o. 39, pp. 429-432 22 January 1976 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON r^ PARAMETOPELLA INQUILINUS, NEW SPECIES FROM DELAWARE BAY OYSTER BEDS (AMPHIPODA: STENOTHOIDAE ) BY Les Watling College of Marine Studies, University of Delaware, Lewes, Delaware 19958 The genus Parametopella is, at present, characterized by the following features (Barnard, 1969): Hnear article 2 of pereo- pods 4 and 5; uniarticulate palp of maxilla 1; mandible without palp. To date, only three species in this genus are known: P. stelleri Gurjanova from the Russian Arctic, P. ninis Barnard from southern California, and P. cypris ( Holmes ) from north- eastern North America. This paper describes a new species of Parametopella from the polyhaline waters of Delaware Bay, U.S.A. Stenothoidae Parametopella Gurjanova, 1938 Parametopella inquilinus, new species Figures 1-2 Diagnosis: Antenna 1, peduncle segments 1 and 2 subequal in length; gnathopod 2 powerful, palm with large teeth near hinge, excavate pos- teriorly with strong tooth on posterior corner; coxal plate 4 greatly ex- panded covering coxae 3 through 7. Description of male: length 3.0 mm. Head small, interantennal angle rounded. Antennae about % length of body. Antenna 1 peduncle article 1 stout, wider than article 2; articles 1 and 2 of subequal length; article 3 about ^/4 length of article 2. An- tenna 2 peduncle nearly as long as antenna 1; last 2 peduncle articles subequal in length; flagellum of 4 to 6 segments. Mouthparts typical for genus. Mandible without palp; maxilla 1 palp uniarticulate; maxilliped outer plate vestigial, inner plate small, sparsely setose, palp with few, strong setae. 39— Proc. Biol. Soc. Wash., Vol. 88, 1976 (429) 430 Proceedings of the Biological Society of Washington Fig. 1. Parametopella inquilinus, new species: a. Side view of body; b, Antenna 1; c, Antenna 2; d. Third maxilliped; e, Male gnathopod 1; f, Male gnathopod 2. Gnathopod 1 simple; dactyl finely pectinate; propodus with 3 setae on posterior margin; article 5 equal in length to article 6, posterior mar- gin with 3 groups of strong, pectinate setae; distal margin of article 4 with cluster of pectinate setae and group of short spines; article 2 with anterior row of long, simple setae. Gnathopod 2 strong; palm of propodus strongly excavate between distal group of teeth and large proximal tooth; article 5 with cluster of pectinate setae on postero-distal corner; article 3 with thin, transparent, anteriorly-directed projection; article 2 armed with anterior row of short, simple setae; coxal plate large, not covered distally by coxal plate 4, lower margin with several short spines. Amphipod from Delaware oyster beds 431 Fig. 2. Parametopella inquilinus, new species: a, Pereopod 1; b, Uro- some; c. Female gnathopod 1; d, Female gnathopod 2. Pereopod 3 coxal plate short, sharply tapered anteriorly, lower margin lightly armed along anterior portion; article 2 with 3 proximal and 2 distal spines along anterior margin; appendage notable for its lack of setation. Pereopod 4, coxal plate large, extending anteriorly to overlap slightly coxal plate 2 and posteriorly to cover coxal plate 7. Pereopods 5-7, article 2 slender. Urosome segments 2 and 3 fused; uropod 1 outer ramus with single spine, peduncle with 7 spines; luropod 2, peduncle with 2 dorsal and single distal spine, rami without spines; uropod 3 uniramous, unarmed, two segments of ramus equal in length to peduncle. Telson entire, with- out spines. Female: Similar to male; gnathopod 1 article 2 anterior margin more setose; palm of gnathopod 2 not as strongly excavate. Holotype: $ , USNM No. 152671. Paratypes: 23$ 9, USNM No. 152672. Type-locality. Oyster beds in Delaware Bay, 75°22'W longitude, 39°12'N latitude; recorded saHnity range 18-25%<7, temperature range 1-26°C, depth 8 m; substratum consists of hard, oyster shell reefs inter- calated with muddy shells and mud (Maurer and Watling, 1973). 432 Proceedings of the Biological Society of Washington Distribution: This species has thus far been found only in Delaware Bay. It occurs on hard substrata, usually in association with the hydroid Tubularia crocea. When the hydroid is found on folding plates, Para- metopella inquilinus, Parapleustes aestuarius Watling and Maimer, and Stenothoe minuta Holmes are found in large numbers in the sediment trapped at the base of the colony. In the oyster community, Maiu-er and Watling ( 1973 ) incorrectly identified this species as P. cypris. Relationships: This species differs from P. stelleri (see Giujanova, 1951 ) by its lack of an anteriorly-directed process on antenna 1 peduncle segment 1. It differs from P. ninis (see Barnard, 1962) by the large excavation of the pahn of gnathopod 2 and by the short coxal plate 3. P. vulgaris can also be distinguished from P. cypris (see Holmes, 1905; Bousfield, 1973) by the form of gnathopod 2, and also by the antenna 1 peduncle segment 1 being shorter than segments 2 and 3 combined, the very long peduncle segments 4 and 5 of anteima 2, and by coxal plate 4 not covering the distal end of coxal plate 2. Etymology: The specific name, from the Latin noun inquilinus = so- journer, refers to its inquilinous Ufe habit. Acknowledgments: The author would like to thank Mr. Tom Dean who brought the specimens to his attention and Dr. Don Maurer whose grants provided the funding under which the specimens were collected. LiTERATUKE CiTED Barnard, J. L. 1962. Benthic marine Amphipoda of southern Cali- fornia: families Amphilochidae, Leucothoidae, Stenothoidae, Argissidae, Hyalidae. Pacific Nat. 3:116-163. . 1969. The families and genera of marine gammaridean Am- phipoda. U.S. Nat. Mus. BuU. 271:1-535. Bousfield, E. L. 1973. Shallow-water gammaridean Amphipoda of New England. Cornell University Press, Ithaca, xiv + 312 pp. GuRjANOVA, E. 1951. Bokoplavy morej SSSR i sporedel'nykh vod ( Amphipoda-Gammaridea ) . Opred. po Faune SSSR, Akad. Nauk SSSR, 41:1-1029. Holmes, S. J. 1905. The Amphipoda of southern New England. Bull. U.S. Bur. Fish. 24:459-529. Maxjrer, D., AND Les Watling. 1973. Studies on the oyster com- munity in Delaware: the effects of the estuarine enviroimient on the associated fauna. Int. Rev. Ges. Hydrobiol. 58:161-201.