KINGDOM ANIMALIA

I. SYNONYMS: crustaceans, arthropods.

II. NUMBER: >39,000 species known.

II. PHYLUM CHARACTERISTICS:

A. Structure

Symmetry: Bilateral; segmented body regions organized into head, thorax and abdomen.

Body Cavity: True coelom reduced and absent in adults. Haemocoel the only body cavity.

Body Covering: Covered by chitinous and often calcified exoskeleton.

Support: Hardened exoskeleton.

Digestive System: Food tube simple. Mouth at anterioventral end flanked by modified legs that serve as mandibles and a terminal anus on the telson (last body segment). Digestive gland formed of a pair of diverticula which serves as a hepatopancreas.

Circulatory System: Open. Haemocoel of blood sinuses with a dorsal heart. Respiratory pigments (haemocyanin or erythrocruorin) in the plasma.

Locomotion: Segments of the thorax and abdomen equipped with pairs of jointed appendages. Those of the abdomen are usually non-ambulatory or absent. Each appendage has a basal protopodite, an inner endopodite and and outer exopodite.

Excretory System: Glands comprising a closed end sac and a tubule located in one or more pairs of appendages (antennae, 2^nd maxillae, etc.).

Nervous System: A circumesophagial ganglion, a pair of ventral nerve cords, usually connected by ganglia at each segment. Sensory organs may be complex; compound eyes, antennae and sensory hairs.

Endocrine System:

Respiratory System: Modifications of appendages that function as gills. Respiratory pigments in the plasma.

B. Reproduction:

Reproductive System: Dioecious. Gonads paired. Fertilization internal. Oviparous.

Development: Zygote develops by modified spiral cleavage. Eggs hatch into nauplius larva with three pairs of appendages (antennules, antennae, and mandibles) and a median compound eye. Successive segments added as the larva molts, usually many times until an adult.

C. Ecology: Mostly free-living, terrestrial and aquatic (marine and freshwater). Most found in the oceans.

CLASS REMIPEDIA (1 ORDER)

At present, this class is made of 12 cave-dwelling species with an interesting mix of primitive and advanced characters.  Body composed of a head covered by a cephalic shield and a very long, 32-segment trunk, each segment with a pair of biramous legs.  The body is not covered by a carapace.  Last segment partly fused and with a telson.  Mouth with unusual poison-injecting fang.

Cryptocorynectes, Godzillus, Lasionectes, Pleomothra, Speleonectes.

CLASS CEPHALOCARDIA (1 ORDER)

Head covered by a cephalic shield to form a horseshoe-shaped head, 8-segmented thorax; 11-segmented abdomen with telson. Antennule uniramous; 1^st 7 thoracic limbs triramous, with large, flattened pseudepipodite; abdomen without appendages except caudal furca with long bristles.  They have no carapace or eyes.  Hermaphroditic, with separate paired testes and ovaries discharging through common ducts; benthic, marine.

Hampsonellus, Hutchinsoniella, Lightiella, Sandersiella.

CLASS BRANCHIOPODA (3 ORDERS)

Usually small; with short body (number of segments varies), reduced, unsegmented antennule, leaf-like thoracic legs with epipodal gills; maxillae small, 2^nd maxillae often absent; without abdominal appendages except caudal furca; characteristic nauplius larva with numerous segments and further appendages added at each molt; carapace (when present) forms bivalved shell; compound eyes in combination with simple eyes usually present; females often parthenogenetic; sexually produced resistant eggs produced when conditions become adverse. Mostly freshwater; some in hypersaline environments.

Artemia, Brancionecta, Branchiella, Streptocephalus, Eubranchipus, Triops, Lepidurus, Lynceus, Cyzicus, Eulimnadia, Imnadia, Metalimnadia, Cyclestheria, Anchistropus, Daphnia, Moina, Polyphemus, Leptodora, Bosmina, Chydorus.

CLASS MALACOSTRACA

Small to very large; often with heavily calcified exoskeleton; 5 cephalic, 8 thoracic, and 6 (sometimes 7) abdominal segments; usually with stalked, compound eyes; carapace covering thorax (part or all) but never covering more than 1^st or 2^nd abdominal segments; first 1-3 pairs of thoracic appendages forming maxillipeds, 5 or more posterior pairs forming walking or swimming legs (pereiopods), 1+ pairs often chelate; abdomen with appendages (pleopods) modified for swimming and reproduction (sometimes for respiration), last pair (uropods) broad, forming tail fan with telson; fertilized eggs often brooded.

SUBCLASS PHYLLOCARDIA (1 ORDER)

The only malacostracan group with 7 abdominal segments; all thoracic appendages phyllopodous; carapace covers thorax and laterally compressed; head with moveable rostrum; antennules biramous and antennae uniramous.

Dahlella, Levinebalia, Nebalia, Nebaliella, Nebaliopsis, Paranebalia.

SUBCLASS EUMALACOSTRACA (13 ORDERS IN 4 SUPERORDERS)

Body segments - 5 head, 8 thoracic, and 6 abdominal; 0-3 thoracic segments fused with the head; antennules and antennae bi- or uniramous; antennae often with exopod; carapace well-developed; thoracic epipods function as gills; abdomen usually long and muscular.

Anaspides, Paranaspides, Koonunga, Bathynella, Thermobathynella

Thermosbaena, Monodella, Spelaeogriphus, Mysis, Neomysis, Gnathophausia, Cumopsis, Leptocuma, Diastylis, Cyclaspis, Aspeudes, Sphyrapus, Tanais, Heterotanais, Oniscus, Porcellio, Armadillidium, Ligyda, Asellus, Idotea, Arcturus, Gnathia, Cymnothoa, Bathynomus, Ione, Liriopsis, Phreatoicus, Gammarus, Hyallela, Orchestia, Caliopius, Siphonectes, Hyperia, Caprella, Ingolfiella.

Euphausia, Meganyctiphanes, Nyctiphanes, Lucifer,Penaeus, Crangon, Heterocarpus, Stenopus, Callianidea, Callianassa, Polyonyx, Callinectes, Uca, Neopanopeus, Cambarus, Cambarellus, Homarus, Clibanarius, Emerita, Sesarma.

Squilla, Echinosquilla, Gonodactylus, Hemisquilla, Lysiosquilla, Pseudosquilla, Coronida, Odontodactylus.

CLASS MAXILLOPODA

Segments- 5 head, 6 thoracic, 4 abdominal (sometimes the body plan is reduced); thoracic appendages usually without epipods; abdomen reduced and lacking "full compliment of legs".  In general, they appear to be neotenic, that is larval in form as sexually mature adults which accounts for their variability in form.  There still is some disagreement as to the monophyly of this group.  Some systems exclude the Ostracods.

SUBCLASS THECOCOSTRACA (CIRRIPEDIA) (4 ORDERS)

Free-living or parasitic; adults sessile; parasitic forms highly modified. Free-living forms attached to substratum by cement from antennules; carapace covering body and limbs, often with discrete calcareous plates; reduced abdomen and segmentation; 6 pairs of biramous thoracic limbs (cirri) used to comb or filter water; adults without antennae or compound eyes; mostly hermaphroditic with cross-fertilization by elongate penis. Marine.

Conchoderma, Lepas, Balanus, Mitella, Tripetesa, Baccalaureus, Dendrogaster, Ascothorax, Laura, Sacculina, Synagoga, Zoanthoecus, Briarsaccus, Loxothylacus, Hansenocaris, Cryptophialis, Typetesa, Heterosaccus, Lernaeodiscus, Mycetomorpha, Peltogaster, Sylon, Chthamalus, Coronula, Pollicipes, Tetraclita, Verruca,

SUBCLASS TANTULOCARDIA (1 ORDER)

Parasites of other crustaceans; free-swimming larval forms with flattened cephalic, shield thorax of 6 segments, and abdomen of up to 7 segments; abdomen without appendages; adults reduced to a sac, reduced abdomen and sex organs.

Basipodella, Doeterthron, Microdajus.

SUBCLASS BRANCHIURA (1 ORDER)

Flattened ectoparasites of fish; carapace covers head and most of body; with 3 free thoracic segments, paired moveable compound eyes, median ocellus, bilobed unsegmented abdomen; 1^st maxillae form suckers; antennules with large terminal hook. Attachment to host periodic, biramous thoracic limbs used for locomotion.

Argulus, Chonopeltis, Dipteropeltis, Dolops.

SUBCLASS PENTASTOMIDA (See PHYLUM PENTASTOMA)

I have omitted this group from the taxonomy of Brusca and Brusca (2003) and set it apart as a separate phylum.

SUBCLASS MYSTACOCARDIA (1 ORDER)

Minute, elongate; head divided into 2 regions; without compound eyes, with 2 pairs of ocelli; 4 pairs of simple, singly-segmented appendages on thoracic segments 2-5; antennules, antennae and maxillae large; appendages of 1^st thoracic segment form maxillipeds; abdomen 5-segmented plus telson with large, claw-like furca; pairs of dentate furrows laterally on posterior head, thorax and abdomen; benthic, marine.

Ctenocheilocaris, Derocheilocaris.

SUBCLASS COPEPODA (10 ORDERS IN 2 INFRACLASSES)

Usually small; short body composed of a head fused to 1+ thoracic segments and 8 free segments plus telson (with further fusion in some); with carapace or paired eyes; with well-developed nauplius eye; uniramous antennules, appendages of 1^st thoracic segment forming maxillipeds, and 4-5 other pairs of thoracic appendages; body often with rounded anterior margin, oval head + thorax, narrow abdomen ending in caudal furca; commensal, free-living and parasitic, parasitic species highly modified.

Antrisocopia, Platycopia.

Calanus, Diaptomus, Eucalanus, Euchaeta, Metridia, Calocalanus, Cyclops, Eucyclops, Lernaea, Mesocyclops, Metacyclops, Notodelphis, Gelyella, Harpacticus, Elaphoidella, Epactophanes, Longipedia,  Monstrilla, Peltidium, Porcellidium, Psammus, Sunaristes, Tisbe, Boxshallia, Misophrya, Monstrilla, Stilloma, Mormonilla, Chondracanthus, Erebonaster, Ergasillus, Pseudanthessius, Clavella, Nemesis, Pontoeciella, Trebius, Acidicola, Notodelphys, Doropygus, Penella, Lepeophtherius, Samnicola, Branchiella.

SUBCLASS OSTRACODA (5 ORDERS IN 2 SUPERORDERS)

Small, enclosed in a bivalved carapace; body unsegmented externally, with 5-7 pairs of thoracic limbs; carapace shed and reconstituted at each molt.

Cypridina, Euphyllomedes, Eusarsiella, Pyrocypris, Gigantocypris, Skogsbergia, Vargula, Conchoecia, Polycope.

Cypris, Candona, Celtia, Darwinula, Limnocythre, Cytherella, Sclerocypris, Manawa, Bairdia, Bythocypris.