The precise number of Okenia taxa inhabiting the Mediterranean Sea, as well as their general taxonomy, varies according to different specialists. So far, eight valid species have been reported from the area: Okenia aspersa (Alder & Hancock, 1845), Okenia cupella (Vogel & Schultz, 1970), Okenia elegans (Leuckart, 1828), Okenia hispanica Valdés & Ortea, 1995, Okenia impexa Er. Marcus, 1957, Okenia leachii (Alder & Hancock, 1854), Okenia mediterranea (Ihering, 1886), and Okenia zoobotryon (Smallwood, 1910). Of these, only three ( O . elegans , O . hispanica , and O . mediterranea ) have their type localities in the Mediterranean Sea, whereas the others were described from different biogeographic areas and later included in the Mediterranean biota. We carried out a review on Mediterranean Okenia species through an integrative approach, based on a wide literature search and a morphological and molecular analysis of available type material and samples collected recently. The present study confirmed the presence of O . aspersa , O . elegans , O . hispanica , and O . mediterranea in the Mediterranean Sea, although leaving remaining questions about some of those taxa. The distribution of O . cupella , O . impexa , and O . zoobotryon is limited to the western Atlantic, and of O . leachii to the eastern Atlantic. All specimens previously identified as O . cupella , O . impexa , and O . zoobotryon by different authors in the Mediterranean Sea were repeatedly misidentified. Thus, we describe Okenia problematica sp. nov. and Okenia longiductis sp. nov., from the “Mediterranean” Okenia cupella/impexa and O . zoobotryon . We also consider here Okenia pusilla Sordi, 1974 a nomen dubium and include a redescription of the holotype of O . cupella . A molecular phylogeny, including all the sequenced Okenia species, was performed in order to evaluate the evolutionary relationships of the newly described species with the other congeneric taxa.

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Trapania is the second largest genus belonging to the family Goniodorididae, of which most of the species are reported from Indo‐Pacific waters. To date, there are nine species of Trapania distributed along the temperate coasts of the East Atlantic Ocean and Mediterranean Sea: Trapania fusca, Trapania graeffei, Trapania hispalensis, Trapania lineata, Trapania maculata, Trapania orteai, Trapania pallida, Trapania sanctipetrensis and Trapania tartanella. However, the validity of some of these species has been problematic due to uncertain taxonomic characteristics used for the differentiation of the species. The genus Trapania has a very uniformly external morphology and very similar internal anatomy. As a consequence, the features most commonly used to differentiate species have been the colour pattern of the body and the morphology of the radula. In the present study, we perform a morphological and molecular revision of the East Atlantic‐Mediterranean species of the genus Trapania. Morphological analyses include dissections and scanning electron microscope photographs of radulae, labial cuticles and penises. Molecular work includes phylogenetic, species delimitation and haplotype network analyses. Our results bring doubt on the taxonomic characteristics used so far, suggesting that the richness of the North Eastern Atlantic‐Mediterranean species has been overestimated. Trapania hispalensis, T. lineata and T. pallida are shown to belong to the same taxa, with Trapania lineata as senior synonym.

Genetic connectivity plays a crucial role in shaping the geographic structure of species. Our aim in this study was to explore the pattern of genetic connectivity in Bursa scrobilator, an iconic marine caenogastropod with long-lived pelagic larvae. Our study was based on the analysis of DNA sequence data for the 658-bp barcoding fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene. This is the largest DNA sequence dataset assembled to date for B. scrobilator. These data confirm that the two recently described subspecies B. scrobilator scrobilator (Linnaeus, 1758), from the Mediterranean and Macaronesia, and B. s. coriacea (Reeve, 1844), from West Africa, constitute two evolutionarily significant units (ESUs). We found that for the nominal subspecies, the variation in morphology (shell, radula and gross anatomy) and DNA sequences was not geographically structured, and this agrees with what we would expect in a species with high connectivity at the larval stage. The divergence between the two subspecies cannot be easily explained by isolation by distance, and we would argue that one or more extrinsic factors may have played a role in isolating the two ESUs and maintaining that isolation.

Numerous faunistic and ecological studies have been conducted throughout the Indo-Pacific Ocean to assess its biodiversity. Despite the abundance of research, studies on the species that inhabit the Indo-Pacific are still necessary due to its extent and high species richness. The major species richness of the genus Okenia Menke, 1830 (Nudibranchia, Goniodorididae) is found in the Indo-Pacific Ocean, including 38 of 60 valid species. Nevertheless, this number does not represent the real biodiversity, since at least 20 more species are already reported in field-guides as undescribed species belonging to this genus. The systematics of the genus Okenia are still unclear since it has been the subject of only a few and incomplete studies. In the present paper, we describe five new Okenia species from the coastlines of Japan, Mozambique and Australia: Okenia aurorapapillata sp. nov., Okenia elisae sp. nov., Okenia nakanoae sp. nov., Okenia siderata sp. nov. and Okenia tenuifibrata sp. nov. Moreover, anatomical details not previously described of Okenia atkinsonorum, Okenia barnardi, Okenia cf. echinata, Okenia hallucigenia, Okenia hiroi, Okenia japonica, Okenia pellucida, Okenia pilosa and Okenia rhinorma are provided. New partial sequences of standard markers (COI, 16S rRNA and H3) were obtained and a phylogenetic analysis that included all species with available data was performed. ZOOBANK urn:lsid:zoobank.org:pub:28AE2536-A264–4194–8AE3-C430620572E7

Sigurdson (1991) erected the monospecific genus Murphydoris to include the species Murphydoris singaporensis. This species differed from the rest of the genera in Goniodorididae by the lack of lamellae on the rhinophores and gill branches around the anus. Since its original description, Murphydoris singaporensis has only been found in Singapore and Thailand. Recently, the paratypes of Murphydoris singaporensis were studied and compared with remaining type species of Goniodorididae, showing that the apomorphies of the genus were unclear and some undescribed species reported as Goniodoridella could belong to Murphydoris. In this study, we examined four undescribed species from the Indo-Pacific region. The internal anatomy was studied by dissections, and electron microscope photographs are included to show details of their radulae, labial cuticles and penises. One specimen was also studied under micro-computed tomography. In addition, mitochondrial and nuclear partial sequences of the species were obtained. As a result, we describe in detail four new species of Murphydoris: M. adusta sp. nov., M. cobbi sp. nov., M. maracabranchia sp. nov. and M. puncticulata sp. nov. We additionally present the first phylogenetic tree that includes sequences of Murphydoris.

Goniodoris is the third most diverse genus of the nudibranch family Goniodorididae. The genus has undergone several taxonomic changes, with c. one-third of the recognized species of Goniodoris having been synonymized (most of these are junior synonyms of genera from other families). In addition, Goniodoris includes other synonymized genera within it, such as Pelagella, which was erected for Doris pareti. This species was synonymized with Goniodoris castanea and the genus Pelagella went almost unnoticed. In the present study, we investigate the systematics of the genus Goniodoris by examining specimens of G. castanea from England and Spain, G. joubini from Hawaii and six undescribed Goniodoris species from Australia, the Philippines and Mozambique. The morphology of the new species is studied using dissections of the internal organs and scanning electron micrographs of the radulae, labial cuticles and the penis. We also carried out phylogenetic analyses using partial DNA sequences of mitochondrial and nuclear genes. These analyses show that the type species of Goniodoris, G. nodosa, is not a member of the clade constituted by the focal species of our study; the valid name for this clade is Pelagella. Six new species of Pelagella, P. albopunctata n. sp., P. balanoyensis n. sp., P. longicornis n. sp., P. scottjohnsoni n. sp., P. rubrobranchiata n. sp. and P. vitrea n. sp., are described.