DOCSLIB.ORG

Habitat Preference of the Sea Urchin (Parechinus Angulosus) Within Tide Pools Brian Hammond, Jennifer Miller, and Melissa Ross Bioe 159 Spring 2013

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Habitat Preference of the Sea Urchin (Parechinus Angulosus) Within Tide Pools Brian Hammond, Jennifer Miller, and Melissa Ross Bioe 159 Spring 2013 Habitat preference of the sea urchin (Parechinus angulosus) within tide pools Brian Hammond, Jennifer Miller, and Melissa Ross Bioe 159 Spring 2013 Abstract Determining the habitat features associated with a species and its functionality gives insight into that species’ evolutionary history, life history characteristics, conservation requirements, biological interactions and spatial distribution. Urchin species’ potential to interpret environmental features through spatial vision and chemosensory perception allows them to distinguish and exploit beneficial habitat. The degree of predation on urchin species can have dramatic impacts on the algal community due to the herbivores' high-density aggregating and grazing tendencies. We observed that Parechinus angulosus (P. angulosus) aggregate within crevices and their spatial distribution was not consistent within or among intertidal pools and that vegetation and substrate type varied within pools. The purpose of this study was to determine the habitat associations of P. angulosus with respect to substrate type, biological cover, and provisioning of refuge. We collected data using the Uniform Point Contact (UPC) method in order to the test our hypotheses that the occupation rate of P. angulosus would be dis-proportional to the substrate, biological cover, and refuge available within tide pools. Overall we determined that P. angulosus exhibits habitat associations and habitat utilization which may be the result of adaptations in response to predation pressure, or may provide some fitness benefit. 1. Introduction Ecological systems are defined on the basis of interactions between organisms and their surrounding environment. An integral way in which animals interact with their environment is through their utilization of habitat (Bax, 1999). Understanding the distribution of organisms relative to their habitat can be fundamental to understanding the foundational ecology of a species (Syms,1995). 1.1 Importance of Habitat Associations A habitat is commonly defined as, “a place where a plant or animal is found” (Diaz, 2004). By building off of Diaz’s terminology we are defining a habitat association as: the relationship between a species and the physical and biological characteristics of its habitat. Determining the habitat features associated with a species and its functionality gives insight into that species’ evolutionary history, life history characteristics, conservation requirements, biological interactions and spatial distribution (Wahle and Steneck, 1990; Leber, 1985; Phillips et al., 2003). Knowledge of habitat is necessary for fishery and conservation policies such as the Manguson-Stevens Fishery Conservation and Management Act, the primary law governing fisheries management in US originally enacted in 1976, which states “all essential fish habitat should be identified and protected” (Benaka, 1999). Distinguishing between essential and non-essential habitat by assessing of the quality and quantity of habitat is imperative for the development of appropriate conservation and management strategies (Diaz, 2004). 1.2 Behavioral Responses to Environment Animals exhibit a wide array of behavioral responses to their physical and biological environment by interpreting cues and signals as well as utilizing different forms of taxis (Main, 1987). Organisms’ behavioral responses to environmental stresses include physiological tolerances to environmental conditions and motility responses to physical stresses (e.g. desiccation, turbulence, salinity) (Iacarella and Helmuth, 2011); animals can navigate through their environment by migrating in response to environmental or biological stimuli (Sameoto, 2007). Even animals with low spatial resolution can detect the rugosity of the substrate to seek out refuge from predation (Blevins and Johnsen, 2004). Essentially, predators have the potential to significantly influence the behavior of prey organisms and induce a habitat association or preference (Carr, 2008). The common use of Fish Aggregating Devices highlights the influence that species-environment relationships have on animal distribution and systems through aggregation (Jaquemet et al., 2011). In addition, observations of organisms aggregating during spawning indicate that habitat associations may indirectly increase reproductive success (Pennington, 1985). 1.3 Habitat Usage Marine and terrestrial animals have obtained the ability to recognize a beneficial habitat feature and the functional significance in order to acquire a fitness gain (Blevins and Johnsen, 2004; Main, 1987). Some organisms’ sensitivity to biochemical cues allows them to respond to environmental changes that “have clear adaptive significance” such as acquiring shelter in response to predation (Bernstein et al., 1983). Urchin species’ potential to interpret environmental features through spatial vision and chemosensory perception allows them to distinguish and utilize beneficial habitat (Blevins and Johnsen 2004; Pinna et al., 2012). They have been known to migrate towards areas of high rugosity and actively provision refuge in the presence of predators (Pinna et al. 2012; Sheibling and Hamm, 1991). The degree of predation on urchin species can have dramatic impacts on the algal community due to the herbivores' high-density aggregating and grazing tendencies (Hagen 1994; Wright, 2005). 1.4 Parechinus angulosus in Betty’s Bay, South Africa The multiple bioregions of South Africa’s coastline are the result of various processes influenced by the Benguela and Agulhas currents. The combination of the distinctive water temperatures generates cool temperate, subtropical, and warm temperate climates that induce a biodiversity hotspot, distinguishing South Africa’s marine habitat. Cool water kelp forests, consisting mainly of Eklonia maxima, characterize the southwestern coastline of Betty’s Bay, South Africa. Numerous species of 2 | Page invertebrates that inhabit the rocky intertidal are largely herbivorous and include: Patella longicosta, Patella cochlear, Dendrofissurella scutellum, Parechinus angulosus, and Haliotis midae (Blamey and Branch, 2012). Impromptu observations in Betty’s Bay suggested that P. angulosus exhibited possible habitat associations with high rugosity substrate and crustose coralline algae. We observed that P. angulosus aggregate within crevices and their spatial distribution was not consistent within or among intertidal pools and that vegetation and substrate type varied within pools. We wanted to examine the potential habitat associations of P. angulosus. The purpose of this study is to determine the habitat associations of P. angulosus with respect to substrate type, biological cover, and provisioning of refuge. In a survey of 28 pools we predict that: (1) the occupation rate of P. angulosus will be disproportional to the substrate type observed; (2) the occupation rate of P. angulosus will be disproportional to the biological cover observed; and (3) the occupation rate of P. angulosus will be disproportional to the availability of refuge observed. We expect that the species will not utilize the habitat features of interest uniformly. 2. Methods 2.1 Study Site Studies were conducted between April 21, 2013 and April 30, 2013 in Betty's Bay, South Africa (34° 22′ 08″ S, 18° 54′ 20″ E) which is situated within a marine protected area along the south-westerly coastline. (Figure 1). The intertidal regions feature hard, jagged bedrock and boulders that create crevices and sheltered hollows. This system is characterized by Ecklonia maxima and other algae species such as Leptophytum foveatum and Ulva rigida. Other invertebrate species include the Tiger Topshell, Oxystele tigirina, Long-spined limpet, Patella longicosta, and the Pear limpet, Patella cochlear. P. angulosus is typically found to be associated with abalone, Haliotis midae and anemone species (e.g. Bunodosoma capensis). Data was collected at low tide from 28 tide pools which were chosen randomly and ranged in size from 10 to 30 m2, and depth from 0.25 to 1.0 m at varying tidal heights. The sites also had to meet the criteria that they must be pools located along the cove and any one area must not be overrepresented. 2.2 Study System The Cape Sea Urchins, Parechinus angulosus are important herbivores that occur commonly in the rocky intertidal of South Africa. Sea Urchins are known for their potential to transform the functionality of kelp forests through grazing (Blamey and Branch, 2012). This can have profound 3 | Page ecological implications due to the role kelp forests have as a refuge for larval development of many fish and invertebrate species (Andrew, 1993). P. angulosus feed primarily on trapped drift kelp as opposed to actively grazing (Day and Branch, 2002). This feeding pattern indirectly facilitates the urchin’s role in sheltering recruits and juvenile abalone. The Rock lobster, Jasus lalandii preys upon P. angulosus and is responsible for a drastic decrease in their abundance in beginning in 1990 when environmental conditions shifted the center of Rock lobster abundance south-easterly. Because P. angulosus individuals provide a suitable refuge for juvenile abalone, the shift in the Rock lobster habitat boundaries correlated to a decrease in abalone densities (Day and Branch, 2002). Figure 1. Study site in Betty's Bay, South Africa. Individual tide pools were chosen at random. 2.3 Habitat surveys: Substrate Type, Biological Cover, and Available Refuge We collected data using the Uniform Point Contact (UPC) method in order to the test
Load more

Recommended publications
  • KELP BLUE NAMIBIA (Pty) Ltd
    KELP BLUE NAMIBIA (Pty) Ltd EIA SCOPING & IMPACT ASSESSMENT REPORT AND ENVIRONMENTAL MANAGEMENT PLAN FOR THE PROPOSED KELP CULTIVATION PILOT PROJECT NEAR LÜDERITZ, KARAS REGION Prepared for: Kelp Blue Namibia (Pty) Ltd August 2020 1 DOCUMENT CONTROL Report Title EIA SCOPING & IMPACT ASSESSMENT REPORT FOR THE PROPOSED KELP CULTIVATION PILOT PROJECT NEAR LÜDERITZ, KARAS REGION Report Author Werner Petrick Client Kelp Blue Namibia (Pty) Ltd Project Number NSP2020KB01 Report Number 1 Status Final to MEFT and MFMR Issue Date August 2020 DISCLAIMER The views expressed in the document are the objective, independent views of the author with input from various Environmental and Social Experts (i.e. Specialists). Neither Werner Petrick nor Namisun Environmental Projects and Development (Namisun) have any business, personal, financial, or other interest in the proposed Project apart from fair remuneration for the work performed. The content of this report is based on the author’s best scientific and professional knowledge, input from the Environmental Specialists, as well as available information. Project information contained herein is based on the interpretation of data collected and data provided by the client, accepted in good faith as being accurate and valid. Namisun reserves the right to modify the report in any way deemed necessary should new, relevant, or previously unavailable or undisclosed information become available that could alter the assessment findings. This report must not be altered or added to without the prior written consent of the author. Project Nr: NSP2020KB01 EIA SCOPING & IMPACT ASSESSMENT REPORT AND EMP FOR August 2020 Report number: 1 THE PROPOSED KELP CULTIVATION PILOT PROJECT 2 Table of Contents 1 INTRODUCTION ..................................................................................................................................
    [Show full text]
  • Modeling a Regime Shift in a Kelp Forest Ecosystem Caused by a Lobster Range Expansion
    BULLETIN OF MARINE SCIENCE. 89(1):347–375. 2013 http://dx.doi.org/10.5343/bms.2011.1127 MODELING A REGIME SHIFT IN A KELP FOREST ECOSYSTEM CAUSED BY A LOBSTER RANGE EXPANSION Laura K Blamey, Éva E Plagányi, and George M Branch ABSTRACT The South African West Coast rock lobster, Jasus lalandii (H. Milne-Edwards, 1837), has expanded its range to the southeast, where its abundance has increased radically. The ecological consequences of this “invasion” are likely to be considerable. We employed a minimally realistic model to simulate the “invasion” and to explore interactions of J. lalandii with the sea urchin, Parechinus angulosus (Leske, 1778), and the abalone, Haliotis midae Linnaeus, 1758, juveniles of which shelter beneath this urchin. Model fits to empirical data were good, although species-interaction terms were difficult to estimate. Base-case trajectories indicated: (1) Lobster biomass peaked at about 1000 t in 1994 and was then reduced by fishing to a stable value approximately 50% lower by 2008. (2) Urchins remained close to carrying capacity in “noninvaded” areas but collapsed to local extinction by 1997 in the invaded area. (3) Abalone declined over 2000–2008 in noninvaded areas because of illegal fishing and collapsed to near zero in the “invaded” area because of illegal fishing combined with increased lobster abundance. Sensitivity analyses favored the hypothesis that the invasion was due to adult immigration rather than larval recruitment. Modeled 50-yr projections indicated that urchins will remain locally extinct in the invaded area, even 50 yrs into the future. The abalone collapse in the invaded area would persist >50 yrs, even if lobsters were absent.
    [Show full text]
  • Ecosystem Effects of a Rock-Lobster 'Invasion': Comparative and Modelling Approaches
    Town The copyright of this thesis rests with the University of Cape Town. No quotation from it or information derivedCape from it is to be published without full acknowledgement of theof source. The thesis is to be used for private study or non-commercial research purposes only. University Ecosystem effects of a rock-lobster 'invasion': comparative and modelling approaches Laura Kate Blamey Town Cape Of Supervisors: Emeritus Professor George M. Branch and Dr Éva Plagányi-Lloyd Thesis presented for the Degree of UniversityDoctor of Philosophy In the Department on Zoology Faculty of Science University of Cape Town February 2010 Town Cape Of University “For in the end, we will conserve only what we love, we will love only what we understand, and we will understand only what we are taught.” ~ Baba Dioum, 1968. This thesis is dedicated to my parentsTown Campbell and Ursula Blamey Cape And to my grandfather DonaldOf Currie University Town Cape Of University Declaration I hereby declare that all the work presented in this thesis is my own, except where otherwise stated in the text. This thesis has not been submitted in whole or in part for a degree at any other university. Town _____________________ Laura Kate Blamey Cape _____________________ Of Date University Table of Contents Acknowledgements...................................................................................................... iii Abstract.......................................................................................................................... v Glossary .......................................................................................................................vii
    [Show full text]
  • Thesis Sci 1975 Greenwood Pe
    THE POPULATION DYNAMICS AND ECOLOGICAL ENERGETICS OF Parechinus angulosus AT ROBBEN ISLAND AND IN FI.U.SE BAY SOUTH AFRICA BY P.J. Greenwood University of Cape Town Submitted in fulfilment of the requirements . for the degree of Master of Science in the Department of Zoology at the University ofcape Town 19744 The copyrighz c;· ~::::;; '.:: ...::::.; is held by the ·ver·"l1-.1 cf /· .. ~.-. T ~.,,.,, Unl .t.) I ;O I - '.~., '.1 .. ......... I ~ • R.eproductlc:1 c:~ t::0 '":::::\.::! er any part l ma)' be maC:e fr);- stuJy purpose:; only, and +,,~ publication. ;-=-----.-,------~---~ The copyright of this thesis vests in the author. No quotation from it or information derived from it is to be published without full acknowledgement of the source. The thesis is to be used for private study or non- commercial research purposes only. Published by the University of Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University of Cape Town r~ I TO MY PARENTS for more than encouragement University of Cape Town I )/ PART I •' POPULATION STRUCTURE, DYNAMICS AND PRODUCTION University of Cape Town TABLE OF CONTENTS PART I POPULATION STRUCTURE, DYNAMICS AND PRODUCTION General 1 THE STUDY """C',,,,,_,,,AREAS AND THEIR HYDROLOGY 5 Robben Island 5 Oatland Point 7 Smitswinkel Bay ((False Bay)) 8 POPULATION STRUCTURE AND RECRUITMENT 9 Field Methods 9 Density and Distribution 10 Data Processing 11 Robben Island 12 Oatland Point 14 Rockeater ((Smitswinkel Bay)) 15 GROWTH 16 Robben Island 16 Oatland Point 19 Rockeater 21 Growth PatternsUniversity of Cape Town 22 AGEING 25 Robben Island 25 / Oatland Point ,// 25 MORTALITY.
    [Show full text]
  • Echinodermata: Ophiuroidea) of South Africa
    Taxonomy, biodiversity and biogeography of the brittle stars (Echinodermata: Ophiuroidea) of South Africa. Jennifer M. Olbers Thesis presented for the degree of Doctor of Philosophy Universityin the Department of of Biological Cape Sciences Town University of Cape Town November 2016 Supervisor: Prof. Charles L. Griffiths University of Cape Town Co-supervisor: Dr Yves Samyn Royal Belgian Institute of Natural Sciences The copyright of this thesis vests in the author. No quotation from it or information derived from it is to be published without full acknowledgement of the source. The thesis is to be used for private study or non- commercial research purposes only. Published by the University of Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University of Cape Town ii “The sea, once it casts its spell, holds one in its net of wonder forever” - Jacques Yves Cousteau “…echinoderms, a noble group especially designed to puzzle the zoologist”. - Libbie Henrietta Hyman iii DECLARATION - PLAGIARISM & FREE LICENCE I, Jennifer M. Olbers, declare that: (a) I know the meaning of plagiarism and declare that all of the work in the thesis, with the exception of which is properly acknowledged, is my own; (b) the above thesis is my own unaided work, both in conception and execution, and that apart from the normal guidance from my supervisors, I have received no assistance except as stated below; (c) neither the substance nor any part of the thesis has been submitted in the past, or is being, or is to be submitted for a degree at this University or at any other University, except as stated below; (d) the University is granted free licence to reproduce the above thesis in whole or in part, for the purpose of research.
    [Show full text]
  • Kelp Forests in False Bay: Urchins Vs
    Kelp forests in False Bay: urchins vs. macroalgae in South Africa’s south-west coast biogeographical transition zone. Kathryn Morris Town Minor Dissertation presented in partial fulfilment of the requirements for the degree of Master of Science in the Department of Biological Sciences Cape of University of Cape Town Submitted: June 2017 University Supervisor: Dr Laura Blamey 1 The copyright of this thesis vests in the author. No quotation from it or information derivedTown from it is to be published without full acknowledgement of the source. The thesis is to be used for private study or non- commercial research purposes Capeonly. of Published by the University of Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University Table of Contents Acknowledgements .................................................................................................................. 3 Abstract ..................................................................................................................................... 4 1. Introduction .......................................................................................................................... 5 1.1 Kelp forests in a changing climate ................................................................................. 5 1.2 South African kelp forest ecosystems and the role of the urchin Parechinus angulosus ............................................................................................................................... 7 1.3 Significance
    [Show full text]
  • Thermal Tolerance and the Potential Effects Of
    THERMAL TOLERANCE AND THE POTENTIAL EFFECTS OF CLIMATE CHANGE ON COASTAL INTERTIDAL AND ESTUARINE ORGANISMS IN THE KARIEGA ESTUARY AND ADJACENT INTERTIDAL COASTLINE, EASTERN CAPE, SOUTH AFRICA A thesis submitted in fulfilment of the requirements for the degree of DOCTOR OF PHILOSOPHY of RHODES UNIVERSITY By KERRY-ANN VAN DER WALT December 2019 ABSTRACT Temperature changes due to the effects of climate change are evident on all continents and oceans. As a result, there is a growing concern over how marine ectotherms will respond to extreme or fluctuating environmental temperatures. Temperature changes have strong direct and indirect effects on individual, population, and ecosystem functioning traits. A multi-scale approach determining the thermal tolerance and performance of several marine ectotherms belonging to different coastal habitats is rarely considered in thermal physiology studies but is effective for an integrated ecosystem assessment. As such, for this thesis, I aimed to quantify and compare the thermal tolerance and performance of a range of coastal marine ectotherms (fish and macro-invertebrates) with different biogeographical distributions from estuarine, subtidal and rocky intertidal habitats to available and projected in situ temperature data. This was also undertaken to gauge the local vulnerability of each species across summer and winter in a warm-temperate region of South Africa. This was done using a multi-method physiological approach, which included the dynamic method (CTmax and CTmin), static respirometry and maximum heart rate f Hmax). Results of the dynamic method on several fish and macro-invertebrate species indicated that there are differences in thermal tolerance according to taxonomy, biogeography and habitat for both summer and winter.
    [Show full text]
  • 7Ec6-47C3-9C8f-5F7c78bb7fdb.Txt
    Dépôt Institutionnel de l’Université libre de Bruxelles / Université libre de Bruxelles Institutional Repository Thèse de doctorat/ PhD Thesis Citation APA: Rolet, G. (2012). Structure et rôle du caecum gastrique des échinides détritivores: étude particulière d'Echinocardium cordatum, Echinoidea: Spatangoida (Unpublished doctoral dissertation). Université libre de Bruxelles, Faculté des Sciences – Sciences biologiques, Bruxelles. Disponible à / Available at permalink : https://dipot.ulb.ac.be/dspace/bitstream/2013/209654/5/c258d843-7ec6-47c3-9c8f-5f7c78bb7fdb.txt (English version below) Cette thèse de doctorat a été numérisée par l’Université libre de Bruxelles. L’auteur qui s’opposerait à sa mise en ligne dans DI-fusion est invité à prendre contact avec l’Université ([email protected]). Dans le cas où une version électronique native de la thèse existe, l’Université ne peut garantir que la présente version numérisée soit identique à la version électronique native, ni qu’elle soit la version officielle définitive de la thèse. DI-fusion, le Dépôt Institutionnel de l’Université libre de Bruxelles, recueille la production scientifique de l’Université, mise à disposition en libre accès autant que possible. Les œuvres accessibles dans DI-fusion sont protégées par la législation belge relative aux droits d'auteur et aux droits voisins. Toute personne peut, sans avoir à demander l’autorisation de l’auteur ou de l’ayant-droit, à des fins d’usage privé ou à des fins d’illustration de l’enseignement ou de recherche scientifique, dans la mesure justifiée par le but non lucratif poursuivi, lire, télécharger ou reproduire sur papier ou sur tout autre support, les articles ou des fragments d’autres œuvres, disponibles dans DI-fusion, pour autant que : - Le nom des auteurs, le titre et la référence bibliographique complète soient cités; - L’identifiant unique attribué aux métadonnées dans DI-fusion (permalink) soit indiqué; - Le contenu ne soit pas modifié.
    [Show full text]
  • Echinodermata: Echinoidea)
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by PubMed Central Evolution of a Novel Muscle Design in Sea Urchins (Echinodermata: Echinoidea) Alexander Ziegler1*, Leif Schro¨ der2, Malte Ogurreck3, Cornelius Faber4, Thomas Stach5 1 Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, United States of America, 2 Molecular Imaging Group, Leibniz-Institut fu¨r Molekulare Pharmakologie, Berlin, Germany, 3 Institut fu¨r Werkstoffforschung, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany, 4 Institut fu¨r Klinische Radiologie, Universita¨tsklinikum Mu¨nster, Mu¨nster, Germany, 5 Institut fu¨r Biologie, Freie Universita¨t Berlin, Berlin, Germany Abstract The sea urchin (Echinodermata: Echinoidea) masticatory apparatus, or Aristotle’s lantern, is a complex structure composed of numerous hard and soft components. The lantern is powered by various paired and unpaired muscle groups. We describe how one set of these muscles, the lantern protractor muscles, has evolved a specialized morphology. This morphology is characterized by the formation of adaxially-facing lobes perpendicular to the main orientation of the muscle, giving the protractor a frilled aspect in horizontal section. Histological and ultrastructural analyses show that the microstructure of frilled muscles is largely identical to that of conventional, flat muscles. Measurements of muscle dimensions in equally-sized specimens demonstrate that the frilled muscle design, in comparison to that of the flat muscle type, considerably increases muscle volume as well as the muscle’s surface directed towards the interradial cavity, a compartment of the peripharyngeal coelom. Scanning electron microscopical observations reveal that the insertions of frilled and flat protractor muscles result in characteristic muscle scars on the stereom, reflecting the shapes of individual muscles.
    [Show full text]
  • Coastal Marine Waters
    S O U T H A F R I C A N WATER QUALITY GUIDELINES FOR COASTAL MARINE WATERS VOLUME 1 NATURAL ENVIRONMENT Department of Water Affairs and Forestry First Edition 1995 SOUTH AFRICAN WATER QUALITY GUIDELINES FOR COASTAL MARINE WATERS Volume 1: Natural Environment First Edition, 1996 I would like to receive future versions of this document (Please supply the information required below in block letters and mail to the given address) Name:................................................................................................................................. Organisation:...................................................................................................................... Address:............................................................................................................................. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. Postal Code:........................................................................................................................... Telephone No.:................................................................................................................... E-Mail:................................................................................................................................
    [Show full text]
  • Modeling a Regime Shift in a Kelp Forest Ecosystem Caused by a Lobster Range Expansion
    BULLETIN OF MARINE SCIENCE. 89(1):347–375. 2013 http://dx.doi.org/10.5343/bms.2011.1127 View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Cape Town University OpenUCT MODELING A REGIME SHIFT IN A KELP FOREST ECOSYSTEM CAUSED BY A LOBSTER RANGE EXPANSION Laura K Blamey, Éva E Plagányi, and George M Branch ABSTRACT The South African West Coast rock lobster, Jasus lalandii (H. Milne-Edwards, 1837), has expanded its range to the southeast, where its abundance has increased radically. The ecological consequences of this “invasion” are likely to be considerable. We employed a minimally realistic model to simulate the “invasion” and to explore interactions of J. lalandii with the sea urchin, Parechinus angulosus (Leske, 1778), and the abalone, Haliotis midae Linnaeus, 1758, juveniles of which shelter beneath this urchin. Model fits to empirical data were good, although species-interaction terms were difficult to estimate. Base-case trajectories indicated: (1) Lobster biomass peaked at about 1000 t in 1994 and was then reduced by fishing to a stable value approximately 50% lower by 2008. (2) Urchins remained close to carrying capacity in “noninvaded” areas but collapsed to local extinction by 1997 in the invaded area. (3) Abalone declined over 2000–2008 in noninvaded areas because of illegal fishing and collapsed to near zero in the “invaded” area because of illegal fishing combined with increased lobster abundance. Sensitivity analyses favored the hypothesis that the invasion was due to adult immigration rather than larval recruitment. Modeled 50-yr projections indicated that urchins will remain locally extinct in the invaded area, even 50 yrs into the future.
    [Show full text]
  • Broad Application of Non-Invasive Imaging Techniques to Echinoids and Other Echinoderm Taxa*
    Zoosymposia 7: 53–70 (2012) ISSN 1178-9905 (print edition) www.mapress.com/zoosymposia/ ZOOSYMPOSIA Copyright © 2012 · Magnolia Press ISSN 1178-9913 (online edition) Broad application of non-invasive imaging techniques to echinoids and other echinoderm taxa* ALEXANDER ZIEGLER Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, Cam- bridge, MA, USA; E-mail: [email protected] *In: Kroh, A. & Reich, M. (Eds.) Echinoderm Research 2010: Proceedings of the Seventh European Conference on Echinoderms, Göttingen, Germany, 2–9 October 2010. Zoosymposia, 7, xii + 316 pp. Abstract Tomographic imaging techniques such as micro-computed tomography (µCT) and magnetic resonance imaging (MRI) permit the gathering of digital anatomical data from whole animal specimens non-invasively. The resulting datasets can be used for direct observation of the two-dimensional tomographic image data as well as for manual and semi-automated three-dimensional modelling. Freshly fixed specimens as well as preserved museum material can be successfully ana- lyzed using this approach, giving the zoomorphologist a powerful tool for large-scale comparative studies. In order to demonstrate the principle suitability of non-invasive imaging in echinoderm research, µCT scans of 199 and MRI scans of 92 sea urchin (Echinodermata: Echinoidea) species were acquired, resulting in a total of 203 analyzed echinoid species. The taxa selected represent 50 of the currently recognized 60 extant sea urchin families. The present article lists all spe- cies that have been analyzed so far and provides information about the scanning parameters employed for each dataset. Furthermore, the workflow established to generate three-dimensional models of sea urchins is outlined.
    [Show full text]