Bulla is a genus of medium to large hermaphrodite sea snails, shelled marine opisthobranch gastropod molluscs. These herbivorous snails are in the suborder Cephalaspidea, headshield slugs, and the order Opisthobranchia.
These snails are popularly known as "bubble snails", and their shells as "bubble shells", because the shell of some of the species is very inflated indeed, almost spherical in shape, and is also very thin and light.
According to some experts, Bulla is currently the only genus in the family Bullidae, which in turn is the only member of the superfamily Bulloidea.
All Bulla species have large, ovate external shells, which are large enough to accommodate the whole snail when retracted. All species have rather similarly shaped shells. The shells have a deep, narrow umbilicus at the apex. There is no operculum.
The smooth shell of Bulla is ovate and expanded, with a deep, sunken involute top. Since there is little difference between the shells and in the morphology of the radular teeth, there is some uncertainty about the exact taxonomy of the species in Bulla.
The gizzard of Bulla is rather different from that of other herbivorous groups. It has three large corneous crushing plates and ancillary corneous spines, instead of just grinding plates. The crawling snails show prominent, frilled or lobed parapodia.
Bulla species have a soft radula.
These snails are mostly nocturnal and can be found on shallow, sandy coasts grazing among sea grasses, feeding primarily on green algae. They bury themselves in mud when the tide is out.
In the coastal lagoons and bays of California, the colorful nudibranch Navanax inermis is a well-known predator of sea slugs, especially Bulla gouldiana, which it envelopes whole.
This family seems to have evolved separately in an early stage of the evolutionary history of the opisthobranchs. For a fuller treatment of the whole group see Cephalaspidea.
Bulla, Haminoea and Smaragdinella form the well-defined monophyletic group Bulloidea, according to the 1996 phylogenetic analysis of Paula M. Mikkelsen (Malacologia, 37(2): 375-442). But, according to Dr. Bill Rudman and others, differences in the alimentary canal and reproductive system, still put Haminoea and Smaragdinella into the separate superfamily Haminoeidea.
Historically, since the 18th century and even in the 20th century, the genus name Bulla has been used for a great number of bubble-shelled species that belonged to the order Cephalapsidea. From the mid-20th century, authors began to restrict species to the genus Bulla in its current meaning. But misidentifications were still numerous through high levels of intraspecific variability in the shell, radula and male genital system. The monograph by Malaquias & Reid (2008) has offered a systematic revision of this genus and has brought order in this genus
Bulla ampulla Linnaeus, 1758 Pacific bulla, ampulle bullaDistribution : on sandy sublittoral bottoms of warmer seas, tropical Indo-Pacific, Pakistan, Sri Lanka, PhilippinesLength : 60 mm (largest shell of the Cephalaspidea)Description : This is the common Bulla in tropical Indo-Pacific; globose, inflated, moderately solid body whorl. The white aperture is as long as the rest of the shell.The rounded outer lip is extended posteriorly beyond the apex. Columella in a reversed ‘S’-shape, smooth and thinly callous. Cream-colored with blotches of dark, purple-brown.Bulla arabica Malaquias & Reid, 2008Bulla bermudae Verrill and Bush, 1900Distribution : BermudasLength : 3 mmBulla clausa Dall, 1889 imperforate bubbleDistribution : FloridaLength : 12 mmBulla gouldiana Pilsbry, 1895 California bubble, Gould’s bubble, cloudy bubbleDistribution : Northwest America, California to EcuadorLength : 30–64 mmDescription: semi-transparent head, mantle and foot are yellowish-brown with mottled pale-bluish dots; reddish to brown involute (= sunken) apex; the aperture is wide anteriorly, narrow posteriorly; their egg mass is yellow to orange tangled string of jelly, containing oval capsules. Each one contains up to 25 eggs, which develop into veliger larvae.Bulla indolens Dall, 1927Distribution : GeorgiaLength : 7.5 mmDescription : found at depths up to 800 mBulla japonica T. Habe, 1976Distribution : JapanBulla krebsii Dall, 1889Distribution : GuadeloupeLength : 8 mmDescription : found at depths up to 1400 mBulla mabillei E. A. A. Locard, 1896 Mabille’s bubbleDistribution : Turkey, Canaries, Madeira, Cape Verde, West AfricaLength : 33–52 mmDescription : larger than the other European species; difficult to obtain; color : yellowish-brown with dark bluish dotsBulla morgana Dall, 1908Distribution : West AmericaBulla occidentalis A. Adams, 1850 (synonym of Bulla striata) common West Indian bubbleDistribution : Brazil, North Carolina to Florida, Bahamas, Caribbean.Length : 25 mmDescription : thin, rotund, oval shell with a smooth, glazed surface; pale color with brown spots; involute (= sunken) apex; large body whorl; long aperture, wide anteriorly; white columella.Bulla orientalis T. Habe, 1941Distribution : Indo PacificDescription : brown punctuate marks on the shellBulla peasiana Pilsbry, 1895Bulla punctulata A. Adams In Sowerby, 1850Distribution : Pacific, California, Mexico, PeruLength : 30 mmDescription : the shell looks like the one of Bulla ampula, but is smaller and more cylindrical. Its color is cream, with clouding of brown or gray in two to four spiral bands, generally spotted with squarish chocolate dots, bordered to the right by white spots.Bulla quoyii Gray in Dieffenbach, 1843 brown bubble shellDistribution : Southern Australia, northern New Zealand.Length : 44 mm-60 mmDescription :The calcified shell has a gray-brown color, with blotches of various shades of brown; the snail has a bright honey-golden color. The hind extremities of the headshield have evolved into tentacles, directing the water over Hancock’s organ. The egg-mass is a jelly-like sphere, with the eggs in a spiral string. After the breeding period, there occurs a mass mortality of the animals, just like the sea hares.Bulla solida Gmelin, 1791 solid bubbleDistribution : Mexico, Florida, Texas, Cuba, Colombia.Length : 30–52 mmDescription : found at depths up to 25 mBulla striata Bruguière, 1792 common Atlantic bubble, striate bubbleDistribution : Mediterranean, Morocco, Canaries, Azores, Atlantic Ocean, FloridaLength : 12–30 mmDescription : The shell is thin, delicate and rather narrow. The body whorl is oval and convex. The smooth elongated aperture narrows posteriorly, but is wide anteriorly. The columellar callus is rather small; The thin outer lip is incurved and extends a little beyond the apex; The color is brown-gray, with darker, smudged dots and dashes, spread unevenly over the surface. The surface is smooth, with some spiral grooves at the posterior end and at the apical umbilicus. There is no operculum. The foot is well developed. There are no parapodia (fleshy winglike outgrowths). The broadened head has no tentacles. The gills and the osphradium are inside the mantle cavity. The radula has three laterals on each side of the central tooth.Bulla vernicosa Gould, 1859 (most probably a color variant of Bulla ampulla)Distribution : Indo Pacific, Thailand, Indonesia, Philippines, Taiwan, TongaLength : 27–50 mmDescription : white-colored shell with lightbrown spotsIn addition to the above, there are a substantial number of names in Bulla that apply to the species Akera bullata, including Bulla akera (Gmelin, J.F., 1791), Bulla norwegica (Bruguière, J.G., 1789), Bulla canaliculata (Olivi, 1792), Bulla resiliens (Donovan, E., 1801), Bulla fragilis (Lamarck, J.B.P.A. de, 1822), Bulla hanleyi (Adams A. in Sowerby G.B. II, 1850/1855), Bulla elastica (Sandri & Danilo, 1856), Bulla farrani (Norman, 1890), Bulla globosa (Cantraine, F.J., 1840)
