Invertebrate Immunology

This three-volume work provides a complete study of this well-known group of animals, dealing with every level of their biological organization, from the molecular to the zoological.
    The leech, once so prominent in the history of medicine, is again being used widely in modern hospitals, especially in microsurgery. Revival in the use of leeches coincides with recent revelations about the rich diversity of pharmacologically active peptides secreted by the leech, including the powerful anticoagulant Hirudin which was discovered in 1884. The author who has studied  leeches extensively for many years, documents for the first time the scientific and biological rationale underlying the medical use of leeches and concludes that there was a nucleus of truth behind their use in previous centuries.
    In recent years the leech has been the subject of much neurobiological research, but such research has tended to emphasize the neurophysiological aspects. This book gives an authoritative account of leech neurobiology from the biological viewpoint, with emphasis on the neuronal basis and the evolution of leech behaviour.
    The book takes up Manton's controversial thesis that insects, myriapods and onychophorans constitute a new phylum (Uniramia) unrelated to the Crustacea. He also significantly extends the argument by proposing that leeches are also allied to the Uniramia. This proposal is a major intrusion into the traditional classification of the animal kingdom, and as such is likely to gain considerable attention.
    A 'key' to the leeches of each zoogeographical region of the world and an extensive bibliography (volume 3) are included.
    The diverse and wide-ranging nature of the book should make it of interest to research workers and students in various disciplines, particularly medicine, molecular biology, neurobiology, zoology and marine biology.
    Volume 1:    0 19 857377 4,  430 pages, 170 illustrations
    Volume 2:    0 19 857622 6,  430 pages, 170 illustrations
    Volume 3:    0 19 857623 4,  240 pages

One of the dogmas of comparative (evolutionary) immunology for the last few decades has been that all invertebrates lack any form of immunological memory similar to that found in jawed vertebrates. Vaccinating invertebrates, such as shrimp, should therefore be an ineffective management strategy resulting in no more than short-lived, non-specific immune stimulation. Recent studies in crustaceans and insects, however, suggest a form of immune memory in these animals described variously as ‘immune priming’, ‘specific immune priming’ or ‘line specific immune memory’. Workers have injected various arthropod species with inactivated pathogens and then later challenged them with a dose of the same pathogen capable of killing the host, reporting enhanced survival or increased reproductive fecundity compared with animals vaccinated with an unrelated organism. Interestingly, in some studies this enhanced immunity is trans-generational (i.e. passed on to progeny). This brief review focusses on a mechanistic exploration of ‘specific immune priming’ with particular reference to shrimp culture. Humoral antimicrobial factors, such as antimicrobial peptides and lysozyme, do not possess the required specificity to explain this phenomenon. Instead, recent studies have demonstrated elevated phagocytic activity after “vaccination” that does not result from general (non-specific) stimulation in phagocytosis. This enhanced phagocytic activity is likely linked to specific recognition of determinants on the outside of microbes by the haemocytes of these “vaccinated” animals. In some cases, at least, the mechanism for recognising these determinants appears to rely upon an invertebrate homologue of the Down syndrome cellular adhesion molecule (Dscam) and the ability of the Dscam gene to produce variants of this molecule with specific binding capabilities. Pioneering studies have demonstrated that Dscam is intricately involved in phagocytosis in insects and able to produce pathogen-specific splice form variants after immune challenge or infection. This would enable an animal to tailor an immune response specifically to a pathogen. It should be noted, however, that the phenomenon of immune priming is certainly not universal, possibly because of the much lower numbers of different immune receptors that arthropods are able to produce compared with jawed vertebrates. The review concludes that immune priming in invertebrates should be re-evaluated on an animal to animal and pathogen to pathogen basis. It also notes that whilst there is evidence that vaccinating shrimp against viral and bacterial infections shows promise, the practicality of such processes and their benefit to shrimp requires further evaluation.► Shrimp culture is affected by periodic viral and bacterial diseases. ► These diseases are difficult to control. ► This review examines approaches to ‘vaccination’ of crustaceans such as shrimp. ► Changes in the immune system of shrimp following vaccination are reviewed.

Microplastics (MPs) are established contaminants of coastal ecosystem. Present investigation is aimed to assess comparative toxicity of polystyrene microplastic (PS-MP) and expanded polystyrene microplastic (EPS-MP) in the coelomocytes of Astropecten indicus, a common seastar of Digha coast of Bay of Bengal, India. Coastal water of Digha, a tourist spot of attraction, bears the ecotoxicological risk of contamination by various agents including expanded and nonexpanded microplastics of industrial origin. Coelomocytes of seastar perform multiple physiological functions including pathogen engulfment, cytotoxicity and respiratory gas exchange and considered as immunoeffector cells in echinoderms. We report an adverse shift in total count, phagocytic response, cytotoxicity and oxidative potential of the coelomocytes of A. indicus under the exposures of 0.5 and 1 mg L-1 PS-MP and EPS-MP for 7 and 14 d. Experimental data suggested a higher level of cytotoxicity of EPS-MP in coelomocytes in comparison to that of PS-MP. Seastar is considered as a keystone species, which plays an important role in maintaining the functional homeostasis of coastal ecosystem. Unrestricted contamination of coastal water by MP may lead to a persistent immunophysiological stress in seastar. Experimental endpoints may be considered as effective monitoring tool to assess ecotoxicity of MPs in seastar and alike organisms sharing the same habitat.

Specific interactions between parasite genotypes and host genotypes (Gp x Gh) are commonly found in invertebrate systems, but are largely lacking a mechanistic explanation. The genotype of invertebrate hosts can be complemented by the genomes of microorganisms living on or within the host (“microbiota”). We investigated whether the bacterial gut microbiota of bumble bees (Bombus terrestris) can account for the specificity of interactions between individuals from different colonies (previously taken as host genotype proxy) and genotypes of the parasite Crithidia bombi. For this, we transplanted the microbiota between individuals of six colonies. Both the general infection load and the specific success of different C. bombi genotypes were mostly driven by the microbiota, rather than by worker genotype. Variation in gut microbiota can therefore be responsible for specific immune phenotypes and the evolution of gut parasites may be driven by interactions with “microbiota types” as well as with host genotypes.

A survey of some immune functions of the haemolymph and circulating haemocytes of the lesser octopus, Eledone cirrhosa was carried out. Alpha-macroglobulin-like activity was found in the serum but not in the amoebocytes. Amoebocytes appeared capable of both weak phenoloxidase activity and the production of super-oxide radicals. It is suggested that, super-oxide and phenol immune functions are incompatible and that the presence of limited phenoloxidase activity in eledone amoebocytes may be an evolutionary relic.