Detonella Papillicornis Class: Malacostraca Order: Isopoda, Oniscidea a Sow Bug Family: Detonidae

Phylum: Arthropoda, Crustacea Detonella papillicornis Class: Malacostraca Order: Isopoda, Oniscidea A sow bug Family: Detonidae

Taxonomy: Detonella papillicornis was Rostrum: Absent (Fig. 2). originally described by Richardson in 1904 as Eyes: Eyes with approximately eight Trichoniscus papillicornis. Richardson (sometimes six) ocelli (Lohmander 1927). described “about seven” articles on the Antenna 1: First antenna is vestigial flagellum of antenna two, but Lohmander later among the suborder Oniscoidea. found 4–5 articles (including observations of Antenna 2: Peduncle of second the type specimen) and moved this species to antenna with 5–6 joints and the last three a new genus, Detonella (Schultz 1972; bear setose tubercules. The fifth joint has a Garthwaite 1988). Interspecific variation in distal process (Fig. 3) and the flagellum is characters (e.g. protopodite setae and composed of four articles (Richardson 1905; pleotelson margin, Schmidt 2000) lead Schultz 1972). subsequent taxonomists to name new Mouthparts: species, which were eventually synonymized Pereon: Body elongate and depressed with as D. papillicornis (for full list of synonyms see thorax composed of seven segments, the first Schmidt 2000). of which is not fused with the head (Brusca et al. 2007). Description Pereonites: Thoracic segments Size: Individuals 3.8 mm (Friday Harbor, about equal in size, each with two rows of Washington, Hatch 1947) to 6 mm in length tubercules and postero-lateral angles directed (South Slough of Coos Bay). backwards (Lohmander 1927). Color: Body dark red and white mottled Pereopods: Seven pairs of (Miller 1975). pereopods. General Morphology: Isopod bodies are Pleon: Pleon narrower than pereon, but not dorso-ventrally flattened and can be divided abruptly so (Fig. 1). into a compact cephalon, with eyes, two Pleonites: Five free pleonites are antennae and mouthparts, and a pereon present (Brusca et al. 2007) (Fig. 1). (thorax) with eight segments, each bearing Pleopods: similar pereopods (hence the name “iso- Uropods: Styliform and extend beyond body pod”). Posterior to the pereon is the pleon, or with outer branch stouter and longer than the abdomen, with six segments, the last of which inner branch. Uropods are inserted postero- is fused with the telson (the pleotelson) (see laterally, and the base is not expanded (Fig. Plate 231, Brusca et al. 2007). The Isopoda 4). can be divided into two groups: ancestral Pleotelson: Spatulate (Fig. 4) and (“short-tailed”) groups (i.e. suborders) that morphologically variable. The pleotelson of have short telsons and derived (“long-tailed”) the present specimen is more triangular in groups with long telsons, D. papillicornis original description (Richardson 1905). groups among the former (see Fig. 9, Sexual Dimorphism: The first and second Garthwaite and Lawson 1992; Brandt and pleopods are also elongated in males for Poore 2003; see Plate 249C, Brusca et al. copulation in oniscideans and reproductive 2007). The suborder, Oniscidea is the largest females have a conspicuous marsupium. isopod suborder and the only fully-terrestrial crustacean group (Brusca et al. 2007). Possible Misidentifications Cephalon: Cephalon without rostrum, but The order Isopoda contains 10,000 species, slightly pronounced anteriorly and with 1/2 of which are marine and comprise 10 concavity at apex (Fig. 2). Large anterior suborders, with eight present from central lobes at antero-lateral angles. California to Oregon (see Brusca et al. 2007).

A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12704 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected]

Among isopods with small, short telsons, Ecological Information there are several groups (i.e. suborders) Range: Type region is Alaska (Trichoniscus including Phreatoicidea, Asellota, papillicornis, USNM# 28772, Garthwaite and Microcerberidea, Calabozoidea and Lawson 1992). Essentially an Arctic and Oniscidea. Antarctic species (Lohmander 1927) with The monophyletic Oniscidea known range from Southern Alaska, to (previously part of the paraphyletic Washington and, recently, in San Francisco Scyphacidae, see Holdrich et al. 1984 in Bay area (Garthwaite and Lawson 1992). Schmidt 2000, 2002) is a fully-terrestrial Local Distribution: Coos Bay distribution at group composed of 4,000 described species, Day's Creek in the South Slough. with 22 known locally (among 10 families, Habitat: Preferable substrates include sand Schmidt 2002; Brusca et al. 2007). and beach debris. Members are characterized by seven Salinity: pereonites, the first not fused with the head, Temperature: seven pairs of pereopods, male penes on the Tidal Level: Upper intertidal of beaches. sternum of pereonite seven, a pleotelson that Associates: The amphipod, Orchestra and does not curve dorsally, vestigal (or very other Oniscoidea, including Armadilioniscus small) antennules and a pleon with five free tuberculatus and Philoscia richardsona (Hatch pleonites (Brusca et al. 2007). The first and 1947). second pleopods are also elongated in Abundance: Somewhat sparse locally, but males for copulation, many species have a rather common in littoral sites throughout San water conducting system and some have Francisco Bay, California (Garthwaite and respiratory structures on pleopods called Lawson 1992). pseudotracheae. The Detonidae have antennae Life-History Information flagella with four articles and the family Reproduction: Most isopods have separate comprises four species locally, three of sexes (i.e. dioecious, Brusca and Iverson which are in the genus Armadilloniscus; 1985) (although protogynous and protandric Detonella is monotypic locally (D. species are known, Araujo et al. 2004; Boyko papillicornis is the only species). and Wolff 2014). Reproduction proceeds by Armadilloniscus species have a definite copulation and internal fertilization where rostrum and an oval body with no narrowing eggs are deposited within a few hours after of the pleon. Their uropods have expanded copulation and brooded within the female bases and all four branches (which are marsupium (Brusca and Iverson 1985). The small) are near the center line. The exopods biphasic molting of isopods allows for are inserted on the medial margin in copulation; the posterior portion of the body Armadilloniscus and are terminal in molts and individuals mate, then the anterior Detonella and conspicuously extend from portion, which holds the brood pouch, molts body outline (Brusca et al. 2007). (Sadro 2001). Embryonic development Armadilloniscus lindahli has a convex body proceeds within the brood chamber and is and can roll into a ball. Armadilloniscus direct with individuals hatching as manca coronacapitalis has a spur-like extension on larvae that resemble small adults, with no the lateral margin of the antenna penduncle larval stage (Boyko and Wolff 2014). article while A. holmesi does not. Both A. Larva: Since most isopods are direct lindahli and A. coronacapitalis have a developing, they lack a definite larval stage. southern distribution from Marin County, Instead this young developmental stage California south, while D. papillicornis occurs resembles small adults (e.g. Fig. 40.1, Boyko from San Francisco Bay, California and Wolff 2014). Most isopods develop from northward (Brusca et al. 2007). embryo to a manca larva, consisting of three Armadilloniscus holmesi occurs from Friday stages. Manca larvae are recognizable by Harbor, Washington to Bahia Megdalena, lacking the seventh pair of pereopods, but Baja California (Schultz 1972). otherwise resemble small adults. They usually hatch from the female marsupium at the second stage and the molt from second to

Hiebert, T.C. 2015. Detonella papillicornis. 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. third manca produces the seventh pair of BEST, R. J., and J. J. STACHOWICZ. 2012. pereopods and sexual characteristics (Boyko Trophic cascades in seagrass and Wolff 2014). Isopod development and meadows depend on mesograzer larval morphology can vary between groups variation in feeding rates, predation (e.g. Gnathiidae, Cryptoniscoidea, susceptibility, and abundance. Marine Bopyroidae, Cymothoidae) (see Boyko and Ecology Progress Series. 456:29-42. Wolff 2014) and some oniscid isopod species BOYKO, C. B., and C. WOLFF. 2014. are known to care for their young after Isopoda and Tanaidacea, p. 210-215. hatching (Boyko and Wolff 2014). Parasitic In: Atlas of Crustacean Larvae. J. W. isopods, for example, have larvae that are Margtin, J. Olesen, and J. T. Høeg morphologically dissimilar from adults (Sadro (eds.). Johns Hopkins University 2001). Isopod larvae are not common Press, Baltimore. members of the plankton, with parasitic larvae BRANDT, A., and G. C. B. POORE. 2003. most likely to be observed. Occasionally, Higher classification of the flabelliferan suspended benthic juveniles or pelagic and related isopoda based on a species are collected in plankton samples, but reappraisal of relationships. these can be differentiated from larvae by Invertebrate Systematics. 17:893-923. their larger size (Sadro 2001). BRUSCA, R. C., C. R. COELHO, and S. Juvenile: TAITI. 2007. Isopoda, p. 503-541. In: Longevity: The Light and Smith manual: intertidal Growth Rate: Growth among isopods occurs invertebrates from central California to in conjunction with molting where the Oregon. J. T. Carlton (ed.). University exoskeleton is shed and replaced. Post-molt of California Press, Berkeley, CA. individuals will have soft shells as the cuticle BRUSCA, R. C., and E. W. IVERSON. 1985. gradually hardens. During a molt, arthropods A guide to the marine isopod have the ability to regenerate limbs that were crustacea of Pacific Costa Rica. previously autonomized (Kuris et al. 2007), Revista de Biologia Tropical. 33:1-77. however, isopods do not autotomize limbs as GARTHWAITE, R. L. 1988. Detonella readily as other groups (Brusca and Iverson papillicornis (Richardson) (Isopoda: 1985). Compared to other arthropods, Oniscidea: Scyphacidae) from Bolinas isopods exhibit a unique biphasic molting, in Lagoon, California. Bulletin Southern which the posterior 1/2 of the body molts California Academy of Sciences. before the anterior 1/2 (Brusca et al. 2007). 87:46-47. Food: GARTHWAITE, R. L., and R. LAWSON. Predators: Isopods play a significant role as 1992. Oniscidea isopoda of the San intermediate food web links, like amphipods, Francisco Bay area. Proceedings of (e.g. see Americorophium salmonis, this the California Academy of Sciences. guide) that are consumed by more than 20 47:303-328. species of marine fish (Welton and Miller HATCH, M. H. 1947. The Chelifera and 1980; cabezon, Best and Stachowicz 2012) isopoda of Washington and adjacent and whales (Brusca et al. 2007). regions. University of Washington Behavior: Publications in Biology. 10:155-274. KURIS, A. M., P. S. SADEGHIAN, J. T. Bibliography CARLTON, and E. CAMPOS. 2007. ARAUJO, P. B., A. F. QUADROS, M. M. Decapoda, p. 632-656. In: The Light AUGUSTO, and G. BOND-BUCKUP. and Smith manual: intertidal 2004. Postmarsupial development of invertebrates from central California to Atlantoscia floridana (van Name, Oregon. J. T. Carlton (ed.). University 1940) (Crustacea, Isopoda, of California Press, Berkeley, CA. Oniscidea): sexual differentiation and LOHMANDER, H. 1927. On some terrestrial size at onset of sexual maturity. isopods in the United States National Invertebrate Reproduction and Museum. Proceedings of the United Development. 45:221-230. States Natural Museum. 72:1-18.

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