Abundance of the Boring Polychaetes of Eunicidae (Annelida) in Great Nicobar Islands

Bioerosion is a major destructive force by mechanisms of grazing and boring organisms harmful on coral reef. The name of crypto fauna is associated with colonies of dead coral due to their role as bioeroding that alter the physical structure of reefs. Analysis of the cryptic polychaetes, totally 874 individuals were collected belonging to eight families among these families Eunicidae (14 species) is the best represented families, varied from 6 to 14 species in all the stations, where as the least number of species and numbers were collected in Johinder nagar (16.66 %) and maximum abundant in Bcori (52.56 %). The mean density of all the three stations varied from 8.785 ± 9.175 (Bcori), 5.142 ± 5.545 (Breakwater) and 2.785 ± 4.370 Johinder nagar. During this survey most abundant species Lydice collaris (30.34 %) followed by Eunice afra punctata (16.66%), L.ninetta (10.68%) and E. antennata (10.25 %) in all the three stations. They accounted for up to 50 % of the total number of individuals collected on dead corals and hard substrates. This study to evaluate the knowledge of the coral inhabiting polychaete distribution and to assist forthcoming researchers to know the particular groups taxonomy and towards better understanding utilization, in coral patches of the Nicobar areas.DOI: http://dx.doi.org/10.3126/on.v10i1.7754

Borers and encrusters as indicators of the presence of hermit crabs in Antarctic Eocene gastropods shells

The community of encrusting and boring organisms developed on shells of the gastropod Antarctodarwinella ellioti from the lower section of the La Meseta Formation (Eocene) exposed on Seymour (Marambio) Island, Antarctic Peninsula, allows inference that the shells were inhabited by hermit crabs. A Chi-square Independence Test revealed that the community - dominated by polychaetes and bryozoans - shows preference for the aperture interior area of the shell. A subsequent Cochran Q Test indicated that the differences in frequency of encrusting and boring organisms as counted on the different interior sectors of the aperture were statistically significant. Thus, polychaetes, boring bryozoans, and encrusting bryozoans, do not show the same frequency in each interior sector of the aperture; they are more frequent on the columella (P < 0.0001, P < 0.01 and P < 0.001 respectively). Encrusting bryozoans also appear to show a preference - albeit not as high as on the columella - for the outer lip. This community of boring and encrusting organisms and their distribution on the shell confirms that the shells were inhabited by hermit crabs. The community is similar to that described in Recent hermitted shells from mid-latitude temperate water environments, suggesting that such communities were already established in the Eocene.

The Incidence ofPolydora Ciliata and Cliona Celata Boring the Shell ofPatella Vulgata in Orkney

Poly dor a ciliata (Johnston) is a polychaete which lives in a U-shaped tube and is found in a wide variety of substrata, ranging from soft clays or muds to hard calcareous materials. Cliona celata Grant is a siliceous sponge which inhabits tunnels and galleries it has etched out in limestone, coral or molluscan shells. The effects of these two species of boring organisms on their hosts have been studied mainly for commercially important molluscs. Hannerz (1956) is the only record of P. ciliata infectingPatella vulgata L, and there is no previous record of anyCliona spp., infections.

Description and ecology of Recent endolithic biota from the Gulf Islands and banks in the Strait of Juan de Fuca, British Columbia

Eleven endolithic forms were distinguished from skeletal fragments collected near the Gulf Islands and from banks in the Strait of Juan de Fuca, British Columbia. The vast majority of studies dealing with endoliths are from tropical regions; however, the abundance of boring organisms described herein demonstrates their importance as sedimentological agents in mid-latitudes as well.Although some, if not most, of the borings occurred after the substrate organism was dead, the order of infestation was indeterminant. Fungal borings are densely distributed when in close proximity to algae. Although the nature of this biological association remains undefined, this relationship suggests that fungi prefer utilizing algae as an energy source. The observed decreased infestation of algal endoliths in shallow environs (less than 30 m) compared with that in deeper water might be attributed to less exposure in a high energy regime or to a freshness factor of the shells. Algal endoliths were observed in several shell substrates obtained from below the photic zone (defined as 45 m on the basis of the deepest occurrence of encrusting red algae). This distribution of endolithic microphytes indicates that any bathymetric zonation that may have been initially present was disturbed by the lateral transport of substrate particles. Furthermore, this suggests that algal borings should not be used independently of other environmental information to determine paleobathymetry.

Initial diversification of macroboring ichnofossils and exploitation of the macroboring niche in the lower Paleozoic

The traces of macroboring organisms are known throughout the Phanerozoic, with diversification and exploitation of the macroboring niche paralleling variations in the development of skeletal metazoa. The oldest macroboring biota is an abundant yet low diversity fauna in hardgrounds and reefs of Lower Cambrian age. Following the extinction of archaeocyathids at the end of the Lower Cambrian (and thus the demise of skeletal reefs until the Middle Ordovician), boring organisms appear to be restricted to submarine hardgrounds. With the development of skeletal reefs in the Middle Ordovician the macroboring fauna shows a rapid speciation and a dramatic increase in diversity. This same pattern occurs again in the Devonian. This record appears to represent refuge of the fauna in low stress, hardground environments when skeletal reefs were not present and radiation in the high stress environment of the reef when large skeletal metazoa were abundant and diverse.