto which male gametes settle. Fertilization occurs when male gametes, after landing on the blade surface, produce a tube that penetrates the cell wall of the female gamete, enabling membrane fusion between the gametes.

Foliose blade phase – the macroscopic, gametophyte stage, which is normally either dioecious or hermaphroditic, although in some species both hermaphroditic and dioecious blades can be found. This stage is haploid.

Male gametes – products of mitosis, produced in regular packets through multiple divisions of blade cells after an initial production of a new cell wall layer. Male gametes can be distinguished from all other reproductive cells, because they are smaller and colorless, and released through cell wall breakdown. They are unable to live independently. The division formula (the arrangement of cells within the gamete packets, Hus, 1902) is a species-specific character. Male gametes in Porphyra have been referred to as antherozoids, B-spores and spermatia (most current treatments). The use of antherozoid inappropriately suggests motility and the use of spore implies the capacity to germinate and live independently. In Porphyra, multiple male gametes result from the divisions of an original single vegetative cell. This differs from the production of spermatia in Florideophycidae. Ultrastructurally, male gametes of Porphyra are similar to those produced by members of the latter subclass.

Neutral conchospores – formed on a differentiated filament, which differs from the surrounding vegetative conchocelis. Each sporangium produces a single product that germinates, sometimes in situ, to form further conchocelis.

Phyllospore – proposed term for spores produced by the blade phase where ploidy level and development are unknown. Use of specific terms for the spores from the blade phase requires knowledge of both ploidy level (zygoto- vs. agamospore) as well as the resultant development (agamospores vs. neutral spore). Information on cytological stage is still rarely available for most species, and frequently spore development has not been followed in culture. For these reasons, we recommend that the term phyllospore is used where ploidy and fertilization have not been confirmed and the fate of the spores upon release is unclear. This brings terminology in line with ‘conchospore’.

Protothalli – cellular masses, which do not exhibit developmental polarity and release protoplasts, which develop into foliar plants. These have been reported for at least four species of Porphyra although the fate of the protothalli has not been followed in all cases.

Zygotospores – mitotic divisions of the zygote result in regularly arranged, packets of diploid cells. The zygotospores are released through breakdown of the cell walls surrounding the packets and germinate into conchocelis.
The terms zygotosporangia and zygotospores were proposed by Guiry (1990) to replace carposporangia and carpospores in the Bangiales. After fertilization in Porphyra, the zygote divides directly to produce spores, whereas in the Florideophycidae the carpospores are produced by gonimoblast filaments, which may arise either directly or indirectly from the zygote.”