Ascobulla Japonica

Introduction

''Ascobulla'' is a genus of sea snails, a marine gastropod shelled- sacoglossan mollusk in the family Volvatellidae. A more common term for the organism is “bubble snails.” The description of “bubble-shells'' comes from the shape of the head-shield and large external shell.Mikkelsen, Paula M. "Cylindrobulla and Ascobulla in the western Atlantic (Gastropoda, Opisthobranchia, Sacoglossa): systematic review, description of a new species, and phylogenetic reanalysis." Zoologica Scripta 27.1 (1998): 49-71 There are three shelled-sacoglossans: ''Cylindrobulla'', ''Ascobulla'', and ''Volvatella''. These three oxynoacean are the most primitive living members of the gastropod order Sacoglossa . Much confusion has occurred in the exact classifications between these species, and living animals of ''Cylindrobulla'' and ''Ascobulla'' have often been considered to be essentially identical, but more recent research is geared towards distinguishing between the two. Several unambiguous features have been found to clearly distinguish the two: These are the cephalic shield with a shallow furrow found in ''Cylindrobulla'', the broad tooth shape of Cylindrobulla, the number of more than 50 teeth in ''Cylindrobulla'', and the equal length of the radula limbs in ''Cylindrobulla''.Laetz, Elise, et al. "The Cylindrobulla/Ascobulla complex—unraveling problems in identification and adding to Cylindrobulla diversity (Gastropoda, Heterobranchia, Sacoglossa) by describing a new species." Zootaxa 3893.3 (2014): 339-362. To date, the genus ''Ascobulla'' contains 5 species: A. californica, A. fischeri, A. fragilis, A. japonica, and A. ulla.

Distribution

''Ascobulla'' appears to show a global distribution in tropical and subtropical waters. Caribbean (Caribbean coasts of Mexico in mangrove habitats), Mediterranean.Gavagnin, M., Mollo, E., Montanaro, D. et al. Chemical Studies of Caribbean Sacoglossans: Dietary Relationships with Green Algae and Ecological Implications. J Chem Ecol 26, 1563–1578 (2000). https://doi-org.ezproxy.bu.edu/10.1023/A:1005526526884 One species within the ''Ascobulla'' genus that has received focus in research is Ascobulla fragilis. This snail inhabits the warmer areas of the Mediterranean Sea.Amancic, S. "Ascobulla fragilis (Jeffers, 1856.) u priobalju Istre." (2020). It is also found in the waters near the Cape of Good Hope in South Africa.

Physical description

''Ascobulla'' exhibits a cylindrical, often somewhat pear-shaped shell with a concave apex and the protoconch (the embryonic/larval shell) exposed at the center. The shell itself is fairly thin and lightly calcified. It exhibits a sutural slit and a sharp edged sutural keel.Jensen, Kather R. "Phylogenetic systematics and classification of the Sacoglossa (Mollusca, Gastropoda, Opisthobranchia)." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 351.1335 (1996): 91-122. ''Ascobulla'' has a cephalic shield, which is a hard external covering. They have a uniserial radula with dagger-shaped teeth, and the preradular tooth present Mikkelsen, Paula M. "Cylindrobulla and Ascobulla in the western Atlantic (Gastropoda, Opisthobranchia, Sacoglossa): systematic review, description of a new species, and phylogenetic reanalysis." Zoologica Scripta 27.1 (1998): 49-71 These snails have a foot that is relatively short (never extends beyond the shell), even when extended; the head and foot of the snail may be completely withdrawn back into the shell, and the shell then may be contracted by an anterior adductor muscle. The eyes of ''Ascobulla'' are located laterally, underneath the cephalic lobes . The gill of all shelled Sacoglossa is composed of a series of many parallel, ciliated lamellae, which are folds of the outer tissue layers of the mantle roof and cover the surface of the kidney.
Mikkelsen, Paula M. "Cylindrobulla and Ascobulla in the western Atlantic (Gastropoda, Opisthobranchia, Sacoglossa): systematic review, description of a new species, and phylogenetic reanalysis." Zoologica Scripta 27.1 (1998): 49-71.

Images from Mikkelsen, 1997:

# ''Ascobulla'' shell (4.0 mm length)
# ''Ascobulla'' shell, expanded (3.1 mm length)
# Apex of specimen in Image B
# Radula (toothed feeding structure) of specimen in Image B

Feeding

''Ascobulla'' species feed suctorially on species of the siphonalean green alga, Caulerpa. ''Ascobulla'' is often found to be protected by living near  Caulerpa species, and is able to reduce the toxicity that comes from these algae in order to protect itself.Gavagnin, M., Mollo, E., Montanaro, D. et al. Chemical Studies of Caribbean Sacoglossans: Dietary Relationships with Green Algae and Ecological Implications. J Chem Ecol 26, 1563–1578 (2000). https://doi-org.ezproxy.bu.edu/10.1023/A:1005526526884 “Suctorial” refers to the adaptation for sucking, or drawing up fluids and nutrients. In this sense, it behaves as a parasitic organism.  ''Ascobulla'', as well as all other sacoglossan species, have a distinctive, lengthened (preradular) tooth that coexists with an ascus (The ascus is a special sac-like structure that is used by slugs to store old teeth).Laetz, Elise, et al. "The Cylindrobulla/Ascobulla complex—unraveling problems in identification and adding to Cylindrobulla diversity (Gastropoda, Heterobranchia, Sacoglossa) by describing a new species." Zootaxa 3893.3 (2014): 339-362. This tooth is well-adapted for piercing and suckling. This tooth breaks through into the cytoplasmic fluid of the algae, which is suckled out by the organism.Amancic, S. "Ascobulla fragilis (Jeffers, 1856.) u priobalju Istre." (2020). Members of the ''Ascobulla'' all have increasing tooth size in their newest teeth, which is another characteristic that distinguishes them from Cylindrobulla.

Reproduction

''Ascobulla'' are hermaphroditic organisms, meaning they contain both male and female reproductive organs. ''Ascobulla'' features a penial stylet, which is able to be turned inside out and is located laterally on the right side. The penis itself is relatively large and muscular, so that it is capable of great extension. Only the tip of the penis is actually inserted during copulation. Copulation occurs at the female gential papilla, which is a region that contains the oviducal opening.

References

External links

photo

Volvatellidae
Taxa named by Eveline Du Bois-Reymond Marcus

{{Heterobranchia-stub