Hemocytes of the mud crab Scylla paramamosain: Cytometric, morphological characterization and involvement in immune responses

Sun

et al. 2018

Appl Environ Microbiol

Symbiotic microorganisms have been found in the hemolymph (blood) of many aquatic invertebrates, such as crabs, shrimps and oysters. Hemolymph is a critical site in host immune response. Currently, studies on hemolymph microorganisms are mostly performed with culture-dependent strategies using selective media (e.g., TCBS, 2216E, and LB) for enumerating and isolating microbial cells. However, doubts remain about the "true" representation of the microbial abundance and diversity of symbiotic microorganisms in hemolymph, particularly for uncultivable microorganisms which are believed to be more abundant than the cultured. To explore this, we developed a culture-independent cell extraction method for separating microbial cells from the hemolymph of three aquatic invertebrates (, , and) involving filtration through a 5-μm mesh filter membrane (the Filtration Method). A combination of the Filtration Method with fluorescence microscopy and high-throughput sequencing technique provides insight into the abundances and diversity of the total microbiota in the hemolymph of these three invertebrates. More than 2.6 × 10 cells/mL of microbial cells dominated by and, and, and and, were detected in the hemolymph of ,, and , respectively. A parallel study for investigating the hemolymph microbiome by comparing the Filtration Method and a culture-dependent method (the Plate Count Method), showed significantly higher microbial abundances (between 26 and 369-folds difference; P<0.05) and less biased community structures of the Filtration Method than those of the Plate Count Method. Furthermore, hemolymph of the three invertebrates harbored many potential pathogens, including ,, and Finally, the Filtration Method provides a solution that improves understanding of the metabolic functions of uncultivable hemolymph microorganisms (e.g., metagenomics) devoid of host hemocytes contamination. Microorganisms are found in invertebrates' hemolymph, a critical site in host immune response. Currently, studies on hemolymph microorganisms are mostly performed with culture-dependent strategies. However, doubts remain about the "true" representation of hemolymph microbiome. This study developed a culture-independent cell extraction method that could separate microbial cells from the hemolymph of three aquatic invertebrates (, , and) based on filtration through a 5-μm mesh filter membrane (the Filtration Method). A combination of the Filtration Method with fluorescence microscopy and high-throughput sequencing technique provides insight into the abundances and diversity of the total microbiota in the hemolymph of these three invertebrates. Our results demonstrate that the hemolymph of aquatic invertebrates harbors a much higher microbial abundance and distinct microbial community composition than previously estimated. Furthermore, this work provides a less biased solution for studying the metabolic functions of uncultivable hemolymph microbiota devoid of host hemocytes contamination.

Section: Resultssupporting

confidence: 87%

Hemolymph Microbiomes of Three Aquatic Invertebrates as Revealed by a New Cell Extraction Method

Sun

et al. 2018

Appl Environ Microbiol

“…Higher phagocytic activities were also demonstrated in the semigranular cells of signal crayfish P. leniusculus. In contrast, the phagocytic activity of semigranular cells was weaker than that of granular cells in Scylla paramamosain (15). However, it is noteworthy to mention that different subpopulations of hemocytes seem to exhibit specific preferences in phagocytosis of different bacteria or viruses.…”

Section: Biological Characteristics Of Hemocytementioning

confidence: 86%

“…Similarly, different subpopulation of hemocytes in diverse species or even in the same species of crustaceans also exhibited variable phagocytic activities. For instance, the higher phagocytic capacity has been observed in the hyaline cells rather than granular and semigranular cells of C. maenas, Carcinus aestuarii (15), and Eriocheir sinensis (16,17), while main phagocytic capabilities of granular and semigranular cells were observed in Macrobrachium rosenbergii, Penaeus monodon, and Cherax quadricarinatus (17)(18)(19)(20). Higher phagocytic activities were also demonstrated in the semigranular cells of signal crayfish P. leniusculus.…”

Section: Biological Characteristics Of Hemocytementioning

confidence: 95%

Hemocyte-Mediated Phagocytosis in Crustaceans

Liu

Zheng

et al. 2020

Front. Immunol.

Phagocytosis is an ancient, highly conserved process in all multicellular organisms, through which the host can protect itself against invading microorganisms and environmental particles, as well as remove self-apoptotic cells/cell debris to maintain tissue homeostasis. In crustacean, phagocytosis by hemocyte has also been well-recognized as a crucial defense mechanism for the host against infectious agents such as bacteria and viruses. In this review, we summarized the current knowledge of hemocyte-mediated phagocytosis, in particular focusing on the related receptors for recognition and internalization of pathogens as well as the downstream signal pathways and intracellular regulators involved in the process of hemocyte phagocytosis. We attempted to gain a deeper understanding of the phagocytic mechanism of different hemocytes and their contribution to the host defense immunity in crustaceans.

“…Granular cells are predominately connected with the PO system [27] and, along with semigranular cells, are thought to produce AMP and also contribute to antioxidant defense. [28] In crustaceans, there are reports that shrimp immune parameters (i.e., total hemocyte count, respiratory bursts, PO, and superoxide dismutase (SOD) activity) were significantly affected by exposure or ingestion of ZnO NP. [29] In a recent study on larvae, pupae, and adults of Tenebrio molitor, transmigration of nanodiamonds through the insect cuticle was followed by inhibition of cellular and humoral immune responses, presence of phagocytosed nanodiamond aggregates mainly in hemocytes, and also in fat body cells, but not in Malpighian tubule cells.…”

Section: (4 Of 25)mentioning

confidence: 99%

Addressing Nanomaterial Immunosafety by Evaluating Innate Immunity across Living Species

Boraschi

Alijagić

Auguste

et al. 2020

Small

The interaction of a living organism with external foreign agents is a central issue for its survival and adaptation to the environment. Nanosafety should be considered within this perspective, and it should be examined that how different organisms interact with engineered nanomaterials (NM) by either mounting a defensive response or by physiologically adapting to them. Herein, the interaction of NM with one of the major biological systems deputed to recognition of and response to foreign challenges, i.e., the immune system, is specifically addressed. The main focus is innate immunity, the only type of immunity in plants, invertebrates, and lower vertebrates, and that coexists with adaptive immunity in higher vertebrates. Because of their presence in the majority of eukaryotic living organisms, innate immune responses can be viewed in a comparative context. In the majority of cases, the interaction of NM with living organisms results in innate immune reactions that eliminate the possible danger with mechanisms that do not lead to damage. While in some cases such interaction may lead to pathological consequences, in some other cases beneficial effects can be identified.