KARYOEVOLUTIVE CONSIDERATIONS in 29 MEDITERRANEAN TELEOST FISHES J Cano, G Thode, M Alvarez
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KARYOEVOLUTIVE CONSIDERATIONS IN 29 MEDITERRANEAN TELEOST FISHES J Cano, G Thode, M Alvarez To cite this version: J Cano, G Thode, M Alvarez. KARYOEVOLUTIVE CONSIDERATIONS IN 29 MEDITER- RANEAN TELEOST FISHES. Vie et Milieu / Life & Environment, Observatoire Océanologique - Laboratoire Arago, 1982, 32, pp.21 - 24. hal-03012268 HAL Id: hal-03012268 https://hal.sorbonne-universite.fr/hal-03012268 Submitted on 18 Nov 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. VIE MILIEU, 1982, 32 (I): 21-24 KARYOEVOLUTIVE CONSIDERATIONS IN 29 MEDITERRANEAN TELEOST FISHES J. CANO, G. THODE and M.C. ALVAREZ Departamento de Genetica, Facullad de Ciencias Universidad de Malaga, Spain ÉVOLUTION RÉSUMÉ. - Les données que nous avons obtenues pour 29 espèces de Téléostéens de CARYOLOCIE Méditerranée, ont été comparées avec celles apportées par d'autres auteurs sur des Poissons CONTENU EN ADN tropicaux afin d eclaircir les mécanismes earyoévolutifs possibles que ce grand groupe a CARYOTYPE suivis. C'est pourquoi le nombre et la morphologie chromosomique, de même que la TÉLÉOSTÉENS longueur totale du génome (LT), le contenu de DNA nucléaire et le coefficient de variation du caryotype sont analysés. ÉVOLUTION ABSTRACT. - The data we obtained in 29 Teleostean species from the Mediterranean KARYOLOGY are compared with those reported by other investigators about tropical fish, with the aim to DNA CONTENT elucidate the possible karyoevolutionary mechanisms that this wide group has followed. KARYOTYPE We also analyse both chromosome number and morphology, the total length of génome TELEOSTS (LT), the nuclear DNA content and the karyotype variation coefficient (CV). INTRODUCTION amount of DNA in the ancestral nucleus (Hinegardner & Rosen, 1972). In this way, some firm bases have been established to interprète the phenomena that occurred Karyological studies are used to distinguish species along the line of karyological évolution in fishes. and even populations, so a great number of possibilities exists for the analysis of evolutionary processes at the Goin and Goin (1968) as well as Ohno et al. (1969) chromosomal level. The discovery of the sex détermina- suggest that the ancestral forms of fishes might have tion mechanisms, or pathological phenomena are exam- suffered a polyploidization, which allowed the accumu- ples from this area of research. lation of a sufficient génome to initiate new directions of At the présent time there are about 20 000 known differentiation. This may be corroborated through ob- species of fish (Manna & Khuda-Bukhsh, 1977). Of servations of the wide range of DNA nuclear content thèse, about 2 000, mainly freshwater varieties, have variation, whose upper limit (140 pg.) is represented by been karyologically analyzed. It has been observed that the lung-fishes and the lower (0.4 pg.), by Teleosts (Hi- a great number of Teleosts présents a chromosomal negardner, 1976). Hinegardner (1968) considers that the diploid number of 2n = 48. This is considered by Ohno species with the lowest DNA content are farther evol- and Atkin (1966) and Ohno (1970) as the ancestral ved; he also suggests that in the beginning of each karyotype of ail fish, which is only represented by evolutionary line there would be an increase of the gene acrocentric chromosomes and a content of nuclear DNA (by way of duplications or polyploidy). Further- DNA in about 20 96 ( = 1.3 picograms) of the placental more, associated with the specialization or adaptation to mammals. Following this assumption, différent varia- a more restricted habitat there is a graduai decrease. tions occurred, namely : duplications, polyploidy, dele- This opinion is also expressed by Bachman et al. (1974). tions or Robertsonian translocations, which gave place On the other hand, it seems that pericentric inver- to increases and/or réductions in the primitive chromo- sions are the principal mechanisms involved in the évo- somal numbers (Atkin & Ohno, 1967) as well as in the lution of the karyotype, which produce changes in the 22 J. CANO, G. THODE AND M.C. ALVAREZ chromosome arm numbers (Chiarelli & Capanna, 1973). chromosome length - which shows the degree of the The rearrangements of the Robertsonian type (centric karyotype heterogeneity. An homogeneus karyotype has fusion and fission) change the number of chromosomes, a CV close to zéro, and as it becomes more and more but they maintain a constant number of arms. There are heterogeneus, it will show a value nearer to 0.5. The différent opinions about the incidence of thèse mecha- CV of the species here studied are given in Table I. nisms on fish karyotypical évolution ; but most authora- The parameters we have considered (Table I), suggest tive opinions insist that in an evolutionary lineage (i.e. that the Pomacentridae and Mugilidae are karyologically between species of the same genus) the tendency exists the least evolved, the former because of their 48 acro- to reduce the number of chromosomes or to increase centric chromosomes (FN = 48) of a simillar size; the the arm number (NF), so that the species with ail the low CV as well as the high DNA content (1.2 pg.) acrocentric chromosomes would in karyotypical terms indicate its proximity to the ancestral karyotype, of be more primitive (Ohno & Atkin, 1966 ; Hsu & Arrighi, which it may have been derived through paracentric 1968; Chiarelli & Capanna, 1973; White, 1973...). Ge- inversions and a few génome variations (Alvarez, Cano nerally there is a positive corrélation between DNA and Thode, 1980). The tropical représentatives in this nuclear content increase and the increase of chromo- family (Arai and Inoue, 1976) generally show and in- some number. crease in the basis number, which may be due to The object of this work is to provide new karyoevo- pericentric inversions, since in thèse the chromosomal lutionary data from a few species of Teleosts in the number is maintained constant. The Mugilidae, with a Mediterranean, and to establish a comparison between karyotype morphologically similar to the ancestral form them and their nearest relatives in the tropical seas. show a trend to the development of biarmed chromoso- mes ; this in Liza aurata, which has a pair of subtelo- centric chromosomes. With regard to their DNA content, a réduction is observed compared to the Poma- MATERIAL AND METHODS centrids. The tropical species seem to follow this rule, according to Hinegardner (1976), Hunt and Fitzsimons (1976) and Choudhury et al., (1979). To realize this study we have analyzed both maies and females of 29 species, belonging to 9 différent The Serranids we have analyzed présent a karyotype teleost families, typical of the rocky littoral. Ail Spéci- close to the afore mentioned groups. Nevertheless, the mens have been captured along the Malaga coast. low nuclear DNA content seems to indicate a great specialization. The tropical représentatives of this family Metaphase plates have been obtained following the (Hinegardner and Rosen, 1972; Ueno et al., 1977 and technique described by Capanna and Cataudella (1972), Rachlin et al., 1978) show a greater FN and a higher which has been slightly modified. For the karyotype DNA content. analysis a sélection was made of at least 30 mitotic metaphases for each species. In the only studied species belonging to the family Mullidae, there is a low DNA content combined with a We determined the nuclear DNA content from ery- high CV, which suggests that it is derived from the throcytes, dying them with the usual Feulgen's procé- ancestral karyotype through translocations and génome dure and comparing them with blood cells of chicken. losses. We used a Vickers M-8 5 integrating microdensitometer. The measurements were made at a wavelength of A group with karyological characteristics similar to 550 nm, and a band width of 50 nm. The arbitrary Serranids and Mullids is the Family Sparidae, which in unities we obtained, from 24 readings for each species, its whole is rather homogeneous, since it maintains the have been transformed into picograms. same diploid number, a FN between 52 and 58 and a nuclear DNA content between 0.52 and 0.65 pg. Tropi- cal species also form an homogeneous group with re- gard to DNA content (according to Hinegardner and RESULTS AND DISCUSSION Rosen, 1972). Most of the karyoevolutionary mechanisms mentio- The results obtained and the corresponding relations ned converge in the family Bleniidae (Cano et al., of the analyzed species are summarized in Table I. The 1981). On the other hand, the diversity of the values data about the families Pomacentridae, Serranidae, Spa- found in CV of thèse species is a reflection of the ridae, Labridae, Blenniidae and Gobiidae were discussed numerous chromosome rearrangements occurred in their in earlier publications, but they are included here along évolution. So we consider that this group is karyologi- with new data in order to corroborate the karyo- cally more speciallized. This hypothesis is corroborated by the différent karyotypes described by Arai and Shiot- evolutionary mechanisms in Teleosts. suki (1973) and Nishikawa and Sakamoto (1978) in We introduced a new parameter in order to quantify tropical species. the size variations within the chromosomes of a karyo- type ; this is the "variation coefficient" (CV - as a resuit The highest level of complexity, from a karyological of dividing the standard déviation (SD) by the average point of view, is observed in the family Gobiidae, be- TELEOST KARYOLOGICAL EVOLUTION 23 Tabl. I. - Karyological characteristics of the studied species. Caractéristiques caryologiques des espèces étudiées.