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Species Name:    Melongena corona
Common Name:             Crown Conch

 

I.  TAXONOMY

Kingdom Phylum/Division: Class: Order: Family: Genus:
Animalia Mollusca Gastropoda Neogastropoda Melongenidae Melongena



Crown conch, Melongena corona. Photo courtesy Kathy Hill.

Species Name: 
Melongena corona Gmelin, 1791

Common Name(s):
Crown Conch

Synonymy:
Melongena pyruloides (DeKay 1843)
Melongena corona altispira (Pilsbry and Vanatta 1934) - putative subspecies (but see below) )
Melongena corona aspinosa (Dall 1890) - putative subspecies (but see below) )
Melongena corona bicolor (Say 1827) - putative subspecies (but see below) )
Melongena corona corona (Gmelin 1791) - putative subspecies (but see below) )
Melongena corona johnstonei (Clench and Turner 1956) - putative subspecies (but see below) )
Melongena corona sprucecreekensis (Tucker 1994) - putative subspecies (but see below)

Species Description:
The crown conch, Melongena corona, is a medium to large carnivorous gastropod with a low spire, large body whorl, and prominent vertical-curved white spines on the shoulder of each whorl that give the species its common name. It has a glossy shell that is brownish-grey to purple with white to yellow-white spiral bands. The columella is thick and white, and the operculum is robust and horny (Kaplan 1988, Rupert and Fox 1988).


Potentially Misidentified Species:
Highly variable coloration, size, and shell architecture, and the physical discontinuity of habitat in which ) Melongena is found have led to considerable taxonomic debate as to the designation of distinct species and subspecies. Historically, a number of putative Melongena species and M. corona subspecies have been collectively been referred to as the "corona complex." Recent DNA sequence analysis conducted by Hayes (2003), however, provided no support for historic taxonomic subdesignations and indicated that the corona complex consists of the single polymorphic species M. corona.


II.  HABITAT AND DISTRIBUTION 

Regional Occurrence:
Melongena corona is a tropical to subtropical species occurring on both coasts of the Florida peninsula, eastern Alabama, and throughout much of the West Indies south to South America. On the east coast, the northern distribution limit is currently reported as Matanzas Inlet south of St. Augustine (Hayes 2003).

IRL Distribution:
Melongena corona occur throughout the intertidal of the IRL system.


III. LIFE HISTORY AND POPULATION BIOLOGY

Age, Size, Lifespan:
Kaplan (1988) indicates that Melongena corona can attain lengths of greater than 200 mm, but most individuals are considerably smaller. The largest individuals, often exceeding 120 mm in length, are often found in association with oyster reefs while smaller animals dominate the intertidal flats (Boudreaux et al. 2006). Cannabalism has also been suggested as a strategy for achieving large size.

Abundance:
Melongena corona is typically among the dominant medium to large intertidal gastropods in the IRL and throughout Florida.

Reproduction:
Melongena corona is a direct-developing prosobranch gastropod in which the sexes are separate and females are on average slightly larger than males (Loftin 1987). The species, like all but the most ancestral gastropods, exhibits sexual reproduction via copulation and internal fertilization (Barnes 1987).

From late winter through summer, reproductive females embed from 15 to more than 500 eggs into protective egg capsules which they attach to a variety of low intertidal substrata in ribbon-like rows of between 6 and 20 capsules (Hathaway and Woodburn 1961). Suitable attachment substrates include rocks, shells of both dead and living organisms, mangrove roots, seagrass blades, wood, and a variety of artificial materials (Clench and Turner 1956, Loftin 1987, Hayes 2003).

Embryology:
The aplanic (no free-swimming stage) lecithotrophic larvae of Melongena corona are typical of direct developing prosobranchs.

Eggs hatch approximately 20-28 days after deposition. Some authors have reported observing crawl-away young incapable of swimming (Hathaway 1958, Gunter and Menzel 1958, Albertson 1980), while others report a brief swimming period in hatchlings (Loftin 1987, Hayes 2003). While egg capsule deposition occurs in the lower intertidal, newly emerged juvenile M. corona preferentially occupy the high intertidal (Woodbury 1986, Dinetz 1982), and Loftin (1987) speculated that the brief swimming stage allowed hatchlings to reach the upper intertidal by riding shoreward surface currents.

Loftin (1987) reports newly hatched animals measure less than 1 mm, but grow to more than 6 mm length within 2-3 months.


IV.  PHYSICAL TOLERANCES

Temperature:
Melongena corona is a cold-sensitive species. Loftin (1987) reports that populations may suffer high winter mortalities when low tides coincide with near-freezing temperatures. The northern distributional limit of the species in Florida is temperature-dependent, as demonstrated apparent slight range extension in milder years (Hayes 2003).

Salinity:
Hathaway and Woodburn (1961) report that Melongena corona at several sites on the Florida Gulf coast survive for extended periods at salinities as low as 8 ppt as well as those approaching oceanic conditions, and occupy habitats experiencing daily salinity changes of 12-24 ppt. The authors also noted that salinities in the range of 20-30 ppt are probably required for carrying out reproduction and other life activities (Hathaway and Woodburn 1961, Hayes 2003).

Early life history stages are less tolerant of salinity fluctuations and reportedly require a narrower range of 25-30 ppt. Hathaway and Woodburn (1961) reported developmental abnormalities in M. corona embryos at 21.5 ppt and increasing mortality rates at lower salinities.


V.  COMMUNITY ECOLOGY

Trophic Mode:
Melongena corona is an opportunistic predator/scavenger capable of feeding on a variety of live prey items as well as carrion and detrital material. Common dietary items include a number of bivalves such as Crassostrea virginica, Ensis minor, Tagelus divisus, as well as larger gastropods such as Busycon spp. (Gunter and Menzel 1957, Hathaway and Woodburn.1961). Crown conchs also readily consume any dead and dying organisms they may encounter (Gunter 1957, Hayes 2003). Dalby (1989) reported predation by crown conch on ascidians as well.

Hayes (2003) notes that newly hatched crown conchs are believed to bury themselves within the sediments of the upper intertidal and subsist for a time on detrital matter and small bivalves.

Although M. corona has been implicated in the decline of oyster abundance and production (e.g., in Tampa Bay), studies by Hathaway and Woodburn (1961) and others conclude that the gastropod is likely not capable of measurably impacting oysters through predation.

Competitors:
A wide diversity of carnivorous gastropods co-occur with Melongena corona and likely compete for dietary resources. Melongenid species like whelks (Busycon spp.) and tulips (Fasciolaria spp.), murex snails (Muricidae) and Florida horse conch (Pleuroploca gigantea) are among the potential competitors for prey.

Predators:
Melongena corona is susceptible to predation by large co-occurring carnivorous gastropods such as the Florida horse conch (Pleuroploca gigantea) and the lace murex (Chicoreus florifer). Hayes (2003) notes that such species typically occupy deeper subtidal habitats surrounding the intertidal areas inhabited by crown conchs potentially limiting their dispersal ability.

Habitats:
Adult Melongena corona are prominent members of the intertidal and shallow subtidal (to 2.5 m) epifaunal community in the IRL. They can be found in a variety of low-energy habitats, including seagrass meadows, salt marsh, mangrove marsh, oyster reefs, and tidal mud flats. They are excluded from high-energy shorelines (Loftin 1987, Kaplan 1988, Hayes 2003, Boudreaux et al. 2006). When this intertidal species becomes exposed at low tide, it typically buries itself part-way in the wet sand until the next high tide.

M. corona was considered by Tiffany (1974) to be an indicator of poor environmental water quality if it occurred in large numbers in the absence of other species.

Activity Time:
A field study by Hamilton (1996) suggests that the timing of foraging activity in Melongena corona is dictated more by the timing of tidal cycles than by day-night cycles. The observer noted active foraging by day and night and made the assumption that animals were equally active at both times. The author also noted that a majority of tagged study individuals were observed to orient generally in an offshore direction during outgoing tides, apparently to maximize foraging time and minimize exposure to the air.


VI. SPECIAL STATUS

Special Status:
None

Economic Importance:
Although Melongenid gastropods belonging to the genera Melongena, Busycon, and Hemifusus contain a number of species that are harvested for their meat elsewhere (Kaplowitz 2001), no commercial harvest of Melongena corona for this purpose in Florida exists.

M. corona has been eyed as a predatory species potentially impacting populations of economically important species such as eastern oysters (Crassostrea virginica) and hard clams (Mercenaria mercenaria) (Hathaway and Woodburn 1961, Estevez and Bruzek 1986).


VII.  REFERENCES

Albertson HD. 1980. Long term effects of high temperatures and low salinities on specimens of Melongena corona and Nassarius vibex. Unpublished Ph.D. Dissertation, University of Miami, Coral Gables FL. 222 p.

Barnes. 1987. Invertebrate Zoology. 5th edition. CBS College Publishing, NY. 893 p.

Boudreaux ML, Stiner JL, and LJ Walters. 2006. Biodiversity of sessile and motile macrofauna on intertidal oyster reefs in Mosquito Lagoon, Florida. Journal of Shellfish Research 25:1079-1090.

Clench WJ and RD Turner. 1956. The family Melongenidae in the western Atlantic. Pp. 161-188 in: Johnsonia: Monographs of the marine mollusks of the Western Atlantic, 3(35). Department of Mollusks, Museum of Comparative Zoology: Cambridge MA.

Dalby, JE, Jr. 1989. Predation of ascidians by Melongena corona (Neogastropoda: Melongenidae) in the northern Gulf of Mexico. Bullietin of Marine Science 45:708-712.

Dinetz BJ. 1982. Intraspecific size distribution of the crown conch, Melongena corona Gmelin: zonation on a low energy beach. Unpublished MS Thesis. University of Florida, Gainesville FL 73 p.

Estevez ED and DA Bruzek. 1986. Survey of mollusks in southern Sarasota Bay, Florida, emphasizing edible species. Mote Marine Laboratory Technical Report no 102. 97 p.

Gunter G. and RW Menzel 1957. The crown conch, Melongena corona, as a predator upon the Virginia oyster. Nautilus 70:84-87.

Hamilton PV. 1996. Tidal movement pattern of crown conchs, Melongena corona Gmelin. Journal of Molluscan Studies 62:129-133.

Hathaway RR. 1958. The crown conch Melongena corona Gmelin; its habits, sex ratios, and possible relations to the oyster. Proceedings of the National Shellfish Association 48:189-194.

Hathaway RR and KD Woodburn. 1961. Studies on the crown conch Melongena corona Gmelin. Bulletin of Marine Science 11:45-65.

Hayes KA. 2003. Phylogeography and evolution of the Florida crown conch (Melongena corona). Unpublished MS. thesis, University of South Florida. 201 p.

Kaplan EH. 1988. A Field Guide to Southeastern and Caribbean Seashores: Cape Hattaras to the Gulf Coast, Florida, and the Caribbean. Peterson Field Guide Series. Houghton Mifflin Company, NY. 425 p.

Kaplowitz MD. 2001. Uncovering Economic Benefits of Chivita (Melongena melongena Linnaeus,1758 and Melongena corona bispinosa Philippi, 1844). Journal of Shellfish Research 20:295-299.

Loftin JL. 1987. The distribution of Melongena corona (Gmelin 1791) egg capsules in North Florida. Unpublished M.Sc. Thesis, Florida State University, Tallahassee FL. 101 p.

Rupert EE and RS Fox. 1988. Seashore Animals of the Southeast. A Guide to Common Shallow-Water Invertebrates of the Southeastern Atlantic Coast. University of South Carolina Press. 429 p.

Tiffany WJ, III. 1974. Checklist of benthic invertebrate communities in Sarasota Bay with special reference to water quality indicator species. Contribution No. 2, Flower Gardens Oceans Research Center, Marine Biomedical Institute, Galveston, TX. 136 p.

Woodbury BD. 1986. The role of growth, predation, and habitat selection in the population distribution of the crown conch, Melongena corona, Gmelin. Journal of Experimental Marine Biology and Ecology 97:1-12.

Report by:  J. Masterson, Smithsonian Marine Station
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Page last updated: September 1, 2008