The Ultrastructure of the Chorion of the Fathead Minnow, Pimephales promelas

Abstract

The teleost chorion serves as a natural barrier to environmental agents. In this investigation, the chorions of the fathead minnow, Pimephales promelas, were subjected to light microscopy, transmission electron microscopy, and scanning electron microscopy during different stages of embryogenesis. The chorion is composed of an outer layer of 22 lamellae, and an inner, more electron‐dense layer. During embryogenesis, there is a great increase in the thickness of the inner layer of the chorion, with a consequential decrease in the thickness of the outer 22 lamellae. The outside surface also changes during embryogenesis. It is suggested that the chorion be taken into consideration in environmental toxicity studies, and that the number of lamellae might be a way of classifying embryos.

Scanning electron microscopy of the chorion of selected freshwater fishes

“…Some layers became compacted 4 days after fertilization (Manner et al, 1977). These authors, using SEM, described the surface of the chorion as a honeycomb-like structure of regular depressions on the day of fertilization with surface elevations that became indented after 4 days of development.…”

“…The surface of the fertilized and developing chorion of the fathead minnow appeared porous through light microscopy, but observation using TEM detected a multilamellar structure that was unbroken by pores. Some layers became compacted 4 days after fertilization (Manner et al, 1977). These authors, using SEM, described the surface of the chorion as a honeycomb-like structure of regular depressions on the day of fertilization with surface elevations that became indented after 4 days of development.…”

“…Larnning (1981) found plug-filled pores in the chorion of three salmonids. Egg surface openings in the Russian sturgeon, Acipenser guldenstadti Brandt, were reported by Markov (1975) and honeycombed structures were described for the fathead minnow, Pimephales promelas (Rafinesque) (Manner et al, 1977). The fine structure of the micropyle has also been outlined for some freshwater salmonid spawners (Stehr & Hawkes, 1979;Riehl, 1980).…”

Early ontogeny of Labeotropbeus Ahl, 1927 (Mbuna, Cichlidae, Lake Malawi), with a discussion on advanced protective styles in fish reproduction and development

“…It is known that the permeability is different in various intervals of ontogeny (e.g. Manner & Muehlemann 1976, Manner et al 1977 and the tension achieved shortly after contact with water can be a combination of initial permeability of the zona radiata, its thickness and presence or absence of chorion (Ivankov & Kurdyayeva 1973) versus the permeability of the yolk syncytium and plasma density, as well as of the existence and density of the perivitelline fluid. In an extreme case the flexibility of the primary vitelline membrane (zona radiata) with or without a secondary chorion versus yolk, embryo body and perivitelline fluid tension can generate most unusual respiratory shapes; for example, Bathygobius soporator, described by Breder (1943) and Tavolga (1950), where remnants of the chorion on portions of the vitelline membrane can possibly help to maintain the unusual shape.…”

Morphology of the fertilizable mature egg in the Acanthopagrus latus, A. schlegeli and Sparus sarba (Teleostei: perciformes: sparidae)

“…As for studies on the egg, there are quite a few studies geared towards better understanding on the morphology of teleost fish's egg and its applications to the identification and classification of phylogenetic relationship (Ivankov & Kurdyayeva, 1973; Szollosi & Billard, 1974; Lønning & Hagstrom, 1975; Manner et al , 1977; Stehr & Hawke, 1979, 1983; Riehl, 1980; Robertson, 1981; Hart et al , 1984; Brusle, 1985; Groot & Alderdice, 1985; Mikodina, 1987; Schmehl &Graham, 1987; Cotelli et al , 1988; Hirai, 1988, 1993; Lønning et al , 1988; Horst & Lasiak, 1989; Riehl & Kock, 1989; Mooi, 1990; Mooi et al , 1990; Mura, 1991). Among these studies, the study of Chen et al (1999) is the only one research that ever attempted to investigate the phylogenetic relationship based on the morphological characteristics and measurement of the egg surface.…”