Hyalella marysolae, Marrón-Becerra & Hermoso-Salazar & Ayón-Parente, 2023

Marrón-Becerra, Aurora, Hermoso-Salazar, Ana Margarita & Ayón-Parente, Manuel, 2023, Description of two new epigean species of the genus Hyalella S. I. Smith, 1874 (Crustacea: Amphipoda: Hyalellidae) from Jalisco, Mexico, Nauplius (e 2023010) 31, pp. 1-22 : 3-11

publication ID	https://doi.org/ 10.1590/2358-2936e2023010
publication LSID	lsid:zoobank.org:pub:601BE1CA-7CC6-428E-93D2-22E2A7749CFA
DOI	https://doi.org/10.5281/zenodo.10955599
persistent identifier	https://treatment.plazi.org/id/03E61C56-FFAD-FF95-FEAE-FA2EFCAEF93B
treatment provided by	Felipe
scientific name	Hyalella marysolae
status	sp. nov.

Treatment

Hyalella marysolae sp. nov.

( Figs. 2−6 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 )

http://zoobank.org/ urn:lsid:zoobank.org:act:68D260B8-6FD1-4440-9156-1CBB0BE15FF0

Etymology. This species is named in honor of Montserrat Marysol Ayón, the beloved daughter of the third author.

Type material. Holotype: male, body size 4.8 mm, cephalothorax size 0.49 mm ( CNCR 35778 ), from El Tajo stream ( Fig. 1A, B View Figure 1 ), in Teuchitlán, state of Jalisco, Mexico (20°40’40.49”N 103°52’13.4”W), 6 April 2018, 1,265 m.a.s.l., temperature 25.5 °C, pH 6.8, associated with roots of Pistia stratiotes Linnaeus, 1753 , A. Marrón-Becerra, M. Ayón-Parente, and M. Hermoso-Salazar collectors GoogleMaps . Paratypes (30 males, 30 females): males mean body size 3.9 ± 0.4 mm, mean cephalothorax length 0.39 ± 0.06 mm (n = 27), GoogleMaps female mean body size 4.8 ± 0.6 mm, cephalothorax length 0.55 ± 0.12 mm (n = 30) (permanent slides CNCR 35779, GoogleMaps male paratypes CNCR 357780, and female paratypes CNCR 35781), collected from the same locality as the holotype GoogleMaps .

Diagnosis. Pleonites 1−2 with short dorsoposterior carina. Coxa 4 excavated posteriorly.Eyes pigmented, black. Antenna 1 shorter than antenna 2 without accessory f lagellum. Antenna 2 less than half of body length, almost reaching seventh pereonite. Maxilla 1 palp short, reaching less than half of length between base of palp and tip of setae of outer plate, with 1 short stout distal seta and with setules; inner plate slender with 2−3 strong pappose apical setae. Maxilla 2 inner plate with 2 strong pappose setae on inner margin, simple setae and serrate setae on distal margin. Gnathopod 1 propodus hammer-shaped, palm with transverse slope, inner face with 2−5 serrate setae, comb scales on distoposterior and distoanterior border, carpus inner face lobe with 5 serrate setae. Gnathopod 2 basis posterior margin with 1 slender seta, merus without medial seta, palm with wide excavation. Uropod 1 male inner ramus without curved setae. Uropod 3, ramus slightly longer than peduncle, styliform and with 4 cuspidate setae of variable length. Telson as long as wide or wider, distal margin rounded or truncated with 2 long widely separated simple setae. Sternal gills on segments 3−7.

Description of males based on holotype ( CNCR 35778) and paratypes. Body, pleonites 1−2 with short dorsoposterior carina ( Fig. 2A View Figure 2 ). Epimeral plates 1−3 slightly acuminate. Coxae 1−3 ( Fig. 2A View Figure 2 ) subequal in shape, subrectangular, longer than wide; coxa 1 shorter than coxae 2−3. Coxa 4 wider than coxae 1−3, with deep posterior excavation; coxae 1−4 slightly overlapping anterior coxa, distal margin rounded with small setae widely separated, acumination absent. Coxae 5−7 reduced, shorter than coxae 1−4, bilobate (except coxa 7), lobe of basis overlapping posterior lobe of coxa, except coxa 7; coxa 5 with 2 subequal lobes, anterior lobe slightly shorter than posterior, overlapping coxae 4 and 6; coxa 6 with 2 unequal lobes, anterior lobe reduced; coxa 7 with 1 single lobe, anterior lobe absent.

Head typically gammaridean ( Fig. 2A View Figure 2 ), with smooth surface, total length less than the combined length of the first 2 pereonites, reaching half of second pereonite, rostrum absent. Eyes pigmented, medium, rounded, and black, located between the insertions of antennae 1 and 2.

Antenna 1 ( Fig. 2A, B View Figure 2 ) less than half body length, about 75% the length of antenna 2, but longer than peduncle of antenna 2, almost reaching half of fifth pereonite; peduncle longer than head, reaching one-third of first pereonite, article 1 and 2 subequal in length, article 1 wider than articles 2−3, article 2 longer and wider than article 3, article 3 shorter and thinner than articles 1−2 (proportions 1.6:1.3:1), article 1 with 1 medial short cuspidate seta, and 1 cluster with 3 cuspidate setae (one shorter) at distal end; flagellum with 12 articles reduced gradually towards distal portion, flagellum longer than peduncle; 1 pair of aesthetascs on articles 4−11; accessory flagellum absent. Antenna 2 ( Fig. 2A, C View Figure 2 ) almost 1.4 times longer than antenna 1, almost half of total body length, almost reaching seventh pereonite; peduncle almost reaching middle of third pereonite, articles gradually increasing in length and decreasing in width, article 5 longer than article4 (about 1.5 times); flagellum with 15 articles, longer than peduncle (about 1.5 times); flagellum without aesthetascs.

Mouthparts: upper lip ( Fig. 3A View Figure 3 ) distal margin rounded, with numerous setules, being longer and more distant towards lateral end. Lower lip ( Fig. 3B View Figure 3 ) subquadrate, outer lobes without notches or excavations; mandibular projection of outer lobes rounded; without inner lobes.

Left and right mandibles ( Fig. 3C, D View Figure 3 ) without palp, asymmetric. Incisor with 6 teeth. Left lacinia mobilis similar to incisor process, with 5 teeth; setal row on left mandible with 3 main pappose setae plus accessory setae. Right lacinia mobilis more reduced than left, with 2 pairs of asymmetric L-shaped teeth, fused at base, proximal pair longer than distal, inner margin denticulate; near lacinia mobilis base with setules on inner margin; setal row on right mandible with 2 main pappose setae plus accessory setae and with setulae near molar process. Molar process large, cylindrical, and triturative; accessory pappose setae present in both molars.

Maxilla 1 ( Fig. 3E, F View Figure 3 ) palp short, vestigial, uniarticulated, longer than wide, distally pointed with 1 short stout distal seta, reaching less than half of palp length, palp length less than half distance between base of palp and base of seta on outer plate; inner plate slender, shorter than outer plate, with 2−3 pappose apical setae; outer plate with 9 apical stout serrate setae and with setules.

Maxilla2 ( Fig.3G View Figure 3 ) plates subequal in length, width, and shape; inner plate shorter and slightly slender, with 2 pappose setae on mid-distal margin, and with 5 long serrulate setae on distal margin; outer and inner plates with large simple distal setae (type A2) and abundant setules on both distal surfaces and margins.

Maxilliped ( Fig. 3H View Figure 3 ) inner plate lobe longer than outer plate lobe; distal margin slightly convex; inner plate distal margin with 3 cuspidate setae of equal size and with plumose setae, inner margin with several pappose setae; outer plate, inner and distal margins with numerous simple setae.Palp composed of 4articles subequal in maximum length; first article with 3−4 simple setae at inner distal end and 2setae at outer distal end;second article with numerous simple setae on inner margin and 2−3 at outer distal end; third article with several setae on distal margin, distal end on outer margin with 4−7 simple setae and comb scales, inner margin with at least 8 setae and 6 at distal end; fourth article unguiform, slightly longer than nail, with comb scales, inner margin with 4 setae near distal half, outer margin with 1seta near nail base; nail overreaching two-thirds of fourth article in length, with serration on distal half.

Gnathopod 1 ( Fig. 4A View Figure 4 ) subchelate, propodus hammer-shaped, shorter than gnathopod 2. Basis elongated, maximum length 3−3.5 times longer than maximum width; medial seta absent, posterior distal end with cluster of 2 setae.Ischium short, subquadrate, longer than wide, length almost same as maximum width of basis and maximum length of merus; distal posterior end with 1 cluster of 2 setae. Merus longer than wide, almost at midway of posterior margin with comb scales; almost at distal margin with 3−8 setae. Carpus longer than wide, slightly longer and wider than propodus, with strong, short, and wide posterior lobe forming 1 scoop-like structure open to inside; mesial surface of lobe with 2−5 serrate setae, outer surface on distal half of lobe, near margin, with comb scales and serrate setae (10), anterior distal end with 7−9 simple setae. Propodus maximum length almost 1.5 times longer than wide; inner surface near distal margin with 3−5 serrate setae in 1 row; distal anterior end with 2 clusters of approximately 5 setae;distal half of anterior and posterior surfaces with comb scales; posterior margin with 1 medial seta; palm transverse, posterior distal end with 1 robust seta and cup for dactyl. Dactyl claw-like; nail present; anterior surface near proximal third with 1 plumose seta, with comb scales on anterior surface.

Gnathopod 2 ( Fig. 4B View Figure 4 ) subchelate. Basis elongate, 4 times longer than wide; posterior margin with 1 slender seta. Ischium short, subquadrate, as long as merus. Merus short; distal end of posterior margin with 4 simple setae, medial setae absent; distal end with comb scales. Carpus shorter than propodus, length similar to merus maximum length, slightly exceeding 1.5 times the width of merus; anterodistal end with 1−3 simple setae; posterior lobe scoop-like, elongate, almost 1.5 times width of merus, with several submarginal pappose setae and comb scales.Propodus robust, ovate, 1.5 times longer than maximum width; palm oblique, shorter than posterior margin; slope slightly irregular, with several long simple setae, few short and medium setae; distal margin of palm with 1 truncated process near insertion of dactyl and with presence of 1 wide posterior excavation at base; palm posterior distal end with 2 robust setae, comb scales, and cup for dactyl. Cup for dactyl as long as space between the inner end of cup and truncated process. Dactyl claw−like, congruent with palm, occupying less than half of cup of dactyl without comb scales; outer margin proximal third with 1 plumose seta; inner margin slightly crenulated with separated setules.

Pereopods 3−7 ( Fig. 5A, F View Figure 5 ) simple, gradually expanding posteriorly. Pereopod5 shorter than6 and7.

Pereopod 3 ( Fig. 5A View Figure 5 ), basis elongate; posterior margin with1simple seta;anterodistal and posterodistal end ing with simple setae. Ischium subquadrate; posterodistal end with one pair of setae. Merus longer than ischium (almost 2.5 times maximum length); anterior margin with 1 robust seta; posterior margin with 5 slender simple setae (2 clusters of 2 setae plus 1 separated seta); anterodistal and posterodistal ends with 1 cluster of 4 slender setae, anterodistal end with 1 robust seta. Carpus shorter and more slender than merus; posterior margin with 4−5 stout setae plus accessory setae; posterodistal end with at least 2 slender setae; anterodistal end with at least 2−3 setae. Propodus shorter than anterior margin of merus, more slender than carpus; posterior margin with 5−6 stout setae plus accessory seta; anterodistal end with 3−5 simple setae.Dactyl claw-like, length more than half of propodus; nail present; first proximal third of anterior margin with 1 plumose seta; anterior and posterior margins with 1 simple seta near base of nail.

Pereopod 4 ( Fig. 5B View Figure 5 ) similar in shape to pereopod 3 but slightly longer; coxa 4 wider than coxa 3 with posterior excavation; basis posterior margin with 1 simple seta; propodus posterior margin with 5 setae. Pereopods 5−7 ( Fig.5C, E View Figure 5 ) similar in shape; basis posterior lobe rounded and denticulated.

Pereopod 7 ( Fig. 5F View Figure 5 ) basis lobe widely expanded posteriorly, overreaching ischium distal margin; wider than lobes of pereopods 5 and 6; basis lobe, width almost 2.2 times as wide as basis (measured at cleft between basis and basis lobe); posterior margin with 10−11 serrations, each with 1 setule, without stout seta on distal margin; anterior margin with3 stout setae and 1 at distal end. Dactyl length less than half of propodus.

Pleopods1−3similar in size and shape,not modified, biramous, elongated, ramus longer than peduncle, rami multi−annulated, with numerous plumose setae. Pleopod 1 ( Fig. 5F View Figure 5 ) inner margin of peduncle distal end with 2 short retinacula (coupling hooks).

Uropod 1 ( Fig. 6A View Figure 6 ) longer than uropod 2 ( Fig. 6B View Figure 6 ); peduncle longer than rami, proximal half of dorsal margin with 2 dorsal cuspidate setae, distal cuspidate seta with accessory seta (type B6), inner and outer distal ends with 1 cuspidate seta; rami subequal, inner ramus slightly longer, with two dorsal and 3−4 distal cuspidate setae, outer ramus with three dorsal cuspidate setae type B6 and 4−5 distal setae; male without curved setae on inner ramus.

Uropod2 ( Fig. 6B View Figure 6 ) longer than peduncle of uropod 1; peduncle as long as rami or slightly shorter, with 2 dorsal cuspidate setae on distal half and 1 cuspidate seta at distal end; rami subequal, inner ramus slightly longer with 2 dorsal and 3 distal cuspidate setae, outer ramus with 3−5 dorsal cuspidate setae, proximal seta with accessory seta (type B6), and up to 4 distal setae.

Uropod 3 ( Fig. 6C View Figure 6 ) slightly longer than peduncle of uropod 2; peduncle subrectangular, wider than ramus with 4 robust distal cuspidate setae of variable length (1 with accessory seta, type B6); inner ramus absent, outer ramus uni-articulate, slender, slightly longer than peduncle, about 2 times length of the larger seta of peduncle, basal width about 2 times apex width of ramus, with 3−7 slender apical simple setae and 1 connate seta.

Telson ( Fig. 6D View Figure 6 ) entire, as long as wide or wider than long, distal margin rounded or truncated with 2 long simple setae widely separated; dorsal surface bearing 2 clusters of 3 plumose setae near middle distal portion, near lateral margin,symmetrically distributed.

Coxal gills sac-like, present on segments 2−6. Sternal gills tubular, present on segments 3−7.

Description of paratypes females. Females mean body size 4.8 ± 0.6 mm, cephalothorax length 0.55 ± 0.12 mm. Gnathopod 1 ( Fig. 4C View Figure 4 ), carpus with 5 setae on inner face lobe; propodus with a row of 5 setae on inner face. Gnathopod 2 ( Fig. 4D View Figure 4 ) smaller than male gnathopod 2, parachelate; palm reverse oblique. Basis posterior margin with 1 seta. Propodus 2.6 longer than maximum width; outer face with 2 setae in 1 row and 2 large setae near palm, with 3 medial setae on mid-posterior surface; anterior and posterior distal half with comb scales. Pereonite 2 with 1 anterior excavation or notch for amplexus. Pereopod 7 lobe with 11 serrations and setules, without stout setae on distal margin. Oostegites subtriangular, with curled setae on margins, almost reaching half of length of merus. Telson similar in shape to male.

Intraspecific variation. The number of articles in the flagellum of antennae 1−2 is variable, increasing proportionally with body size. The length of antenna 2 can posteriorly reach one-third of the sixth pereonite or almost reach the seventh. The length of the f lagellum of antenna 2 varies from 1.3 to 1.5 times as long as the peduncle. The palp of maxilla 1 can be different between individuals or even between right and left side on the same individual, from one third to more than half of the length from the base of palp to the base of setae on the outer plate. Also, the number of setae on the inner plate of maxilla 1 can be 2−3. The number of setae in the first and third article of maxilliped is variable. The basis of the first gnathopod can be 3−3.5 times as long as wide. Some individuals bear an extra robust medial cuspidate seta on the peduncle of uropod 3, like in Hyalella wakulla wakulla ( Drumm and Knight-Gray, 2019) . Moreover, the distal margin of the telson varies from rounded to truncated.

Remarks. Hyalella marysolae sp. nov. exhibits two short dorsal projections or carinae on pleonites 1−2, barely visible, this characteristic is also in H. azteca , H. cenotensis , H. maya , H. tepehuana , and H. wakulla from North America, and it is not in the species from South America but, unlike H. marysolae sp. nov., in the species from North America the projections or carinae are evident. The presence or absence of projections or carinae was long considered a crucial feature to distinguish the species of the genus. The most morphologically similar species to H. marysolae sp. nov. is H. morronei sp. nov., despite the absence of projections or carinae in this last species (described below). Both species share characters, such as: the number of articles in the antennae 2 (more than 13), the relative length of antennae 2 and the body, and the form of the eyes that distinguish them from the other species from Mexico ( Tab. 1 View Table 1 ). Nevertheless, several differences can be observed between both species, for example: H. marysolae sp. nov., the palp of maxilla 1 presents setules; the length of the head relative to the second pereonite is smaller in H. marysolae sp. nov. than in H. morronei sp. nov.; H. marysolae sp. nov. has one pair of aesthetascs on the articles 4−11 of the f lagellum of antenna 1, while H. morronei sp. nov. has one aesthetasc on articles 1, 5, 8, 9 and one pair on articles 6−7; in H. marysolae sp. nov., the propodus of the gnathopod 1 is hammer-shaped, while in H. morronei sp. nov. it is hatchet-shaped; the propodus maximum length relative to the width of gnathopod 1 is greater in H. marysolae sp. nov. than in H. morronei sp. nov. (1.5× vs. 1.25×, respectively); and the telson is wider than long in H. marysolae sp. nov. and longer than wider in H. morronei sp. nov. ( Tab. 1 View Table 1 ).

Type locality. El Tajo stream, Teuchitlán ( Fig. 1A, B View Figure 1 ), state of Jalisco, Mexico (20°40’40.49”N 103°52’13.40”W) GoogleMaps .

Habitat and conservation. This species was collected near the sediment and in the roots of macrophytes in the littoral zone. It is important to mention that the habitat of this species is threatened by anthropogenic activities. Water is regularly extracted from the El Tajo stream to maintain surrounding crops of corn and sugarcane.This process generates runoff of herbicides and chemicals (urea) into the stream (M.A.-P., pers. observation).