Ontogenetic Studies on the Immune System of Two Locust Species: Lowsta Migratoria and Schistocerca Gregaria

  • Amira A.A.E. Tolba

    Student thesis: Doctoral ThesisDoctor of Philosophy

    Abstract

    Work presented in this thesis examines the ontogenesis of
    immunity in two species of locust, Locusta migratoria (the migratory
    locust), and Schistocerca gregaria (the desert locust). Three haemocyte types (granulocytes, coagulocytes and plasmatocytes) were observed in all stages examined and the differential blood cell count remained constant throughout development. Following antigenic challenge in all developmental stages, there was an increase in the percentage of blood granulocytes, a decline in coagulocytes and less
    consistent changes were noted in the percentage of plasmatocytes.
    Autoradiographical studies revealed proliferative activity in haemopoietic tissue following antigenic challenge but not in peripheral haemocytes. Inducible agglutinins were observed in the haemolymph following challenge with vertebrate erythrocytes and bacteria. Agglutinin titres varied with species, developmental stage and the antigen used. Opsonisation studies revealed that haemolymph from immunised Locusta could promote phagocytosis by haemocytes in vitro.

    Haemocytes of both species were able to phagocytose vertebrate
    erythrocytes, charcoal and indian ink particles in vivo. The phagocytic response to erythrocytes was stronger than that observed towards inert particles and phagocytic responses were weaker or absent in younger stages. Adult and fifth instar
    was active in phagocytosis of charcoal and indian ink, but that of
    younger stages failed to trap foreign particles.

    Haemocytes of adult and fifth instar nymphs were seen to respond
    positively in chemotaxis and chemokinesis assays. Positive
    responses were observed following exposure to erythrocytes and
    bacteria, and haemocyte capsules formed around cat gut implants also
    produced chemotaxis and chemokinesis responses.
    Schistocerca gregaria failed to encapsulate implants and, in
    general, responses in this species were weaker than those observed
    in Locusta migratoria.
    Date of AwardMay 1987
    Original languageEnglish
    Awarding Institution
    • Aston University

    Keywords

    • immune system
    • locust
    • Lowsta migratoria
    • Schistocerca gregaria

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