Phylum: Arthropoda, Crustacea Limnoria tripunctata Class: Multicrustacea, Malacostraca, Eumalacostraca Order: Peracarida, Isopoda, Limnoriidea A gribble Family: Limnorioidea, Limnoriidae Taxonomy: Limnoria was described in 1813 ball and are easily recognizable by their small by Leach and has been placed in a variety size and wood-boring habits (Brusca 1980). of isopod families since (e.g. Asellidae), until Cephalon: Smooth, rounded and modified for Harger erected the family Limnoriidae for it, boring (Fig. 1). in 1880 (Menzies 1957). It was divided into Eyes: Lateral and anterior (Fig. 1). two subgenera on the basis of boring sub- Antenna 1: First antenna flagellum strate and associated mouthparts (Cookson with four articles and peduncle with three (Fig. 1991). Limnoria Limnoria were the wood- 3). Both antennae are reduced, separated at borers while Limnoria Phycolimnoria were midline, and positioned in a nearly transverse the algae-borers (Menzies 1957; Brusca line (Fig. 1). 1980). Thus, Limnoria Limnoria tripunctata Antenna 2: Second antenna flagellum is sometimes seen, although these subge- with five articles (Fig. 4). neric names are rarely used today (Cookson Mouthparts: Mandibles with file-like 1991; Brusca et al. 2007). ridges (right) and rasping surface (left), but lack lacina mobilis and molar processes Description (Brusca 1980). Size: Limnoriids are small and L. tripunctata Rostrum: is no exception, reaching maximum lengths Pereon: of 2.5 mm. Pereonites: Seven total segments, the Color: Light tan, whitish and often encrusted first of which is widest (Figs. 1, 2) and coxal with debris. plates are present on pereonites 2–7 (Brusca General Morphology: Isopod bodies are 1980). dorso-ventrally flattened and can be divided Pereopods: In mature females, leaf- into a compact cephalon, with eyes, two an- like ooestegites are present at the base of tennae and mouthparts, and a pereon each of first four pairs of legs and forms a (thorax) with eight segments, each bearing brood pouch or marsupium (see Fig. 6, similar pereopods (hence the name “iso- Corophiurn spinicorne, this guide). pod”). Posterior to the pereon is the pleon, Pleon: or abdomen, with six segments, the last of Pleonites: Five free pleonites with fifth which is fused with the telson (the pleo- somite bearing three tubercles (Fig. 1). telson) (see Plate 231, Brusca et al. 2007). Pleopods: The Isopoda can be divided into two groups: Uropods: Uropod branches dissimilar, with ancestral (“short-tailed”) groups (i.e. subor- short and claw-like exopod and long, apically ders) that have short telsons and derived blunt endopod (Fig. 6). (“long-tailed”) groups with long telsons. Pleotelson: Ornamented pleotelson with Members of the Flabellifera, to which L. three anterior tubercles (“tri-punctata", Fig. 1) tripunctata belongs, fall into the long-tailed and tuberculate posterior and lateral borders variety (see Fig. 86, Kozloff 1993). Limnoria (Fig. 5). tripunctata individuals are able to roll into a A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] Hiebert, T.C. 2015. Limnoria tripunctata. 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. Sexual Dimorphism: Mature females are Ecological Information conspicuous with a marsupium (see pereo- Range: Type locality is San Diego, California. pods) and males with modified posterior Known range from Atlantic and Pacific coasts end of the seventh pereonite (see Fig. 1, in temperate and tropical waters and capable Menzies 1972). of interbreeding over large geographic dis- Possible Misidentifications tances (Menzies 1972) within a temperature The order Isopoda contains 10,000 range of 15–30˚C (44˚ to 12° N) (Beckman Limnoria tripunctata species, 1/2 of which are marine and com- and Menzies 1960). is a prise 10 suborders, with eight present from well-established species in European coastal central California to Oregon (see Brusca et waters (Borges et al. 2014). Local Distribution: Oregon distribution in up- al. 2007). Among isopods with elongated telsons (with anuses and uropods that are per bays including Coos, Yaquina, Tillamook subterminal), there are several groups (i.e. estuaries. suborders) including the Valvifera, Anthu- Habitat: Docks and pilings, chiefly in bays ridea, Gnathiidea, Epicaridea and Flabellif- and estuaries, where it burrows into wood, era. whether it is floating or submerged (Johnson The Flabellifera is a large assem- and Menzies 1956). The wood serves as Limnoria tripunctata blage and contains 3,000 species with sev- both food and protection. en families occurring locally, threeof which is even undeterred by creosote preserved wood (Menzies 1951; Ricketts and Calvin are not present north of Point Conception, California (Brusca et al. 2007). Limnoriids 1952; Borges et al. 2014) (see also Food). are wood-boring species that are charac- Within the wood, burrows are equal in diame- terized by reduced uropods, small exo- ter throughout and have smooth walls (Sleeter pods, and a body that is less that 4 mm in and Coull 1973). Bite marks left on wood by Limnoria length (see Brusca et al. 2007 for other species are distinct and measure 50 distinguishing characters). This family –80 µm in diameter and tunnels reach depths comprises only four local species (70 de- of 2 cm (Pitman et al. 1997). They can com- scribed worldwide) and all are in the genus pletely bury themselves within wood in 4–6 days, but remain close to the wood surface Limnoria. Limnoria algarum, bores in algal (Ricketts and Calvin 1952). holdfasts, not wood, and is the only spe- Salinity: A stenohaline species (Borges et al. cies with a simple incisor mandibular pro- 2014) that tolerates salinity and oxygen fluc- cess, lacking a file that is present in the tuations as individuals occur in warm, often other three, wood-boring, species. Limno- salty upper bays. The ideal salinity range is ria lignorum has a pleotelson with dorsal 30–34 (in the lab, Borges et al. 2009), but in- surface that forms a Y-shaped keel at the dividuals tolerate salinities from 12 to 48 Limnoria base while L. quadripuntcata and L. (Menzies 1972). Other species (e.g. L. lignorum tripunctata have pleotelsons with symmet- ) can't tolerate low salinity (15) or rically arranged anterior tubercles. The dissolved oxygen content below 1.6 ppm. Limnoria tripunctata two latter species can be differentiated (as can stand periodic oxy- their names suggest) by the number of tu- gen depletion, however, (Menzies 1957) and bercles present, four in L. quadripuntcata has been observed at salinities of 12 near and three in L. tripunctata (Brusca et al. San Francisco, California, and can survive at L. 2007). salinities between 10–18. However, even tripunctata cannot survive exposure to fresh- A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: https://oimb.uoregon.edu/oregon-estuarine-invertebrates and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] water for greater than one day (Menzies sexes (i.e. dioecious, Brusca and Iverson 1957). 1985) (although protogynous and protandric Temperature: Temperature range from 15° species are known, Araujo et al. 2004; Boyko to 30°C (Beckman and Menzies 1960; and Wolff 2014). Reproduction proceeds by Menzies 1972; Borges et al. 2009). Highest copulation and internal fertilization where reproductive rates were observed between eggs are deposited within a few hours after 20–25˚C, reproduction is impaired below 10° copulation and brooded within the female C and egg production takes twice as long at marsupium (Brusca and Iverson 1985). The 15˚C than at 20˚C (Menzies 1957, 1972). biphasic molting of isopods allows for copula- Tidal Level: A shallow water species, L. tion; the posterior portion of the body molts tripunctata occurs from the water surface to and individuals mate, then the anterior por- 18 meters deep. Individuals prefer lower tion, which holds the brood pouch, molts depths when surface salinity is low or tidal (Sadro 2001). Embryonic development pro- fluctuation is great. Individuals tend to pre- ceeds within the brood chamber and is direct fer estuary benthos, and commonly occur at with individuals hatching as manca larvae that the bases of pilings. resemble small adults, with no larval stage Associates: Limnoria burrows can be in- (Boyko and Wolff 2014). Limnoria species habited by the commensal isopod, Caecijae- exhibit low fecundity, iteroparity and direct de- ra; the sphaeromatid isopod, Gnori- velopment (Menzies 1972) and females in the mosphaeroma; the amphipod, Chelura; and genus only carry an average of about 9–10 the copepod Donsiella (Menzies 1957), eggs and breeding occurs year-round none of which are borers. The boring (Ricketts and Calvin 1952). Adult L. tripunc- mollusk, Teredo, can also co-occur in wood tata occur and copulate as pairs within tun- where Limnoria burrows. After 4–6 months nels (see Fig. 2, Menzies 1972) and eggs re- submerged (suspended 1–4 meters above quire 2–4 weeks for development (Borges et the bottom), untreated wood with L. al. 2014). Females can produce up to three tripunctata developed a community broods per year, and the number of gravid fe- consisting of turbellarians, nematodes, the males in a single population is highest when archiannelid Dinophilus; the polychaete water temperatures are between 17 and 19˚C Polydora; the tanaid, Leptochelia savignyi; (Johnson and Menzies 1956). Locally, peak copepods and amphipods (Sleeter and Coull breeding time for L. tripunctata is from April to 1973). The heterotrich ciliate Microfolliculina May (Friday Harbor, WA, Welton and Miller limnoriae, attaches to the dorsal surface of 1980) and the average number of eggs per the pleotelson (up to four individuals per sin- female is 22 (Welton and Miller 1980).