Metamorphosis Of Larvae Research Articles

A transcriptome-wide analysis provides novel insights into how Metabacillus indicus promotes coral larvae metamorphosis and settlement

BackgroundCoral reefs experience frequent and severe disturbances that can overwhelm their natural resilience. In such cases, ecological restoration is essential for coral reef recovery. Sexual reproduction has been reported to present the simplest and most cost-effective means for coral reef restoration. However, larval settlement and post-settlement survival represent bottlenecks for coral recruitment in sexual reproduction. While bacteria play a significant role in triggering coral metamorphosis and settlement in many coral species, the underlying molecular mechanisms remain largely unknown. In this study, we employed a transcriptome-level analysis to elucidate the intricate interactions between bacteria and coral larvae that are crucial for the settlement process.ResultsHigh Metabacillus indicus strain cB07 inoculation densities resulted in the successful induction of metamorphosis and settlement of coral Pocillopora damicoris larvae. Compared with controls, inoculated coral larvae exhibited a pronounced increase in the abundance of strain cB07 during metamorphosis and settlement, followed by a significant decrease in total lipid contents during the settled stage. The differentially expressed genes (DEGs) during metamorphosis were significantly enriched in amino acid, protein, fatty acid, and glucose related metabolic pathways. In settled coral larvae induced by strain cB07, there was a significant enrichment of DEGs with essential roles in the establishment of a symbiotic relationship between coral larvae and their symbiotic partners. The photosynthetic efficiency of strain cB07 induced primary polyp holobionts was improved compared to those of the negative controls. In addition, coral primary polyps induced by strain cB07 showed significant improvements in energy storage and survival.ConclusionsOur findings revealed that strain cB07 can promote coral larval settlement and enhance post-settlement survival and fitness. Manipulating coral sexual reproduction with strain cB07 can overcome the current recruitment bottleneck. This innovative approach holds promise for future coral reef restoration efforts.

Local differences in robustness to ocean acidification.

Ocean acidification (OA) caused by increased atmospheric carbon dioxide is affecting marine systems globally and is more extreme in coastal waters. A wealth of research to determine how species will be affected by OA, now and in the future, is emerging. Most studies are discrete and generally do not include the full life cycle of animals. Studies that include the potential for adaptation responses of animals from areas with different environmental conditions and the most vulnerable life stages are needed. Therefore, we conducted experiments with the widely distributed blue mussel, Mytilus edulis, from populations regularly exposed to different OA conditions. Mussels experienced experimental conditions prior to spawning, through embryonic and larval development, both highly vulnerable stages. Survivorship to metamorphosis of larvae from all populations was negatively affected by extreme OA conditions (pH 7.3, Ωar, 0.39, pCO2 2479.74), but, surprisingly, responses to mid OA (pH 7.6, Ωar 0.77, pCO21167.13) and low OA (pH 7.9, Ωar 1.53, pCO2 514.50) varied among populations. Two populations were robust and showed no effect of OA on survivorship in this range. One population displayed the expected negative effect on survivorship with increased OA. Unexpectedly, survivorship in the fourth population was highest under mid OA conditions. There were also significant differences in development time among populations that were unaffected by OA. These results suggest that adaptation to OA may already be present in some populations and emphasizes the importance of testing animals from different populations to see the potential for adaptation to OA.

The mussel larvae microbiome changes in response to a temperature rise

Ocean warming caused by global climate change influences the function, diversity, and community dynamics of commensal microorganisms, including the hemolymph and the gut microbiota in mussels. However, the microbiota in hard-shelled mussel (Mytilus coruscus) larvae and the effect of temperature on the microbial community structure have yet to be studied. Herein, we investigated the core microbiota of M. coruscus larvae and the impact of acute (4 h) and gradual (4 days) exposure to a rise in seawater temperature from 21 to 25 °C. Eleven core genera were identified in M. coruscus larvae by 16S rDNA gene sequencing: Alteromonas, Brevundimonas, Delftia, Microbacterium, Neptuniibacter, Neptunomonas, Pseudoalteromonas, Rhodococcus, Stenotrophomonas, Tenacibaculum, and Thalassotalea. The microbiota of larvae in the short exposure treatment was similar to the control. However, the abundance of Delftia, Neptunomonas, Pseudoalteromonadaceae, Rhodococcus, and Stenotrophomonas decreased significantly in the long-exposure larvae. In contrast, at the genus level, the abundance of Tenacibaculum increased significantly. Diversity and multivariate analyses confirmed that the microbiota patterns were linked to seawater warming over the long term. Microbiota diversity did not change significantly, regardless of whether the seawater temperature increased quickly or slowly; however, we observed a significant increase in the microbiota species abundance at higher temperatures. Among the altered bacterial genera, Delftia, Neptunomonas, and Rhodococcus function in the degradation of organic compounds; Pseudoalteromonas is closely associated with mussel attachment and metamorphosis, and Tenacibaculum is an opportunistic pathogen that can cause marine mollusk death. The results suggest that marine heat waves caused by climate change may reduce the ability of symbiotic bacteria to degrade environmental toxins, will affect mussel larvae metamorphosis, and increase the abundance of opportunistic pathogens, thereby increasing the risk of disease and death of mussel larvae.

Regulatory effects of prolactin in amphibians

Prolactin (PRL) is a protein hormone of the anterior pituitary and has a diverse role in different aspects of amphibian life - in courtship, reproduction, larval development and in other physiological functions. The expression of PRL receptor mRNA is reported in skin, gill, liver, gut, kidney, gonads and many other organs of different groups of amphibians. PRL stimulates growth and inhibits the metamorphosis of larvae of several species of amphibians. PRL causes seasonal changes in sex accessory structures and secondary sexual characteristics. PRL affects metabolic regulation and suggests phylogenic conservation of its receptors. Plasma PRL concentration changes during the annual reproductive cycle in many amphibians. In courtship behavior of newt, PRL also induces the synthesis of the newt courtship pheromones. PRL acts on skin and its function is also associated with water drive in amphibians. PRL causes water retention in amphibians. PRL acts centrally or peripherally to induce the courtship behavior. The key goal of the paper is to understand the roles of PRL in various aspect of amphibian life, like in aspects of morphology, behaviour, physiological functions and how PRL interfere amphibian life in presence and absence of other chemical and biological factors.

Evaluation of natural resveratrol multimers as marine antifoulants

In the current study we investigate the antifouling potential of three polyphenolic resveratrol multimers (–)-hopeaphenol, vaticanol B and vatalbinoside A, isolated from two species of Anisoptera found in the Papua New Guinean rainforest. The compounds were evaluated against the growth and settlement of eight marine microfoulers and against the settlement and metamorphosis of Amphibalanus improvisus barnacle cyprids. The two isomeric compounds (–)-hopeaphenol and vaticanol B displayed a high inhibitory potential against the cyprid larvae metamorphosis at 2.8 and 1.1 μM. (–)-Hopeaphenol was also shown to be a strong inhibitor of both microalgal and bacterial adhesion at submicromolar concentrations with low toxicity. Resveratrol displayed a lower antifouling activity compared to the multimers and had higher off target toxicity against MCR-5 fibroblasts. This study illustrates the potential of natural products as a valuable source for the discovery of novel antifouling leads with low toxicity.

Effects of supplementary astaxanthin in egg custard on antioxidant capacity and non-specific immunity during larvae metamorphosis of giant freshwater prawn (Macrobrachium rosenbergii)

Effects of supplementary astaxanthin in egg custard on antioxidant capacity and non-specific immunity during larvae metamorphosis of giant freshwater prawn (Macrobrachium rosenbergii)

Ancestral glycoprotein hormone and its cognate receptor present in primitive chordate ascidian: Molecular identification and functional characterization

The glycoprotein hormone (GPH) system is fundamentally significant in regulating the physiology of chordates, such as thyroid activity and gonadal function. However, the knowledge of the GPH system in the primitive chordate ascidian species is largely lacking. Here, we reported an ancestral GPH system in the ascidian (Styela clava), which consists of GPH α subunit (Sc-GPA2), GPH β subunit (Sc-GPB5), and the cognate leucine-rich repeat-containing G protein-coupled receptor (Sc-GPHR). Comparative structure analysis revealed that distinct from vertebrate GPH β subunits, Sc-GPB5 was less conserved, showing an atypical N-terminal sequence with a type II transmembrane domain instead of a typical signal peptide. By investigating the presence of recombinant Sc-GPA2 and Sc-GPB5 in cell lysates and culture media of HEK293T cells, we confirmed that these two subunits could be secreted out of the cells via distinct secretory pathways. The deglycosylation experiments demonstrated that N-linked glycosylation only occurred on the conserved cysteine residue (N78) of Sc-GPA2, whereas Sc-GPB5 was non-glycosylated. Although Sc-GPB5 exhibited distinct topology and biochemical properties in contrast to its chordate counterparts, it could still interact with Sc-GPA2 to form a heterodimer. The Sc-GPHR was then confirmed to be activated by tethered Sc-GPA2/GPB5 heterodimer on the Gs-cAMP pathway, suggesting that Sc-GPA2/GPB5 heterodimer-initiated Gs-cAMP signaling pathway is evolutionarily conserved in chordates. Furthermore, in situ hybridization and RT-PCR results revealed the co-expression patterns of Sc-GPA2 and Sc-GPB5 with Sc-GPHR transcripts, respectively in ascidian larvae and adults, highlighting the potential functions of Sc-GPA2/GPB5 heterodimer as an autocrine/paracrine neurohormone in regulating metamorphosis of larvae and physiological functions of adults. Our study systematically investigated the GPA2/GPB5-GPHR system in ascidian for the first time, which offers insights into understanding the function and evolution of the GPH system within the chordate lineage.

Unique peptidic agonists of a juvenile hormone receptor with species-specific effects on insect development and reproduction

Juvenile hormones (JHs) control insect metamorphosis and reproduction. JHs act through a receptor complex consisting of methoprene-tolerant (Met) and taiman (Tai) proteins to induce transcription of specific genes. Among chemically diverse synthetic JH mimics (juvenoids), some of which serve as insecticides, unique peptidic juvenoids stand out as being highly potent yet exquisitely selective to a specific family of true bugs. Their mode of action is unknown. Here we demonstrate that, like established JH receptor agonists, peptidic juvenoids act upon the JHR Met to halt metamorphosis in larvae of the linden bug, Pyrrhocoris apterus. Peptidic juvenoids induced ligand-dependent dimerization between Met and Tai proteins from P. apterus but, consistent with their selectivity, not from other insects. A cell-based split-luciferase system revealed that the Met-Tai complex assembled within minutes of agonist presence. To explore the potential of juvenoid peptides, we synthesized 120 new derivatives and tested them in Met-Tai interaction assays. While many substituents led to loss of activity, improved derivatives active at sub-nanomolar range outperformed hitherto existing peptidic and classical juvenoids including fenoxycarb. Their potency in inducing Met-Tai interaction corresponded with the capacity to block metamorphosis in P. apterus larvae and to stimulate oogenesis in reproductively arrested adult females. Molecular modeling demonstrated that the high potency correlates with high affinity. This is a result of malleability of the ligand-binding pocket of P. apterus Met that allows larger peptidic ligands to maximize their contact surface. Our data establish peptidic juvenoids as highly potent and species-selective novel JHR agonists.

Integrating morphology and physiology of the key endocrine organ during tadpole development: The interrenal gland

Indirect development is widespread in anurans and is considered an ancestral condition. The metamorphosis of larvae into juveniles involves highly coordinated morphological, physiological, biochemical, and behavioral changes, promoted by the thyroid hormone and interrenal corticosteroids. Stress response to environmental changes is also mediated by corticosteroids, affecting the timing and rate of metamorphosis and leading to great developmental plasticity in tadpoles. Given the potential effect of interrenal gland ontogeny alterations on metamorphosis and the lack of studies addressing both the morphology and endocrinology of this gland in tadpoles, we present corticosterone (CORT) production and histological changes through the ontogeny of interrenal gland in the generalized pond-type tadpole of Rhinella arenarum (Anura, Bufonidae). This species shows the highest concentration of whole-body CORT by the early climax when drastic metamorphic changes begin. This is coincident with the morphological differentiation of steroidogenic cells and the formation of interrenal cords. By this stage, steroidogenic cells have a shrunken cytoplasm, with a significantly higher nucleus-to-cell diameter ratio. The lowest CORT concentration during premetamorphosis and late climax is associated with small undifferentiated cells with lipid inclusions surrounding large blood vessels between kidneys, and with cords of differentiated steroidogenic cells with a significantly lower nucleus-to-cell diameter ratio, respectively. Our study characterizes the morphological and physiological pattern of interrenal gland development, showing an association between certain histological and morphometric characteristics and CORT levels. Variations in this morpho-physiological pattern should be considered when studying the phenotypic plasticity or variable growth rates of tadpoles.

Bacteriophages improve survival and metamorphosis of larval Pacific oysters (Crassostrea gigas) exposed to Vibrio coralliilyticus strain RE98

The bacterial pathogen Vibrio coralliilyticus has been implicated in severe larval oyster mortality events in U.S. hatcheries. The aims of this study were to determine whether additions of bacteriophages (phages) specific to V. coralliilyticus strain RE98 can lower concentrations of V. coralliilyticus in seawater and consequently enhance survival, growth and metamorphosis of larvae of the Pacific oyster (Crassostrea gigas). Cocktails containing 2 or 3 previously characterized phages in the family Myoviridae (designated 6B, 7B and 11A) were added to cultures of C. gigas larvae together with V. coralliilyticus RE98. Results confirmed that: 1) the addition of a 2-phage cocktail (7B and 11A) significantly reduced concentrations of V. coralliilyticus in autoclaved seawater over a 48-h period in the absence of larvae (p < 0.05); 2) the concentration of a 2-phage cocktail required to significantly reduce mortality of 2-day post fertilization (PF) larvae depended on the initial concentration of V. coralliilyticus added to the seawater; 3) preparation of three-phage cocktails using tangential flow filtration increased the effectiveness of the phages; and 4) a single addition of a cocktail containing 3 phages to 2-day old oyster larval cultures eliminated mortality due to exposure to V. coralliilyticus and significantly improved the proportion of larvae metamorphosing to become spat more than 16 days later. Reductions in V. coralliilyticus-associated larval mortalities by additions of phages were consistent across a range of culture conditions, varying from 1 ml cultures with autoclaved seawater to 10-l cultures supplied with non-sterile, 10-μm filtered seawater.

Coral larval settlement and post-settlement survival facilitated by crustose coralline algae with or without living tissue

Selection of a permanent attachment site of coral larvae can be a critical determinant of recruitment success affecting the structure of coral communities and underpins the ability of coral reef ecosystems to recover from disturbance. Settlement specificity of a threatened coral in Sanya reefs, Acropora millepora, was tested by measuring the larval metamorphosis preferences and post-settlement survival in response to crustose coralline algae (CCA) species Hydrolithon reinboldii and other substrata. In the no-choice experiments, the larvae of A. millepora had similar rates of total metamorphosis with the presence of CCA regardless of the algae tissue being alive or not, and settlement success induced by CCA was higher than by other substrata (tile or glass). In the paired-choice experiments, when CCA was in presence, the coral larvae preferred the surface of the dish and the side of living CCA. In the absence of CCA, total larvae metamorphosis was lower than in the treatments where CCA was present. New recruits of A. millepora had approximately 68% mean survival on all the settlement substrata after 2 weeks maintained in aquaria with flow-through seawater similar to the coral larval sampling site, but with no coral spat survival in the treatments where CCA was absent. However, there were statistical differences between the larvae survival of dead CCA and glass chips treatment and the others where CCA was present. Our results were consistent with the conclusion that some CCA species could facilitate coral larval settlement and post-settlement survivorship, highlighting the importance of substrata selection success for facilitating coral recruitment in the threatened coral reefs.

Dermacentor reticulatus biorhythms in the northern forest-steppe of the Tyumen region

To forecast the number of ticks and take successful measures for decreasing them in population it is necessary to know the features of their phenology in aparticular region. The majority of acarologists pays attention to the features of Ixodes persulcatus activity as they transmitixodic infections. The proved epizootic and epidemiological importance of Dermacentors dictates the necessity of developing and organizing the comprehensive control system against this specie of ticks to prevent diseases. This demand the fullest and comprehensive studying of ecology and phenology features of Dermacentor reticulatus of a particular region. The aim of the research is the detailed studying of bioecology of Dermacentor reticulatus ticks, the most widespread ticks in the Tyumen region. We had monitored over the life cycle features of Dermacentor reticulates in natural biotopes over the 2013 to 2014 period in the subzone of the northern forest-steppe of the Tyumen region. In natural climatic conditions of the specified climatic zone Dermacentor reticulatus are capable to give one generation per a parasitizing season if parasite juvenile forms meet feeders. The whole process of reproduction from egg up to the adult specimen emerge took from 69 to 161 days, and averagely 115±1.99 full days. Metamorphosis of larvae had taken the shortest time period (29.1±2.,0 full days or 25.3% of all cycle time), nymph and imago formations had happened practically for equal periods of 34.5±2.3 and 37.0±5.0 full days respectively. Having studied the regularities of the Dermacentor reticulates life cycles we can prove the emergence and the activity peaks of both juvenile, and adult phases of these ticks activity. That allows to plan actions on controlling these parasites in places of their dwelling.

Effects of microalgae diets and stocking density on larval growth, survival and metamorphosis of dwarf surfclam, Mulinia lateralis

The dwarf surfclam Mulinia lateralis is widely considered a model species in bivalves because of its small size and short generation. An efficient culture system is necessary to continuously obtain enough high quality larvae for genetic research. In the present study, the impacts of microalgae diets and stocking density on larval growth, survival and metamorphosis were investigated to optimize the culture system for M. lateralis. Six of seven tested microalgae were ingested by 2 to 10-day-old larvae, including Isochrysis galbana (IG), Chlorella pyrenoidesa (CP), Nitzschia closterium (NC), Platymonas helgolandica (PH), Chaetoceros muelleri (CM) and Pyramimonas delicatula (PD). The exception was Dunaliella salina (DS), which was not ingested by larvae during the experimental period. This results indicated the larvae could ingest microalgae with larger size as larvae develop. The time needed for digestion gradually decreased as the larvae develop. According to the growth, survival and metamorphosis of larvae after feeding with different microalgae diets, the optimal diets were a single diet of IG for D-shaped larvae, mixed diets of IG + PH at a 1:1 ratio by cell density for umbo larvae and IG + NC + PH at a 1:1:1 ratio by cell density for pediveliger larvae. The better microalgae concentration was 2.4–3.6 × 103 cells mL−1 for D-shaped larvae, 6.0–12 × 103 cells mL−1 for umbo larvae, and 30–40 × 103 cells mL−1 for pediveliger larvae. In addition, the better density of D-shaped larvae was ≤9 larvae mL−1, the density of umbo larvae was ≤7 larvae mL−1, and the density of pediveliger larvae was ≤5 larvae mL−1. In conclusion, ingestion and digestion of microalgae, microalgae combination, microalgae concentration and stocking density significantly affected growth, survival, and metamorphosis of M. lateralis larvae. The optimized conditions will be of great significance for establishing a standard culture system for M. lateralis.

The Starfish Asterina pectinifera: Collection and Maintenance of Adults and Rearing and Metamorphosis of Larvae.

Here we describe methods for (a) collecting starfish during their breeding period; (b) maintaining adults with fully grown gonads in laboratory aquaria; (c) rearing fertilized eggs to brachiolaria larvae, and (d) inducing larvae to metamorphose into juveniles under laboratory conditions. Such protocols should facilitate various analyses of starfish development throughout the entire life cycle of these model organisms.

Proteome of larval metamorphosis induced by epinephrine in the Fujian oyster Crassostrea angulata

BackgroundThe Fujian oyster Crassostrea angulata is an economically important species that has typical settlement and metamorphosis stages. The development of the oyster involves complex morphological and physiological changes, the molecular mechanisms of which are as yet unclear.ResultsIn this study, changes in proteins were investigated during larval settlement and metamorphosis of Crassostrea angulata using epinephrine induction. Protein abundance and identity were characterized using label-free quantitative proteomics, tandem mass spectrometry (MS/ MS), and Mascot methods. The results showed that more than 50% (764 out of 1471) of the quantified proteins were characterized as differentially expressed. Notably, more than two-thirds of the differentially expressed proteins were down-regulated in epinephrine-induced larvae. The results showed that “metabolic process” was closely related to the development of settlement and metamorphosis; 5 × 10− 4 M epinephrine induced direct metamorphosis of larvae and was non-toxic. Calmodulin and MAPK pathways were involved in the regulation of settlement of the oyster. Expression levels of immune-related proteins increased during metamorphosis. Hepatic lectin-like proteins, cadherins, calmodulin, calreticulin, and cytoskeletal proteins were involved in metamorphosis. The nervous system may be remodeled in larval metamorphosis induced by epinephrine. Expression levels of proteins that were enriched in the epinephrine signaling pathway may reflect the developmental stage of the larvae, that may reflect whether or not larvae were directly involved in metamorphosis when the larvae were treated with epinephrine.ConclusionThe study provides insight into proteins that function in energy metabolism, immune responses, settlement and metamorphosis, and shell formation in C. angulata. The results contribute valuable information for further research on larval settlement and metamorphosis.Graphical abstract

Megalopae of the invasive crab Hemigrapsus sanguineus metamorphose in response to marine biofilms from different potential habitats

Habitat characteristics favoring settlement and metamorphosis of larvae can affect the distribution and abundance of benthic marine invertebrates. Less selective responses to habitat cues by settling larvae can lead to broader distributions of species and potentially successful introduction to new geographic locations. This study tested whether marine biofilms, which serve as habitat cues for many invertebrates, enhance settlement and metamorphosis (molting) of megalopae of the invasive Asian shore crab Hemigrapsus sanguineus. Biofilms were allowed to develop on plastic mesh netting deployed in coastal locations with abundant rocky substrate (adult habitat) and estuarine locations with few rocks. Molting rates of laboratory-reared megalopae maintained with biofilm-covered netting were determined. Controls consisted of mesh netting without field-derived biofilms and seawater without netting. Experiments were also conducted with megalopae of a native species of estuarine mud crab, Dyspanopeus sayi, for comparison of responses. Both species molted faster in response to field biofilms regardless of habitat of biofilm development, although the response to biofilms compared to netting without biofilms was stronger for H. sanguineus than D. sayi. The broad response of megalopae of both species to biofilms suggests that positive responses to biofilms and physical structure could be important for successful colonization of crab species in general.

Impact of ocean acidification on growth, onset of competence, and perception of cues for metamorphosis in larvae of the slippershell snail, Crepidula fornicata

Ocean pH has been declining since the start of the Industrial Revolution, and is predicted to continue declining for at least another 200 years. Although the chemical cues that induce larval metamorphosis in marine invertebrates in part determine the distribution and persistence of many coastal marine communities, few studies have examined the effects of ocean acidification on the timing of metamorphic competence or the ability of larval invertebrates to metamorphose in response to environmental cues. Working with larvae of the marine gastropod Crepidula fornicata, we examined the impacts of sudden, short-term (2 h), and prolonged (several weeks) exposure to reduced pH as low as 7.5 on larval survival and growth, the onset of metamorphic competence, and the ability of larvae to perceive inductive cues and metamorphose in their presence. Unexpectedly, although larvae reared at pH 7.5 grew more slowly and took longer to become competent to metamorphose, exposure to acidified conditions did not appreciably impair larval cue perception for metamorphosis.

A contractile injection system stimulates tubeworm metamorphosis by translocating a proteinaceous effector.

The swimming larvae of many marine animals identify a location on the sea floor to undergo metamorphosis based on the presence of specific bacteria. Although this microbe-animal interaction is critical for the life cycles of diverse marine animals, what types of biochemical cues from bacteria that induce metamorphosis has been a mystery. Metamorphosis of larvae of the tubeworm Hydroides elegans is induced by arrays of phage tail-like contractile injection systems, which are released by the bacterium Pseudoalteromonas luteoviolacea. Here we identify the novel effector protein Mif1. By cryo-electron tomography imaging and functional assays, we observe Mif1 as cargo inside the tube lumen of the contractile injection system and show that the mif1 gene is required for inducing metamorphosis. Purified Mif1 is sufficient for triggering metamorphosis when electroporated into tubeworm larvae. Our results indicate that the delivery of protein effectors by contractile injection systems may orchestrate microbe-animal interactions in diverse contexts.

Bioactive Aliphatic Sulfates from Marine Invertebrates.

The occurrence of sulfated steroids and phenolics in marine organisms is quite widespread, being typically reported from Echinoderms. In contrast, alkane and alkene aliphatic sulfates are considerably rarer with examples being reported from a diverse array of organisms including echinoderms, sponges and ascidians. While no ecological roles for these metabolites have been proposed, they do exhibit a diverse array of biological activities including thrombin inhibition; the ability to induce metamorphosis in larvae; antiproliferative, antibacterial and antifungal properties; and metalloproteinase inhibition. Of particular interest and an avenue for future development is the finding of antifouling properties with low or nontoxic effects to the environment. This review focuses on alkyl sulfates and related sulfamates, their structures and biological activities. Spectroscopic and spectrometric techniques that can be used to recognize the presence of sulfate groups are also discussed, data for which will enhance the ability of researchers to recognize this class of chemically- and biologically-interesting marine natural products.

Inducers of settlement and metamorphosis of the shrimp Hippolyte inermis Leach in Posidonia oceanica

Larvae of the caridean shrimp Hippolyte inermis persist in the plankton of the Mediterranean up to about one month. Since they need to reach appropriate coastal areas for their recruitment in seagrass meadows, we hypothesized that leaves of Posidonia oceanica or, alternatively, algae present in their epiphytic biofilms, might be physically recognised as target substrates and trigger larval metamorphosis and settlement. Chemical cues could improve the finding of suitable habitats for settlement. Thus, the effects of leaves of P. oceanica and biofilms of the diatom Cocconeis scutellum parva, seasonally abundant in the leaf epiphytic stratum, were investigated along with the effect of volatile organic compounds (VOCs) extracted from the epiphytic diatom. The physical induction with P. oceanica accelerated larval settlement, stimulating an earlier and faster metamorphosis of larvae. C. scutellum parva produced a weaker effect on settlement; however, diatom’s VOCs had evident influence and accelerated metamorphosis and settlement. We concluded that such chemical cues as the VOCs produced by epiphytic diatoms, reinforce the effect of physical cues for the identification of suitable settlement locations for this shrimp.