Key:  Suborder Epicaridea

Phylum Arthropoda
  Subphylum Crustacea
    Class Malacostraca
      Subclass Eumalacostraca
        Superorder Peracarida
         Order Isopoda

Taken primarily from  Kozloff, 1987, 1996 p. 341 (Copyright 1987, 1996, University of Washington Press.  Used in this web page by permission of University of Washington Press)
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1a  Protandrichermaphrodites in which the last larval stage (cryptoniscus), after functioning as a free-living male, becomes transformed into a parasitic female; this loses all or most appendages and becomes hypertrophied in such a way that the body has 2 to several lobes (section Cryptoniscina) 2
1b Sexes separate and both parasitic, the male being much smaller and more isopodlike than the female (there is usually a male closely associated with each female)(section Bopyrina) 3
2a Parasitic in barnacles (Balanus glandula, Chthamalus dalli); adult female conserving only the cephalon and some of the more anterior segments of the cryptoniscus, the rest of the body consisting of several lobes; basal article of antenna 1 and coxal plates of male toothed Hemioniscus balani
2b Hyperparasitic on the rhizocephalans Peltogaster paguri and Peltogasterella gracilis, which are parasites of hermit crabs; adult female, after a period of completely internal parasitism, becomes constricted into 2 nearly spherical portions, the anterior one being buried in the host, the posterior one being external; basal article of antenna 1 and coxal plates of male smooth Liriopsis pygmaea
3a Endoparasitic (not visible externally) in the visceral cavity of the crabs Hemigrapsus oregonensis and H. nudus (body of female bent into a V, the cephalon divided into 2 hemispheres, the pereopods reduced to stubs, the pleon with 5 pairs of wrinkled lateral lobes; male with only 6 pairs of pereopods Portunion conformis
3b Ectoparasitic, either located in the branchial chamber of the crustacean host, attached to the dorsal surface, or attached to the underside of the abdomen 4
4a Attached to the dorsal surface of the host, which is either a decapod or mysid (female asymmetrical, with only 5 pairs of pereopods, these grouped around the oral region, and with most of the posterolateral portion covered by a pair of enlarged oostegites) 5
4b In the branchial chamber or under the abdomen of decapod crustaceans 7
5a Parasitic on the shrimp Pasiphaea pacifica; female with all pereonites and pleonites fused or so nearly fused that they are indistinct (male with pleonites fused) Holophryxus alaskensis
5b Parasitic on mysids (possibly other planktonic crustaceans); female with at least some pereonites and pleonites distnct dorsally 6
6a Female with all pereonites and pleonites distinct dorsally (male with all pleonites distinct)(parasitic on the mysid Eucopia australis, collected in very deep water, and perhaps associated with other mysids) Arthophryxus beringanus
6b Female with pereonites 1-3 and pleonites distinct dorsally (type specimen found in a collection of mysids from very deep water) Prophryxus alascensis
7a Female symmetrical or only slightly asymmetrical, with all pereonites distinct, and with 5 pairs of nearly equal oostegites; female with 7 pars of pereopods and generally with 6 distinct pleonites 8
7b Abdominal parasites of shrimps in the genera Lebbeus, Spirontocaris, Eualus, and Heptacarpus; female very asymmetrical, with pereonites not completely separated dorsally; on the swollen side, the oostegites are large and form a closed brood pouch, and generally only pereopod 1 persists; on the nearly straight side, oostegites 2-4 are reduced to small plates and there are 7 pereopods; pleon with 5 pleonites, 4 pairs of leaflike lateral plates, and small uniramouspleopods; male with fused pleonites Hemiarthrus abdominalis
8a Parasitic on the underside of the abdomen of the thalassinid Upogebia pugettensis (pleon of female without lateral plates but with well developed biramous pleopods and uniramous uropods; pleon of male with lateral plates) Phyllodurus abdominalis
8b Parasitic in the branchial chamber of thalassinids, hermit crabs, galatheids, and shrimps of the families Crangonidae, Hippolytidae, and Pandalidae 9
9a On the thalassinid Neotrypaea californiensis; pleon of female with 6 pairs of lateral plates which are long and thin and whose posterior margins are fringed by slender outgrowths (brood pouch of female closed; pleon of male with elongated lateral plates but these are not fringed) Ione cornuta
9b On hermit crabs, galatheids, or shrimps; pleon either with 5 pairs of lateral plates, with rudimentary plates, or without any plates 10
10a Pleon with 5 pairs of lamellar and smooth lateral plates; brood pouch closed; pleonites of male fused or not fused 11
10b Pleon either without lateral plates or with rudimentary plates; brood pouch open; pleonites of male fused (photo) 13
11a On the galatheid Munida quadrispina (see also choice 12b); female with 2 pars of lateral lamellae on the posteroventral border of the cephalon; coxal plates of the pereon well developed; pleopods visible when the animal is viewed from the dorsal side; pleotelson elongated and swollen near its tip and bearing biramous uropods; pleonites of male fused Munidum parvum
11b Female with 1 pair of lateral lamellae on the posteroventral border of the cephalon; pereon without coxal plates; pleopods not visible when the animal is viewed from the dorsal side; pleotelson short, rounded or truncate at its tip and bearing uniramousuropods; pleonites of male not fused 12
12a On hermit crabs; endopodites of pleopods of female much longer than the exopodites, their surfaces more or less tuberculated Pseudione giardi
12b On the galatheid Munida quadrispina (see also choice 11a); endopodites of pleopods of female only slightly longer than the exopodites, their surfaces smooth Pseudione galacanthae
13a On shrimps of the family Crangonidae (Crangon, Argis); female with well developed biramouspleopods and uniramousuropods Argeia pugettensis
13b On shrimps of the families Hippolytidae (Spirontocaris, Eualus, Heptacarpus) and Pandalidae; female either without pleopods or with pleopods reduced to tubercles, and without uropods Bopyroides hippolytes

Taxonomic Levels Represented in This Key:

  Bopyroides hippolytes
  Orthione griffenis

Page created by Dave Cowles, 2008
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