Precocial species

Several studies have identified responses that do not involve VN participation, from marsupials to Mouse-lemurs. Where the chosen endpoint is totally unaffected by absence of the organ and in addition is dependent upon MOS activity, then it needs to be classified as VN-independent. Where VN-x results are ambiguous, as already considered for opossums (Monodelphis domestica), further analysis is desirable. For instance, Goats do not use AOS input for mating, only urinalysis, although experiential variables have not been fully explored (Ladewig et al., 1980). Examples of VN independence then exist in both altricial and precocial species. 

The newborns of birds including chickens and of some mammals such as guinea pigs and sheep can open their eyes, eat, and exhibit sleep-wake cycles similar to those found in adulthood (1—4) these animals are precocial species. The newborns of other mammals such as those of rats, cats, and rabbits are not able to open their eyes at birth and have very different sleep-wake states from their adulthood (4,5). These species are altricial mammals. There are also a variety of developmental and anatomical brain differences in altricial and precocial species that appear to relate to learning and experiential development (1). 

Nestlings of altricial species (those confined to the nest for some time after hatch) may be considerably more sensitive to lead exposure than adults, and also more sensitive than hatchlings of many precocial species. Hatchlings of precocial species, including chickens, Japanese quail, mallards, and pheasants, are relatively tolerant to moderate lead exposure, i.e., there was no effect on growth at dietary levels of 500.0 mg Pb/kg, or survival at 2000.0 mg Pb/kg. 

Preliminary results of antijuvenile hormone bioassays for precocious metamorphosis in immature stages of Oncopeltus fasciatus revealed that some of the non-linear derivatives (VI) showed higher activities and lower toxicities that those exhibited by natural precocenes or 7-ethoxy-6-methoxy-2,2-dimethylchromene, one of the most active synthetic analogs known. In addition, some of these compounds were unexpectedly inactive in the sterilization bioassay with adults of the same species (8). Further investigation of antijuvenile hormone activities of selected compounds of this series in other insects is now in progress. 

Due to concerns over potential exposure of aquatic organisms to NP, a number of acute and chronic toxicity tests have been conducted for both freshwater and saltwater species of invertebrates, fish, and aquatic plants. NP is considered an endocrine dis-ruptor chemical and induces production of vitellogenin in male rainbow trout, a process that normally occurs only in female fish in response to estrogenic hormones during the reproductive cycle. NP also induces precocious development of ovaries and an intersex condition in some fish species. 

Phytochemicals, such as the precocenes, isolated from Ageratum houstonianum [126], interfere with JH biosynthesis. In sensitive insect species, application of these dichromenes to larval instars results in precocious metamorphosis to sterile adults or sterility in adult females following treatment. Pesticides based on these compounds would be useful in the control of insects which are primarily destructive in their immature stages. Other phytochemicals which potentially function as "antijuvenile hormones" include dimethyl sciadinonate, isolated from the leaves of avocado, Persea americana Mill [127, 128], Ingestion of this... 

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