The freshwater amphipods Hyalella Smith , 1874 in Chile ( Crustacea : Amphipoda )

The Chilean fauna of amphipods has been poorly studied. Freshwater amphipods in Chile have a single genus in epigean environments. Seven species of the genus Hyalella are reported for Chile: H. simplex; H. fossamancinii, H. kochi; H. chiloensis; H. costera; H. araucana, and H. franciscae. A short diagnosis, a key and figures are given for each species.

Hyalella fossamancinii, Cavalieri, 1959, H. araucana Grosso & Peralta, 1999, and H. franciscae González & Watling, 2003a are part of what has been called the "patagonica complex".This group is named after H. patagonica (Cunningham, 1871) the first described species of the complex.Most of the species have a rather restricted distribution in the extreme south of South America.Bousfield (1996) proposed for Chile in this complex, species "A" now H. araucana, species "B" now H. franciscae and species "C" not described yet (González & Watling 2003a).Hyalella araucana was described as nomen novum by Grosso & Peralta 1999 in replacement of H. patagonica.
Here a short description is given for the seven valid species recorded in Chile.The figures in this work are modified from the original descriptions.A discussion of the species previously recorded for Chile is also included.
Diagnosis: body surface smooth.Coxa 4 excavated posteriorly.Eyes pigmented.Antenna 1 shorter than antenna 2. Mandible incisor toothed.Maxilla 1 palp longer than wide, reaching more than half length the distance between base of palp and tip of setae on outer plate; inner plate slender, with two strong and pappose apical setae.Maxilla 2 inner plate with two apposed strong pappose setae on inner margin (Fig. 1F).Gnathopod 1 propodus length less than two times maximum width (quadrangular), hatched shape, inner face with ten pappose setae, disto-posterior and disto-anterior borders without setose scales.Gnathopod 2 propodus ovate, palm length the same as posterior margin, slope slightly oblique, anterior edge smooth.Peraeopods 3 and 4 merus and carpus posterior margin with three hind marginal clusters of short setae; propodus posterior margin with two to four groups of setae.Uropod 3 peduncle with four strong distal setae; outer ramus shorter than peduncle, basal width two times or less tip of ramus.Telson as wide as long, apically rounded, with more than two small or minute setae, asymmetrically distributed on the apical margin.Sternal gills in segments 3 to 7.
Characters of female that differ from male.Size, 9.8 mm.Antenna 1 flagellum with seven articles.Antenna 2 weaker than in male, flagellum with eight articles.Gnathopod 1 similar in size, and different in shape to gnathopod 2; similar to male gnathopod 1 in size and shape.Gnathopod 2 different from male gnathopod 2 in shape and smaller, propodus length less than two times maximum width, normally subchelate, palm transverse.
Remarks.This species was erected as a nomen novum for H. patagonica (Cunningham, 1871), which is not described in the original paper and poorly figured.Grosso & Peralta (1999) gave a long list of characters for distinguishing this species from H. neonoma.The species are very close, but differ among other characters, in the length of palp in maxilla 1, setation and palm border in propodus of gnathopod 2 in male, and setation of peduncle in uropod 3. The figures of H. sp.A given by Bousfield (1996) correspond well with this species.
Diagnosis: body surface smooth.Coxa 4 excavated posteriorly.Eyes pigmented.Antenna 1 shorter than antenna 2. Antenna 2 less than half body length.Mandible incisor toothed.Maxilla 1 palp minute, reaching less than half length the distance between base of palp and tip of setae on outer plate; inner plate slender, with two strong and pappose apical setae.Maxilla 2 inner plate with one strong pappose seta on inner margin (Fig. 2F).Gnathopod 1 propodus length less than two times maximum width (quadrangular), hammer shape, inner face with nine pappose setae, setose scales on disto-posterior and distoanterior border.Gnathopod 2 propodus ovate, palm length the same as posterior margin, slope slightly oblique, anterior edge smooth.Peraeopods 3 and 4 merus and carpus posterior margin with five to six hind marginal clusters of long setae; propodus posterior margin with five to eight groups of setae.Uropod 3 peduncle with four strong distal setae; outer ramus longer than peduncle, basal width two times or less tip of ramus.Telson longer than wide, apically truncated, with more than two, long and short simple setae symmetrically distributed in two groups, occasionally with shorter setae close to the main setae.Sternal gills in segments 3 to 7.
Characters of females that differ from males: Size, 7.4 mm.Antenna 1 flagellum with six articles.Antenna 2 similar in shape to male, flagellum with nine articles.Gnathopod 1 similar in size, and same shape to gnathopod 2; similar to male gnathopod 1 in size and shape.Gnathopod 2 different from male gnathopod 2 in shape and smaller, propodus length two to three times maximum width, normally subchelate, palm transverse.
Remarks: This species is close to H. curvispina in its general morphology, Fig. 2: Hyalella chiloensis male, length 8.1 mm, female 7.4 mm.Modified from González & Watling (2001).Symbols as in Fig. 1.The scale is indicated as a small bar on each appendices: "a" is equivalent to 103 µm; "b" is equivalent to 50 µm; "d" is equivalent to 330 µm.
especially uropod 3, and gnathopods, but differs in the type of setae on the telson, (H.curvispina has shorter and stronger setae on telson), a shorter article 2 in maxillipedal palp, males bear nine setae on inner side of propodus in gnathopod 1, and longer setae on merus and carpus in peraeopods 3 and 4 (see Shoemaker 1942).The main characteristic that distinguishes these two species is the presence of six pairs (from segment 2 to 7) of sternal gills in H curvispina, while H. chiloensis has only five pairs (from segment 3 to 7).This feature has been overlooked by or not considered of importance by many authors (Ruffo 1947), or miscounted in several descriptions.The consistency of this character makes it relevant in the evolutionary relationships within the genus.
Diagnosis: body surface smooth.Coxa 4 excavated posteriorly.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 half length the distance between base of palp and tip of setae on outer plate; inner plate slender, with two strong and pappose apical setae.Maxilla 2 inner plate with one strong pappose seta on inner margin.Gnathopod 1 propodus length less than two times maximum width (quadrangular), hammer shape, inner face with seven pappose setae, setose scales on disto-posterior and distoanterior border.Gnathopod 2 propodus rectangular elongated, palm shorter than posterior margin, slope oblique, anterior edge smooth.Peraeopods 3 and 4 merus and carpus posterior margin with three hind marginal clusters of short setae; propodus posterior margin with two to four groups of setae.Uropod 3 peduncle with four strong distal setae; outer ramus longer than peduncle, basal width two times or less tip of ramus.Telson as wide as long, apically rounded, with two widely apart, long simple setae, symmetrically distributed, occasionally with shorter setae close to the main setae.Sternal gills in segments 3 to 7.
Characters of females that differ from males.Size, 6.1 mm.Antenna 1 flagellum with eight articles.Antenna 2 similar in shape to male, flagellum with nine articles.Gnathopod 1 similar in size, and same shape to gnathopod 2; similar to male gnathopod 1 in size and shape.Gnathopod 2 different from male gnathopod 2 in shape and smaller, propodus length two to three times maximum width, normally subchelate, palm transverse.Additionally, coxa 6, anterior lobe is very small; maxilla 2, inner plate subequal in length to outer plate; maxilliped, article 2 as wide as long; gnathopod 1 propodus with one or two setae on anterior border, inner face without small triangular setae; peraeopod 5 basis posterior lobe deeper than wide and similar to posterior lobe of peraeopod 7, which is wider than deep; uropod 3 with six simple apical slender setae.
Remarks: this species was collected in freshwater sources near the coast, along most of the continental Chilean territory.It is the only species present in lowland areas from Paposo in Antofagasta to Concepción.From this point south and down to Valdivia, it is found in the same areas as H. chiloensis, but rarely together in the same locality.Most of the specimens collected were females.Only in La Ligua and Limache, males were found in very low densities.H. costera differs from H. chiloensis in the setation on the inner side of propodus in gnathopod 1, narrower propodus on gnathopod 2, the setation of merus and carpus in peraeopods 3 and 4, setation of telson and the epimeral plate 1.The main difference of H. costera with H. curvispina is the setation of the telson and like in H. chiloensis, it has only five pairs of sternal gills.The morphological characteristics of this species differ considerably from any of the species in the "azteca complex".The latter is mainly distributed in North America, with possible incursions in Central America.The presence of H. azteca in Chile is highly improbable.
Diagnosis: body surface smooth.Coxa 4 excavated posteriorly.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 the distance between base of palp and tip of setae on outer plate; inner plate slender, with two strong and pappose apical setae.Maxilla 2 inner plate with one strong pappose seta on inner margin.Gnathopod 1 propodus length less than two times maximum width (quadrangular), hatched shape, inner face with more than ten pappose setae, disto-posterior and disto-anterior borders without setose scales.Gnathopod 2 propodus  (1959).Symbols of figures are: (A), gnathopod 1 male; (B) gnathopod 2 male; (C) gnathopod 1 female; (D) gnathopod 2 female; (E) maxilla 1; (F) uropod 1; (G) uropod 3; (H) telson.The scale is indicated as a small bar on each appendices: "a" is equivalent to 500 µm; "b" is equivalent to 300 µm; "c" is equivalent to 200 µm; "d" is equivalent to 150 µm; "e" is equivalent to 100 µm; and "f" is equivalent to 2 mm.ovate, palm length the same as posterior margin, slope slightly oblique, anterior edge smooth.Peraeopods 3 and 4 merus and carpus posterior margin with four hind marginal clusters of short setae; propodus posterior margin with five to eight groups of setae.Uropod 3 peduncle with four strong distal setae; outer ramus shorter than peduncle, basal width two times or less tip of ramus.Telson wider than long, apically quadrate, with more than two small or minute setae, asymmetrically distributed on the apical margin.Sternal gills in segments 3 to 7.
Characters of female that differ from male.Size, 5.6 mm.Antenna 1 flagellum with eight articles.Antenna 2 similar in shape to male, flagellum with nine articles.Gnathopod 1 similar in size, and same shape to gnathopod 2; similar to male gnathopod 1 in size.Gnathopod 2 different from male gnathopod 2 in shape and smaller, propodus length less than two times maximum width, normally subchelate, palm transverse.
Remarks.The distribution of this species, in Chile and Argentina, is much northern than the distribution of other members of the "patagonica" group.However, the characteristic hatch shape of propodus in gnathopod 1 represents the common feature for the species complex.The record of H. andina (Philippi, 1860) a freshwater amphipod for the Atacama desert (Cachinal de la Sierra, Agua de Profetas (locality not longer exist with this name), and Riofrio), is hardly comparable to any of the species present in Chile.The description is very general and no figures are given.However, the mention of small eyes and triangular gnathopod 1 could put this species closest to H. fossamancinii.Since the holotype of H. andina is not available and the description is poor, it is better to consider Hyalella andina a nomen dubium.Hyalella.fossamancinii has been recorded for San Juan in Argentina, at high altitude, close to the border with Chile, so it is not surprising to find it in the Chilean part of the Andes.This species is close to H. franciscae, for details see the remarks section in the latter species.
Diagnosis: body surface smooth.Coxa 4 excavated posteriorly.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 base of setae on outer plate; inner plate slender, with two strong and pappose apical setae.Maxilla 2 inner plate with one strong pappose seta on inner margin.Gnathopod 1 propodus length less than two times maximum width (quadrangular), hatched shape, inner face with more than ten pappose setae, disto-posterior and disto-anterior borders without setose scales.Gnathopod 2 propodus triangular, palm longer than posterior margin, slope oblique, anterior edge smooth.Peraeopods 3 and 4 merus and carpus posterior margin with four hind marginal clusters of long setae; propodus posterior margin with five to eight groups of setae.Uropod 3 peduncle with five strong distal setae; outer ramus same length as peduncle, basal width more than two times tip of ramus.Telson wider than long, apically rounded, with more than two, long and short simple setae, asymmetrically distributed on the apical margin.Sternal gills in segments 3 to 7.
Characters of females that differ from males.Size, 11.4 mm.Antenna 1 flagellum with seven articles.Antenna 2 similar in shape to male, flagellum with ten articles.Gnathopod 1 similar in size, and same shape to gnathopod 2; similar to male gnathopod 1 in size.Gnathopod 2 different from male gnathopod 2 in shape and smaller, propodus length less than two times maximum width, normally subchelate, palm transverse.
Remarks: this species is close to H. fossamancinii, but differs in having 16 setae on the inner face of propodus in gnathopod 1; long setae on posterior margin of merus and carpus of peraeopods 3 and 4; long ramus on uropod 3; long setae on posterior margin of telson; several setae on uropod 1, and bigger eyes.The figures given by Bousfield (1996) of H. sp.B correspond well with this species.
Diagnosis: body surface smooth.Coxa 4 excavated posteriorly.Eyes pigmented.Antenna 1 shorter than antenna 2. Antenna 2 less than half body length.Mandible incisor toothed.Maxilla 1 palp short, reaching less than half length the distance between base of palp and tip of setae on outer plate; inner plate slender, with two strong and pappose apical setae.Maxilla 2 inner plate with one strong pappose seta on inner margin.Gnathopod 1 propodus length less than two times maximum width (quadrangular), hammer shape, inner face with seven pappose setae, setose scales on disto-posterior and disto-anterior border.Gnathopod 2 propodus ovate, palm shorter than posterior margin, slope slightly oblique, anterior edge smooth.Peraeopods 3 and 4 merus and carpus posterior margin with three to four hind marginal clusters of short setae; propodus posterior margin with five to eight groups of setae.Uropod 3 peduncle with four strong distal setae; outer ramus shorter than peduncle, basal width two times or less tip of ramus.Telson as wide as long, apically truncated, with two widely apart, long simple setae, symmetrically distributed, occasionally with shorter setae close to the main setae.Sternal gills in segments 3 to 7.
Characters of females that differ from males.Size, 5.5 mm.Antenna 1 flagellum with six articles.Antenna 2 flagellum with eight articles.Gnathopod 1 similar in size, and same shape to gnathopod 2; similar to male gnathopod 1 in size and shape.Gnathopod 2 different from male gnathopod 2 in shape and smaller, propodus length two to three times maximum width, normally subchelate, palm transverse.
Remarks: Hyalella kochi is common only at high altitude.It is very characteristic for the equal length of ramus and peduncle in uropod 3 and big ovoid eyes.It is found together with H. fossamancinii.Both species are common and the male-female ratio is 1:1.The amphipods collected by S. W. Garman on January 19, 1875 in Moro, Lake Titicaca, Perú and San Antonio, Pisagua, northern Chile, (the latter close to the localities examined here) were assigned by Faxon (1876) to Allorchestes dentata inermis.The two sets of specimens deposited in the Museum of Comparative Zoology, Harvard University (USA) do not correspond to the same species.The specimens from Chile are closely related to H. kochi; however, a more detailed study of the specimens seems necessary.Hyalella kochi is a species of wide distribution in the Andes, it has been found in coastal waters of Lake Titicaca, living sympatrically with H. tiwanaku González & Watling, 2003c, and , 1943in Bousfield, 1996: 192. Hyalella species "S" Bousfield, 1996 (in part): 195-196, fig. 6.
Diagnosis: body surface smooth.Coxa 4 excavated posteriorly.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 half length the distance between base of palp and tip of setae on outer plate; inner plate slender, with two strong and pappose apical setae.Maxilla 2 inner plate with one strong pappose seta on inner margin.Gnathopod 1 propodus length less than two times maximum width (quadrangular), hammer shape, inner face with seven pappose setae, setose scales on disto-posterior and disto-anterior border.Gnathopod 2 propodus ovate, palm shorter than posterior margin, slope slightly oblique, anterior edge smooth.Peraeopods 3 and 4 merus and carpus posterior margin with four hind marginal clusters of short setae; propodus posterior margin with two to four groups of setae.Uropod 3 peduncle with three strong distal setae; outer ramus shorter than peduncle, basal width more than two times tip of ramus.Telson as wide as long, apically rounded, with two widely apart, strong setae, symmetrically distributed, no additional apical setae present.Sternal gills in segments 3 to 7. Fig. 7: Hyalella simplex, male 7.8 mm, female 8.1 mm.Modified from González & Watling (2003a).Symbols as in Fig. 4. Scale as in Fig. 5 Hyalella simplex, macho, largo 7,8 mm, female 8,1 mm.Modificada de González & Watling (2003a).Símbolos como en Fig. 4. Escala de tamaño como en Fig. 5.
Characters of females that differ from males.Size, 8.1 mm.Antenna 1 flagellum with nine articles.Antenna 2 flagellum with eleven to fourteen articles.Gnathopod 1 similar in size, and same shape to gnathopod 2; similar to male gnathopod 1 in size and shape.Gnathopod 2 different from male gnathopod 2 in shape and smaller, propodus length less than two times maximum width, normally subchelate, palm transverse.
Remarks: the distribution of H. simplex is confined to the extreme south of South America, where the "patagonica complex" dominates the freshwater habitat.The description by Schellenberg (1931)  The species pictured in his work correspond to the material from Punta Arenas (Chile).The material from Putabla and Quilpué (Chile) correspond to H. costera.Type material from Schellenberg's original sampling was not available, but material from the same localities was collected and analyzed.H. simplex differs from H. kochi in the shape and setation of telson, the longer palp in maxilla 1, the several connate setae on inner plate and wider article 2 of palp in maxilliped, and the longer propodus in female gnathopod 2. This species was mistakenly described as H. curvispina by Grosso & Peralta (1999).H. simplex has sternal gills in segments 3 to 7, H. curvispina in segments 2 to 7.These authors in the description of this species include populations as far north as Concepción (Chile).In the samples analyzed in this work from that area, H. simplex was not present.Grosso & Peralta (1999) based their identifications on the presence of curved setae on inner ramus of uropod 1.This character is common in several species with very different general morphologies and distribution of sternal gills.

DISCUSSION
The information gathered for this work from new material collected in Chile, and the examination of type material in most cases, indicates that the synonymies proposed by Barnard & Barnard (1983) and the distributions proposed by González (1991aGonzález ( , 1991b) ) are no longer valid.H. gracilicornis is a species from the Amazonian basin and its area of influence.The morphological characteristics of this species (González & Watling 2003b) do not agree with any of the species found in Chile.Hyalella azteca has been mention for South America and Chile several times (Ruffo 1947, González 1991a, Villarroel & Graziani 1995).However, the redescription of the species by González & Watling (2002b) makes it clear that the morphology is not present in South America.Unfortunately, some countries have imported specimens of H. azteca from U.S.A. to be used in toxicological studies, that may have introduced the species into natural habitats.The azteca morphology has not been found for Chile yet.Hyalella andina most probably corresponds to H. fossamancinii, but it is not possible to validate it.H. simplex is not synonym with H. curvispina.The material reported by Schellenberg (1931) comprises and array of different species, the drawings and description in his publication correspond to H. simplex.Samples of H. curvispina from Argentina, Uruguay and Brazil indicates that the morphology, although variable, does not correspond with the ones present in Chile.The samples analyzed of H. araucana indicates that its distribution is restricted to areas near Punta Arenas (Chile) and probably toward the east into Argentina, this distribution agrees with the type locality of H. patagonica.Hyalella franciscae has a distribution northwest of Punta Arenas toward Torres del Paine National Park.The former H. patagonica (Cunningham, 1871) could be any of the species in the complex.
now only known for Bolivia and Perú, respectively.
LITERATURE CITED BARNARD JL & CM BARNARD (1983) Freshwater Amphipoda of the world.I. Evolutionary patterns and II.Handbook and bibliography.Hayfield Associates, Mt.Vernon, Virginia, USA.830 pp.