Comparison of the genetic relationship between nine Cephalopod species based on cluster analysis of karyotype evolutionary distance

Abstract

Karyotype analysis was carried out on gill cells of three species of octopods using a conventional air-drying method. The karyotype results showed that all the three species have the same diploid chromosome number, 2n=60, but with different karyograms as 2n=38M+6SM+8ST+8T, FN (fundamental number)=104 (Cistopus chinensis Zheng et al., 2012), 2n=42M+6SM+4ST+8T, FN=108 (Octopus minor (Sasaki, 1920)) and 2n=32M+16SM+12T, FN=108 (Amphioctopus fangsiao (d’Orbigny, 1839–1841)). These findings were combined with data from earlier studies to infer the genetic relationships between nine species via cluster analysis using the karyotype evolutionary distance (De) and resemblance-near coefficient (λ). The resulting tree revealed a clear distinction between different families and orders which was substantially consistent with molecular phylogenies. The smallest intraspecific evolutionary distance (De=0.2013, 0.2399) and largest resemblance-near coefficient (λ=0.8184, 0.7871) appeared between O. minor and C. chinensis, and Sepia esculenta Hoyle, 1885 and S. lycidas Gray, 1849, respectively, indicating that these species have the closest relationship. The largest evolutionary gap appeared between species with complicated karyotypes and species with simple karyotypes. Cluster analysis of De and λ provides information to supplement traditional taxonomy and molecular systematics, and it would serve as an important auxiliary for routine phylogenetic study.

Cytogenetic studies in three octopods, Octopus minor, Amphioctopus fangsiao, and Cistopus chinensis from the coast of China

“…In conclusion, the present study combining a previously published paper (Wang and Zheng 2017) highlights our increased knowledge of cephalopod cytogenetic studies. Up to now, cytogenetic studies of the cephalopods have stepped forward: Thirteen species of cephalopod chromosome information have been reported, of which three are related to silver staining and C-banding, also fourteen species of cephalopod genome size or haploid DNA content have been revealed.…”

“…Collection of samples and chromosome slides preparation based on the previous published paper (Wang and Zheng 2017). The nucleoli in interphase and the NORs in metaphase were visualized using rapid silver nitrate staining using the previous methods (Howell and Black 1980).…”

“…The previous chromosome analysis of cephalopods had revealed 2n=60 or 92 in most species studied, including O.minor , A.fangsiao , C.chinensis , two sepiids ( Sepiaesculenta and S.lycidas Gray, 1849) and three loliginids ( Heterololigobleekeri Natsukari, 1984, Sepioteuthislessoniana Blainville, 1824 and Photololigoedulis (Hoyle, 1885)) (Gao and Natsukari 1990, Adachi et al 2014, Wang and Zheng 2017), although Nautilusmacromphalus Sowerby, 1849 had 2n=52 chromosomes (Bonnaud et al 2004), and the studies led by Papan and Jazayeri reported the chromosome number of S.arabica Massy, 1916 and S.pharaonis Ehrenberg, 1831 was 2n=48 (Papan et al 2010, Jazayeri et al 2011). However, there are only a few studies on the cephalopod chromosomes in reported publications, and there are no researches on the band type in these species.…”

“…All these factors seriously restrict the cytological study of cephalopods. In a previous published paper, we gave a detailed overview of the existing cephalopod chromosome information, including the genetic relationship analysis based on evolutionary distance (Wang and Zheng 2017). The present study used gills as materials, and through a large number of repeated tests, the ideal metaphases with NORs and C-bands were obtained based on the previous study.…”

Genetic structure of Octopus minor around Chinese waters as indicated by nuclear DNA variations (Mollusca, Cephalopoda)

“…They have immense commercial and ecological significance, including a profound contribution as a source of protein for humans. The cephalopod has lobed and folded brain like that of vertebrates and are ingenious, migrant and largest of all molluscs (Mather and Kuba 2013; Cheng et al 2013; Larson et al 2015) and it is sensitive to environmental factors (Emery et al 2016; Wang and Zheng 2017…”