Blackburn, D.G. (1994). Standardized criteria for the recognition of
developmental nutritional patterns in squamate
reptiles. Copeia 1994: 925-935.
Abstract: In squamates, nutrients for
embryonic development can be derived from the egg itself or from the placental
membranes. This paper critically
evaluates criteria that have been used to distinguish developmental nutritional
patterns, with an emphasis on viviparous squamates. Composition
analysis of eggs and neonates is the most reliable means of quantifying sources
of nutrients for development, but tends to underestimate placental nutrient
provision. Data on gestational changes
in dry mass of the viviparous conceptus indicate only the predominant source of
nutrients for development. Specialized
allantoplacental morphology offers moderate evidence for placentotrophy, but
the functional correlates of several placental features remain unknown. Radiotracer studies reveal the capacity for
placental transport, but not its importance to embryonic nutrition. Gestational changes in wet mass of the
conceptus reveal little about nutrient sources in relatively lecithotrophic
forms, as do comparisons of the relative size of the ovum with the fetus or the
mother. Future reports should consider
the nature and quality of evidence for
inferences about developmental nutritional modes.
Reprints: daniel.blackburn@mail.trincoll.edu