The developmental biology of annual fishes. II. Naturally occurring dispersion and reaggregation of blastomeres during the development of annual fish eggs

摘要: Complete dispersion and subsequent reaggregation of pre-embryonic blastomeres, features characteristic annual fish development, are analyzed in Austrofundulus myersi Dahl. Cleavage produces a typical teleost blastoderm. During the mid-blastula stages, blastomeres segregate into two populations; deep which disperse, outer form enveloping cell layer. When epiboly layer periblast commences, come together as consolidated mass then migrate outward amoeboid cells. has concluded, completely dispersed. After few days, these cells to definitive aggregate within embryogenesis occurs. The process was quantified vivo by determining “coefficients dispersion.” Amoeboid were found be: uniformly distributed when is completed (day 2); randomly on day 3; aggregated 4. The origin developmental pattern involved spatial temporal dissociation processes embryogenesis. This been accomplished interposition dispersion-reaggregation phases. They may represent an exaggeration phases incipient localized aggregation occur most teleosts. considered be control mechanism operating principle requirement for “critical mass” necessary prelude primary events survival value dispersed phase discussed. Comparative studies 43 closely related species have shown that present only those cyprinodont fishes with life cycles. group includes members following genera: Aphyosemion (annual only); Austrofundulus; Cynolebias (including Cynopoecilus); Nothobranchius; Pterolebias; Rachovia; Roloffia. Non-annual cyprinodonts develop do other fishes. Some transitional patterns.