In elementary school science textbooks, the study unit “animal birth” has an activity to observe the embryogenesis of medaka (Oryzias latipes) while in the egg. It is important to understand this process not in isolation, but continuously. Elementary school children cannot recognize embryonic development correctly while they intermittently observe living embryos selected randomly from adult medaka or attached on waterweeds growing in an aquarium. Some supplementary teaching materials are required in observing living embryos to understand the morphogenetic process continuously. In this study, we observed the development of medaka and prepared fixed specimens of embryos, allowing their developmental stage to be observed at any time. First, we investigated whether college-level students could observe the organs and structures of fixed embryos the same as for living embryos in order to evaluate the applicability of the fixed embryos before trying to use the embryo specimens with elementary school children. The structures of the living embryos such as the blood, blood vessels, and heart, for which movements can be easily observed were better recognized compared with the fixed embryos, but there was no significant difference between the recognition of other organs and structures of living and fixed embryos. We also implemented the observation of medaka embryos in elementary school science classes with fixed embryo specimens which can show the sequence of embryonic development and we considered their utility. As a result, in the class using the fixed embryos as supplementary teaching materials along with living embryos, more children were able to recognize correctly either the days after oviposition or the process in which the body was developing, compared with the class using only textbooks. Therefore, we suggest that the use of fixed embryo specimens, along with living embryos, helps children to comprehend better the embryogenesis of medaka than the use of only textbooks does.

Insects have developed powerful innate immune system, but lack acquired immune function for antibody production and immunological memory similar to that present in vertebrates. Insect immune system is divided into two major reaction types, cellular and humoral immune responses.

Actual protective responses were shown in the silkworm larvae, Bombyx mori, which had be anaesthetized on a frozen thermal gel and subsequently injected with various inocula. As a cellular response, phagocytic activity of hemocytes was observed 3 hr after injection of India ink, followed by accumulation of the ink carbon particles in hemocytes for successive 1 day. When polystyrene beads were injected as an inoculum, the uptake of beads into hemocytes was observed evidently. Chemical protection induced by humoral immune response was also examined, using larvae injected with heat-killed bacteria and bacterial lipo-polysaccharide (LPS). Antibacterial activities in hemolymph were detected constantly 6–24 hr after injection, which were assayed by the agar cup-plate method. In addition, hemolymph samples immunized for 6, 12 and 24 hr were analyzed by native-polyacrylamide gel electrophoresis, demonstrating that inducible antibacterial proteins were found in these hemolymph samples. Based on the present study, the topic of insect immune responses is thought to be accepted as a useful teaching material in high school.