Variability of Chromosome Number in the Lobsters,Homarus AmericanusandHomarus Gammarus

Abstract

SUMMARYExamination of 42 testicular cells from H. americanus yielded a diploid chromosome number of 110 with a range of 94 to 185. The diploid number in H. gammarus was determined to be 95.5 with a range of 90.5 to 134.5 The meiotic chromosome number of H. americanus was found to be bimodal at 66.5 and 68. The meiotic chromosome number in H. gammarus was 62.5. The range of meiotic chromosome counts in H. americanus was 50.5 to 83.5. In H. gammarus the range was 45 to 88.The wide range of chromosome numbers in the spermatocytes of both H. americanus and H. gammarus indicates a strong probability that supernumerary chromosomes exist in both species. Although the size and overlapping of the chromosomes made counting difficult, it is unlikely that these factors alone would result in such a wide variation in chromosome numbers.