Report on molluscan species found in the offshore waters of Louisiana, including many extensions of known range and un-named species.
    This report deals with molluscs collected in waters of the Louisiana coast from 1970 to the present.  Early collecting resulted in only few species obtained principally by SCUBA diving on the offshore calcareous banks or "pinnacles" (García, 1974). However, beginning in 1993, the use of the "Pelican," a research vessel belonging to the Louisiana Universities Marine Consortium, produced many more species. (García 1999, 2000, 2001, 2002; García and Lee 2002, 2003). A large percentage of these taxa were not known to inhabit the northwestern Gulf of Mexico; of these, some had never been reported from anywhere in the Gulf; and still others, mainly micromollusks, seem to be undescribed species.

Bullina exquisita, Bursa ranelloides, Cymatium Rehderi

    Due to the effects of the Mississippi, Atchafalaya, and Calcasieu Rivers, the Louisiana coastal areas consist mainly of marshland and beaches composed of  mud or muddy sand. This type of rather uniform shoreline habitat is inimical to molluscan diversity. In contrast, offshore habitats are more diverse. Besides the prevalent muddy bottom, the many offshore oil-rig platforms act as artificial reefs, making it possible for epifaunal bivalves of the families Arcidae, Ostreidae, Chamidae and Spondylidae to prosper, and with them, the predators Stramonita haemastoma and Hexaplex fulvescens. Hydrocarbon vents on the continental slope off the Louisiana coast have also created an ecosystem with an interesting molluscan fauna (see Carney, 1994 and Warén and Bouchet, 1993). However, most diverse of the offshore habitats are the series of calcareous banks that arise abruptly from the deep, soft, muddy sediment to approximately 20 to 90 m from the surface and which are inhabited by a rich molluscan fauna. Parker et al. (1956) have recorded some 130 such banks off the Texas and Louisiana coasts. These banks, particularly those off Louisiana, are essentially calcareous islands in a sea of mud, and their molluscan species are quite different from the surrounding soft bottom.

    The mollusks in this list were collected from approximately 20 m to 680 m; from Latitude 27.48º N to 28.37º N, and from Longitude 88.59º W to 93.18º W. They were obtained by SCUBA diving, trawling, dredging, and with core grabs in mud, silty sand, calcareous rubble and hydrocarbon vents. The sediment obtained from such collecting methods was passed first through a 1/4' mesh and then through a 1/16" mesh to preserve the smaller species. Of the 459 species-level taxa listed, 146 are reported as new records for the northwestern Gulf of Mexico and comprise approximately 32% of the total. Each of these is marked with an asterisk (*). Many of the species have never been reported from the continental United States. As time permits, illustrations will be added to accompany the list; these species-level taxa will be conspicuously identified.

    We would like to thank the following persons for contributing to the accuracy of this list as well as for calling to our attention some overlooked references:  Mr. Roe Davenport (San Antonio, Texas), Colin Redfern (Boca Raton, Florida) and Marien Faber (Netherlands).

    You are welcome to download any of the images linked from these pages for private non-profit use. If they are to be republished, please request permission from Dr. Emilio F. Garcia. Also see www.jaxshells.org Terms Of Use.

Voucher specimens for all listed species are in the Thorpe, García and/or Lee collection

Molluscs found in the offshore waters of Louisiana, including many extensions of known ranges and un-named taxa

REFERENCES

Bright, T. J. and L.H. Pequegnat. 1974. Biota of the West Flower Garden Bank. Gulf Publishing Co, 435 pp.

Carney, R. S. 1994. Consideration of the oasis analogy for chemosynthetic communities at the Gulf of Mexico hydrocarbon vents. Geo-Marine Letters 14: 149-159.

García, E. F. 1974. A variation of Conus ranunculus Hwass. Of Sea and Shore. 5(3):121

_____. 1999. New molluscan records for the northwestern Gulf of Mexico. American Conchologist. 27(2):27.

_____. 2000. Surprising new molluscan records for Louisiana and the northwestern Gulf of Mexico.  American Conchologist. 28(3):5.

_____. 2002. More discoveries from a collecting expedition off the Louisiana coast. American Conchologist. 30(1):6.

_____. 2002. Unexpected molluscan finds from the hydrocarbon vents off the Louisiana coast. American Conchologist 30(4): 28.

García, E. F. and H. G. Lee. 2002. Report on molluscan species found in the offshore waters of  Louisiana, including many extensions of known range and un-named species. American Conchologist 30(4): 10-13.

_____. 2003. Report on molluscan species found in the offshore waters of  Louisiana, including many extensions of known range and un-named species. II. American Conchologist 31(1): 26-29.

Odé, H. 1975-1995. Monographs: Distribution and records of marine mollusks in the northwestern Gulf of Mexico. Texas Conchologist XI-XXXI.

Parker, R. H. and J. R. Curry. 1956. Fauna and bathymetry of banks on the continental shelf, northwestern Gulf of Mexico. Bull. Am. Assoc. Petrol. Geolg. 40(10):2428-2439.

Tunnell, J. W. Jr. 1970. A checklist of the mollusks of Seven and One-half Fathom Reef, northwestern Gulf of Mexico. Contributions in Martine Science 15:193-203.

Warén, A. and P. Bouchet. 1993. New records,species, genera, and a new family of gastropods from hydrothermal vents and hydrocarbon seeps. Zoologica Scripta. 22(1):1-90.

Back