Conventional karyotype, nucleolar organizer regions and genome size in five Mediterranean species of Syngnathidae (Pisces, Syngnathiformes)

Abstract

Conventional karyotypes, NOR-bearing chromosomes by means of silver impregnation and genome size were investigated in five Mediterranean species in three genera of the Syngnathidae. A karyotype of 48 subtelocentric-acrocentric chromosomes was found in the seahorse Hippocampus hippocampus (FN=48) while a diploid value of 44 occurred in H. guttulatus (2 sm-m+42 a; FN=46) and the pipefish Syngnathus abaster (44 a; FN=44) and S. typhle (44 a; FN=44). The pipefish Nerophis ophidion, possessing a diploid chromosomal set of 58 made up of 50 meta-submetacentric and eight subteloacrocentric elements (FN=108) and a genome size three to four times larger than those known to date, differs cytogenetically from all other Syngnathids studied so far. A single pair of active NOR-bearing chromosomes was found in both species of the genus Hippocampus while in Syngnathus and Nerophis species more than two silver positive chromosomes were found to be involved in nucleolus organization giving rise to NOR-bearing chromosome polymorphism. The possible evolutionary routes of quantitative and qualitative changes in chromosome and DNA are discussed. The resulting phylogenetic scheme is shown to coincide with that constructed from morphological characters. 1998 The Fisheries Society of the British Isles

The Dynamics of Male Brooding, Mating Patterns, and Sex Roles in Pipefishes and Seahorses (Family Syngnathidae)

“…Our phylogeny suggests that the primary split between these two lineages occurred at the same time or shortly before the major morphological radiation of male brooding structures and subsequent radiation of species (Wilson et al 2001). The early diversification of the ancestral syngnathid into tail and abdominal brooders is consistent with results from a karyotypic study, which highlights a possible total-genome duplication in the abdominal-brooding lineage (Vitturi et al 1998). Brooding structures within these two lineages independently increased in complexity, culminating in the completely enclosed brood pouches located on the tail of seahorses (Herald 1959; type A5) and the well-defined abdominal pouch of Oostethus brachyrus (type B3), the most complex abdominal pouch type.…”

Conventional karyotype and nucleolar organizer regions of the toadfish <i>Halobatrachus didactylus</i> (Schneider, 1801) (Pisces: Batrachoididae)

“…According to Schmidt (1978: in Vitturi et al, 1998, a single pair of NORbearing chromosomes represents a primitive condition in most vertebrate species. It is difficult to make comparisons within Batrachoidid species since no reports including data on NORs for toadfish are available.…”

Molecular Cytogenetic Evidence of Rearrangements on the Y Chromosome of the Threespine Stickleback Fish

“…The same study found evidence for a ZW sex chromosome system in a more distantly related stickleback species, Apeltes quadracus (Chen and Reisman 1970). In contrast, no heteromorphic sex chromosome pairs have been reported in the outgroup family Syngnathidae (Vitturi et al 1998;Libertini et al 2006). The existence of different sex chromosome systems within the stickleback family, along with the availability of genetic resources and the complete genome sequence of the female threespine stickleback (Peichel et al 2001;Kingsley et al 2004;Kingsley and Peichel 2007) make this fish a compelling vertebrate system in which to study sex chromosome evolution.…”