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231.
We examined annual variation in the timing of conception andparturition in the African buffalo (Syncerus caffer) and thesynchrony of birth timing with resource cues, using 8 yearsof monthly birth, rainfall, and vegetation data, measured asNormalized Difference Vegetation Index (NDVI). Monthly birthshad the strongest significant correlations with NDVI and rainfalllevels 12 and 13 months in the past, respectively. In addition,the synchrony of current year births corresponds most stronglyto the synchrony of the previous year's NDVI distribution. Becausethe gestation period of buffalo has been estimated to be around11 months, these findings suggest that improved protein levels,occurring approximately a month after the first green flushof the wet season, are either a trigger for conception or conceptionhas evolved to be synchronous with correlated environmentalcues that ensure females enter a period of peak body conditionaround the time of conception and/or parturition. With a gestationperiod of approximately 340 days, parturition occurs to takeadvantage of the period when forage has its highest proteincontent. A comparative analysis of gestation periods withinthe subfamily Bovinae indicates that African buffalo have aprotracted gestation for their body size, which we suggest isan adaptation to their seasonal environment. We also found thatinterannual variation in the birth distribution suggests a degreeof plasticity in the date of conception, and variation in thenumber of calves born each year suggest further synchrony ata timescale longer than a single year. 相似文献
232.
One major parvalbumin each was isolated from the skeletal muscle of two
reptiles, a boa snake, Boa constrictor, and a map turtle, Graptemys
geographica, while two parvalbumins were isolated from an amphibian, the
salamander Amphiuma means. The amino acid sequences of all four
parvalbumins were determined from the sequences of their tryptic peptides,
which were ordered partially by homology to other parvalbumins.
Phylogenetic study of these and 16 other parvalbumin sequences revealed
that the turtle parvalbumin belongs to beta lineage, while the salamander
sequences belong, one each, to the alpha and beta lineages defined by
Goodman and Pechere (1977). Boa parvalbumin, however, while belonging to
the beta lineage, clusters within the fish in all reasonably parsimonious
trees. The most parsimonious trees show many parallel or back mutations in
the evolution of many parvalbumin residues, although the residues
responsible for Ca2+ binding are very well conserved. These most
parsimonious trees show an actinopterygian rather than a crossoptyrigian
origin of the tetrapods in both the alpha and beta groups. One of two
electric eel parvalbumins is evolving more than 10 times faster than its
paralogous partner, suggesting it may be on its way to becoming a
pseudogene. It is concluded that varying rates of amino acid replacement,
much homoplasy, considerable gene duplication, plus complicated lineages
make the set of parvalbumin sequences unsuitable for systematic study of
the origin of the tetrapods and other higher-taxa divergence, although it
may be suitable within a genus or family.
相似文献
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