Investigating population structure of Sea Lamprey (Petromyzon marinus, L.) in Western Iberian Peninsula using morphological characters and heart fatty acid signature analyses.

Maria João Lança,Catarina S Mateus,Bernardo R Quintella,Pedro R Almeida,Marta Lourenço,Maria Machado,Ana F Ferreira,David William Pond

doi:10.1371/journal.pone.0108110

Abstract

This study hypothesizes the existence of three groups of sea lamprey Petromyzon marinus L. in Portugal (North/Central group, Tagus group, and Guadiana group), possibly promoted by seabed topography isolation during the oceanic phase of the life cycle. Within this context, our purpose was to analyze the existence of a stock structure on sea lamprey populations sampled in the major Portuguese river basins using both morphological characters and heart tissue fatty acid signature. In both cases, the multiple discriminant analysis revealed statistically significant differences among groups, and the overall corrected classification rate estimated from cross-validation procedure was particularly high for the cardiac muscle fatty acid profiles (i.e. 83.8%). Morphometric characters were much more useful than meristic ones to discriminate stocks, and the most important variables for group differentiation were eye length, second dorsal fin length and branchial length. Fatty acid analysis showed that all lampreys from the southern Guadiana group were correctly classified and not mixing with individuals from any other group, reflecting a typical heart fatty acid signature. Our results revealed that 89.5% and 72.2% of the individuals from the Tagus and North/Central groups, respectively, were also correctly classified, despite some degree of overlap between individuals from these groups. The fatty acids that contributed to the observed segregation were C16:0; C17:0; C18:1ω9; C20:3ω6 and C22:2ω6. Detected differences are probably related with environmental variables to which lampreys may have been exposed, which leaded to different patterns of gene expression. These results suggest the existence of three different sea lamprey stocks in Portugal, with implication in terms of management and conservation.

Highlights

European populations of sea lamprey (Petromyzon marinus L.) have declined over the last 30 years [1], [2], and several authors have pointed out a reduction in sea lamprey abundance in Portuguese rivers [3], [4]
A limited record of 80 sea lampreys captured in the northwest Atlantic indicated that almost all individuals with less than 39 cm long where taken in bottom trawls on the continental shelf or in coastal trap nets, whereas most animals with more than 56 cm long were captured in mid-water trawls along the shelf edge or over the continental slope [6]
The total length (TL) and body total mass (TM) of the sampled lampreys ranged from 63.9 cm to 97.9 cm and from 770 g to 1806 g, respectively

Summary

Introduction

European populations of sea lamprey (Petromyzon marinus L.) have declined over the last 30 years [1], [2], and several authors have pointed out a reduction in sea lamprey abundance in Portuguese rivers [3], [4]. Sea lampreys can be found in all major Portuguese river basins, being more abundant in the central and northern regions of the country [3]. Whereas the continental phase of lampreys’ life cycle is well known, the oceanic phase remains a mystery, with available data resuming to a few accidental captures of host species with scars or, occasionally, lampreys still attached to the fish or cetaceans [5]. Evidence that sea lamprey might not show homing behaviour first emerged following a tagging study with a landlocked population of the Great Lakes [7], and was corroborated using genetic analysis on anadromous populations captured along the east coast of North America [8], [9]

Methods

Results

Conclusion