Chromosome diversity in Mediterranean and Antarctic euphausiid species (Euphausiacea)

• Published in: Journal of Crustacean Biology
• Main Authors: Thiriot-Quievreux, C, Leitao, A, Cuzin-Roudy, J
• Other Authors: Océanographie Biologique et Écologie du Plancton Marin (LOBEPM), Observatoire océanologique de Villefranche-sur-mer (OOVM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Inconnu
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 1998
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Antarctic; Antarc*; Euphausia superba; Meganyctiphanes norvegica; Thysanoessa macrura
• Online Access: https://hal.science/hal-03479820; https://doi.org/10.2307/1549322

Chromosome number and morphology were studied in gonadal tissue from eight euphausiid species, using an air-drying technique and Giemsa staining. Among Mediterranean species, haploid chromosome numbers were: n = 19 in Euphausia hemigibba, Euphausia brevis, and Nematoscelis megalops, n = 18 in Euphausia krohni, and n = 11 in Nyctiphanes couchi. Among Antarctic species, haploid chromosome numbers were: n = 17 in Euphausia superba, n = 20 in Thysanoessa macrura, and n = 13 in Thysanoessa vicina. Chromosome morphology was further studied for three species after chromosome measurements: Euphausia hemigibba karyotype showed 17 metacentric and 2 submetacentric chromosome pairs, Euphausia krohni 17 metacentric and 1 submetacentric chromosome pairs, and Nematoscelis megalops 17 metacentric and 2 submetacentric chromosome pairs. Three species sharing the same chromosome number of n = 19, i.e., Euphausia hemigibba, Nematoscelis megalops, and Meganyctiphanes norvegica were distinguished by a different slope of the decrease in chromosome size and by the presence/absence of metacentric and submetacentric chromosome pairs differing in number and position. Chromosome morphology of other species was derived from the observation of meiotic metaphases II. A majority of metacentric chromosomes was also displayed. Cytotaxonomic differences in haploid chromosome number allow the discrimination of morphologically neighboring sympatric species (e.g., Meganyctiphanes norvegica and Nyctiphanes couchi; Thysanoessa vicina and T. macrura). Euphausiids share common chromosomal features which clearly separate them from other eucarids, i.e., a narrow range of haploid chromosome number, a large chromosome size, and a majority of metacentric chromosomes.