DOCSLIB.ORG

Is the Aquatic Dikerogammarus Villosus a 'Killer Shrimp'

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Is the Aquatic Dikerogammarus Villosus a 'Killer Shrimp' Is the aquatic Dikerogammarus villosus a ‘killer shrimp’ in the field? – a case study on one of the most invasive species in Europe Dr. Meike Koester1,2, Bastian Bayer1 & Dr. René Gergs3 1Institute for Environmental Sciences, University of Koblenz-Landau, Campus Landau, Germany 2Institute of Natural Sciences, University of Koblenz-Landau, Campus Koblenz, Germany 3Federal Environment Agency, Berlin, Germany Introduction 143 animal 58 invasive 2 Introduction Bij de Vaate et al. (2002) 3 Introduction 1994/95 first record from the River Rhine Colonised most major European rivers within 2 decades www.aquatic-aliens.de 4 Introduction Larger than native amphipods High reproductive potential & growth rate Colonises different substrates Highly tolerant towards various environmental conditions (e.g. T, O2, salinity) Feeding behaviour 5 Introduction River Rhine species of number Mean Schöll, BfG-report Nr. 172 other gamarids Dikerogammarus villosus Gammarus roeselii Gammarus pulex/fossarum after Rey et al. 2005 6 Introduction 7 Hypothesis D. villosus is also strongly predacious in the field 8 Stable Isotope Analyses (SIA) 12 13 Carbon C C 13C/12C 98,89 % 1,11 % 14 15 Nitrogen N N 15N/14N 99,64 % 0,36 % δ15N: strong accumulation Predator 1 Trophic Level ca. 3.4 ‰ Secondary consumer N 13 15 δ C: less accumulated δ Primary consumer C-source of the food Producer δ13C 9 Sampling areas of the River Rhine and its tributaries B Bulk analyses δ13C and δ15N SIBER-Analyses comparing amphipod species Genetic gut content analyses with group-specific C B rDNA primers (Koester Aet al. 2013) A C 10 A. Feeding river vs. Lake Constance 14 Feeding river Lake Constance n = 21 8 n = 21 12 1 × Ephemera sp. 1 × Ephemeroptera 5 × Caenis sp. 7 N 10 15 1 × Heptageniidae 3 × Heptageniidae δ 6 8 2 × Asellus aquaticus 3 × Gammarus sp. 6 5 -32 -31 -30 -29 -28 -27 -26 -25 -30 -25 -20 -15 δ13C Dikerogammarus villosus Caenis sp. Limnomysis benedeni Echinogammarus berelloni Chironominae Potamopyrgus antipodarum + Gammarus roeselii Dreissena polymorpha Simuliidae Asellus aquaticus Hydropsyche sp. Characea sp. Bithynia tentaculata Hirudinae Periphyton Seston 11 B. Upper Rhine vs. Lower Rhine 12 Upper Rhine 16 Lower Rhine n = 20 15 n = 20 10 14 N 15 8 13 δ 3 × Ephemera sp. 1 × Chelicorophium sp. 12 6 11 4 10 -28 -26 -24 -22 -20 -18 -32 -30 -28 -26 -24 δ13C Dikerogammarus villosus Potamopyrgus antipodarum Echinogammarus ischnus Periphyton Corbicula fluminea Seston Jaera sarsi 12 C. Invasion front vs. Established 9 Invasion front Established 10 8 n = 32 from two sites n = 20 9 7 8 N 6 15 δ 7 5 1 × Ephemeroptera 1 × Jaera sarsi 6 1 × Ephemeroptera 4 5 3 -34 -32 -30 -28 -26 -32 -30 -28 -26 -24 -22 -20 δ13C Dikerogammarus villosus Diamesinae Echinogammarus ischnus + Gammarus fossarum Simuliidae Dreissena rostriformis × Gammarus pulex Orthocladiinae Jaera sarsi G. pulex/G. fossarum Rhyacophila sp. Potamopyrgus antipodarum Ancylus fluviatilis Periphyton Seston 13 Isotopic niche width D. villosus 5 A B C * 4 3 Area (‰²) Area 2 1 0 - Feeding river Lake Constance Upper Rhine Lower Rhine Invasion front Estab lished 14 Conclusion Hypothesis D. villosus is also strongly predacious in the field ‘killer shrimp’? less predatory in the River Rhine system supported by SIA and genetic analyses – apparently not more opportunistic at an invasion front 15 Thanks… … for your attention … to Andreas Hirsch … to Peter Rey, Uta Mürle and Johannes Ortlepp … and numerous other people Need more details? [email protected] 16 .
Load more

Recommended publications
  • The Killer Shrimp, Dikerogammarus Villosus (Sowinsky, 1894), Is Spreading in Italy
    Aquatic Invasions (2010) Volume 5, Issue 2: 211-214 This is an Open Access article; doi: 10.3391/ai.2010.5.2.14 Open Access © 2010 The Author(s). Journal compilation © 2010 REABIC Short communication The killer shrimp, Dikerogammarus villosus (Sowinsky, 1894), is spreading in Italy Elena Tricarico, Giuseppe Mazza, Gabriele Orioli, Claudia Rossano, Felicita Scapini and Francesca Gherardi* Dipartimento di Biologia Evoluzionistica “Leo Pardi”, Università di Firenze, via Romana 17, 50125 Firenze, Italy E-mail: [email protected] (ET), [email protected] (GM), [email protected] (GO), [email protected] (CR), [email protected] (FS), [email protected] (FG) * Corresponding author Received: 23 November 2009 / Accepted: 11 January 2010 / Published online: 21 January 2009 Abstract In 2008, the killer shrimp, Dikerogammarus villosus, native to the Ponto-Caspian region, was found for the first time in Central Italy, in Bilancino, an artificial lake situated in the watershed of the River Arno (Tuscany). This new record shows that this species’ range is expanding in Italy. It is thus imperative to identify the pathways and vectors of spread of this species in order to halt this invasion process. Key words: Dikerogammarus villosus, inland waters, Italy Because of its predatory voracity and aggressive Devin et al. 2003; Brooks et al. 2009) and adapts behaviour, Dikerogammarus villosus (Sowinsky, to several types of substrate (Devin et al. 2003), 1894) is called the ‘‘killer shrimp’’. It is a favoured in this by its polymorphic pigmentation crustacean amphipod native to the Ponto-Caspian (Devin et al. 2004a). Its aggressive behaviour region. After the opening of the Danube-Main- and voracity cause the replacement of indigenous Rhine canal in 1992, as the result of both natural gammarids (Dick and Platvoet 2000; Van Riel et expansion and transportation in ballast waters al.
    [Show full text]
  • Seasonal Diet Pattern of Non-Native Tubenose Goby (Proterorhinus Semilunaris) in a Lowland Reservoir (Mušov, Czech Republic)
    Knowledge and Management of Aquatic Ecosystems (2010) 397, 02 http://www.kmae-journal.org c ONEMA, 2010 DOI: 10.1051/kmae/2010018 Seasonal diet pattern of non-native tubenose goby (Proterorhinus semilunaris) in a lowland reservoir (Mušov, Czech Republic) Z. Adámek(1),P.Jurajda(2),V.Prášek(2),I.Sukop(3) Received March 18, 2010 / Reçu le 18 mars 2010 Revised May 21, 2010 / Révisé le 21 mai 2010 Accepted June 3rd, 2010 / Accepté le 3 juin 2010 ABSTRACT Key-words: The tubenose goby (Proterorhinus semilunaris) is a gobiid species cur- Gobiidae, rently extending its area of distribution in Central Europe. The objective food, of the study was to evaluate the annual pattern of its feeding habits in lowland the newly colonised habitats of the Mušov reservoir on the Dyje River (the reservoir, Danube basin, Czech Republic) with respect to natural food resources. rip-rap bank, In the reservoir, tubenose goby has established a numerous population, the Dyje River densely colonising stony rip-rap banks. Its diet was exclusively of an- imal origin with significant dominance of and preference for two food items – chironomid (Chironomidae) larvae and waterlouse (Asellus aquati- cus), which contributed 40.2 and 27.6%, respectively, to the total food bulk ingested. The index of preponderance for the two items was also very high, amounting to 73.8 and 26.5, respectively. In the annual pat- tern, a remarkable preference for chironomid larvae was recorded in the summer period whilst waterlouse were consumed predominantly in win- ter months. The proportion of other food items was rather marginal – only corixids, copepods, ceratopogonids and cladocerans were of certain mi- nor importance with proportions of 5.4, 4.3, 4.1 and 3.9%, respectively.
    [Show full text]
  • Guide to Crustacea
    38 Guide to Crustacea. This is a very large and varied group, comprising numerous families which are grouped under six Sub-orders. In the Sub-order ASELLOTA the uropods are slender ; the basal segments of the legs are not coalesced with the body as in most other Isopoda ; the first pair of abdominal limbs are generally fused, in the female, to form an operculum, or cover for the remaining pairs. This group includes Asellus aquaticus, which is FIG. 23. Bathynomus giganteus, about one-half natural size. (From Lankester's "Treatise on Zoology," after Milne-Edwards and Bouvier.) [Table-case No. 6.] common everywhere in ponds and ditches in this country, and a very large number of marine species, mostly of small size. The Sub-order PHKEATOICIDEA includes a small number of very peculiar species found in fresh water in Australia and New Zealand. In these the body is flattened from side to side, and Peraca rida—Isopoda. 39 the animals in other respects have a superficial resemblance to Amphipoda. In the Sub-order FLABELLIFERA the terminal limbs of the abdomen (uropods) are spread out in a fan-like manner on each side of the telson. Many species of this group, belonging to the family Cymothoidae, are blood-sucking parasites of fish, and some of them are remarkable for being hermaphrodite (like the Cirri- pedia), each animal being at first a male and afterwards a female. Mo' of these parasites are found adhering to the surface of the body, behind the fins or under the gill-covers of the fish. A few, however, become internal parasites like the Artystone trysibia exhibited in this case, which has burrowed into the body of a Brazilian freshwater fish.
    [Show full text]
  • A Review of Potential Methods to Control and Eradicate the Invasive Gammarid, Dikerogammarus Villosus from UK Waters
    Cefas contract report C5525 A review of potential methods to control and eradicate the invasive gammarid, Dikerogammarus villosus from UK waters Paul Stebbing, Stephen Irving, Grant Stentiford and Nicola Mitchard For Defra, Protected Species and Non-native Species Policy Group Commercial in confidence Executive Summary The killer shrimp, Dikerogammarus villosus (Dv) is a large gammarid of Ponto-Caspian origin Dv has invaded and spread over much of mainland Europe where it has out-competed a number of native species. Dv was discovered at Grafham Water, Cambridgeshire, England, in September 2010 and subsequently in Wales in Cardiff Bay and Eglwys Nunydd near Port Talbot. In early 2012 it was found in the Norfolk Broads, the full extent of its distribution in the area is still being determined. The main objective of this work was to review the potential approaches for the control/eradication of invasive Dv populations in the UK. The approaches reviewed include physical removal (e.g. trapping), physical control (e.g. drainage, barriers), biological control (e.g. predation, disease), autocides (e.g. male sterilization and pheromone control) and biocides (the use of chemical pesticides). It should be noted that there have been no specific studies looking at the control and/or eradication of this particular species. The examples presented within this study are therefore primarily related to control of other invasive/pest species or are speculative. Recommendation made and potential applications of techniques are therefore based on expert opinion, but are limited by a relative lack of understanding of the basic life history of D. villosus within its invasive range.
    [Show full text]
  • Establishment of a Taxonomic and Molecular Reference Collection to Support the Identification of Species Regulated by the Wester
    Management of Biological Invasions (2017) Volume 8, Issue 2: 215–225 DOI: https://doi.org/10.3391/mbi.2017.8.2.09 Open Access © 2017 The Author(s). Journal compilation © 2017 REABIC Proceedings of the 9th International Conference on Marine Bioinvasions (19–21 January 2016, Sydney, Australia) Research Article Establishment of a taxonomic and molecular reference collection to support the identification of species regulated by the Western Australian Prevention List for Introduced Marine Pests P. Joana Dias1,2,*, Seema Fotedar1, Julieta Munoz1, Matthew J. Hewitt1, Sherralee Lukehurst2, Mathew Hourston1, Claire Wellington1, Roger Duggan1, Samantha Bridgwood1, Marion Massam1, Victoria Aitken1, Paul de Lestang3, Simon McKirdy3,4, Richard Willan5, Lisa Kirkendale6, Jennifer Giannetta7, Maria Corsini-Foka8, Steve Pothoven9, Fiona Gower10, Frédérique Viard11, Christian Buschbaum12, Giuseppe Scarcella13, Pierluigi Strafella13, Melanie J. Bishop14, Timothy Sullivan15, Isabella Buttino16, Hawis Madduppa17, Mareike Huhn17, Chela J. Zabin18, Karolina Bacela-Spychalska19, Dagmara Wójcik-Fudalewska20, Alexandra Markert21,22, Alexey Maximov23, Lena Kautsky24, Cornelia Jaspers25, Jonne Kotta26, Merli Pärnoja26, Daniel Robledo27, Konstantinos Tsiamis28,29, Frithjof C. Küpper30, Ante Žuljević31, Justin I. McDonald1 and Michael Snow1 1Department of Fisheries, Government of Western Australia, PO Box 20 North Beach 6920, Western Australia; 2School of Animal Biology, University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia; 3Chevron
    [Show full text]
  • Reproduction in the Freshwater Crustacean Asellus Aquaticus Along a Gradient of Radionuclide Contamination at Chernobyl
    Science of the Total Environment 628–629 (2018) 11–17 Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv Reproduction in the freshwater crustacean Asellus aquaticus along a gradient of radionuclide contamination at Chernobyl Neil Fuller a, Alex T. Ford a, Liubov L. Nagorskaya d, Dmitri I. Gudkov c, Jim T. Smith b,⁎ a Institute of Marine Sciences, School of Biological Sciences, University of Portsmouth, Ferry Road, Portsmouth, Hampshire PO4 9LY, UK b School of Earth & Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth, Hampshire PO1 3QL, UK c Department of Freshwater Radioecology, Institute of Hydrobiology, Geroyev Stalingrada Ave. 12, UA-04210 Kiev, Ukraine d Applied Science Center for Bioresources of the National Academy of Sciences of Belarus, 27 Academicheskaya Str., 220072 Minsk, Belarus HIGHLIGHTS GRAPHICAL ABSTRACT • We assessed effects of Chernobyl radia- tion on crustacean reproduction. • Fecundity of Asellus aquaticus assessed at dose rates from 0.06–27.1 μGy/h. • No association of radiation with repro- ductive endpoints in A. aquaticus. • Findings support proposed benchmarks for the protection of aquatic popula- tions. • Data can assist in management of radio- actively contaminated environments. article info abstract Article history: Nuclear accidents such as Chernobyl and Fukushima have led to contamination of the environment that will per- Received 25 October 2017 sist for many years. The consequences of chronic low-dose radiation exposure for non-human organisms Received in revised form 29 January 2018 inhabiting contaminated environments remain unclear. In radioecology, crustaceans are important model organ- Accepted 29 January 2018 isms for the development of environmental radioprotection.
    [Show full text]
  • Nutria Nuisance in Maryland in This Issue: and the Search for Solutions Upcoming Conferences by Dixie L
    ANS Aquatic Nuisance Species Volume 4 No. 3 August 2001 FRESHWATER DIGEST FOUNDATION Providing current information on monitoring and controlling the spread of harmful nonindigenous species. Predicting Future Aquatic Invaders; the Case of Dikerogammarus villosus By Jaimie T.A. Dick and Dirk Platvoet he accumulation of case studies of invasions has led to for- mulations of general ‘predictors’ that can help us identify Tpotential future invaders. Coupled with experimental stud- ies, assessments may allow us to predict the ecological impacts of potential new invaders. We used these approaches to identify a future invader of North American fresh and brackish waters, the amphipod crustacean Dikerogammarus villosus. Why Identify D. villosus as Invasive? Dikerogammarus villosus (see Figure 1) originates from an invasion donor “hot spot”, the Ponto-Caspian region, which com- prises the Black, Caspian, and Azov Seas’ basins (Nesemann et al. 1995; Ricciardi & Rasmussen 1998; van der Velde et al. 2000). This species has already invaded western Europe, has moved through the Main-Danube canal, which was formally opened in 1992 (Tittizer 1996), and appeared in the River Rhine at the German/Dutch border in 1994-5 (bij de Vaate & Klink 1995). D. villosus is currently sweeping through Dutch waters (Dick & Platvoet 2000) and has Dikerogammarus villosus continued on page 26 Figure 1. Dikerogammarus villosus Photograph by Ivan Ewart The Nutria Nuisance in Maryland In This Issue: and the Search for Solutions Upcoming Conferences By Dixie L. Bounds, Theodore A. Mollett, and Mark H. Sherfy and Meetings . 27 utria, Myocastor coypus, is an invasive lished in 15 states nationwide, all reporting Nuisance Notes.
    [Show full text]
  • Dikerogammarus Villosus)
    Management of Biological Invasions (2018) Volume 9, Issue 2: 101–113 DOI: https://doi.org/10.3391/mbi.2018.9.2.04 Open Access © 2018 The Author(s). Journal compilation © 2018 REABIC Research Article A preliminary investigation into biosecurity treatments to manage the invasive killer shrimp (Dikerogammarus villosus) Marion Sebire*, Georgina Rimmer, Ruth Hicks, Sarah-Jane Parker and Paul D. Stebbing Centre for Environment, Fisheries and Aquaculture Science (Cefas), Weymouth, DT4 8UB, UK Author e-mails: [email protected] (MS), [email protected] (GR), [email protected] (RH), [email protected] (SJP), [email protected] (PDS) *Corresponding author Received: 11 April 2017 / Accepted: 18 December 2017 / Published online: 4 February 2018 Handling editor: Calum MacNeil Abstract Following the detection of the invasive killer shrimp, Dikerogammarus villosus (Dv) at two sites in the UK in September 2010, an effective biosecurity system is required to prevent further spread. This study investigated the application of several treatments as potential biosecurity measures with a view to their application on Dv-infected fomites. For each treatment, adult Dv were submerged for 15 minutes at different concentrations to determine the maximum lethal concentration, and for each effective treatment for different times to assess a minimal lethal time (LT50). Sodium hypochlorite (50,000 mg/Lmg/L), FAM30® (6 ml/l), Virkon S® (1% solution) and water at high temperature (45 °C) were found to cause 100% mortality within 15-min exposure, while carbonated water caused narcosis in 100% of animals within a few seconds of exposure.
    [Show full text]
  • Present Absent D
    Alien macro-crustaceans in freshwater ecosystems in Flanders Pieter Boets, Koen Lock and Peter L.M. Goethals Pieter Boets Ghent University (UGent) Laboratory of Environmental Toxicology and Aquatic Ecology Jozef Plateaustraat 22 B9000 Gent, Belgium pieter.boets@ugent. be Aquatic Ecology Introduction Why are aquatic ecosystems vulnerable to invasions ? • Ballast water • Attachment to ships • Interconnection of canals • Vacant niches as consequence of pollution Impact of invasive macroinvertebrates ? • Ecological: decrease of diversity destabilization of ecosystem • Economical: high costs for eradication decrease of yield in aquaculture Aquatic Ecology Introduction pathways Deliberatly introduced + aquaculture Shipping (long distance) Shipping (short distance) + interconnection of canals Aquatic Ecology The process of Potentialinvasion donor region Transport (e.g. through ballast water of ships) Introduction Biotic and abiotic factors Establishment & reproduction Interactions between species (competition, predation, …) Dispersal & dominant behavior Aquatic Ecology Overview of freshwater macrocrustaceansFirst occurence in in Family Species FlandersOrigin Flanders Gammaridae Gammarus pulex Gammarus fossarum Southern Gammarus roeseli Europe 1910 EchinogammarusGammarus tigrinus IberianUSA 1993 Dikerogammarusberilloni Peninsula 1925 villosus Ponto-Caspian 1997 CrangonictidTalitridae CrangonyxOrchestia cavimana Ponto-Caspian 1927 ae Chelicorophiumpseudogracilis USA 1992 Corophidae curvispinum Ponto-Caspian 1990 Asellidae Asellus aquaticus Southern
    [Show full text]
  • Experimental Evidence of Invasion Facilitation in the Zebra Mussel-Killer
    bioRxiv preprint doi: https://doi.org/10.1101/626432; this version posted May 2, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 1 Experimental evidence of invasion facilitation in the 2 zebra mussel-killer shrimp system 3 4 5 Matteo Rolla1, Sofia Consuegra1, Ellie Carrington1, David Hall2, 6 Carlos Garcia de Leaniz*1 7 8 1Department of BioSciences, Centre for Sustainable Aquatic Research, Swansea University, 9 Singleton Park, Swansea SA2 8PP, UK 10 11 2Cardiff Harbour Authority, Queen Alexandra House, Cargo Road, Cardiff CF10 4LY 12 *corresponding author: [email protected] 13 14 1 bioRxiv preprint doi: https://doi.org/10.1101/626432; this version posted May 2, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 15 Abstract 16 Invasion facilitation, whereby one species has a positive effect on the establishment of another 17 species, could help explain the rapid colonisation shown by some freshwater invasive species, 18 but the underlying mechanisms remain unclear. We employed two-choice test arenas to test 19 whether the presence of zebra mussel (Dreissena polymorpha) could facilitate the establishment 20 of the killer shrimp (Dikerogammarus villosus). Killer shrimp preferred to settle on mats of zebra 21 mussel, but this was unrelated to mat size, and was not different from attraction shown to 22 artificial grass, suggesting that zebra mussel primarily provides substrate and refuge to the killer 23 shrimp.
    [Show full text]
  • Comparison of Some Epigean and Troglobiotic Animals Regarding Their Metabolism Intensity
    International Journal of Speleology 48 (2) 133-144 Tampa, FL (USA) May 2019 Available online at scholarcommons.usf.edu/ijs International Journal of Speleology Off icial Journal of Union Internationale de Spéléologie Comparison of some epigean and troglobiotic animals regarding their metabolism intensity. Examination of a classical assertion Tatjana Simčič1* and Boris Sket2 1Department of Organisms and Ecosystems Research, National Institute of Biology, Večna pot 111, SI-1000 Ljubljana, Slovenia 2Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia Abstract: This study determines oxygen consumption (R), electron transport system (ETS) activity and R/ETS ratio in two pairs of epigean and hypogean crustacean species or subspecies. To date, metabolic characteristics among the phylogenetic distant epigean and hypogean species (i.e., species of different genera) or the epigean and hypogean populations of the same species have been studied due to little opportunity to compare closely related epigean and hypogean species. To fill this gap, we studied the epigean Niphargus zagrebensis and its troglobiotic relative Niphargus stygius, and the epigean subspecies Asellus aquaticus carniolicus in comparison to the troglobiotic subspecies Asellus aquaticus cavernicolus. We tested the previous findings of different metabolic rates obtained on less-appropriate pairs of species and provide additional information on thermal characteristics of metabolic enzymes in both species or subspecies types. Measurements were done at four temperatures. The values of studied traits, i.e., oxygen consumption, ETS activity, and ratio R/ETS, did not differ significantly between species or subspecies of the same genus from epigean and hypogean habitats, but they responded differently to temperature changes.
    [Show full text]
  • ^^®Fe Ojiioxq © Springer-Verlag 1987
    Polar Biol (1987) 7:11-24 ^^®fe OJiioXq © Springer-Verlag 1987 On the Reproductive Biology of Ceratoserolis trilobitoides (Crustacea: Isopoda): Latitudinal Variation of Fecundity and Embryonic Development Johann-Wolfgang Wagele Arbeitsgruppe Zoomorphologie, Fachbereich 7, Universitat Oldenburg, Postfach 2503, D-2900 Oldenburg, Federal Republic of Germany Received 21 February 1986; accepted 1 July 1986 Summary. The embryonic development of Ceratoserolis Material and Methods trilobitoides (Crustacea: Isopoda) is described. It is estimated that breeding lasts nearly 2 years. In compari­ During the expedition "Antarktis III" of RVPolarstern several samples were taken in the area of the Antarctic Peninsula, South Shetlands, son with non-polar isopods 3 causes for the retardation South Orkneys and the Eastern and Southern Weddell Sea by means of of embryonic development are discussed: genetically an Agassiztrawl (localities with C trilobitoides: see Wagele, in press). fixed adaptations to the polar environment, the physio­ Females used for the study of latitudinal variations of fecundity and logical effect of temperature and the effect of egg size. egg size (Fig. 6) were collected from the following sites: 62°8.89'S The latter seems to be of minor importance. Intraspecific 58°0.46'W, 449 m (King George Island); 60°42.40'S 45°33.07'W, 86 m (Signy Island); 73°39.7'S 20°59.76'W, 100m (off Riiser-Larsen Ice variations of fecundity are found in populations from the Shelf, near Camp Norway); 72°30.35'S 17°29.88'W, 250 m (off Riiser- Weddell Sea, the largest eggs occur in the coldest region. Larsen Ice Shelf); 73°23.36'S 21°30.37'W, 470 m (off Riiser-Larsen Ice The distribution of physiological races corresponds to the Shelf);'^77°18.42'S 41°25.79'W, 650m (Gould Bay); 77°28.85'S distribution of morphotypes.
    [Show full text]