摘要
本文对Omodeo(1951～1952、1955)和Vedovini(1973)等报道的正方拟爱胜蚓[Eiseniella tetraedra typica (Savigny)]的染色体数目进行了核实,对尚未见报道的夹杂带丝蚓[Lumbriculus variegalus(Moller)]染色体的核型进行了研究。夹杂带丝蚓2n=20。正方拟爱胜蚓的2n=12。在观察过程中还发现了在同一种内具有不同核型的个体,同时也发现在同一个体内具有染色体的多态现象。染色体的多态性是并存在个体内和个体间的,这种情况更有利于寡毛类动物去适应各种不同的环境,使它们得以更好地繁殖后代和延续它们的种族。
Lumbriculus variegatus(MUller)was collected from Swan Lake Park and Eiseniella tetraedra typica(Savigny)was collected from Gold Stream in Victoria, B. C. respectively. They belong to two families, Lumbriculidae and Lumbricidae. They lived in different envi- ronments and their habits were different as well. This problem was responsive to their karyotype. Cytogenetics studies of the two species revealed the karyotype of L. variegatus as 2n=20, and E. tetraedra typica as 2n=12. The relative lengths of chromosome pairs in L. variegatus were 19.7985±1.4501, 15.4201±2.5440, 13.6201±1.0471, 11.4564±2.2824, 8.6498±2.2249, 7.4798±0.9753,6.7077±0.5105, 6.3682±0.6825, 5.6328±0.8831, and 4.8655±0.7658. In E. tetraedra typica, they were 22.4821±0.6788, 20.4551±0.7765, 18.6705±1.4980, 15.5905±1.5437, 12.7445±2.0092, and 10.0574±1.4984. All were telocentromere in L. variegatus and E. tetraedra typica. In hermaphroditic oligochaetes polyploidy appeared to be more frequent. Amony the organisms, 40% of the investigated karyotypes(about 250)had been found to be polyploid(Casellato, 1987). Our observation also found the polymorphism of chromosomes in two oligochaetes. In the study, we found the different karyotype individuals in a species and the chromosome polymorphism in a specimen. From this, we could deduce that chromosome polyploidy coexists in a individual and between individuals. This fact would provide them with favourable qualities for life, the ability to resist environmental stresses, to reproduce future generations, and to continue their race. Mihailova and Subchev(1981)considered that the chromosome polymorphism was due to the mosiac occurence caused by the missing of translocation of chromosomes. Evi-dently, this paper was reliable, because we discovered not only sub-ploid, but also super-ploid, though we did not find any translocation rings. Using different times and comcentrations of colchicine for L. variegatus and E. tetraedra typica, we treated the former with a higher concentration(400μl/30ml)for 22 hrs, because they lived in the polluted water for a long time, and on the contrary, only 200μl/30ml and 2.5 hrs for the latter, because they stayed in the crystal clear water all the way. We obtained sufficient evidence to explain that the ability of L. variegatus to resist pol-lution was stronger than that of E. tetraedra typica. Anyway, the former was likely to sur-vive than the latter in nature too. It is possible that the latter can regenerate as well as the former, because they all had chromosome polymorphism.
出处
《南京大学学报（自然科学版）》
CAS
CSCD
1990年第4期675-683,共9页
Journal of Nanjing University（Natural Science）
关键词
寡毛类
染色体
核型
多倍体
oligochaeta
chromosome
karyotype
polyploid
