Francisco Otero-Ferrer

Species identification and genetic structure of threatened seahorses in Gran Canaria Island (Spain) using mitochondrial and microsatellite markers

A non-invasive DNA analysis of seahorse populations was carried out after extensive underwater surveys in Gran Canaria Island (Spain). In this geographical area, the presence of two species, Hippocampus hippocampus and H. guttulatus, has been previously reported. Sequencing of 16S ribosomal DNA (16S rDNA) was used for specific identification of live seahorses sampled in situ, as a previous step to evaluate genetic structure based on ten microsatellite markers. Phylogenetic analyses revealed the presence of a single species, H. hippocampus, in the seahorse communities found at Gran Canaria. No evidences of H. guttulatus or interspecific hybrids were found based on 16S rDNA and microsatellite data. The nuclear markers revealed low genetic diversity and lack of population structure across populations of Gran Canaria Island, with evidence of small population sizes. This study provides critical information to support conservation strategies of Gran Canaria seahorses.

Embryonic developmental plasticity in the long-snouted seahorse (Hippocampus reidi, Ginsburg 1933) in relation to parental preconception diet

The aim of the present study was to investigate the hypothesis that parental periconception nutrition in adult seahorses affects the development and growth of their offspring. We tested the hypothesis that because seahorse embryos develop inside the males brood pouch, manipulation of the males diet would affect offspring growth and development independently of the females diet. Adult males and females were fed separately with either wild-caught crustaceans or commercial aquarium diet for 1 month before conception to influence the periconception environment. Approximately 10000 offspring were obtained from four different treatment groups (Male/Wild or Male/Commercial×Female/Wild or Female/Commercial). Weights, physical dimensions and fatty acid profiles of the newborns were determined. Offspring produced when the males receiving commercial diet were mated with wild-fed females were larger (P<0.05) than those produced by wild-fed males. When both males and females were fed with commercial diet, their offspring were significantly smaller than those from the other treatment groups. When commercial diet-fed females were mated with wild-fed males, the offspring showed distortion of the snout:head length ratio. These results support the view that the preconception diet received by males and females differentially affects embryonic development.

First records of Hippocampus algiricus in the Canary Islands (north-east Atlantic Ocean) with an observation of hybridization with Hippocampus hippocampus.

Morphometric and genetic analyses confirmed the first records of the West African seahorse Hippocampus algiricus at Gran Canaria Island (north-east Atlantic Ocean), and also the first evidence of interspecific hybridization in seahorses. These results provide additional data on the distribution of H. algiricus that may help to establish future conservation strategies, and uncover a new potential sympatric scenario between H. algiricus and Hippocampus hippocampus.

When natural history collections reveal secrets on data deficient threatened species: Atlantic seahorses as a case study

Natural history collections from museums and private institutions can play an important role supporting decisions in biodiversity conservation. Seahorse populations have suffered a worldwide decline, while many areas remain data deficient including areas subjected to heavy commercial trading, such as the coasts of West Africa. In this work, seahorse collections from museums and public institutions in Macaronesia (Azores, Madeira and the Canary Islands) were initially reviewed (1) to identify specimens not previously determined, and (2) to correct species determinations from Macaronesia and adjacent West African coasts. The morphological data (3) were tested for phenotypic variation of seahorses within and between Macaronesia and adjacent West African coasts. The presence of Hippocampus hippocampus (short-snouted seahorse) and Hippocampus algiricus (West African seahorse) was confirmed for the area, including new sightings along previous geographical distribution ranges. Morphological analyses partitioned seahorse species and several morphotypes within and between Macaronesia and adjacent West African coasts. This phenotypic plasticity was associated with cranial morphology. Such differences are a useful tool for tracking seahorse populations of varying species and origins. New information presented here, is valuable for improving the management and conservation of seahorses, particularly in areas threatened by illegal trading or other anthropogenic activities.

Parallel use of a shared genomic island of speciation in clinal and mosaic hybrid zones between cryptic seahorse lineages

Diverging semi-isolated lineages either meet in narrow clinal hybrid zones, or have a mosaic distribution associated with environmental variation. Intrinsic reproductive isolation is often emphasized in the former and local adaptation in the latter, although both can contribute to isolation. Rarely these two patterns of spatial distribution are reported in the same study system, while this could provide fundamental information on the endless debate about the relative contribution of intrinsic reproductive isolation and local adaptation on the speciation process. Here we report that the low diversity long-snouted seahorse Hippocampus guttulatus is genetically subdivided into five cryptic semi-isolated lineages. Along the Atlantic coasts, northern and southern lineages meet and coexist with little hybridization in the southwest of France, forming a clinal hybrid zone. In the Mediterranean Sea, two lineages have a mosaic distribution associated with lagoon-like and marine habitats. A fifth lineage was identified in the Black Sea. Genetic homogeneity over large spatial scales within each lineage, together with among-locus variance in differentiation levels between lineages and spatial patterns of introgression provide evidence that partial reproductive isolation is maintaining the divergence. Surprisingly, the North Atlantic and the Mediterranean lagoon lineages are genetically similar for a single chromosome-wide island showing parallel genetic differentiation among regions. Since Atlantic lineages distribution lacks association with habitat variation, genetic parallelism suggests that a shared genomic barrier contributes to reproductive isolation in contrasted contexts - i.e. spatial vs. ecological. We discuss how a genomic hotspot of parallel differentiation could have evolved and become associated either with space or with a patchy environment in a single study system.Diverging semi-isolated lineages either meet in narrow clinal hybrid zones, or have a mosaic distribution associated with environmental variation. Intrinsic reproductive isolation is often emphasized in the former and local adaptation in the latter, although both can contribute to isolation. Rarely these two patterns of spatial distribution are reported in the same study system. Here we report that the long-snouted seahorse Hippocampus guttulatus is subdivided into discrete panmictic entities by both types of hybrid zones. Along the European Atlantic coasts, a northern and a southern lineage meet in the southwest of France where they coexist in sympatry with little hybridization. In the Mediterranean Sea, two lineages have a mosaic distribution, associated with lagoon-like and marine habitats. A fifth lineage was identified in the Black Sea. Genetic homogeneity over large spatial scales contrasts with isolation maintained in sympatry or close parapatry at a fine scale. A high variation in locus-specific introgression rates provides additional evidence that partial reproductive isolation must be maintaining the divergence. Surprisingly, fixed differences between lagoon and marine populations in the Mediterranean Sea belong to the most differentiated SNPs between the two Atlantic lineages, against the genome-wide pattern of structure. These parallel outlier SNPs cluster on a single chromosome-wide island of differentiation. Since Atlantic lineages do not match the lagoon-sea habitat variation, genetic parallelism at the genomic island suggests a shared genetic barrier contributes to reproductive isolation in contrasting contexts -i.e. spatial vs. ecological. We discuss how a genomic hotspot of parallel differentiation could have evolved and become associated either with space or with a patchy environment in a single study system.