Phylum: Arthropoda
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PHYLUM: ARTHROPODA Authors Charles Griiths1, Jannes Landschof1 and Lara Atkinson2 Citation Griiths CL, Landschof J and Atkinson LJ. 2018. Phylum Arthropoda In: Atkinson LJ and Sink KJ (eds) Field Guide to the Ofshore Marine Invertebrates of South Africa, Malachite Marketing and Media, Pretoria, pp. 133-226. 1 Marine Research Institute and Department of Biological Science, University of Cape Town 2 South African Environmental Observation Network, Egagasini Node, Cape Town 133 Phylum: ARTHROPODA Sub-phyla Crustacea and Chelicerata Crabs, prawns, lobsters, barnacles, mantis shrimps, isopods, pycnogonids, etc. The Phylum Arthropoda includes all animals which have become sessile, have reduced body which have an external skeleton (exoskeleton), a parts and are usually encased by calcareous segmented body, and jointed appendages. It is by plates. far the most diverse of all phyla, incorporating over • Class Malacostraca: The largest class and 80% of all described species. The Phylum is divided divided among many orders, of which the into ive Sub-phyla, as follows: following are addressed in this guide: • Sub-phylum Trilibitomorpha: Trilobites - Order Stomatopoda: Mantis shrimps (extinct). (35 species known in the region). • Sub-phylum Chelicerata: Spiders and - Order Tanaidacea: Tanaids (19 species horseshoe crabs, of which only the Class known in the region). Pycnogonida is briely considered in this guide. - Order Isopoda: Isopods (over 300 species • Sub-phylum Myriopoda: Centipedes and known in the region). millipedes, entirely terrestrial, so not covered in - Order Amphipoda: Amphipods (over 450 this guide. species known in the region). • Sub-phylum Hexapoda: Insects and their - Order Decapoda: Prawns, lobsters, hermit allies, primarily terrestrial or freshwater, almost crabs, crabs, etc., which include most of completely absent from marine habitats and not the larger-bodied Crustacea and form the covered in this guide. majority of species addressed in this guide. • Sub-phylum Crustacea: Crabs, prawns, etc., the Over 750 species are recorded from South main group considered within this guide. Africa. Sub-phylum Crustacea The order of species pages presented in this guide Crustaceans are characterised by having a may not necessarily follow strict phylogenetic segmented body, a chitinous exoskeleton, paired relationships, but are presented based on supericial jointed limbs and two pairs of antennae. They similarity to enable better comparisons during ield include such well-known groups as crabs, prawns, identiication. hermit crabs, lobsters and barnacles. Most are free-living and aquatic, but some are terrestrial Collection and preservation (e.g. woodlice), parasitic (e.g. some barnacles and In the ield, or on board a vessel, crustaceans are isopods), or sedentary (barnacles). There are about best preserved by freezing specimens in individual 67 000 known species globally and over 2 300 marine plastic bags with labels. Specimens should be species have been described from South African packaged with protection padding and in hard waters, with many more remaining undescribed. plastic containers to protect them from breakage. This is best done by packing small groups of samples The major subgroups consided here are the into larger jars, rigid cardboard boxes, buckets with following: lids, or crates. Alternatively, specimens can be frozen • Class Ostracoda: Small, body enclosed in an in a jar or container illed with seawater. oval or round bivalved carapace. Planktonic or benthic in both marine and freshwater. About Samples can also be preserved in 70% ethanol, but 45 marine species are known from South Africa. as colour can be important for identiication and • Class Hexanauplia: This recently recognised quickly fades in alcohol, specimens that might be of group includes both the more familiar Subclass taxonomic signiicance should irst be photographed Copepoda (copepods: small but very abundant to record their natural colours. Include the specimen and diverse planktonic or benthic animals, label and, if possible, a scale bar in photogaphs, about 430 South African marine species, which are best taken against a plain black or white not covered in this guide) and the Infraclass background. Cirripedia (barnacles; 86 South African species), 134 Phylum: Arthropoda References Barnard KH. 1950. Descriptive catalogue of South African decapod Crustacea. Annals of the South African Museum 38: 1-837. Bianchi G, Carpenter KE, Roux J-P, Molloy FJ, Boyer D and Boyer HJ. 1999. FAO species identiication ield guide for ishery purposes. Field guide to the living marine resources of Namibia ISSN 1020-6868 Norwegian Agency for International Development, Food and Agriculture Organization of the United Nations, Rome. Biccard A and Griiths CL. 2016. Additions to the barnacle (Crustacea: Cirripedia) fauna of South Africa. African Zoology 51(2): 99-116. Debelius D. 1999. Crustacea: Guide of the World. IKAN, Frankfurt. 321pp. Emmerson WD. 2016. A Guide to, and Checklist for, the Decapoda of Namibia, South Africa and Mozambique. Cambridge Scholars Publishing, Newcastle upon Tyne. (3 volumes). Griiths CL. 1976. Guide to the Benthic Marine Amphipods of Southern Africa. Trustees of the South African Museum, Cape Town, 106pp. Kensley B. 1978. Guide to the Marine Isopods of Southern Africa. Trustees of the South African Museum, Cape Town, 173pp. Prawn external anatomy terminology Carapace Pleon 1-6 pleonal segments Post-orbital spine Rostrum Pleura Flagella Gastric region Cardiac region Dorsal crest Antennule Telson Tail Pleopods fan Uropod Pereopods 135 Phylum: Arthropoda Crab (Brachyura) external anatomy terminology Dactyl (movable inger) 1 Chela (claw/hand) Fixed inger 2 Propodus Palm Carpus 3 Eye Merus Frontal region Anterolateral teeth Pereopods 1-5 Gastric region Lateral spine Posterior margin Cardiac region 4 Coxa Basi-ischium Merus Carpus Carapace Propodus Swimming leg 5 Dactyl Hermit crab external anatomy terminology 1st pereopod (cheliped) 2nd antenna 1st antenna Dactylus Propodus Eyestalks Carpus 2nd pereopod Shield Merus 4th pereopod 5th pereopod 3rd pereopod Pleon Telson Pleopod 5 Pleopod 3 Pleopod 4 136 Phylum: Arthropoda Pycnogonid spp. (Pycnog) Phylum: Arthropoda Subphylum: Chelicerata Class: Pycnogonida Order: Pantopoda Suborder: - Family: Various Genus: ‘Pycnogonid’ Species: - Common name: Sea spiders 60 mm 90 mm Distinguishing features Size Pycnogonids (sea spiders) have small bodies with Variable. From a few millimetres up to 140 mm in long, spider-like legs. Most have four pairs of jointed diameter (in South Africa). walking legs, although some species are known to have ive or six pairs of legs. Body form consists of a Distribution cephalon and a trunk which has four body segments, Ubiquitous in benthic habitats. each segment bearing a pair of legs. The cephalon bears a proboscis, a pair of chelifores, a pair of palps Similar species and a pair of ovigerous legs (ovigers). Ovigers are a Unlikely to be confused with any other group, except feature unique to Pycnogonida. perhaps Inachidae spider crab species, which have ive pairs of slender, long legs. Offshore South African pycnogonids from Iziko Museum, identiied by David Staples, are classiied References into three families: Pallenopsidae, Callipallenidae, Bamber RN, El Nagar A and Arango CP. (eds). 2018. and Nymphonidae. However, for purposes of Pycnobase: World Pycnogonida Database. Accessed research trawl surveys, all pycnogonids are grouped at http://www.marinespecies.org/pycnobase on together under the FishBoard code ‘Pycnog’. 2018-03-01. Colour Barnard KH. 1954. South African Pycnogonida. Variable, but usually orange, yellow or red. Annals of the South African Museum 41: 81-159. 137 Phylum: Arthropoda Ostracods (Ostra) Phylum: Arthropoda Subphylum: Crustacea Class: Ostracoda Order: Various Suborder: - Family: Various Genus: ‘Ostracod’ Species: - Common name: Ostracods 20 mm 15 mm Distinguishing features Distribution Small crustaceans, body completely enclosed in Ubiquitous in benthic and pelagic habitats. bivalved carapace, hence common name ‘mussel shrimps’ or ‘seed shrimps’. Usually round or oval in Similar species outline, most are smooth, but some extravagantly South African benthic marine ostracods are poorly ridged or spiked. Some have conspicuous antennal known and in urgent need of revision. notch (Order Myodocopa, shown here). Swim using elongate antennae. Can be planktonic or Reference benthic and have various feeding habits, including Stebbing TRR. 1910. General Catalogue of South carnivores, grazers, scavengers and ilter-feeders. African Crustacea. Annals of the South African Museum 6: 281-593. Colour Usually white to yellow, sometimes pink/orange organs visible through carapace. Size Up to 15 mm diameter, mostly much smaller (<5 mm). 138 Phylum: Arthropoda Stalked barnacles (BarSta) Phylum: Arthropoda Subphylum: Crustacea Class: Hexanauplia Order: Lepadiformes Suborder: - Family: Various Genus: ‘Stalked barnacles’ Species: - Common name: Stalked barnacles 20 mm 15 mm Distinguishing features Distribution Diverse group of barnacles, most commonly Entire region, surface to abyssal depths. encountered attached to loating objects (‘Goose barnacles’), but in benthic habitats also often found Similar species attached to rocks, crustaceans, corals, hydroids, The two species shown (Verum porcellanum, left, and polychaete tubes, etc. Filter-feeding appendages Poecilasma kaempferi, right) both attach to crabs and project from laterally-flattened body, which is are fairly well known,