Aspects of the embryology and neural development of the American lobster

Abstract

It is feasible to study the anatomical, physiological, and biochemical properties of identifiable neurons in lobster embryos. To exploit fully the advantages of this preparation and to lay the foundation for single-cell studies, our recent goals have been to 1) establish a quantitative staging system for embryos, 2) document in detail the lobster's embryonic development, 3) determine when uniquely identifiable neurons first acquire their transmitter phenotypes, and 4) identify particular neurons that may serve developmental functions. Behavioral, anatomical, morphometric, and immunocytochemical studies have led to a detailed characterization of the growth and maturation of lobster embryos and to the adoption of a percent-staging system based upon the eye index of Perkins (Fish. Bull., 70:95-99, 1972). It is clear from these studies that the lobster nauplius molts at approximately 12% embryonic development (E12%) into a metanauplius, which subsequently undergoes a complete molt cycle within the egg. This molt cycle climaxes with the emergence of the first-stage larva shortly after hatching. Serotonin and proctolin, neurohormones widely distributed in the lobster nervous system, appear at different times in development. Serotonin immunoreactive neurons begin to appear at approximately E10%, with the adult complement being established by E50%. In contrast, proctolin immunoreactive neurons appear later and attain their full complement over a protracted period including larval and juvenile stages. The development of serotonergic deutocerebral neurons and their targets, the olfactory and accessory lobes in the brain, are also examined. The olfactory lobes are forming by E10% and have acquired their glomerular organization by E50%, whereas the formation of the accessory lobes is delayed; the early rudiments of the accessory lobes are seen by E50%, and glomeruli do not form until the second larval stage.

Developmental expression of the octopamine phenotype in lobsters,Homarus americanus

“…The total span of developmental time over which this occurs can be up to 9 months in the wild. Serotonin, by contrast, appears in the central nervous system within the first few days of embryonic development and the entire system is fully formed several weeks later (Beltz and Kravitz, 1987;Beltz et al, 1990Beltz et al, , 1992. The first serotonin-immunopositive fibers appear in the median protocerebrum of the brain around E10%, at the time of the first muscular contractions in the embryo .…”

Contributions of larval biology to crustacean research: a review

“…In these cases, it is represented as a stage of the embryonic development that is passed within the egg membrane, identifiable only with histological or other microscopical techniques (e.g. Beltz et al, 1992). Due to its fundamental morphology and universal appearance among the Crustacea, it may be used for the definition of this arthropod taxon (Waloßek and Müller, 1990), or conversely, for excluding from the Crustacea other taxa that are without this stage (e.g.…”

Functional differentiation of adult neural circuits from a single embryonic network

“…The developmental stages of Homarus had been extensively described since the pioneering work of Herrick (1895) and Bumpus (1891), and more recently by Helluy and Beltz (1991) and Beltz et al (1992). The principal features of the lobster Homarus gammarus development are summarized in Figure 2.…”

“…Although the developmental periods of Homarus have been described (Bumpus, 1891;Herrick, 1895;Beltz et al, 1992), there are no reports on the development of the embryonic foregut or stomodeum of lobsters or other large crustaceans. Thus, using histological techniques (see Materials and Methods) we followed the morphological development of the stomodeum which can be detected very early in the embryo of Homarus as an invagination of the ectoderm between the brain and the ventral nerve cord.…”