Pyropia plicata

The blades of Pyropia plicata are deeply folded and when fully extended are seen to have a circular to oval shape. The blades are very variable in size, generally in the range of 4–12 cm in diameter although reproductively mature thalli have been found to range from 1.5 cm through to 42 cm in diameter. The thalli are attached to rock substrata by a centrally located holdfast, made up of rhizoids extending from cells in the lower (central) area of the blade. The thalli are robust and very strongly attached to rock substrata in the upper intertidal zone of rocky open coasts (Figure 2). Thalli are primarily purple to grey in colour, but they become bleached particularly in summer and autumn and become khaki to yellow-green particularly on the upper edges. Thalli are monostromatic and monoecious. Sterile regions of the blades are ca. 50-55 µm thick and the margin of the blade has a ragged or irregular appearance bordered by several layers of small pale cells (Figure 3). Fertile regions of the blade develop around the margins with sterile cells intermixed with patches of spermatangia and presumed zygotosporangia (Figure 4). In the early stages of development spindle-shaped carpogonia form trichogynes on both sides of the blade, in marked contrast to the box-like shape of the neighbouring sterile cells (Figure 5). Blades increase in thickness to ca. 85–110 µm in zygotosporangial regions (Figure 6) and ca. 60–70 µm in mature spermatangial regions (Figure 7). The zygotosporangia when mature are deep red and the packets vary in size, becoming lozenge shaped at maturity with divisions up to a/8, b/8, c/8 (Figure 6). The spermatangial patches become golden as they develop and when mature are divided into packets ca. a/2, b/2, c/8 (Figure 7). Spermatia and zygotospores are usually released before reaching the maximum division formulae. Typically Pyropia plicata is found on the upper intertidal shores of open coasts on rocky substrata. It has not been found growing epiphytically and is uncommon in sheltered areas. The deep pleats and central attachment of Pyropia plicata enable the retention of moisture between the folds in the blade. This morphology would appear to be advantageous in the upper intertidal habitats where it is found, as this species can be out of water for periods of up to eight hours between tidal cycles. The outer part of a clump of Pyropia plicata may be dried with a cellophane-like appearance yet within the folds, parts of the blade remain wet. Pyropia plicata shows no particular seasonal trends in its distribution, with reproductively mature specimens collected throughout the year. Collections of this species have been made from the northern tip of the North Island, through to areas on the south western and south eastern South Island, as well as on the Chatham Islands. It has not been found on the Three Kings Islands, Stewart Island, or any of the New Zealand subantarctic islands. Distinctive features: Pyropia plicata can be distinguished from other New Zealand species of bladed Bangiales by a number of distinctive features. It is the only species of Pyropia present on mainland shores with a marked rosette-like growth form. Although the ribbon-like blades of Pyropia cinnamomea may become eroded with age, the basal position of the holdfast in this species differs from Pyropia plicata. In addition, these two species can be distinguished by colour, and also by the division formulae of zygotosporangia. On intertidal shores Pyropia plicata is characteristically found in the high intertidal but below the position occupied by Clymene coleana (W.A.Nelson) W.A.Nelson from which it can be easily distinguished. Clymene coleana has finely divided finger-like lobes rather than the continuous circular to oval deeply pleated blade of Pyropia plicata. Although both of these species have a predominantly grey colour in winter months, they bleach to different colours in bright light, with Clymene coleana becoming golden compared with the khaki colour of Pyropia plicata. In addition the zygotosporangia and spermatangia are arranged in separate areas of the blade in Clymene coleana rather than being intermixed in Clymene plicata.

New Zealand - North I., South I., Chatham Is.