Mechanisms of wet adhesion have evolved in several aquatic organisms over millions of years. Yet, the repertoire of synthetic biocompatible wet adhesive materials is still limited. The byssus is a well-studied proteinaceous bioadhesive structure utilized by several bivalves to support sessile lifestyles in turbulent conditions. The quagga mussel (Dreissena bugensis) is a freshwater byssate and a notorious invasive species in the Great Lakes region. To identify adhesive proteins in the quagga mussel byssus, we utilized quantitative proteomics and found several proteins enriched at the byssus-substrate interface. Among the identified proteins was the Dbfp7 protein family. Dbfp7 is a small, polymorphic, and mostly disordered protein that lacks significant amounts of 3,4-dihydroxyphenylalanine (DOPA), a modified amino acid found in several marine mussel byssal proteins. Atomic force microscopy nanomechanical mapping of Dbfp7 films demonstrates that this protein exhibits adhesive ability in aqueous conditions. While DOPA is critical for marine mussel adhesion, interfacial electrochemistry of freshwater adhesive plaques suggests that freshwater byssates circumvent catechol-based adhesion. The functional characterization of Dbfp7 as a freshwater mussel adhesive protein advances the understanding of fundamental requirements for biocompatible wet adhesion, a crucial step for the development of bioinspired wet adhesive materials, such as improved medical adhesives.

Mechanisms of wet adhesion have been developed by several aquatic organisms over millions of years of evolutionary processes. Yet, the repertoire of synthetic biocompatible wet adhesive materials is still limited. In most marine bioadhesive proteins, 3,4–dihydroxyphenylalanine (DOPA) plays a significant role in strong interfacial interactions. The bioadhesive proteins in freshwater organisms are less well understood. The quagga mussel ( Dreissena bugensis ) is a notorious freshwater invasive species in the Great Lakes that attaches to a plethora of surfaces via a byssus. To determine the adhesive proteins in the quagga mussel byssus, we utilized quantitative proteomics to identify the proteins enriched at the byssus-substrate interface. Among the identified proteins was the Dbfp7 protein family. Dbfp7 is a small, polymorphic, and mostly disordered protein that lacks significant amounts of DOPA. Atomic force microscopy measurements of Dbfp7 confirm that this protein has similar adhesion energy to marine mussel adhesive proteins in aqueous conditions despite lacking DOPA. These results suggest that freshwater mussels may employ different mechanisms of adhesion compared to marine byssates. The inclusion of Dbfp7 to the library of known wet bioadhesive proteins — the first functionally characterized freshwater bioadhesive protein to our knowledge — will allow for a better understanding of the fundamental properties required to achieve biocompatible wet adhesion, a crucial step for the development of bio-inspired wet adhesive materials, such as improved medical adhesives. ### Competing Interest Statement The authors have declared no competing interest.

A solitary Anelasma squalicola specimen was collected from the cloaca of a Greenland shark (Somniosus microcephalus), the first time this association has been recorded. The specimen's identity was confirmed through morphological and genetic assessment (mitochondrial markers: COI and control region). A. squalicola is a species typically associated with deep-sea lantern sharks (Etmopteridae) and, until the present observation, had never been observed at a sexually mature size in the absence of a mating partner. Given the reported negative effects of this parasite on its hosts, monitoring Greenland sharks for additional cases is recommended.

Barnacles (Cirripedia) are almost exclusively a marine taxon. Within two of the three suborders that constitute the Cirripedia, i.e., Thoracica (the sessile and pedunculated barnacles) and Acrothoracica (the burrowing barnacles), no truly freshwater-dwelling species has ever been reported. In the third suborder, Rhizocephala (parasitic barnacles), four species are known to thrive in semiterrestrial, brackish waters, or fully freshwater habitats, as parasites of crabs from the corresponding habitats. In this chapter, we present molecular data that indicate a single marine-to-freshwater transition event in a lineage that is either part of the genus Heterosaccus or closely related to it. Morphological characters of the settling larval stage, the cypris, further support this evolutionary scenario.

Molecular and morphological methods are used to describe the rhizocephalan Lernaeodiscus kasyanovi sp. nov. from Russian waters of the Sea of Japan, the second of two Lernaeodiscus species parasitizing the porcellanid crab Pachycheles stevensii Stimpson, 1858. Lernaeodiscus kasyanovi sp. nov. differs from the other species found on this host, Lernaeodiscus rybakovi Korn et al., 2020a, by molecular markers, by a smaller size, a lighter color, by the shape of receptacles, by the presence of marginal lobes in mature specimens, and by the retinacula type on the internal cuticle. Lernaeodiscus kasyanovi sp. nov. is the sister taxon to Lernaeodiscus porcellanae in the monophyletic genus Lernaeodiscus. Lernaeodiscus kasyanovi is rather rare compared to L. rybakovi, their prevalence on the porcellanid crab P. stevensii does not exceed 2%. It is the second example of two rhizocephalan species infesting the same brachyuran species in Peter the Great Bay.

Lithistid sponges are globally distributed in temperate and sub-tropical areas, constituting an important component of deep-sea benthic communities where they form structurally complex and vulnerable marine ecosystems (VMEs). In this study, we assess the diversity and investigate the spatial and bathymetric distribution of the lithistid sponges of the Azores archipelago (North Atlantic) based on historical records and examination of samples accidentally collected during deep-sea longline fishing operations in the region. Eleven lithistid species are recognized to occur in the Azores, including Leiodermatium tuba , recently described from material collected in several Northeast Atlantic seamounts that is hereby reported for the first time to the archipelago. We provide molecular barcodes (mtDNA COI and rRNA 28S) for seven of these species, including Discodermia ramifera , Macandrewia azorica , and Exsuperantia archipelagus , for which the Azores constitutes the type locality. We further discuss the phylogenetic and biogeographic affinities of the Azorean lithistids in the context of the Porifera classification, and the wider Northeast Atlantic upper bathyal fauna. Our study also warrants the addition of some lithistid species to the list of VME indicators for the Northeast Atlantic in support of the sustainable management and conservation of these species and habitats, as well as the ecological functions they deliver.

Molecular and morphological methods are used to describe Lernaeodiscus rybakovi, a new rhizocephalan species parasitizing the porcellanid crab Pachycheles stevensii Stimpson, 1858, collected in Russian waters of the Sea of Japan. Molecular analysis of three species, including the new one, confirms the monophyly of the genus Lernaeodicus Muller, 1862 and its recent transfer to the family Peltogastridae. The main morphological features of the new species are also common with characters of the other species of the genus Lernaeodiscus Muller, 1862. Externa of L. rybakovi differs from the well studied Lernaeodiscus porcellanae from the E. Pacific by molecular markers, color and the absence of pronounced marginal lobes. Retinacula on the internal cuticle of L. rybakovi are found in the genus Lernaeodiscus for the first time. Some of the female hosts with adult externae were unusual in also carrying their own eggs on the pleopods, a rare situation among rhizocephalans. The complete larval development in the genus Lernaeodiscus is described here for the first time and includes five naupliar and one cypris instar. The main morphological features of Lernaeodiscus nauplii (the presence of flotation collar, morphology of the frontolateral horns and furcal spines, and the arrangement of dorsal setae on the shield head) are common with those of other known peltogastrid larvae, but also resemble nauplii of Peltogasterella in the presence of naupliar eyes and thin structure of the flotation collar. The sizes of male and female cyprids of L. rybakovi overlap slightly. In summer months, larval sex ratio is male-biased. We briefly review important larval characters in the Rhizocephala. (c) 2020 Elsevier GmbH. All rights reserved.

Fishes in the mesopelagic zone (200–1000 m) have recently been highlighted for potential exploitation. Here we assess global phylogeography in Maurolicus , the Pearlsides, an ecologically important group. We obtained new sequences from mitochondrial COI and nuclear ITS-2 from multiple locations worldwide, representing 10 described species plus an unknown central South Pacific taxon. Phylogenetic analyses identified five geographically distinct groupings, three of which comprise multiple described species. Species delimitation analyses suggest these may represent four species. Maurolicus muelleri and M. australis are potentially a single species, although as no shared haplotypes are found between the two disjunct groups, we suggest maintenance of these as two species. Maurolicus australis is a predominantly southern hemisphere species found in the Pacific, Indian and southern South Atlantic Oceans, comprising five previously allopatric species. M. muelleri (previously two species) is distributed in the North Atlantic and Mediterranean Sea. Maurolicus weitzmani (previously two species) inhabits the eastern equatorial Atlantic, Gulf of Mexico and western North and South Atlantic. Maurolicus mucronatus is restricted to the Red Sea. No Maurolicus have previously been reported in the central South Pacific but we have identified a distinct lineage from this region, which forms a sister group to Maurolicus from the Red Sea.

Rhizocephalans are abundant members of marine ecosystems and are important regulators of crustacean host populations. Morphological and ecological variation makes them an attractive system for evolutionary studies of advanced parasitism. Such studies have been impeded by a largely formalistic taxonomy, because rhizocephalan morphology offers no characters for a robust phylogenetic analysis. We use DNA sequence data to estimate a new phylogeny for 43 species and use this to develop a revised taxonomy for all Rhizocephala. Our taxonomy accepts 13 new or redefined monophyletic families. The traditional subdivision into the suborders Kentrogonida and Akentrogonida is abandoned, because both are polyphyletic. The three ‘classical’ kentrogonid families are also polyphyletic, including the species-rich Sacculinidae, which is split into a redefined and a new family. Most species of large families remain to be studied based on molecular evidence and are therefore still assigned to their current genus and family by default. We caution against undue generalizations from studies on model species until a more stable species-level taxonomy is also available, which requires more extensive genus- and species-level sampling with molecular tools. We briefly discuss the most promising future studies that will be facilitated by this new phylogeny-based taxonomy.

Haminoeidae is the most diverse family of Cephalaspidea with 13 to 17 genera commonly recognised as valid and with 46 genera that historically have been moved back and forth between Haminoeidae and other families. Due to poor definition of most genera the family is plagued by extensive taxonomic confusion and its generic composition and internal relationships remain uncertain. In this work we have integrated the study of type material, original descriptions, shells, morpho-anatomical data, and molecular phylogenetics (Bayesian, maximum likelihood, and maximum parsimony) based on five genetic markers (the mitochondrial genes cytochrome c oxidase subunit I and 16SrRNA and the nuclear genes 18SrRNA, 28SrRNA, and histoneH3) to delimit the valid genera, define synapomorphic traits, and establish synonym lists. Three hundred and ninety novel sequences were generated. In total 14 genera were recognised; one genus (Vellicolla gen. nov.) is here described as new and an additional fifteenth group was identified, but no species could be formally ascribed to it and therefore remains unnamed (here designated informally as mini-haminoeids). The relationships of genera are discussed and seven deep clades have been identified but are not formally named because of lack of recognisable synapomorphies for several of them. A new classification for Haminoeidae is proposed including 14 valid genera and one informal group.

The European freshwater mollusk Dreissena bugensis (quagga mussel), an invasive species to North America, adheres to surfaces underwater via the byssus: a non-living protein ‘anchor’. In spite of its importance as a biofouling species, the sequence of the majority of byssal proteins responsible for adhesion are not known, and little genomic data is available. To determine protein sequence information, we utilized next-generation RNA sequencing and de novo assembly to construct a cDNA library of the quagga mussel foot transcriptome, which contains over 200,000 transcripts. Quagga mussel byssal proteins were extracted from freshly induced secretions and analyzed using LC-MS/MS; peptide spectra were matched to the transcriptome to fingerprint the entire protein primary sequences. We present the full sequences of fourteen novel quagga mussel byssal proteins, named Dreissena bugensis foot proteins 4 to 17 (Dbfp4–Dbfp17), and new sequence data for two previously observed byssal proteins Dbfp1 and Dbfp2. Theoretical masses of the newly discovered proteins range from 4.3 kDa to 21.6 kDa. These protein sequences are unique but contain features similar to glue proteins from other species, including a high degree of polymorphism, proteins with repeated peptide motifs, disordered protein structure, and block structures.

We use Rhizocephala to illustrate the problems inherent in estimating the phylogeny of parasitic crustaceans. The adult rhizocephalan parasite has such a reduced morphology that little else than the presence of a moulted cuticle relegates them to Arthropoda. Therefore, until the advent of molecular phylogenetic analysis relegation of the Rhizocephala to taxon relied exclusively on larval characters. The reduced adult morphology also entailed that very few characters were available for intrinsic rhizocephalan systematics and virtually none that could be compared with any outgroup. Thus, rhizocephalan taxonomy relied only on analysis within the group and, with few exceptions, was not based on any phylogenetic principles. The advent of DNA methods in phylogeny confirmed, with high confidence, rhizocephalans as cirripedes and nested them within the taxon as the sister group to Thoracica. This result was supported by SEM studies of the cypris larvae. Additional molecular phylogenetic studies yielded detailed insight into rhizocephalan relationships, culminating in the phylogeny presented here, which includes species from all but one family. Contrary to traditional hypotheses, the new phylogeny shows that infection of the host using a kentrogon stage represents the plesiomorphic condition, while rhizocephalans (Akentrogonida) without this stage are advanced. In this analysis, both Kentrogonida and the species-rich Sacculinidae are paraphyletic. In addition, recent hypotheses on family-level relationships in Akentrogonida, based on larval structure and the sexual system, were largely confirmed. This shows that when accurately analysed in a strict homology regime, morphological characters can be powerful partners to molecular data in elucidating rhizocephalan phylogeny.

The barnacle Anelasma squalicola is a marine epibiont found on members of the species-rich, deep-sea lantern shark family Etmopteridae (Figure 1A) but is unlike any other epibiotic thoracian barnacles [1]. While many barnacle species are associated with various marine animals including turtles and whales, with the exception of Anelasma these all retain a filter-feeding lifestyle and have a commensal relationship with their host; despite often being deeply embedded in the dermis, no other species has been reported as feeding on its host. Although Anelasma is fully equipped with cirri (thoracic appendages), these are no longer used for filter feeding [1]. Instead, Anelasma embeds a stalk with root-like structures into the flesh of the shark (Figure S1C in Supplemental Information, published with this article online) that it uses to parasitize its host. Here, we show that specimens of Anelasma sampled from all over the world show very little genetic differentiation, suggesting that this innovation coincided with a rapid worldwide expansion.

Chapter 2 Planning Marine Field Studies Jennifer Devine, Jennifer DevineSearch for more papers by this authorKeno Ferter, Keno FerterSearch for more papers by this authorHenrik Glenner, Henrik GlennerSearch for more papers by this authorJon Thomassen Hestetun, Jon Thomassen HestetunSearch for more papers by this authorKnut Helge Jensen, Knut Helge JensenSearch for more papers by this authorLeif Nøttestad, Leif NøttestadSearch for more papers by this authorMichael Pennington, Michael PenningtonSearch for more papers by this authorDavid John Rees, David John ReesSearch for more papers by this authorAnne Gro Vea Salvanes, Anne Gro Vea SalvanesSearch for more papers by this authorKjersti Sjøtun, Kjersti SjøtunSearch for more papers by this authorArved Staby, Arved StabySearch for more papers by this author Jennifer Devine, Jennifer DevineSearch for more papers by this authorKeno Ferter, Keno FerterSearch for more papers by this authorHenrik Glenner, Henrik GlennerSearch for more papers by this authorJon Thomassen Hestetun, Jon Thomassen HestetunSearch for more papers by this authorKnut Helge Jensen, Knut Helge JensenSearch for more papers by this authorLeif Nøttestad, Leif NøttestadSearch for more papers by this authorMichael Pennington, Michael PenningtonSearch for more papers by this authorDavid John Rees, David John ReesSearch for more papers by this authorAnne Gro Vea Salvanes, Anne Gro Vea SalvanesSearch for more papers by this authorKjersti Sjøtun, Kjersti SjøtunSearch for more papers by this authorArved Staby, Arved StabySearch for more papers by this author Book Editor(s):Anne Gro Vea Salvanes, Anne Gro Vea Salvanes Department of Biology, University of Bergen, Bergen, NorwaySearch for more papers by this authorJennifer Devine, Jennifer Devine Institute of Marine Research (IMR), Bergen, NorwaySearch for more papers by this authorKnut Helge Jensen, Knut Helge Jensen Department of Biology, University of Bergen, Bergen, NorwaySearch for more papers by this authorJon Thomassen Hestetun, Jon Thomassen Hestetun Department of Biology, University of Bergen, Bergen, NorwaySearch for more papers by this authorKjersti Sjøtun, Kjersti Sjøtun Department of Biology, University of Bergen, Bergen, NorwaySearch for more papers by this authorHenrik Glenner, Henrik Glenner Department of Biology, University of Bergen, Bergen, NorwaySearch for more papers by this author First published: 01 December 2017 https://doi.org/10.1002/9781119184362.ch2 AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter presents various ways to design a scientific survey for marine field studies, including a description of the most used designs. This is followed by descriptions of some currently employed survey designs for littoral and benthos field studies: an oceanic survey to estimate the abundance of mackerel; a bottom trawl survey to monitor demersal fish populations; a hydroacoustic survey to study the diel vertical migration of mesopelagic organisms, and lastly, a survey design to study barotrauma in physoclistous fish species. The design of a survey can influence the outcomes of the analysis implementing a design that will allow for answering the question without bias is crucial. There are two standard survey designs for field studies. One common design is a stratified random survey. The other common survey design for field studies is a systematic survey. An important aspect for designing a field survey is to determine how and how much to sample at each station. Marine Ecological Field Methods: A Guide for Marine Biologists and Fisheries Scientists RelatedInformation

The genus Maurolicus comprises extremely abundant vertically-migrating fishes that have considerable biomass in a number of regions worldwide. The genus was generally considered monotypic, with a single species, M. muelleri (Gmelin, 1789), inhabiting all world oceans. Based on differences in combinations of a limited number of morphometric characters, 15 separate species have been proposed, mostly associated with different ocean basins and seamounts. However, due to similarities in external morphology and overlap in ranges of morphometric characteristics, there remains a need for further validation of these species. Here, we present results of a multi-gene analysis, together with morphological data, for five putative Maurolicus species from multiple locations in the northern and southern hemispheres. Sampling encompasses described species from the North and South Atlantic, Mediterranean Sea, south-east Indian Ocean and the western South Pacific. Mitochondrial (16S and COI) and nuclear (ITS-2) gene sequences for 120 specimens were used in Maximum Parsimony and Bayesian Inference analyses as well as creation of haplotype networks. Morphological character analyses were based on data from 279 adult individuals. Several clear groupings emerge, conflicting with previously recognised species: (1) a ‘northern’ clade comprising Maurolicus muelleri and M. amethystinopunctatus, (2) a ‘southern’ clade comprising M. australis, M. walvisensis (also M. japonicus) and (3) eastern Equatorial and western North Atlantic M. weitzmani. The southern clade taxa are genetically indistinguishable and not well defined morphologically and present a clear case for synonymisation as M. australis. Synonymisation is also proposed for M. muelleri and M. amethystinopunctatus, with limited morphological variation likely to reflect physical and biological differences experienced north / south of the sub-polar front. Maurolicus weitzmani is clearly differentiated from all other Maurolicus species on both a molecular and morphological basis. Studies of genetic and morphological diversity in Maurolicus will further contribute to the question of ‘what constitutes a species in the open ocean?’, where a complex picture is emerging of both unexpected variation, as well as the unexpectantly absent genetic variation, in cosmopolitan taxa.

The rhizocephalan Sacculina shiinoi sp. nov. parasitizes three species of Upogebia in Japan. It is described morphologically and compared with another Upogebia parasite, Sacculina upogebiae Shiino, 1943 from Japan and Korea. These two species are the only sacculinids that parasitize mud shrimps. DNA analyses clearly show the two species to be separate and not closely related. The cuticle differs in being provided with close-set, branched, and spiny excrescences in S. shiinoi, while it lacks excrescences, but forms small scales in S. upogebiae. In S. upogebiae, the bulbous sperm-producing part and the narrow receptacle duct are separated by a compartmentalized mid portion, which is missing in S. shiinoi. A ridge, having a thickened, fluffy cuticle with a U-shaped course, passes across the visceral mass between the two receptacle openings in S. shiinoi. Such a structure has never been described in other rhizocephalans, and its function is uncertain.

The invasive freshwater mollusc Dreissena bugensis (quagga mussel) sticks to underwater surfaces via a proteinacious 'anchor' (byssus), consisting of a series of threads linked to adhesive plaques. This adhesion results in the biofouling of crucial underwater industry infrastructure, yet little is known about the proteins responsible for the adhesion. Here the identification of byssal proteins extracted from freshly secreted byssal material is described. Several new byssal proteins were observed by gel electrophoresis. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to characterize proteins in different regions of the byssus, particularly those localized to the adhesive interface. Byssal plaques and threads contain in common a range of low molecular weight proteins, while several proteins with higher mass were observed only in the plaque. At the adhesive interface, a plaque-specific similar to 8.1 kDa protein had a relative increase in signal intensity compared to the bulk of the plaque, suggesting it may play a direct role in adhesion.

The freshwater zebra mussel, Dreissena polymorpha, is an invasive, biofouling species that adheres to a variety of substrates underwater, using a proteinaceous anchor called the byssus. The byssus consists of a number of threads with adhesive plaques at the tips. It contains the unusual amino acid 3, 4-dihydroxyphenylalanine (DOPA), which is believed to play an important role in adhesion, in addition to providing structural integrity to the byssus through cross-linking. Extensive DOPA cross-linking, however, renders the zebra mussel byssus highly resistant to protein extraction, and therefore limits byssal protein identification. We report here on the identification of seven novel byssal proteins in the insoluble byssal matrix following protein extraction from induced, freshly secreted byssal threads with minimal cross-linking. These proteins were identified by LC-MS/MS analysis of tryptic digests of the matrix proteins by spectrum matching against a zebra mussel cDNA library of genes unique to the mussel foot, the organ that secretes the byssus. All seven proteins were present in both the plaque and thread. Comparisons of the protein sequences revealed common features of zebra mussel byssal proteins, and several recurring sequence motifs. Although their sequences are unique, many of the proteins display similarities to marine mussel byssal proteins, as well as to adhesive and structural proteins from other species. The large expansion of the byssal proteome reported here represents an important step towards understanding zebra mussel adhesion.

On the basis of 104 individuals of Cottunculus from the Norwegian coast, the Barents Sea, Svalbard and north-east Greenland waters, this paper evaluates the descriptive taxonomic characters of three species Cottunculus sadko, Cottunculus microps and Cottunculus konstantinovi and links the character variation to genetic characterizations. Eleven morphological characters used as diagnostic characters in the original descriptions of these species were analysed in pair-wise character comparisons. All characters show cross-species traits when in combination with each other, and all individuals show traits of more than one of the species. Partial cytochrome oxidase c subunit I (coI) gene sequences from 21 individuals, covering the morphological variation among the specimens, show little variation among the individuals. From these results, it is concluded that the descriptive characters do not support the maintenance of more than one species. It is recommended that C. microps remains the name for this species, with C. sadko and C. konstantinovi as junior synonyms.

In his monograph on Cirripedia from 1851, Darwin pointed to a highly unusual, plateless, and most likely parasitic barnacle of uncertain phylogenetic affinity. Darwin's barnacle was Anelasma squalicola, found on deep-water sharks of the family Etmopteridae, or lantern sharks. The barnacle is uncommon and is therefore rarely studied. Recent observations by us have shown that they occur at an unusually high prevalence on the velvet belly lantern shark, Etmopterus spinax, in restricted fjord areas of western Norway. A phylogenetic analysis based on ribosomal DNA data (16S, 18S, and 28S) from 99 selected barnacle species, including all available pedunculate barnacle sequences from GenBank, shows that A. squalicola is most closely related (sister taxon) to the pedunculate barnacle Capitulum mitella. Both C. mitella and species of Pollicipes, situated one node higher in the tree, are conventional suspension feeders from the rocky intertidal. Our phylogenetic analysis now makes it possible to establish morphological homologies between A. squalicola and its sister taxon and provides the evolutionary framework to explain the unprecedented transition from a filter-feeding barnacle to a parasitic mode of life.