Tissue culture of the deep-sea bivalve Calyptogena soyoae

Sex Reversal and Analyses of Possible Involvement of Sex Steroids in Scallop Gonadal Development in Newly Established Organ-Culture Systems

Many molluscs perform sex reversal, and sex hormones may be involved in the process. In adult scallops, Patinopecten yessoensis, gonadotropin releasing hormone and 17β-estradiol (E₂) are involved in male sexual maturation, however, little is known about the effects of E₂ and testosterone (T) on the gonadal differentiation in young scallops. In the present study, scallop gonadal development was analyzed to determine the sex reversal stage in Funka bay, and effects of E₂ and T were examined. In Funka bay, almost all scallops were male at month 12. Scallops equipped with ambiguous gonads were 61.1% at month 16 and disappeared at month 18. Therefore, sex reversal in Funka bay occurs at around month 16. For establishment of organ culture systems for bivalves, Manila clam gonads were cultured in 15% L-15 medium diluted with HBSS containing 10% KSR on agarose gel at 10°C, and the gonads survived for 14 days. Scallop gonads were also able to be cultured in 30% L15 medium diluted with ASW containing 10% KSR on agarose gel for seven days. At mature stage, Foxl2 and Tesk were predominantly expressed in ovary and testis, respectively. When scallop gonads at sex reversal stage were organ-cultured, sex steroid treatment decreased Tesk expression in the majority of scallop gonads at sex reversal stage. However, no obvious change in Foxl2 and Tesk expression was detected in mature gonads in response to either E₂ or T in culture, suggesting sex steroid treatment might affect gonadal development at sex reversal stage.

Electrical Retrieval of Living Microorganisms from Cryopreserved Marine Sponges Using a Potential-Controlled Electrode

The purpose of this study was to develop a novel electrical retrieval method (ER method) for living sponge-associated microorganisms from marine sponges frozen at -80 °C. A -0.3-V vs. Ag/AgCl constant potential applied for 2 h at 9 °C induced the attachment of the sponge-associated microorganisms to an indium tin oxide/glass (ITO) or a gallium-doped zinc oxide/glass (GZO) working electrode. The electrically attached microorganisms from homogenized Spirastrella insignis tissues had intact cell membranes and showed intracellular dehydrogenase activity. Dead microorganisms were not attracted to the electrode when the homogenized tissues were autoclaved for 15 min at 121 °C before use. The electrically attached microorganisms included cultivable microorganisms retrieved after detachment from the electrode by application of a 9-MHz sine-wave potential. Using the ER method, we obtained 32 phyla and 72 classes of bacteria and 3 archaea of Crenarchaeota thermoprotei, Marine Group I, and Thaumarchaeota incertae sedis from marine sponges S. insignis and Callyspongia confoederata. Employment of the ER method for extraction and purification of the living microorganisms holds potential of single-cell cultivation for genome, transcriptome, proteome, and metabolome analyses of bioactive compounds producing sponge-associated microorganisms.

Does zebra mussel (Dreissena polymorpha) represent the freshwater counterpart of Mytilus in ecotoxicological studies? A critical review

One of the fundamentals in the ecotoxicological studies is the need of data comparison, which can be easily reached with the help of a standardized biological model. In this context, any biological model has been still proposed for the biomonitoring and risk evaluation of freshwaters until now. The aim of this review is to illustrate the ecotoxicological studies carried out with the zebra mussel Dreissena polymorpha in order to suggest this bivalve species as possible reference organism for inland waters. In detail,we showed its application in biomonitoring, as well as for the evaluation of adverse effects induced by several pollutants, using both in vitro and in vivo experiments. We discussed the advantages by the use of D. polymorpha for ecotoxicological studies, but also the possible limitations due to its invasive nature.

Attachment and detachment of living microorganisms using a potential-controlled electrode

We developed an electrical modulation method for attachment and detachment of microorganisms. Living microorganisms suspended in non-nutritive media such as PBS⁻ and artificial seawater were attracted by and selectively attached to indium tin oxide (ITO)/glass electrode regions to which a negative potential was applied. The microorganisms suspended in LB medium and glucose solution were not attracted to the ITO electrode. Dead microorganisms were not attracted to the ITO electrode. The living microorganisms were retrieved after detachment from the ITO electrode by application of a high-frequency triangular wave potential. When we applied this method to separate microorganisms from deep-sea sediment, bacteria belonging to 19 phyla and 23 classes were collected without undesirable high molecular weight contaminants such as humic acids. At the phylum and class level, respectively, 95 and 87 % of the phylotypes among electrically retrieved bacteria were common to the gene clones from the direct sediment DNA extraction. This technique is a novel useful method to prepare bacterial cells in a single population or a community for metagenomic analyses.

Cytotoxicity assessment of four pharmaceutical compounds on the zebra mussel (Dreissena polymorpha) haemocytes, gill and digestive gland primary cell cultures

Pharmaceutical compounds are considered the new environmental pollutants but at present few studies have evaluated their ecotoxicity on aquatic invertebrates. This study was aimed to investigate the in vitro cytotoxicity of four common drugs, namely atenolol (ATL), carbamazepine (CBZ), diclofenac (DCF) and gemfibrozil (GEM), on three different cell typologies from the zebra mussel (Dreissena polymorpha): haemocytes, gill and digestive gland cells. Results obtained by the Trypan blue exclusion test revealed that exposure to increasing concentrations (0.001; 0.01; 0.1; 1 and 10 mg L(-1)) of CBZ, DCF and GEM were able to significantly decrease the viability of each cell type, while the MTT (3(4,5-dimethyl-2thiazholyl)-2,5-diphenyl-2H-tetrazolium bromide) reduction assay highlighted only a slight reduction of mitochondrial activity of gill and digestive gland cells. Overall, DCF was the most cytotoxic drug for zebra mussel cells, followed by GEM, CBZ, while ATL has not a noteworthy toxic potential. Our preliminary results lay the groundwork for further in vitro evaluations, which will allow a better definition of the potential toxicity of these drugs.

Development of an in vitro culture method for cells and tissues from the zebra mussel (Dreissena polymorpha)

Despite the successful transfer of mammalian in vitro techniques for use with fish and other vertebrates, little progress has been made in the area of invertebrate tissue culture. This paper describes the development of an in vitro technique for the culture of both cells in suspension and tissue explants from the gill, digestive gland and mantle of the zebra mussel (Dreissena polymorpha) and their successful maintenance in culture for up to 14 days. Cell suspensions from the gills and digestive gland were the most successful technique developed with viability >80% maintained for up to 8 days in culture, suitable for use in short term toxicity tests. Tissue explants from the mantle were also maintained in culture for up to 14 days. This paper describes the challenges involved in the development of a novel in vitro culture technique for aquatic invertebrates.

Cell biology of deep-sea multicellular organisms

Establishing tissue cultures derived from deep-sea multicellular organisms has been extremely difficult because of the serious damage they sustain upon decompression and exposure to the high temperature of surface seawater. We developed a novel pressure-stat aquarium system for the study of living deep-sea multicellular organisms under pressure. Using this system, we have succeeded in maintaining a variety of deep-sea multicellular organisms under pressure and atmospheric conditions after gradual, slow decompression. Furthermore, we successfully cultivated and freeze-stocked pectoral fin cells of the deep-sea eel Simenchelys parasiticus collected at a depth of 1,162 m under atmospheric pressure conditions. This review describes novel capture and maintenance devices for deep-sea organisms and cell culture studies of the organisms under atmospheric and pressure conditions.

Piezotolerance of the cytoskeletal structure in cultured deep-sea fish cells using DNA transfection and protein introduction techniques

We used DNA transfection and protein introduction techniques to investigate the pressure tolerance of cytoskeletal structures in pectoral fin cells derived from the deep-sea fish Simenchelys parasiticus (habitat depth, 366-2,630 m). The deep-sea fish cells have G418 resistance. The cell number increased until day 6 of cultivation and all cells had died by day 35 when cultured in 35-mm Petri dishes in medium containing G418. Enhanced yellow fluorescent protein-tagged human beta-actin (EYFP-actin) was stably expressed by 1 in 100,000 deep-sea fish cells. Because almost none of the EYFP-actin was incorporated into actin filaments of the cells, we replaced the relatively large EYFP tag with a chemical fluorescent compound and succeeded in incorporating fluorescently labeled rabbit actins into the deep-sea fish actin filaments. Most of the filament structure in the cells with rabbit actin inserted underwent depolymerization when subjected to pressure of 100 MPa for 20 min, in contrast to control cells. There were no differences in the tubulin filament structure between control cells and deep-sea fish cells with fluorescein-labeled bovine tubulin inserted after the application of pressure ranging from 40 to 100 MPa for 20 min.

Effects of the piezo-tolerance of cultured deep-sea eel cells on survival rates, cell proliferation, and cytoskeletal structures

We investigated the pressure tolerance of deep-sea eel (Simenchelys parasiticus; habitat depth, 366-2,630 m) cells, conger eel (Conger myriaster) cells, and mouse 3T3-L1 cells. Although there were no living mouse 3T3-L1 and conger eel cells after 130 MPa (0.1 MPa = 1 bar) hydrostatic pressurization for 20 min, all deep-sea eel cells remained alive after being subjected to pressures up to 150 MPa for 20 min. Pressurization at 40 MPa for 20 min induced disruption of actin and tubulin filaments with profound cell-shape changes in the mouse and conger eel cells. In the deep-sea eel cells, microtubules and some actin filaments were disrupted after being subjected to hydrostatic pressure of 100 MPa and greater for 20 min. Conger eel cells were sensitive to pressure and did not grow at 10 MPa. Mouse 3T3-L1 cells grew faster under pressure of 5 MPa than at atmospheric pressure and stopped growing at 18 MPa. Deep-sea eel cells were capable of growth in pressures up to 25 MPa and stopped growing at 30 MPa. Deep-sea eel cells required 4 h at 20 MPa to finish the M phase, which was approximately fourfold the time required under atmospheric conditions.

Survival of deep-sea shrimp (Alvinocaris sp.) during decompression and larval hatching at atmospheric pressure

We report successful larval hatching of deep-sea shrimp after decompression to atmospheric pressure. Three specimens of deep-sea shrimp were collected from an ocean depth of 1157 m at cold-seep sites off Hatsushima Island in Sagami Bay, Japan, using a pressure-stat aquarium system. Phylogenetic analysis of Alvinocaris sp. based on cytochrome c oxidase subunit gene sequences confirmed that these species were a member of the genus Alvinocaris. All 3 specimens survived to reach atmospheric pressure conditions after stepwise 63-day decompression. Two of the specimens contained eggs, which hatched after 10 and 16 days, respectively, of full decompression. Although no molting of the shrimp larvae was observed during 74 days of rearing under atmospheric pressure, the larvae developed conventional dark-adapted eyes after 15 days.

Tissue culture of the deep-sea eel Simenchelys parasiticus collected at 1,162 m

We successfully cultivated fin cells of the deep-sea eel Simenchelys parasiticus (collected at 1,162 m) in L-15 medium supplemented with fetal bovine serum (FBS) and additional NaCl. We found that the pectoral fin cells proliferated in L-15 medium enriched with 4 g/l of NaCl salt (pH 7.3) containing 10% FBS at 10 degrees C and 15 degrees C. No cells were attached to the plastic culture plates when Dulbecco's modified Eagle's medium (pH 7.8) or 0-2 g/l of NaCl was added to the medium or when incubation was carried out at 4 degrees C. The majority of the explant outgrowth cells were detached when temperature increased to higher than 15 degrees C. The rate of proliferation of the fin cells was extremely slow and was dependent on the FBS concentration. Cell growth was enhanced by approximately 2.2-fold, and doubling time decreased from 170 h to 77 h when the FBS concentration was increased from 10% to 20% (v/v). Our established deep-sea eel cells were passaged 16 times over a 1-year period under atmospheric pressure conditions.