Nematocytes Research Articles

CO2‐induced seawater acidification impairs the stinging cells of a jellyfish

AbstractCO2‐induced seawater acidification has been shown to modify predator–prey interactions in many marine taxa. Scyphozoans play an important role in the trophic dynamics of marine ecosystems during their blooms in coastal waters; however, the impacts of seawater acidification on the predation behavior of these animals are poorly understood. Here, we aimed to examine the impact of a decrease in seawater pH on the feeding behavior and growth of ephyrae (juvenile medusae) of the scyphozoan Aurelia coerulea. Combining bulk and single‐cell RNA sequencing approaches, we assessed transcriptomic changes of ephyrae under a laboratory‐based pH 7.6 condition. We found that the feeding rates and growth of ephyrae were significantly inhibited by a decrease in seawater pH. Furthermore, transcriptome analysis showed that a decline in pH significantly reduced the expression of genes related to toxins and nematocyst structure in ephyrae. These findings were further confirmed by single‐cell transcriptomic analyses and revealed that low pH impaired the toxin activity and energy metabolism of stinging cells. The pH recovery experiment indicated that moving ephyrae from seawater with pH 7.6 into seawater with pH 8.1 greatly restored their feeding, growth, and toxin‐related and nematocyst structure–related gene expression. However, exposure to pH 7.6 for 23 d could not recover the decrease in the feeding and growth of ephyrae. Together, these findings indicate that CO2‐induced acidification compromised the stinging cells of A. coerulea ephyrae, with concomitant negative consequences on predation and growth that are likely to alter predator–prey interactions, with consequent effects on community structure and ecosystem.

The evolution of cnidarian stinging cells supports a Precambrian radiation of animal predators.

Cnidarians-the phylum including sea anemones, corals, jellyfish, and hydroids-are one of the oldest groups of predatory animals. Nearly all cnidarians are carnivores that use stinging cells called cnidocytes to ensnare and/or envenom their prey. However, there is considerable diversity in cnidocyte form and function. Tracing the evolutionary history of cnidocytes may therefore provide a proxy for early animal feeding strategies. In this study, we generated a time-calibrated molecular clock of cnidarians and performed ancestral state reconstruction on 12 cnidocyte types to test the hypothesis that the original cnidocyte was involved in prey capture. We conclude that the first cnidarians had only the simplest and least specialized cnidocyte type (the isorhiza) which was just as likely to be used for adhesion and/or defense as the capture of prey. A rapid diversification of specialized cnidocytes occurred through the Ediacaran (~654-574 million years ago), with major subgroups developing unique sets of cnidocytes to match their distinct feeding styles. These results are robust to changes in the molecular clock model, and are consistent with growing evidence for an Ediacaran diversification of animals. Our work also provides insight into the evolution of this complex cell type, suggesting that convergence of forms is rare, with the mastigophore being an interesting counterexample.

Beachside banquet: Ants' appetite for shipwrecked siphonophores

As the importance of both the high seas and gelatinous zooplankton is continuously revealed, it is important to document basic interactions. Physalia are venomous siphonophores, commonly called ‘Man of War’ or ‘Bluebottles’, that use a gas filled float to sail the high seas. Despite being the most conspicuous member of the neustonic ecosystem (the ecosystem at the open ocean's surface), little is known about its life history nor its ecosystem contributions. Herein, two ant species, Solenopsis cf. geminata and Iridomyrmex cf. anceps, were observed foraging on beached colonies of Physalia cf. utriculus in Guam, Micronesia. Ants explored fresh colonies with untriggered stinging cells, yet only disassembled and transported partially dry or degraded colonies. Observations like this improve the understanding of cross-ecosystem dynamics between the coastal and neustonic ecosystem, island trophic structures, and the contribution of gelatinous zooplankton.

Metatranscriptome analysis reveals the putative venom toxin repertoire of the biofouling hydroid Ectopleura larynx

Cnidarians thriving in biofouling communities on aquaculture net pens represent a significant health risk for farmed finfish due to their stinging cells. The toxins coming into contact with the fish, during net cleaning, can adversely affect their behavior, welfare, and survival, with a particularly serious health risk for the gills, causing direct tissue damage such as formation of thrombi and increasing risks of secondary infections. The hydroid Ectopleura larynx is one of the most common fouling organisms in Northern Europe. However, despite its significant economic, environmental, and operational impact on finfish aquaculture, biological information on this species is scarce and its venom composition has never been investigated. In this study, we generated a whole transcriptome of E. larynx, and identified its putative expressed venom toxin proteins (predicted toxin proteins, not functionally characterized) based on in silico transcriptome annotation mining and protein sequence analysis. The results uncovered a broad and diverse repertoire of putative toxin proteins for this hydroid species. Its toxic arsenal appears to include a wide and complex selection of toxin proteins, covering a large panel of potential biological functions that play important roles in envenomation. The putative toxins identified in this species, such as neurotoxins, GTPase toxins, metalloprotease toxins, ion channel impairing toxins, hemorrhagic toxins, serine protease toxins, phospholipase toxins, pore-forming toxins, and multifunction toxins may cause various major deleterious effects in prey, predators, and competitors. These results provide valuable new insights into the venom composition of cnidarians, and venomous marine organisms in general, and offer new opportunities for further research into novel and valuable bioactive molecules for medicine, agronomics and biotechnology.

Single-cell atavism reveals an ancient mechanism of cell type diversification in a sea anemone

Cnidocytes are the explosive stinging cells unique to cnidarians (corals, jellyfish, etc). Specialized for prey capture and defense, cnidocytes comprise a group of over 30 morphologically and functionally distinct cell types. These unusual cells are iconic examples of biological novelty but the developmental mechanisms driving diversity of the stinging apparatus are poorly characterized, making it challenging to understand the evolutionary history of stinging cells. Using CRISPR/Cas9-mediated genome editing in the sea anemone Nematostella vectensis, we show that a single transcription factor (NvSox2) acts as a binary switch between two alternative stinging cell fates. Knockout of NvSox2 causes a transformation of piercing cells into ensnaring cells, which are common in other species of sea anemone but appear to have been silenced in N. vectensis. These results reveal an unusual case of single-cell atavism and expand our understanding of the diversification of cell type identity.

Functional analysis in a model sea anemone reveals phylogenetic complexity and a role in cnidocyte discharge of DEG/ENaC ion channels

Ion channels of the DEG/ENaC family share a similar structure but serve strikingly diverse biological functions, such as Na+ reabsorption, mechanosensing, proton-sensing, chemosensing and cell-cell communication via neuropeptides. This functional diversity raises the question of the ancient function of DEG/ENaCs. Using an extensive phylogenetic analysis across many different animal groups, we found a surprising diversity of DEG/ENaCs already in Cnidaria (corals, sea anemones, hydroids and jellyfish). Using a combination of gene expression analysis, electrophysiological and functional studies combined with pharmacological inhibition as well as genetic knockout in the model cnidarian Nematostella vectensis, we reveal an unanticipated role for a proton-sensitive DEG/ENaC in discharge of N. vectensis cnidocytes, the stinging cells typifying all cnidarians. Our study supports the view that DEG/ENaCs are versatile channels that have been co-opted for diverse functions since their early occurrence in animals and that respond to simple and ancient stimuli, such as omnipresent protons.

FIRST SYMBIOTIC ASSOCIATION BETWEEN HEDERELLOIDS AND RUGOSE CORALS (LATEST SILURIAN OF SAAREMAA, ESTONIA)

ABSTRACTA phoronid-like hederelloid that formed a symbiotic association with the rugosan coral Entelophyllum has been found in the Pridoli Series of Estonia. The skeletons of the hederelloid and rugosan are partially intergrown. The hederelloid apertures are located at the margin of the rugosan calice. The hederelloid lophophore was likely placed between the tentacles of the coral polyp, indicating a positive or at least a neutral co-existence. In extant corals, polyps can be retracted into the calice either during the day or night. If the rugose coral was similar to modern corals in this respect, it may have helped in the co-existence with the hederelloid and allowed feeding at different times. It is possible that the hederelloid soft tissues were protected against smaller predators by the stinging cells of the rugosan tentacles. The history of symbiosis in hederelloids is similar to that of tentaculitoids, in which symbiotic relationships also appeared early in their evolution. To date, Entelophyllum is the only colonial rugosan known to have formed symbiotic associations during the Silurian.

Comparative Study of Morphology and Histology on Papuan Jellyfish Mastigias papua in Kakaban Lake and Sea

Jellyfish are marine invertebrates belonging to the phylum Cnidaria. Mastigias papua is a jellyfish from the Scyphozoa class. This study investigates differences in environmental parameters, morphology, and shape of nematocyte cells using the histological method with (SEM) Scanning Electron Microscopy on M. papua jellyfish Kakaban Lake and Sea. Environmental parameters in Kakaban Lake and Kakaban Sea were measured for salinity, temperature, and pH. The t-test analysis results showed significant differences in environmental parameters in Kakaban Lake and Kakaban Sea (p < 0.05). Body diameter and length of jellyfish tentacles were measured and analyzed using SPSS 16 with a t-test. The t-test analysis showed that for M. papua jellyfish in Kakaban Lake and jellyfish in the Kakaban Sea showed a significant difference in the diameter and length of the body tentacles (p < 0.05). The SEM results of jellyfish in the Kakaban Sea showed that the tentacles of M. papua in the Kakaban Sea had nematocytes consisting of three forms, namely microbasic isorhiza, atrichouz isorhiza, and merotrichous isorhiza. M. papua in Kakaban Lake has nematocyst cells, which comprise of one type, namely Microbasic mastigophoran, where the number of nematocytes is minimal and has a smaller size than the Papuan Mastigias jellyfish that live in the Kakaban Sea. Nemeatocyte cells are stinging cells in jellyfish. SEM results show that the jellyfish in Kakaban Lake cannot sting because the size of the jellyfish tentacles is reduced to smaller, fewer nematocyte cells and different shape nematocytes. Based on the results of this study, it can be concluded that there are differences in environmental parameters, body dimensions, tentacle length, and the size and number of nematocytes between M. papua jellyfish in Dunau and in the Kakaban Sea.

Extraction and characterization of sea anemones compound and its Anti bacterial and hemolytic studies

Seas assets that give us a variety of characteristic items to control bacterial, contagious and viral ailment and mostly utilized for malignancy chemotherapy practically from spineless creatures, for example, bryozoans, wipes, delicate corals, coelenterates, ocean fans, ocean bunnies, molluscs and echinoderms. In the previous 30 - 40 years, marine plants and creatures have been the focal point of overall endeavours to characterize the regular results of the marine condition. Numerous marine characteristic items have been effectively exceptional to the last phases of clinical preliminaries, including dolastatin-10, a group of peptides disengaged from Indian ocean rabbit, Dollabella auricularia. Ecteinascidin-743 from mangrove tunicate Ecteinascidia turbinata, Didemnins was isolated from Caribbean tunicate Trididemnum solidum and Conopeptides from cone snails (Conus sp.), and a developing number of up-and-comers have been chosen as promising leads for expanded pre-clinical appraisals. Sea anemones possess numerous tentacles containing stinging cells or cnidocytes. The stinging cells are equipped with small organelles known as nematocysts. The two species of sea anemones namely, Heteractis magnificaandStichodactyla haddoni, were collected from Mandapam coastal waters of Ramanathapuram district, Tamilnadu, India. The Nematocyst was collected and centrifuged, and the supernatant was lyophilized and stored for further analysis. The amount of protein from Heteractis Magnifica and Stichodactyla haddoni was estimated. The crude extract has shown haemolytic activity on chicken blood and goat blood. In the antibacterial activity of the sea anemone against six bacterial strains Staphylococcus aureus, Salmonella typhii, Salmonella paratyphii, Klebsiella pneumonia, Vibrio cholerae, Pseudomonas aeruginosa. Antibacterial activity of H. Magnifica and S.haddoni was measured as the radius of the zone of inhibition.

A tentacle for every occasion: comparing the hunting tentacles and sweeper tentacles, used for territorial competition, in the coral Galaxea fascicularis

BackgroundCoral reefs are among the most diverse, complex and densely populated marine ecosystems. To survive, morphologically simple and sessile cnidarians have developed mechanisms to catch prey, deter predators and compete with adjacent corals for space, yet the mechanisms underlying these functions are largely unknown. Here, we characterize the histology, toxic activity and gene expression patterns in two different types of tentacles from the scleractinian coral Galaxea fascilcularis – catch tentacles (CTs), used to catch prey and deter predators, and sweeper tentacles (STs), specialized tentacles used for territorial aggression.ResultsSTs exhibit more mucocytes and higher expression of mucin genes than CTs, and lack the ectodermal cilia used to deliver food to the mouth and remove debris. STs and CTs also express different sensory rhodopsin-like g-protein coupled receptors, suggesting they may employ different sensory pathways. Each tentacle type has a different complement of stinging cells (nematocytes), and the expression in the two tentacles of genes encoding structural nematocyte proteins suggests the stinging cells develop within the tentacles. CTs have higher neurotoxicity to blowfly larvae and hemolytic activity compared to the STs, consistent with a role in prey capture. In contrast, STs have higher phospholipase A2 activity, which we speculate may have a role in inducing tissue damage during territorial aggression. The expression of genes encoding cytolytic toxins (actinoporins) and phospholipases also differs between the tentacle types.ConclusionsThese results show that the same organism utilizes two distinct tentacle types, each equipped with a different venom apparatus and toxin composition, for prey capture and defense and for territorial aggression.

A molecular filter for the cnidarian stinging response.

All animals detect and integrate diverse environmental signals to mediate behavior. Cnidarians, including jellyfish and sea anemones, both detect and capture prey using stinging cells called nematocytes which fire a venom-covered barb via an unknown triggering mechanism. Here, we show that nematocytes from Nematostella vectensis use a specialized voltage-gated calcium channel (nCaV) to distinguish salient sensory cues and control the explosive discharge response. Adaptations in nCaV confer unusually sensitive, voltage-dependent inactivation to inhibit responses to non-prey signals, such as mechanical water turbulence. Prey-derived chemosensory signals are synaptically transmitted to acutely relieve nCaV inactivation, enabling mechanosensitive-triggered predatory attack. These findings reveal a molecular basis for the cnidarian stinging response and highlight general principles by which single proteins integrate diverse signals to elicit discrete animal behaviors.

Predatory protists.

The vast majority of eukaryotic life is made up of single cells commonly referred to as protists. In this primer, Leander provides an introduction to predatory protists - cells that eat other cells. This lifestyle, in particular the use of phagocytosis, makes endosymbiosis possible and enabled the evolution of complex cells.

Where in the World Did You Get That Rash?

1. Panteha Eshtiaghi, HBSc* 2. Miriam Weinstein, MD, FRCPC† 1. *Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada 2. †Hospital for Sick Children, Toronto, Ontario, Canada * Abbreviations: ACD: : allergic contact dermatitis CD: : cercarial dermatitis CL: : cutaneous leishmaniasis CLM: : cutaneous larva migrans DF: : dengue fever HFMD: : hand, foot, and mouth disease HSV: : herpes simplex virus KD: : Kawasaki disease PCR: : polymerase chain reaction PR: : pityriasis rosea RT-PCR: : reverse transcriptase polymerase chain reaction The challenge to diagnose cutaneous eruptions and lesions in patients who have spent time in foreign countries is increasingly common. With the advent of increased global travel, foreign adoptions, immigration, and refugee seekers, rashes that were once relegated to the realm of the exotic and likely to show up in a tropical diseases clinic may now present to a general pediatrician. Furthermore, the pediatric traveler is at increased risk for dermatoses. (1) It behooves the practitioner to be aware of these skin findings, to be able to recognize them and distinguish them from other skin conditions. After completing this article, readers should be able to: 1. Identify and classify rashes by main morphologic patterns. 2. Develop a broad differential diagnosis and diagnostic approach for a rash in a returned pediatric traveler based on initial morphology, history, epidemiology, and other clinical features. 3. Consider both infectious and noninfectious causes of skin disorders presenting in a patient with a travel history. 4. Outline the basic investigations and principles of management for travel-acquired and non–travel-acquired dermatologic illnesses. 5. Discuss …

InVivo Bioengineering of Fluorescent Conductive Protein-Dye Microfibers.

SummaryEngineering protein-based biomaterials is extremely challenging in bioelectronics, medicine, and materials science, as mechanical, electrical, and optical properties need to be merged to biocompatibility and resistance to biodegradation. An effective strategy is the engineering of physiological processes in situ, by addition of new properties to endogenous components. Here we show that a green fluorescent semiconducting thiophene dye, DTTO, promotes, in vivo, the biogenesis of fluorescent conductive protein microfibers via metabolic pathways. By challenging the simple freshwater polyp Hydra vulgaris with DTTO, we demonstrate the stable incorporation of the dye into supramolecular protein-dye co-assembled microfibers without signs of toxicity. An integrated multilevel analysis including morphological, optical, spectroscopical, and electrical characterization shows electrical conductivity of biofibers, opening the door to new opportunities for augmenting electronic functionalities within living tissue, which may be exploited for the regulation of cell and animal physiology, or in pathological contexts to enhance bioelectrical signaling.

Mechanisms of cnidocyte development in the moon jellyfish Aurelia.

Stinging cells called cnidocytes are a defining trait of the cnidarians (sea anemones, corals, jellyfish, and their relatives). In hydrozoan cnidarians such as Hydra, cnidocytes develop from interstitial stem cells set aside in the ectoderm. It is less clear how cnidocytes develop outside the Hydrozoa, as other cnidarians appear to lack interstitial stem cells. We addressed this question by studying cnidogenesis in the moon jellyfish (Aurelia) through the visualization of minicollagen-a protein associated with cnidocyte development-as well as transmission electron microscopy. We discovered that developing cnidoblasts are rare or absent in feeding structures rich in mature cnidocytes, such as tentacles and lappets. Using transmission electron microscopy, we determined that the progenitors of cnidocytes have traits consistent with epitheliomuscular cells. Our data suggests a dynamic where cnidocytes develop at high concentrations in the epithelium of more proximal regions, and subsequently migrate to more distal regions where they exhibit high usage and turnover. Similar to some anthozoans, cnidocytes in Aurelia do not appear to be generated by interstitial stem cells; instead, epitheliomuscular cells appear to be the progenitor cell type. This observation polarizes the evolution of cnidogenesis, and raises the question of how interstitial stem cells came to regulate cnidogenesis in hydrozoans.

Prevailing conditions influence anemone duels

If you had to put together a list of your top 10 knock-out heavy-weights, I suspect that sea anemones wouldn't be high up. But when Sarah Lane from the University of Plymouth describes sea anemones slugging it out, it is clear that the outcomes are no less cataclysmic. Elongating their bodies and inflating blue stinging blobs – known as acrorhagi – at the base of their tentacles, the combatants slam their bodies down on top of each other. In the process, they rip off the acrorhagi as they drag them along their opponent's flank, depositing toxin-laden stinging cells in their opponent's skin until the vanquished adversary closes up or makes off. According to Lane, the outcome of confrontations is often assumed to depend on the size and strength of the opponents, but she and Mark Briffa – also from the University of Plymouth – wondered whether the local prevailing conditions could also influence the result. ‘The environment is rarely stable’, says Lane, pointing out that sea anemones are often prey to exposure and rising temperatures, both of which could impact their performance when duelling over real estate. ‘We wanted to understand how such environmental variation might affect how fights play out in the wild’, says Lane.After settling sea anemones (Actinia equina) that had been collected from rock pools on a Cornish beach into their Plymouth laboratory home, Lane transferred half of the animals into water with low oxygen levels. ‘This [oxygen] is a factor that is known to vary considerably within rock pools when the tide is out’, says Lane, adding that the availability can affect the anemones’ strength and stamina. Then, she riled pairs of sea anemones by nestling them together and gave them something to fight over: flowing water. ‘Anemones are scavengers and use their feeding tentacles to catch food passing by in the water column; thus, anemones value flowing water over still water’, she says. Pitting ‘breathless’ anemones from the deoxygenated water against well-aerated animals, as well as coupling pairs of aerated anemones and pairs of oxygen-deprived (hypoxic) anemones, Lane staged some prize fights when the water was flowing and others when it was still – and there was less at stake – before recording which fighter had been overcome at the end of a round.Comparing the anemones’ prowess, it was clear to Lane and Briffa that the environment affected the animals’ performance dramatically, with the well-aerated anemones out-performing their oxygen­-deprived sparring partners, especially when they had a healthy current to duel over. However, Lane admits that she was surprised that despite the lack of oxygen, the hypoxic anemones fought more doggedly than their well-aerated opponents; they were particularly brutal, inflicting more wounds on their adversary, when matched against an equally hypoxic competitor.So, the environmental conditions that a contestant experiences can affect their performance in combat, ‘by altering an individual's ability to fight and its motivation’, says Lane. And she is eager to stage more anemone fisticuffs, only this time between anemones from different locations on the beach, to find out how much of an impact the real world has in practice on sea anemone boxing bouts.

Before platelets: the production of platelet-activating factor during growth and stress in a basal marine organism.

Corals and humans represent two extremely disparate metazoan lineages and are therefore useful for comparative evolutionary studies. Two lipid-based molecules that are central to human immunity, platelet-activating factor (PAF) and Lyso-PAF were recently identified in scleractinian corals. To identify processes in corals that involve these molecules, PAF and Lyso-PAF biosynthesis was quantified in conditions known to stimulate PAF production in mammals (tissue growth and exposure to elevated levels of ultraviolet light) and in conditions unique to corals (competing with neighbouring colonies over benthic space). Similar to observations in mammals, PAF production was higher in regions of active tissue growth and increased when corals were exposed to elevated levels of ultraviolet light. PAF production also increased when corals were attacked by the stinging cells of a neighbouring colony, though only the attacked coral exhibited an increase in PAF. This reaction was observed in adjacent areas of the colony, indicating that this response is coordinated across multiple polyps including those not directly subject to the stress. PAF and Lyso-PAF are involved in coral stress responses that are both shared with mammals and unique to the ecology of cnidarians.

Phylogenomics provides a robust topology of the major cnidarian lineages and insights on the origins of key organismal traits

BackgroundThe phylogeny of Cnidaria has been a source of debate for decades, during which nearly all-possible relationships among the major lineages have been proposed. The ecological success of Cnidaria is predicated on several fascinating organismal innovations including stinging cells, symbiosis, colonial body plans and elaborate life histories. However, understanding the origins and subsequent diversification of these traits remains difficult due to persistent uncertainty surrounding the evolutionary relationships within Cnidaria. While recent phylogenomic studies have advanced our knowledge of the cnidarian tree of life, no analysis to date has included genome-scale data for each major cnidarian lineage.ResultsHere we describe a well-supported hypothesis for cnidarian phylogeny based on phylogenomic analyses of new and existing genome-scale data that includes representatives of all cnidarian classes. Our results are robust to alternative modes of phylogenetic estimation and phylogenomic dataset construction. We show that two popular phylogenomic matrix construction pipelines yield profoundly different datasets, both in the identities and in the functional classes of the loci they include, but resolve the same topology. We then leverage our phylogenetic resolution of Cnidaria to understand the character histories of several critical organismal traits. Ancestral state reconstruction analyses based on our phylogeny establish several notable organismal transitions in the evolutionary history of Cnidaria and depict the ancestral cnidarian as a solitary, non-symbiotic polyp that lacked a medusa stage. In addition, Bayes factor tests strongly suggest that symbiosis has evolved multiple times independently across the cnidarian radiation.ConclusionsCnidaria have experienced more than 600 million years of independent evolution and in the process generated an array of organismal innovations. Our results add significant clarification on the cnidarian tree of life and the histories of some of these innovations. Further, we confirm the existence of Acraspeda (staurozoans plus scyphozoans and cubozoans), thus reviving an evolutionary hypothesis put forward more than a century ago.

About the Cover

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCoverThe cover image is of the brilliantly colored, adult nudibranch Flabellina iodinea. The purple-blue body contrasts richly with the bright orange dorsal extensions, termed cerata. This coloration, coupled with its rhythmically twisting swimming motion, has earned this species the nickname “Spanish shawl.”The shell-less F. iodinea feeds preferentially on the cnidarian hydroid Eudendrium ramosum, from which it obtains the carotenoid astaxanthin that gives the animal its purple, orange, and red pigmented coloration as well as its stinging cells, termed nematocysts. Flabellina iodinea sequesters nematocysts in specialized cells of the cerata for defense. The conspicuously contrasting color pattern of the animal functions to attract would-be predators to the location of these stinging nematocysts and away from the main body, thereby discouraging further predation by those that have learned their lesson!On pages 116–129, S. J. Dearden, A. Ghoshal, D. G. DeMartini, and D. E. Morse show that the pigmented optical appearance of F. iodinea is augmented by dynamically sparkling, brightly reflective stacks of tiny crystals that tumble within vesicles in cells located throughout the epidermis. This tumbling exposes different faces of the small reflective crystals to produce their silvery sparkling appearance. Light and electron microscopy revealed the location and behavior of these sparkling crystals in situ, while purification, thin-layer chromatography, and electron diffraction were used to characterize their crystallographic and molecular structure—composed of the organic metabolites guanine and hypoxanthine. Although similar stacks of such crystals have been found to provide reflectivity in tissues of chameleons, spiders, fish, and other nudibranchs, this is the first discovery of dynamically sparkling, tumbling, crystalline reflectors in any tissue.Credits: Photo, Larry Friesen, Santa Barbara City College. Cover design, Jeannie Harrell, University of Chicago Press. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 234, Number 2April 2018 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/698953 © 2018 by The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.

Consequences of Stinging Plankton Blooms on Finfish Mariculture in the Mediterranean Sea

In recent years, caged finfish mariculture across European seas suffered production losses by severe fish mortality, following episodic outbreaks of invertebrate cnidarian stingers. Due to their stinging cells and injectable venoms, medusozoan jellyfish or drifting propagules of polyp colonies at high density may impair caged fish health through toxic effects on vulnerable tissues of gills and skin, and related secondary bacterial infections. Gill disorders in European sea bass (Dicentrarchus labrax) fish farms along the Spanish Mediterranean coast are commonly reported, but regular monitoring of the frequency of cnidarian outbreaks and their potential impacts on caged fish is still poorly enforced. In this study, two sea bass mariculture farms in Southern Spain (Malaga; Almeria) were monitored biweekly for zooplankton, phytoplankton and fish gills condition, over 13 or 30 months for the Malaga and Almeria facilities respectively, within the period 2012 – 2014. Significant, direct correlations were found among low water temperature, recorded fish mortalities, and high abundances of planktonic cnidarians, particularly of the hydrozoan siphonophores Muggiaea atlantica and M. kochii, and the larval stage of Ectopleura larynx, a common member of cage biofouling communities. A significant relationship between cnidarian densities and the quantitative scoring of gill pathology was also observed. In addition, high densities of long-bristled planktonic diatoms (Chaetoceros spp.) coincided with a major fish mortality event (April 2012, Almeria farm). Standardised monitoring of plankton dynamics and composition may help in promoting response capacities of Mediterranean mariculture managers to fish health challenges (such as stinging plankton blooms) by a) improving diagnostic tools and preventative countermeasures and b) supporting the development of science-based spatial planning and sustainable growth of coastal mariculture.