Idotea Wosnesenskii Class: Malacostraca Order: Isopoda Family: Idoteidae

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Phylum: Arthropoda, Crustacea Idotea wosnesenskii Class: Malacostraca Order: Isopoda Family: Idoteidae

Taxonomy: The genus Idotea was described pod”). Posterior to the pereon is the pleon, or by Fabricius in 1798, and although originally abdomen, with six segments, the last of which spelled Idotea, several authors adopted the is fused with the telson (the pleotelson) (see spelling Idothea, since then. The genus Plate 231, Brusca et al. 2007). The Isopoda Pentidotea was described by Richardson in can be divided into two groups: ancestral 1905 and was reduced to subgeneric level by (“short-tailed”) groups (i.e. suborders) that Menzies in 1950. The two subgenera (or have short telsons and derived (“long-tailed”) genera), Pentidotea and Idotea differ by the groups with long telsons. Valviferan articles on maxilliped palps, the former with (including the Idoteidae) isopods have an five and the latter with four (Miller and Lee elongated telson (Fig. 73, Ricketts and Calvin 1970), but are not always currently 1952). Idotea wosnesenskii individuals are recognized (Rafi and Laubitz 1990). robust, not tapered, elongate and depressed Furthermore, this character may vary with age (see Fig. 62, Ricketts and Calvin 1952). and other characters may reveal more Cephalon: Wider than long, with frontal concrete differences to define the two (Poore margin slightly concave (Miller 1968) and and Ton 1993). Thus synonyms for I. posterior portion somewhat wider than wosnesenskii include, Idothea wosnesenskii, anterior portion (Richarson 1905). Head Pentidotea wosnesenskii and Idotea narrower than pleon (Schultz 1969). First Pentidotea wosnesenskii. We follow the most thoracic segment fused with head (Isopoda, recent intertidal guide for the northeast Pacific Brusca et al. 2007). coast (Brusca et al. 2007), which uses the Rostrum: Frontal process widely name Idotea wosnesenskii. angulate and hidden by and not extending beyond frontal lamina, which is triangulate (in Description dorsal view) (Fig. 2). Size: Individuals to 35 mm in length (Hatch Eyes: Eyes small, reniform (kidney- 1 1947) and ½ to /3 as wide as long (Fee 1927; shaped) (Miller 1975) (Fig. 4), compound, Ricketts and Calvin 1952). The figured transversely ovate and situated at extreme specimen (male) is 22 mm long. A 22-mm lateral margins (compare to M. entomon, this male weighs approximately 0.3 grams and a guide), about halfway between the anterior similar sized female weighs 0.2 grams (wet and posterior margins (Fig. 1). weight). Antenna 1: First antennae Color: Dark green or light olive and some (antennules) with four articles, basal one individuals living amongst red algae are dark large and flattened. red and gray (Fee 1927). Males tend to be Antenna 2: Second antennae with larger and paler than females (Welton and peduncle of five articles and flagellum of 12– Miller 1980). Color polymorphism is high in 16 articles (Fig. 1). the congener, I. baltica and variation is Mouthparts: Maxilliped palp with five determined by habitat and predation pressure articles and one coupling hook (Miller 1975). but not sexual selection (Jormalainen and Pereon: Body elongate and depressed with Merilaita 1995). thorax composed of seven segments (Brusca General Morphology: Isopod bodies are et al. 2007). dorso-ventrally flattened and can be divided Pereonites: All seven thoracic into a compact cephalon, with eyes, two somites (pereonites) are free (Idoteidae) with antennae and mouthparts, and a pereon epimeral sutures visible dorsally (except the (thorax) with eight segments, each bearing first somite) (Fig. 1). Postero-lateral border of similar pereopods (hence the name “iso- last pereonite acute (Fig. 1).

Pereopods: Seven pairs of developed coxal plates, the absence of ambulatory and similar walking legs. mandibular palps, occasionally fused Pleon: Short pleon with six pleonites (Brusca pleonites and males with modified sexual et al. 2007). Pleon with two complete and appendages arising from the first pleonite, one partial intersegmental suture dividing it rather than the thorax. This suborder into three divisions. Pleon wider than head includes three local families and 34 species: (Schultz 1969). the Chaetiliidae (see Mesidotea entomon, Pleonites: Two small anterior this guide), the Arturidae and the Idoteidae. pleonites and a large shield-like pleotelson The Arturidae is composed of species with with an incompletely fused pleonite near its narrow but cylindrical bodies, with the base (Fig. 1) (Miller 1975). The first pleonite anterior four pleopods larger and less setose with acute lateral borders and shorter laterally than the posterior three. Characteristics of than medially (Miller 1975; Kozloff 1974) (Fig the Idoteidae include a dorso-ventrally 1). compressed body, similar pereopods, and Pleopods: Seven pleopod pairs are seven free pereonites and is composed of 22 ambulatory, nearly similar and all with small species, locally (Brusca et al. 2007). sharp claws. Male pereopods with coarse Most local species in the Idoteidae are hairs (Figs. 1, 4) and females with hair only on within the genus Idotea (12 species), which propodi. Appendages of the pleon include includes those with a pleon composed of two five respiratory pairs and a single pair of complete and one incomplete pleonite(s), a uropods (Brusca et al. 2007). The first three maxillipedal palp with five articles and one pairs are particularly locomotory (e.g. for coupling seta, eyes that are not elongated swimming), while the posterior two pairs are transversely and a large shield-like pleotelson strictly respiratory (Alexander 1988; (Brusca et al. 2007). Idotea sensu Poore and Alexander et al. 1995), although all five pairs Ton 1993 refers only to individuals with free can also function in ventilation as water is pleonites, anterior spiniform pereopod setae passed through the branchial chamber with a and free penes, while many northeastern total of three strokes (Alexander 1991). Pacific species have fused pleonites, partially Uropods: Ventral, not visible dorsally, and fused penes and reduced coxae (Poore and forming opercular plates or valves. Ton 1993). Based on these characters, Pleotelson: Large, shield-like, broadly authors differentiate Idotea from Pentidotea rounded (Hatch 1947), and ends in large blunt (see Taxonomy). point (Fig. 1). Among the Idotea, I. urotoma, I. Sexual Dimorphism: Conspicuous sexual rufescens, and I. ochotensis have a dimorphism is rare among isopods, however, maxilliped palp with four articles (rather than males tend to be larger, paler, and have five in the remaining eight Idotea species) a hairier legs than females in I. wosnesenskii. character that previously defined two sub- Mature females are broader and bear a genera, Idotea Idotea (with four articles) and thoracic marsupium while males have Idotea Pentidotea (with five articles) (Menzies modified first pleopods, called gonopods 1950; Miller and Lee 1970). (Sadro 2001; Boyko and Wolff 2014). Of the Idotea species with five maxilliped palp articles (Idotea Pentidotea, Possible Misidentifications Menzies 1950), I. aculeata, a reddish idoteid The order Isopoda contains 10,000 species, with a long projection on its narrowing 1/2 of which are marine and comprise 10 pleotelson. It has oval eyes (not reniform), suborders, with eight present from central long antennae and blunt lateral borders on California to Oregon (see Brusca et al. the first pleonite (compare to acute borders as 2007). Among isopods with elongated in I. wosnesenskii). Idotea montereyensis is telsons (with anuses and uropods that are slender and small (up to 16 mm), red, green- subterminal), there are several families brown, or black and white and is found on including Flabellifera, Anthuridea, Phyllospadix species and red algae. It has a Gnathiidea, Epicaridea and Valvifera. The rounded telson and with a short projection. It Valvifera are characterized by hinged doors differs from I. wosnesenskii in the frontal or valves covering the pleopods, well- process, which is narrow, pointed and

Hiebert, T.C. 2015. Idotea wosnesenskii. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Species, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR. projects much beyond the frontal lamina. The temperature barriers for other invertebrates frontal lamina is triangulate (compare to (Wallerstein and Brusca 1982). I. wosnesenskii, frontal process and Fig. 2). Tidal Level: Upper middle intertidal zone to Male I. montereyensis are long and slim and 16 m deep. The figured specimen was females are broader, and more like I. collected at 0.0 meters. wosnesenskii in outline. Idotea schmitti has Associates: Associates include the pleonite one with acute lateral borders as in I. gastropod Tegula, brachyurans Hemigrapsus wosnesenskii, but the anterior margin of species and Cancer oregonensis, and the pereonite one does not encompass the carnivorous gastropod, Nucella. Often co- cephalon. Idotea stenops is olive-green to occurs with mussel species in large clusters brown, found on brown algae and with narrow (Ricketts and Calvin 1952). eyes, a slender pointed telson, and 2–3 Abundance: Common and probably the coupling hooks on its maxillipeds, not one. most common idoteid isopod in Coos Bay Idotea kirchanskii is bright green and found (Kozloff 1974; Menzies 1950). Most common on Phyllospadix species. It has a rounded small crustacean in Santa Cruz, California telson (lacking a medial projection), oval eyes (Ricketts and Calvin 1952). and the epimera of pereonal somites are visible dorsally only on segments 5–7. Idotea Life-History Information resecata (this guide) has a very distinctive Reproduction: Most isopods have separate concave pleotelson that is not a rounded, but sexes (i.e. dioecious, Brusca and Iverson convex. 1985) (although protogynous and protandric species are known, Araujo et al. 2004; Boyko Ecological Information and Wolff 2014). Reproduction proceeds by Range: No exact type locality is given, but copulation and internal fertilization where region (based on noted locations in the eggs are deposited within a few hours after original species description) is likely Sea of copulation and brooded within the female Okhotsk and Bering Sea (Menzies 1950). marsupium (Brusca and Iverson 1985). The Known range from Sea of Okhotsk, Russia, biphasic molting of isopods allows for Bering Sea, Alaska (Menzies 1950), south to copulation; the posterior portion of the body San Luis Obispo, Calif. (Ricketts and Calvin molts and individuals mate, then the anterior 1952; Kussakin 1994). portion, which holds the brood pouch, molts Local Distribution: Oregon distribution in (Sadro 2001). Embryonic development Coos (e.g. at Pigeon Point) and Tillamook proceeds within the brood chamber and is Bays (Hatch 1947). direct with individuals hatching as manca Habitat: Substrates include rocks and pilings larvae that resemble small adults, with no (Puget Sound, Washington Kozloff 1974), but larval stage (Boyko and Wolff 2014). Little is individuals also occur under rocks on gravelly known about reproduction and development or sandy substrates with lots of vegetative in I. wosnesenskii specifically, but females are debris as well as in crevices and cracks, ovigerous in July (California, Welton and within empty shells and worm tubes (Brusca Miller 1980) and a few advanced (8 mm) et al. 2007). Also in mussel beds, on Ulva juveniles were found in female oöestigites in and Porphyra (Welton and Miller 1980). More April (Coos Bay). Idotea baltica and I. common on outer rocky shores than in chelipes produce 1–3 broods per year with estuaries (Menzies 1950; Ricketts and Calvin brood sizes that range from 60 to 120 eggs 1952). per brood (Limfjord, Denmark, Kroer 1989; Salinity: Tolerates salinity changes better Baltic, Jormalainen and Tuomi 1989). than I. resecata (Brusca 1966; Welton and Larva: Since most isopods are direct Miller 1980). Primary osmoregulation (i.e. developing, they lack a definite larval stage. inward ion transport) occurs with the Instead this young developmental stage endopodites of the posterior three pleopods resembles small adults (e.g. Fig. 40.1, Boyko (Holliday 1988). and Wolff 2014). Most isopods develop from Temperature: North Pacific Idotea species embryo to a manca larva, consisting of three exhibit a wide temperature tolerance as their stages. Manca larvae are recognizable by ranges extend across several zoogeographic lacking the seventh pair of pereopods, but provinces that are associated with otherwise resemble small adults. They

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12716 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] usually hatch from the female marsupium at 2014). Regarding the intertidal alga, Iridaea the second stage and the molt from second to cordata, Idotea wosnesenskii only fed on third manca produces the seventh pair of reproductively mature plants (Gaines 1985). pereopods and sexual characteristics (Boyko A feeding rate of approximately 3 mg per day and Wolff 2014). Isopod development and of the unicellular epiphytes, Isthmia nervosa larval morphology can vary between groups and Odonthalia floccosa (Ruesink 2000) was (e.g. Gnathiidae, Cryptoniscoidea, reported and overall, algal feeding rates in Bopyroidae, Cymothoidae, Oniscoidea) (see Idotea species can range from 0.1–71.3 mg Boyko and Wolff 2014). Parasitic isopods, for per individual per day (Trowbridge 1993). example, have larvae that are morphologically Idotea wosnesenskii is not negatively affected dissimilar from adults (Sadro 2001). Isopod by macroalgal defenses (e.g. acrylic acid) larvae are not common members of the (VanAlstyne et al. 2001) unlike many grazers plankton, with parasitic larvae most likely to (e.g. Strongylocentrotus species). be observed. Occasionally, suspended Predators: Isopods play a significant role as benthic juveniles or pelagic species are intermediate food web links, like amphipods, collected in plankton samples, but these can (e.g. see Americorophium salmonis, this be differentiated from larvae by their larger guide) that are consumed by more than 20 size (Sadro 2001). species of marine fish (Welton and Miller Juvenile: Juveniles possess most adult 1980; cabezon, Best and Stachowicz 2012) characteristics, but antennal flagellae are and whales (Brusca et al. 2007). shorter than in adults (Fig. 3). This specimen Behavior: Swimming is accomplished by was found in a female brood pouch. Juvenile propulsion from the first three pairs of development in isopods follows the third pleopods. In Idotea resecata and I. manca stage, where males have gonopods wosnesenskii, the power strokes from each (modified first pleopods) and females have pleopod occur in succession, but the recovery plate-like limbs on pereopods 2–5, called strokes occur simultaneously (Alexander oostegites (that, together with the sternites, 1988). form the marsupium) (Boyko and Wolff 2014). Females brood beginning when body length is Bibliography 13 mm (Wallerstein and Brusca 1982). Longevity: 1. ALEXANDER, D. E. 1988. Kinematics Growth Rate: Growth among isopods occurs of swimming in two species of Idotea in conjunction with molting where the (Isopoda, Valvifera). Journal of exoskeleton is shed and replaced. Post-molt Experimental Biology. 138:37-49. individuals will have soft shells as the cuticle 2. —. 1991. Mechanics of branchial gradually hardens. During a molt, arthropods ventilation in the valviferan isopod have the ability to regenerate limbs that were Idotea wosnesenskii (Crustacea). previously autonomized (Kuris et al. 2007), Journal of Zoology. 224:607-616. however, isopods do not autotomize limbs as 3. ALEXANDER, D. E., J. BLODIG, and readily as other groups (Brusca and Iverson S. Y. HSIEH. 1995. Relationship 1985). Compared to other arthropods, between function and mechanical isopods exhibit a unique biphasic molting, in properties of the pleopods of isopod which the posterior 1/2 of the body molts crustaceans. Invertebrate Biology. before the anterior 1/2 (Brusca et al. 2007). 114:169-179. Food: Idotea wosnesenskii is primarily an 4. ARAUJO, P. B., A. F. QUADROS, M. herbivore, eating kelp and eelgrass blades M. AUGUSTO, and G. BOND- (Welton and Miller 1980). However, I. BUCKUP. 2004. Postmarsupial wosnesenskii individuals are also known to development of Atlantoscia floridana chew through and ingests egg capsules of the (van Name, 1940) (Crustacea, gastropod, Nucella emarginata (Rawlings Isopoda, Oniscidea): sexual 1990). Idotea species produce a phenolic differentiation and size at onset of compounds that reduces feeding on eelgrass sexual maturity. Invertebrate (Zostera species) by other grazers (e.g. Ampithoe valida, this guide) (Lewis and Boyer

Hiebert, T.C. 2015. Idotea wosnesenskii. In: Oregon Estuarine Invertebrates: Rudys' Illustrated Guide to Common Species, 3rd ed. T.C. Hiebert, B.A. Butler and A.L. Shanks (eds.). University of Oregon Libraries and Oregon Institute of Marine Biology, Charleston, OR. Reproduction and Development. polymorphism of the isopod Idotea 45:221-230. baltica (Pallas). Biological Journal of 5. BEST, R. J., and J. J. STACHOWICZ. the Linnean Society. 55:45-68. 2012. Trophic cascades in seagrass 15. JORMALAINEN, V., and J. TUOMI. meadows depend on mesograzer 1989. Reproductive ecology of the variation in feeding rates, predation isopod Idotea baltica (Pallas) in the susceptibility, and abundance. Marine northern Baltic. Ophelia. 30:213-223. Ecology Progress Series. 456:29-42. 16. KOZLOFF, E. N. 1974. Seashore life 6. BOYKO, C. B., and C. WOLFF. 2014. of Puget Sound, the Strait of Georgia, Isopoda and Tanaidacea, p. 210-215. and the San Juan Archipelago and In: Atlas of crustacean larvae. J. W. adjacent Regions. University of Margtin, J. Olesen, and J. T. Høeg Washington Press, Seattle and (eds.). Johns Hopkins University London. Press, Baltimore. 17. KROER, N. 1989. Life cycle 7. BRUSCA, G. J. 1966. Studies on the characteristics and reproductive salinity and humidity tolerances of five patterns of Idotea spp. (Isopoda) in the species of isopods in a transition from Limfjord, Denmark. Ophelia. 30:63-74. marine to terrestrial life. Bulletin of the 18. KURIS, A. M., P. S. SADEGHIAN, J. Southern California Academy of T. CARLTON, and E. CAMPOS. 2007. Science. 65:147-154. Decapoda, p. 632-656. In: The Light 8. BRUSCA, R. C., C. R. COELHO, and and Smith manual: intertidal S. TAITI. 2007. Isopoda, p. 503-541. invertebrates from central California to In: The Light and Smith manual: Oregon. J. T. Carlton (ed.). University intertidal invertebrates from central of California Press, Berkeley, CA. California to Oregon. J. T. Carlton 19. KUSSAKIN, O. G. 1994. The common (ed.). University of California Press, north-east idoteid Idotea Berkeley, CA. wosnesenskii, a recent invader to the 9. BRUSCA, R. C., and E. W. IVERSON. Commander Islands. Biologiya Morya. 1985. A guide to the marine isopod 20:97-99. crustacea of Pacific Costa Rica. 20. LEWIS, J. T., and K. E. BOYER. 2014. Revista de Biologia Tropical. 33:1-77. Grazer functional roles, induced 10. FEE, A. R. 1927. The Isopoda of defenses, and indirect interactions: Departure Bay and vicinity with implications for eelgrass restoration in descriptions of new species, variations San Francisco Bay. Diversity. 6:751- and colour notes. Contributions to 770. Canadian Biology and Fisheries. 3:15- 21. MENZIES, R. J. 1950. The taxonomy, 47. ecology, and distribution of northern 11. GAINES, S. D. 1985. Herbivory and California isopods of the genus between-habitat diversity: the Idothea with the description of a new differential effectiveness of defenses species. Wasmann Journal of Biology. in a marine plant. Ecology. 66:473- 8:155-195. 485. 22. MILLER, M. A. 1968. Isopoda and 12. HATCH, M. H. 1947. The Chelifera Tanaidacea from buoys in coastal and isopoda of Washington and waters of the continental United adjacent regions. University of States, Hawaii, and the Bahamas Washington Publications in Biology. (Crustacea). Proceedings of the 10:155-274. United States National Museum. 13. HOLLIDAY, C. W. 1988. Branchial 125:1-53. Na+/K+-atpase and osmoregulation in 23. —. 1975. Phylum Arthropoda: the isopod, Idotea wosnesenskii. Crustacea, Tanaidacea and Isopoda, Journal of Experimental Biology. p. 277-312. In: Light's manual: 136:259-272. intertidal invertebrates of the central 14. JORMALAINEN, V., S. MERILAITA, California coast. S. F. Light, R. I. and J. TUOMI. 1995. Differential Smith, and J. T. Carlton (eds.). predation on sexes affects color

University of California Press, 31. SADRO, S. 2001. Arthropoda: Berkeley. Decapoda, p. 176-178. In: 24. MILLER, M. A., and W. L. LEE. 1970. Identification guide to larval marine A new idoteid isopod Idotea invertebrates of the Pacific Northwest. (Pentidotea) kirchanskii from central A. Shanks (ed.). Oregon State California (Crustacea). Proceedings of University Press, Corvallis, OR. the Biological Society of Washington. 32. SCHULTZ, G. A. 1969. How to know 82:790-798. the marine isopod crustaceans. Brown 25. POORE, G. C. B., and H. M. L. TON. Company, Dubuque, Iowa. 1993. Idoteidae of Australia and New 33. TROWBRIDGE, C. D. 1993. Feeding Zealand (Crustacea: Isopoda: ecology of the ascoglossan Valvifera). Invertebrate Taxonomy. opisthobranch Aplysiopsis 7:197-278. enteromorphae (Cockerell and Eliot): 26. RAFI, F., and D. R. LAUBITZ. 1990. patterns of distribution and impact on The Idoteidae (Crustacea, Isopoda, tidepool-dwelling green algae. Journal Valvifera) of the shallow waters of the of Experimental Marine Biology and northeastern north Pacific Ocean. Ecology. 169:233-257. Canadian Journal of Zoology. 34. VAN ALSTYNE, K. L., G. V. WOLFE, 68:2649-2687. T. L. FREIDENBURG, A. NEILL, and 27. RAWLINGS, T. A. 1990. Associations C. HICKEN. 2001. Activated defense between egg capsule morphology and systems in marine macroalgae: predation among populations of the evidence for an ecological role for marine gastropod, Nucella DMSP cleavage. Marine Ecology emarginata. Biological Bulletin. Progress Series. 213:53-65. 179:312-325. 35. WALLERSTEIN, B. R., and R. C. 28. RICHARDSON, H. 1905. Monograph BRUSCA. 1982. Fish predation: a on the isopods of North America. preliminary study of its role in the Bulletin of the United States Natural zoogeography and evolution of Museum. 54:1-727. shallow water idoteid isopods 29. RICKETTS, E. F., and J. CALVIN. (Crustacea: Isopoda: Idoteidae). 1952. Between Pacific tides: an Journal of Biogeography. 9:135-150. account of the habits and habitats of 36. WELTON, L. L., and M. A. MILLER. some five hundred of the common, 1980. Isopoda and Tanaidacea: the conspicuous seashore invertebrates of isopods and allies, p. 536-558. In: the Pacific Coast between Sitka, Intertidal invertebrates of California. R. Alaska, and Northern Mexico. H. Morris, D. P. Abbott, and E. C. Stanford: Stanford University Press, Haderlie (eds.). Stanford University Stanford. Press, California. 30. RUESINK, J. L. 2000. Intertidal mesograzers in field microcosms: linking laboratory feeding rates to community dynamics. Journal of Experimental Marine Biology and Ecology. 248:163-176.