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BACKGROUND: How novel phenotypes originate from conserved genes, processes, and tissues remains a major question in biology. Research that sets out to answer this question often focuses on the conserved genes and processes involved, an approach that explicitly excludes the impact of genetic elements that may be classified as clade-specific, even though many of these genes are known to be important for many novel, or clade-restricted, phenotypes. This is especially true for understudied phyla such as mollusks, where limited genomic and functional biology resources for members of this phylum have long hindered assessments of genetic homology and function. To address this gap, we constructed a chromosome-level genome for the gastropod Berghia stephanieae (Valdés, 2005) to investigate the expression of clade-specific genes across both novel and conserved tissue types in this species. RESULTS: The final assembled and filtered Berghia genome is comparable to other high-quality mollusk genomes in terms of size (1.05 Gb) and number of predicted genes (24,960 genes) and is highly contiguous. The proportion of upregulated, clade-specific genes varied across tissues, but with no clear trend between the proportion of clade-specific genes and the novelty of the tissue. However, more complex tissue like the brain had the highest total number of upregulated, clade-specific genes, though the ratio of upregulated clade-specific genes to the total number of upregulated genes was low. CONCLUSIONS: Our results, when combined with previous research on the impact of novel genes on phenotypic evolution, highlight the fact that the complexity of the novel tissue or behavior, the type of novelty, and the developmental timing of evolutionary modifications will all influence how novel and conserved genes interact to generate diversity.

Kumar JSY, Sen A, Raghunathan C, Venkatraman C. 2024. Shallow water sea slugs (Gastropoda: Heterobranchia) from Andhra Pradesh, India. Nusantara Bioscience 16: 154-168. The current manuscript explores the initial underwater survey findings, revealing 19 heterobranch species across 10 genera, 6 families, 2 suborders, one order, and one superorder within the Visakhapatnam coast of Andhra Pradesh, India. While, the heterobranchs fauna of Andhra Pradesh has been studied by several authors, it has been observed that underwater surveys to discover this marine group are lacking from the region, and therefore, the present study has been done. These species from the study site include Coryphellina exoptata, Pteraeolidia semperi, Dendrodoris krusenstenii, Doriprismatica atromarginata, Glossodoris sp. cf. cincta, G. rufomarginata, Goniobranchus alius, G. setoensis, G. fidelis, G. trimarginatus, Hypselodoris bullockii, H. nigrostriata, H. sagamiensis, H. kanga, Jorunna funebris, Phyllidia ocellata, P. polkadotsa, Phyllidiopsis phiphiensis, and Elysia marginata. Remarkably, 13 of these heterobranchs species are documented for the first time in the Andhra Pradesh region, with 12 belonging to the order Nudibranchia and one to the superorder Sacoglossa. The manuscript provides a comprehensive analysis of morphometric characteristics, detailed descriptions, photography, and distribution trends of 19 heterobranchs species, as well as a comprehensive literature record of sea slugs found in Andhra Pradesh, India. Sea slugs, being the butterflies of the ocean, are a great part of the ecosystem, although based on economic valuation, they are regarded as a low-value bycatch, trash. The bottom trawl is one of the major threats to the habitat destruction for these animals. Thus, the habitats along the Andhra coastline should be known so that fishing activities in these parts could be restricted for the better survival of sea slugs. [ABSTRACT FROM AUTHOR]

The "escape and radiate" hypothesis predicts that once species have evolved aposematism, defended species can utilize more visually diverse visual backgrounds as they "escape" the need to be well camouflaged. This enables species to explore new ecological niches, resulting in increased diversification rates. To test this hypothesis "escape" component, we examined whether the background habitats of 12 nudibranch mollusk species differed among species depending on the presence and strength of chemical defenses. We obtained a rich array of color pattern statistics using quantitative color pattern analysis to analyze backgrounds viewed through the eyes of a potential predator (triggerfish, Rhinecanthus aculeatus). Color pattern analysis was done at viewing distances simulating an escalating predation sequence. We identified 4 latent factors comprising 17 noncorrelated color pattern parameters, which captured the among-species variability associated with differences in chemical defenses. We found that chemically defended species, indeed, were found on visually distinct backgrounds with increased color and luminance contrast, independent of viewing distance. However, we found no evidence for increased among-species background diversity coinciding with the presence and strength of chemical defenses. Our results agree with the "escape and radiate" hypothesis, suggesting that potent chemical defenses in Dorid nudibranchs coincide with spatiochromatic differences of visual background habitats perceived by potential predators. [ABSTRACT FROM AUTHOR]

Vayssierea is an understudied nudibranch genus characterized by its orange colouration and small size (up to 5 mm in length). To date, there are four described species, distributed in the Indo-Pacific Ocean. Here, individuals of Vayssierea were recorded for the first time in the North Atlantic Ocean on the Canary Islands (Spain). This study aims to evaluate the systematic and taxonomic status and distribution of the genus through multilocus phylogenetic, morphological, and radular analyses. Phylogenetic results show the monophyly of Vayssierea and evidence indicating that the genus is included in the new subfamily Okadaiinae stat. nov. within Polyceridae. According to species delimitation tests, four different species have been sequenced from Russia to Australia, in addition to our new records in the Atlantic Ocean, but more information is needed to identify the species. Nevertheless, our specimens from the Canary Islands belong to two different species, one of which is identical to the Australian species. Bearing in mind that they lack a planktonic larval stage; we hypothesize that they arrived by shipping transportation or aquarium releases, becoming a non-indigenous species of the Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Calcareous skeletal structures are common among different invertebrate groups, including Porifera, Cnidaria, Platyhelminthes, Mollusca, and Echinodermata. They appear externally as shells, plates, or scales, or internally as subepidermal spicules. Although typically formed outside of the cells, in one class of gastropod molluscs, the Heterobranchia, subepidermal and intracellular spicules are found—a rare case, at least for the molluscs. This type of spicules is present in several phylogenetically distant groups of heterobranch molluscs (Rhodopemorpha, Acochlidimorpha, and Nudibranchia), each different in terms of morphology and autecology. This raises questions about the origin and homology of subepidermal spicules in heterobranch molluscs. To answer these questions, understanding the process of spicule formation is crucial. This is impeded by insufficient data on the fine structure of the subepidermal spicules and adjacent epithelia. To address this problem, we carried out a comprehensive morphological study of subepidermal spicules and the body wall in one species of Acochlidimorpha. We revealed variations in the cellular composition of the epidermis, musculature organization, and spicules' arrangement, which most likely reflect the different functional roles of the spicule complex within Heterobranchia representatives. However, the obtained data are insufficient to answer the question of the origin of spicules and their homology within Heterobranchia. [ABSTRACT FROM AUTHOR]

Species of the genus Eubranchus Forbes, 1838 (Mollusca: Gastropoda: Nudibranchia) are common faunistic elements of boreal benthic ecosystems, associated with hydroid communities. Recent studies have suggested that the widely distributed trans-Arctic E. rupium (Møller, 1842) constitutes a complex of at least three candidate species, but the detailed taxonomy of the complex remains unresolved. The purpose of the present paper is to conduct an integrative taxonomic study including molecular genetic methods (a phylogenetic analysis using COI , 16S rRNA and histone H3 with application of species delimitation methods) and morphological study (light and scanning electron microscopy) of E. rupium and closely related species. The specific aims of this study were to establish the species boundaries, morphological variability, and the phylogeographic structure within this group. The phylogeographic analysis included a TCS -based network analysis, an analysis of molecular variance (AMOVA), divergence time estimations, and ancestral area reconstructions. We demonstrate that specimens initially identified as E. rupium included three distinctive species: the nominal E. rupium with an amphiboreal range, the new species Eubranchus novik sp. nov. from the Sea of Japan, for which a taxonomic description is provided in this paper, and Eubranchus sp. from the northern Kuril Islands, which requires the collection and study of additional material for formal description. Our results confirm the amphiboreal distribution of E. rupium , as no geographic structure was found across Pacific, Arctic and Atlantic populations, and the results of the AMOVA analysis showed no differences between groups of samples from different geographic regions. The divergence of the ' Eubrancus rupium species complex' is estimated from the late Miocene or the Miocene–Pliocene boundary to the late Pliocene. It is hypothesised that the most probable ancestral region for the Eubranchus rupium species complex is the north-western Pacific, and the subsequent speciation likely occurred due to dispersal followed by allopatric speciation. ZooBank: Species of the genus Eubranchus Forbes, 1838 are common in boreal benthic ecosystems. Recent studies suggest the trans-Arctic Eubranchus rupium (Møller, 1842) is a species complex. This paper conducts an integrative taxonomic study of Eubranchus rupium and related species, confirming its amphiboreal distribution. The divergence of the species complex is estimated from the late Miocene or the Miocene–Pliocene boundary to the late Pliocene with the north-western Pacific as the probable ancestral region, followed by dispersal and allopatric speciation. (Image credit: Darya Grishina.) [ABSTRACT FROM AUTHOR]

Sea slugs of the family Chromodorididae (Nudibranchia, Gastropoda, Mollusca) have garnered attention by researchers and hobbyists alike for their bright and variable color patterns. However, the chromodorid life cycle has yet to be fully elucidated as there exist no reports of their rearing in the laboratory. Here, we report the rearing of Hypselodoris festiva from eggs to adults, where we categorized their post-settlement growth patterns from juvenile to adult stages. Body coloration appeared around 36 days, and organogenesis of vital adult organs began within 42 days after hatching. The anus of H. festiva was observed to change from a ventral to dorsal position during juvenile growth. Individuals reached sexual maturity after six months post-hatching, with successful mating and spawning observed ex situ. This study outlines comprehensive rearing methods and life cycle staging that could be applied to other chromodorid species. We propose H. festiva as a model organism for chromodorid research, with this research contributing to the progress of developmental and evolutionary research on sea slugs. [ABSTRACT FROM AUTHOR]

The selective factors that shape phenotypic diversity in prey communities with aposematic animals are diverse and coincide with similar diversity in the strength of underlying secondary defences. However, quantitative assessments of colour pattern variation and the strength of chemical defences in assemblages of aposematic species are lacking. We quantified colour pattern diversity using quantitative colour pattern analysis (QCPA) in 13 dorid nudibranch species (Infraorder: Doridoidei) that varied in the strength of their chemical defences. We accounted for the physiological properties of a potential predator's visual system (a triggerfish, Rhinecanthus aculeatus) and modelled the appearance of nudibranchs from multiple viewing distances (2 and 10 cm). We identified distinct colour pattern properties associated with the presence and strength of chemical defences. Specifically, increases in chemical defences indicated increases in colour pattern boldness (i.e. visual contrast elicited via either or potentially coinciding chromatic, achromatic and/or spatial contrast). Colour patterns were also less variable among species with chemical defences when compared to undefended species. Our results indicate correlations between secondary defences and diverse, bold colouration while showing that chemical defences coincide with decreased colour pattern variability among species. Our study suggests that complex spatiochromatic properties of colour patterns perceived by potential predators can be used to make inferences on the presence and strength of chemical defences. [ABSTRACT FROM AUTHOR]

During a diving expedition through northern Norway, a total of 25 heterobranchiate taxa were collected, and additional data on distribution and ecology were given. Cumanotus beaumonti and Flabellina borealis are recorded for the first time since Odhner (1907), (1922) on the Norwegian coast, and the distribution of eight heterobranch taxa were re-evaluated. By using SCUBA diving as a sampling method, it is proved that the diversity and distribution of heterobranchs is poorly known in northern Norwegian waters, as the results show that large quantities of specimens, as well as a significant number of taxa, are found at each locality. The significance of diving for studying heterobranchs is emphasized. Apart from new records of heterobranchs and enhanced knowledge of biodiversity and biogeography of this group in northern Norway, this paper presents previous published literature where heterobranch taxa are mentioned for northern Norway.

The chromodorid nudibranch Goniobranchus aureopurpureus (Collingwood, 1881) is characterized by numerous yellow spots on a white mantle that is bordered with purple spots. It is believed to be widely distributed in both the Northern and Southern Hemispheres in the West Pacific, showing color varieties in a more-or-less geographically coherent manner. Chromodoris variata Risbec, 1928 (type locality: New Caledonia) has been considered a synonym. In addition, three, similar-looking congeners have been proposed as synonymous with G. aureopurpureus: G. albopustulosus (Pease, 1860) (type locality: Hawaii), G. alius (Rudman, 1987) (type locality: Tanzania), and G. rufomaculatus (Pease, 1871) (type locality: French Polynesia). To test the synonymies proposed above, we performed maximum-likelihood and Bayesian-inference analyses utilizing partial sequences of the cytochrome c oxidase subunit I (COI) and 16S rRNA genes. The taxon sampling included a specimen of G. aureopurpureus newly collected in Hokkaido, Japan, along with other sequences of Goniobranchus deposited in public databases (31 specimens representing 22 species), including one identified as ‘Chromodoris aureopurpurea’ from New South Wales, Australia; G. albopustulosus from Hawaii; and two ‘Chromodoris rufomaculata’ from Guam and the Mariana Islands. Goniobranchus aureopurpureus from Japan and from Australia were sister taxa in the resulting trees but differed from each other by 8.6% in terms of 658-bp COI, suggesting that these two represent closely-related but different biological entities. For the Australian taxon, Goniobranchus cf. variatus comb. nov. is proposed herein. Goniobranchus albopustulosus and G. rufomaculatus were not closely related to the G. aureopurpureus–G. cf. variatus clade, rejecting the hypothesis that they are synonymous with either of these species. However, G. albopustulosus and G. rufomaculatus appeared to comprise a single biological entity, warranting further investigation of this potential synonymy. The placement of the Indian Ocean G. alius also remains to be tested.

The Mediterranean Sea is known to be a hot spot for marine biodiversity, especially if considering the highly specialized Heterobranchia mollusks. In recent years, there has been increasing effort to fill some knowledge gaps existing on Mediterranean heterobranch diversity, but, to date, several potentially interesting habitats remain unexplored. In fact, most studies have been focused on sea slugs inhabiting coastal areas and lakes, but those living in extremely variable areas like Mediterranean rocky tide pools remain almost completely ignored even if it is reported worldwide that they can host a high sea slug diversity. In this context, the rocky tide pool system near the 'Passetto' urban beach (Ancona, Italy) in the North Adriatic Sea (Mediterranean Sea) represents a biodiversity hot spot, highlighting the importance of the conservation of this peculiar habitat. A preliminary quantitative survey on the associated Heterobranchia unveiled a thriving community residing in this limited and fragile habitat, and it inspired a more detailed investigation as performed in the present study. In order to reveal the presence of species that have gone unnoticed, an in-depth study was carried out between 2018 and 2022, which aimed to amplify the knowledge on this vulnerable environment and the fauna associated with this as yet poorly known habitat. Tide pooling activities corroborated by photographic analyses allowed the recording of 45 taxa in total and the addition of 25 species to the previously known list. Within those, (i) two species were potentially new to science, (ii) one was recorded in the Mediterranean Sea for the first time, (iii) two species were added to the Italian fauna, and (iv) one species constituted a new record for Sector 9 of the Italian Seas. [ABSTRACT FROM AUTHOR]

Nudibranchs are mostly predators preying on a variety of invertebrates. The dietary preferences of tropical nudibranchs were studied by the method of fatty acid trophic markers (FATM) in order to for better understanding of their trophic ecology. For this, the fatty acid profiles of two nudibranch species from the South China Sea, Doriprismatica atromarginata (Cuvier, 1804) and Jorunna funebris (Kelaart, 1859), were analyzed and trophic markers were identified. The high level of very long chain fatty acids (from C24 to C28), which are characteristic of sponges, in nudibranchs was evidence of their predation on sponges. However, the distribution of these components differed significantly between the species. The acids 24:2Δ5,9, 25:2Δ5,9, 26:2Δ9,19, and especially 26:2Δ5,9 dominated in D. atromarginata, but were not found in J. funebris that was rich in 28:2Δ5,9 and 28:3Δ5,9,19. The significant differences in the profile of these demospongic acids indicate that these nudibranchs consumed different species of sponges. The similarity between the FATMs of J. funebris and its potential prey, the sponge Xestospongia, confirmed their predator–prey relationship. Doriprismatica atromarginata from different sites along the Vietnam coast had different FATM profiles, which showed this nudibranch as having no any strict food specialization and feeding on various Demospongiae species. The abundance of bacterial FATMs in the nudibranchs suggests the importance of bacteria in their diet. Thus, the FATM method has proven to be useful for identifying the feeding specialization and assessing the effect of food availability on the diet of these tropical nudibranch species. [ABSTRACT FROM AUTHOR]

Behavior is predicted to be a primary determinant of the success of the invasion process during the early phases of colonization. Comparing invaders with sympatric native species may provide a good approach to unravel behavioral traits involved in an invasion process. In this study, we carried out an experimental simulation of the introduction and the acclimatization phase into a new environment and assessed the expression of activity, alertness, and habituation in an invasive Mediterranean population of the South African nudibranch Godiva quadricolor comparing its profiles with those of the sympatric Mediterranean native nudibranchs Cratena peregrina and Caloria quatrefagesi. Individuals of these 3 species were subjected to 3 behavioral tests: spontaneous activity, carried out in the introduction phase (immediately after sampling) and after a week of acclimatization; alert test, in which a potential threat was simulated by means of a tactile stimulus, and habituation test, in which the same alert test stimulus was repeated 5 times at 30-min intervals. The invasive G. quadricolor showed higher levels of exploration activity, thigmotaxis, alertness, and sensitization than the native species. These behavioral traits may represent pivotal drivers of the ongoing invasion process. [ABSTRACT FROM AUTHOR]

The precise mechanisms that allow animals and phototrophic organisms to form a stable photosymbiotic relationship are still unknown. While previous studies focused on genomic adaptations of the animal host, more recent research looked into the role of bacteria in photosymbiosis. Here, we analyzed the core microbiome of the sea slug Berghia stephanieae and its food source Exaiptasia diaphana to understand if the microbiome and the linked bacterial metabolic pathways differ between unstable and stable photosymbiosis. This sea slug feeds solely on the model cnidarian E. diaphana and steals their photobionts which the slug can only maintain for a week. We additionally examined the influence of light and starvation stress on the slug's bacterial composition, which are common experimental set-ups to elucidate the photosymbiotic relationship in the slugs. Our results show that the core microbiome of B. stephanieae and E. diaphana differed significantly suggesting that the slug's microbiome is not obtained from its food source or the water column and indicates a vertical transmission. Further, differences in metabolic pathways imply that the microbiome of B. stephanieae does not support a stable photosymbiosis due to an insufficient nitrogen cycle on part of the photobiont. Starving the slugs induced a shift towards an increased abundance of potential pathogens and led to a downregulation in the sulphur cycle. Yet, starvation in darkness resulted in the depletion of most bacteria and induced a metabolic switch toward bacterial nitrogen fixation. This emphasizes that different holobiont members contribute to essential nutrient cycles, and it is important to look beyond the photobiont to understand the sea slug holobiont. [ABSTRACT FROM AUTHOR]

Phylliroe bucephala is a nudibranch notable for having a laterally compressed body and a pelagic lifestyle. Although P. bucephala is widely distributed in tropical and subtropical waters of the Atlantic, Pacific, and Indian Oceans, it has not been recorded in the Colombian Pacific. Here we report the presence of the species in the coastal zone of Nuquí and Pizarro, two localities of Chocó - Colombia, and describe the main characteristics of the specimens collected. [ABSTRACT FROM AUTHOR]

Based on available information on nudibranchs from all published literature, sampling concentrated around the area of Central Norway, and the nudibranch collections at the Museum of Natural History and Archaeology in Trondheim, this study presents the distribution of nudibranch species along the Norwegian coast. All species reported in the literature from Norwegian waters are listed and discussed. A total of 81 species are confirmed being a part of the Norwegian fauna, of which four species (Cuthona rubescens, Polycera faeroensis, Eubranchus vittatus and Onchidoris depressa) are new to Norwegian waters, and two that have previously been mentioned but not documented, Cuthona caerulea and Geitodoris planata, are confirmed found for the first time. Six species, Triopella incisa, Cadlina glabra, Rostanga setidens, Cuthona distans, Cuthona norvegica, Berghia norvegia are considered endemic to Norway, and four species, Doridunculus echinulatus, Doris nobilis, Doto crassicornis, Goniaeolis typica are considered endemic to Scandinavian waters. After the review six species previously reported from Norwegian waters, are considered insufficiently supported, or due to misidentifications (Onchidoris aspersa, Onchidoris oblonga, Onchidoris sparsa, Thecacera virescens, Doto tuberculata and Flabellina browni) and are not longer considered a part of the Norwegian fauna. Sampling has in large been based on SCUBA diving, and proved to be very efficient when sampling in the upper sublittoral in kelp forest habitat.

Baseline data on the distribution of marine species is crucial to be able to address biogeographical patterns and to monitor changes in species occurrences in marine systems. Nudibranch mollusks have proved to be useful bioindicators for monitoring shifts in distribution and have received much attention by the scientific community in recent years. Being positioned in a zoogeographic transition zone between boreal and Arctic regions, northern Norway is an important area for detecting and tracking early distributional shifts. Despite this, no comprehensive knowledge on current biodiversity and distribution of nudibranchs exists from the region. This work presents, for the first time, an annotated and illustrated inventory of nudibranchs in shallow water habitats of the Tromsø region in northern Norway. In total, 49 different nudibranch species or taxa belonging to 19 different families were recorded during the time period May 2020 – December 2023. Compared to occurrence data from literature records and online data sources, 31 species are here reported from the region for the first time. In addition, northern range extensions are presented for a significant part of the Norwegian nudibranch fauna. By documenting current biodiversity and distribution the present study hopes to serve as a baseline for studies focused on monitoring biodiversity in the Arctic region in the future.

Abstract Background How novel phenotypes originate from conserved genes, processes, and tissues remains a major question in biology. Research that sets out to answer this question often focuses on the conserved genes and processes involved, an approach that explicitly excludes the impact of genetic elements that may be classified as clade-specific, even though many of these genes are known to be important for many novel, or clade-restricted, phenotypes. This is especially true for understudied phyla such as mollusks, where limited genomic and functional biology resources for members of this phylum have long hindered assessments of genetic homology and function. To address this gap, we constructed a chromosome-level genome for the gastropod Berghia stephanieae (Valdés, 2005) to investigate the expression of clade-specific genes across both novel and conserved tissue types in this species. Results The final assembled and filtered Berghia genome is comparable to other high-quality mollusk genomes in terms of size (1.05 Gb) and number of predicted genes (24,960 genes) and is highly contiguous. The proportion of upregulated, clade-specific genes varied across tissues, but with no clear trend between the proportion of clade-specific genes and the novelty of the tissue. However, more complex tissue like the brain had the highest total number of upregulated, clade-specific genes, though the ratio of upregulated clade-specific genes to the total number of upregulated genes was low. Conclusions Our results, when combined with previous research on the impact of novel genes on phenotypic evolution, highlight the fact that the complexity of the novel tissue or behavior, the type of novelty, and the developmental timing of evolutionary modifications will all influence how novel and conserved genes interact to generate diversity.

In this paper, a new genus in the nudibranch family Discodorididae, Avaldesia n. gen. is established for Avaldesia albomacula (Chan & Gosliner, 2007) and Avaldesia tahala (Chan & Gosliner, 2007), originally assigned to the genus Thordisa Bergh, 1877, and a new species, Avaldesia tamatoa n. sp. described here from the central Pacific. To establish species relationships within Avaldesia , as well as the placement of Avaldesia within Discodorididae, we utilized four molecular markers (cytochrome c oxidase subunit I, 16S rRNA, histone H3 and 28S rRNA) in our Bayesian inference and maximum likelihood analyses. Four species delimitation methods were complemented by morphological dissections and scanning electron microscopy. Our results reveal a clear separation between Avaldesia and Thordisa and suggest that Avaldesia is more closely related to the genera Hoplodoris Bergh, 1880 and Asteronotus Ehrenberg, 1831. The most characteristic features of Avaldesia include a radula with increasing denticulation towards the fimbriate outermost laterals and a reproductive system with a lobate vestibular gland, occasional hollow vestibular spine and a penis armed with one or more penial spines. All species of Avaldesia are found in shallow water (5–10 m depth) on rocky reefs, sandy sediments and algal fields with distributions across the Indo-Pacific. [ABSTRACT FROM AUTHOR]

Numerous marine invertebrates form symbiotic relationships with single-celled algae, termed "photosymbioses", and the diversity of these interactions is likely underestimated. We examined Phidiana lynceus, a cladobranch sea slug that feeds on photosymbiotic hydrozoans. We assessed its ability to acquire/retain algal symbionts by examining specimens in starvation, finding that P. lynceus is able to incorporate and retain symbionts for up to 20 days. Examining body size during starvation revealed that P. lynceus does not receive enough energy from hosting symbionts to maintain its body mass let alone grow. Intact symbionts were still present in deceased specimens, indicating that P. lynceus does not digest all of its symbionts, even when starving to death. We also examined slug behavior in the field and lab to determine if it seeks light to facilitate photosynthesis, which could provide energetic and oxygenic benefits. In the field, slugs were always observed hiding under stones during the day and they displayed light avoidance in the lab, suggesting this species actively prevents photosynthesis and the benefits it could receive. Lastly, we measured their metabolic rates during the day and night and when treated with and without a photosynthetic inhibitor. Higher metabolic rates at night indicate that this species displays nocturnal tendencies, expending more energy when it emerges at night to forage. Paradoxically, P. lynceus has evolved all of the requisite adaptations to profit from photosymbiosis but it chooses to live in the dark instead, calling into question the nature of this symbiosis and what each partner might receive from their interaction. [ABSTRACT FROM AUTHOR]

Time calibrated phylogenies are typically reconstructed with fossil information but for soft‐bodied marine invertebrates that lack hard parts, a fossil record is lacking. In these cases, biogeographic calibrations or the rates of divergence for related taxa are often used. Although nudibranch phylogenies have advanced with the input of molecular data, no study has derived a divergence rate for this diverse group of invertebrates. Here, we use an updated closure date for the Isthmus of Panama (2.8 Ma) to derive the first divergence rates for chromodorid nudibranchs using multigene data from a geminate pair with broad phylogeographic sampling. Examining the species Chromolaichma sedna (Marcus & Marcus, 1967), we uncover deep divergences among eastern Pacific and western Atlantic clades and we erect a new species designation for the latter (Chromolaichma hemera sp. nov.). Next, we discover extensive phylogeographic structure within C. hemera sp. nov. sensu lato, thereby refuting the hypothesis of a recent introduction. Lastly, we derive divergence rates for mitochondrial and nuclear loci that exceed known rates for other gastropods and we highlight significant rate heterogeneity both among markers and taxa. Together, these findings improve understanding of nudibranch systematics and provide rates useful to apply to divergence scenarios in this diverse group. [ABSTRACT FROM AUTHOR]

Some cladobranch sea slugs host algae (Symbiodiniaceae), forming stable or unstable photosymbiotic relationships. Although some benefits from retaining symbionts have been described in stable photosymbioses, unstable photosymbioses remain largely uninvestigated. We examined two potential benefits – nutrition and oxygen produced via photosynthesis – in the unstable cladobranch model species, Berghia stephanieae. To investigate potential nutritive benefits, we conducted transmission electron microscopy and observed both partially digested symbionts and lipid droplets, indicating that B. stephanieae benefits energetically from hosting zooxanthellae through digestion. Since increased temperatures can cause oxygen limitation, any oxygenic benefits B. stephanieae receives from photosynthesis could influence their thermal tolerance, allowing photosynthetic slugs to withstand higher temperatures than specimens where photosynthesis is limited or absent. To assess this, we measured the maximum temperature they can withstand before succumbing to heat-shock under three light intensities (0, 100 and 700 µmol m-2s-1). Oxygen uptake was measured before and after heat-shock to determine whether uptake was affected by thermal stress. Slugs exposed to high light displayed significantly lower thermal limits than those at zero or moderate light, indicating exposure to acute high light negatively impacts thermal tolerance. Lastly, we assessed if and how light affects juvenile development and survival. Juveniles exposed to moderate light survived longest, while both other light intensities reduced survival. These investigations demonstrate that unstable photosymbiosis provides B. stephanieae with nutritive benefits during different ontogenetic stages. Oxygenic benefits are less clear, as slugs exposed to thermal stress in dark and under moderate light did not display different thermal tolerances. [ABSTRACT FROM AUTHOR]

This study reports our observation of the large sea slug Tethys fimbria Linnaeus, 1767 in the northern-eastern Sea of Marmara (the Princes’ Islands). We observed T. fimbria on the detrital bottom of the sea at a depth of 35 m in June 2022. This species had previously been reported during spawning in a recent study conducted in the southern part of the Çanakkale Strait (the Dardanelles Strait that connects the Marmara Sea with the Aegean Sea). Prior to 2022 there had been no reports of this conspicuous species from the Marmara Sea in the scientific literature or in photo-records among divers. Following our observation of the species in the sea around the Princes’ Islands, underwater photographers reported pictures of T. fimbria from different locations in the Marmara Sea on social media platforms. The sea slug seems to extend its distribution northwards. The potentially new arrival of the large sea slug in the Sea of Marmara, rather than a distribution shift from deoxygenated deep Marmara basins or a climate-related northwards expansion, is discussed.

Abstract Time calibrated phylogenies are typically reconstructed with fossil information but for soft‐bodied marine invertebrates that lack hard parts, a fossil record is lacking. In these cases, biogeographic calibrations or the rates of divergence for related taxa are often used. Although nudibranch phylogenies have advanced with the input of molecular data, no study has derived a divergence rate for this diverse group of invertebrates. Here, we use an updated closure date for the Isthmus of Panama (2.8 Ma) to derive the first divergence rates for chromodorid nudibranchs using multigene data from a geminate pair with broad phylogeographic sampling. Examining the species Chromolaichma sedna (Marcus & Marcus, 1967), we uncover deep divergences among eastern Pacific and western Atlantic clades and we erect a new species designation for the latter (Chromolaichma hemera sp. nov.). Next, we discover extensive phylogeographic structure within C. hemera sp. nov. sensu lato, thereby refuting the hypothesis of a recent introduction. Lastly, we derive divergence rates for mitochondrial and nuclear loci that exceed known rates for other gastropods and we highlight significant rate heterogeneity both among markers and taxa. Together, these findings improve understanding of nudibranch systematics and provide rates useful to apply to divergence scenarios in this diverse group.

Goniodoridella Pruvot-Fol, 1933 is a genus of small nudibranchs found in the Indo-Pacific Ocean. Currently, the genus includes only two described species, the widely distributed type species Goniodoridella savignyi Pruvot-Fol, 1933 and G. borealis Martynov, Sanamyan & Korshunova, 2015, which is found in the northern Sea of Japan. However, because of the presence of a group of cryptic species, the known geographic range of G. savignyi may have been overestimated, while the species richness of the genus may be underestimated. In the current study, we examined specimens from Australia, the Philippines and Russia that were identified as G. savignyi, G. borealis and an undescribed species. Detailed analyses of the external morphology and internal anatomy of the specimens were carried out, as well as scanning electron micrography of the radula and the labial cuticle. Photographs of the penial spines were taken under a light microscope. DNA sequence data for selected mitochondrial and nuclear markers were obtained, allowing the inclusion of the genus Goniodoridella in molecular phylogenetic analyses for the first time. Our results support the monophyly of the genus Goniodoridella and confirm the existence of a species complex of which the type is G. savignyi. The new species G. geminae n. sp. G. serrata n. sp. and G. unidonta n. sp. are described. [ABSTRACT FROM AUTHOR]

Color ontogeny and variations associated with discrete morphological differences may generate taxonomical challenges, which requires multiple data types and in-depth historical review. The nudibranch known as the Spanish dancer, Hexabranchus sanguineus, is a classic example with over 200 years of taxonomic confusion. Currently, H. sanguineus is accepted by most authors as a single species from the Indo-Pacific Ocean with Hexabranchus morsomus as a valid species from the Atlantic Ocean. Yet, despite these species being highly studied, their systematic status remains debatable. Over 30 synonyms have been proposed for H. sanguineus and even a distinct genus for H. morsomus. Here we provide, for the first time, a comprehensive review of all proposed names and an integrative taxonomic revision of the genus including morphological and molecular data. Our results reveal that H. sanguineus is a complex of five species: four previously described and an undescribed species, one of the largest nudibranchs in the world: Hexabranchus giganteus sp. nov. The genus Caribranchus is considered a junior synonym of Hexabranchus Ehrenberg, 1828 and the ontogeny of color pattern is discussed. [ABSTRACT FROM AUTHOR]

We describe the first recorded association between fishes and nudibranchs in epipelagic waters. In situ observations and photographs of a juvenile spotted driftfish Ariomma regulus (Stromateiformes; Ariommatidae) swimming alongside the planktonic nudibranch Phylliroe lichtensteinii (Gastropoda; Phylliroidae) were made during blackwater scuba dives off Palm Beach, Florida, United States of America. In this paper, we describe this behavior, highlighting a previously undocumented zooplanktonic host used by fishes. This finding also demonstrates the importance of community science in advancing our understanding of the early life history of marine species. [ABSTRACT FROM AUTHOR]

This study reports our observation of the large sea slug Tethys fimbria Linnaeus, 1767 in the northern-eastern Sea of Marmara (the Princes' Islands). We observed T. fimbria on the detrital bottom of the sea at a depth of 35 m in June 2022. This species had previously been reported during spawning in a recent study conducted in the southern part of the Çanakkale Strait (the Dardanelles Strait that connects the Marmara Sea with the Aegean Sea). Prior to 2022 there had been no reports of this conspicuous species from the Marmara Sea in the scientific literature or in photo-records among divers. Following our observation of the species in the sea around the Princes' Islands, underwater photographers reported pictures of T. fimbria from different locations in the Marmara Sea on social media platforms. The sea slug seems to extend its distribution northwards. The potentially new arrival of the large sea slug in the Sea of Marmara, rather than a distribution shift from deoxygenated deep Marmara basins or a climate-related northwards expansion, is discussed. [ABSTRACT FROM AUTHOR]

Feeding-choice experiments were conducted under laboratory conditions with two dorid spongivorous nudibranchs, Goniobranchus aureomarginatus and Ceratosoma amoenum, collected from a sponge meadow off Tauranga, New Zealand with two sponge prey (Dysidea teawanui sp.nov. and an undescribed species from the Dictyodendrillidae family, possibly Dictyodendrilla tenella (Lendenfeld 1888). The first choice of prey, the total number of prey choices made, and the time spent on each prey target was recorded, results indicating that each nudibranch had strong preferences for specific prey species. Preferences were significant when the time spent grazing on prey was taken into consideration. Goniobranchus aureomarginatus had a strong preference for the undescribed Dictyodendrillid sponge, while Ceratosoma ameonum preferred Dysidea teawanui. The results of the feeding-choice experiments matched observations in the wild. Chemical analysis of the undescribed Dictyodendrillid sponge led to the isolation and characterisation of six known bioactive metabolites, dictyodendrin C (1), D (2) and F (3), as well as denigrin E (4), dactylpyrrole A (5) and lamellarin O1 (6). Two of the known compounds, dictyodendrins C (1) and F (3) were also isolated from G. aureomarginatus individuals. Chemical analysis of D. teawanui afforded ergosterol peroxide, 5α,8α-epidioxy-24-methylcholesta-6,22-dien-3β-ol (7). The structures of the isolated natural products were elucidated based on extensive analysis of 1D and 2D NMR data. [ABSTRACT FROM AUTHOR]

The phylogeny of the family Tritoniidae has recently been studied with significant advances, but the relationships between genera are still controversial. In our study, we investigated the phylogeny of Tritoniidae using the most diverse taxon sampling possible. We applied an integrative approach based on new sequences of two mitochondrial genes (COI and 16S), a nuclear gene (H3) and morpho-anatomical characters. The monophyly of the family Tritoniidae was not recovered in our phylogenetic analyses. In view of our results, we propose a new rearrangement at the subfamily and genus levels. The plate-bearing genera are raised to the subfamily level as the monophyletic Marioniinae subfam. nov. , formed by Marionia and the reinstated Marioniopsis. The remaining plate-less genera are raised to the subfamily level as the monophyletic Tritoniinae Lamarck, 1809. The genus Myrella is reinstated to assign the Antarctic and sub-Antarctic tritoniids. The taxonomic status of the monotypic Tritonidoxa is confirmed. Species delimitation analyses reveal a new large Marionia species from the Gulf of Cádiz (south-west Spain, Atlantic Ocean) and evidence for the pseudocryptic speciation of numerous Atlantic–Mediterranean and Indo-Pacific tritoniids. Finally, taxonomic notes are provided for several species according to the proposed rearrangement. [ABSTRACT FROM AUTHOR]

Nudibranchs, as a group, have received limited attention in terms of scientific study along the coastline of Peru. Here, an updated and comprehensive list of nudibranch species found in the Peruvian sea is presented, compiled through an extensive review of relevant literature. This compilation encompasses a total of 31 species, classified into two suborders, 10 superfamilies, 20 families, and 28 genera. With respect to the biogeographic provinces along the Peruvian coast, 23 species inhabit the Warm Temperate Southeastern Pacific province, 18 species occur in the Tropical Eastern Pacific province, and 10 species are found in both provinces, crossing the transitional zone between them. In terms of distribution patterns, two species exhibit a cosmopolitan distribution (Glaucus atlanticus and Fiona pinnata), while two species display a circumtropical distribution (Cephalopyge trematoides and Phylliroe bucephala). One species exhibits a bipolar distribution in the Eastern Pacific and possesses an amphi-South American distribution (Rostanga pulchra). Additionally, six species exhibit an amphi-South American distribution (Rostanga pulchra, Diaulula punctuolata, Doto uva, Tyrinna evelinae, Tyrinna delicata, and Doris fontainii), and two species are endemic to Peru (Corambe mancorensis and Felimare sechurana). This study provides comprehensive information on biogeographical aspects, geographical distributions, and taxonomic updates within the nudibranch species documented in Peru. Furthermore, we discuss the status of species listed in previous literature that have not been confirmed by collections, referring to them as potentially occurring species. [ABSTRACT FROM AUTHOR]

Spurilla braziliana MacFarland 1909 is a morphologically diverse nudibranch found in the Pacific and Western Atlantic. The complete mitochondrial genome of S. braziliana has been constructed using next-generation sequencing technology. The mitochondrial genome is 14,291 bp and contains 13 protein-coding genes, 2 rRNA genes, and 23 tRNA genes. Molecular phylogenetic analysis using the maximum likelihood method revealed that S. braziliana is included in the superfamily Aeolidioidea and forms a monophyletic group with Berghia stephanieae, a nudibranch of the family Aeolidiidae. This study reinforces existing taxonomic insights and provides a basis for further molecular phylogenetic analysis. [ABSTRACT FROM AUTHOR]

A peculiar eolid nudibranch showing an unknown chromatic array was found in a rocky bottom of Santa Maria al Bagno, in the Salento peninsula, Ionian Sea (Central Mediterranean Sea). This specimen, initially identified as Piseinotecus sp., was observed in situ and photographed while feeding and laying eggs close to individuals belonging to the Mediterranean Piseinotecus soussi. To assess the identity of this unexpected Piseinotecus ‘white morph’, a DNA identification approach was carried out using mitochondrial cytochrome coxidase subunit I (COI), as it is the molecular marker mostly used to distinguish nudibranchs species. The molecular analysis unambiguously identified this specimen as Piseinotecus soussi and helped to shed lights on the striking intraspecific colour variability characterizing this rare species. [ABSTRACT FROM AUTHOR]

Abstract By applying morphological and molecular data on two genera of the nudibranch molluscs it is shown that the tension between taxonomic practice and evolutionary processes persists. A review of the related genera Catriona and Tenellia is used to demonstrate that the fine‐scale taxonomic differentiation is an important tool in the integration of morphological and molecular data. This is highlighted by the hidden species problem and provides strong argument that the genus must be kept as a maximally narrowly‐defined entity. Otherwise, we are forced to compare a highly disparate species under the putatively lumped name “Tenellia”. We demonstrate this in the present study by applying a suite of delimitation methods and describing a new species of Tenellia from the Baltic Sea. The new species possesses fine‐scale morphological distinguishing features, which were not investigated before. The true, narrowly defined genus Tenellia represents a peculiar taxon with a clearly expressed paedomorphic characters and predominantly brackish‐water habitats. The phylogenetically related genus Catriona, of which three new species are described here, clearly demonstrates different features. A lumping decision to call many morphologically and evolutionary different taxa as “Tenellia” will downgrade the taxonomic and phylogenetic resolution of the entire family Trinchesiidae to just a single genus. The dissolution of the dilemma of “lumpers & splitters”, which still significantly affects taxonomy, will further help to make systematics a true evolutionary discipline.

The occurrence, relative abundance and bathymetric distribution of the deep Mediterranean heterobranch fauna were evaluated as a result of an extensive visual census down to 1825 m depth, carried out along the western Italian coasts, covering a latitudinal range of about 600 nautical miles. Observations were conducted using Remotely Operated Vehicles (ROVs) in 551 sites, focusing on the deepest part of the continental shelf, the shelf edge and the upper bathyal zone. The analysis of over 508 hours of video footage and more than 27,000 high-resolution photographs allowed to explore about 594,000 m2 of rocky outcrops and nearby soft seafloors in four main coastal areas (Ligurian Sea, north-central Tyrrhenian Sea, southern Tyrrhenian Sea, and Sicily Channel) and twelve offshore seamounts. Thirty-six species of heterobranchs, for a total of 559 records, were identified. Sixteen were only sporadically spotted (

Species of Kaloplocamus Bergh, 1880 are enigmatic Nudibranchia sea slugs, and only two valid species are reported in the northwestern Pacific. Kaloplocamus japonicus (Bergh, 1880) was initially described based on alcohol-fixed specimens. In the latest revision of Kaloplocamus, it was synonymized with Kaloplocamus ramosus (Cantraine, 1835). Recently, several nudibranchs were collected from Tianheng, Shandong Province, China, and one of them is identified as an undescribed species described here as Kaloplocamus albopunctatus sp. nov. based on integrated approaches incorporating morphological observations, internal anatomy, and phylogenetic analyses of two mitochondrial (COI, 16S rRNA) genes. The other species is identified as K. japonicus Bergh, 1880 based on the anatomy of the reproductive system. The new species K. albopunctatus sp. nov. is similar to K. ramosus in having a bright orange-red color pattern but differs significantly in the structure of appendages and reproductive system. Kaloplocamus japonicus can be easily distinguished from other Kaloplocamus species by its translucent, white-pink coloration and unique features of the female reproductive organ. Both species are supported as distinct species in all molecular analyses. The phylogenetic analyses propose a new estimate of the relationship between Kaloplocamus and Plocamopherus, and the evolution of bioluminescence within Triophinae is discussed. Our results also suggest cryptic biodiversity within the K. ramosus species complex. [ABSTRACT FROM AUTHOR]

Background: Nudibranchs comprise a group of > 6000 marine soft-bodied mollusk species known to use secondary metabolites (natural products) for chemical defense. The full diversity of these metabolites and whether symbiotic microbes are responsible for their synthesis remains unexplored. Another issue in searching for undiscovered natural products is that computational analysis of genomes of uncultured microbes can result in detection of novel biosynthetic gene clusters; however, their in vivo functionality is not guaranteed which limits further exploration of their pharmaceutical or industrial potential. To overcome these challenges, we used a fluorescent pantetheine probe, which produces a fluorescent CoA-analog employed in biosynthesis of secondary metabolites, to label and capture bacterial symbionts actively producing these compounds in the mantle of the nudibranch Doriopsilla fulva. Results: We recovered the genome of Candidatus Doriopsillibacter californiensis from the Ca. Tethybacterales order, an uncultured lineage of sponge symbionts not found in nudibranchs previously. It forms part of the core skin microbiome of D. fulva and is nearly absent in its internal organs. We showed that crude extracts of D. fulva contained secondary metabolites that were consistent with the presence of a beta-lactone encoded in Ca. D. californiensis genome. Beta-lactones represent an underexplored group of secondary metabolites with pharmaceutical potential that have not been reported in nudibranchs previously. Conclusions: Altogether, this study shows how probe-based, targeted sorting approaches can capture bacterial symbionts producing secondary metabolites in vivo. 8entVVL2Hhkfc-ejj4sDuQ Video Abstract [ABSTRACT FROM AUTHOR]

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In this paper six heterobranch mollusc species are reported for the first time for Bosnia and Herzegovina: Berthellina edwardsi (Vayssiere, 1896), Felimida luteorosea (Rapp, 1827), Thuridilla hopei (Verany, 1853), Dendrodoris grandiflora (Rapp, 1827), Camachoaglaja africana (Pruvot-Fol, 1953) and Felimare villafranca (Risso, 1818). The study was conducted in October 2021 on Klek Peninsula and in Neum Bay (eastern Adriatic Sea, Bosnia and Herzegovina). This paper significantly extends the knowledge of the national marine heterobranch molluscs fauna, almost doubling the number of species known for the country, as only seven heterobranch species were reported for Bosnia and Herzegovina until now. [ABSTRACT FROM AUTHOR]

The current study presents the first molecular data of three species of the family Phyllidiidae,Phyllidia ocellata, Phyllidia alyta and Phyllidiella rosans, from Indian waters. The P. ocellata molecular sequences closely match those available from the Pacific Ocean, whereas P. alyta and P. rosans form independent clades, confirming their identifications as distinct species. Phyllidia ocellata, frequently found in the Indo-Pacific tropical coral reefs, is renowned for its wide range of colours and external forms. Numerous variations have been found and are being examined at the molecular level, and the subject of this study is another variation that, until dissection and molecular analysis, was thought to be a colour form of Phyllidia multituberculata. Although India has a long history of heterobranch research, no phyllidiid species from Indian waters have ever been the subject of molecular research. [ABSTRACT FROM AUTHOR]

One new species of the genus Dendronotus (Nudibranchia: Dendronotidae) is described from Norway and Northern Ireland, as well as from the adjacent North Sea, and one new subspecies of Dendronotus arcticus is described from Norway by applying a combination of fine-scale morphological and molecular phylogenetic data. The present case demonstrates multilevel morphological and molecular similarities and differences considering on the one hand a grouping of three similar looking sympatric taxa (D. yrjargul, D. arcticus gartensis n. subsp. and D. keatleyae n. sp.), and on the other hand two different looking apparently allopatric subspecies (D. arcticus arcticus and D. arcticus gartensis n. subsp.). The type species of the genus, D. frondosus, which is the commonest dendronotid in Norway and the United Kingdom, consistently demonstrates substantial molecular and fine-scale morphological differences from D. keatleyae n. sp. The present study, apart from providing purely taxonomic information, also provides new data for a broad discussion of global biodiversity patterns. [ABSTRACT FROM AUTHOR]

Nudibranchs have a mostly carnivorous diet, and they prey on a wide variety of other animal taxa. Many species, mainly belonging to the Cladobranchia suborder, feed on cnidarians, including member of the class Hydrozoa. Several hydrozoan species display a symbiotic lifestyle, being associated with other benthic invertebrates, including for instance bryozoans, corals, octocorals, and sponges. In our knowledge, no record of nudibranch predation on symbiotic hydrozoans has been reported so far, possibly thanks to the protective action by the host towards its symbiotic hydrozoan. Here, we show the unexpected case of a nudibranch belonging to the recently described species Sakuraeolis marhe (Fernández-Simón and Moles, 2023) feeding on Zanclea sp. 2, a hydrozoan associated with the cheilostome bryozoan Celleporaria sp. This trophic association is confirmed by the presence and storage of the nematocysts into the nudibranch cnidosacs. Moreover, the nudibranch appears to selectively store mostly a single type of nematocyst, that is large size stenotele. The observation here reported represents the first well-documented record of a nudibranch feeding on a symbiotic hydrozoan and the first confirmed case of predation on Zanclea polyps. Moreover, we provide additional genetic information and the first description of the internal anatomy of S. marhe. [ABSTRACT FROM AUTHOR]

The study of a well-preserved collection of discodorid nudibranchs collected in Koumac, New Caledonia, revealed the presence of seven species new to science belonging to the genera Atagema, Jorunna, Rostanga, and Sclerodoris, although some of the generic assignments are tentative as the phylogeny of Discodorididae remains unresolved. Moreover, a poorly known species of Atagema originally described from New Caledonia is re-described and the presence of Sclerodoris tuberculata in New Caledonia is confirmed with molecular data. All the species described herein are highly cryptic on their food source and in the context of the present study the term "cryptic" is used to denote such species. This paper highlights the importance of comprehensive collecting efforts to identify and document well-camouflaged taxa. [ABSTRACT FROM AUTHOR]

The present study was carried out along the coasts of the Island of Pantelleria (Italy, Mediterranean Sea), a volcanic island located at the centre of the Sicily Channel. The aim was to provide the first faunistic list of the marine heterobranchs at the Pantelleria Island. Through both scuba dives and snorkelling/apnoea activities, 33 species were found: two species of the Pleurobranchida, 23 of the Nudibranchia, one of the Umbraculida, two of the Aplysiida and five of the Sacoglossa. Among these, the findings of Felimida elegantula, Okenia picoensis and Polybranchia sp. are discussed due to the particular interest at them. The present list represents the baseline information in the study of the marine Heterobranchia fauna of the Pantelleria Island and contributes to characterising it as a hotspot of the marine biodiversity. [ABSTRACT FROM AUTHOR]

Nudibranchs have turned into highly popular marine creatures in the scuba diving world. With the aim to protect and conserve the environment, the illustration method is used as the medium because, as a visual artifact, it has quite reliable, and its broad visual communication capabilities allow for different expressions. The result is, by establishing Nudibranchs as cultural objects, the popularity of Nudibranchs can reach the wider society to greatly impact the marine conservation efforts. [ABSTRACT FROM AUTHOR]

By applying morphological and molecular data on two genera of the nudibranch molluscs it is shown that the tension between taxonomic practice and evolutionary processes persists. A review of the related genera Catriona and Tenellia is used to demonstrate that the fine‐scale taxonomic differentiation is an important tool in the integration of morphological and molecular data. This is highlighted by the hidden species problem and provides strong argument that the genus must be kept as a maximally narrowly‐defined entity. Otherwise, we are forced to compare a highly disparate species under the putatively lumped name "Tenellia". We demonstrate this in the present study by applying a suite of delimitation methods and describing a new species of Tenellia from the Baltic Sea. The new species possesses fine‐scale morphological distinguishing features, which were not investigated before. The true, narrowly defined genus Tenellia represents a peculiar taxon with a clearly expressed paedomorphic characters and predominantly brackish‐water habitats. The phylogenetically related genus Catriona, of which three new species are described here, clearly demonstrates different features. A lumping decision to call many morphologically and evolutionary different taxa as "Tenellia" will downgrade the taxonomic and phylogenetic resolution of the entire family Trinchesiidae to just a single genus. The dissolution of the dilemma of "lumpers & splitters", which still significantly affects taxonomy, will further help to make systematics a true evolutionary discipline. [ABSTRACT FROM AUTHOR]

Five Chromodoris species from North Sulawesi, Indonesia, were investigated for their sequestration of marine natural products. The cytotoxic 2-thiazolidinone macrolide latrunculin A (LatA) was the major metabolite in all examined Chromodoris species, as well as in one of the associated sponges Cacospongia mycofijiensis (Kakou, Crews & Bakus, 1987), supporting a dietary origin of LatA. Furthermore, LatA was secreted with the mucus trail, suggesting a possible use in short-range chemical communication. MALDI MS-Imaging revealed an accumulation of LatA throughout the mantle tissue, mucus glands, and especially in vacuoles of the mantle dermal formations (MDFs). Cytotoxicity of the isolated LatA was tested in HEK-293 cells, confirming that LatA targets the actin cytoskeleton. In vivo toxicity experiments with the sacoglossan Elysia viridis (Montagu, 1804) showed 100% mortality, but 100% survival of Chromodoris specimens, demonstrating resistance to LatA. A novel actin isoform was detected in all investigated Chromodoris species with two amino acid substitutions at the 'nucleotide binding' cleft, the binding site of LatA. These are suggested to cause insensitivity against LatA, thus enabling the storage of the toxin within the body for the slugs' own defense. [ABSTRACT FROM AUTHOR]