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Lamellaria sp. (Montagu, 1815)
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Natasha Tay 2019
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Summary | |
From the moment the Lamellaria genus was formed, many of them have been misidentified and classified. They are often confused with nudibranchs due to their external non-retractile mantle, however the presence of an internal shell and absence of marginal teeth on the radula distinguishes this genus from the others (Kazmi, 1995). They are known for mimicking the colour of their ascidian food source for camouflage and are generally found living on or near these ascidians (Doneddu and Manunza, 1993).
Unfortunately, limited research has been done on this genus, making it difficult to identify the species. After much consideration, I speculate that the specimen is Lamellaria perspicua due to the shell structure, which is a distinguishing characteristic, however I am still unsure as much research is still required to fully identify this species. Thus, I would be focusing slightly more on L. perspicua but also talking about the genus itself.
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Physical Description | |
When the specimen was alive, the dorsal surface of the mantle was white with brownish-black stipples and looked porous, which closely resembled the oral apertures of zooids, allowing it to camouflage with the colonial ascidian that it was found on. Under the mantle a thin, flattened, auriform white shell could be seen under it. A short anterior siphon was also seen on the dorsal surface. To the untrained eye, it would have been easily mistaken for a nudibranch (Kazmi, 1995).The ventral surface contained the muscular foot used for locomotion, the head with two elongated tentacles and minute eyes at the base and these are both white in colour as well.
After fixing it in 4% PFA, the colouration on the mantle was lost, making it more translucent and the growth lines on the shell more visible. The shell is approximately 5 mm long and consists of one to two whorls. L. perspicua has also been recorded to have orange and light brown coloured mantles, thus making it difficult to identify the species based on just external morphology alone.
The radula was removed from the specimen however, it was enclosed by the buccal cavity, thus I was unable to identify the species based on the radula. According to Kazmi,1995, the radula has 67 rows of teeth, of which 4-5 distal most rows are whitish and the rachidean (Figure 8 part A) are almost equal and the lateral tooth (Figure 8 part B) has 4-5 strong inner and 15 outer denticles, gradually decreasing in size towards apex.
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Ecology | |
Lamellaria sp. use colonial ascidians as a food source and incubatory pouches for their eggs,though there has been little research on the latter (Dias and Delboni, 2008). This would have negative impacts on the ascidians as the egg pouches increase in size, the ascidian zooids would be affected via reduction of their filtering abilities, thus causing death to the zooids in the area or even the whole colony (Dias and Delboni, 2008). This could cause issues especially if the ascidians are endangered or important to that ecosystem.
Lamellariid gastropods mimic the colour and texture of the ascidians they feed and live on, thus making it difficult for scientists to distinguish the species on external appearances alone as one species can have various morphological differences (Quieroz and Sales, 2016;Dias and Delboni, 2008). However, morphology of the shell and radula are used as distinguishing characteristics to identify species from one another (Kazmi,1995; Bois-Reymond Marcus and Marcus, 1963; Marcus 1956).
There has been debate on whether this relationship between the Lamellaria sp. and ascidians are parasitic or symbiotic (sensu lato) as there has not been much research on the negative impacts on the hosts of Lamellaria sp. (Quieroz andSales, 2016; Dias and Delboni, 2008).
For the specimens collected on the ARMS plate from Amity point, North Stradbroke Island, the organisms have been found on ascidians that possibly belong to the family Didemnidae.
They are usually found in intertidal and subtidal zones and can be located under rocks in rock pools and clefts.They can also be found on stony seabeds and rocky bottoms down to 1200m (Queiroz and Sales, 2016; Morley and Hayward, 2015; Taki, 1972) and are usually living close to or even on the specific ascidians that they feed on (Doneddu and Manunza, 1993).
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Life History and Behaviour |
Defence Mechanisms | |
When disturbed, Lamellaria sp. secrete strong sulphuric acid (pH 1) through their skin and this is believed to be their defense mechanism as tests have shown that fish would not consume food that has been soaked in acid. Histological preparations have shown that these acid glands are subepidermal multicellular sacs that open to the permanent pores found on the mantle of the Lamellaria sp. A network of smooth muscle fibers surrounds each acid sac and is thought to assist in the secretion of acid (Thompson, 1969).
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Reproduction | |
According to Fretter, 1946, the echinospira larvae of Lamellaria perspicua are found in the plankton in all stages of development throughout the year, but during spring and summer, the population of larvae would increase drastically. The males would pass seminal fluid through a filamentous tip into the ducts of the spermotheca of the female (Fretter, 1946).
Once ready to lay their eggs, the female would need to locate a colonial ascidian host (Quieroz and Sales,2016) and would then proceed to stiffen the mantle and erect the body, followed by strong contractions which allows the female’s mouth to be placed on the ascidian to create a hole. The posterior region would then be placed in the hole and a small capsule with large number of eggs would be embedded. This process requires two hours, resulting in about 3 to 53 egg pouches and 13 to 164 eggs within each pouch. These egg pouches have plugs at the surface and that is where the echinospira larvae would eventually emerge (Dias and Delboni, 2008). Even though there are so many larvae produced, these gastropods would rather live a solitary life (Taki, 1972).
Temperature seems to play a role in the time taken for these echinospira larvae to developas the larvae took 6 days to develop at 10oC in the laboratory as observed in Dias and Delboni (2008), while it took larvae of L. sternsii 28 to 35 days to develop in 23o to 26oC in the wild as observed in Page (2002).
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Lamellarins | |
Lamellarins,being a natural product, is of interest due to their potent cytotoxic activities which have been shown effective against multidrug-resistant tumour cell lines and prostate cancer cells. These polyaromatic alkaloids known have been found in Lamellaria sp. and have recently been found in didemnid ascidians. As Lamellaria sp. feed on colonial ascidians, researchers speculate that they obtained these compounds through ingesting the colonial ascidians (Chittchang and Theppawong, 2018; Facompré et al. 2003).Uptake of these compounds could be due to another form of chemical defense however, there is lack of research in this area.
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Anatomy and Physiology | |
The shell is produced by glands located at the bottom of the shell chamber and the muscular foot is connected to the shell via two bundles of muscle fibres. The underside of the mantle has a network of blood vessels and muscles and these were possibly used for respiratory or even defensive functions (Marcus, 1956). The mantle also contains acid glands that have smooth muscle fibres surrounding them (Thompson,1969). The nerve ring lies together with the oesophagus on the left. The eyes have vesicles with lens and the statocysts lie near the pedal ganglia and contain a single statolith. Respiratory surface of the female is more than thrice that of the male due to the increase in length of the branchial leafletsin females. Presence of proboscis and jaw and the radula are yellow in front and colourless behind. The oesophagus enters the foliate stomach from the front and continue through as a ciliated gutter. The reproductive organs are a blind tube that is coiled, ciliated and glandular and the shape varies between species.
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Biogeographic Distribution | |
Lamellaria sp. are known to be a cosmopolitan genus, thus it could befound in a multitude of places (Marcus,1956). Studies have found them in placessuch as Brazil, North America and Japan (Dias and Delboni, 2008; Taki, 1972; Bois-Reymondand Marcus, 1963). However, due to the lack of study on the genus, it is difficult to identify the species based on geographical location (Marcus,1956).
In Australia, the studies on Lamellaria sp. have been scarce, and some papers that have studied the genushave not identified their specimens down to species. Thus, it is possible that there are unknown Lamellaria sp. in the Great Barrier Reef.
L. perspicua, in particular havebeen found in areas such as Florida, Miami, South America, theEastern Atlantic Ocean, including the Mediterranean Sea but not the Arctic, andthe Indo-West Pacific Ocean, where Australia is located (Bois-Reymond andMarcus, 1963). Thus, increasing the possibility that the specimen collected is indeed L. perspicua.
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Evolution and Systematics |
Taxonomy | |
- Kingdom: Animalia
- Phylum: Mollusca
- Class: Gastropoda
- Subclass: Caenogastropoda
- Order: Littorinimorpha
- Superfamily: Velutinoidea
- Family: Velutinidae
- Subfamily: Lamellariinae
- Genus: Lamellaria
- Species: Lamellaria perspicua
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Evolution | |
Gastropods are generally herbivores and use their radula to scrape algae and organic detritus off hard substrates. But the Lamellaria sp. have evolved into a predatory group which would in turn change the morphology of the radula and foregut. These changes can be observed through their larval and metamorphic development (Page, 2002).
It is difficult to obtain evolutionary insight based on the overall morphology of the organism due to the soft body plan that they have, which would decompose easily. Evolutionary insight would only be able to be observed through their development, genetics (such as fossil genes) or even through the shell and radula, which tend to be more hardier.
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Conservation and Threats | |
Lack of research limits us to put conservation efforts into place if needed. The threats that the genus face is unknown however, anthropological impacts such as global warming,imbalance in the ecosystem such as algal blooms or introduction of invasive species could possibly affect the population.
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References | |
Bois-Reymond Marcus, E.D. and Marcus, E., 1963.Opisthobranchs from the lesser Antilles. Studies on the Fauna of Curaçao andother Caribbean Islands, 19(1), pp.1-76.
Chittchang, M. and Theppawong, A., 2018. An Overview of theMultifaceted Lessons Learned from Marine-Derived Bioactive Lamellarin NaturalProducts. In Studies in Natural Products Chemistry(Vol. 61, pp. 411-460).Elsevier.
Dias, G.M. and Delboni, C.G.M., 2008. Colour polymorphismand oviposition habits of Lamellaria mopsicolor. Marine Biodiversity Records,1.
Doneddu, Mauro & Manunza, Bruno., 1993. Lamellariaperspicua (Linnè, 1758). Enumeratio Molluscorum Maris Nostri.
Facompré, M., Tardy, C., Bal-Mahieu, C., Colson, P., Perez,C., Manzanares, I., Cuevas, C. and Bailly, C., 2003. Lamellarin D: a novelpotent inhibitor of topoisomerase I. Cancer research, 63(21), pp.7392-7399.
Kazmi, Q.B., 1995. A note on Lamellaria perspicua(Mesogastropoda, Gastropoda) collected from Karachi coast. Pakistan Journal ofMarine Sciences, 4(2), pp.155-157.
Marcus, E.D.B.R., 1956. On some Prosobranchia from the coastof São Paulo. Boletim do Instituto Oceanográfico, 7(1-2), pp.03-29.
Morley, M.S. and Hayward,B.W., 2015. Intertidal records of ‘sea slugs’(nudibranchs and alliedopisthobranch gastropods) from northern North Island, New Zealand. Recordsof the Auckland Museum, 50, pp.33-75.
Page, L.R., 2002. Larval and metamorphic development of theforegut and proboscis in the caenogastropod Marsenina (Lamellaria) stearnsii.Journal of morphology, 252(2), pp.202-217.
Taki, I., 1972. ON A NEW SPECIES OF LAMELLARIA (L. UTINOMII,N. SP.) FROM SHIRAHAMA, WAKAYAMA PREFECTURE, JAPAN (MOLL., GASTROPODA).
Thompson, T.E., 1969. Acid secretion in the Pacific Oceangastropods. Australian Journal of Zoology, 17(5), pp.755-764.
QUEIROZ, V. and SALES, L., 2016. A new color pattern for theascidian-symbiontic Lamellaria mopsicolor (Mollusca: Caenogastropoda) innortheastern Brazil, with a discussion of its symbiotic lifestyle. Pan-AmericanJournal of Aquatic Sciences, 11(2), pp.123-129.
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