Morphological Diversity and Evolution of Egg and Clutch Structure in Amphibians

Abstract

The first part of this synthesis summarizes the morphology of the jelly layers surrounding an amphibian ovum. We propose a standard terminology and discuss the evolution of jelly layers. The second part reviews the morphological diversity and arrangement of deposited eggs-the ovipositional mode; we recognize 5 morphological classes including 14 modes. We discuss some of the oviductal, ovipositional, and postovipositional events that contribute to these morphologies. We have incorporated data from taxa from throughout the world but recognize that other types will be discovered that may modify understanding of these modes. Finally, we discuss the evolutionary context of the diversity of clutch structure and present a first estimate of its evolution.

Oviposition and egg mass morphology in barred frogs (Anura: Myobatrachidae:MixophyesGünther, 1864), its phylogenetic significance and implications for conservation management

“…Oviposition has now been observed in the wild for Our use of the term egg mass is equivalent to the concept of a 'group' of eggs sensu Altig and McDiarmid (2007), such that a group can comprise eggs from one or more bouts of egg laying and that one or more groups may make up the clutch. Altig and McDiarmid (2007) define a clutch as the total number of eggs deposited per ovulation event.…”

“…Altig and McDiarmid (2007) define a clutch as the total number of eggs deposited per ovulation event. The ovipositional mode (Altig and McDiarmid 2007) of each group of Mixophyes eggs is an adherent clump, i.e. a multilayered stack of eggs that lack a common, surrounding surface or matrix, with interstices among eggs and with adjacent eggs adherent.…”

Intracapsular algae provide fixed carbon to developing embryos of the salamanderAmbystoma maculatum

“…maculatum females deposit hundreds of eggs in shallow vernal pools each spring. The eggs are surrounded by multiple jelly layers and are deposited as masses enclosed in a thick jelly matrix that protects the embryos from pathogens, predators and contaminants (Altig and McDiarmid, 2007). Egg masses remain below the surface of the water and are often attached to vegetation.…”

Natural History and Ecology of the Critically Endangered Puerto Rican Plains Coquí, <i>Eleutherodactylus juanariveroi</i> Ríos-López and Thomas, 2007 (Amphibia: Anura: Eleutherodactylidae)¹

“…Previous studies have shown that egg jelly coat may protect eggs from predation and from microbial/fungi overgrow (e.g. Altig and McDiarmid, 2007;Touchon, 2012), which can be particularly important in the absence of parental attendance in E. juanariveroi (N. Ríos-López, unpublished data). Consequently, egg morphology could play a significant role for the maintenance of egg's internal osmotic condition and protection from external variables (e.g.…”

“…Consequently, egg morphology could play a significant role for the maintenance of egg's internal osmotic condition and protection from external variables (e.g. Beuchat et al, 1984;Altig and McDiarmid, 2007) leading to high levels of hatching success, particularly in the absence of parental care.…”