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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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