Evidence for sublethal predation and regeneration among living and fossil ascophoran bryozoans

Virginia Museum of Natural History Special Publication 01/2008; 15:1-7.


Evidence for partial predation on ascophoran bryozoans was hitherto mainly found in borings of the frontal shield. However, during this and many other studies, borings are only observed rarely. Indeed, many predators (e.g. nudibranch gastropods) are known to gain access to the internal organs via the operculum while leaving no traces of frontal wall damage. This type of predation may, nevertheless, be evidenced by the presence of intramural buds underneath undamaged zooecia, indicated by the presence of one or more orificial rims within the primary one, and implies that the damage occurred during lifetime of the colony. This skeletal signature was observed to occur in Late Cretaceous Acanthostega, as well as in Miocene to Recent Lepraliomorpha, and in Recent Hippothoomorpha. Its infrequent presence may suggest that ascophorans are not important target species for many predators, that not all taxa are able to secrete intramural buds, and/or that only certain types of feeding mechanisms trigger this type of regeneration. Information on feeding habits of modern predators on ascophorans, and reactions of different ascophoran taxa to various types of predation, are needed to verify exactly when and why intramural buds are formed in preyed zooecia.

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    • "The idea of somewhat perennial colonies is supported by the common occurrence of regenerated zooids and nonfunctional zooids with orifices occluded by mineralised closures (Fig. 3e). These features may also reflect the presence and pressure of predators (Berning, 2008), as shown by numerous predation attempts that are visible in the lectotype by means of damaged orifices, and by the presence of a secondary or even tertiary orifice rim Fig. 6 -Cleidochasmidra portisi n. comb. from the Gulf of Noto (Catalogue number PMC R.I.H. B-25b). "
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