﻿Two new species of the family Aoridae (Crustacea, Malacostraca, Amphipoda) from Korean waters

﻿Abstract Two new species of the family Aoridae, one from the genus Aoroides Walker, 1898, and other from the genus Grandidierella Coutière, 1904, are reported from Korean waters. Aoroidesgracilicrussp. nov. is similar to A.longimerus in having numerous plumose setae on the basis and carpus of gnathopod 1. However, the new species can be distinguished from A.longimerus by the numerous plumose setae on the bases of pereopods 3 and 4 and the slender basis of pereopod 7. Grandidierellanaroensissp. nov. is morphologically most similar to G.pseudosakaensis. However, the new species can be distinguished by the presence of small distal and proximal processes and a large middle process on the carpus of gnathopod 1, and the subovate propodus of gnathopod 1. Both new species are illustrated and compared to related species. A key to species in the family Aoridae from Korean waters is also provided.


Introduction
The family Aoridae Stebbing, 1899 includes amphipod species that are abundant in coastal and sublittoral waters.Aorid amphipods usually feed on generalized organic detritus and algal debris, but some aorids can be opportunistic predators.Microdeutopus gryllotalpa Costa, 1853 will seize and consume small crustaceans passing the opening of its tube, and an undescribed species of Grandidierella from northwestern Australia has been observed to feed on insect larvae (Myers and Lowry 2003).
The family Aoridae was first established by Stebbing (1899) with Aora typica Krøyer, 1845 as its type species.Aorid amphipods are characterized by an enlarged male gnathopod 1 and are easily distinguished from congeners by pereopod 7, which is disproportionately longer than pereopod 6.According to the ratio of the length of pereopod 7, groups with pereopod 7 relatively longer than pereopods 5 and 6 have been classified as the family Aoridae, whereas groups with pereopods 5-7 of similar length have been classified as the family Unciolidae (Myers and Lowry 2003).In addition, due to strong sexual dimorphism in the family, the female gnathopod 1 is subequal in size to gnathopod 2, without an especially enlarged or elongated article.

Materials and methods
Specimens were collected with a light trap and hand net from subtidal waters of the East and South Sea, Korea (Fig. 1).The specimens were fixed in 95% ethanol and dissected in glycerol on Cobb's aluminum hole slides.The materials were examined under stereoscopic (Olympus SZX 10) and compound microscopes (Olympus BX 51), and drawings and measurements were made with the aid of a drawing tube.Body length was measured from the end of the rostrum to the end of the urosome, along the dorsal parabolic line of the body.The examined specimens are deposited at the Honam National Institute of Biological Resources (HNIBR), Mokpo, Korea, and the Department of Biological Science, Dankook University (DKU), Cheonan, Korea.Diagnosis.Eyes well developed, oval.Antenna 1 slender, except peduncular article 1, elongated, moderately setose; flagellum longer than peduncle.Antenna 2 densely setose, stout, gland cone bluntly pointed; flagellum short, 3-articulate, with two robust setae on each article distally.Mandible, incisor with five dentate, tricuspidate lacinia mobilis, molar triturative.Maxilla 1, outer plate with 10 dentate setae apically.Gnathopod 1 merochelate, massive, greatly larger than gnathopod 2, covered by plumose setae; coxa with a long robust and a plumose seta on anteroventral corner.Pereopod 7 slender, elongated, longer than pereopods 5 and 6.Uropod 1 with a large inter-ramal process.Uropod 3, outer ramus biarticulate.Telson short, fleshy, truncate distally.
Uropod 1 (Fig. 5F), peduncle subrectangular, length 0.73× inner ramus, with three dorsolateral and two dorsomedial robust setae, and a large inter-ramal process; outer ramus length× 1.09 inner ramus, with two robust setae on both margins, four robust setae on apex; inner ramus with three dorsal and four apical robust setae.
Uropod 2 (Fig. 5G), peduncle subrectangular, subequal in length to inner ramus, with one dorsomedial robust seta; outer ramus length 1.26× inner ramus, with three dorsal and four apical robust setae; inner ramus with three dorsal and four apical robust setae.
Telson (Fig. 5I) short and fleshy, longer than broad, concave distally, each lobe with two lateral robust setae and 5-6 unequal setae near the apex. Female.Unknown.
Etymology.The species name is derived from the Latin gracilis (= slender) and crus (= leg) in reference to the relatively slender basis of pereopod 7.
Left mandible (Fig. 6H) similar to right mandible, but lacinia mobilis with four teeth and accessory setal row composed of eight setae.
Pereopod 6 (Fig. 8C), coxa similar but slightly smaller than coxa 5; basis elongate-ovate, length 1.91× width, anterior margin with two plumose and three setae, posterior margin with row of unequal plumose setae; merus subrectangular, length 0.84× basis, posterior margin with one robust and five simple setae, posterodistal corner with one long and two robust setae; carpus with three robust setae on posterior margin, posterodistal corner with one robust and three setae; propodus slender, length 1.79× carpus, with a row of five robust setae anteriorly; dactylus falcate.
Uropod 2 (Fig. 8F), peduncle short, subrectangular, subequal to inner ramus in length, with two dorsolateral and one dorsomedial robust setae; outer ramus with three dorsal and four terminal robust setae; inner ramus subequal to outer ramus, with two dorsal and three terminal robust setae.
Etymology.The species name is derived from the type locality, Narodo Island, located on the south coast of Korea.

Table 1 .
Morphological characters of Aoroides gracilicrus sp.nov.and related species with numerous plumose setae on anterior margin of basis and carpus of gnathopod 1.