Ontogenetic variability in the external morphology of monkey goby, Neogobius fluviatilis (Pallas, 1814) and its relevance to invasion potential

Abstract

In the previous decade, four species of non-native gobies have invaded the middle section of the river Danube and its tributaries. An effective tool for understanding biological invasions is the evaluation of various biological traits (morphological, life history, ontogenetic) within an epigenetic context. The present study examines the external morphology of monkey goby Neogobius fluviatilis (Pallas, 1814) from the mouth of the River Hron, the morphological differences among three goby species (monkey, bighead and round) and the relevance of these differences for invasive potential. Monkey goby reach their definite phenotype very early in their ontogeny and thus represent a strongly precocial (specialized) species with direct development. The morphological differences between monkey and two other goby species also reflect its strong specialization for sandy substrata and smaller prey types. Thus, monkey goby are not expected to spread to new areas as fast as the round and bighead gobies, and their distribution is likely to be limited to sandy and/or sandy-gravel substrata. If this assumption is correct, then the potential adverse impact of monkey goby on native fauna or even ecosystem is likely to be less than that of the bighead and round gobies.

What can morphology tell us about ecology of four invasive goby species?

“…Such a result emphasizes the early acquisition of a definitive phenotype in P. gymnotrachelus and places this goby even closer to the specialist end of the continuum of alternative ontogenies (Balon, ), when compared with the other three goby species. A similar pattern in relative growth was found only in N. fluviatilis in which four characters demonstrate abrupt shifts in isometric growth and 22 from 36 characters grow isometrically (Čápová et al ., ).…”

“…The observed patterns of relative growth, with isometric growth predominating in most characters (30 from 36 characters; Tables and ) from as small as size 25 mm L S suggest that P. gymnotrachelus reach their definite phenotype early in ontogeny. This ontogenetic pattern has also been observed in N. fluviatilis , N. melanostomus and P. kessleri (Kováč & Siryová, ; Ľavrinčíková et al ., ; Čápová et al ., ) and it is typical for fishes with direct ontogeny ( i.e . species with limited or absent larva periods; Dmitrieva, ; Kalinina, ; Moiseyeva, ; Flegler‐Balon, ).…”

“…To analyse morphological differences between four species, a dataset containing raw data on all four species was created, using the data on 31 common morphometric characters for P. gymnotrachelus from this study and for N. melanostomus , P. kessleri and N. fluviatilis from previous studies (Kováč & Siryová, ; Ľavrinčíková et al ., ; Čápová et al ., ). This dataset was then transformed into residuals and subjected to canonical discriminant analysis (Sokal & Rohlf, ) using Statistica 7.0 software (http://www.statsoft.com).…”

“…The results are evaluated within an ontogenetic context and the morphological differences between the species are discussed to tackle the question: can special external shape adaptations help assess the invasive potential of each species? Data from previous studies on N. melanostomus , P. kessleri and N. fluviatilis (Kováč & Siryová, ; Ľavrinčíková et al ., ; Čápová et al ., ) were reanalysed, whereas a full examination of variability in external morphology of the P. gymnotrachelus is presented in this paper as an underlying objective.…”

First information on age and growth ofPadogobius bonelli(Bonaparte, 1846) outside of its native range: River Aggia (Central Italy)

“…Sexual dimorphism based on the larger size of males is reported as a typical trait of the species Gandolfi et al, 1991;Marconato et al, 1989). Among gobies, males are usually bigger than females, as noted in many other researches (Cápová et al, 2008;Filiz and Toðulga, 2009;Scalici and Gibertini, 2009;Borcherding et al, 2011;Gutowsky and Fox, 2011;Grul'a et al, 2012;Pompei et al, 2015b). Due to maleguarding behaviour, males of several gobies species, such as P. bonelli, may be subjected to a strong sexual selection because the larger males will occupy better nests Marconato et al 1989;Bobbio et al, 1990;Lugli et al, 1992;Scalici and Gibertini, 2009), obtaining a greater chance of attracting a female.…”