Direct and latent effects of ocean acidification on the transition of a sea urchin from planktonic larva to benthic juvenile

Ongoing ocean acidification (OA) is expected to affect marine organisms and ecosystems. While sea urchins can survive a wide range of pH, this comes at a high energetic cost, and early life stages are particularly vulnerable. Information on how OA affects transitions between life-history stages is scarce. We evaluated the direct and indirect effects of pH (pHT 8.0, 7.6 and 7.2) on the development and transition between life-history stages of the sea urchin Strongylocentrotus droebachiensis, from fertilization to early juvenile. Continuous exposure to low pH negatively affected larval mortality and growth. At pH 7.2, formation of the rudiment (the primordial juvenile) was delayed by two days. Larvae raised at pH 8.0 and transferred to 7.2 after competency had mortality rates five to six times lower than those kept at 8.0, indicating that pH also has a direct effect on older, competent larvae. Latent effects were visible on the larvae raised at pH 7.6: they were more successful in settling (45%) and metamorphosing (30%) than larvae raised at 8.0 (17 and 1% respectively). These direct and indirect effects of OA on settlement and metamorphosis have important implications for population survival.

Evidence for Association of Vibrio Echinoideorum with Tissue Necrosis on Body Shell of the Green Sea Urchin Strongylocentrotus Droebachiensis

“Sea urchin lesion syndrome” is known as sea urchins disease with the progressive development of necrotic epidermal tissue and loss of external organs, including appendages on the outer body surface. Recently, a novel strain, Vibrio echinoideorum has been isolated from the lesions of green sea urchin (Strongylocentrotus droebachiensis), an economically important mariculture species in Norway. V. echinoideorum has not been reported elsewhere in association of with green sea urchin lesion syndrome. Therefore, in this study, an immersion based bacterial challenge experiment was performed to expose sea urchins (wounded and non-wounded) to V. echinoideorum, thereby mimicking a nearly natural host-pathogen interaction under controlled conditions. This infection experiment demonstrated that only the injured sea urchins developed the lesion to a significant degree when exposed to V. echinoideorum. Pure cultures of the employed bacterial strain was recovered from the infected animals and its identity was confirmed by the MALDI-TOF MS spectra profiling. Additionally, the hemolytic phenotype of V. echinoideorum substantiated its virulence potential towards the host, and this was also supported by the cytolytic effect on red spherule cells of sea urchins. Furthermore, the genome sequence of V. echinoideorum was assumed to encode potential virulence genes and were subjected for in silico comparison with the established virulence factors of Vibrio vulnificus and Vibrio tasmaniensis. This comparative virulence profile provided novel insights about virulence genes and their putative functions related to chemotaxis, adherence, invasion, evasion of the host immune system, and damage of host tissue and cells. Thus, it supports the pathogenicity of V. echinoideorum. In conclusion, the interaction of V. echinoideorum with injured sea urchins appears to be essential for the development of lesion syndrome and therefore, revealing its potentiality as an opportunistic pathogen.

Diversity of echinoderms of class echinoidea and holothuroidea in waingapu old pier, east sumba regency

Echinoderms are in habitats in coastal waters because is a biota that can maintain the sustainability and the balance of the coral reef ecosystem. Human activity in utili zing Echinoderms, namely in Echinoidea and Holothuroidea can affect life his life. The purpose of this study was to determine the diversity of phyla Echinoderms class Echinoidea and Holothuroidea at the Harbor Waingapu Old Pier and its use as a medium Biology learning. The research method used is purposive sampling and analyzed using the approach quantitative descriptive with the Shannon diversity index formula Wiener. Echinoderm samples were calculated using the technique quadratic transects with a plot size of 2 x 2 meters are placed perpendicularly in the direction of 50 meters using a plot of 30 plot. Environmental factors measured are temperature, salinity, degrees acidity (pH) and levels of oxygen (DO). Measurements are taken at each observation station. The results showed 11 species Echinoderms are divided into 2 classes, namely Diadema setosum, Diadema savignyi, Tripneustes gratilla, Strongylocentrotus droebachiensis, Echinocardium flavescens, Clypeaster subdepressus, and Mespilia globulus from the class Echinoidea. Holothuria atra, Holothuria scraba, Euapta godeffroyi and Chiridota rigida from the class Holothuroidea. The diversity index obtained includes medium category with a value of H = 1.696.

New Echinoderm-Crab Epibiotic Associations from the Coastal Barents Sea

During diving surveys for a Russian research project that monitored introduced species, red king crabs (Paralithodes camtschaticus) were collected at a coastal site of the Barents Sea to study the structure and dynamics of this species. Sampling of the organisms colonizing the crabs was part of this research project. For the first time, the presence of relatively large specimens of the common starfish Asterias rubens as epibionts of P. camtschaticus was observed in July 2010, 2018, and 2019. In 2010 and 2019, we also found three other echinoderm species (the Atlantic sea cucumber Cucumaria frondosa, the green sea urchin Strongylocentrotus droebachiensis, and the brittle star Ophiura sarsii). These findings add to the current list of associated species on king crabs not only in the Barents Sea but also in native areas of this host. Red king crabs have been documented as predators for these echinoderm species, and our records show additional possible interactions between king crabs and echinoderms in this region. More likely, the epibiotic lifestyle allows these echinoderms to avoid predation from red king crabs. There are no potential disadvantages derived by red king crabs through their relationships with the echinoderm epibionts due to low occurrences of these associations. We suggest no negative effects for the local red king crab population and populations of other commercial species in the Barents Sea.

Observations from the Hydrolysis of the Green Sea Urchin (Strongylocentrotus Droebachiensis)

There is a large amount of co-product generated by the sea urchin fisheries around the world, as well as a growing interest in removing large quantities of undersize and low value sea urchins from barren areas in the northern Atlantic and Pacific coasts. The authors believe there is scope to develop a hydrolysate product from this and this study gives preliminary observations on the characteristics of hydrolysate from the sea urchin Strongylocentrotus droebachiensis. The biochemical composition for S. droebachiensis were; water 64.1%, protein 3.4%, oil 0.9% and ash 29.8%. Amino acid composition, molecular weight distribution, lipid-class and fatty acid composition are also presented. The authors suggest a sensory-panel mapping be undertaken on future sea urchin hydrolysates. Possible uses for the hydrolysate are unclear at this stage but the combination of amino acids and the relatively high levels of Glycine, Aspartic acid, and Glutamic acid should be further investigated.