NAME Palaeachlya perforans
AGE Early Paleozoic [Silurian?, Devonian?].   AGE span: 443.7...359.2 mya
K&J CLASSIFICATION (2000) Oomycetes, Saprolegniales.
FIGURE(S)
Image of
Pl.34fig.11.jpg
FIGURE REFERENCE Duncan PM. 1876. On some unicellular Algae parasitic within Silurian and Tertiary coals, with a notice of their presence in Calceola sandalina and other fossils; Quarterly Journal of Geological Society of London, v. 32, p. 205-211.
SPECIES, AUTHORITY P. perforans Duncan 1876, p. 209-210.
LOCATION Thin sections of the fossil coral Calceola.
ORIG DESCRIPTION* [here condensed and abbreviated] In the Calceola [coral] examined, [the previously discussed] tubes of all kinds were seen, and conidia of globular shape included in the larger ones. The largest tubes (fig. 12) are four or five times as broad as the medium-sized straight tubes (fig. 11); their exit in a loculus opening outwards at the surface can be seen. The loculus (figs. 12 & 13) sometimes contains a crowd of spores; and little wavy canals pass out from all sides. The contents of the tubes have undergone alteration in some, and a reddish tint has replaced the ordinary greenish-black color.

Evidently the parasite got into the old corals, as it does into those now living, from the outside, and by contact, growth, pressure, protoplasmic movement and the dissolving effect of the evolved gas, slowly and surely penetrated. The course, size, shape, and length of the tube being determined by the presence of the organic matter within the sclerenchyma and the arrangement of the coral-spicula, it is best to term the entophyte an alga, and classify it amongst the unicellular types in the neighbourhood of Achlya, calling it Palaeachlya perforans.

It is of course important to decide when the perforations were made. Were they forming contemporaneously with the growth of the coral and shell, or were they of subsequent date? In the first case the Silurian and Devonian age of the Achlyan becomes apparent; but if the second supposition be at all consistent with facts, the whole interest of the subject vanishes. The characteristic tubes of this alga have been found by me in species of Cyathophyllum from the Upper Silurian, and in a Foraminifer from the Lower Silurian of Canada. [For many more details, refer to original paper].
COMMENTS* A comparison of the parasitic excavation of recent corals with those of the secondary and Palaeozoic ages presents most remarkable resemblances. Tube may be compared with tube in all its parts; but fossilization has produced appearances in the spores and conidia which suggest distinction between the recent and the fossil kinds of algae. Nevertheless, the general character of the reproductive resting spores and the conidia arising from the vegetative part of the organism remain much the same. The large tubes in the Palaeozoic coral and Brachiopod, or whatever Calceola may be, would at first sight indicate a different species of parasite from those which formed the smaller penetrations; but both large and medium-sized tubes often exist in the same recent corallum, and these last now and then give off others so small and so finely linear that their diameter cannot be measured. While recognizing two or three forms of parasitic algae within these sclerenchymatous structures of recent and ancient date, it does not follow that they are to be made into different species. They may all be parts of the same mycelium-like growth of the parasite, and may depend upon the nature of the nidus in which growth has taken place. [For many more details, refer to original paper].
PUBLICATION REFERENCE Duncan PM. 1876. On some unicellular Algae parasitic within Silurian and Tertiary coals, with a notice of their presence in Calceola sandalina and other fossils; Quarterly Journal of Geological Society of London, v. 32, p. 205-211.
K&J REMARKS The description of this essentially modern-looking endozoic form, and the name Palaeachlya perforans Duncan gave to it, suggest its affinity to an extant genus Achlya, a saprolegniaceous fungus, although Duncan invariably refers to it as an alga or a form of Conferva [an old algal genus]. The coenocytic filaments, with long, cylindrical, terminal structures, generally resemble that of zoosporangia, containing spores (encysted zoospores) and probably emerging germ tubes (fig. 12) from the germinating spores, of modern water-molds. However, some algal thalli (Siphonales) also consist of coenocytic branched filaments similar to those found in Saprolegniales.

Duncan's discourse about the exact time of the infection by the fungus and the penetration of its hyphae into the fossil host [coral], whether simultaneously with the growth of the coral or, subsequently, even much later, especially in view of the fact that the fragments of mycelium and fruiting structures appear similar to living water-molds, casts some doubt about the stratigraphic age of the fungus. However, Duncan also indicated that the distinction between the recent and the fossil kinds of algae (Conferva) is visible due to the process of fossilization, except for the general character of the reproductive resting spores and the conidia arising from the vegetative part of the organism, which remain much the same. Kalgutkar and Jansonius (2000) consider the fungus a fossil of Early Paleozoic age within the sclerified tissues of an ancient coral.
TYPE no holotype designated [lectotype, fig. 13 selected by Kalgutkar and Jansonius (2000)].
ALL NAMES (Including synonyms) Palaeachlya perforans
SERIAL NUMBER 1175
PUBLIC COMMENTS
 *For source, see Publication Reference.