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Impact of artificial coastal protection structures on Ascidians settlement along the Tamil Nadu coast, India

Jebarathanam Prince Prakash Jebakumar, Nandhagopal Ganesan, Rajan Babu Bose, Ragumaran Shunmugavel, Ramakritinan Chokalingam Muthiah, Ali Abdul Jaffar, Arshan Mohammed Kaleem, Ravichandran Vijaya

Oceanologia

2019

No. 61 (1)

60--67

Ascidians are one of the dominant marine sedentary filter feeders recorded more frequently as introduced species than other taxa. It is renowned that artificial structures offer novel niches to the non-native species. A yearlong investigation was carried out to understand the role of ascidian colonization on various artificial structures located along 84 stations stretched on the 1076 km long Tamil Nadu coast of South India. It revealed the occurrence of 26 ascidian species, among these18 specimens were identified to species level, 8 were identified to genus level based on morphological characters. As on origin and nativity, out of the total 26,3 species were classified as introduced, 8 specieswere classifiedas native and 15 as cryptogenic species. Interestingly, Polyclinum isipingense and Diplosoma variostigmatumwere reported first time inIndianwaters.Thecryptogenic and colonial forms of ascidians are dominant in the artificial structures. There were significant differences observed between artificial structure type, geographic locations ( p = 0.0071) and between ascidians forms as well as geographic areas ( p = 0.00375). This study also confirms the artificial structures offer new niches for non-native ascidian colonization. The influence of the substrate (structure type) aswell as geographic locations on the biotic assemblage was also observed.

Distribution of the sea squirt Ecteinascidia thurstoni Herdman, 1890 (Ascidiacea: Perophoridae) along Suez Canal and Egyptian Red Sea coasts

Ali A-F., Gab-Alla A

Oceanologia

2008

No. 50 (2)

239-253

Ecteinascidia thurstoni is a colonial sea squirt. It has a seasonal rhythm and a tropical and subtropical distribution; it is usually present during the summer months. It synthesizes a group of molecules called ecteinascidins. One of these is ET-743, a compound that has a most original anti-tumoral activity and is today considered to be one of the most promising substances effective against various solid-type tumors (currently sold under the trade name of Yondelis for the treatment of sarcomas and related tumors; it is undergoing phase II/III clinical trails for other kinds of tumors). Worldwide, Ecteinascidia species represent the only available source of this bioactive compound, which was first discovered in E. turbinata. During the present study, the ecology of E. thurstoni along the Suez Canal and Red Sea was investigated. Its populations were observed to be highly gregarious due in part to their low larval dispersal, which is very localized; larvae therefore tend to settle close to their parent colonies. It is only recorded in shallow waters (0.5-1.5 m) as an epiphyte on the pneumatophores of mangroves by the Red Sea, on the pilings of jetties, and the metal or cement banks of the Suez Canal. The morphometric characteristics (zooid length, zooid weight, colony weight) of the Suez Canal population differ significantly from those of the Red Sea. Studying the distribution of this species and locating its different populations along the Suez Canal and Red Sea could help to characterize their genetics, chemistry and bacterial communities at different isolated locations. Ultimately, this will help to define the sources of ET-743 and hence promote its biosynthesis on a commercial scale.