Phyllidiidae (Nudibranchia, Heterobranchia, Gastropoda): an integrative taxonomic approach including chemical analyses

Abstract

Members of the widely distributed and common nudibranch family Phyllidiidae are often easily spotted in the marine environment because of their conspicuous colours and obvious presence on the reef. They are interesting with regard to their defensive chemical compounds that may lead to new drug discoveries. Despite their abundance, the family is also well known for its taxonomic problems and the difficulties in species identification due to very similarly coloured species and lack of morphological characters. In this study, phyllidiid species were analysed using an integrative approach. Molecular analysis of the mitochondrial genes 16S and CO1 was utilised, running phylogenetic analyses, species delimitation tests, and haplotype network analyses. Additionally, for the first time, external morphological characters were analysed, museum material was re-analysed, and chemical profiles were applied for characterising species. The analyses are based on sequences of 598 specimens collected in Indonesia by the team, with the addition of published sequences available on GenBank. This study comprises 11 species of Phyllidia, seven species of Phyllidiopsis, and at least 14 species of Phyllidiella. Moreover, 11 species belonging to these three genera are probably new to science, Phyllidiopsis pipeki is synonymised with P. krempfi, and Phyllidiella albonigra is resurrected. Some of the external colouration previously used for species identification is shown to not be valid, but alternative characters are provided for most species. Chemical analyses led to species characterisation in a few examples, indicating that these species use particular sponge species as food; however, many species show a broad array of compounds and are therefore characterised more by their composition or profile than by distinct or unique compounds.

Systematic Review of Chemical and Biological Activity Studies of Extracts and Isolated Compounds From Nudibranchs

“…Okino et al [81] suggested that sesquiterpenes present in the mucus may serve as antifouling agents to keep exposed surfaces free of epibionts, and that Phyllidia compounds also utilize a dense layer of calcareous spicules arranged on the mantle and foot, which provide structural support and make them difficult to eat, acting as a defense mechanism. The most detected secondary metabolites in the three analyzed Phyllidia genera are sponge-derived sesquiterpene isonitrile and related compounds, which agrees with chemical investigations prior to the Papu et al [82] and a common feature of all chemically analyzed Phyllidia species is the presence of brominated natural products that have moderate polarity.…”

Keanekaragaman dan Kelimpahan Nudibranch di Pantai Penimbangan Buleleng Bali

“…Analisis kimia menunjukkan bahwa jenis ini menggunakan jenis sponge tertentu sebagai makanan; namun, banyak jenis menunjukkan susunan yang luas senyawa dan karena itu lebih dicirikan oleh komposisi atau profilnya daripada senyawa yang berbeda atau unik. (Papu, et al, 2021) Kelompok nudibranch yang ditemukan dalam jumlah yang relatif lebih sedikit dari kelompok pertama, terdiri dari jenis Baeolidia nodosa, Berghia coerulescens, Chelidonura pallida, Bornella sp, Halgerda carlsoni, Jorunna funebris, Asteronotus cespitosus, Thuridilla bayeri, Thuridill. T. gracilis, Caloria indica, Flabellina exoptata, Hexabranchus sanguineus, Ercolania sp, dan Pleurobranchus forskalii, seperti ditunjukkan dalam Tabel 2.…”