Karyological analysis of the sea cicada Blepharipoda liberate Shen from the Rizhao intertidal zone, China

Blepharipoda liberate Shen is a commercially valuable seafood species that has important ecological significance in Shandong Province, China. Although B. liberate is crustacean, its external characteristics are not entirely those of shrimps or crabs. The question of whether B. liberate is a shrimp or a crab has been debated in recent years. We studied the karyotype of B. liberate by light microscopy using air-drying and spreading methods. We obtained mitotic chromosomal plates from B. liberate larvae, and from adult B. liberate females subsequent to egg-laying. The results revealed that B. liberate has 53 pairs of chromosomes (i.e., n=53 and 2 n=106), a characteristic shared with four species of crab. The karyogram of B. liberate consists of 25 metacentric, 14 submetacentric, 11 subtelocentric and 3 telocentric pairs. We did not find any heteromorphosis sex chromosomes. Tissue from larvae, gills and ovaries can be used for chromosomal investigations, and we found similar lampbrush chromosomes in ovary cells. Comparatively speaking, larvae tissue is more practical, and ovary tissue is more suitable for the preparation of lampbrush chromosomes. B. liberate is more closely related to crabs than to shrimps, based on the numbers of chromosomes. The B. liberate karyotype reported here provides a basis for further comparative cytogenetic studies of species populations.