Hyalella gauchensis,

Morgana Tais Streck, Giovanna Monticelli Cardoso, Stella Gomes Rodrigues, Daniel Angelo Sganzerla Graichen & Daniela Da Silva Ca, 2017, Two new species of Hyalella (Crustacea, Amphipoda, Hyalellidae) from state of Rio Grande do Sul, Southern Brazil, Zootaxa 4337 (2), pp. 263-278: 269-276

publication ID

https://doi.org/10.11646/zootaxa.4337.2.5

publication LSID

lsid:zoobank.org:pub:9022EDDB-E12F-4A80-9FB7-57325653A066

persistent identifier

http://treatment.plazi.org/id/039287E8-FFB7-AD45-51DA-FCC4C38CFDAE

treatment provided by

Plazi

scientific name

Hyalella gauchensis
status

n. sp.

Hyalella gauchensis  n. sp. Streck & Castiglioni

Material examined: Holotype male, body length = 10.56 mm, head length = 0.64 mm (MNRJ 25901); Allotype female ( MNRJ 25902View Materials). Brazil, state of Rio Grande do Sul, Palmeira das Missões municipality, Sítio Taqui (27°57'54.30"S 53°14'03.09"W), August, 10, 2012, Castiglioni, D.S. coll.GoogleMaps 

Paratypes: MNRJ 25903 (20 males and 20 females), CCUFLA 0 390. All specimens with the same data as the holotype, August, 10, 2012, Castiglioni, D.S. coll. Mean body length of male paratypes: 10.78 ± 1.88 mm and female paratypes: 5.52 ± 1.40 mm.

Type-locality. Brazil, state of Rio Grande do Sul: Sítio Taqui (27°57'54.30"S 53°14'03.09"W, state of Rio Grande do Sul, Palmeira das Missões municipality, artificial pond (Várzea river basin), 539 meters of altitude, August, 10, 2012.

Diagnosis. Maxilla 2 inner plate with 10 serrulate setae and two robust papposerrate apical setae. Gnathopod 1 posterior lobe of carpus with polygonal pattern with one row of serrate setae and one row of denticles in combscales, propodus inner face with five long serrate setae and 9–10 short serrate setae, hammer-shaped, posterior and anterior distal margins with comb-scales. Gnathopod 2 carpus wider than long, posterior lobe with polygonal pattern and one row of comb-scales and serrate setae and one row of denticles in comb-scales, propodus ovate, longer than wide, palm longer than posterior margin of propodus, slope oblique, palm margin convex, posterior distal corner with cup for dactylus, dactylus reaching the lobe of propodus. Pleopods rami with long plumose setae. Uropod 1 inner ramus of male with one long curved setae followed by row of three small cuspidate setae. Uropod 2 inner ramus apex with 11 cuspidate setae. Uropod 3 peduncle with six cuspidate setae apically. Telson (male) as long as wide, with six apical cuspidate setae distributed in three clusters of two setae each, six plumose setae laterally. Coxal gills sac-like present on pereonites 2 to 6 and sternal gills tubular on pereonites 2 to 7.

Description of male. ( Fig. 24View FIGURES 24 – 32) Mean body length: 10.78 ± 1.88 mm, mean head length: 0.70 ± 0.18 mm (n=20). Body surface smooth; epimeral plates not acuminate.

Head longer than the first thoracic segments, rostrum absent. Eyes round, pigmented ( Fig. 24View FIGURES 24 – 32).

Antenna 1 ( Fig. 25View FIGURES 24 – 32) shorter than antenna 2, less than half body length; peduncle not surpassing head length, flagellum with 11 articles, longer than peduncle; aesthetascs occurring distally on flagellum after article 3.

Antenna 2 ( Fig. 26View FIGURES 24 – 32) peduncle surpassing the second pereonite, less than half body length, peduncle slender; flagellum with 15 articles and longer than peduncle.

Upper lip ( Fig. 27View FIGURES 24 – 32) margin rounded, distal border covered by several short setules on dorsal and ventral faces.

Basic amphipodan mandible ( Fig. 28View FIGURES 24 – 32) (in sensu of Watling 1993), without palp; incisor toothed; left lacinia mobilis with five teeth and setae row of left mandible with three long and three short pappose setae; molar process large, cylindrical and with one long accessory seta.

Lower lip ( Fig. 29View FIGURES 24 – 32) lobes rounded, with several setules on dorsal and ventral faces.

Maxilla 1 ( Fig. 30View FIGURES 24 – 32) palp uniarticulate, short, longer than wide, reaching less than half length the distance between the base of the palp and tip of setae on outer plate; inner plate shorter and slender than outer plate, with two long apical papposerrate setae, and some setules on the inner margin; outer plate with seven serrate setae.

Maxilla 2 ( Fig. 31View FIGURES 24 – 32) inner and outer plates of similar sizes; inner plate with several simple setae, ten serrulate setae and two papposerrate apical setae; outer plate with several simple long setae apically; outer and inner plates with several setules.

Maxilliped ( Fig. 32View FIGURES 24 – 32) inner plate apically rounded, longer than wide, with three apical cuspidate setae and simple setae apically, several pappose setae on inner margin; outer plate with simple apical setae; palp with four articles, with simple setae and few pappose setae; dactylus unguiform, shorter than propodus, with simple and pappose setae and comb-scales.

Gnathopod 1 ( Fig. 33View FIGURES 33 – 34) subchelate; coxal plate wider than long; basis and ischium with few simple setae dorsally; merus without setae; basis, ischium and merus with comb-scales posterodistally; carpus longer than wide, longer than propodus, with strong lateral distal lobe produced and forming a scoop-like structure with polygonal pattern and pectinate border, one row of serrate setae and one row of denticles in comb-scales, and ventral face with three serrate setae; propodus longer than wide, propodus length 1.5 times the maximum width (rectangular), hammer-shaped, inner face with five long serrate setae and 9–10 short serrate setae, posterior and anterior distal margins with denticles in comb-scales, disto-anterior border with a cluster of simple setae, palm slope oblique with few simple setae on the posterior distal corner; dactylus claw-like, with denticles in comb-scales and one plumose seta dorsally.

Gnathopod 2 ( Fig. 34View FIGURES 33 – 34) subchelate; coxal plate wider than long; basis, ischium and merus with simple setae and comb-scales on the disto-posterior margin; carpus wider than long, posterior lobe elongated with polygonal pattern, with pectinate border, one row of serrate setae and one row of denticles in comb-scales, disto-anterior margin with serrate setae; propodus ovate, longer than wide, propodus length 1.4 times width, posterior margin of lobe covered by denticles in comb-scales and with one strong cuspidate setae; palm smooth, longer than posterior margin of propodus, slope oblique, margin convex with several simple setae, posterior distal corner with a cup for dactylus; dactylus claw-like, reaching lobe of propodus, with one plumose seta dorsally, without comb-scales.

Pereopods 3 to 7 ( Figs. 35–39View FIGURES 35 – 39) simple, with several simple setae on border; ischium, merus, carpus and propodus posterior margin with cluster of simple and cuspidate setae; dactylus less than half length of propodus, unguiform; pereopod 3 and 4 with similar sizes; pereopod 5 smaller than others; pereopod 6 smaller than pereopod 7.

Pleopods ( Fig. 40View FIGURES 40 – 44) peduncle shorter than rami, with two coupling spines; both rami with long plumose setae.

Uropod 1 ( Fig. 41View FIGURES 40 – 44) peduncle 1.3 times longer than rami, with four cuspidate setae dorsally; inner ramus longer than outer ramus; inner ramus with three dorsal cuspidate setae, male with one long curved seta followed by three small cuspidate setae, four cuspidate setae apically (two of them longer than others); outer ramus with four dorsal cuspidate setae and three cuspidate setae apically.

Uropod 2 ( Fig. 42View FIGURES 40 – 44) shorter than uropod 1; peduncle rectangular as long as rami, with two cuspidate setae dorsally; inner ramus slightly longer than outer ramus, with three dorsal cuspidate setae and apex with seven cuspidate setae and one row of four short cuspidate setae; outer ramus with three cuspidate seta dorsally and apex with four cuspidate setae.

Uropod 3 ( Fig. 43View FIGURES 40 – 44) shorter than other uropods; peduncle longer than wide, wider than ramus, with six cuspidate setae apically; inner ramus absent; outer ramus uniarticulate, sub-equal to peduncle, with eight simple setae apically (two of them shorter than others).

Telson ( Fig. 44View FIGURES 40 – 44) entire, apically rounded, as wide as long, with six cuspidate setae apically distributed in three clusters of two setae each, six plumose setae laterally.

Coxal gills sac-like present on pereonites 2 to 6 and sternal gills tubular on pereonites 2 to 7.

Female. Mean body length: 5.52 ± 1.40 mm, mean head length: 0.59 ± 0.15 mm (n=20). Antenna 1 flagellum with 10 articles. Antenna 2 with 13 articles. Gnathopod 1 ( Fig. 45View FIGURES 45 – 46) similar to male gnathopod 1; carpus longer than wide, posterior lobe margin with polygonal pattern and with serrate setae and denticles in comb-scales on the margin, and ventral face with three serrate setae; propodus longer than wide, hammer-shaped, inner face with six serrate setae and some simple setae, anterior and posterior distal margins with comb-scales; dactylus with combscales and one plumose seta. Gnathopod 2 ( Fig. 46View FIGURES 45 – 46) similar in size to gnathopod 1, but the propodus of gnathopod 2 is longer than gnathopod 1; different to male gnathopod 2 in shape and smaller; carpus longer than wide, posterior lobe with polygonal pattern and denticles in comb-scales, one row of serrate setae on margin, anterior distal margin with few simple setae, and ventral face with two serrate setae; propodus rectangular, longer than wide, inner face with four serrate setae and few simple setae, palm transverse, posterior distal corner with one strong cuspidate seta, posterior and anterior distal margins with comb-scales; dactylus with comb-scales and one plumose seta. Telson similar in shape to male, but with four cuspidate setae and six plumose setae laterally.

Habitat. Freshwater, epigean. Hyalella gauchensis  was found in an artificial pond of shallow depth (around 30 cm) ( Fig. 48View FIGURES 47 – 48). The pond presented a large amount of macrophytes of the genus Salvinia  , which were used as shelter for the specimens of H. gauchensis  .

Conservation. Hyalella gauchensis  occurs in an artificial pond that was built by the residents of the property for fish farming. To build the pond, the residents use the water from the spring where H. georginae  inhabits. In the surroundings of the pond, there is no cultivation of any type of crops, which could be considered a threat to H. gauchensis  , as the pesticides used in these cultures can be harmful to the amphipods. However, as this is an artificial pond, it is under the risk of drying out, in the case of the residents interrupt the water flow coming from the spring, which may cause the local extinction of the population of H. gauchensis  .

Etymology. The species epithet " gauchensis  " is related to the Portuguese word "gaúcho", which means the native people or the residents of the state of Rio Grande do Sul, Brazil.

Remarks. Using the taxonomic key of Rodrigues et al. (2014), we observed that H. gauchensis  differs from the other species of the genus in Brazil. As H. georginae  , Hyalella gauchensis  resembles to H. montenegrinae  , H. curvispina  , H. castroi  , H. pseudoazteca  , H. kaingang  , H. pleoacuta  , H. carstica  and H. xakriaba  by present a curved seta on the inner ramus of uropod 1 of the males. Hyalella gauchensis  is different from H. pleoacuta  , H. kaingang  and H. pseudoazteca  by lacking dorsal flanges on pereions and pleonites. The new species differs from H. montenegrinae  , H. curvispina  , H. castroi  , H. carstica  and H. xakriaba  in the type and number of setae on uropods, telson and inner face of gnathopod 1, as well as the shape and size of ganthopod 2 propodus. Hyalella georginae  and H. gauchensis  differ from each other in the number of serrate setae on the inner face of gnathopod 1, in the shape of gnathopod 2 propodus, in the number of setae on antenna 2, in the size of the plumose setae on pleopods and in the type and number of setae on uropods and telson.

MNRJ

Museu Nacional/Universidade Federal de Rio de Janeiro