Hyalella cheyennis, Bueno & Oliveira & Wellborn, 2019

Bueno, Alessandra Angélica De Pádua, Oliveira, Kevin Martins & Wellborn, Gary, 2019, A new species of Hyalella Smith, 1874 (Crustacea: Amphipoda: Hyalellidae) from Oklahoma, USA, Zootaxa 4700 (2), pp. 259-269 : 260-268

Hyalella cheyennis n. sp.

( Figs 1–6 )

Type material. HOLOTYPE: Holotype male, body length = 5.54 mm, head length = 0.54 mm, Rutherford Spring , small spring, near the town of Connerville, Oklahoma, USA (34 o 3’17.14”N 96 o 32’54.10”W), MZUSP 39432 , March /2007, Wellborn coll. PARATYPES: female, same collection data of the holotype, MZUSP 39433 . 10 females , two males, same collection data of the holotype, CCUFLA 406 .

Diagnosis. Body surface smooth. Eyes round, pigmented. Antenna 1 shorter than antenna 2. Antenna 2 more than half body length. Maxilla 1 palp longer than wide, reaching less than half the distance between base of palp and tip of setae on outer plate; inner plate slender, with two strong pappose apical setae. Maxilla 2 inner and outer plate with some serrate setae. Gnathopod 1 propodus longer than wide, hammer-shaped, inner face with one row of three–four pappose setae, anterior and posterior margins with comb-scales. Gnathopod 2 propodus ovate, palm shorter than posterior margin of propodus, posterior margin with comb-scales, slope oblique. Uropod 1 of male without curved seta on inner ramus. Uropod 3 peduncle wider and longer than rami, with three–four distal cuspidate setae with accessory seta, ramus with four simple setae and one cuspidate seta apically. Telson wider than long, apically rounded with two apical simple setae. Coxal gills sac-like present on segments 2 to 6. Sternal gills present on segments 3 to 7.

Description of male. Mean body length: 3.47 ± 0.79 mm, mean head length: 0.40 ± 0.11 mm (n = 6). Body surface smooth. Epimeral plates slightly acuminate. Coxae one to four subequal in size and shape, slightly overlapping. Coxa 1 similar to 2 and 3. Coxa 3 narrower than 4. Coxa 4 deeper than wide, excavated posteriorly. Coxa 5 posterior lobe deeper than anterior lobe. Coxa 6 anterior lobe small. Coxa 7 reduced. Head smaller than first two thoracic segments. Eyes round and pigmented.

Antenna 1 less than half body length, shorter than antenna 2, longer than peduncle of antenna 2; peduncle slightly shorter than head; article 1 longer than 2, article 3 shorter than 1, and the same length as article 2; flagellum with nine articles, longer than peduncle; aesthetascs occurring on flagellum from the articles 3 to 6 distally.

Antenna 2 more than half body length; peduncle slender, longer than head, article 1 shorter than article 4; flagellum with 13 articles, longer than peduncle.

Basic amphipodan mandible, without palp; incisor toothed; left lacinia mobilis with five teeth; with setal row with three to four pappose setae with accessory seta; right mandible with four papposerrate setae; molar process broad and cylindrical.

Upper lip margin rounded; distal border covered by setules on ventral and dorsal faces. Lower lip outer lobes rounded and distally notched, with setules on dorsal and ventral faces.

Maxilla 1 inner plate slender, shorter than outer plate, with two long pappose apical setae presenting long setules; outer plate with eight–nine serrate setae. Palp short, uniarticulate, longer than wide reaching less than half the distance between base of palp and tip of setae on outer plate.

Maxilla 2 inner and outer plates subequal in width, inner plate with two papposerrate setae, three serrate setae and several simple setae; outer plate with several simple distal setae, two serrate setae and two pappose setae; inner and outer plates covered by a few setules.

Maxilliped inner plate longer than wide, with six pappose setae, three cuspidate setae and eight pappose apical setae; outer plate similar in width to inner plate, with two pappose setae and several simple setae on the margin; palp as the same size as inner plate and longer than outer plate, four articles, article 1 longer than wide, outer margin with simple setae; article 2 longer than wide, inner margin with several long simple setae; article 3 longer than wide, outer and inner margins with several long simple setae and two serrate setae; dactylus unguiform, shorter than third article, distal setae simple and shorter than nail, distal nail present.

Gnathopod 1 subchelate; coxal plate longer than wide with simple setae on the margin; basis and ischium with simple setae distoventrally; merus with simple setae, carpus longer than wide, similar in length to propodus, with lateral distal lobe produced and forming a scoop-like structure, margin with several pappose setae; propodus width about 1/2 of maximum length, hammer-shaped, with few simple long setae on disto-anterior margin, comb-scales in anterior and posterior margin; palm slope transverse, margin slight convex, palm with many simple setae, posterior distal corner with one strong cuspidate seta with an accessory seta; dactylus claw-like, comb-scales on distal margin.

Gnathopod 2 subchelate; coxal plate longer than wide, with simple setae on the margin; basis with few simple setae on posterior margin; merus with six simple setae on posterior margin; carpus wider than long, posterior lobe slim produced between merus and propodus, margin with comb-scales and several pappose setae; propodus ovate, longer than wide, posterior margin with comb-scales; palm shorter than posterior margin of propodus, slope oblique, with one row of several simple setae and some with accessory setae; posterior distal corner with two long and strong cuspidate setae with an accessory setae and with a cup for dactylus; dactylus claw-like, congruent with palm, combscales absent.

Peraeopods 3 to 7 simple. Peraeopods 3 and 4 merus and carpus posterior margin with clusters of simple setae; propodus posterior margin of peraeopod 3 and 4 with simple setae, some with accessory setae; dactylus less than half-length of propodus. Peraeopods 5 to 7 merus, carpus and propodus posterior margin with 10–11 marginal clusters of 1–6 simple setae, some with an accessory seta, dactylus less than half-length of propodus; Peraeopod 7 with three stout simple setae on the ventral margin of the posterior lobe. Peraeopod 3 and peraeopod 4 similar sizes; peraeopod 5 smaller than others; peraeopod 6 smaller than peraeopod 7, which is about 1.2 times longer than peraeopod 3.

Pleopods peduncle shorter than rami, with two coupling spines; both rami with several plumose setae.

Uropod 1 longer than uropod 2; peduncle longer the rami, with six cuspidate setae with accessory seta; rami subequal; inner ramus with one dorsal cuspidate seta with an accessory seta on the margin and two to three cuspidate setae with an accessory seta apically; male without curved seta; outer ramus with two dorsal cuspidate setae with an accessory seta on the margin and two to three cuspidate setae with an accessory seta apically.

Uropod 2 shorter than uropod 1, peduncle wider than rami, with five cuspidate setae with an accessory seta; inner ramus with two dorsal cuspidate setae with an accessory seta and five cuspidate setae with accessory seta apically; outer ramus with two dorsal cuspidate setae and one of them with an accessory seta and four distal cuspidate setae.

Uropod 3 shorter than peduncle of uropod 1 and peduncle of uropod 2; peduncle longer than wide, with three to four cuspidate setae; inner ramus absent; outer ramus uniarticulate; ramus shorter than peduncle; basal width more than twice apex of ramus, with four simple setae and one cuspidate seta apically.

Telson entire, wider than long, apically rounded, with two apical simple setae.

Coxal gills sac-like, present on pereonites 2 to 6. Sternal gills tubular present on pereonites 3 to 7.

Female. Mean body length 3.25 ± 0.39 mm, mean head length 0.39 ± 0.05 mm (n = 10). Gnathopod 1 similar to male gnathopod 1; carpus longer than wide, with comb-scales; with posterior lobe produced and forming a scooplike structure, with pectinate margin, with several pappose setae; propodus longer than wide, hammer-shaped, palm shorter than posterior margin of propodus, with comb-scales, inner margin with four pappose setae and three simple setae, palm slope transverse, dactylus claw-like. Gnathopod 2 similar in size and shape to gnathopod 1; different in shape to male gnathopod 2 and smaller; propodus longer than wide, subchelate, inner margin with five simple setae, palm transverse with few long simple setae, with comb-scales. Telson similar in shape to male.

Etymology. The specific epithet “cheyennis” was selected to honor the Southern Cheyenne Indian tribe which inhabited the region.

Habitat. Freshwater, epigean.

Remarks. The description of this new species of Hyalella increases to 15 the number of species of the genus for the USA. The new species is known only from a single freshwater spring in the state of Oklahoma, which is in the Center-South region of the country.

Hyalella cheyennis n. sp. presents serrate setae in the maxilla 2, a feature that is not found in any of the 14 species that occur in North America and the Caribbean. This characteristic cannot be compared with H. inermis , because its description is poor in detail and has poor quality figures. However, when analyzing the gnathopod 1 and 2, it is possible to observe that H. cheyennis n. sp. differs from H. inermis in the shape of the gnathopod 1 and 2, and number and type setae present in the posterior margin and palm of propodus of gnathopod 2 ( Smith 1875).

Hyalella cheyennis n. sp. differs from H. cenotensis and H. muerta because it is not a troglobitic species ( Baldinger et al. 2000; Marrón-Becerra et al. 2014). The new species described here is found in an epigean environment, with eyes present and without troglomorphic characteristics, such as reduced or absent eyes and longer appendages.

Because it does not have flanges on the surface of the body, it is also possible to differentiate Hyalella cheyennis n. sp. from the ten known epigeal species ( H. montezuma , H. texana , H. azteca , H. spinicauda , H. wellborni , H. maya , H. wakulla ) ( Soucek et al. 2015; Marrón-Becerra et al. 2018, Drumm & Knight-Gray 2019). However, it is not possible to use this criterion for H. squamosa , since it has a very old description and precarious information. However, H. cheyennis n. sp. differs from H. squamosa because it does not present comb-scales in the carpus of gnathopod 1 and gnathopod 2 ( Mateus & Mateus 1987).

Of the epigeal species that do not present flanges ( H. meraspinosa , H. caribbeana , H. sandra , H. longicornis ) H. cheyennis n. sp. presents other characteristics that differ from them ( Soucek et al. 2015). When compared to H. meraspinosa , H. cheyennis n. sp. is differentiated by having the palm of the propodus of gnathopod 2 equivalent in size to the distal-posterior margin of the propodus, which is not observed in H. meraspinosa , where the palm is larger than the margin ( Baldinger 2004).

Hyalella cheyennis n. sp. differs from H. caribbeana and H. longicornis because it presents coxal gills in segments 2 to 6. In relation to H. longicornis , H. cheyennis n. sp. also differs by the size of the palm of the gnathopod 2 in relation to the distal-posterior margin of the propodus, where H. longicornis presents the palm smaller than the margin ( Bousfield 1996).

Hyalella cheyennis n. sp. differs from H. sandra because it presents differences both in the form and in the number of apical setae of the ramus of the uropod 3, the telson is wider than long and presents a difference in the number of setae ( Baldinger et al. 2000).

The diversity of the genus Hyalella in North America has increased when the populations of complex H. azteca are studied with more details ( Drumm & Knight-Gray 2019, Soucek et al. 2015, and this manuscript). Thus, it is necessary to review all species of the complex with molecular and morphological analyses, and if possible, to review the old descriptions (as H. inermis ). It is important to document the full diversity of Hyalella , and to consider conservation measures to protect species, like H. cheyennis , endemic to a single location.

Figures

FIGURE1. Hyalella cheyennisn.sp.,Rutherford Spring, OklahomaCity, OklahomaState, USA(34o3’17.14”N 96o32’54.10”W). Holotype, male, 5.54 mm, MZUSP 39432; paratype, female, 4.52 mm, MZUSP 39433. Scale bars: 1 mm.

FIGURE2. Hyalella cheyennisn.sp.,Rutherford Spring, OklahomaCity, OklahomaState, USA(34o3’17.14”N 96o32’54.10”W). Paratype, male, 4.4 mm. Scale bars: 0.2 mm.

FIGURE3. Hyalella cheyennisn.sp.,Rutherford Spring, OklahomaCity, OklahomaState, USA(34o3’17.14”N 96o32’54.10”W). Paratype, male, 4.4 mm. Scale bars: 0.2 mm.

FIGURE4. Hyalella cheyennisn.sp.,Rutherford Spring, OklahomaCity, OklahomaState, USA(34o3’17.14”N 96o32’54.10”W). Paratype, male, 4.4 mm. Scale bars: 0.2 mm.

FIGURE5. Hyalella cheyennisn.sp.,Rutherford Spring, OklahomaCity, OklahomaState, USA(34o3’17.14”N 96o32’54.10”W). Paratype, male, 4.4 mm. Scale bars: 0.2 mm.

FIGURE6. Hyalella cheyennisn.sp.,Rutherford Spring, OklahomaCity, OklahomaState, USA(34o3’17.14”N 96o32’54.10”W). Paratype, female, 4.52 mm. Scale bars: 0.2 mm.