Sexual dichotomy in habitat selection during the nonbreeding season was studied in the rough-skinned newt Taricha granulosa from November 1970 to August 1973 on southern Vancouver Island. Field results show that in this area adult females normally migrate from breeding ponds to overwinter on land. Adult males normally remain permanently aquatic. Related observations on the reproductive cycle of T. granulosa show that females, who lay their eggs singly, deposit them for a period of a few days, followed by a period of nonegglaying. This process is repeated at intervals. Oviposition can occur from late April to July in this area. Females who were induced to ovulate in the laboratory each deposited three eggs per day for 5 days before opposition ceased. Thus the reproductive cycles of field and taboratory-acclimated females are correlated.
The DOPA-reaction was used to identify tyrosinase in the nucleus and cytoplasm of the neural crest melanoblast of Taricha torosa, the California newt . In this urodele there is a nuclear DOPA-positive response during the normal embryonic development from the late blastula stage to the nucleus of the early melanocyte . During the gastrula stages, all nuclei of this newt are DOPA-positive . This positive nuclear response fades away after the formation of the neural crest, save in the melanoblasts . The only cells that give a positive DOPA marking in the cytoplasm are the melanoblasts . This cytoplasmic reaction appears while the melanoblast nucleus still gives a DOPA-positive reaction . Tyrosinase activity, as marked by unlabeled DOPA, has ceased in the fully mature melanocyte . The red nuclei, seen in some of the animals in the maturing melanocyte and adjacent tissues, may be in the hallachrome stage of melanin formation . There is a diffuse distribution of DOPA reactivity in the resting nucleus, and an adherence of the DOPA-marking in the region of the dividing chromosomes in the mitosis of DOPA-positive nuclei of the melanoblast . These observations suggest that tyrosinase may be among the chromosomally bound enzymes of the chromatin space .
The normal developmental sequence of the dermal and epidermal melanophores in the California newt, Taricha torosa, with the first documentation of melanoblasts after hatching, is presented. It is shown that the first larval melanophore population of the dorsal integument is confined to the dermis, and that a chronologically separate second melanophore population is confined to the epidermis. This second population of melanophores begins to appear late in larval development and eventually provides the dorsal brown pigmentation of the adult.
Adult Taricha granulosa are relatively radioresistant in both their active (summer and spring) and inactive (winter) phases. Animals exposed to doses between 2700 and 3600 rads in their inactive phase died between 80 and 107 days post irradiation. Animals irradiated with similar doses in their active phase died between 40 and 75 days post irradiation. Some observations relating to changes in pigmentation are discussed.
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