Ultrastructural Evidence for Temperature-Dependent Ca2+ Release from Fish Sarcoplasmic Reticulum During Rigor Mortis

The release or leakage of ca2+ from the sarcoplasmic reticulum (SR) during rigor mortis of fish muscle was investigated by transmission electron microscopy using pyroantimonate and related biochemical changes. Ca2+ -pyroantimonate deposits were observed in the SR immediately after spiking the fish. At the onset of rigor for fish stored at 0°C, no deposits were found in the SR; however, fish stored for the same period at woe which were still in the pre-rigor state, clearly showed Ca2+ deposits in the SR. In association with the Ca2+ translocation, ATP degraded faster at 0 c than at 10 °C, probably due to enhancement of myofibrillar ATPase activity by the increasing Ca2 + concentrations. Therefore, rapid Ca2+ release from the SR at 0°C seemed to trigger the acceleration of fish rigor mort is at this temperature, analogous to the phenomenon called cold shortening

Genetic diversity of blue-spotted mudskipper (Boleophthalmus boddarti) populations in Gulf of Thailand

Environmental changes and the reduction of habitat can threaten populations of mudskippers, which have a distinct life cycle compared with other fish species. Genetic diversity and structure are crucial information for the conservation plan of this species. The genetic diversity was investigated on the blue-spotted mudskipper, Boleophtalmus boddarti, in the Gulf of Thailand. In total, 178 fish were collected from six locations in the Gulf. Based on the 320 bp sequences of the mitochondrial control region of the 55 haplotypes observed, the most common was in 88 fish from all locations. Total haplotype diversity and nucleotide diversity values (mean ± SD) were h = 0.751 ± 0.036 and π = 0.0069 ± 0.0001, respectively. There was a significant (p = 0.011) difference in π between inner and outer Gulf samples. Although the analysis of molecular variance suggested the absence of genetic structuring within the Gulf, two clear groups of haplotypes were evident in the medianjoining network of haplotypes. Group I included haplotypes from all locations and group II was identified by haplotypes with an additional adenine at the 16078th position based on the mitochondrial genome sequence of B. boddarti (Accession no. KF87427). The results of the nonmetric multidimensional scaling and Bayesian assignment test were indicative of genetic divergence between the inner and outer Gulf, suggesting that despite the high potential for dispersal of planktonic larvae, water currents may act as a physical barrier to gene flow in the study area. The observed signals of population divergence between B. boddarti from the inner and outer Gulf of Thailand may account for the presence of this oceanographical barrier. Mismatch distributions, based on the observed number of differences among haplotype pairs, produced a unimodal distribution with a peak close to the y-axis, suggesting recent demographic expansion. The results could augment future study with baseline information on the maternal genetic variation and structure of the bluespotted mudskipper, B. boddarti, populations in the Gulf of Thailand

THERMAL STABILITY OF SYNTHETIC PEPTIDES MIMICKING THE SEQUENCE OF THE REGION CONTAINING THE SKIP RESIDUES IN SQUID MYOSIN ROD

Myosin is the major protein in skeletal muscles including those of fish and shellfish. The characteristics of this protein are closely related to the biological function and the quality and physical properties of musclefood. In the myosin rod (the coiled-coil region of myosin), several amino acid residues, known as skip residues, seem to destabilize the ordered structure (heptad repeat). These residues might be responsible for reducing thermal stability. Attempts were thus made to examine the role of these residues in the rod of squid myosin, based on the thermodynamic properties of synthetic peptides which have been designed to mimic the partial sequence of myosin heavy chain from the squid Todarodes pacificus mantle muscle. Five peptides, namely, with the sequence of Trp1343 -Ala1372  having the skip residue Glu1357 at the center (Peptide WT), without the skip residue (Peptide Δ), with the replacements of the skip residue (Glu) by Ile, Gln and Pro (Peptides E/I, E/Q, and E/P, respectively) to modify the helix forming propensity, were synthesized. The results obtained showed that the stability of the peptides as measured by circular dichroism spectrometry was in the order of Peptide Δ > Peptide WT > Peptide E/Q > Peptide E/P > Peptide E/I. It is suggested that the presence of the skip residues dexterously tunes the stability or flexibility of the coiled-coil structure, thus possibly regulating thick filament formation and further gel formation ability of myosin

THERMAL STABILITY OF SYNTHETIC PEPTIDES MIMICKING THE SEQUENCE OF THE REGION CONTAINING THE SKIP RESIDUES IN SQUID MYOSIN ROD

Myosin is the major protein in skeletal muscles including those of fish and shellfish. The characteristics of this protein are closely related to the biological function and the quality and physical properties of muscle food. In the myosin rod (the coiled-coil region of myosin), several amino acid residues, known as skip residues, seem to destabilize the ordered structure (heptad repeat). These residues might be responsible for reducing thermal stability. Attempts were thus made to examine the role of these residues in the rod of squid myosin, based on the thermodynamic properties of synthetic peptides which have been designed to mimic the partial sequence of myosin heavy chain from the squid Todarodes pacificus mantle muscle. Five peptides, namely, with the sequence of Trp1343 -Ala1372  having the skip residue Glu1357 at the center (Peptide WT), without the skip residue (Peptide Δ), with the replacements of the skip residue (Glu) by Ile, Gln and Pro (Peptides E/I, E/Q, and E/P, respectively) to modify the helix forming propensity, were synthesized. The results obtained showed that the stability of the peptides as measured by circular dichroism spectrometry was in the order of Peptide Δ > Peptide WT > Peptide E/Q > Peptide E/P > Peptide E/I. It is suggested that the presence of the skip residues dexterously tunes the stability or flexibility of the coiled-coil structure, thus possibly regulating thick filament formation and further gel formation ability of myosin

Identification and characterization of a matrix protein (PPP-10) in the periostracum of the pearl oyster, Pinctada fucata

AbstractThe periostracum is a layered structure that is formed as a mollusk shell grows. The shell is covered by the periostracum, which consists of organic matrices that prevent decalcification of the shell. In the present study, we discovered the presence of chitin in the periostracum and identified a novel matrix protein, Pinctada fucata periostracum protein named PPP-10. It was purified from the sodium dodecyl sulfate/dithiothreitol-soluble fraction of the periostracum of the Japanese pearl oyster, P. fucata. The deduced amino acid sequence was determined by a combination of amino acid sequence analysis and cDNA cloning. The open reading frame encoded a precursor protein of 112 amino acid residues including a 21-residue signal peptide. The 91 residues following the signal peptide contained abundant Cys and Tyr residues. PPP-10 was expressed on the outer side of the outer fold in the mantle, indicating that PPP-10 was present in the second or third layer of the periostracum. We also determined that the recombinant PPP-10 had chitin-binding activity and could incorporate chitin into the scaffolds of the periostracum. These results shed light on the early steps in mollusk shell formation

Molecular phylogeny of the rotifers with two Indonesian Brachionus lineages

The rotifer Brachionus plicatilis is an ecologically and commercially important species, and has been studied in various fields such as population dynamics, ecotoxicology and aging. However, recent studies have revealed that the B. plicatilis lineages involve an unknown number of cryptic species, and the group has been regarded as the Brachionus complex. One cause of this complicated taxonomy is the lack of surveys in the tropical zone, which is characterized by enormous species-richness. Accordingly, in this study we collected two Brachionus rotifers from the Sumatra and Sulawesi Islands, Indonesia, and determined their partial nucleotide sequences of mitochondrial DNA cytochrome c oxidase subunit I gene. Subsequently, we constructed molecular phylogenetic trees with fourteen species/lineages from four genera including the two Indonesian rotifers. The two Indonesian Brachionus rotifers were respectively found to be phylogenetically close to B. ibericus and B. rotundiformis. On the other hand, Japanese B. plicatilis was suggested to be phylogenetically closer to B. Manjavacas, which is proposed to be a new species, than to Spanish B. plicatilis. These results imply that the current taxonomy of the Brachionus is problematic, and a major revision is necessary to establish a reliable taxonomy of this group

A high-quality, haplotype-phased genome reconstruction reveals unexpected haplotype diversity in a pearl oyster

Homologous chromosomes in the diploid genome are thought to contain equivalent genetic information, but this common concept has not been fully verified in animal genomes with high heterozygosity. Here we report a near-complete, haplotype-phased, genome assembly of the pearl oyster, Pinctada fucata, using hi-fidelity (HiFi) long reads and chromosome conformation capture data. This assembly includes 14 pairs of long scaffolds (>38 Mb) corresponding to chromosomes (2n = 28). The accuracy of the assembly, as measured by an analysis of k-mers, is estimated to be 99.99997%. Moreover, the haplotypes contain 95.2% and 95.9%, respectively, complete and single-copy BUSCO genes, demonstrating the high quality of the assembly. Transposons comprise 53.3% of the assembly and are a major contributor to structural variations. Despite overall collinearity between haplotypes, one of the chromosomal scaffolds contains megabase-scale non-syntenic regions, which necessarily have never been detected and resolved in conventional haplotype-merged assemblies. These regions encode expanded gene families of NACHT, DZIP3/hRUL138-like HEPN, and immunoglobulin domains, multiplying the immunity gene repertoire, which we hypothesize is important for the innate immune capability of pearl oysters. The pearl oyster genome provides insight into remarkable haplotype diversity in animals

N-Acetyl-d-Glucosamine-Binding Lectin in Acropora tenuis Attracts Specific Symbiodiniaceae Cell Culture Strains

Many corals establish symbiosis with Symbiodiniaceae cells from surrounding environments, but very few Symbiodiniaceae cells exist in the water column. Given that the N-acetyl-d-glucosamine-binding lectin ActL attracts Symbiodiniaceae cells, we hypothesized that corals must attract Symbiodiniaceae cells using ActL to acquire them. Anti-ActL antibody inhibited acquisition of Symbiodiniaceae cells, and rearing seawater for juvenile Acropora tenuis contained ActL, suggesting that juvenile A. tenuis discharge ActL to attract these cells. Among eight Symbiodiniaceae cultured strains, ActL attracted NBRC102920 (Symbiodinium tridacnidorum) most strongly followed by CS-161 (Symbiodinium tridacnidorum), CCMP2556 (Durusdinium trenchii), and CCMP1633 (Breviolum sp.); however, it did not attract GTP-A6-Sy (Symbiodinium natans), CCMP421 (Effrenium voratum), FKM0207 (Fugacium sp.), and CS-156 (Fugacium sp.). Juvenile polyps of A. tenuis acquired limited Symbiodiniaceae cell strains, and the number of acquired Symbiodiniaceae cells in a polyp also differed from each other. The number of Symbiodiniaceae cells acquired by juvenile polyps of A. tenuis was correlated with the ActL chemotactic activity. Thus, ActL could be used to attract select Symbiodiniaceae cells and help Symbiodiniaceae cell acquisition in juvenile polyps of A. tenuis, facilitating establishment of symbiosis between A. tenuis and Symbiodiniaceae cells

Live imaging of center of calcification formation during septum development in primary polyps of Acropora digitifera

Recent studies have revealed that stony corals create their extracellular skeletons via biologically controlled calcification, in which amorphous calcium carbonate (ACC), regarded as precursors of aragonite crystals, have been observed at nanoscale using electron microscopy. However, the exact mechanism by which ACC is generated, and how it contributes to skeletal growth in coral calcifying tissue, remains enigmatic. The septal skeleton of an individual polyp is composed of radially aligned plates extending upward from the aboral calcifying tissue. This structure includes microstructure known as the centers of calcification (CoC). However, despite its importance, direct in vivo observation of septal growth has not been reported. Observations under transmitted illumination using polarized light microscopy on calcifying tissue of young Acropora digitifera revealed small crystals, a few micrometers in size, that accompany subtle movements and that emerge exclusively on the inner wall of the pocket in extracellular calcifying fluid (ECF). Crystal growth initiated from small, scattered crystals on a glass plate resembles this phenomenon observed in coral skeletons. Time-lapse photographs of 12 individuals in early primary polyp settlement revealed this process in three individuals, documenting 13 of these crystal events. This phenomenon occurred solely at the bases of subsequently formed septa. These crystals differ notably from fusiform crystals and from dumbbell-like or rod-like crystals growing individually. Upright two-photon microscopy captured movement of sub-micron-sized fluorescent calcein-accumulating particles, emphasizing their presence on the surface of the growing fronts of septa. Methodological advances that facilitate comprehensive in vivo observation of sub-micron-sized structures, calcein-accumulating particles to the skeleton, are needed to develop a more detailed understanding of coral skeletal growth

Introduction for Fisheries and Aquatic Biology

Chapter I. Aquatic Environment. Ken FURUYA and Ichiro YASUDA : chapter_1.pdfChapter II. Biology and Ecology of Aqua-Shere. Toyoji KANEKO, Katsumi TSUKAMOTO, Atsushi TSUDA, Yuzuru SUZUKI and Katsufumi SATOH : chapter_2.pdfChapter III. Aquatic Resource and Production. Ichiro AOKI, Kazuo OGAWA, Taku YAMAKAWA and Tomoyoshi YOSHINAGA : chapter_3.pdfChapter IV. Chemistry of Aquatic Organism and Their Utilization. Hiroki ABE, Shugo WATABE, Yoshihiro OCHIAI, Shigeru OKADA, Naoko YOSHIKAWA, Yoshiharu KINOSHITA, Gen KANEKO and Shigeki MATSUNAGA : chapter_4.pdfChapter V. Relation between Aqua-Shere and Human Life. Hisashi KUROKURA, Hirohide MATSUSHIMA, Shingo KUROHAGI, Haruko YAMASHITA, Akinori HINO, Kazumasa IKUTA, Satoquo SEINO, Masahiko ARIJI, Ken FURUYA, Junichiro OKAMOTO and Nobuyuki YAGI : chapter_5.pdfPart of "Introduction for Fisheries and Aquatic Biology