We examined the effects of water temperature, salinity and feeding regime on leptocephalus metamorphosis, and on daily growth increment deposition and strontium:calcium (Sr:Ca) ratios of otoliths in the Pacific tarpon Megalops cyprinoides. The tarpons at the pre-metamorphic leptocephalus stage (SI) were collected in the estuary, marked with tetracycline and then reared for 18 and 30 d in 2 inde...

There is a general agreement concerning the influence of the thyroid upon the metamorphosis of anuran amphibian larvae. All a~thors who reported experiments on feeding thyroid to tadpoles, regardless of the locality in which they were carried on and on whatever species of anura they were performed, invariably found that thyroid feeding always resulted in a precocious metamorphosis. The experime...

We report here, the effects of extended competency on larval survival, metamorphosis, and postlarval juvenile growth of four closely related species of tropical sea urchins, Echinometra sp. A (Ea), E. mathaei (Em), Echinometra sp. C (Ec), and E. oblonga (Eo). Planktotrophic larvae of all four species fed on cultured phytoplankton (Chaetoceros gracilis) attained metamorphic competence within 22-...

From the experiments above described it is evident that the viscous metamorphosis of the blood platelets in shed blood is intimately associated with the early stages of coagulation and that the presence of calcium is a very important element, though perhaps not absolutely necessary. No constant differences in this phenomenon could be detected with platelets or coagulating elements from the bloo...

Thyroid hormone induces the complete metamorphosis of anuran tadpoles into juvenile frogs. Arguably, anuran metamorphosis is the most dramatic effect of a hormone in any vertebrate. Recent advances in pharmacology and molecular biology have made the study of this remarkable process in the frog Xenopus laevis attractive to developmental biologists and endocrinologists alike. In particular, the a...

The transition from larval to adult haemoglobin during natural metamorphosis of Rana catesbeiana tadpoles was studied by polyacrylamide gel electrophoresis of either untreated or reduced and alkylated haemolysates in 8 M urea. The capacity of the peripheral red cells to synthesize haemoglobin in vitro declined in the course of the development of tadpoles prior to metamorphosis. The beginning of...

Metamorphosis can be described as the period in the life cycle of an animal in which an immature individual undergoes drastic anatomical and physiological changes to develop into an adult. Usually these transitions are accompanied by a change of habitat or behaviour. Because it is present in a large number of animal phyla, we can infer that metamorphosis is an important evolutionary and develop...

The early embryonic development of Hydractinia lasts about 2.5 days until the developing planula larva acquires competence for metamorphosis. Most embryonic cells stop cycling on reaching the larval stage. In older larvae of Hydractinia, cells that are still proliferating occur exclusively in the endoderm in a typical distribution along the longitudinal axis. During metamorphosis, proliferation...

Solitary ascidians have a long legacy as model organisms for investigating developmental mechanisms because of the simplicity of their embryogenesis and their basal phylogenetic position within the chordates (Berrill, 1929; Cameron et al., 2000; Conklin, 1905; Jeffery and Swalla, 1997; Kowalevsky, 1866; Satoh, 1994). The chordate traits that unite ascidians with the cephalochordates and vertebr...

Modern development environments support refactoring by providing atomically behaviour-preserving transformations. While useful, these transformations are limited in three ways: (i) atomicity forces transformations to be complex and opaque, (ii) the behaviour preservation requirement disallows deliberate behaviour evolution, and (iii) atomicity limits code reuse opportunities for refactoring imp...