Publisher Summary This chapter discusses basic concepts and advances of invertebrate immunity. In mammals and other higher vertebrates, a plethora of information exists on the origin, development, structure, and functions of the cells and tissues of the immune system. The cells of the invertebrate immune system can be subdivided into two main groups—namely, the freely circulating blood cells/coelomocytes and a variety of fixed cells. These latter cells may be either scattered throughout the tissues or localized together in hemopoietidphagocytic organs. In addition to these cell-mediated defenses, there are a number of chemical and mechanical barriers to parasite invasion. The chapter also explains the structure and classification of blood cells/coelomocytes. It provides a functional approach for blood cell classification and the cells are arranged into five main groups—namely, progenitor cells, phagocytic cells, hemostatic cells, nutritive cells, and pigmented cells.

Invertebrate Immunity: Basic Concepts and Recent Advances

In each of two reciprocal cross-infection experiments, a digenetic trematode (Microphallus sp.) was found to be significantly more infective to snails (Potamopyrgus antipodarum) from its local host populations. This gives strong evidence for local adaptation by the parasite and indicates that there is a genetic basis to the host-parasite interaction. It is suggested that the parasite should be able to track common snail genotypes within populations and, therefore, that it could be at least partially responsible for the persistence of sexual subpopulations of the snail in those populations that have both obligately sexual and obligately parthenogenetic females.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1558-5646.1989.tb02616.x

Adaptation by a parasitic trematode to local populations of its snail host.

Publisher Summary The study of intramolluscan single and double trematode infections has proved to be a useful approach in better understanding host–parasite relationship Modification and disruption of snail infection with trematodes is reviewed and the parameters and characteristics of various infection combinations are described Biologically, however, the inter-trematode reactions and the responses of the snail host offer remarkable opportunities to examine and isolate various aspects of this host–parasite relationship The single species infection patterns differ widely between the pure sporocyst type, exemplified by S mansoni, and the redial type, typified by P segregatum Characteristics of each are reviewed Their interaction is then reviewed, based on original data and comparison with other studies Redial predation (“direct antagonism”) is discussed in terms of relative activity, efficiency, and predatory response to triggering stimuli in the snail Possible mechanisms of indirect antagonism are reviewed, with a fuller consideration of snail immunity as induced by these infections and measured experimentally The parameters or characteristics of single-species infection are described and related to one another in a preliminary fashion as an “adaptation index” (AI), which includes such parameters as infection rate, period for 50% snail death, and period to cercarial shed The trematode method is locally applicable, using indigenous strains supplied and sustained at a high level by continual reseeding with eggs of the controlling trematode (or processed faeces from the appropriate final hosts) Effective biocontrol as a self-sustaining life-cycle appears highly improbable, as is the expectation that this method can be adopted on a wide scale with the same controlling agent

Intramolluscan inter-trematode antagonism: a review of factors influencing the host-parasite system and its possible role in biological control.

Evidence supporting the concept that the parasitic trematode Schistosoma mansoni may escape immune reactions from its vertebrate (man) or invertebrate (the freshwater snail Biomphalaria glabrata) hosts by using signal molecules it has in common with these hosts was obtained by the following experiments. The presence of immunoactive proopiomelanocortin (POMC)-derived peptides [corticotropin (ACTH), beta-endorphin] in, and their release from, S. mansoni was demonstrated. Coincubation of adult worms with human polymorphonuclear leukocytes or B. glabrata immunocytes led to the appearance of alpha-melanotropin (MSH) in the medium. The conclusion that this alpha-MSH resulted from conversion of the parasite ACTH by neutral endopeptidase 24.11 (NEP) present on these cells was supported by the fact that the alpha-MSH level in the medium was markedly reduced by addition of the specific NEP inhibitor phosphoramidon. This interpretation is substantiated by the fact that no conversion was observed in comparable tests with human monocytes, which exhibit no NEP activity. alpha-MSH has the capacity to inactivate formerly active immunocytes not only from the definitive host (man, hamster) but also from the intermediate host (B. glabrata), as determined by microscopic computer-assisted examination of conformational changes. POMC-derived peptides have been detected in B. glabrata hemolymph 2, 10, and 24 days after infection by S. mansoni miracidia. Immunocytes from infected snails were found to be inactivated, and this inactivation was prevented by antibodies directed against ACTH and alpha-MSH. The immunoactive beta-endorphin released from S. mansoni does not appear to be subject to enzymatic conversion. Since it is active at lower concentrations, it may be used for distant signaling.

https://www.pnas.org/content/pnas/89/2/778.full.pdf

Immunosuppression in the definitive and intermediate hosts of the human parasite Schistosoma mansoni by release of immunoactive neuropeptides.

We have tried to show that freshwater gastropods (especially those in temporary waters) are generally less well adapted to avoid predation by crushing or other shell destruction than are most benth...

Coevolution of Freshwater Gastropods and Their Predators

Although the biological control of medically important snails has been suggested from time to time during the past quarter of a century (Nagano, 1927; Bequaert, 1928; Mozely, 1939, 1951; McMullen, 1952), the subject has, as yet, received but little serious consideration. Upon the initiation of our studies (Chernin, Michelson & Augustine, 1956a, b) the literature was searched for references to predators, parasites and diseases of molluscs which might furnish leads for experimental investigation.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/E368EA22E6AD4AD205F92177DBD57E35/S0031182000022101a.pdf/div-class-title-studies-on-the-biological-control-of-schistosome-bearing-snails-predators-and-parasites-of-fresh-water-mollusca-a-review-of-the-literature-div.pdf

Studies on the biological control of schistosome-bearing snails. Predators and parasites of fresh-water mollusca: a review of the literature

Biomphalaria glabrata amoebocytes: effect of Schistosoma mansoni infection on in vitro phagocytosis.

1. Thirty-one strains representing eight species and four genera of the molluscan family Planorbidae were surveyed for the presence of hemagglutinins and hemolysins. Extracts prepared from albumen-glands and egg-masses, as well as hemolymph, were assayed by a micro-hemagglutination technique in which human erythrocytes were used as receptors.2. Hemagglutinins and hemolysins for human erythrocytes were not uniformily present in all members of the family and detection of these substances depended, in part, on the material tested.3. Neither heating to 56° C, dialysis, storage at -20° C for up to a year, nor repeated freezing and thawing appeared to effect the agglutinating activity of egg or albumen-gland extracts.4. Inhibition of the agglutinating activity of Helisoma hemolymph could be accomplished with N-Acetyl-D-Galactosamine, but this sugar had no effect on the activity of Biomphalaria agglutinins.5. There is evidence to suggest that the source and nature of agglutinins from Helisoma and Biomphalaria sp...

Agglutinins and lysins in the molluscan family planorbidae: a survey of hemolymph, eggmases albumen-gland extracts

Seventeen populations of snails (Biomphalaria glabrata) from the state of Bahia, Brazil were studied with respect to their susceptibility to infection with an allopatric strain of Schistosoma mansoni. Two of the populations were from the city of Salvador, 3 from other sites in Bahia, and 12 from habitats in the municipio Castro Alves. Our data show that the Bahian snail populations are extremely variable in their susceptibility to an allopatric strain of S. mansoni and that the phenomenon is not associated solely with distantly separated strains, but is present, as well, in adjacent populations situated in a restricted geographic region. Of the 6 populations found to be completely refractory to infection when exposed at a size of 5–7 mm, only 2 were refractory when exposed at 5–12 days of age. It is suggested that the variability to infection displayed by populations in a restricted geographic area may be explained by assuming that the Founder Principle was operative.

E.H. Michelson

Papers

Studies on the biological control of schistosome-bearing snails. Predators and parasites of fresh-water mollusca: a review of the literature

Biomphalaria glabrata amoebocytes: effect of Schistosoma mansoni infection on in vitro phagocytosis.

Agglutinins and lysins in the molluscan family planorbidae: a survey of hemolymph, eggmases albumen-gland extracts

Susceptibility of Bahian Populations of Biomphalaria Glabrata to an Allopatric Strain of Schistosoma Mansoni

Biomphalaria glabrata amoebocytes: Assay of factors influencing in vitro phagocytosis