GUIDE TO THE COASTAL AND SURFACE ZOOPLANKTON OF THE SOUTH-WESTERN INDIAN OCEAN David VP Conway Rowena G White Joanna Hugues-Dit-Ciles Christopher P Gallienne David B Robins DEFRA Darwin Initiative Zooplankton Programme Version 1 June 2003 Marine Biological Association of the United Kingdom Occasional Publication No 15 GUIDE TO THE COASTAL AND SURFACE ZOOPLANKTON OF THE SOUTH-WESTERN INDIAN OCEAN David VP Conway Marine Biological Association Plymouth Rowena G White University of Wales Bangor Joanna Hugues-Dit-Ciles, Christopher P Gallienne and David B Robins Plymouth Marine Laboratory UK-DEFRA Darwin Initiative Project 162/09/004 Zooplankton of the Mascarene Plateau Version 1 June 2003 Marine Biological Association of the United Kingdom Occasional Publication No 15 General disclaimer The authors, the Marine Biological Association and the Plymouth Marine Laboratory do not guarantee that this publication is without flaw of any kind and disclaims all liability for any error, loss, or other consequence which may arise from you relying on any information in this publication. Citation Conway, D.V.P., White, R.G., Hugues-Dit-Ciles, J., Gallienne, C.P., Robins, D.B. (2003). Guide to the coastal and surface zooplankton of the south-western Indian Ocean, Occasional Publication of the Marine Biological Association of the United Kingdom, No 15, Plymouth, UK. Electronic copies This guide is available for download, without charge, from the Plymouth Marine Laboratory Website at http://www.pml.ac.uk/sharing/zooplankton.htm. © 2003 by the Marine Biological Association of the United Kingdom and the Plymouth Marine Laboratory, Plymouth, UK. No part of this publication may be reproduced in any form without permission of the authors. ISSN 0260-2784 1 CONTENTS Introduction Page 4 Background to the Zooplankton programme 4 Sampling programme 4 Scope of this guide 5 Acknowledgements 6 Phytoplankton and cyanobacteria 7 Protozoan Zooplankton 8 Phylum Sarcomastigophora 8 Radiolaria 8 Acantharia 9 Foraminifera 10 Phylum Ciliophora 10 Tintinnida 10 Eumetazoan Zooplankton 11 Phylum Cnidaria 11 Class Anthozoa 11 Class Scyphozoa 12 Class Hydrozoa 13 Sub-class Hydroidomedusae 13 Sub-class Siphonophorae 25 Phylum Ctenophora 38 Phylum Platyhelminthes 39 Phylum Nemertina 40 Phylum Rotifera 41 Phylum Mollusca 42 Phylum Annelida 63 Phylum Arthropoda 73 Subphylum Uniramia 73 Class Insecta 73 Subphylum Chelicerata 74 Class Pycnogonida 74 Subphylum Crustacea 74 Class Brachiopoda 74 Suborder Cladocera 74 Class Maxillipoda 75 Infraclass Facetotecta 75 Infraclass Cirripedia 75 Subclass Copepoda 76 Order Calanoida 82 2 Order Cyclopoida 195 Order Harpacticoida 208 Order Poicilostomatoida 218 Order Monstrilloida 263 Order Siphonostomatoida 263 Class Ostracoda 264 Class Malacostraca 265 Order Stomatopoda 265 Order Mysida 266 Order Amphipoda 266 Order Isopoda 267 Order Cumacea 268 Order Euphausiacea 269 Order Decapoda 281 Phylum Phoronida 292 Phylum Bryozoa 292 Phylum Brachiopoda 293 Phylum Echinodermata 293 Phylum Chaetognatha 294 Phylum Hemichordata 319 Phylum Urochordata 319 Class Ascidiacea 319 Class Larvacea 320 Class Thalliacea 320 Subphylum Cephalochordata 321 Bibliography 322 The background to the cover of the guide is page 100, Pontellid copepods, from Dakin, W.J. & Colefax, A.N. 1940. The plankton of the Australian coastal waters off New South Wales. Part 1. Publications of the University of Sydney, Department of Zoology. 3 INTRODUCTION This guide has been compiled, as part of a UK DEFRA Darwin Initiative Project, as an aid to researchers, particularly new researchers, in the identification of south-western Indian Ocean zooplankton. It has been compiled because much of the identification literature covering this area of amazing biodiversity is currently spread through the scientific literature and not easily accessible without extensive library resources. The guide was produced in a limited time period, so some specialist groups have not been dealt with in great detail. However, we hope to gradually extend the guide to fill any gaps. We would welcome any comments and corrections (please contact Dr Dave Conway at [email protected]). Background to the DEFRA Darwin Initiative, Zooplankton Project The Mascarene Plateau is a 2,200 km crescent-shaped ridge that runs roughly north-south from the Seychelles Bank to the island of Mauritius. The ridge’s islands, banks and shoals form a barrier modifying predominantly westward passage of the South Equatorial Current and waves across the Indian Ocean. The ridge shallows to less than 30m in many areas of the banks at the north of the plateau and places, where the depth of the plateau is less than 200m can be more than 250km wide. The Mascarene Plateau is a rare example of an extensive shallow-shelf sea completely detached from land boundaries, and is a large, almost completely unexplored marine ecosystem. Because it is a little studied region, the Royal geographical Society (with the institute of British geographers) and Royal Society set up the Shoals of Capricorn marine programme. The purpose of the research, coupled with education and training, was to help with sustainable development and conservation of the marine and coastal environments of the Seychelles and Mauritius, including the off lying island of Rodrigues. A second aim was to develop a better picture of how the Mascarene ridge affects water flows and ecological processes in a key global ocean-climate system – the western Indian Ocean. In April 2000, the UK (DEFRA) Darwin Initiative funded a joint training and research programme between local agencies in Mauritius and Seychelles, the Shoals of Capricorn programme and Plymouth Marine Laboratory with the Marine Biological Association. The programme, called Biodiversity in the basement of the marine food web, was to focus on the zooplankton of the Mascarene Plateau. One of the project’s primary objectives was, for the first time, to identify important zooplankton species around the Seychelles and Mauritius and start local training and research programmes to monitor plankton diversity and abundance. When the Shoals of Capricorn field programme formally came to an end in November 2001, the Shoals bases were handed over to the host nations. In the Seychelles this was undertaken by the new Seychelles Centre for Marine Research and Technology – Marine Parks Authority (SCMRT– MPA) under the Ministry of Environment, and in Rodrigues through a new non- governmental organisation, Shoals Rodrigues, associated with the Mauritius Oceanography Institute (MOI). At the same time the management of the Darwin project was passed to the Plymouth Marine Laboratory (PML). 4 The zooplankton Darwin Initiative project ended in 2003 with a regional conference and workshop in the Seychelles to consolidate the three years of research and training, as well as to help map out strategies for each regional team. The workshop was used to launch this “Guide to the coastal and surface zooplankton of in the South Western Indian Ocean”. Sampling programme A weekly zooplankton sampling programme was started in September 2000 in both the Seychelles and Rodrigues. The sampling equipment used is a conical 0.4 m diameter hand net of 125 mm mesh aperture, fitted with a General Oceanics (GO) flowmeter. Because the stations are shallow and over coral, the net is towed on a horizontal haul for at least 5 minutes at approximately 5 m depth. Whenever possible, temperature and salinity measurements are taken in association with the hauls and records kept of meteorological conditions. Zooplankton samples are preserved in 4%, borax buffered formaldehyde. Zooplankton is being identified to as precise a taxonomic detail as possible and counted using sub-sampling techniques. Counting of samples is also being carried out at both sites using an Optical Plankton Counter (OPC), which also gives zooplankton volumes, which can then be used to estimate biomass. The plankton net mesh size of 125µm was specifically chosen, as it samples organisms to the lower end of the size discrimination of the OPC. This net also efficiently samples the small copepods, which compose the bulk of the zooplankton biomass at the surface and in the coastal regions of these tropical waters. In the Seychelles three stations are sampled for zooplankton, one off the capital Victoria (outside the immediate influence of the harbour), the second off the island of St Anne and the third in more open water, outside the small island of Seche. In Rodrigues one station is sampled, in water of 12 m deep, just beyond the reef edge, outside the shipping channel leading into the capital, Port Mathurin. Sampling stations were chosen to be accessible, except in extreme weather, and which were under the influence of both the reefs and open sea. Sampling is carried out, for safety reasons, only during the day and close to high water, to standardise sampling conditions as closely as possible. Scope of this guide This guide attempts to cover all pelagic zooplankton species sampled in the Seychelles and Rodrigues. However, it also includes information from ancillary sampling carried out using a Continuous Plankton Recorder (CPR) towed from HMS ‘Beagle’, south-east of the Seychelles, from 08°58'S, 59°41'E to 05°28'S, 55°45'E in February 1999, as well as samples taken between Seychelles and Rodrigues on the research yacht ‘Zuza’ in April 2001 and from some samples taken close to Aldabra in February 2001. We have also included species recorded from inshore zooplankton studies in Madagascar (Furnestin & Radiguet, 1964; Gaudy, 1967; Binet & Dessier, 1968; Patriti, 1970). This guide therefore includes a high proportion of the island- coastal and surface water zooplankton of the south-western Indian Ocean. The location where a particular species has been sampled has been noted. Some species, that have not been sampled but that are known to occur in the region, have been included. For some specialist groups, which we did not have time to fully identify, a selection of representative members have been given, so that organisms can at least be assigned to perhaps a particular genus within the main group.