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Common Atlantic bubble, Bulla striata. Photo jaxshells.org.

Species Name: Bulla striata Bruguiere, 1792
Common Name: Common Atlantic Bubble
Striate Bubble
Synonymy: Bulla amygdala Dillwyn, 1817 - See below.
Bulla columnae Chiaje, 1823
Bulla modesto Risso, 1826
Bulla nebulosa Schroeter, 1804
Bulla omphalodes Chiaje, 1853
  1. TAXONOMY

    Kingdom Phylum/Division Class: Order: Family: Genus:
    Animalia Mollusca Gastropoda Cephalaspidea Bullidae Bulla

    Species Description

    The Atlantic bubble shell, Bulla striata, is a member of the Family Bullidae, the true bubble shells. The shell is thin and usually delicate, smooth, oval and inflated with an umbilicate (depressed) spire. The aperture is longer then the shell and is rounded at both ends, narrow posteriorly and wde anteriorly. The lip is thin and slightly constricted centrally. No operculum is present. The foot is well developed and the foot and mantle are slightly translucent. When the foot and mantle are extended, the animal completely envelops the shell, but it also can retract completely into it. There are no parapodia (fleshy winglike outgrowths). The head is broadened and lacks tentacles. The small eyes occur on the dorsal surface of the cephalic shield. (Abbot 1974, Abbot and Morris 1995, Baily-Matthews Shell Museum undated).

    Color is variable, pale reddish gray to brown-gray, mottled with darker smudged purplish brown dots. The aperature and the smooth, thin columellar callus is white (Abbot 1974, Abbot and Morris 1995, Oliver and Nicholls 2004).

    Tucker (1974) remarks that the type striata specimen comes form the Mediterranean, and that the Caribbean form is sometimes designated as the subspecies Bulla striata umbilicata. The author also notes that specimens identified as Bulla amygdale are probably a smooth form of B. striata.

    Bubble shells belong to the gastropod suborder Cephalaspidea, the headshield slugs, and to the order Opisthobranchia which also contains the sea hares, saccoglossans, nudibranchs, and others. The flattened cephalic shield possessed by members of the suborder is used for burrowing (Rupert and Fox 1988).

    Potentially Misidentified Species

    Bulla striata is relatively easily distinguished from co-occurring cephalaspideans by its size and shape. The solitary paper bubble, Haminoea solitaria, is smaller than B. striata (1.3 cm versus 2 cm) and has a spiral-grooved, fragile white shell. The channeled barrel bubble, Acteocina canaliculata, is very small (lass than 5 mm), and the shell is more strongly spired than that of B. striata (Rupert and Fox 1988).

  2. HABITAT AND DISTRIBUTION

    Regional Occurrence

    Bulla striata is widely distributed throughout the shallow tropics and subtropics on both sides of the Atlantic, including the Mediterranean, Morocco, Canaries, the Azores, and Florida.

    IRL Distribution

    Bulla striata occurs in soft sediment habitats throughout the IRL system (Mikkelsen et al. 1995, De Maintenon and Mikkelsen 2001, NBI undated).

  3. LIFE HISTORY AND POPULATION BIOLOGY

    Age, Size, Lifespan

    Rupert and Fox (1988) indicate that Bulla striata typically reach a shell length of around 2 cm.

    Reproduction

    Reproduction in Bulla striata involves copulation with internal fertilization between hermaphroditic individuals. Fertilized eggs are deposited as an external egg mass which individuals may attach to seagrass blades.

    The egg masses are long, irregularly coiled, gelatinous cylindrical cords. Egg capsules of specimens from the Western Mediterranean are ovoid and around 160 µm in length and each usually contains a single embryo. Uncleaved eggs average around 80 µm in diameter (Murillo and Templado 1998).

    Histological studies conducted by De Maintenon and Mikkelsen (2001) reveal that B. striata is a true simultaneous hermaphrodite, with male and female reproductive systems maturing at the same time. This is believed to be atypical for opisthobranchs, most of which are protandric (functionally male first) hermaphrodites (Gosliner 1994).

    Embryology

    Larval development is planktotrophic. Murillo and Templado (1998) report that veligers from the Western Mediterranean hatch 4-5 days after egg deposition. The authors reared planktonic larvae for up to 10 days but animals did not achieve metamorphosis. By day 10 the larval shell of the veligers attained a length of around 115 µm and the surface of the shell was smooth.

  4. PHYSICAL TOLERANCES

    Temperature

    Temperature tolerance experiments conducted by Murray and Wingard (2006) indicate Bulla striata is tolerant across a broad range of temperatures. Under both normal and hypersaline conditions, individuals survived and reproduced during extended (175-plus days) exposures to temperatures reaching 17.5 °C and 31 °C. Under hyposaline conditions, survival remained high but no reproduction occurred.

    Salinity

    Ross et al. (2000) calculated salinity tolerance indices for 32 mollusc species. The authors ranked Bulla striata as a "marine species", i.e., rather than as a "marine species with a tolerance for low salinity". Murray and Wingard (2006), however, demonstrated that B. striata was capable of surviving (although apparently not reproducing) during prolonged exposure to salinities as low as 16 ppt.

  5. COMMUNITY ECOLOGY

    Trophic Mode

    Although many bullid gastropods are herbivores, Bulla striata is reportedly a predatory species that feeds principally on molluscs (Baily-Matthews Shell Museum undated).

    Competitors

    No information is available.

    Predators

    Although bubble shells are vulnerable to certain predators, specific information regarding the predators of Bulla striata is lacking. The California predatory cepalaspid Navanax inermis is known to feed on Bulla gouldiana (Rudman 2003).

    Habitats

    Bulla striata is a burrowing species found in unconsolidated sand and mud substrata. They are common residents of estuarine flats and seagrass beds (De Maintenon and Mikkelsen 2001). As a whole, the members of order Cephalaspidea are species that are adapted for life on or in sandy bottoms. Cimino et al. (2004) suggest that the order retains the most ancestral characters found among the opisthobranchs.

  6. ADDITIONAL INFORMATION

    Special Status

    None.

    Economic/Ecological Importance

    The empty shells of dead B. striata are often an important resource for hermit crabs (Turra and Pereira Leite 2001).

  7. REFERENCES

    Abbot RT. 1974. American Seashells, The Marine Mollisca of the Atlantic and Pacific Coasts of North America. Second Edition. Van Nostrand Reinhold Company, New York. 663 p.

    Abbot RT and PA Morris. 1995. Shells of the Atlantic and Gulf Coasts and the West Indies. Peterson Field Guides. Houghton Mifflin Company, NY. 350 p.

    Baily-Matthews Shell Museum. Undated. Bulla striata species profile. Available online [http://www.shellmuseum.org/Sanibel/shells_bulla.html].

    Cimino G, Fontana A, Cutignano A, and M Gavagnin. 2004. Biosynthesis in opisthobranch molluscs: General outline in the light of recent use of stable isotopes. Phytochem Rev 3:285-307.

    Gosliner TM. 1994. Gastropoda: Opisthobranchia. Pp 253-255 in: Harrison FW and AJ Kohn (eds.). Microscopic Anatomy of Invertebrates, Volume 5. Mollusca I. Wiley-Liss, NY.

    de Maintenon M and PM Mikkelsen. 2001. Late reproductive system development in two cephalaspideans (Gastropoda, Opisthobranchia): Bulla striata Bruguiere, 1792, and Actocina atrata Mikkelsen and Mikkelsen, 1984. The Veliger 44:237-260.

    Mikkelsen PM, Mikkelsen PS, and DJ Karlen. 1995. Molluscan biodiversity in the Indian River Lagoon, Florida. Bulletin of Marine Science 57:94-127.

    Murillo, L and J Templado. 1998. Spawn and development of Bulla striata (Opisthobranchia, Cephalaspidea) from the western Mediterranean. Iberus 16:11-19.

    Murray JB and GL Wingard. 2006. Salinity and temperature tolerance experiments on selected Florida Bay mollusks. US Geological Survey Open File Report 2006-1026. Us Department of Interior/US Geological Survey. 59 p.

    NOAA National Benthic Inventory (NBI). Undated. Bulla striata collection information. Available online.

    Oliver APH and J Nicholls. 2004. Guide to Seashells of the World. Firefly Books, NY. 320 p.

    Rudman WB. 2004. Navanax inermis, Cooper 1863. Species profile from Sea Slug Forum. Australian Museum, Sydney. Available online. [http://www.seaslugforum.net/factsheet.cfm?base=navainer]

    Ross MS, Meeder JF, Sah JP, Ruiz PL and GJ Telesnicki. 2000. The Southeast Saline Everglades Revisited: 50 Years of Coastal Vegetation. Journal of Vegetation Science 11:101-112.

    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.

    Turra A and FP Pereira Leite. 2001. Shell utilization patterns of a tropical rocky intertidal hermit crab assemblage: I. The case of Grande Beach. Journal of Crustacean Biology 21: 393-406.

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

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