Cytogenetic analysis and chromosomal characteristics of the polymorphic 18S rDNA of Haliotis discus hannai from Fujian, China

Lipid Profiling of Pacific Abalone (Haliotis discus hannai) at Different Developmental Stages Using Ultrahigh Performance Liquid Chromatography-Tandem Mass Spectrometry

Pacific abalone (Haliotis discus hannai) is a commercially important mollusk; therefore, improvement of its growth performance and quality has been emphasized. During embryonic development, abalones undergo a series of distinct larval stages, including swimming veliger larvae, juveniles, and mature individuals, and their biomolecular composition varies depending on the developmental stage. Therefore, in the present study, we performed untargeted lipid profiling of abalone tissues at different developmental stages as well as the hemolymph of mature female and male abalones using ultrahigh-performance liquid chromatography-tandem mass spectrometry. These profiles can provide meaningful information to understand compositional changes in lipids through abalone metamorphosis and development. A total of 132 lipids belonging to 15 classes were identified from abalone tissues at different developmental stages. Moreover, 21 lipids belonging to 8 classes were identified from the hemolymph of mature abalones. All data were processed following strict criteria to provide accurate information. Triglycerides and phosphatidylcholines were the major lipid components identified in both tissues and hemolymph, accounting for, respectively, 27% and 15% of all lipids in tissues and, respectively, 24% and 38% of all lipids in the hemolymph. Of note, lysophosphatidylcholine was only detected in the tissues of mature abalones, paving the way for further analyses of abalone lipids based on developmental stages. The present findings offer novel insights into the lipidome of abalone tissues and hemolymph at different developmental stages, building a foundation for improving the efficiency and quality of abalone aquaculture.

Non-lethal method for the preparation of metaphase spreads using cultured mantle tissue from live adult abalone

Metaphase spread preparation in adult abalone has not been successful, which has restricted the applications of karyotyping-based technologies. Here, we present a non-lethal method to enable preparation of metaphase spreads from live adult abalone using a tissue culture method. Mantle tissue fragments from live adult abalone were cultured in vitro and the cultured cells were used for metaphase spread preparation. To retrieve a sufficient number of proliferating cells required for metaphase spread preparation, at least 14 days of culture was required, and culturing the marginal zone of mantle was more optimal than culturing other areas. Additionally, it was shown that simple medium consisting of basal medium, fetal bovine serum and antibiotics could stimulate cellular proliferation followed by metaphase spread preparation.

Cytogenetic studies in three octopods, Octopusminor, Amphioctopusfangsiao, and Cistopuschinensis from the coast of China

To provide markers to identify chromosomes in the genome of octopods, chromosomes of three octopus species were subjected to NOR/C-banding. In addition, we examined their genome size (C value) to submit it to the Animal Genome Size Database. Silver staining revealed that the number of Ag-nucleoli was 2 (Octopusminor (Sasaki, 1920)), 2 (Amphioctopusfangsiao (d'Orbigny, 1839)) and 1 (Cistopuschinensis Zheng et al., 2012), respectively, and the number of Ag-nucleoli visible was the same as that of Ag-NORs on metaphase plates in the same species. In all analyzed metaphases, Ag-NORs were mainly located terminally on the long arms of chromosomes 3 (3^rd) of O.minor and on the short arms of chromosomes 4 (4^th) of A.fangsiao, whereas only one of the chromosomes 23 (23^rd) was found Ag-NORs of C.chinensis. C-bands were localized predominantly in the centromeric regions of chromosomes in the three species, while other conspicuous stable C-bands were observed in terminal regions, including the Ag-NORs. That means these three chromosome pairs (3^rd, 4^th and 23^rd) could be considered species-specific cytogenetic markers. The mean C values of O.minor, A.fangsiao and C.chinensis were 7.81±0.39 pg (0.070 pg per unit length), 8.31±0.18 pg (0.068 pg per unit length) and 5.29±0.10 pg (0.038 pg per unit length), respectively, and results showed that C values of the three species were not proportional to the relative length of the chromosomes. These cytogenetic characteristics will provide more theoretical foundation for further researches on chromosome evolution in octopods.

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

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 (D_e ) 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 (D_e =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 D_e and λ provides information to supplement traditional taxonomy and molecular systematics, and it would serve as an important auxiliary for routine phylogenetic study.