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

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.