Preliminary survey of egg envelope morphology in the Macrouridae and the possible implications of its ornamentation

Abstract

The eggs of only 13 macrourid species have been reported hitherto, eight identified from free buoyant eggs and five from ripening oocytes. Eggs of 11 species had raised, hexagonally patterned ornamentation on the envelope, while two species bore only partial ornamentation. Ripening oocytes of a further eight species showed that, overall, the eggs of 13 species had characteristic hexagonal ornamentation and three partial ornamentation, but four were smooth. Fertilized eggs of Coryphaenoides (Coryphaenoides) rupestris were found with smooth envelopes, while ornamented eggs have been reported for this species also. Little taxonomic significance could be attached to these results. Some correlation was found between the three categories of egg envelope ornamentation and species' bathymetric distributions. A recent model of egg development in a slope dwelling trachichthyid species suggested analagous potential ecological advantage for ornamentational variation in macrourids. 1996 The Fisheries Society of the British Isles

Ultrastructural studies of the morphological variations of the egg surface and envelopes of the African catfish <em>Clarias gariepinus</em> (Burchell, 1822) before and after fertilisation with a discussion of fertilisation mechanism

“…Further changes were recorded at the 30 h stage (Fig.5E). Similar ornamentation patterns have been recorded by many authors working on different teleost species belonging to different taxonomic groups (Johnson and Werner, 1986;Cotelli et al, 1988;Merrett and Barnes, 1996;Chen et al, 1999;Rizzo et al, 2002;Chiou et al, 2004). Some of these authors considered the egg surface ornamentation as taxonomic characters at the specific level.…”

“…Interspecific differences in the microstructure of the chorion (egg envelope) of teleost fishes have been recognised for almost 30 years (Merrett and Barnes, 1996). Such differences have been used not only to identify eggs in plankton samples (Merrett and Barnes, 1996), but also as potentially useful taxonomic characters (Gill and Mooi, 1993;Johnson and Brothers, 1993;Britz et al, 1995;Chen et al, 1999;Britz and Breining, 2000).…”

“…Chen et al (1999) concluded that the ultrastructural features of the egg envelope were found to be helpful in species identification of the distantly related species, but not of closely related ones. Merrett and Barnes (1996) clarified Marshall's (1973) suggestion that egg envelope ornamentation is a family characteristic.…”

“…Such differences have been used not only to identify eggs in plankton samples (Merrett and Barnes, 1996), but also as potentially useful taxonomic characters (Gill and Mooi, 1993;Johnson and Brothers, 1993;Britz et al, 1995;Chen et al, 1999;Britz and Breining, 2000). Chen et al (1999) concluded that the ultrastructural features of the egg envelope were found to be helpful in species identification of the distantly related species, but not of closely related ones.…”

“…Are these instructions and their language influenced by genetic programs of both parents? To answer these questions, the fertilisation process of a fish must be described in the light of reorganisation of the chorion at fertilisation, its physiological roles, the dynamic changes of the egg cortex, the secretory functions of cortical granules, mechanisms of sperm-egg interactions, and mechanical blocking of polyspermy (Lönning and Hagstrom, 1975;Hart, 1990;Yamagami et al, 1992;Griffin et al, 1996;Merrett and Barnes, 1996;Linhart and Kudo, 1997;Chen et al, 1999;Britz and Breining, 2000;Coward et al, 2002).…”