Hemolymph Cells Research Articles

Methodological approaches to the comparative assessment of cellular reactions of innate immunity in mollusk <I>Pomacea</I> sp. (<I>Caenogastropoda, Ampullariidae</I>) in experimental aseptic inflammation

One of the significant methodological problems that arise in the study of cells of the innate immunity of invertebrates is the unsuitability of culture media and even salt solutions intended for mammals and humans. Another important methodological point is the significantly pronounced reactions of coagulation, which play an important protective role in all invertebrates, but manifest themselves in vitro in cellular suspensions prepared even with optimal saline solutions for this animal. To solve this problem, researchers widely use an anticoagulation buffer with ethylenediaminetetraacetic acid (EDTA) even in functional tests. From the standpoint of traditional approaches of mammalian immunology, the use of EDTA is possible only for the study of cell morphology, but not their functions. The aim of the work is to adapt methodological approaches to the comparative assessment of cellular reactions of innate immunity in Pomacea sp mollusks in experimental aseptic inflammation. To evaluate the functions of phagocytic cells in mollusk Pomacea sp., we used a complete salt solution (CSS) with optimal concentrations of glucose, calcium ions, magnesium with addition to prevent coagulation, cellular aggregation and degranulation instead of EDTA sodium salt of heparin at a concentration of 100 IU/mL (CSS-hep). As a result of a specially conducted experiment, it was shown that during incubation of hemolymph cells in this solution, their viability is preserved, evaluated by flow laser cytometry during incubation with annexin V-PE (PE Annexin V) and 7-aminoactinomycin D (7- AAD), as well as in a test with trypan blue. The possibility of studying the phagocytic activity and a phagosome acidification of leukocytes from hemolymph, hematopoiesis organ (kidney) and the focus of inflammation induced by intramuscular injection of sterile suspension of zymosan using CSS-hep is shown. Unlike the Limnaea stagnalis and Biomphalaria glabrata mollusks, in which the production of reactive oxygen species by phagocytes in the luminol-dependent chemiluminescence reaction is well documented, we were unable to induce this reaction in Pomacea sp. mollusks. In a specially conducted experiment, we did not reveal the effect of the sodium salt of heparin at a concentration of 100 IU/mL on the production of reactive oxygen species by rat phagocytes.

Studies on immunological characteristics and transcriptomic analysis of Litopenaeus vannamei low salt-tolerance family

Litopenaeus vannamei is a widely distributed euryhaline aquatic animal, affected by low salinity, which can impact its disease resistance and immunity. However, there is a limited understanding of the adaptation mechanisms of L. vannamei with different genetic backgrounds to low salinity. Therefore, the present study aimed to compare the immunity characteristics and transcriptomics of L. vannamei low salt-tolerant (FG I/J) and low salt-sensitive (control) families. Also, the disease resistance and immune parameters (including [THC], hemolymph cell viability, lysozyme activity [LZM], phenoloxidase content [PO], interleukin-6 [IL-6], and tumor necrosis factor-alpha [TNF-α]) of the FG I/J and control families of L. vannamei under low salinity (5‰) and ambient salinity (24‰) were examined. Additionally, hepatopancreas transcriptomics of the FG I/J and control families were analyzed at a salinity of 5‰. The results showed that the FG I/J family had higher disease resistance to Vibrio parahaemolyticus and stronger immunological capacity than the control family. Transcriptomic analysis showed significantly enriched energy metabolism and immune regulation pathways. Therefore, we speculated that energy metabolism provides sufficient energy for immunological modulation in the FG I/J family to deal with long-term low-salt stress and achieve high growth and survival rates.

Development and Evaluation of a Shrimp Virus (IHHNV)-Mediated Gene Transfer and Expression System for Shrimps.

An efficient gene transfer and expression tool is lacking for shrimps and shrimp cells. To solve this, this study has developed a shrimp DNA virus-mediated gene transfer and expression system, consisting of insect Sf9 cells for viral packaging, the shrimp viral vector of pUC19-IHHNV-PH-GUS and the baculoviral vector of Bacmid or Bacmid-VP28 encoding the shrimp WSSV envelope protein VP28. The pUC19-IHHNV-PH-GUS vector was constructed by assembling the genomic DNA of shrimp infectious hypodermal and hematopoietic necrosis virus (IHHNV), which has shortened inverted terminal repeats, into a pUC19 backbone, and then an expression cassette of baculoviral polyhedron (PH) promoter-driven GUS (β-glucuronidase) reporter gene was inserted immediately downstream of IHHNV for proof-of-concept. It was found that the viral vector of pUC19-IHHNV-PH-GUS could be successfully packaged into IHHNV-like infective virions in the Sf9 cells, and the gene transfer efficiency of this system was evaluated and verified in three systems of Sf9 cells, shrimp hemolymph cells and tissues of infected shrimps, but the GUS expression could only be detected in cases where the viral vector was co-transfected or co-infected with a baculovirus of Bacmid or Bacmid-VP28 due to the Bacmid-dependence of the PH promoter. Moreover, the packaging and infection efficiencies could be significantly improved when Bacmid-VP28 was used instead of Bacmid.

Predicting the immunomodulatory activity of probiotic lactic acid bacteria using supervised machine learning in a Cornu aspersum snail model

In the process of screening for probiotic strains, there are no clearly established bacterial phenotypic markers which could be used for the prediction of their in vivo mechanism of action. In this work, we demonstrate for the first time that Machine Learning (ML) methods can be used for accurately predicting the in vivo immunomodulatory activity of probiotic strains based on their cell surface phenotypic features using a snail host-microbe interaction model. A broad range of snail gut presumptive probiotics, including 240 new lactic acid bacterial strains (Lactobacillus, Leuconostoc, Lactococcus, and Enterococcus), were isolated and characterized based on their capacity to withstand snails' gastrointestinal defense barriers, such as the pedal mucus, gastric mucus, gastric juices, and acidic pH, in association with their cell surface hydrophobicity, autoaggregation, and biofilm formation ability. The implemented ML pipeline predicted with high accuracy (88 %) strains with a strong capacity to enhance chemotaxis and phagocytic activity of snails’ hemolymph cells, while also revealed bacterial autoaggregation and cell surface hydrophobicity as the most important parameters that significantly affect host immune responses. The results show that ML approaches may be useful to derive a predictive understanding of host-probiotic interactions, while also highlighted the use of snails as an efficient animal model for screening presumptive probiotic strains in the light of their interaction with cellular innate immune responses.

From Personal Care to Coastal Concerns: Investigating Polyethylene Glycol Impact on Mussel's Antioxidant, Physiological, and Cellular Responses.

Pharmaceutical and personal care products (PPCPs) containing persistent and potentially hazardous substances have garnered attention for their ubiquitous presence in natural environments. This study investigated the impact of polyethylene glycol (PEG), a common PPCP component, on Mytilus galloprovincialis. Mussels were subjected to two PEG concentrations (E1: 0.1 mg/L and E2: 10 mg/L) over 14 days. Oxidative stress markers in both gills and digestive glands were evaluated; cytotoxicity assays were performed on haemolymph and digestive gland cells. Additionally, cell volume regulation (RVD assay) was investigated to assess physiological PEG-induced alterations. In the gills, PEG reduced superoxide dismutase (SOD) activity and increased lipid peroxidation (LPO) at E1. In the digestive gland, only LPO was influenced, while SOD activity and oxidatively modified proteins (OMPs) were unaltered. A significant decrease in cell viability was observed, particularly at E2. Additionally, the RVD assay revealed disruptions in the cells subjected to E2. These findings underscore the effects of PEG exposure on M. galloprovincialis. They are open to further investigations to clarify the environmental implications of PPCPs and the possibility of exploring safer alternatives.

Stress granule related-genes during blastogenetic cycle of two colonial ascidians: Botryllus schlosseri compared to Botryllus primigenus.

AbstractBackgroundColonial ascidians are chordates known to reproduce both sexually and asexually. In the present study, we used the Mediterranean species Botryllus schlosseri and the Japanese Botryllus primigenus to investigate the possible role of tiar, ttp, and g3bp in the periodical renewal of the colonies, defined by generation changes or takeovers. In this scenario, the above genes, which codify key components for the formation of stress granules, storing specific mRNAs, can play a pivotal role, allowing the regulation of processes such as stress responses, cell proliferation, and stem cell development.ResultsWe characterized tiarx1, ttp, and g3bp2 sequences in B. schlosseri and B. primigenus. Then, we analyzed gene transcription by in situ hybridization in hemolymph cells and colony tissues, and we proceeded with quantification of the gene transcription by quantitative real‐time PCR, during the phases of the colonial blastogenetic cycle.ConclusionsOur results allowed us to assign a role in the development of the new colonial generations to the studied genes.

Identification of active shrimp U6 promoters for efficient CRISPR/Cas9 gene editing in penaeid shrimps based on a VP28-pseudotyped baculovirus expression system

The activity of species-specific U6 promoter is crucial for efficient expression of sgRNA in target cells when CRISPR/Cas9 is delivered in plasmid, thus the use of CRISPR/Cas9 technology was markedly limited in shrimps due to the lack of endogenous U6 promoter. To overcome this, in this study four candidate U6 promoters (LvU6 A-D) had been identified and cloned from the genome of penaeid shrimp (Litopenaeus vannamei), and then their activities to drive the expression of shRNA in insect Sf9 cells and shrimp primary hemolymph cells were successively analyzed using insect baculovirus expression system. It was found that all the isolated four LvU6 promoters contained all the characteristic elements (DSE, PSE and TATA box) of RNA polymerase III U6 promoter. Both a dual plasmids delivery system (Bacmid-PH-LvU6-shEGFP-P2-gBFP and Bacmid-PH-EGFP) and an all-in-one plasmid delivery system (Bacmid-PH-EGFP-LvU6-shEGFP-P2-gBFP) were constructed for RNAi analysis of reporter gene EGFP which are not pseudo-typed for the infection of Sf9 cells but pseudo-typed for the infection of shrimp cells by co-transfection with pFastBac1-VP28 (an envelope protein of shrimp virus). The obtained results showed that only LvU6 A, B and D could successfully drive the expression of shEGFP in both of the tested cells, and the order of interference efficiency was LvU6 B > LvU6 D > LvU6 A. Furthermore, the RNAi efficiency of LvU6 B was up to 27% (P < 0.05) when the dual plasmids were co-transfected at a mass ratio of 1: 0.1 in Sf9 cells, which was higher than that of the all-in-one plasmid (15%, P < 0.05). In shrimp cells, no noticeable fluorescence could be observed when dual plasmids delivery system was used; in contrast, the efficiency could reach 19% when all-in-one delivery system was used (P < 0.05). However, when LvU6 B was used in the shrimp CRISPR/Cas9 gene editing system with a co-expressed VP28 gene in the baculovirus vector, there were no mutations detected in the target gene (Bax) of both in vitro cultured shrimp cells and adult shrimps. Surprisingly, after optimizing the system by using a truncated LvU6 B promoter and introducing double sgRNAs, the insertion, deletion or replacement of target sites occurred in both shrimp cells and adult tissues (spermatophore, Oka and intestine), and the mutation rates increased up to 22% and 46%, respectively. This work has provided one active shrimp U6 promoter for efficient gene editing in shrimps and shrimp cells.

Isolation and functional identification of immune cells in hemolymph of blood clams Tegillarca granosa

Blood clam Tegillarca granosa is a type of economically cultivated bivalve mollusk with red blood, and it primarily relies on hemocytes in its hemolymph for immune defense. However, there are currently no reports on the isolation and identification of immune cells in T. granosa, which hinders our understanding of their immune defense. In this study, we employed single-cell transcriptome sequencing (scRNA-seq) to visualize the molecular profile of hemocytes in T. granosa. Based on differential expression of immune genes and hemoglobin genes, hemocytes can be molecularly classified into immune cells and erythrocytes. In addition, we separated immune cells using density gradient centrifugation and demonstrated their stronger phagocytic capacity compared to erythrocytes, as well as higher levels of ROS and NO. In summary, our experiments involved the isolation and functional identification of immune cells in hemolymph of T. granosa. This study will provide valuable insights into the innate immune system of red-blood mollusks and further deepen the immunological research of mollusks.

Microsporidian Nosema bombycis hijacks host vitellogenin and restructures ovariole cells for transovarial transmission.

Microsporidia are a group of obligate intracellular parasites that infect almost all animals, causing serious human diseases and major economic losses to the farming industry. Nosema bombycis is a typical microsporidium that infects multiple lepidopteran insects via fecal-oral and transovarial transmission (TOT); however, the underlying TOT processes and mechanisms remain unknown. Here, we characterized the TOT process and identified key factors enabling N. bombycis to invade the ovariole and oocyte of silkworm Bombyx mori. We found that the parasites commenced with TOT at the early pupal stage when ovarioles penetrated the ovary wall and were exposed to the hemolymph. Subsequently, the parasites in hemolymph and hemolymph cells firstly infiltrated the ovariole sheath, from where they invaded the oocyte via two routes: (I) infecting follicular cells, thereby penetrating oocytes after proliferation, and (II) infecting nurse cells, thus entering oocytes following replication. In follicle and nurse cells, the parasites restructured and built large vacuoles to deliver themselves into the oocyte. In the whole process, the parasites were coated with B. mori vitellogenin (BmVg) on their surfaces. To investigate the BmVg effects on TOT, we suppressed its expression and found a dramatic decrease of pathogen load in both ovarioles and eggs, suggesting that BmVg plays a crucial role in the TOT. Thereby, we identified the BmVg domains and parasite spore wall proteins (SWPs) mediating the interaction, and demonstrated that the von Willebrand domain (VWD) interacted with SWP12, SWP26 and SWP30, and the unknown function domain (DUF1943) bound with the SWP30. When disrupting these interactions, we found significant reductions of the pathogen load in both ovarioles and eggs, suggesting that the interplays between BmVg and SWPs were vital for the TOT. In conclusion, our study has elucidated key aspects about the microsporidian TOT and revealed the key factors for understanding the molecular mechanisms underlying this transmission.

Alteration of lipopolysaccharide O antigen leads to avirulence of gut-colonizing Serratia marcescens.

The reason why the potent entomopathogen Serratia marcescens fails to kill insects through oral infection is unknown. To compare effects of septic injection and oral administration of S. marcescens, we used a model bean bug, Riptortus pedestris. Most R. pedestris insects survived oral infections, but not septic infections. Although the number of S. marcescens cells in hemolymph after oral infection, which were originated from gut-colonizing S. marcescens, was higher than the fatal number of cells used in septic injection, they did not kill host insects, suggesting a loss of virulence in gut-colonizing S. marcescens cells. When gut-colonizing S. marcescens cells were septically injected into insects, they failed to kill R. pedestris and survive in hemolymph. To understand the avirulence mechanisms in gut-colonizing bacteria, lipopolysaccharides of S. marcescens were analyzed and revealed that the O antigen was lost during gut colonization. Gut-colonizing S. marcescens cells were resistant to humoral immune responses but susceptible to cellular immune responses, easily succumbing to phagocytosis of hemocytes. When cellular immunity was suppressed, the gut-colonizing S. marcescens cells recovered their virulence and killed insects through septic injection. These results suggest that a key mechanism of avirulence in orally infected S. marcescens is the loss of the O antigen, resulting in susceptibility to host's cellular immune responses.

The stress granule component TIAR during the non-embryonic development of the colonial ascidian Botryllusschlosseri

TIAR, is a nucleic acid binding protein involved in the formation of cytoplasmic foci known as stress granules, in which mRNA translation is temporarily blocked in response to stressful conditions. TIAR is used as stress granules molecular marker in vertebrates, but it is not so deeply investigated in invertebrates, especially in marine organisms. In the present work, we investigated the role of TIAR in the colonial ascidian Botryllus schlosseri during its non-embryonic development, featured by the cyclical renewal of the colony. We studied the extent of transcription during the colonial blastogenetic cycle and the location of the transcripts in Botryllus tissues. Using an anti-TIAR antibody specific for ascidians, by immunocytochemistry and immunohistochemistry assays, we studied the expression of the protein in haemolymph cells and body tissues and by transmission electron microscopy we identified its subcellular localisation. The anti-TIAR antibody was also microinjected in the circulatory system of B. schlosseri to study its effect on non-embryonic development and immune responses. Results indicate a delay in the progression of the blastogenetic cycle in injected colonies. In addition, degranulation of circulating cytotoxic cells and phagocytosis by professional, circulating phagocytes, two fundamental processes of innate immunity, were also negatively affected.

A novel medium for long-term primary culture of hemocytes of Metapenaeus ensis

The development of a suitable shrimp cell medium is essential for achieving a long-term cell culture and finite cell line of shrimps routinely. In this study, we have successfully developed an optimal shrimp cell medium that can be used for long-term in vitro culture and continuous subculture of the hemolymph cells (or hemocytes) of greasyback shrimp Metapenaeus ensis, designated as MeH cells, by shrimp serum-based and supplements-based optimization of the basic and growth medium. In this article, we have focused on the details for the preparation of the optimal shrimp cell medium by diluting and mixing of various stock solutions as well as the methods for isolation and primary culture of MeH cells.•A novel shrimp cell growth medium is developed for long-term shrimp hemocytes culture.•The preparation method of shrimp cell growth medium is successfully established.•Obvious cell activity and proliferation potential of isolated shrimp cells can be maintained beyond 30 days.

Improvement and applications of adeno-associated virus 2 (AAV-2) system for efficient gene transfer and expression in penaeid shrimp cells

Adeno-associated virus 2 (AAV-2)-mediated expression system is a well-developed and widely used gene transfer and expression tool in mammalian cells, but no attempt has been done to examine its infection and expression efficiency in shrimp cells. In this study, using eGFP as a reporter gene, we found that unmodified AAV-2 could infect primarily cultured shrimp hemolymph cells, but with an extremely low infection efficiency of up to 0.0067%. However, all the improvements of AAV-2 expression system tried in this study including the insertion of shrimp virus (IHHNV)-sourced P2 promoter into the AAV-2 vector (i.e. pAAV-CMV-P2-eGFP) and the inclusion of shrimp virus (IHHNV)-sourced nucleocapsid protein （IHCP） into or association of shrimp virus (WSSV)-sourced tegument protein (VP26) with the capsid of the improved AAV-2 s, respectively, could significantly increase the infection and expression efficiencies of this expression system in the primarily cultured shrimp hemolymph cells in comparison with wild-type AAV-2. Moreover, from the viewpoint of improving the infection and expression efficiency, the insertion of P2 promoter did best, followed by the association of WSSV tegument protein of VP26, and the last was the inclusion of IHHNV nucleocapsid protein of IHCP. In conclusion, an improved AAV-2 expression system which consists of four expression plasmids of pAAV-CMV-P2-eGFP, pAAV-RC, pHelper and pcDNA3.1-VP26 and one packaging cell line of HEK293T has been successfully developed in this study. This improved AAV-2 expression system will provide us a useful tool for efficient gene transfer and expression in shrimp cells.

Mytilus galloprovincialis releases immunologically functional haemocytes to the intervalvar space in response to tissue injury and infection.

Haemocytes of Mytilus galloprovincialis represent the main component of the internal self-defence system. Although haemocytes from haemolymph are usually studied to analyse these animals' immune response, the presence of haemocytes in the intervalvar liquid, which is essentially sea water, led us to characterize them. Several functional (ROS production, phagocytosis, gene expression, travel velocity and distance) and morphological (area, size and granularity) assays were performed by applying different stimuli to the mussels (waterborne infection, shell injury and their combination). Our results revealed that intervalvar liquid haemocytes share common characteristics with haemolymph haemocytes (for instance, the cell morphology and the cell population structure divided in three main groups) but also show significant differences in size (usually smaller in the intervalvar liquid), mobility (commonly faster in the intervalvar liquid), ROS production (higher in non-stimulated intervalvar liquid cells) and gene expression (IL17, Myd88 and CathL are over expressed in liquid intervalvar cells compared to haemolymph cells). Moreover, differences were observed when mussels were subjected to the mentioned treatments. These free intervalvar haemocytes could constitute the first line of defence as external sentinels extending the immunological alert system outside of the mussel body.

Morphological Analysis of the Hemolymph Cell Composition in the Bivalve Mollusk &lt;i&gt;Anadara&lt;/i&gt; &lt;i&gt;broughtonii&lt;/i&gt; Schrenck, 1867 (Sea of Japan)

The hemolymph cells of the ark clam Anadara broughtonii were examined using light microscopy, flow cytometry and gradient centrifugation. All three methods of analysis made it possible to identify two main types of cells in the hemolymph of the ark clam Anadara broughtonii – large granular erythrocytes and small agra-nular amebocytes. Erythrocytes accounted for 95.6 ± 0.9% of the total number of hemolymph cells. Erythrocytes were hemoglobin-containing cells with a great number of granules in the cytoplasm, a low nuclear-cytoplasmic ratio (NCR) and a lower intensity of cellular respiration compared to amebocytes. Amebocytes are cells of predominantly irregular shape with a high number of cells that do not contain or contain no more than 10 granular inclusions in the cytoplasm. All types of hemocytes found in the ark clam hemolymph demonstrated the same ability to spontaneously produce reactive oxygen species. For the first time, it has been shown that red blood cells of the ark clam Anadara broughtonii are capable of phagocytosis. At the same time, amebocytes absorbed on the average two times more zymosan particles (10.3 ± 0.7 pcs.), compared to erythrocytes (5.3 ± 0.1 pcs.).

Genotoxic effects of anthropogenic environments in the leaf litter-dwelling scorpion Tityus pusillus Pocock, 1893 (Scorpiones; Buthidae)

Invertebrates are harmed by pollution of their habitats. Litter-dwelling sedentary scorpions, such as Tityus pusillus, studied here, may be good models for examining the genotoxic effects of xenobiotics in soil. Thirty specimens were collected from five sites in Northeast Brazil with different levels of human disturbance, as well as a laboratory group. The comet assay was performed on hemolymph cell samples. Damage Index (DI) and Damage Frequency (DF%) were measured. Much higher genotoxicity was observed in animals collected in an area with human interference and solid waste, compared to those obtained in more pristine areas or the laboratory. T. pusillus may be a useful model for environmental genotoxicity assays.

Characterization of hemocytes from the marine amphipod Parhyale hawaiensis (Dana 1853): Setting the basis for immunotoxicological studies

AbstractHemocytes are circulating blood cells that play a crucial function in amphipods and other crustacean immune systems. The hemocytes of the marine tropical amphipod Parhyale hawaiensis have been used for the evaluation of DNA damage and micronuclei, but they have not been characterized in the scientific literature. The aim of this study was to describe the hemolymph cells of P. hawaiensis and study their phagocytotic activity. Basic dyes were used to differentiate the cell types and the presence of lipids. The total hemocyte counts (THCs) and the proportion and sizes of the hemocyte types were determined. Hemolymph was exposed to Escherichia coli for verification of the presence of phagocytosis. Three cell types, all containing lipids, were identified in P. hawaiensis: granulocytes (oval shape, 13.4 × 7.6 μm), semi‐granulocytes (oval shape, 14.1 × 7.2 μm), and hyalinocytes (round shape, 9.6 × 7.2 μm). Those three cell types were found in different percentages in males (64.8%, 31.1%, and 4.2%) and females (70.1%, 28.2%, and 1.7%). THCs for males were 9007 ± 3800 cells per individual and 4695 ± 1892 cells per individual for females. The cells of E. coli were phagocytized by the hemocytes. Our findings increased the knowledge of hemocytes in P. hawaiensis and is a step forward in using hemocyte‐based immune responses as an endpoint in ecotoxicology.

Changes in the cell composition of the hemolymph in the snail Planorbarius corneus after infection with the trematode Plagiorchis sp.

AbstractWe found two functional populations of hemocytes in the hemolymph of the pulmonate snail Planorbarius corneus: hyalinocytes and granulocytes. The hyalinocytes were much more numerous than granulocytes. Each population was subdivided into subpopulations based on morphological and functional characteristics. The hyalinocyte population was represented by two subpopulations differing in size, granularity, and ability to form pseudopodia. In snails infected with the trematodes Plagiorchis sp., the cellular composition of the hemolymph changes, with hemocytes being mostly represented by granulocytes. This phenomenon is associated with the fact that granulocytes form a hemocytic paletot on the surface of sporocysts of Plagiorchis sp. It is suggested that pulmonate molluscs have one lineage of hemolymph cells. Hematopoietic stem cells can divide, ensuring multiplication of prohemocytes. The latter differentiate into hyalinocytes, which, in turn, differentiate into granulocytes.

Routine development of long-term primary cell culture and finite cell line from the hemolymph of greasyback shrimp (Metapenaeus ensis) and virus susceptibility

Long-term and continuous shrimp cell cultures can offer an indispensable tool for studies on the isolation, multiplication and pathogenic mechanism of shrimp causative viruses at cellular and molecular levels. However, they are hard to be developed routinely and continuous shrimp cell line is still unavailable. This can be attributed to a great degree to the unsuitability of medium used. In this study, we have successfully developed a long-term culture condition for the hemolymph cells (or hemocytes) of greasyback shrimp Metapenaeus ensis, designated as MeH cells, by shrimp serum-based and supplements-based optimization of the basic and growth medium. Using the newly developed gelatin-containing optimal basic medium (SBM-12), MeH cell monolayer could be routinely developed and maintained healthily beyond 275 days. In the novel optimal growth medium (SGM-10), the proliferation potentials of MeH cells have been markedly improved, evidenced by the presence of dividing cells in the primarily cultured 30-day hemocytes, suggesting that the mitosis-arrest of MeH cells has been tentatively broken. It was also found that among the 4 types of hemocytes (granulocyte, semi-granulocyte, hyalinocyte and prohaemocyte), the hyalinocytes could not survive after a long-term in vitro culture, but the prohaemocytes could survive well and thus could serve as a good cell source. The addition of gelatin could significantly alter the attachment and cellular morphology of MeH cells and result in a loose attachment and round shape, which made it easy for the cells to be passaged by physical flushing for up to 32 times and a finite shrimp cell line can be developed routinely. Virus susceptibility test showed that the MeH cells cultured in the optimal growth medium were sensitive to shrimp covert mortality nodavirus (CMNV), and obvious cytopathic effects and viral multiplication were detected in the infected cells. In a word, the success in the routine development of long-term primary cell culture and finite cell line from shrimps in this study will greatly facilitate the establishment of shrimp continuous cell lines and studies on shrimp viruses.

Identification of haemocytes and histological examination of gills of the spiny oyster Spondylus gaederopus (Linnaeus, 1758)

In the framework of investigations aimed to detect new available bioindicators in marine environment, haemolymph cells and ctenidia of the Mediterranean spiny oyster, Spondylus gaederopus, have been investigated. Haemocyte count and characterisation, phagocytosis and superoxide anion production and enzyme activity assays, have been carried out. TEM observations have been performed. After gross anatomy observations, cito-histological determinations have been carried out, especially focused on ctenidia structure and function. Main results concerned the relatively low number of circulating cells, and the rich in granules granulocytes, most of which were lysosomes. Release of lysosomal enzymes was confirmed a shared trait inside bivalves. Glycogen deposits as probable result of conversion of bacteria carbohydrates, have been detected, as well as the occurrence of both acidophilic and basophilic haemocytes. Phagocytosis, both in granulocytes and agranulocytes, has been recorded, together with the production of superoxide anion. Haemocytes were found positive to acid phosphatase, alkaline phosphatase, β-glucuronidase, chloroacetylesterase and arylsulphatase. Ctenidia showed a complex organization, including two demibranch to each ctenidium, two different kinds of lamellae filament and specialized structures as ciliated disks connecting filaments in “eutherorhabdic ctenidia”. The occurrence of three different types of mucous cells in the same region of ordinary filaments has been underlined. Such features, suggesting high resistance to environmental stress and disease, allow to consider spiny oysters as promising bioindicators, although deserving of further investigations to evaluate the physiological responses to stress in controlled conditions. Present data, moreover, providing basic information on the biology of S. gaederopus, notably implement the present knowledge on the Mediterranean spiny oysters, whose under-evaluated ecological role should be carefully considered.