New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca

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Org. Divers. Evol. 6, Electr. Suppl. 10: 1-28 (2006) Gesellschaft für Biologische Systematik URL: http://www.senckenberg.de/odes/06-10.htm URN: urn:nbn:de:0028-odes0610-8 New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca Ch. Oliver Coleman a, *, Exequiel R. Gonzalez b a Museum für Naturkunde Berlin, Humboldt Universität zu Berlin, Invalidenstraße 43, 10115 Berlin, Germany b Facultad de Ecología y Recursos Naturales, Universidad Andrés Bello, Santiago, Chile; also Centro de Estudios Avanzados en Zonas Áridas (CEAZA) and Universidad Católica del Norte, Coquimbo, Chile * Corresponding author, e-mail: oliver.coleman@museum.hu-berlin.de Received 22 October 2004 Accepted 2 November 2005 Abstract Two new species of hyalellid amphipods, Hyalella crawfordi and H. gauthieri, are described from Lake Titicaca; H. echinus (Faxon, 1876) is redescribed. The Hyalella echinus species group is newly proposed for these three species. A group diagnosis and a key is provided. Keywords: Freshwater; Taxonomy, New species; Hyalella echinus; Hyalella crawfordi; Hyalella gauthieri Introduction The distinctive hyalellid fauna of Lake Titicaca has been sampled extensively, but not studied properly. Faxon (1876) described eight species, seven of them from material collected by A. Agassiz and S.W. Garthman in 1875. Chevreux (1904, 1907) described four species collected by Neveulemaire, and redescribed two of Faxon s species. Two additional large sampling efforts have been undertaken: one in 1937 by G.I. Crawford who deposited the material in the Natural History Museum in London, the other by C. Dejoux (then of ORSTOM, France) who collected more than 15,000 specimens (Dejoux 1992). For the present study, part of the material from the NHM was examined, along with specimens kindly provided by Dr. Dejoux. Recently, González and Watling (2003) described two new species and redescribed four others of Hyalella from Lake Titicaca. Material and methods Whole animals were transferred to glycerol, and bodies illustrated using a camera lucida on a Leica Wild M8 dissecting microscope. Specimens were then dissected, the appendages transferred onto slides in glycerol and illustrated using a Leica DMLB light microscope equipped with a camera lucida. Permanent slide mounts were made using Euparal green (Chroma, 3C 240). The type material of the new species is deposited at the Natural History Museum (NHM), London. The sexes were recognized according to gnathopod morphology and the presence of oostegites and penal papillae. Taxonomic section Diagnosis of the Hyalella echinus group of species Male. Head with a pair of teeth anteriorly and a subocular tooth on both sides. Body with teeth on each segment: 2 3 dorsal and 1 lateral on each side. Pleonites with or without posterolateral marginal teeth. Eyes pigmented. Antenna 1 shorter than antenna 2. Antenna 2 less than half body length. Mandible incisor toothed. Maxilla 1 palp longer than wide, reaching more than half length of distance between base of palp and tips of setae on outer plate; inner plate slender, with 2 strong and pappose apical setae. Maxilla 2 inner plate with 1 strong pappose seta on inner margin. Lateral faces of coxal plates of pereopods 1 5 ridged or scul-

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 2 pured. Gnathopod 1 propodus less than twice as long as wide (quadrangular), hammer-shaped, inner face with approximately 10 pappose setae, posterodistal and anterodistal margins without setose scales. Gnathopod 2 propodus ovate, palm longer than posterior margin, slope slightly oblique, anterior edge smooth. Uropod 3 peduncle with some strong distal setae; ramus shorter than peduncle, tapering distally. Telson longer than wide, apically rounded, with some long simple setae that are distributed asymmetrically on the apical margin. Sternal gills on segments 3 to 7. Female. Gnathopod 1 subequal to gnathopod 2. Gnathopod 2 differs from that of the male in the shape and smaller size; propodus length less than twice maximum width, subchelate, palm transverse. Key to the species of the Hyalella echinus group 1. Pereon with 3 rows of dorsal processes... H. crawfordi n. sp. Pereon with only 2 rows of dorsal processes... 2 2. Posterolateral margins of pleon epimera with teeth... H. gauthieri n. sp. Posterolateral margins of pleon epimera without teeth... H. echinus (Faxon, 1876) Hyalella echinus (Faxon, 1876) (Figs. 2 5) Allorchestes echinus Faxon, 1876: 367 368, figs. 19 21. Hyalella echinus (Faxon). Stebbing (1888: 455); Della Valle (1893: 517, pl. 58, figs. 12 13); Stebbing (1906: 576); Barnard and Barnard (1983: 708). Hyalella (Mesohyalella) echina (Faxon). Bousfield (1996: 192). Type material examined. 1 specimen (MCZ = Museum of Comparative Zoology, Harvard, 3110), Bolivia, Lake Titicaca, Llampopata, 12.2.1875, leg. S.W. Garman; 3 specimens (MCZ 3109), as lectotype, except 13.2.1875. Additional material examined. 1) 14 females, 5 males; 2 juveniles; Siripata, G 90, GIC 1001/1, 13.7 m. 2) 1 juvenile (female?), Uruñi Bay, station G. 28, GIC 631, 9 m, 9.7.1937. 3) 1 female, Uruñi Bay, station G. 21, GIC 606, 8.5 m, 9.7.1937. 4) 2 females, 2 juveniles, Rio Desaguadero, GIC 991/1, 27.7.1937. 5) 11 females, 6 males, 3 juveniles, Is. Titicaca, GIC 970/1, 3 m. 6) 1 female, 1 juvenile, Uruñi Bay, station G 39, GIC 650, 3 m, 9.7.1937. 7) 6 females, 1 male, 1 juvenile, Uruñi Bay, station G. 36, GIC 646, 10.5 m, 9.7.1937. 8) 2 females, 1 male, 1 juvenile, Sucuné, station G. 44, GIC 762, 2.4 m, 13.7.1937. 9) 10 females, 12 males, 4 juveniles, Sucuné, station G. 45, GIC 768, 2.9 m, 13.7.1937. 10) 1 male, Sucuné, station G. 51, GIC 814, 7.3 m, 13.7.1937. 11) 1 female, Sucuné, station G. 44, GIC 761, 2.4 m, 13.7.1937. 12) 22 females, 10 males, 8 juveniles Japitse, station P. 9, GIC 502, 3.5 4.5 m, 26.6.1937. 13) 3 females, 2 males, 3 juveniles, Japitse, station P 9, GIC 570, 10 25m, 26.6.1937. 14) 1 female, Japitse, GIC 542, 6 7 m, 26.6.1937. 15) 4 females, 7 males, 1 juvenile, Japitse, GIC 531, 4.5 m, 26.6.1937. 16) 1 female, 1 juvenile, Choccocoya, station P. 8, GIC 497, 3.5 4.5 m, 26.6.1937. 17) 2 males, 4 juveniles, Sucuné, station G 43, GIC 751, 1.2 m, 13.7.1937. 18) 1 female, 1 male, Sucuné, station G 46, GIC 776, 3.6, 13.7.1937. 19) 1 female, 9 males, 7 juveniles, Japitse, GIC 501, 3.5 4.5, 26.6.1937. 20) 4 females, 2 males, (all with very short dorsal processes), nr. Moho, station P. 4, GIC 470, 1.7 1.8 m, 24.6.1937. 21) 4 females, 1 male, 5 juveniles; Siripata Bay, station G. 89a, GIC 999/1, 7.9 m, 30.7.1937. 22) 5 females, 7 males, 1 juvenile; Sucuné, station G. 45, GIC 769, 2.9 m, 13.7.1937. 23) 5 females, 5 males; Sucuné, station G. 43, GIC 752, 1.2 m, 13.7.1937. 24). Description of male (from additional material sample 1; see above). Size 7.3 mm. Body with teeth on each segment: 2 dorsal and 1 lateral on each side (Fig. 2a, b). Pereon segment 1 with 4 dorsal and 2 lateral teeth on each sides, pereon segments 2 7 with 2 dorsal and one lateral on each side. Pleonites 1 3 with 2 dorsal teeth, without lateral processes. Epimeral plate 1 rounded, plate 2 angular, 3 slightly produced (Fig. 2c). Coxae 1 4 slightly overlapping. Coxa 4 strongly tapering, subacute. Coxa 1 slightly shorter than 2 and 3, curved anteriorly. Coxa 3 narrower than 4. Coxa 4 longer than wide, posteroventrally straight. Coxa 5 posterior lobe longer than anterior. Coxa 6 anterior lobe small. Head smaller than first 2 thoracic segments, typically gammaridean, rostrum absent. Eyes pigmented, small, round, located posterior of insertion of antenna 1 (Fig.. 2a). Antenna 1 (Fig. 2d) less than half body length, shorter than antenna 2, longer than peduncle of antenna 2; peduncle longer than head, article 1 longer than 2, article 3 shorter than article 1, subequal to article 2; flagellum of 6 articles, longer than peduncle, basal article not elongated. Antenna 2 (Fig. 2b) less than half body length; peduncle slender, longer than head, article 4 shorter than article 5, setal groups on articles 4 and 5 scarce; flagellum of 9 articles, longer than peduncular article 5, basal article elongated. Basic amphipodan mandible (in the sense of Watling 1993) (Fig. 2f); incisor toothed; lacinia mobilis dentate; molar large, cylindrical, and triturative, accessory seta present. Labrum (Fig. 3b) ventral margin slightly rounded to truncate, covered with hair-like setae. Lower lip (hypopharynx) (Fig. 3d) outer lobes rounded without notches or excavations, mandibular projection of outer lobes round.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 3 Maxilla 1 (Fig. 3c) palp uniarticulate, longer than wide, not reaching insertion of setae on outer plate; inner plate slender, shorter than outer plate, with 2 strong and pappose apical setae; outer plate with 9 stout and serrate spine-like setae. Maxilla 2 (Fig. 2e) inner plate shorter and more slender than outer plate, 1 strong pappose seta on inner margin, outer and inner plates with few hair-like setae. Maxilliped (Fig. 3f) inner plates apically rounded to truncate, with 3 connate setae, pappose setae apically and medially; outer plates longer than inner plates, apically rounded, apical, medial and facial setae simple; palp longer than outer plate, 4 articles; article 2 as wide as long, medial margin with long simple setae; article 3 outer distal face with several long simple setae, inner distal face with long slender setae, inner distal margin with long setae, outer margin with a few long slender setae; dactylus unguiform, shorter than article 3, distal nail present, distal setae simple and shorter than nail, inner margin without setae. Gnathopod 1 (Fig. 3d) subchelate; carpus longer than wide, subequal in length, and wider than propodus, with strong and wide posterior lobe, produced and forming a scoop -like structure, open to the inside, posterior margin pectinate and with a row of pappose setae; propodus width 68 % of length, curved posteriorly, inner face with about ten pappose setae, posterodistal and anterodistal margins without setose scales, palm slope slightly oblique, margin convex, posterodistal angle with robust setae; dactylus claw-like, congruent with palm, with a few short setae on concave inner margin. Gnathopod 2 (Fig. 3a) subchelate; basis posterior margin with 4 6 groups of setae; merus posterodistal margin straight, distal angle subacute; carpus posterior lobe elongated, produced between merus and propodus, inner face pectinate with several pappose setae, anterior distal margin with group of setae; propodus ovate, posterodistal and anterodistal margins without setose scales, palm longer than posterior margin, slope oblique, margin straight, guarded by row of medium sized setae, anterior edge smooth, posterodistal corner with 2 spiniform setae, and with cup for dactylus; dactylus claw-like, congruent with palm, with row of short setae on concave inner margin. Pereopods 3 and 4 (Figs. 4e, 5b) similar: basis with groups of setae on posterior margin; ischium short with protrusion on anterior margin; merus weakly expanded distally, anterodistal corner drawn out; carpus narrow, shorter than merus; propodus longer than carpus; dactylus with nail. Pereopods 5 7 (Fig. 5a, c, d) subequal, slightly longer successively. Pereopod 5 (Fig. 5c) basis posterior lobe longer than wide, smaller than posterior lobe of pereopod 7; merus with 2 posteromarginal setae, proximal and distal setae subequal. Pereopod 6 (Fig. 5a) similar to pereopod 5, but each article longer; basis posterior lobe longer than wide, slightly larger than posterior lobe of pereopod 5, and smaller than posterior lobe of pereopod 7. Pereopod 7 (Fig. 5d) basis to dactylus subequal in dimensions to those of pereopod 6; basis posterior lobe longer than wide. Pleopods (Fig. 5i) not modified. Uropod 1 (Fig. 5g) longer than uropod 2; peduncle longer than rami; rami subequal; inner ramus with 1 dorsal and 4 distal setae, only one longer, without curved setae on inner side of ramus; outer ramus with one dorsal seta and 3 distal setae; peduncle setation present. Uropod 2 (Fig. 5f) rami subequal; inner ramus with 1 dorsal seta and 5 distal setae; outer ramus without dorsal and 3 distal setae; peduncle setation present. Uropod 3 (Fig. 5h) same length as urosomite 3, shorter than peduncle of uropod 1 and peduncle of uropod 2; peduncle globose, wider than ramus, with 2 3 marginal setae; inner ramus absent; outer ramus uniarticulate, shorter than peduncle, tapering distally, with 1 2 apical simple, slender setae and 1 spine-like seta. Telson slightly longer than wide, entire, apically rounded, with some simple setae which are asymmetrically distributed on apical margin. Coxal gills sac-like, in segments 2 to 6. Sternal gills tubular, in segments 3 to 7. Characters of female that differ from male (from additional material sample 1; see above). Gnathopod 1 (Fig. 4a, b) similar to gnathopod 2 and to male gnathopod 1 in size and shape. Gnathopod 2 (Fig. 4c, d) smaller than male gnathopod 2 and shaped differently, propodus length:width ratio = 1.6, subchelate, palm transverse. Habitat. Freshwater, epibenthic, at approx. 1 14 m water depth. Distribution. Endemic to Lake Titicaca in Bolivia and Peru. Hyalella gauthieri n. sp. (Figs. 6 14) Etymology. This species is named for our dear colleague and friend Dr. Gauthier Chapelle, who has studied the gigantism of Baikal amphipods for years and compared his findings with the Lake Titicaca species flock. Type material. Holotype (NHM 2005.95; spirit specimen, 2 slides): male, 7 mm; Lake Titicaca, Uruñi Bay, station G. 41, GIC 689, 0.9 m, 9.8.1937, in Potamogeton, ex coll. Crawford. Paratypes: 14 females, 5 males (NHM 2005.96 105; spirit specimens), as holotype; 1 male (specimen a, see the description below) from unknown locality in Lake Titicaca, ex coll. Dejoux.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 4 Additional material examined. Crawford collection: 1) 1 female, 3, males, 2 juveniles; Taquili Island, R 49.50, GIC 1000/1, 2.7 2.8 m; 20.7.37. 2) 1 female; Uruñi Bay; station G 25; GIC 625; 2.4 m; 9.7.37. 3) 3 females, 1 male; Uruñi Bay, station G 40, GIC 657, 1.3 m; 9.7.37, in Chara. 4) 2 females, Uruñi Bay, station G 40, GIC 668, 1.3 m; 9.7.37, in Potamogeton. 5) 4 females, 3 males; Taman, station GIC 119, 2 3.5 m, 1.5.37, fine mesh dredge. 6) 3 females, 1 male; Taman, station GIC 336, 10 m; 10.6.37. 7) 1 juvenile; Isla Companaria de Ccotos, station GIC 1012; 0.7 m; 5.8.37. 8) 2 females, 1 male; Uruñi Bay, station G24, GIC 620, 1.7 m, 9.7.37. 9) 57 females, 37 males, 8 juveniles; Uruñi Bay, station G. 40, GIC 656, 1.3 m, 9.7.37, in Chara. 10) 5 females, 3 males, 4 juveniles. Uruñi, station GIC 679, 0.9 m; 9.7.37. 11) 1 juvenile, Taman, station G18, MS 261/4, 1.5 m; 8.7.37. 12) 1 female, 1 juvenile; Taman, G19, station MS 258/5, 4.5 m; 8.7.37. 13) 1 female, 4 males, 2 juveniles; Uruñi Bay, station G. 40, GIC 667, 1.3 m, 9.7.1937, in Potamogeton. 14) Dejoux collection: Lake Titicaca, unknown locality. Description of male (specimen a = ex coll. Dejoux). Size 7 mm (holotype), 8.8 mm ( a ). Head smaller than first 2 thoracic segments, typically gammaridean, rostrum absent, with 2 strong teeth anteriorly and a small tooth below the eyes. Eyes pigmented, small, round, located posterior of insertion of antenna 1 (Figs. 6a, 11a). Body with teeth on each segment; pereon segment 1 with 4 dorsal and 2 lateral teeth on each side, on pereon segments 2 7 a pair of dorsal teeth and 1 lateral tooth on each side (Fig. 8b), specimen a bears 1 additional dorsolateral tooth on each side of pereon segment 6 (Fig. 6a), holotype with inconspicuous small protrusions laterally of dorsal teeth on pereonites 2 6 (Fig. 11a). Pleonites 1 3 with 2 dorsal teeth and additionally posterolateral teeth on segments 1 2 (Fig. 9a) in specimen a, a similar tooth on pleonite 3 of holotype (Fig. 11a). Epimeral plate 1 rounded, plate 2 angular, 3 slightly produced (Fig. 11a). Coxae 1 4 slightly overlapping, lateral faces sculptured. Coxa 4 strongly tapering, subacute. Coxa 1 slightly shorter than 2 and 3, curved anteriorly. Coxa 3 narrower than 4. Coxa 4 longer than wide, posteroventral margin straight. Coxa 5 posterior lobe longer than anterior. Coxa 6 anterior lobe small. Coxa 7 without anterior lobe. Antenna 1 (Figs. 6g, 11c) less than half body length, shorter than antenna 2, longer than peduncle of antenna 2; peduncle longer than head, article 1 longer than 2, article 3 shorter than article 1, subequal to article 2; flagellum of 9 articles, longer than peduncle, basal article not elongated. Antenna 2 (Figs. 6b, 11b) less than half body length; peduncle slender, longer than head, article 4 shorter than article 5, setal groups on articles 4 and 5 scarce; flagellum with 12 articles, longer than peduncular article 5, basal article elongated. Basic amphipodan mandible (in the sense of Watling 1993) (Figs. 6f, 11g); incisor toothed; lacinia mobilis dentate; molar large, cylindrical and triturative, accessory seta present. Labrum (Figs. 6d, 11d) ventral margin somewhat rounded to truncate, covered with hair-like setae. Lower lip (hypopharynx) (Figs. 6e, 11f) outer lobes rounded without notches or excavations, mandibular projection of outer lobes rounded. Maxilla 1 (Figs. 7b, 12a) palp uniarticulate, longer than wide, not reaching insertion of setae on outer plate; inner plate slender, shorter than outer plate, with 2 strong and pappose apical setae; outer plate with 9 stout and serrate setae. Maxilla 2 (Figs. 6c, 11e) inner plate slightly shorter and more slender than outer plate, 1 strong pappose seta on inner margin, outer and inner plates covered with hair-like setae. Maxilliped (Figs. 8c, 12b, c) inner plates apically rounded to truncate, with 3 terminal connate setae, pappose setae apically and medially; outer plates longer than inner plates, apically rounded with apical, medial and facial setae; palp longer than outer plate, 4 articles; article 2 as wide as long, medial margin with long simple setae; article 3 outer distal face with several long simple setae, inner distal face with long slender setae, inner distal margin with long setae, outer margin with a few long slender setae; dactylus unguiform, shorter than article 3, distal setae simple and shorter than nail. Gnathopod 1 (Figs. 7c, d, 12d) subchelate; carpus longer than wide, as wide as propodus and subequal in length, with prominent posterior lobe, produced and forming a scoop-like structure, open medially, posterior margin pectinate and with a row of pappose setae; propodus width 56% of length, curved posteriorly, medial face with about ten pappose setae, palm slope slightly oblique, margin weakly convex, posterodistal angle with robust setae; dactylus claw-like, congruent with palm, with a few short setae on concave inner margin (Fig. 12d). Gnathopod 2 (Figs. 7a, 13a, b) subchelate; basis posterior margin with 4 6 groups of setae; merus posterodistal margin straight, distally angular; carpus posterior lobe elongated, produced between merus and propodus, inner face pectinate with several pappose setae, distal margin with a group of setae; propodus expanded distally, palm longer than posterior margin, slope oblique, margin straight, guarded by row of medium sized setae, anterior margin smooth, posterodistal angle with spiniform setae, and with a cup for the dactylus apex; dactylus claw-like, congruent with palm, concave inner margin with row of short setae.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 5 Pereopods 3 (Fig. 9e) and 4 (Fig. 13d) basis to dactylus similar: basis with groups of setae on posterior margin; ischium short with protrusion on anterior margin; merus weakly expanded distally, anterodistal angle drawn out; carpus narrow, shorter than merus; propodus longer than carpus; dactylus with nail. Pereopods 5 7 (Figs. 8d, 10b, c, 14a c) subequal, slightly longer successively. Pereopod 5 (Figs. 10c, 14a) basis posterior lobe longer than wide, smaller than posterior lobe of pereopod 7; merus with 2 groups of posteromarginal setae. Pereopod 6 (Figs. 10b, 14b) basis to dactylus similar to those of pereopod 5, but each article longer; basis posterior lobe longer than wide, slightly larger than posterior lobe of pereopod 5, and smaller than posterior lobe of pereopod 7. Pereopod 7 (Figs. 8d, 14c) basis to dactylus subequal in dimensions to those of pereopod 6; basis posterior lobe longer than wide. Pleopods (Fig. 14d) not modified. Uropod 1 (Figs. 9f, 13f) longer than uropod 2; peduncle longer than rami; rami subequal; inner ramus with 1 dorsal and 3 4 distal setae, only 1 longer; outer ramus with 1 dorsal and 3 distal setae; peduncle setation present. Uropod 2 (Figs. 9b, 13c, 14e) rami subequal; inner ramus with 1 dorsal and 5 distal setae; outer ramus with 3 distal setae; peduncle setation present. Uropod 3 (Figs. 9c, 14f) equal in length to urosomite 3, subequal to peduncle of uropod 1, peduncle globose, wider than ramus, with 2 4 marginal setae; only one ramus present; shorter than peduncle, tapering distally, with 1 2 simple apical slender setae and 1 spine-like seta. Telson (Fig. 9g) slightly longer than wide, entire, apically rounded, with some simple setae which are asymmetrically distributed on the apical margin. Coxal gills sac-like, on segments 2 6. Sternal gills tubular, on segments 3 7. Characters of female that differ from male. Gnathopod 1 (Fig. 10a, d) similar in size and shape to gnathopod 2 (Fig. 8a, e) and to male gnathopod 1. Gnathopod 2 (Fig. 8a, e) smaller than male gnathopod 2 and shaped differently, propodus length:width ratio = 1.6, subchelate, palm transverse. Habitat. Freshwater, epibenthic, at approx. 0.5 10 m water depth. Distribution. Endemic to Lake Titicaca in Bolivia and Peru. Remarks: Specimens from the additional material (see above) samples 1) and 8) have shorter teeth on the posterolateral margins of epimera 1 3. Hyalella crawfordi n. sp. (Figs. 15 20) Etymology. This species is named for Mr. George Crawford, for his tremendous efforts to collect and sort much of the material treated in this study. Type material. Holotype (NHM 2005.90; spirit specimen, 2 slides): male, 9.5 mm; Molinopampa; station P. 23, GIC 868/1, 869/1; 5.6 8 m, ex coll. Crawford. Paratypes (sampling data as holotype): allotype ovigerous female, 6 mm (NHM 2005.89; spirit specimen, 1 slide); 2 females, 2 males (NHM 2005.91 94; spirit specimens). Additional material examined. 1) 2 females, 5 males; off Catachaca; station G109, GIC 1131/3, 3.0 m, 30.8.37; Chara amid scattered Tortora. 2) 1 female, 2 males; off Chucuito; station G105, GIC 1129/3; 2.3 2.5m; 30.8.37; Chara, 50 m outside Tortora. 3) 11females, 19 males; off Catachaca; station G107, GIC 1130/3; 1.3 m; 30.8.37; Chara among scattered Tortora. 4) 6 females, 3 males; Puno Bay; station G101, GIC 1115/4; 0.7 m; 28.7.37; New edge of Tortora, Chara. Description of male holotype. Size 9.5 mm. Head smaller than first 2 thoracic segments, typically gammaridean, rostrum absent, with 2 strong teeth anteriorly and a small tooth below the eyes. Eyes pigmented, small, round, located posterior of insertion of antenna 1 (Figs. 15a, d). Body with teeth on each body segment; pereon segment 1 with 6 dorsal and 2 lateral teeth on each side, pereon segments 2 7 (Figs. 15a, c, d) with 3 dorsal and 1 lateral tooth on each side. Pleonites 1 3 with 3 dorsal teeth and smooth posterolateral margins (Fig. 15a). Epimeral plate 1 rounded, plate 2 angular, 3 slightly produced. Coxae 1 4 slightly overlapping, lateral faces sculptured. Coxa 1 slightly shorter than 2 and 3, apex curved anteriorly. Coxa 2 subequal in length to 3, apically truncate. Coxa 4 (Figs. 15a, 18d) strongly tapering, apex subacute, posteroventral margin straight. Coxa 5 (Figs. 15a, 18d) posterior lobe slightly longer than anterior. Coxa 6 anterior lobe small (Fig. 18b). Coxa 7 (Fig. 19a) without anterior lobe. Antenna 1 (Fig. 16c) less than half body length, shorter than antenna 2, longer than peduncle of antenna 2; peduncle longer than head, article 1 subequal in length to 2, more than twice as wide, article 3 shorter than article 1, slender, slightly shorter than article 2; flagellum of 9 articles, longer than peduncle, basal article not elongated. Antenna 2 (Figs. 15a, 16b) less than half body length; peduncle slender, longer than head, articles 4 shorter than article 5, setal groups on article 4 and 5

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 6 scarce; flagellum with 12 articles, longer than article 5, basal article elongated. Basic amphipodan mandible (in the sense of Watling 1993) (Fig. 15f); incisor toothed; lacinia mobilis dentate; molar large, cylindrical, and triturative, accessory seta present. Labrum (Fig. 15e) ventral margin somewhat rounded to truncated, covered with hair-like setae. Lower lip (hypopharynx) (Fig. 15g) outer lobes rounded without notches or excavations, mandibular projection of outer lobes rounded. Maxilla 1 (Fig. 16e) palp uniarticulate, longer than wide, not reaching insertion of setae on outer plate; inner plate slender, shorter than outer plate, with 2 strong and pappose apical setae; outer plate with 9 stout and serrate setae. Maxilla 2 (Fig. 15b) inner plate slightly shorter and more slender than outer plate; outer and inner plates with few hair-like setae. Maxilliped (Fig. 16a, d) inner plates apically rounded to truncate, with 3 terminal connate setae, pappose setae apically and medially (Fig. 16d); outer plates longer than inner plates, apically rounded with apical, medial and facial setae; palp longer than outer plate, 4 articles; article 2 as wide as long, medial margin with long simple setae; article 3 outer distal face with several long setae, inner distal face and inner distal margin with long slender setae, outer margin with a few long slender setae; dactylus unguiform, shorter than third article, distal setae simple and shorter than nail, inner margin without setae. Gnathopod 1 (Fig. 17c, b) subchelate; carpus longer than wide, subequal in length and as wide as propodus, with prominent posterior lobe, produced and forming a scoop-like structure, directed medially, posterior margin pectinate and with a row of pappose setae; propodus width 71% of length, bent posteriorly, anterior margin without setae, medial face with about ten pappose setae, palm slope slightly oblique, margin weakly convex, posterodistal angle with robust setae; dactylus claw-like, congruent with palm, with a few short setae on concave inner margin. Gnathopod 2 (Fig. 17a) subchelate; basis posterior margin with 4 groups of setae; merus posterodistal margin weakly convex, angular distally; carpus posterior lobe elongated, produced between merus and propodus, inner face pectinate with several pappose setae, distal margin with group of setae; propodus expanded distally, palm longer than posterior margin, slope oblique, margin straight, guarded by row of medium sized setae, anterior edge smooth, posterodistal angle with spiniform setae, and with cup for dactylus apex; dactylus claw-like, congruent with palm, with row of short setae on concave inner margin (Fig. 17a). Pereopods 3 and 4 (Fig. 18a, d) basis to dactylus similar: basis with 2 3 groups of setae on posterior margin; ischium short with protrusion on anterior margin; merus weakly expanded distally, anterodistal angle drawn out; carpus narrow, shorter than merus; propodus longer than carpus; dactylus with nail. Pereopods 5 7 (Figs. 18c, b; 19a) subequal, slightly longer successively. Pereopod 5 (Fig. 18c) basis posterior lobe longer than wide, smaller than posterior lobe of pereopod 7; merus with 2 groups of posteromarginal setae, slightly expanded distally and drawn out posterodistally. Pereopod 6 (Fig. 18b) basis to dactylus similar to those of pereopod 5, but each article longer; basis posterior lobe longer than wide, slightly larger than posterior lobe of pereopod 5, and smaller than posterior lobe of pereopod 7. Pereopod 7 (Fig. 19a) basis to dactylus subequal in dimensions to those of pereopod 6; basis posterior lobe ventrally produced. Pleopods (Fig. 19c) not modified. Uropod 1 (Fig. 19b) peduncle slightly longer than uropod 2; peduncle longer than rami; rami subequal in length; inner ramus with 1 dorsal and 3 4 distal setae, one of those elongate, outer ramus with 2 dorsal setae, and 4 distal setae; peduncle setation present. Uropod 2 (Fig. 19d) rami subequal; inner ramus with 1 dorsal and 3 distal setae; outer ramus with 3 distal setae; peduncle setation present. Uropod 3 (Fig. 19f, g) same length as urosomite 3, subequal to peduncle of uropod 1, peduncle globose, wider than ramus, with 2 marginal setae; only 1 ramus present; shorter than peduncle, tapering distally, with 3 simple apical slender setae and 1 spine-like seta. Telson (Fig. 19e) slightly longer than wide, entire, apically rounded, with some simple setae, asymmetrically distributed on apical margin. Coxal gills sac-like, on segments 2 6. Sternal gills tubular, on segments 3 7. Characters of female that differ from male. Gnathopod 1 (Fig. 20b, c) similar in size and shape to gnathopod 2 (Fig. 20a) and to male gnathopod 1. Gnathopod 2 (Fig. 20a) smaller than male gnathopod 2 and shaped differently, propodus length:width ratio = 1.6, subchelate, palm transverse. Habitat. Freshwater, epibenthic, at approx. 0.5 10 m water depth. Distribution. Endemic to Lake Titicaca in Bolivia and Peru. Discussion Hyalella echinus is one of the species in Lake Titicaca with a unique body morphology bearing rows of dorsal and lateral teeth. The respective numbers and sizes of dorsal and lateral processes on the pereonites and pleonites vary considerably (Fig. 21). The abundant material in the Natural History Museum in London has revealed the presence of several species. The specimens

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 7 were compared with the type material of H. echinus deposited in the Museum of Comparative Zoology at Harvard University. This type material, collected by A. Agassiz and S.W. Garman in 1875 and described by Faxon (1876), shows two rows of dorsal teeth, with posterolateral teeth on the pleon lacking. The male specimen used for the redescription and all other specimens identified as H. echinus correspond in all details with the type material and the original description. Regarding male H. gauthieri n. sp., both the holotype (ex coll. Crawford) and the Dejoux specimen ( a ) bear teeth on the posterolateral margins of the pleon epimera. This is also true for the additional material of this species which was abundant at several sampling stations. A third species, H. crawfordi n. sp., is rather similar to H. echinus. However, all specimens bear an additional row of dorsal processes on all pereon and pleon segments. Thus these animals have, together with the lateral processes, 5 teeth in the cross-section of the tergites (Fig. 8b), instead of 4 as in H. echinus and H. gauthieri n. sp.. Within each of the 3 species there is a considerable variation in length and shape of the body processes. The size of gnathopod 2, for example, varies with the age of the animal. Contrary to this, the variable lengths of the dorsal and lateral tergite processes do not follow any recognizable pattern. There are very short processes (Fig. 21 e, f) and rather long and slender upright teeth (Fig. 21 a, b). As there is apparently no discontinuity between these traits, and with only parts of the lake sampled, it is for the time being impossible to further classify this variation. It is possible that additional species are hidden in this complex. However, there is character discontinuity in the presence or absence of whole rows of teeth on the dorsal body face and the lateral faces of the pleon; we are convinced that these differences indicate the existence of separate species. The characters used in the key are the only traits that can be used to differentiate these 3 populations. Other characters, such as the outline and surface structure of coxal plates or the shape of dorsal teeth, cannot be used as they are variable and do not show discontinuities. A similar case of a low number of separating characters between species has been observed with the Lake Titicaca species Hyalella longispina Gonzalez & Coleman, 2002, which is separable from H. armata (Faxon, 1876) solely by the relative length of a long, conspicuous tooth on the coxa of pereopod 4. The distribution map (Fig. 1) shows that the species of the H. echinus group do not overlap, except for a single co-occurrence of H. echinus and H. gauthieri n. sp. at Uruñi. Hyalella echinus predominately lives on the northeastern shore of the lake, the shores of Isla Titicaca, at Siripata and in the Lago Pequeño at the estuary of Rio Desaguadero. Hyalella gauthieri n. sp. is limited to the Uruñi and Isla Taquili area. Hyalella crawfordi n. sp. was found on west-southwestern shores: in the Puno Bay area and near Molinopampa. The unexpectedly high Hyalella species diversity is probably not due to the age of the lake (for discussion see González and Coleman 2002). Acknowledgements We thank Ms. Jacqueline Meier and Ms. Juliane Zantke for making some of the amphipod drawings, and Dr. Ardis Johnston for the loan of the type material of H. echinus. Thanks also to Ms. Miranda Lowe for the loan of material from the Crawford collection, and for her kind hospitality during our stays at the NHM. References Barnard, J.L., Barnard, C.M., 1983. Freshwater Amphipoda of the World. I. Evolutionary Patterns. II. Handbook and Bibliography. Hayfield Associates. Mt. Vernon, Virginia. Bousfield, E.L., 1996. A contribution to the reclassification of Neotropical freshwater hyalellid amphipods (Crustacea: Gammaridea, Talitroidea). Boll. Mus. Civ. Storia Nat. Verona 20, 175 224. Chevreux, E., 1904. Mission G. de Créqui-Monfort et Sénéchal de la Grange. Note preliminaire sur les amphipodes recueillis par M. le Dr. Neveu-Lemaire dans le Lac Titicaca. (Julliet, 1903). Bull. Soc. Zool. Fr. 29, 131 134, 2 figs. Chevreux, E., 1907. Les amphipodes des lacs des hauts plateaux de l Amérique du Sud, in: Mission Scientifique G. de Créqui-Monfort et Sénéchal de la Grange, Lacs Hauts Plateuaux de l Amerique du Sud, 22 pp., figs. 30 41. Dejoux, C., 1992. The Amphipoda, in: Dejoux; C., Iltis, A. (Eds.), Lake Titicaca: a Synthesis of Limnological Knowledge. Kluwer Academic, Dordrecht, pp. 346 356. Della Valle, A., 1893. Gammarini del Golfo di Napoli. Fauna Flora Golf. Neapel Angrenz. Meeres-Abschn., Monogr. 20: 1 948, 61 pls. Faxon, W., 1876. Exploration of Lake Titicaca by Alexander Agassiz and S.W. Garman. IV. Crustacea. Bull. Mus. Compar. Zool. 3, 361 375, 37 figs. González, E.R., Coleman, C.O., 2002. Hyalella armata (Crustacea, Amphipoda, Hyalellidae) and the description of a related new species from Lake Titicica. Org. Divers. Evol. 2, 261 262 (see also http://senckenberg. de/odes/02-06.htm. González, E.R., Watling, L., 2003. Two new species of Hyalella from Lake Titicaca, and redescriptions of four others in the genus (Crustacea: Amphipoda). Hydrobiologia 497, 181 204. Stebbing, T.R.R., 1888. Report on the Amphipoda collected by H.M.S. Challenger during the years 1873 1876, in: Rep. Sci. Res. Voy. H.M.S. Challenger 1873 1876, Zool. 29, 1 1737, 210 pls. Stebbing, T.R.R., 1906. Amphipoda I. Gammaridae. Tierreich 21, 1 806. Watling, L., 1993. Functional morphology of the amphipod mandible. J. Nat. Hist. 27, 837 849.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 8 Fig. 1: Distribution of Hyalella echinus group species in Lake Titicaca. Circles = H. echinus; open squares = Hyalella gauthieri n. sp.; diamonds = Hyalella crawfordi n. sp.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 9 Fig. 2: Hyalella echinus (Faxon); male, 7.3 mm. (a) left lateral habitus; (b) antenna 2; (c) left aspect of pleon and urosome; (d) antenna 1; (e) maxilla 2, setulation of setae omitted; (f) mandible. Scale bars: a, c = 1 mm; b, d f = 100 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 10 Fig. 3: Hyalella echinus (Faxon); male, 7.3 mm. (a) gnathopod 2; (b) upper lip (labrum); (c) maxilla 1; (d) gnathopod 1; (e) lower lip; (f) maxilliped, right plates and palp omitted. Scale bars: 100 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 11 Fig. 4: Hyalella echinus (Faxon). (a) propodus and dactylus of female gnathopod 1; (b) female gnathopod 1, setation of propodus and dactylus omitted; (c) female gnathopod 2, setation of propodus and dactylus omitted; (d) propodus and dactylus of female gnathopod 2; (e) male pereopod 3. Scale bars: a d = 100 µm, e = 200 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 12 Fig. 5: Hyalella echinus (Faxon); male, 7.3 mm. (a) pereopod 6; (b) pereopod 4; (c) pereopod 5; (d) perepod 7; (e) telson; (f) uropod 2; g: uropod 1; (h) uropods 3; (i) pleopod 1. Scale bars: a d, f, g = 200 µm; e, h, i = 100 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 13 Fig. 6: Hyalella gauthieri n. sp.; male paratype a, 8.8 mm. (a) left lateral habitus; (b) antenna 2; (c) maxilla 2; (d) upper lip (labrum); (e) lower lip; (f) mandible; (g) antenna 1. Scale bars (separately lettered): a = 192 µm; b = 94 µm; c = 47 µm; d = 727 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 14 Fig. 7: Hyalella gauthieri n. sp.; male paratype a, 8.8 mm. (a) gnathopod 2; (b) maxilla 1; (c) gnathopod 1; (d) propodus and dactylus of pereopod 1. Scale bars as in Fig. 6.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 15 Fig. 8: Hyalella gauthieri n. sp.; male paratype a, 8.8 mm; female specimen f (from Additional material item 14; see above), 5.8 mm. (a) female gnathopod 2; (b) transverse aspect of male pereon segment; (c) right side of male maxilliped; (d) male pereopod 7; (e) female gnathopod 2. Scale bars as in Fig. 6.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 16 Fig. 9: Hyalella gauthieri n. sp.; male paratype a, 8.8 mm. (a) left aspect of pleonites 1 3; (b) uropod 2; (c) uropod 3; (d) pereopod 4; (e) pereopod 3; (f) uropod 1; (g) telson. Scale bars as in Fig. 6.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 17 Fig. 10: Hyalella gauthieri n. sp.; male paratype a, 8.8 mm; female c (from Additional material item 14; see above), 5.8 mm. (a) female gnathopod 1; (b) male pereopod 6; (c) male pereopod 5; (d) palm of female gnathopod 1. Scale bars as in Fig. 6.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 18 Fig. 11: Hyalella gauthieri n. sp.; male holotype, 7 mm. (a) left lateral habitus; (b) antenna 2; (c) antenna 1; (d) upper lip (labrum); (e) maxilla 2; (f) lower lip (hypopharynx), damaged; (g) mandible. Scale bars: a = 1 mm; b d = 200 µm; e g = 100 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 19 Fig. 12: Hyalella gauthieri n. sp.; male holotype, 7 mm. (a) maxilla 1; (b) inner and outer plates of maxilliped; (c) maxilliped, setae on right palp omitted; (d) gnathopod 1. Scale bars: a, c, d = 200 µm; b = 100 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 20 Fig. 13: Hyalella gauthieri n. sp.; male holotype, 7 mm. (a) coxa of gnathopod 1; (b) merus to dactylus of gnathopod 2; (c) uropod 2; (d) pereopod 3; (e) pereopod 4; (f) uropod 1. Scale bars: a c = 200 µm; d, e = 500 µm, f = 100 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 21 Fig. 14: Hyalella gauthieri n. sp.; male holotype, 7 mm. (a) pereopod 5; (b) pereopod 6; (c) pereopod 7; (d) pleopod 1; (e) uropod 2; (f) uropods 3. Scale bars: a c = 500 µm; d f = 200 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 22 Fig. 15: Hyalella crawfordi n. sp.; male holotype, 9.5 mm. (a) left lateral habitus; (b) maxilla 2; (c) cross-section through pereon segment; (d) dorsal habitus; (e) upper lip (labrum); (f) mandible; g: lower lip (hypopharynx). Scale bars: a, d = 1 mm; b, f = 100 µm; e, g = 200 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 23 Fig. 16: Hyalella crawfordi n. sp.; male holotype, 9.5 mm. (a) maxilliped; (b) antenna 2; (c) antenna 1; (d) inner plate of maxilliped; (e) maxilla 1; (f) terminal article of maxilliped palp. Scale bars: a c = 200 µm; d f = 100 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 24 Fig. 17: Hyalella crawfordi n. sp.; male holotype, 9.5 mm. (a) gnathopod 2; (b) carpus to dactylus of gnathopod 1; (c) gnathopod 1. Scale bars: a, c = 200 µm; b = 100 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 25 Fig. 18: Hyalella crawfordi n. sp.; male holotype, 9.5 mm. (a) pereopod 3; (b) pereopod 6; (c) pereopod 5; (d) pereopod 4. Scale bars: 500 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 26 Fig. 19: Hyalella crawfordi n. sp.; male holotype, 9.5 mm. (a) pereopod 7; (b) uropod 1; (c) pleopod 1; (d) uropod 2; (e) telson; (f, g) uropods 3. Scale bars: a = 500 µm; b e = 200 µm; f, g = 100 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 27 Fig. 20: Hyalella crawfordi n. sp.; female allotype. (a) gnathopod 2; (b) gnathopod 1; (c) palm of gnathopod 2. Scale bars: 200 µm.

Coleman & Gonzalez: New hyalellids (Crustacea, Amphipoda, Hyalellidae) from Lake Titicaca 28 Fig. 21: Interspecific and intrapopulational variation of male body morphology in the Hyalella echinus group; left column: lateral habitus, right column: dorsal habitus; appendages except coxal plates omitted in figs. a j. (a, b) H. echinus, from sample 21 (see Additional material above); (c, d) H. echinus, from sample 22; (e, f) H. echinus, from sample 20; (g, h) H. gauthieri n. sp., from sample 9; (i, j) H. gauthieri n. sp., from sample 13; (k, l) H. crawfordi n. sp., holotype.