Sea Urchin Research Articles

Bioactive Polyketides from the Natural Complex of the Sea Urchin-Associated Fungi Penicillium sajarovii KMM 4718 and Aspergillus protuberus KMM 4747

The marine-derived fungal strains KMM 4718 and KMM 4747 isolated from sea urchin Scaphechinus mirabilis as a natural fungal complex were identified as Penicillium sajarovii and Aspergillus protuberus based on Internal Transcribed Spacer (ITS), partial β-tubulin (BenA), and calmodulin (CaM) molecular markers as well as an ribosomal polymerase two, subunit two (RPB2) region for KMM 4747. From the ethyl acetate extract of the co-culture, two new polyketides, sajaroketides A (1) and B (2), together with (2′S)-7-hydroxy-2-(2′-hydroxypropyl)-5-methylchromone (3), altechromone A (4), norlichexanthone (5), griseoxanthone C (6), 1,3,5,6-tetrahydroxy-8-methylxanthone (7), griseofulvin (8), 6-O-desmethylgriseofulvin (9), dechlorogriseofulvin (10), and 5,6-dihydro-4-methyl-2H-pyran-2-one (11) were identified. The structures of the compounds were elucidated using spectroscopic analyses. The absolute configurations of the chiral centers of sajaroketides A and B were determined using time-dependent density functional theory (TDDFT)-based calculations of the Electronic Circular Dichroism (ECD) spectra. The inhibitory effects of these compounds on urease activity and the growth of Staphylococcus aureus, Escherichia coli, and Candida albicans were observed. Sajaroketide A, altechromone A, and griseofulvin showed significant cardioprotective effects in an in vitro model of S. aureus-induced infectious myocarditis.

Advances in Aquaculture Hatchery Techniques of Sea Urchin Sphaerechinus granularis (Lamarck, 1816) (Echinoidea: Toxopneustidae): Broodstock Conditioning and Spawning Induction.

In response to the growing demand for sea urchin gonads (roe or uni) in Asian and European markets and the concerns regarding the overexploitation of wild populations, this preliminary study addresses the need for cost-effective protocols in echinoculture. The primary focus of this research was to evaluate the gonadosomatic index (GI) in captive-conditioned Sphaerechinus granularis over a five-month period and compare it with that of their wild-caught conspecifics. Additionally, two different spawning induction methods were assessed: potassium chloride (KCl) injection and agitation. Results indicate that captive-conditioned sea urchins exhibit significantly higher GI values when compared to their wild-caught counterparts. Furthermore, it was observed that the agitation method is equally effective as the KCl injection in triggering a positive response, i.e., gamete ejection, while maintaining lower mortality rates among the subjected S. granularis. In conclusion, this preliminary study underscores the pivotal role of broodstock conditioning in supporting the sustainability of sea urchin aquaculture. Moreover, the spawning induction method through agitation emerges as a viable alternative to the traditional intracelomic KCl injection, offering comparable efficacy without compromising the survival of the broodstock. These findings have significant implications for the development of sustainable sea urchin farming practices.

Intensive sea urchin harvest rescales Paracentrotus lividus population structure and threatens self-sustenance.

The harvest of the edible sea urchin Paracentrotus lividus is intensively practiced in some regions of the Western Mediterranean Sea. The removal of the largest individuals can determine an overall reduction in population size and a size class truncation that can lead to a drastic drop the self-sustenance. The aim of this study is to evaluate the variability of the population reproductive potential across 5 years in one of the main harvest hotspots of Sardinia (Western Mediterranean Sea). The breeding stock consists of commercial and under-commercial size individuals which were sampled on a monthly basis to estimate their GonadoSomatic Index (GSI) and the Individual Gamete Output (IGO). In addition, the reproductive potential of the population-Total Gamete Output (TGO)-was calculated across the 5-year period in relation with the variation of the density of the breeding stock. During the last year, the reproductive potential was also estimated in a well-conserved population of a nearby Marine Protected Area. No significant variability in GSI and IGO was found over the 5 years nor when compared with the ones of protected population in the last year. However, the intensive harvest drastically rescaled the population body-size: although density of the commercial size class remained low, density of the under-commercial size-class halved from the beginning to the end of the study. Accordingly, the proportional decrease of their gamete output contribution led to a 40% loss of the reproductive potential of the whole population in the 5-year period. Interestingly, despite the loss of reproductive potential due to the decrease of the breeding stock density, the average values of IGO slightly increased across the years leading to the highest Annual Gamete Output (AGO) during the fourth year of sampling. This positive pattern could suggest a mechanism of reproductive investments of the survivors in terms of gonad production rate or increase in spawning intensity. This work provides evidence of the direct effect of size-selective harvesting on the rapid loss of population self-sustenance. Furthermore, it lays new prospective for future research of the indirect effects of the rescaling population body-size in functional traits of the sea urchin P. lividus and that could become important for both, sustainable exploitation and ecosystem conservation management.

Large‐scale one‐off sea urchin removal promotes rapid kelp recovery in urchin barrens

Sea urchin overgrazing is a leading cause of kelp forest loss and in such cases their removal is increasingly advocated for kelp forest restoration. However, refining removal approaches is needed to improve the efficiency and success of restoration, as most previous removal studies have been small scale and require ongoing removals to maintain low densities and allow kelp recovery. We investigated the effectiveness of one‐off urchin removal from large, semi‐discrete areas of urchin barrens as a tool to promote kelp recovery. We removed sea urchins (Evechinus chloroticus) from four areas (1.6–2 ha) of urchin barrens in northeastern New Zealand. Exposed urchins were reduced to approximately 7% of initial densities and remained low, yet cryptic urchin densities increased after 2 years. Kelp (Ecklonia radiata) and fucoid (Sargassum sinclairii, Carpophyllum spp.) densities increased rapidly in removal areas, but remained constant or declined in adjacent control urchin barren areas. Macroalgal canopy recovery varied among and within removal areas, but increased on average from approximately 5 to 43% in 2 years. Densities of large sea urchin predators did not increase with kelp recovery, likely due to ongoing fishing within removal areas. Our results demonstrate that a single urchin removal from large, semi‐discrete areas of urchin barrens can effectively and efficiently promote rapid multi‐species macroalgal recovery without additional actions (e.g. repeated urchin removals or macroalgae enhancement) for at least 2 years. However, this approach does not restore whole ecosystems and consequently restoration benefits through kelp recovery will be temporary without longer‐term urchin management and/or rebuilding of predator populations.

An efficient segmentation method based on semi-supervised learning for seafloor monitoring in Pujada Bay, Philippines

The semantic segmentation of marine images makes it easier to describe seafloor scenes and track marine organisms. However, creating human-annotated datasets for image segmentation requires significant time and effort. Therefore, this study proposes a semisupervised learning approach that combines the mean-teacher model and U-Net architecture for segmenting seafloor images obtained from the Philippines. The proposed method performs segmentation for categories, including corals, sea urchins, sea stars, and seagrass. Traditional manual labelling methods are used for coral, sea urchins, and sea stars. For the seagrass category, which is challenging to label manually, we used the K-means clustering algorithm to obtain corresponding labelled datasets based on the characteristics of such images and evaluated the feasibility. Compared with the U-Net-based supervised method, the semi-supervised method used in this study achieved good results and accuracy values, even with fewer labelled images.

Effects of Supplementary Kelp Feeding on the Growth, Gonad Yield, and Nutritional and Organoleptic Quality of Subadult Sea Urchin (Strongylocentrotus intermedius) with Soya Lecithin Intake History.

A 23-week feeding experiment was conducted to investigate the effects of supplementary kelp feeding on the growth, gonad development, and nutritional and sensory properties of sea urchin (Strongylocentrotus intermedius) with soya lecithin (SL) intake history. The feeding experiment was divided into experimental phase I and phase II. During phase I, 48 subadult sea urchins (initial weight: 6.28 ± 0.07 g) were fed one of the feeds with different levels of SL (0%, 1.6%, 3.2%) or kelp (Saccharina japonica) for 12 weeks. Then, all sea urchins were fed kelp for the next 11 weeks during the phase II. Each diet was randomly allocated to six cages of sea urchins. The results of phase I showed that weight gain rate (WGR), gonadosomatic index (GSI), gonad sensory properties (color and texture), and essential amino acid (EAA) contents were not significantly affected by SL level in the feed groups. High level (3.2%) of SL suppressed gonad development of S. intermedius with retarded gametogenesis in the 3.2% SL group (stage Ⅱ) compared to those fed 0% and 1.6% SL groups (stage Ⅲ). Sea urchins fed dry feeds exhibited significantly lower WGR and values of color (redness and yellowness) and texture (hardness and gumminess) but higher contents of EAA in the gonads than those fed kelp. The n-3/n-6 polyunsaturated fatty acid (PUFA) and eicosapentaenoic acid (EPA) of gonads in the groups fed with dry feeds showed no significant differences, but were significantly lower than that of kelp group. At the end of phase II, the gonad yellowness and EPA content of gonads in all dry feed groups were significantly increased by supplementary kelp feeding, with a higher increase observed in S. intermedius with SL intake history, while arachidonic acid (ARA) content was significantly improved by supplementary kelp feeding in S. intermedius with SL intake history. Gonad texture was improved to some extent by supplementary kelp feeding. These results indicated that S. intermedius fed dry feeds showed significantly higher GSI and EAA but poorer organoleptic quality and lower n-3/n-6 PUFA and EPA than those fed kelp. Kelp supplementary feeding improved the fatty acid value and organoleptic quality of gonads, especially for the sea urchins with SL intake history.

Molecular compartmentalization in a syncytium: restricted mobility of proteins within the sea urchin skeletogenic mesenchyme.

Multinucleated cells, or syncytia, are found in diverse taxa. Their biological function is often associated with the compartmentalization of biochemical or cellular activities within the syncytium. How such compartments are generated and maintained is poorly understood. The sea urchin embryonic skeleton is secreted by a syncytium, and local patterns of skeletal growth are associated with distinct sub-domains of gene expression within the syncytium. For such molecular compartments to be maintained and to control local patterns of skeletal growth: (1) the mobility of TFs must be restricted to produce stable differences in the transcriptional states of nuclei within the syncytium; and (2) the mobility of biomineralization proteins must also be restricted to produce regional differences in skeletal growth. To test these predictions, we expressed fluorescently tagged forms of transcription factors and biomineralization proteins in sub-domains of the skeletogenic syncytium. We found that both classes of proteins have restricted mobility within the syncytium and identified motifs that limit their mobility. Our findings have general implications for understanding the functional and molecular compartmentalization of syncytia.

Comparison of feeding preferences of herbivorous fishes and the sea urchin Diadema antillarum in Little Cayman.

On Caribbean coral reefs, losses of two key groups of grazers, herbivorous fishes and Diadema antillarum, coincided with dramatic increases in macroalgae, which have contributed to decreases in the resilience of these coral reefs and continued low coral cover. In some locations, herbivorous reef fishes and D. antillarum populations have begun to recover, and reductions in macroalgal cover and abundance have followed. Harder to determine, and perhaps more important, are the combined grazing effects of herbivorous fishes and D. antillarum on the structure of macroalgal communities. Surprisingly few studies have examined the feeding preferences of D. antillarum for different macroalgal species, and there have been even fewer comparative studies between these different herbivore types. Accordingly, a series of in-situ and ex-situ feeding assays involving herbivorous fishes and D. antillarum were used to examine feeding preferences. Ten macrophytes representing palatable and chemically and/or structurally defended species were used in these assays, including nine macroalgae, and one seagrass. All species were eaten by at least one of the herbivores tested, although consumption varied greatly. All herbivores consumed significant portions of two red algae species while avoiding Halimeda tuna, which has both chemical and structural defenses. Herbivorous fishes mostly avoided chemically defended species while D. antillarum consumed less of the structurally defended algae. These results suggest complementarity and redundancy in feeding by these different types of herbivores indicating the most effective macroalgal control and subsequent restoration of degraded coral reefs may depend on the recovery of both herbivorous fishes and D. antillarum.

The people behind the papers - Jian Ming Khor and Charles Ettensohn.

Syncytia are multinucleated cells that form distinct functional compartments. In a new paper in Development, Charles Ettensohn and colleagues use the sea urchin embryonic skeleton to study how specialized compartments are generated in a syncytium to give rise to local skeletal patterns. We caught up with first author Jian Ming Khor and corresponding author Charles Ettensohn, Professor at Carnegie Mellon University, to find out more about their research.

Trace elements and arsenic speciation in Paracentrotus lividus from North-West Mediterranean Sea.

Levels of 14 trace elements (Al, Ti, V, Cr, Mn, Co, Ni, Zn, As, Se, Cd, Sn, Hg, and Pb) and 5 arsenic species (arsenite/As(III), arsenate/As(V), monomethylarsonic acid/MA, dimethylarsinic acid/DMA, and arsenobetaine/AsB) were assessed in the gonads of sea urchin samples (Paracentrotus lividus) from North-West Mediterranean Sea (French coast). The samples were collected from 13 sites characterized by different types and levels of chemical contamination. Trace elements levels were measured by inductively coupled plasma-mass spectrometry (ICP-MS) following microwave (acid) digestion in a closed system, whereas As speciation analysis was carried out by ion-exchange liquid chromatography coupled with ICP-MS after microwave-assisted extraction. High levels of trace elements were found in sea urchins sampled from Corsica whereas the samples from Théoule were found to be the least contaminated. From all the analyzed urchin samples, none showed Cd, Hg, or Pb concentrations above the regulatory levels set by the European Community (EC) No. 1881/2006 for seafood or bivalve mollusks. Regarding arsenic speciation, AsB was confirmed to be the predominant species. Inorganic As (As(III) + As(V)) was mainly constituted by As(III), which was quantified in all samples. Methylated As forms (MA and DMA) represent 9 to 23% of the total As.

Combining computer vision and standardised protocols for improved measurement of live sea urchins for research and industry

AbstractTo allow sea urchin aquaculture to achieve its intended scale, efficient and precise methods for measuring large numbers of urchins in commercial‐scale operations are needed. Current protocols for measuring urchin test (shell) dimensions and mass are time‐consuming and prone to high measurement error, thus inconvenient in research and impractical in a commercial context. This study investigates and compares various measurement methods with a newly developed computer vision approach developed in this study, to establish a single protocol using precise, efficient and accessible methodology for measuring live urchins. We show that urchin wet mass can vary up to 8.73% depending on time out of water; this is significantly reduced to an average of 0.1% change by allowing urchins to drip‐dry for at least 90 s prior to weighing. We found the conventional vernier calliper method used to measure urchin dimensions to be both time‐consuming and imprecise (mean coefficient of variation (CV) of 2.41% for Tripneustes gratilla). Conversely, the computer vision programme we developed measures with higher precision (mean CV of 1.55% for T. gratilla) and is considerably faster. The software uses a series of hue saturation value filters, edge detection algorithms and distortions to measure the diameter of the test (excluding spines) of multiple urchins at once. The software is open‐source, and the protocol does not require specialised equipment (can be performed with a mobile phone camera). When the computer vision application is combined with the simple procedures described in this paper, to reduce measurement inaccuracies, urchin wet mass and diameter can be more efficiently and precisely determined. For a larger scale context, this software could easily be incorporated into various tools, such as a grading machine, to completely automate various farm processes. As such, this study has potential to assist urchin data collection in both research and commercial contexts.

Loss, resilience and recovery of kelp forests in a region of rapid ocean warming.

Changes in kelp abundances on regional scales have been highly variable over the past half-century owing to strong effects of local and regional drivers. Here, we assess patterns and dominant environmental variables causing spatial and interspecific variability in kelp persistence and resilience to change in Nova Scotia over the past 40 years. We conducted a survey of macrophyte abundance at 251 sites spanning the Atlantic coast of Nova Scotia from 2019 to 2022. We use this dataset to describe spatial variability in kelp species abundances, compare species occurrences to surveys conducted in 1982 and assess changes in kelp abundance over the past 22 years. We then relate spatial and temporal patterns in abundance and resilience to environmental metrics. Our results show losses of sea urchins and the cold-tolerant kelp species Alaria esculenta, Saccorhiza dermatodea and Agarum clathratum in Nova Scotia since 1982 in favour of the more warm-tolerant kelps Saccharina latissima and Laminaria digitata. Kelp abundances have increased slightly since 2000, and Saccharina latissima and L. digitata are widely abundant in the region today. The highest kelp cover occurs on wave-exposed shores and at sites where temperatures have remained below thresholds for growth (21 °C) and mortality (23 °C). Moreover, kelp has recovered from turf dominance following losses at some sites during a warm period from 2010 to 2012. Our results indicate that dramatic changes in kelp community composition and a loss of sea urchin herbivory as a dominant driver of change in the system have occurred in Nova Scotia over the past 40 years. However, a broad-scale shift to turf-dominance has not occurred, as predicted, and our results suggest that resilience and persistence are still a feature of kelp forests in the region despite rapid warming over the past several decades.

Aging of the sea urchin Centrostephanus rodgersii using demi-pyramid microstructure

We investigate a novel aging method that utilizes parallel ridges and grooves on the surface of demi-pyramids of the sea urchin Centrostephanus rodgersii. Analysis of marginal increments from sea urchins tagged with oxytetracycline confirmed that ridges form in the mid to late Austral spring, as seawater begins to warm. After known periods of up to three years, counts of ridges from tagged sea urchins showed that the ridges were formed annually. Differences between observed and expected counts of ridges were mostly related to readers’ inability to distinguish adjacent ridges at the growing margin of the demi-pyramid. This resulted in a higher probability of underestimating age for individuals ≥ 6 yr. Counts of the ridges on the same demi-pyramid by the same reader, and comparisons among different readers, provided estimates of random error and bias. Estimates of aging error and bias in distinguishing ridges were modeled and used to estimate ‘true’ age and age structure. Maximum estimated age was 27 yr but most individuals were estimated to be 10–15 yr. We discuss the relevance of our findings to the fishery and the broader applicability of our method to correct ages estimated from other hard parts in marine species.

Temperature-Dependent Food Consumption Rates of the Sea Urchin Mesocentrotus nudus and Top Shell Turbo sazae: Potential Impacts on Seaweed Beds.

In Korea, the expansion of barren ground and a shift in macrograzer habitats due to increasing water temperatures associated with climate change are becoming increasingly problematic. This study assessed the potential effects of the sea urchin Mesocentrotus nudus and top shell Turbo sazae on seaweed beds by examining changes in their food consumption rates in response to changes in temperature. The food consumption rates of kelp (Saccharina japonica) for both species were estimated at 5 °C, 10 °C, 15 °C, 20 °C, and 25 °C in laboratory experiments. The rate for M. nudus increased with increasing water temperature, with the highest rate of 0.001 g g-1 d-1 at 15 °C and 20 °C, and the lowest at 25 °C, which killed some individual sea urchins. The rate for T. sazae also increased with increasing water temperature, with the highest being 0.087 g g-1 d-1 at 25 °C and the lowest being at 5 °C. T. sazae had a higher food consumption rate than M. nudus at all temperatures; as water temperature increased, the difference between species increased, with the largest difference occurring at 25 °C. These findings indicate that as water temperature increases, T. sazae places greater feeding pressure on macroalgae than M. nudus.

Zoo-mediated CuO Nanoparticles Synthesis Using Sea Urchin Salmacis virgulata (L. Agassiz & Desor, 1846) Test as a Novel Reducing Agent and Evaluated the In silico Antifungal Activity

Nanotechnology provides alternatives to conventional pesticides that result in improved efficacy with a specific target, reduced doses, smart delivery, and protection from natural enemies. The present study aims to investigate the eco-friendly source of zoo-material from sea urchin Salmacis virgulata (L. Agassiz & Desor, 1846) test. This is the first-time study on sea urchin test aqueous extract using zoo-mediated CuO nanoparticle synthesis. The present results of the zoochemicals from the aqueous zoo-extract of the sea urchin S. virgulata test contained 60 zoo-compounds were recorded using GC-MS techniques. S. virgulata test zoochemicals are involved in the reduction of copper ions (Cu2+ into Cu0), which forms sea urchin-mediated copper oxide nanoparticles, and initially UV-visible, FTIR spectra confirmed the formation of Z-CuONPs. The computational study confirms the potential antifungal properties of S. virgulata test zoochemicals and CuO using molecular docking tools. The S. virgulata test recorded it as a novel metal ion-reducing agent and also provided valuable bioactive zoo-compounds, and further study is recommended to investigate the In vitro studies on various aspects of synthesized Z-CuONPs. 
 
 Graphical abstract of zoo-mediated CuO nanoparticles synthesis using sea urchin Salmacis virgulata (L. Agassiz & Desor, 1846) test as a novel reducing agent and evaluated the In silico antifungal activity

CatSper mediates not only chemotactic behavior but also the motility of ascidian sperm.

Introduction: Sperm motility, including chemotactic behavior, is regulated by changes in the intracellular Ca2+ concentration, and the sperm-specific Ca2+ channel CatSper has been shown to play an important role in the regulation of intracellular Ca2+. In particular, in mammals, CatSper is the only functional Ca2+ channel in the sperm, and mice deficient in the genes comprising the pore region of the Ca2+ channel are infertile due to the inhibition of sperm hyperactivation. CatSper is also thought to be involved in sea urchin chemotaxis. In contrast, in ascidian Ciona intestinalis, SAAF, a sperm attractant, interacts with Ca2+/ATPase, a Ca2+ pump. Although the existence of CatSper genes has been reported, it is not clear whether CatSper is a functional Ca2+ channel in sperm. Results: We showed that CatSper is present in the sperm flagella of C. intestinalis as in mammalian species, although a small level of gene expression was found in other tissues. The spermatozoa of CatSper3 KO animals were significantly less motile, and some motile sperms did not show any chemotactic behavior. These results suggest that CatSper plays an important role in ascidians and mammals, and is involved in spermatogenesis and basic motility mechanisms.

Enhanced composite thermal conductivity by percolated networks of in-situ confined-grown carbon nanotubes

Despite the ever-increasing demand of nanofillers for thermal enhancement of polymer composites with higher thermal conductivity and irregular geometry, nanomaterials like carbon nanotubes (CNTs) have been constrained by the nonuniform dispersion and difficulty in constructing effective three-dimensional (3D) conduction network with low loading and desired isotropic or anisotropic (specific preferred heat conduction) performances. Herein, we illustrated the in-situ construction of CNT based 3D heat conduction networks with different directional performances. First, to in-situ construct an isotropic percolated conduction network, with spherical cores as support materials, we developed a confined-growth technique for CNT-core sea urchin (CNTSU) materials. With 21.0 wt.% CNTSU loading, the thermal conductivity of composites reached 1.43 ± 0.13 W/(m·K). Secondly, with aligned hexagonal boron nitride (hBN) as an anisotropic support, we constructed CNT-hBN aligned networks by in-situ CNT growth, which improved the utilization efficiency of high density hBN and reduced the thermal interface resistance between matrix and fillers. With ~ 8.5 wt.% loading, the composites possess thermal conductivity up to 0.86 ± 0.14 W/(m·K), 374% of that for neat matrix. Due to the uniformity of CNTs in hBN network, the synergistic thermal enhancement from one-dimensional (1D) + two-dimensional (2D) hybrid materials becomes more distinct. Based on the detailed experimental evidence, the importance of purposeful production of a uniformly interconnected heat conduction 3D network with desired directional performance can be observed, particularly compared with the traditional direct-mixing method. This study opens new possibilities for the preparation of high-power-density electronics packaging and interfacial materials when both directional thermal performance and complex composite geometry are simultaneously required.

Alterations in sea urchin (Mesocentrotus nudus) microbiota and their potential contributions to host according to barren severity

Sea urchins are biotic factors driving the decline of kelp forests in marine ecosystems. However, few studies have analyzed the microbiota of surviving sea urchins in barren regions with scarce diet resources. Here, we analyzed the microbiota in the pharynx and gut of the sea urchin Mesocentrotus nudus located along the coast of an expanding barren region in South Korea. The ecological adaptation of genera in sea urchins was predicted using the neutral assembly model. The pharynx and gut microbiota were different, and microbes in the surrounding habitats dispersed more to the pharynx than to the gut. The gut microbiota in sea urchins is altered by barren severity and plays different roles in host energy metabolism. These findings help to understand the microbiota in sea urchins according to urchin barren and its contribution to the survival of sea urchins in severe barren regions with limited macroalgae.

Echinoidea Community Structure in the Timbul Bone Labunta Sand Waters, Buton Tengah Regency, Southeast Sulawesi

This study aims to determine the types of sea urchins (Echinoidea), the diversity index (H'), uniformity index (E), and dominance index (C) in sea urchins (Echinoidea) in Pasir Timbul Bone Labunta waters, Central Buton Regency. This research is a type of quantitative descriptive research. The determination of stations is carried out using a purposive sampling technique, namely data collection based on the presence of sea urchins (Echinoidea). This research was conducted in April-May 2023 in Pasir Timbul Bone Labunta waters, Central Buton Regency. Observations were made during the day, at the lowest tide, and when sea urchins (Echinoidea) rested in coral crevices or seagrass. The results showed that there were 5 types of sea urchins (Echinoidea), namely Diadema setosum, Echinotrix calamaris, Tripneustes gratilla, Salmacis sphaeroides and Echinometra mathaei. The diversity index at Station I is in the low category, and Stations II and III are in the medium category. Uniformity index at Station I with a low category, Stations II and III with a high category. The dominance index of Station I has a high category, and Stations II and III have a low category index value.

The Role of Soluble Adenylyl Cyclase in the Regulation of Flagellar Motility in Ascidian Sperm.

Flagellar motility in sperm is activated and regulated by factors related to the eggs at fertilization. In the ascidian Ciona intestinalis, a sulfated steroid called the SAAF (sperm activating and attracting factor) induces both sperm motility activation and chemotaxis. Cyclic AMP (cAMP) is one of the most important intracellular factors in the sperm signaling pathway. Adenylyl cyclase (AC) is the key enzyme that synthesizes cAMP at the onset of the signaling pathway in all cellular functions. We previously reported that both transmembrane AC (tmAC) and soluble AC (sAC) play important roles in sperm motility in Ciona. The tmAC plays a major role in the SAAF-induced activation of sperm motility. On the other hand, sAC is involved in the regulation of flagellar beat frequency and the Ca2+-dependent chemotactic movement of sperm. In this study, we focused on the role of sAC in the regulation of flagellar motility in Ciona sperm chemotaxis. The immunochemical analysis revealed that several isoforms of sAC protein were expressed in Ciona sperm, as reported in mammals and sea urchins. We demonstrated that sAC inhibition caused strong and transient asymmetrization during the chemotactic turn, and then sperm failed to turn toward the SAAF. In addition, real-time Ca2+ imaging in sperm flagella revealed that sAC inhibition induced an excessive and prolonged Ca2+ influx to flagella. These results indicate that sAC plays a key role in sperm chemotaxis by regulating the clearance of [Ca2+]i and by modulating Ca2+-dependent flagellar waveform conversion.