Phylum: Arthropoda, Crustacea Grandidierella japonica Subphylum: Malacostraca Order: Amphipoda, Gammaridea A brackish water amphipod Family: Aoridae Description Size: Males up to 22 mm in length, females flagellum is equal to peduncle and consists of 13 mm long (San Francisco Bay, Chapman 18 articles (Stephensen 1938). Male antenna and Dorman 1975; Myers 1981). The one longer than its antenna two (Barnard illustrated specimen (a male, from Coos Bay) 1973), however female antennae are of equal is 10 mm in length (Fig. 1). size (Stephensen 1938) (female not figured). Color: Black head, mottled grey to grey Antenna 2: Length from ¾ of to brown body (Chapman and Dorman 1975) longer than antenna one (Chapman and with distal parts of limbs white (Stephensen Dorman 1975) (see antenna 1). Spines 1938; Chapman 2007). This specimen white present on peduncle articles 3–5. Male (preserved in ETOH). second antenna stout and flagellum with General Morphology: The body of seven articles (Stephensen 1938). Female amphipod crustaceans can be divided into second antenna length in equal to antenna three major regions. The cephalon (head) or one and fifth article of peduncle with four cephalothorax includes antennules, antennae, strong spines. Female flagellum with six mandibles, maxillae and maxillipeds articles (not figured). (collectively the mouthparts). Posterior to Mouthparts: Mandible with large the cephalon is the pereon (thorax) with molar, toothed lacinia mobilis, incisors and seven pairs of pereopods attached to long 2-articled mandibular palp with third pereonites followed by the pleon (abdomen) article setose. Maxilliped with 4-articled palp, with six pairs of pleopods. The first three sets article four claw-like and article two twice the of pleopods are generally used for swimming, length of one and two (Chapman and Dorman while the last three are simpler and surround 1975). Outer maxilliped plates twice the the telson at the animal posterior. The length of inner plates. gammarid family Aoridae is characterized by separate urosome articles and a biramous Pereon: third uropod. They also have a short Coxae: Reduced (Chapman and (sometimes absent) rostrum, a long first Dorman 1975), serially arranged and barely antenna and a fleshy telson. Grandidierella contiguous (Barnard 1973) (Fig. 1). Coxal japonica (see plate 262A, Chapman 2007), plate one with a medial-ventral tooth however, resembles the family Corophiidae (Chapman and Dorman 1975) (just slightly more closely due to the uniramus uropod produced in illustrated specimen). three (Chapman 2007). Gnathopod 1: Male gnathopod one is Cephalon: greatly enlarged, “carpochelate” (i.e. not Rostrum: filtering type) (Grandidierella, Barnard 1973; Eyes: A single, oval-shaped, lateral Chapman 2007). Articles two and five greatly eye (Kozloff 1974) that are black and medium enlarged and subequal (Chapman and in size (Stephensen 1938) (Fig. 1). Dorman 1975). Article two oval, article three Antenna 1: The first antenna in small, article four small and elongate. Article males is more than ½ body length (Chapman five with sides parallel and with one enlarged and Dorman 1975) and is much shorter in tooth forming thumb and two smaller teeth females. The peduncle is with short (Grandidierella, Barnard 1975). Anterior edge accessory flagellum in both sexes (Fig. 1b). of article five with 18–20 transverse fine The male flagellum has 20 articles and is a ridges ("stridulating organs’’, Stephensen little longer than peduncle. The female 1938) and four spines (Figs. 1, 1a). Female Hiebert, T.C. 2015. Grandidierella japonica. 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. A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species: http://hdl.handle.net/1794/12709 and full 3rd edition: http://hdl.handle.net/1794/18839 Email corrections to: [email protected] gnathopod one is small, but larger than rostrum, long first antenna, gnathopod one gnathopod two. Article two is setose and larger than two (in males), a fleshy telson, a narrow (Stephensen 1938) (Fig. 5). long seventh pereopod (longer than the sixth), Gnathopod 2: Male gnathopod two is distinctly separate urosome articles and a simple and much smaller than gnathopod biramous uropod three. There are four aorid one. Article two is twice the length of article amphipod species that are not native to the five. Article three is short and dactyl is not northeastern Pacific coast (e.g. Aoroides chelate (Fig. 1). Female gnathopod two is secundus, Microdeutopus gryllotapla), one of setose, is smaller than gnathopod one and which is G. japonica. At least two aorid with article two about 2/3 length of male genera that are quite similar to Grandidierella: article two (Barnard 1973). Paraoroides, and Aoroides (family Aoridae). Pereopods 3 through 7: Simple, not Paraoroides species have a uniramous third prehensile (Barnard 1973) and increasing in uropod (as in G. Japonica), but this ramus is length. A character of the Aoridae is a only as long as the peduncle, not twice or seventh pereopod that is longer than the sixth three times as long (Barnard 1973). In (see plate 269C, Chapman 2007) and the Paraoroides, the first gnathopod is not seventh pereopod in G. japonica is very long carpochelate, but only slightly enlarged, the (Fig. 1). Female pereopods are with narrow gnathopods are equal in size. The third second articles (Stephensen 1938). article of the first antenna is not elongate, as it Pleon: is in G. japonica. Aoroides species (six local) Pleonites: Third pleonite is without have an immensely merochelate male first dorsal tooth (Barnard 1975) gnathopod (Barnard 1975), quite different Urosomites: All three urosomites from that of G. japonica. Article four is short (Fig. 1). The first uropod is biramous elongate, article five is oval, but lacks teeth. and longer than the second or third. The The gnathopod is the filtering type, with long peduncle is with peduncular process and two setae. The third uropods in this genus are anterolateral spines on urosomite (Barnard biramous, not uniramous as in Grandidierella. 1969) (Fig. 3). Second uropod is also Aoroides columbiae is a Pacific coast species. biramous (Grandidierella, Barnard 1975) and Other species of Grandidierella have not been with thin peduncle and long rami (Barnard recorded from our area, include a tropical 1975) (Fig. 4). The third uropod is uniramous, species, G. nottoni, and four freshwater without hooked apical spine or long setae species. Grandidierella japonica closely (Barnard 1975) (a defining character of G. resembles amphipods in the gamily japonica). It is not fleshy, blunt or elongate Corophiidae (Chapman 2007) and the ramus is three times as long as the The gammarid family Corophiidae is peduncle (Barnard 1973) (Fig. 6). characterized by individuals that build U- Epimera: shaped tubes in both soft sediments and on Telson: Telson uncleft and somewhat hard surfaces, sometimes forming dense swollen (Kozloff 1974), with button-like aggregations. Species can be dramatically morphology and medial groove (Chapman sexually dimorphic and, while males may be and Dorman 1975) (Figs. 1, 2). easier to identify with taxonomically relevant Sexual Dimorphism: Male first gnathopod characters including the rostrum and article two is expanded and article five is peduncle of second antennae, most females large, with parallel sides, teeth and can be reliably identified to species as well stridulating organ. All features are lacking in (Chapman 2007). Five corophiid genera females. Male antenna one is also longer occur locally, Americorophium, Corophium, than two and female antennae are equal. Crassicorophium, Laticorophium and Monocorophium. The three common Possible Misidentifications estuarine species in this guide (A. brevis, A. The Aoridae are a family of gammarid salmonis, A. spinicorne) were previously amphipods that are tube-building suspension members of the genus Corophium (see feeders found in marine and estuarine Shoemaker 1949), but were transferred to the habitats. They are characterized by a short Hiebert, T.C. 2015. Grandidierella japonica. 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. genus Americorophium in 1997 (Bousfield japonica). Photis species have elongate and Hoover 1997). coxae and a normal first gnathopod, but an Other common gammarid families enlarged second gnathopod that is often include the Ampithoidae, Cheluridae, highly sculptured. The third uropod has an Ischyroceridae, Podoceridae, and lsaeidae elongate peduncle. (for key see Chapman 2007). The Ampithoidae have a poorly recessed head Ecological Information (Barnard 1973) and a short third article on the Range: Grandidierella japonica is native to peduncle of antenna one. At least one ramus Abasiri River, Hokkaido, Japan, from which it of the third uropod in this family is very setose was introduced to U.S. Pacific harbors with terminally and the third uropod also has Crassostrea (commercial oyster), Tomales, curved hooks on the end of its stout ramus Bolinas, and San Francisco, California, (Barnard 1975). The Ampithoidae have a possibly as early as 1928 (Chapman and thick, uncleft telson. In our area there are Dorman