Open AccessChromosome variation in embryos of a solitary spider, Pityohyphantes phrygianus , with skewed sex ratio
Author(s) -
GUNNARSSON BENGT,
ANDERSSON AGNETA
Publication year - 1992
Publication title -
hereditas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 50
eISSN - 1601-5223
pISSN - 0018-0661
DOI - 10.1111/j.1601-5223.1992.tb00011.x
Subject(s) - biology , brood , chromosome , embryo , polyploid , genetics , sex ratio , ploidy , population , meiosis , sperm , spider , zoology , demography , gene , sociology
Chromosome numbers were investigated in developing embryos of the solitary sheetweb spider Pityohyphantes phrygianus (Araneae: Linyphiidae). It was concluded that 2n = 25 in males, and 2n = 28 in females, i.e., males are X 1 X 2 X 3 0. Aberrant chromosome numbers were found in 3.2 % of the embryos. In 1.8 % of the embryos, the haploid chromosome number, n = 14, was observed, suggesting that unfertilized eggs could start developing. A few polyploid embryos were also observed. The proportion of embryos with aberrant chromosome numbers was significantly higher in the second brood of the females than in the first one. The observed chromosome variation suggests that the meiosis in Pityohyphantes phrygianus is unstable. An unstable genetic mechanism may have implications at the population level in this case as the primary sex ratio is female biased in P. phrygianus. Conceivable mechanisms of the skewed sex ratio are segregation distorsion and sperm selection. The evolutionary implications of the results are discussed.