Sea Hare Research Articles

The biologically and ecologically important natural products from the Chinese sea hare Bursatella leachii: structures, stereochemistry and beyond

A novel amide alkaloid, bursatamide A (1), featuring an unprecedented propyl-hexahydronaphthalene carbon framework, was isolated from the infrequently studied sea hare Bursatella leachi, alongside a new 3-phenoxypropanenitrile alkaloid, bursatellin B (2), and twelve known compounds. The structures of 1 and 2 were elucidated through comprehensive spectroscopic data analyses, while their relative and absolute configurations (ACs) were established through total synthesis and a series of quantum chemical calculations, including calculated electronic circular dichroism (ECD) spectra, optical rotatory dispersion (ORD) methods, and DP4+ probability analyses. Bursatamide A (1) demonstrated inhibitory effects against the human pathogenic bacteria Listeria monocytogenes and Vibrio cholerae. Erythro-bursatellin B (21), a diastereoisomer of 2, exhibited notable antibacterial activity against the fish pathogenic bacterium Streptococcus parauberis FP KSP28, with an MIC90 value of 0.0472 μg·mL−1.

Nematicidal Potentiality of Four Marine Molluscans' Defensive Secretions From the Red Sea Against Syphacia obvelata (Nematoda: Oxyuridae) In Vitro.

The continuous requirement to substitute safe and affordable alternatives for helminth medications, as well as address the resistance of some used drug classes, introduced bioactive products derived from marine animals into the field of competition; however, almost all the previous research only focused on their impact on bacterial and protozoal infection. In the present work, we investigated the potential in vitro nematocidal effect of the aqueous extract of defense secretions for four species of marine mollusks: two cephalopods, namely the cuttlefish Sepia pharaonis and the common Octopus Octopus vulagris and two gastropods, the sea hare Aplysia argus and the sea slug Berthillina citrina, against the adult murine pinworm Syphacia obvelata. Data showed dose and time efficacy in all examined extracts. The sea slug's skin acid secretion has the highest impact, causing death in the cultivated worms, followed by the ink of the sea hare, the common octopus and the cuttlefish, where LC90 after 10 h of exposure were 250, 290, 316, and 391 µg/mL, respectively. Comparatively with the control and albendazole-treated groups, the skin acid secretion of the sea slug caused the highest levels of the antioxidant enzymes SOD, Cat and GSH-PX; however, albendazole prompted the highest level of GSH-PX enzyme in all experimental groups.

The role of sea hares as significant algal herbivores on the Southern Great Barrier Reef

Sea hares are cryptic, herbivorous sea slugs present on many coral reefs worldwide. Although they are known to consume high quantities of macroalgae, they are rarely considered or quantified in assessing algal suppression. Their role as algal suppressors is not well understood, therefore this study sought to quantify sea hare herbivory on the abundant red algal genus Laurencia. The sea hares Aplysia dactylomela, Dolabella auricularia and Dolabella sp. were collected and used in herbivory trials in aquaria at Heron Island on the Southern Great Barrier Reef to quantify their rate of consumption. A. dactylomela consumed 76.9 g partially dried weight of Laurencia per 24-h, which was significantly more than the other species, with D. auricularia consuming an average of 22.5 g and Dolabella sp. consuming 37.4 g partially dried weight. Consumption of Laurencia by A. dactylomela increased with body size, with the exception of the smallest animals, which ate up to 12.5 times their body weight. D. auricularia consumed significantly more algae than was lost in control tanks. Although we observed Dolabella sp. feeding on Laurencia, the amount consumed was not significantly different to loss of algae in control tanks. The rate of herbivory on Laurencia by A. dactylomela is comparable or greater than that of more commonly studied reef herbivores such as fishes and urchins, which suggests that they may contribute to algal suppression on coral reefs and further studies are warranted to evaluate their possible role in coral-algal phase shift dynamics.

Firts records of Bursatella leachii de Blainville 1817 (Mollusca; Gastropoda; Aplysiidae) in Black Sea

ABSTRACT This study reports, for the first time, the discovery of the ragged sea hare Bursatella leachii de Blainville 1817 in the Black Sea. The observations were made during the month of September 2023 at depths varying between 1,0 and 4,0 meters by scuba and snorkeling. A total of 484 specimens of this species were found. Of these, a part were observed in the sandy-muddy bottom of Kumbaba beach and a part in the sandy bottom of Uzunkum beach, in the Sile district (Istanbul province). The estimate of the density of individuals per square meter of seabed made it possible to highlight how the high number of individuals was present on the Kumbaba beach near the mouth of the Türknil river. It could be hypothesized that the introduction of this species into Black Sea could have occurred through natural means. This may have been possible for two reasons; the first is that the beaches of Sile are a few kilometers from the Bosphorus Canal while the other reason lies in the fact that the report of B. leachii closest to the town of Sile dates back to January 2020, when the species was observed in the seabed of the coast southern Dardanelles (Çanakkale Strait). To be certain of what has been stated, monitoring should be carried out on a regular basis but, at this moment, this hypothesis appears to be the most real. Keywords: Bursatella leachii, Black Sea, Turkey, AIS, NIS

Host response to Aplysia Abyssovirus 1 in nervous system and gill

The California sea hare (Aplysia californica) is a model for age associated cognitive decline. Recent researched identified a novel nidovirus, Aplysia Abyssovirus 1, with broad tropism enriched in the Aplysia nervous system. This virus is ubiquitous in wild and maricultured, young and old animals without obvious pathology. Here we re-evaluated gene expression data from several previous studies to investigate differential expression in the nervous system and gill in response to virus and aging as well as the mutational spectrum observed in the viral sequences obtained from these datasets. Viral load and age were highly correlated, indicating persistent infection. Upregulated genes in response to virus were enriched for immune genes and signatures of ER and proteostatic stress, while downregulated genes were enriched for mitochondrial metabolism. Differential expression with respect to age suggested increased iron accumulation and decreased glycolysis, fatty acid metabolism, and proteasome function. Interaction of gene expression trends associated with viral infection and aging suggest that viral infection likely plays a role in aging in the Aplysia nervous system. Mutation analysis of viral RNA identified signatures suggesting ADAR and AID/APOBEC like deaminase act as part of Aplysia anti-viral defense.

PEGylated Recombinant Aplysia punctata Ink Toxin Depletes Arginine and Lysine and Inhibits the Growth of Tumor Xenografts.

In recent years, a novel treatment method for cancer has emerged, which is based on the starvation of tumors of amino acids like arginine. The deprivation of arginine in serum is based on enzymatic degradation and can be realized by arginine deaminases like the l-amino acid oxidase found in the ink toxin of the sea hare Aplysia punctata. Previously isolated from the ink, the l-amino acid oxidase was described to oxidate the essential amino acids l-lysine and l-arginine to their corresponding deaminated alpha-keto acids. Here, we present the recombinant production and functionalization of the amino acid oxidase Aplysia punctata ink toxin (APIT). PEGylated APIT (APIT-PEG) increased the blood circulation time. APIT-PEG treatment of patient-derived xenografted mice shows a significant dose-dependent reduction of tumor growth over time mediated by amino acid starvation of the tumor. Treatment of mice with APIT-PEG, which led to deprivation of arginine, was well tolerated.

Synthesis and Late-Stage Modification of (-)-Doliculide Derivatives Using Matteson's Homologation Approach.

(-)-Doliculide, a marine cyclodepsipeptide derived from the Japanese sea hare, Dolabella auricularia, exhibits potent cytotoxic properties, sparking interest in the field of synthetic chemistry. It is comprised of a peptide segment and a polyketide moiety, rendering it amenable to Matteson's homologation methodology. This technique facilitates the diversification of the distinctive polyketide side chain, thereby permitting the introduction of functional groups in late stages for modifications of the derived compounds and studies on structure-activity relationships.

First record of Bursatella leachii de Blainville, 1817 (Mollusca: Gastropoda: Aplysiidae) in Corsica (France, NW Mediterranean)

This study reports for the first time the occurrence of ragged sea hare Bursatella leachii de Blainville, 1817 in Corsica (France, NW Mediterranean Sea). The species has colonized the shallow waters (0.1–0.5 m depth) of Diana Lagoon mainly constituted of sandy-muddy bottoms and Cymodocea nodosa and Zostera noltei seagrass beds. A total of 166 individuals were inventoried in June 2023 during the survey carried out along more than 300 m of shoreline. The highest density of individuals (0.63 ind m−2) was mainly reported in very warm and sheltered water basins formed by the accumulation of woody debris (mean ± SE: 0.17 ± 0.06 ind m−2). Morphometric measurements of specimens showed an average body length of 54.3 ± 1.7 mm and weight of 14.7 ± 0.8 g. The introduction pathways of this species into this coastal lagoon may have resulted from the natural dispersal of larvae or juveniles or via the shellfish farming located in the lagoon. Extensive monitoring should be carried out along the coast of Corsica to shed light on the occurrence of the species and its spatio-temporal spread. A literature review on B. leachii has enabled us to update the existing dataset on the species distribution. The species is now confirmed from 21 out of 23 countries surrounding the Mediterranean basin.

Marine Resources for Marine-Derived Drugs: A Review

The oceans are the world’s most important sources of biological activity, water, and biomass production. They supply food, oxygen, and other natural products critical for human existence, and interactions between the oceans and the climate. The oceans serve as the world’s greatest reservoir of biodiversity, including marine mammals, fish, crustaceans, molluscs, and countless species of zoophytoplankton. The ocean is a key source of organisms that are beginning to provide new and potent drugs for the treatment of human disease, as well as new products that use in biotechnology. Ocean can support human health, through providing new sources of drugs to treat human disease. Bioactive metabolites derived from marine organisms provide a rich source of chemical diversity that can contribute to design and development of new and potentially useful pharmaceutical agents. The marine ecosystem possesses efficient pharmaceutical materials to identify, isolate and characterize new compounds suitable for therapeutic purposes. Marine sponges, tunicates, fishes, soft corals, nudibranchs, sea hares, molluscs, echinoderms, bryozoans, prawns, shells, sea slugs, and marine microorganisms are sources of bioactive compounds. The current review is designed to collate all currently available data about the marine drugs with respect to sources, classification, chemical classes, metabolites of marine algae, fungi, bacteria and invertebrates, techniques for separation and isolation, and examples. This review aims to provide a holistic, multidisciplinary account of the current state of affairs on this topic.

Antibacterial activity of sea hare (Dolabella auricularia) egg string extracts against potentially pathogenic bacteria

Abstract. Liguez CGO, Tabugo SR. 2023. Antibacterial activity of sea hare (Dolabella auricularia) egg string extracts against potentially pathogenic bacteria. Biodiversitas 24: 6675-6683. Pharmaceutical industries now recognize the vast variety of ocean organisms, each possessing distinct biological characteristics. Sea hares, for example, are marine organisms that use bioactive chemicals to defend against predators, including their eggs. To explore the potential antibacterial properties of sea hare species (Dolabella auricularia) found in Pujada Bay, Philippines, egg strings were collected and extracted using hexane and methanol solvents. The antibacterial activity of each fraction was then determined through Minimum Inhibitory Concentration (MIC) testing against four potentially pathogenic bacteria, two gram-positive strains (Staphylococcus aureus, Bacillus subtilis) and two gram-negative strains (Escherichia coli, Pseudomonas aeruginosa). The broth microdilution method was employed to assess the antibacterial activity of Dolabella auricularia egg strings. The results revealed the MIC values for the four bacterial strains. The hexane extracts of both extract 1 and extract 2 exhibited a MIC of 0. 23 and 0.33 mg/mL and a MIC of 0.52 and 0.125 mg/mL against P. aeruginosa, respectively. The methanolic extracts (1 and 2) displayed a MIC of 1.46 and 2.83 mg/mL against E. coli and an even more potent MIC of 1.33 and 0.79 mg/mL against P. aeruginosa. In the case of B. subtilis, the hexane extracts (1 and 2) had a MIC of 1.5 and 0.54 mg/mL, while the methanolic extracts (1 and 2) exhibited a MIC of 1.17 mg/mL and 0.83 mg/mL. Lastly, against S. aureus, hexane extracts (1 and 2) suppressed the growth with a MIC of 0.77 mg/mL and 0.25 mg/mL, respectively, while both methanolic extracts (1 and 2) demonstrated a MIC of 3.33 mg/mL. These findings showcase the promising antibacterial activity of Dolabella auricularia egg string extracts and highlight their potential for further investigation and development in the pharmaceutical field.

Untangling the Gordian Knot of Aplysia sea hare egg masses: An integrated open-hardware system for standardized egg strand sizing and packaging for cryopreservation research and application

The California sea hare (Aplysia californica) provides a powerful biomedical model system for studying aspects of neurological development and damage, behavior, aging, and hypoxia. Aplysia encapsulate their zygotes within strands that result in tangled egg masses that greatly complicate culture and experimentation. The historical and current importance of Aplysia for biomedical research and the mounting climate crisis necessitates protection of Aplysia genetic resources. The goal of this work was to prototype open-hardware sizing, processing, and packaging devices for A. californica early life stages suitable for integration into a cryopreservation pathway. The Strand Centi-Sizer was a low-cost, fused filament fabrication 3-D printable device that increased experiment preparation efficiency and standardized the cutting of egg strands customizable to user needs. A downstream system of 3-D printed devices was also prototyped to address inefficiencies in handling of egg strand sections for processing and packaging into existing cryopreservation straw platforms. Time studies were conducted comparing manual methods (i.e., no specialized equipment) with open hardware to demonstrate utility of the devices and to encourage community members to design and prototype new devices to address recurrent and novel problems in other aquatic animals that produce egg strands. Improvements in design could further increase efficiency, standardization, and reproducibility, and extend the application of these devices to other research communities, such as shrimp or salamander spermatophores, sea anemone body part (e.g., pedal lacerate) cryopreservation, or study areas such as vitrification.

Tutorial: using NEURON for neuromechanical simulations.

https://github.com/fietkiewicz/PointerBuilder.

First record of microplastic in the Brazilian sea hare Aplysia brasiliana Rang, 1828 (Mollusca: Aplysiidae)

The presence of plastic debris in the marine environment has reached massive levels in the past decades. In marine environments, microplastics can exist for hundreds of years and the presence of microplastics in this environment has been reported since 1970 and since then has been considered ubiquitous. Mollusks are being used as microplastic pollution indicators, especially in coastal areas and bivalves are more often used in microplastic-monitoring studies. On the other hand, gastropods are poorly used as indicators for microplastic pollution, even though they are the most diverse group of mollusks. The sea hares of the genus Aplysia are herbivorous gastropods, important model organisms commonly used in neuroscience studies, isolating the compounds in their defensive ink. Until today, there is no previous record of the presence of MPs in Aplysia gastropods. Therefore, this study aims to investigate the presence of microplastics in tissues of A. brasiliana found in southeastern Brazil. We collected seven individuals of A. brasiliana from a beach in southeastern Brazil, dissected them to isolate the digestive tract and the gills, and digested the tissues with a solution of 10 % NaOH. In the end, 1021 microplastic particles were found, 940 in the digestive tissue, and 81 in the gills. These results represent the first record of the presence of microplastics in the Brazilian sea hare A. brasiliana.

Investigating the internal system of defense of Gastropoda Aplysia depilans (Gmelin, 1791): Focus on hemocytes.

The internal defense system of mollusks represents an efficient protection against pathogens and parasites, involving several biological immune processes, such as phagocytosis, encapsulation, cytotoxicity, and antigenic recognition of self/non-self. Mollusks possess professional, migratory, and circulating cells that play a key role in the defense of the organism, the hemocytes. Several studies have been performed on hemocytes from different mollusks, but, to date, these cells are still scarcely explored. Different hemocyte populations have been found, according to the presence or absence of granules, size, and the species of mollusks studied. Our study aims to deepen the knowledge of the hemocytes of the gastropod Aplysia depilans using morphological techniques and light and confocal microscopy, testing Toll-like receptor 2, inducible nitric oxide synthetase, and nicotinic acetylcholine receptor alpha 7 subunit. Our results show two hemocyte populations distinguishable by size, and presence/absence of granules in the cytoplasm, strongly positive for the antibodies tested, suggesting for the first time the presence of these receptors on the surface of sea hare hemocytes by immunohistochemistry. These data help in the understanding of the immune system of this gastropod, providing additional data for comprehending the evolution of the defense response in metazoan phylogenesis.

Monitoring the Reproduction and Development of Eggs in the Sea Hare Aplysia fasciata under Laboratory Conditions

This study looks at spawning patterns, egg mass shape, and embryo development to learn more about the reproductive biology of the A. fasciata species that lives in Libya's coastal waters. In June 2022, eight mature Aplysia fasciata collected from Tajura coast and kept into aquarium contain aerated seawater and marine algae (Ulva lactuca). After five days, a mating couple was seen in the aquarium, and, a mass of fertilized eggs were produced. The clusters eggs were transfer to new aquarium. After few hours, the eggs started development to embryo and at 10 day the egg masses colour changed to a brownish as the embryo developed to the trochophore stage and started to rotate inside capsules. After 16 day of spawning the trochophore broke the egg capsules to hatch as free swimming larvae (the veliger stage). Unfortunately, after 25 day of fertilized eggs all larvae died as veliger. Probably, the result of inadequate conditions for rearing or lack an availability of appropriate food. Whereas A. fasciata has never been recorded before in the Libyan waters.

Discovery of New Cytotoxic Aplaminone Derivatives from the Sea Hare Aplysia kurodai and Elucidation of Their Accumulation from Local Sea Algae through the Food Chain

AbstractThe shell‐less herbivorous marine mollusk (sea hare) Aplysia kurodai is known to contain a variety of bioactive substances. While these compounds have been thought to originate from sea algae or their associated microbes, most of their origin and acquisition pathways are still unclear. Six new cytotoxic aplaminone derivatives, bromodopamine‐terpenoid hybrid molecules, were isolated from A. kurodai. Among them, isoaplaminone had a reverse prenyl group at the C15 aliphatic chain, which is a rare structural feature from the viewpoint of terpenoid biosynthesis. Investigation for chemical components in A. kurodai and the sea algae collected at several different locations revealed that two major aplaminones were contained in the Laurencia complex species at specific sites. Our chemical and ecological studies provide new insights into the origin of marine alkaloid toxins and their dynamism through the food chain.

Welcome Matt and farewell Ken.

Welcome Matt and farewell Ken.

New nor-chamigrane and bisabolane sesquiterpenoids from the sea hare Aplysia dactylomela

Two new nor-chamigranes and a new bisabolane sesquiterpene, given the trivial names dactylomelanins CE (1–3), were isolated from the sea hare Aplysia dactylomela along with a known compound (4). Their structures and absolute configurations were elucidated by analysis of their HRESIMS, NMR and ECD spectroscopic data. The position of the bromine atom in the structure of 1 was established by quantum chemical calculations of the NMR chemical shifts and by analysis of DP4+ probability. Compounds 1–4 were evaluated for their cytotoxicity against three cell lines, A549, MCF-7, and HepG2.

Biological Characteristics of the Wedge Sea Hare (Dolabella auricularia)

Dolabella auricularia, also known as the wedge sea hare, is a marine species which belongs to the gastropods. Dolabella is called the sea hare because it has rhinophores, the two rabbit-ears-like tentacles on the top of their head. These animals have secondary metabolites which are important in biomedical research. In addition, this animal is also known as an algae cropper, so that it is utilized in aquaculture to clean seawater systems. This short article describes the biological properties of it so that it becomes a marine biota that can be utilized in biomedicine and aquaculture.

Structural and functional analysis of a tandem repeat galacturonic acid-binding lectin from the sea hare Aplysia californica

A d-galacturonic acid-specific lectin, named AcL, was purified from the sea hare Aplysia californica by galactose-agarose affinity chromatography. AcL has a molecular mass of 27.5 kDa determined by MALDI-TOF mass spectrometry. This lectin shows a good affinity for d-galacturonic acid and a lower affinity for galactosides: raffinose, melibiose, α and β-lactose, and d-galactose. We determined the amino acid sequence of AcL by trypsin digestion and subsequent peptide analysis by mass spectrometry, resulting in a 238 amino acid protein with a theoretical molecular mass of 26.4 kDa. The difference between the theoretical and experimental values can be attributed to post-translational modifications. Thiol-disulfide quantification discerned five disulfide bonds and three free cysteines. The structure of Acl is mainly comprised of beta sheets, determined by circular dichroism, and predicted with AlphaFold. Theoretical models depict three nearly identical tandem domains consisting of two beta sheets each. From docking analysis, we identified AcL glycan-binding sites as multiple conserved motifs in each domain. Furthermore, phylogenetic analysis based on its structure and sequence showed that AcL and its closest homologues (GalULs) form a clear monophyletic group, distinct from other glycan-binding proteins with a jelly-roll fold: lectins of types F and H. GalULs possess four conserved sequence regions that distinguish them and are either ligand-binding motifs or stabilizing network hubs. We suggest that this new family should be referred to as GalUL or D-type, following the traditional naming of lectins; D standing for depilans, the epithet for the species (Aplysia depilans) from which a lectin of this family was first isolated and described.