Gammarus:ImportantTaxoninFreshwaterand ... · show that both pulses of wash water from a watercress farm and isolated phenethyl isothiocyanate (PEITC) can inﬂuence the reproductive

Hindawi Publishing CorporationInternational Journal of ZoologyVolume 2011, Article ID 524276, 2 pagesdoi:10.1155/2011/524276

Editorial

Gammarus: Important Taxon in Freshwater andMarine Changing Environments

Almut Gerhardt,1 Michelle Bloor,2 and Chris Lloyd Mills3

1 LimCo International GmbH, Technologiezentrum Konstanz, Blarerstrβe 56, 78462 Konstanz, Germany2 School of Earth and Environmental Science, University of Portsmouth, Burnaby Building, Burnaby Road,Portsmouth PO1 3QL, UK

3 School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, UK

Correspondence should be addressed to Almut Gerhardt, [email protected]

Received 19 June 2011; Accepted 19 June 2011

Copyright © 2011 Almut Gerhardt et al. This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.

Gammarus spp. consist of more than 100 freshwater, brack-ish, and marine species in the Northern hemisphere. Theyrepresent important keystone species in aquatic ecosystemsand are often present in high abundance. As shredders anddetritus feeders, they contribute to the detritus cycle andthe microbial loop. Gammarids are also carnivorous, feedingon small invertebrates and carrion. Due to their widespreaddistribution, significance in the food web, and sensitivity toa wide range of pollutants, they are important bioindicatorsfor water quality assessment. Gammarus spp. are ecologicallyhighly successful due to the following characteristics: widetrophic repertoire and foraging plasticity, migration abilityand tendency to drift, which allows them to easily invade andcolonize ecosystems, high reproductive capacity with severalbroods per female per year, and a high number of offspringand relatively longevity (1-2 yrs).

Gammarus spp. and their American relative Hyalellaazteca are standard test species in ecotoxicity testing in theUSA and UK. A new OECD test guideline is currently beingprepared for gammarids, which will consist of a variety ofin situ and ex situ ecotoxicological studies based on differentmeasurement parameters.

The evolution of gammarids is particularly interesting:gammarids contain several Ponto-Caspian and Atlantic inva-sive species, which have spread throughout Europe. Somespecies are currently being divided into several geographicalforms. Although the genome of Gammarus pulex has yetto be sequenced, 12345 expressed sequence tags are known,

which might be the basis for future innovative knowledge intaxonomy and toxicogenomics.

Despite the taxon’s importance in different fields of biol-ogy (e.g., ecology, evolution, ecotoxicology, taxonomy, bio-geography), its application (as test species and bioindicators)in scientific research tends to consider isolated questions. Theaim of this special issue on Gammarus spp. is to highlightthe importance of this taxon and facilitate interdisciplinaryresearch. The focus of this issue is to present articles thatshowcase different facets of gammarid research, includingmethods that demonstrate direct practical approaches. Inorder to reach a wide spectrum of readers from differentdisciplines and geographical regions, we chose this journalwith global open access.

Gammarids are known to be important shredders inthe aquatic detritus cycle and the microbial loop. Themost recent research within the field of gammarid-microbialinteractions is summarized and discussed in the first articleby D. Nelson. Gammarids prefer so-called conditioned leavesas food, that is, leaves colonized by a microbial biofilm.The role of hyphomycete fungi as a source of secondarymetabolites is stressed in the paper. However, although theeffects of leaf type and microbial colonization on Gammarusspp. feeding activity, growth, and survival has been studied,the effects of Gammarus spp. on shaping the microbialcommunity still remain unknown.

Understanding dietary requirements of gammarids isessential knowledge to describe feeding schemes for a

2 International Journal of Zoology

successful laboratory culture. M. Bloor tests unconditionedand conditioned (either naturally conditioned or artificiallyconditioned) alder leaves as a food source for Gammaruspulex and Asellus aquaticus and concludes that both speciesprefer naturally conditioned leaves compared to artificialconditioning. M. Bloor provides a simple method to preparealder leaves for laboratory culturing of both species. Success-ful breeding is an essential requisite for a standard test speciesin ecotoxicological test procedures.

A. Gerhardt presents a simple low-cost test system withGammarus spp. studying survival, feeding, and behaviour aswell as biomarkers, to be used both in and ex situ. This testprotocol does not need sophisticated laboratory equipmentand hence can be applied worldwide. Compared to thestandard test species Daphnia magna, gammarids tend tobe as sensitive towards toxicants and are more ecologicallyrelevant test species. We hope to increase the applicationof gammarids in aquatic ecotoxicology by providing simplemethods for breeding, feeding, and test systems.

Whilst gammarids can be very sensitive towards pesti-cides, they are also susceptible to natural defence substancesreleased by aquatic plants. M. J. Dixon and P. J. Shawshow that both pulses of wash water from a watercressfarm and isolated phenethyl isothiocyanate (PEITC) caninfluence the reproductive behaviour of Gammarus pulex.Short-term pulses lead to the interruption of precopula pairs,with recovery occurring in clean water. Such a transientbehavioural parameter has the potential to be used as an earlywarning indicator of pulsed pollution stress.

A sound basis for every ecological and ecotoxicologicalstudy is species determination. In gammarids several crypticspecies have been found based on genetic methods. However,the proof of mechanisms in speciation such as geograph-ical and/or ecological isolation is still lacking. Do geneticdifferences suffice to describe (sub)species, or do we needa combination of genetic, morphological, and ecologicalmethods? Haug et al. present the most recent methods forimaging gammarids from whole animals to tiny structuresusing both high- and low-cost techniques. Modern imagingmethods in combination with sophisticated software are verypowerful tools which facilitate taxonomic determination. Inthis paper, different techniques are presented, from simplelight microscopy with staining techniques, autofluorescence,and polarized light applications to focused ion beam scan-ning electron microscopy, confocal laser microscopy, andmicrotomography.

Although most gammarids represent freshwater Gam-marus species, brackish and marine gammarids have recentlybeen studied in more detail. L. Delgado et al. show thatboth adult and juvenile Gammarus aequicauda have a widesalinity tolerance range and that juvenile growth rate is onlyaffected towards the extremes of the salinity tolerance range.Ecological plasticity is a prerequisite to spread to differenthabitats and geographical locations. Gammarids are highlysuccessful in this aspect.

A. Mirzajani et al. describe selection of gammarid speciesfor potential use as a natural food source for warm water fishfarming in Iran. In this interesting approach the reproductivetraits of 7 amphipod species have been studied with respect

to their breeding periods and reproductive output. Theyidentified 4 species that might be suitable for warm water fishaquaculture.

Almut GerhardtMichelle Bloor

Chris Lloyd Mills

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Gammarus:ImportantTaxoninFreshwaterand ... · show that both pulses of wash water from a watercress farm and isolated phenethyl isothiocyanate (PEITC) can inﬂuence the reproductive