Marine Invertebrates of Bermuda Neapolitan Spurilla (Spurilla neapolitana) By Shaunte Henry and James B. Wood and Abel Valdivia (Eds) Taxonomy  Abstract  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links

Abstract


Spurilla neapolitana, also known as the Neapolitan Spurilla or Naples Spurilla, is a type of nudibranch that can be found in the Pacific and Atlantic Oceans. It is usually found in inter-tidal communities and among shallow tide pools. Although it is a member of the phylum Gastropoda, S. neapolitana has lost many of the gastropod traits, including the calcium carbonate shell and torsion of the visceral mass. One of the larger species of nudibranchs, S. neapolitana can reach lengths of up to 100mm. This fascinating creature uses its large chitonous jaws to feed on sea anemones. While feeding, it is able to ingest the anemones stinging nematocysts and protect itself by transporting the unfired nematocysts to dorsal projections called cerata. On average, the Neapolitan Spurilla possesses around 100 individual cera (singular form of cerata) on its dorsal side, allowing it to carry approximately 300,000 nematocysts for protection. S. neapolitana is naturally preyed upon by fish, echinoderms, and other mollusks. S. neapolitana can form symbiotic relationships with photosynthetic zooxanthallae by housing them in their cerata. On another note, the Neapolitan Spurilla is a simultaneous hermaphrodite and copulation if reciprocal. These creatures are semelparous, so they reproduce once in their entire life span and then die shortly after.

Taxononmy


Phylum: Mollusca
  Class: Gastropoda
    Order: Nudibranchia
      Family: Aoelidiidae

Spurilla neapolitana is a member of Opisthobranchia, a subclass of the phylum Mollusca. In general, members of the phylum Mollusca possess a hard calcium carbonate shell which is created by a specialized layer of tissue called the mantle. Between the mantle and the visceral mass lies the mantle cavity, which usually houses the gills, or ctenidia (Pechenik 2000). Gastropoda is the class in which Opisthobranchia is found. The defining characteristics of the class Gastropoda include torsion of the body, which is the twisting of the visceral mass so that the posterior end faces the same direction as the anterior end, and the presence of the operculum. The operculum is a proteinaceous shield attached to the foot of the organism that acts as a seal to close the aperture of the shell (Pechenik 2000). However, S. neapolitana has lost many of the “defining” characteristics of class Gastropoda. Members of Opisthobranchia have gone through a complete detorsion of the body and have lost the protective shell as well as the operculum. They have also lost the mantle cavity and ctenidia (Todd 1981, Pechenik 2000).

Within the subclass Opisthobranchia is the order Nudibranchia. Nudibranchia is defined by, as mentioned before, the loss of the calcium carbonate shell and proteinaceous operculum after metamorphosis, the loss of the mantle cavity and ctenidia, as well as the presence of cerata (Todd 1981, Pechenik 2000).Cerata are long dorsal projections that function in gas exchange and defense (Todd 1981). In addition to oral tentacles, nudibranchs also possess rhinopores, which are long anterior tentacles that are believed to function as chemo-receptors (Sterrer 1986, Pechenik 2000). Nudibranchia can then be divided up into four suborders: Dendronotacea, Doridacea, Arminacea, and Aeolidacea. S. neapolitana is a member of Aeolidacea. Aeolidaceans are characterized by their predation on cnidarians, the presence of numerous dorsal cerata, and the possession of a large jaw (Todd 1981, Pechenik 2000). Finally, S. neapolitana is located in the family Aeolidiidae (the aeolids) and is the only aeolid present in the waters located off the coast of Bermuda (Todd 1981, Sterrer 1986).



Habitat


Spurilla neapolitana can be found in many different places all over the world. It is common throughout the Atlantic Ocean, including the Mediterranean Sea, the Caribbean Sea, and the Sargasso Sea. It can also be found from the Central Pacific to the Eastern Pacific (Bertsch, 1984). There are records of S. neapolitana off the coast of Florida, Texas, Italy, Morocco, Spain, and Portugal, as well as the Canary Islands and Cape Verde (Eyster 1985, Marín 1991, Calado et al. 2003,). Although S. neapolitana does make its home in Bermudian waters, it is fairly uncommon (Sterrer 1986).Generally, S. neapolitana can be spotted in the rocky intertidal zone, in tide pools, among subtidal communities, or among brown algae. Occasionally it can also be found under large rocks (Eyster 1980, Todd 1981, Sterrer 1986).

Ecology


Anatomy

The Neapolitan Spurilla it is one of the larger species of nudibranch. Its length can range from 45-100mm (Eyster 1980, Sterrer 1986). It possesses approximately 100 cerata, (Greenwood and Mariscal 1984), on its dorsal side and long rhinopores. Cerata are long projections on the skin that function in gas exchange by increasing skin surface area and thus increasing diffusion. The presence of the cerata compensate for the lack of gills in the nudibranch (Todd 1981, Pechenik 2000). Cerata are used as a mode of defense by housing nematocysts, and also play a role in energy uptake by housing symbiotic bacteria (Conklin and Mariscal 1977, Day 1978, Greenwood and Mariscal 1984, Marín and Ros 1991). More details on both of these functions can be found in the ‘Defense Mechanisms’ and ‘symbiotic relationships’ section respectively. S. neapolitana also possess large jaws which allows them to feed on anemones (Todd 1981). S. neapolitana can range from light brown to pinkish in color. Its cerata are long and curved with white tips. The body, head, tentacles, and cerata are also covered with small dots (Sterrer 1986).

Feeding Behavior

S. neapolitana is carnivorous (Todd 1981). It is known to eat the actinians Anemonia viridis, Aiptasia mutabilis, Aiptasiogeton hyalinus, Aiptasia sp., Bunodeopsis sp., Haliplanella luciae, Condylactis gigantea (Marín and Ros, 1991), Anemonia sargassensis, Anthopleura kresbi, and Lebrunia danae (Conklin and Mariscal, 1977). S. neapolitana mainly feeds on the oral disk and tentacles of these anemones (Conklin and Mariscal 1977). In order to consume this type of prey S. neapolitana possess large chitinous jaws as well as a radula. The jaws serve the purpose of processing and grinding the food, while the radula acts as a conveyer belt, moving food into the esophagus (Todd 1981). S. neapolitana also possesses part of its digestive gland in its cerata. This is called the diverticula. The diverticula allows the nudibranch to have a slender body and allows the nudibranch to be more buoyant (Todd 1981). Because the skin of S. neapolitana is translucent, the contents of the divertucula can be seen through the skin. This allows the nudibranch to take on the color of the anemone that it is eating and thus blend in with its environment, providing the nudibranch with a mode of crypsis (Pontes 2000). The diverticula also functions in passing ingested nematocysts to the tips of the cerata, where they will be used for defensive purposes (Conklin and Mariscal 1977).

Conklin and Mariscal (1977) were able to observe the act of predation of S. neapolitana on several species of anemone. They found that before S. neapolitana is able to feed, it must first go through an acclimation process similar to that found in anemone fish. They observed that at the beginning of an attack, S. neapolitana is actively stung by the anemone. However, after the first few minutes of attack, the nudibranch is no longer stung (Conklin and Mariscal 1977). New research performed by Greenwood et al. (2004) has proven that nudibranchs are able to produce chemicals that specifically inhibit nematocyst discharge from anemones. They also discovered that nudibranchs are able to create different chemicals for each different species of anemone that it consumes (Greenwood et al. 2004). In other words, if a nudibranch preys upon three different species of anemones, that nudibranch will be able to create three different nematocyst-inhibating chemicals; one for each species of anemone. After this acclimation process, the nudibranch is free to consume as much anemone as necessary. Feeding will take place for about an hour, and the amount consumed can range from 25-100% of the anemone, depending on its size (Conklin and Mariscal 1977).

Symbiotic Relationships

Marín and Ros (1991) have found that S. neapolitana is able to ingest photosynthetic zooxanthellae from its cnidarian prey and incorporate them into their cerata. The cerata serve the purpose of increasing the surface area and sunlight absorption of the nudibranch in order to facilitate the creation of photosynthetic products created by zooxanthellae. Marín and Ros (1991) have suggested that this is a mutualistic relationship in which S. neapolitana gains photosynthetic products to help with body processes, while the nudibranch serves as dispersal method for zooxanthellae. Intact zooxanthellae have been found in the feces of S. neapolitana, so it is assumed that the nudibranch houses the algae in its body until it no longer has any need for it and then releases the intact cells in its feces. There is a regulated balance between the amount of zooxanthellae that is ingested and the amount of zooxanthellae that is released (Marín and Ros 1991).

Defense Mechanisms

Because S. neapolitana has lost its protective shell, it has had to develop a few clever defenses in order to protect itself from potential predators. Possibly one of the most fascinating defensive tactics of the Neapolitan Spurilla is its ability to not only consume the nematocysts of its prey, but also its ability to selectively use these nematocysts as its own protection. In other word, this animal is able to bypass the defense mechanisms of the animal which it is preying upon and then use those exact same defenses in order to protect itself (Conklin and Mariscal 1977, Todd 1981, Greenwood and Mariscal 1984). When the Neapolitan Spurilla consumes the nematocysts, it allows the diverticula to place the unfired nematocysts in the tips of the cerata (Greenwood and Mariscal 1984). Inside of the cerata, the nematocysts are placed in special sacs called cnidosacs (Greenwood and Mariscal 1984). Greenwood and Mariscal (1984) attribute the incorporation of unfired nematocysts to the ability of the nudibranch to actively select between mature and immature nematocysts. They found that the nudibranch is able to select for immature nematocysts and pass them through their gut with no risk of the nematocysts being fired off. S. neapolitana then passes the immature nematocysts to the cnidosacs where they are allowed to mature and be used for protection at a later time. However, Greenwood and Mariscal (1984) also found that the nudibranchs are able to pass mature nematocysts quickly through their digestive glands to their cnidosacs without firing off the nematocysts. The mechanism for this process is not yet fully understood. On average, one S. neapolitana can contain around 300,000 nematocysts (Greenwood and Mariscal 1984). Research has also shown that nudibranchs have the ability to change the type of nematocysts found in their bodies, depending on the species of anemone that they are consuming at the time. Usually the turnover of nematocyst types can take anywhere between 6 days to a month after the species of prey is changed (Day 1978, Greenwood and Mariscal 1984).

The standard behavior observed by S. neapolitana when attacked is a bristling and waving of cerata. This is done in order to possibly confuse its predators. They also tend to arch all of the cerata and direct them towards their enemies (Todd 1981). This increases the possibility that the enemy will be stung by the numerous nematocysts located in the tips. In addition to possessing nematocysts in their cerata, S. neapolitana is also able to autotomise its cerata in case of persistent irritation or attack (Todd 1981). They are also believed to create toxic chemicals in their mucus protected skin to deter predation. The natural predators of the Neapolitan Spurilla are fish, echinoderms, and other mollusks, including cephalopods (Todd 1981).

Reproduction

All nudibranchs are semelparous, meaning that they typically reproduce once in a lifetime and die shortly after (Todd 1981). They are also simultaneous hermaphrodites and fertilization is internal and involves reciprocal copulation. There has been no evidence of asexual reproduction or self-fertilization in these animals (Todd 1981). After copulation, the eggs are released by the adult in an egg mass, or ribbon, which is attached to substratum (Eyster 1980, Todd1981). These ribbons can contain over 10,000 separate eggs (Eyster 1980). The eggs develop after about 6 to 7 days and develop into plankotrophic larvae (Eyster 1980). The term plankotrophic refers to the developmental form in which the larvae feed and grow in the plankton, for a time ranging from a few weeks to a few months, until they have reached metamorphic competence (Goddard 2004). The larval form possesses all the ancestral characteristics of a gastropod, including a shell, an operculum, and a mantle cavity. They later lose these characteristics as they develop into adults (Todd 1981, Pechenik 2000, Goddard 2004).

Recent Research


Besides a few population studies, there is very little recent research being done specifically on S. neapolitana. As previously stated, Greenwood et al. (2004) recently proved that nudibranchs are able to produce substances in their mucus that inhibits the firing of nematocysts. I predict that within the next few years more research will be done in order to discover the specific properties of these chemicals. There have also been a study looking into the autotomy of aeolid cerata (Miller and Byrne 2000). The purpose of this study was to find the mode of regeneration in aeolid nudibranchs. Also of some interest, though a little bit dated, some research efforts were put into finding cancer fighting properties in the chemicals produced by nudibranch skin (Tucker 1985).

Commercial Importance


Spurilla neapolitana is not a commercially significant animal.

Bermuda Laws


The Fishery act of 1972 created 29 marine protected areas in which fishing and collecting of marine organisms is prohibited (Wood and Jackson 2005).Therefore, the Neapolitan Spurilla would be prtoected under this act if found in any of these marine protected areas. HOwever, Bermuda currently has no specific laws protecting S. neapolitana.

Personal Interest


I first became interested in S. neapolitana while trying to decide on an organism to research. I knew that I wanted to research a species of nudibranch, because I am interested in their ability to consume nematocysts and use them as a mode of defense. I chose to research S. neapolitana because it was one of the few Bermudian nudibranchs that has had a decent amount of research done on it and it is an overall beautiful creature.

References

Bertsch H. (1984) Distribution and radular morphology of various nudibranchs (gastropoda: opisthobranchia) from the Gulf of California, Mexico. Veliger 26: 264-273

Conklin E.J., Mariscal R.N. (1977) Feeding behavior, ceras structure, and nematocyst storage in the aeolid nudibranch, Spurilla neapolitana (Mollusca). Bull. Mar. Sci. 27: 658-667

Calado G., Malaquias M.A.E., Gavaia C., Cervera J.L., Megina C., Dayrat B., Camacho Y., Pola M., Grande C. (2003) New data on opisthobranchs (mollusca: gastropoda) from the southwestern coast of Portugal. Bol. Inst. Esp. Oceanogr. 19: 199-204

Day R.M., (1978) Selection and turnover of coelenterate nematocysts in some aeolid nudibranchs. Veliger 21: 104-109

Eyster L.S. (1980) Distribution and reproduction of shell-less opisthobranchs from South Carolina. Bull. Mar. Sci. 30: 580-599

Goddard J.H.R. (2004) Developmental mode in benthic opisthobranch molluscs from the northeast Pacific Ocean: feeding in a sea of plenty. Can. J. Zool. 82: 1954-1968

Greenwood P.G., Garry K., Hunter A., Jennings M. (2004) Adaptable defense: a nudibranch mucus inhibits nematocyst discharge and changes with prey type. Biol. Bull. 206: 113-120

Greenwood P.G., Mariscal R.N. (1984) Immature nematocyst incorporation by the aeolid nudibranch Spurilla neapolitana . Mar. Biol. 80: 35-38

Marín A., Ros J. (1991) Presence of intracellular zooxanthellae in Mediterranean nudibranchs. J. Moll. Stud. 57: 87-101

Miller J.A., Byrne M. (2000) Ceretal autotomy and regeneration in the aeolid nudibranch Phidiana crassicornis and the role of predators. Invert. Biol. 119: 167-176

Pechenik J.A. (2000) Biology of the invertebrates, fourth edition. McGraw-Hill, Boston. P. 203-276

Pontes M. (2000) Mediterranean nudibranchs: Spurilla neapolitana. Nudibranch News 2: 43

Todd C.D. (1981) The ecology of nudibranch molluscs. Oceanogr. Mar. Biol. Ann. Rev. 19: 141-234

Tucker J.B. (1985) Drugs from the sea spark renewed interests: Will new anticancer drugs come from marine organisms? Bioscience 35: 541-545

Sterrer W. (1986) Marine fauna and flora of Bermuda: a systematic guide to the identification of marine organisms. John Wiley and Sons Inc., New York. P. 451-455

Wood J.B., Jackson K.J. (2005) Bermuda. Caribbean Marine Biodiversity: the Known and the Unknown.In: DEStech Publications,Pennsylvania. P. 19-36

Links

Duke University Homepage
Sea Slug Forum
The Slug Site
The Guanacaste Nudibranch Project