pubmed

Calaxin establishes basal body orientation and coordinates movement of monocilia in sea urchin embryos.

Latest Publications - Thu, 07/18/2019 - 20:53
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Calaxin establishes basal body orientation and coordinates movement of monocilia in sea urchin embryos.

Sci Rep. 2017 09 07;7(1):10751

Authors: Mizuno K, Shiba K, Yaguchi J, Shibata D, Yaguchi S, Prulière G, Chenevert J, Inaba K

Abstract
Through their coordinated alignment and beating, motile cilia generate directional fluid flow and organismal movement. While the mechanisms used by multiciliated epithelial tissues to achieve this coordination have been widely studied, much less is known about regulation of monociliated tissues such as those found in the vertebrate node and swimming planktonic larvae. Here, we show that a calcium sensor protein associated with outer arm dynein, calaxin, is a critical regulator for the coordinated movements of monocilia. Knockdown of calaxin gene in sea urchin embryos results in uncoordinated ciliary beating and defective directional movement of the embryos, but no apparent abnormality in axoneme ultrastructure. Examination of the beating cycle of individual calaxin-deficient cilia revealed a marked effect on the waveform and spatial range of ciliary bending. These findings indicate that calaxin-mediated regulation of ciliary beating is responsible for proper basal body orientation and ciliary alignment in fields of monociliated cells.

PMID: 28883641 [PubMed - indexed for MEDLINE]

Categories: pubmed

Analysis of sea star larval regeneration reveals conserved processes of whole-body regeneration across the metazoa.

Latest Publications - Wed, 07/10/2019 - 20:34
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Analysis of sea star larval regeneration reveals conserved processes of whole-body regeneration across the metazoa.

BMC Biol. 2019 02 22;17(1):16

Authors: Cary GA, Wolff A, Zueva O, Pattinato J, Hinman VF

Abstract
BACKGROUND: Metazoan lineages exhibit a wide range of regenerative capabilities that vary among developmental stage and tissue type. The most robust regenerative abilities are apparent in the phyla Cnidaria, Platyhelminthes, and Echinodermata, whose members are capable of whole-body regeneration (WBR). This phenomenon has been well characterized in planarian and hydra models, but the molecular mechanisms of WBR are less established within echinoderms, or any other deuterostome system. Thus, it is not clear to what degree aspects of this regenerative ability are shared among metazoa.
RESULTS: We characterize regeneration in the larval stage of the Bat Star (Patiria miniata). Following bisection along the anterior-posterior axis, larvae progress through phases of wound healing and re-proportioning of larval tissues. The overall number of proliferating cells is reduced following bisection, and we find evidence for a re-deployment of genes with known roles in embryonic axial patterning. Following axial respecification, we observe a significant localization of proliferating cells to the wound region. Analyses of transcriptome data highlight the molecular signatures of functions that are common to regeneration, including specific signaling pathways and cell cycle controls. Notably, we find evidence for temporal similarities among orthologous genes involved in regeneration from published Platyhelminth and Cnidarian regeneration datasets.
CONCLUSIONS: These analyses show that sea star larval regeneration includes phases of wound response, axis respecification, and wound-proximal proliferation. Commonalities of the overall process of regeneration, as well as gene usage between this deuterostome and other species with divergent evolutionary origins reveal a deep similarity of whole-body regeneration among the metazoa.

PMID: 30795750 [PubMed - indexed for MEDLINE]

Categories: pubmed

High frequency ultrasound imaging and simulations of sea urchin oocytes.

Latest Publications - Wed, 07/10/2019 - 20:34
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High frequency ultrasound imaging and simulations of sea urchin oocytes.

J Acoust Soc Am. 2017 07;142(1):268

Authors: Strohm EM, Wirtzfeld LA, Czarnota GJ, Kolios MC

Abstract
High frequency ultrasound backscatter signals from sea urchin oocytes were measured using a 40 MHz transducer and compared to numerical simulations. The Faran scattering model was used to calculate the ultrasound scattered from single oocytes in suspension. The urchin oocytes are non-nucleated with uniform size and biomechanical properties; the backscatter from each cell is similar and easy to simulate, unlike typical nucleated mammalian cells. The time domain signal measured from single oocytes in suspension showed two distinct peaks, and the power spectrum was periodic with minima spaced approximately 10 MHz apart. Good agreement to the Faran scattering model was observed. Measurements from tightly packed oocyte cell pellets showed similar periodic features in the power spectra, which was a result of the uniform size and consistent biomechanical properties of the cells. Numerical simulations that calculated the ultrasound scattered from individual oocytes within a three dimensional volume showed good agreement to the measured signals and B-scan images. A cepstral analysis of the signal was used to calculate the size of the cells, which was 78.7 μm (measured) and 81.4 μm (simulated). This work supports the single scattering approximation, where ultrasound is discretely scattered from single cells within a bulk homogeneous sample, and that multiple scattering has a negligible effect. This technique can be applied towards understanding the complex scattering behaviour from heterogeneous tissues.

PMID: 28764480 [PubMed - indexed for MEDLINE]

Categories: pubmed

A SLC4 family bicarbonate transporter is critical for intracellular pH regulation and biomineralization in sea urchin embryos.

Latest Publications - Sat, 07/06/2019 - 20:27
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A SLC4 family bicarbonate transporter is critical for intracellular pH regulation and biomineralization in sea urchin embryos.

Elife. 2018 05 01;7:

Authors: Hu MY, Yan JJ, Petersen I, Himmerkus N, Bleich M, Stumpp M

Abstract
Efficient pH regulation is a fundamental requisite of all calcifying systems in animals and plants but with the underlying pH regulatory mechanisms remaining largely unknown. Using the sea urchin larva, this work identified the SLC4 HCO3- transporter family member SpSlc4a10 to be critically involved in the formation of an elaborate calcitic endoskeleton. SpSlc4a10 is specifically expressed by calcifying primary mesenchyme cells with peak expression during de novo formation of the skeleton. Knock-down of SpSlc4a10 led to pH regulatory defects accompanied by decreased calcification rates and skeleton deformations. Reductions in seawater pH, resembling ocean acidification scenarios, led to an increase in SpSlc4a10 expression suggesting a compensatory mechanism in place to maintain calcification rates. We propose a first pH regulatory and HCO3- concentrating mechanism that is fundamentally linked to the biological precipitation of CaCO3. This knowledge will help understanding biomineralization strategies in animals and their interaction with a changing environment.

PMID: 29714685 [PubMed - indexed for MEDLINE]

Categories: pubmed

The unique biomineralization transcriptome and proteome of Lytechinus variegatus teeth.

Latest Publications - Fri, 06/21/2019 - 19:34
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The unique biomineralization transcriptome and proteome of Lytechinus variegatus teeth.

Connect Tissue Res. 2018 12;59(sup1):20-29

Authors: Alvares K, DeHart CJ, Thomas PM, Kelleher NL, Veis A

Abstract
BACKGROUND: Matrix-regulated biomineralization involves the specific nucleation and growth of mineral phases within or upon preformed structured organic matrices. We hypothesized that there might be a general mechanism whereby anionic, phosphorylated mineral ion-binding proteins assist in specifically locating the mineral ions with respect to the mineralizing structural organic matrix. Here we extended these studies to invertebrate mineralization in Lytechinus variegatus (Lv) teeth.
MATERIALS AND METHODS: The tooth proteins were extracted and the phosphoproteins occluded in the mineral were enriched by passage through a ProQ Diamond phosphoprotein enrichment column, and subjected to MS/MS analysis. A Lv RNA-seq derived transcriptome database was generated. The MS/MS data found 25 proteins previously classified as "Predicted uncharacterized proteins" and many of the spicule matrix proteins. As these 25 proteins were also identified with the transcriptome analysis, and were thus no longer "hypothetical" but real proteins in the Lv tooth. Each protein was analyzed for the presence of a signal peptide, an acidic pI≤4, and the ability to be phosphorylated.
RESULTS: Four new Lv tooth specific Pro-Ala-rich proteins were found, representing a new class of proteins.
CONCLUSION: The tooth is different from the spicules and other urchin skeletal elements in that only the tooth contains both "high" and "very high" magnesium calcite, [Ca(1-X) Mg(X) CO3], where X is the mole fraction of Mg. We speculate that our newly discovered proline-alanine rich proteins, also containing sequences of acidic amino acids, may be involved in the formation of high magnesium and very high magnesium calcite.

PMID: 29745816 [PubMed - indexed for MEDLINE]

Categories: pubmed

Temnopleurus as an emerging echinoderm model.

Latest Publications - Thu, 06/20/2019 - 19:34
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Temnopleurus as an emerging echinoderm model.

Methods Cell Biol. 2019;150:71-79

Authors: Yaguchi S

Abstract
Sea urchins have played important roles in cell and developmental biology. They have the potential to be even more useful as models if the ability to create transgenic animals and maintain genetic lines are developed. Here, I describe the methods to produce next-generation lines using a newly introduced sea urchin model, Temnopleurus reevesii, in the laboratory. The embryos of T. reevesii have wide range of temperature tolerance between 15°C to 30°C and have high transparency, which can be a strong point in live-imaging and fluorescent immunohistochemistry. I describe how to grow and culture the embryos/larvae/juveniles/adults of T. reevesii to address the challenge of establishing inbred strains followed by introducing genetics into this species in the future.

PMID: 30777191 [PubMed - indexed for MEDLINE]

Categories: pubmed

Exploring the sea urchin genome with undergraduates using bioinformatic tools.

Latest Publications - Thu, 06/20/2019 - 19:34
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Exploring the sea urchin genome with undergraduates using bioinformatic tools.

Methods Cell Biol. 2019;150:449-469

Authors: Romano L, Byrum C, Lee PY, Morris RL

Abstract
It is important to provide undergraduate students with research experiences so that they obtain essential problem-solving skills and come to appreciate the process of science whether or not they pursue graduate study. However, such experiences can be difficult to achieve at a primarily undergraduate institution where time and resources are limited. One strategy is to incorporate research into the laboratory component of courses, with students having input into the specific topic being investigated. In this chapter, we present a series of activities that can be brought together as a semester or year-long project after students select a gene with the potential to be analyzed in a novel species of echinoderm. Students become acquainted with important databases, software programs, and online tools as they clone their gene, confirm its identity through alignment with homologous sequences, and characterize its expression through both qPCR and WMISH. We provide streamlined protocols that allow the work to be accomplished in an efficient manner, and conclude with ideas for assignments that can be completed in parallel to improve students' writing and oral communication skills in preparation for any career.

PMID: 30777188 [PubMed - indexed for MEDLINE]

Categories: pubmed

A teaching laboratory on the activation of xenobiotic transporters at fertilization of sea urchins.

Latest Publications - Thu, 06/20/2019 - 19:34
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A teaching laboratory on the activation of xenobiotic transporters at fertilization of sea urchins.

Methods Cell Biol. 2019;150:429-447

Authors: Shipp LE, Hill RZ, Hamdoun A

Abstract
Sea urchin gametes have been historically used to demonstrate fertilization and early development in student laboratories. Large amounts of egg and sperm are easily acquired, and the conspicuous changes in egg surface morphology, indicative of sperm-egg fusion and egg activation, are readily observed in the classroom. However, less often incorporated into teaching labs are exercises that demonstrate the dramatic metabolic changes that accompany egg activation. One example is the massive up-regulation of various essential transport activities in the embryo's plasma membrane, including xenobiotic transporter activity. Here we outline a laboratory that incorporates this concept into a teaching lab, capitalizing on the magnitude and uniformity of the xenobiotic transporter activation event in certain species of sea urchins. The introduction of this chapter provides background information for the instructor, and the remainder serves as a laboratory manual for students. The experiments detailed within the manual can be completed in a total of 4-8h spread over one or two lab periods. The lab manual guides students through a modified version of the United States Environmental Protection Agency (EPA) toxicity test, a novel undergraduate-level laboratory on xenobiotic transporters, and analysis of microscope data using ImageJ. We have found this lab to be of interest to a wide range of biology and environmental science undergraduates, and effective in teaching underlying concepts in developmental biology, physiology and toxicology.

PMID: 30777187 [PubMed - indexed for MEDLINE]

Categories: pubmed

Methods for collection, handling, and analysis of sea urchin coelomocytes.

Latest Publications - Thu, 06/20/2019 - 19:34
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Methods for collection, handling, and analysis of sea urchin coelomocytes.

Methods Cell Biol. 2019;150:357-389

Authors: Smith LC, Hawley TS, Henson JH, Majeske AJ, Oren M, Rosental B

Abstract
Sea urchin coelomocytes can be collected in large numbers from adult sea urchins of the species, Strongylocentrotus purpuratus, which typically has 12-40mL of coelomic fluid. Coelomocytes are used for analysis of immune reactions and immune gene expression in addition to basic functions of cells, in particular for understanding structure and modifications of the cytoskeleton in phagocytes. The methods described here include coelomocyte isolation, blocking the clotting reaction, establishing and maintaining primary cultures, separation of different types of coelomocytes into fractions, processing live coelomocytes for light microscopy, fixation and staining for light and electron microscopy, analysis of coelomocyte populations by flow cytometry, and sorting single cells for more detailed follow-up analyses including transcriptomics or genomic characteristics. These methods are provided to make working with coelomocytes accessible to researchers who are unfamiliar with these cells and perhaps to aid others who have worked extensively with invertebrate cells.

PMID: 30777184 [PubMed - indexed for MEDLINE]

Categories: pubmed

Procuring animals and culturing of eggs and embryos.

Latest Publications - Thu, 06/20/2019 - 19:34
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Procuring animals and culturing of eggs and embryos.

Methods Cell Biol. 2019;150:3-46

Authors: Adams NL, Heyland A, Rice LL, Foltz KR

Abstract
Echinoderms and especially echinoids have a rich history as model systems for the study of oogenesis, fertilization, and early embryogenesis. The ease of collecting and maintaining adults, as well as in obtaining gametes and culturing large quantities of synchronous embryos, is complemented by the ability to do biochemistry, reverse genetics, embryo manipulations and study gene regulatory networks. The diversity of species and developmental modes as well as unparalleled transparency in early developmental stages also makes echinoderms an excellent system in which to study evolutionary aspects of developmental biology. This chapter provides a practical guide to experimental methods for procuring adults and gametes, achieving synchronous in vitro fertilization, and culturing embryos through early larval stages for several echinoderm species representing four classes (Echinoidea, Asteroidea, Ophiuroidea, and Holothuroidea). We provide specific examples of protocols for obtaining adults and gametes and for culturing embryos of a selected number of species for experimental analysis of their development. The species were chosen to provide breadth across the phylum Echinodermata, as well as to provide practical guidelines for handling some of the more commonly studied species. For each species, we highlight specific advantages, and special note is made of key issues to consider when handling adults, collecting gametes, or setting and maintaining embryo cultures. Finally, information regarding interspecific crosses is provided.

PMID: 30777182 [PubMed - indexed for MEDLINE]

Categories: pubmed

Methods to label, isolate, and image sea urchin small micromeres, the primordial germ cells (PGCs).

Latest Publications - Thu, 06/20/2019 - 19:34
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Methods to label, isolate, and image sea urchin small micromeres, the primordial germ cells (PGCs).

Methods Cell Biol. 2019;150:269-292

Authors: Campanale JP, Hamdoun A, Wessel GM, Su YH, Oulhen N

Abstract
Small micromeres of the sea urchin are believed to be primordial germ cells (PGCs), fated to give rise to sperm or eggs in the adult. Sea urchin PGCs are formed at the fifth cleavage, undergo one additional division during blastulation, and migrate to the coelomic pouches of the pluteus larva. The goal of this chapter is to detail classical and modern techniques used to analyze primordial germ cell specification, gene expression programs, and cell behaviors in fixed and live embryos. The transparency of the sea urchin embryo enables both live imaging techniques and in situ RNA hybridization and immunolabeling for a detailed molecular characterization of these cells. Four approaches are presented to highlight small micromeres with fluorescent molecules for analysis by live and fixed cell microscopy: (1) small molecule dye accumulation during cleavage and blastula stages, (2) primordial germ cell targeted RNA expression using the Nanos untranslated regions, (3) fusing genes of interest with a Nanos2 targeting peptide, and (4) EdU and BrdU labeling. Applications of the live labeling techniques are discussed, including sorting by fluorescence-activated cell sorting for transcriptomic analysis, and, methods to image small micromere behavior in whole and dissociated embryos by live confocal microscopy. Finally, summary table of antibody and RNA probes as well as small molecule dyes to label small micromeres at a variety of developmental stages is provided.

PMID: 30777180 [PubMed - indexed for MEDLINE]

Categories: pubmed

Visualizing egg and embryonic polarity.

Latest Publications - Thu, 06/20/2019 - 19:34
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Visualizing egg and embryonic polarity.

Methods Cell Biol. 2019;150:251-268

Authors: Smith LT, Wikramanayake AH

Abstract
During development metazoan embryos have to establish the molecular coordinates for elaboration of the embryonic body plan. Typically, bilaterian (bilaterally symmetric animals) embryos establish anterior-posterior (AP) and dorsal-ventral (DV) axes, and in most cases the AP axis is established first. For over a century it has been known that formation of the AP axis is strongly influenced by the primary axis of the egg, the animal-vegetal (AV) axis. The molecular basis for how the AV axis influences AP polarity remains poorly understood, but sea urchins have proven to be important for elucidating the molecular basis for this process. In fact, it is the first model system where a critical role for Wnt signaling in specification and patterning the AV and AP axis was first established. One current area of research is focused on identifying the maternal factors that regulate localized activation of Wnt/β-catenin signaling at the vegetal pole during development. An essential tool for this work is the means to identify the AV polarity in oocytes and eggs. This permits investigation into how polarity is established and allows development of experimental strategies to identify maternal factors that contribute to and control axial polarity. This chapter provides protocols to accomplish this in sea urchin eggs and early embryos. We describe simple methods to visualize polarity including direct observation of eggs and oocytes, using a microscope for overt morphological signs of polarity, and more extensive methods involving localization of known factors indicative of inherent embryonic polarity, such as the upstream regulators of the Wnt/β-catenin pathway.

PMID: 30777179 [PubMed - indexed for MEDLINE]

Categories: pubmed

Sea urchin embryonic cilia.

Latest Publications - Thu, 06/20/2019 - 19:34
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Sea urchin embryonic cilia.

Methods Cell Biol. 2019;150:235-250

Authors: Morris RL, Vacquier VD

Abstract
Cilia are exceptionally complicated subcellular structures involved in swimming and developmental signaling, including induction of left-right asymmetry in larval stages. We summarize the history of research on sea urchin embryonic cilia. The high salt method to isolate cilia is presented first; methods to block cilia formation and to lengthen cilia are presented in the appendix. Evidence suggests that regenerated cilia may not be as physiologically perfect as those formed normally during embryogenesis. Sea urchin embryonic cilia are valuable models for studying molecular details of cilia assembly and differentiation as well as gene activation, cell signaling, and pattern formation during development.

PMID: 30777178 [PubMed - indexed for MEDLINE]

Categories: pubmed

Microinjection of oocytes and embryos with synthetic mRNA encoding molecular probes.

Latest Publications - Thu, 06/20/2019 - 19:34
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Microinjection of oocytes and embryos with synthetic mRNA encoding molecular probes.

Methods Cell Biol. 2019;150:189-222

Authors: von Dassow G, Valley J, Robbins K

Abstract
We describe methods and techniques for introduction of molecular probes in the form of synthetic mRNA by rapid repetitive microinjection into oocytes or early embryos of echinoderms and various invertebrates. Construct assembly is followed by standard kit-based in vitro mRNA synthesis, with slight modifications to optimize expression and clean-up. Variations of a basic microinjection procedures are detailed for echinoderms: starfish oocytes (Patiria miniata or other species), purple urchin (Strongylocentrotus purpuratus) and sand dollar (Dendraster excentricus) zygotes, with notes included for other invertebrate eggs and embryos as well.

PMID: 30777176 [PubMed - indexed for MEDLINE]

Categories: pubmed

Microinjection methods for sea urchin eggs and blastomeres.

Latest Publications - Thu, 06/20/2019 - 19:34
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Microinjection methods for sea urchin eggs and blastomeres.

Methods Cell Biol. 2019;150:173-188

Authors: Yaguchi J

Abstract
Methods for microinjection into sea urchin eggs have become relatively easier because of the technical improvements by a number of researchers in the past decades. However, the size and the characteristics, such as the elasticity and toughness, of the eggs and embryos differ in species, so that we still need to modify the details of methods to adapt to each target. In this section, I list microinjection methods for three species: Hemicentrotus pulcherrimus, which has relatively tough eggs, Temnopleurus reevesii, which has slightly weak eggs, and Strongylocentrotus purpuratus, which is the most used species in sea urchin biology. In addition, I describe the methods for co-injection of morpholino anti-sense oligonucleotides and mRNAs, as well as the method for microinjection into blastomeres.

PMID: 30777175 [PubMed - indexed for MEDLINE]

Categories: pubmed

Culturing echinoderm larvae through metamorphosis.

Latest Publications - Thu, 06/20/2019 - 19:34
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Culturing echinoderm larvae through metamorphosis.

Methods Cell Biol. 2019;150:125-169

Authors: Hodin J, Heyland A, Mercier A, Pernet B, Cohen DL, Hamel JF, Allen JD, McAlister JS, Byrne M, Cisternas P, George SB

Abstract
Echinoderms are favored study organisms not only in cell and developmental biology, but also physiology, larval biology, benthic ecology, population biology and paleontology, among other fields. However, many echinoderm embryology labs are not well-equipped to continue to rear the post-embryonic stages that result. This is unfortunate, as such labs are thus unable to address many intriguing biological phenomena, related to their own cell and developmental biology studies, that emerge during larval and juvenile stages. To facilitate broader studies of post-embryonic echinoderms, we provide here our collective experience rearing these organisms, with suggestions to try and pitfalls to avoid. Furthermore, we present information on rearing larvae from small laboratory to large aquaculture scales. Finally, we review taxon-specific approaches to larval rearing through metamorphosis in each of the four most commonly-studied echinoderm classes-asteroids, echinoids, holothuroids and ophiuroids.

PMID: 30777174 [PubMed - indexed for MEDLINE]

Categories: pubmed

The painted sea urchin, Lytechinus pictus, as a genetically-enabled developmental model.

Latest Publications - Thu, 06/20/2019 - 19:34
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The painted sea urchin, Lytechinus pictus, as a genetically-enabled developmental model.

Methods Cell Biol. 2019;150:105-123

Authors: Nesbit KT, Fleming T, Batzel G, Pouv A, Rosenblatt HD, Pace DA, Hamdoun A, Lyons DC

Abstract
Although sea urchins are one of the oldest and most widely used marine model systems, few species have been routinely kept in culture through multiple generations. The workhorse of the field is the purple urchin Strongylocentrotus purpuratus. However, one disadvantage of S. purpuratus is its long generation time, making it impractical as a model for generating and maintaining transgenic lines. In an effort to develop a sea urchin that is suitable for transgenerational experiments and the generation of transgenic lines, we have focused on development of updated culturing methods and genomic resources for the painted sea urchin, Lytechinus pictus. Compared to S. purpuratus, L. pictus have relatively large eggs, develop into optically clear embryos, and the smaller adults can become gravid in under a year. Fifty years ago, Hinegardner developed culturing methods for raising L. pictus through metamorphosis. Here, we provide an updated protocol for establishing and maintaining L. pictus in the laboratory, and describe a new genome resource for this urchin. In our hands, L. pictus reach the 4-armed pluteus stage at 4 days; become competent to metamorphosis at 24 days; and are gravid by 6 months. Plutei and juveniles are fed on a diet of algae and diatoms, and adults are fed on kelp. We also make available a L. pictus transcriptome generated from developmental stages (eggs to 2-day-old plutei) to support the annotation of our genome sequencing project, and to enhance the utility of this species for molecular studies and transgenesis.

PMID: 30777173 [PubMed - indexed for MEDLINE]

Categories: pubmed

Larvae of Caribbean Echinoids Have Small Warming Tolerances for Chronic Stress in Panama.

Latest Publications - Tue, 06/18/2019 - 19:29
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Larvae of Caribbean Echinoids Have Small Warming Tolerances for Chronic Stress in Panama.

Biol Bull. 2019 04;236(2):115-129

Authors: Perricone V, Collin R

Abstract
In species with complex life cycles, early developmental stages are often less thermally tolerant than adults, suggesting that they are key to predicting organismal response to environmental warming. Here we document the optimal and lethal temperatures of larval sea urchins, and we use those to calculate the warming tolerance and the thermal safety margin of early larval stages of seven tropical species. Larvae of Echinometra viridis, Echinometra lucunter, Lytechinus williamsi, Eucidaris tribuloides, Tripneustes ventricosus, Clypeaster rosaceus, and Clypeaster subdepressus were reared at 26, 28, 30, 32, and 34 °C for 6 days. The temperatures at which statistically significant reductions in larval performance are evident are generally the same temperatures at which statistically significant reductions in larval survival were detected, showing that the optimal temperature is very close to the lethal temperature. The two Echinometra species had significantly higher thermal tolerance than the other species, with some surviving culture temperatures of 34 °C and showing minimal impacts on growth and survival at 32 °C. In the other species, larval growth and survival were depressed at and above 30 or 32 °C. Overall, these larvae have lower warming tolerances (1 to 5 °C) and smaller thermal safety margins (-3 to 3 °C) than adults. Survival differences among treatments were evident by the first sampling on day 2, and survival at the highest temperatures increased when embryos were exposed to warming after spending the first 24 hours at ambient temperature. This suggests that the first days of development are more sensitive to thermal stress than are later larval stages.

PMID: 30933644 [PubMed - indexed for MEDLINE]

Categories: pubmed

Light-Dependent Electrical Activity in Sea Urchin Tube Feet Cells.

Latest Publications - Tue, 06/18/2019 - 19:29
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Light-Dependent Electrical Activity in Sea Urchin Tube Feet Cells.

Biol Bull. 2019 04;236(2):108-114

Authors: Marconi LJ, Stivale A, Shah MA, Shelley C

Abstract
Sea urchins can detect and respond to light, and many species of sea urchins are negatively phototaxic. Light detection is hypothesized to occur via photoreceptors located on sea urchin tube feet, and opsins have been detected in tube feet, spines, and the test. However, the molecular mechanisms underlying light detection are, for the most part, unknown. Individual tube feet disc cells were isolated from purple sea urchins (Strongylocentrotus purpuratus), and the electrical responses of these cells to varying levels of illumination were quantified using the patch clamp technique. No currents were observed under bright illumination, whereas under dark conditions, large, slowly activating currents were consistently observed. Two types of cells were functionally identified based on their responses to darkness. Type I cells sustained currents indefinitely in the dark, whereas Type II cell currents spontaneously decayed after several seconds. The large currents observed were composed of the summation of many smaller events that were characterized by a rapid onset and an exponentially decaying component, which may be indicative of direct vesicular release from the tube feet disc cells in response to the dark conditions.

PMID: 30933638 [PubMed - indexed for MEDLINE]

Categories: pubmed

Molecular and Morphological Toxicity of Diatom-Derived Hydroxyacid Mixtures to Sea Urchin Paracentrotus lividus Embryos.

Latest Publications - Tue, 06/18/2019 - 19:29
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Molecular and Morphological Toxicity of Diatom-Derived Hydroxyacid Mixtures to Sea Urchin Paracentrotus lividus Embryos.

Mar Drugs. 2019 Mar 01;17(3):

Authors: Albarano L, Ruocco N, Ianora A, Libralato G, Manfra L, Costantini M

Abstract
Oxylipins such as polyunsaturated aldehydes (PUAs) and hydroxyacids (HEPEs) are signaling molecules derived from the oxidation of polyunsaturated fatty acids. They are common in diatoms that constitute a major group of microalgae in freshwater and oceanic ecosystems. Although HEPEs represent the most common oxylipins produced by diatoms, little information is available on their effects on marine invertebrates, and most of the information has been obtained by testing individual HEPEs. Our previous studies reported that four hydroxyacids, i.e., 5-, 9-, 11-, and 15-HEPE, were able to induce malformations and a marked developmental delay in sea urchin Paracentrotus lividus embryos, which had not been reported for other oxylipins. Here, we tested a mixture of 5-, 9-, 11-, and 15-HEPE at different concentrations for the first time. The results showed that mixtures of HEPEs have synergistic effects that are much more severe compared to those of individual HEPEs: The HEPE mixtures induced malformations in sea urchin embryos at lower concentrations. Increasing HEPE mixture concentrations induced a marked increase in the number of delayed embryos, until all embryos were delayed at the highest concentration tested. At the molecular level, the HEPE mixtures induced variations in the expression of 50 genes involved in different functional processes, mainly down-regulating these genes at the earliest stages of embryonic development. These findings are ecologically significant, considering that during diatom blooms, sea urchins could accumulate HEPEs in concentrations comparable to those tested in the present study.

PMID: 30823630 [PubMed - indexed for MEDLINE]

Categories: pubmed

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