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 off 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 1999a, 1999b, 2000, 2001, 2002, 2005, 2006, 2007, 2008a, 2008b, 2008c, 2010, 2011a, 2011b, 2011c, 2012, 2013; 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.

Pteropurpura bequaerti Clench and Pérez Farfante, 1949    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, the 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 1745 m; from  Latitude 27º.35’N to 29º.20’N and from Longitude 88º.15’ W to 93º.18’ 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. Since 2007 the “Pelican” has been using the Benthic Skimmer (see García, 2007), a large dredge specially designed for the very soft silt that is found in the deep water benthos. This dredge has produced many species not collected by earlier designs.  Of the 646 species-level taxa  listed, 177 are reported herein as new records for the northwestern Gulf of Mexico and comprise approximately 27% of the total. Each of these is marked with an  asterisk (*). However, most of these new records have now appeared in Rosenberg et al. (2009). Many of the species have never been reported from the continental United States, and some have been recently described. For easier access, we have not attempted to rearrange the order of genera formerly assigned to “Turridae” . They remain alphabetized under that umbrella taxon. 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:  Roe Davenport  (San Antonio, Texas), Colin Redfern (Boca Raton, Florida), Phil Fallon (Farmingdale, New York, and Marien Faber (Netherlands). Material for this list is based in part upon work supported by the National Science Foundation under Grant No. 0315995, the “RAPID” grant, and the Gulf of Mexico Research Initiative, the latter supported by British Petroleum.

This list was last revised in November, 2013.

    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

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

_____. 1999b. Three new gastropod species from the New World. Apex 14(3-4):59-65 (Stated date: December 20, 1999)

_____. 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.

_____. 2005. Six new deep-water molluscan species (Gastropoda: Epitoniidae, Conoidea) from the Gulf of Mexico.   Novapex 6(4): 79-87.

 _____. 2006. Conus sauros, a new Conus species (Gastropoda: Conidae) from the Gulf of Mexico. Novapex 7(2-3): 71-76.

_____. 2007a. Results of deep-water dredging in the Gulf of Mexico using the “Benthic Skimmer,” and report on several geographic extensions, including two species not previously reported in the western Atlantic. The Festivus XXXIX(2): 13-18.

____. 2007b. A new species of Cosmioconcha (Gastropoda: Columbellidae) from the northern Gulf of Mexico. Novapex 8(2): 43-46.

 ____. 2008a. Eight new molluscan species (Gastropoda: Turridae) from the western Atlantic, with the description of two new genera. Novapex 9(1): 1-15.

_____. 2008b. Molluscan findings from a recent dredging expedition off the Louisiana coast. American Conchologist 36(4): 4-9.

_____. 2008c. Four new buccinid species (Gastropoda: Buccinidae) from the western Atlantic. Novapex 9(4):141- 148.

 ____. 2010. A geographic extension for two species of Favartia (Muricidae: Muricopsinae) from the western Atlantic. American Conchologist 38(3): 10-11.

 ____. 2011a. A new species of Mitra (Fusimitra) (Gastropoda: Mitridae) from the northwestern Gulf of Mexico. Novapex 12(3-4): 57-62.

 ____. 2011b.Two new species of Epitonium (Gastropoda: Epitoniidae) from the western Atlantic. Novapex 12(3-4): 99-107.

 ____. 2011c. On Vexillum (Pusia) articulatum (Reeve, 1845) and V. (P.) trophonium (Dall, 1889). American Conchologist 39(3) 10-11.

 ____. 2012. Noteworthy offshore mollusks from the north- central Gulf of Mexico, including geographical extensions and a generic reassignment. American Conchologist  40 (1):  34- 37.

_____. 2013. Report on a dredging expedition off the Louisiana coast including geographical extension and new record size. II. American Conchologist 41(1):4-8.

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.

Rosenberg, G., F. Moretzsohn and E. García. 2009. Gastropoda (Mollusca) of the Gulf of Mexico. In: Gulf of Mexico: Its Origins, Waters, and Biota.I,I. Biodiversity. D. L. Felder & D. K. Camp, eds, Texas A & M University Press, pp. 579-699.

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.

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