Research Article |
Corresponding author: Aurora Marrón-Becerra ( auro13@hotmail.com ) Academic editor: Tammy Horton
© 2020 Aurora Marrón-Becerra, Margarita Hermoso-Salazar, Gerardo Rivas.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Marrón-Becerra A, Hermoso-Salazar M, Rivas G (2020) A new species of the genus Hyalella (Crustacea, Amphipoda) from northern Mexico. ZooKeys 942: 1-19. https://doi.org/10.3897/zookeys.942.50399
|
A new species, Hyalella tepehuana sp. nov., is described from Durango state, Mexico, a region where studies on Hyalella have been few. This species differs from most species of the North and South American genus Hyalella in the number of setae on the inner plate of maxilla 1 and maxilla 2, characters it shares with Hyalella faxoni Stebbing, 1903. Nevertheless, H. faxoni, from the Volcan Barva in Costa Rica, lacks a dorsal process on pereionites 1 and 2. Also, this new species differs from other described Hyalella species in Mexico by the shape of the palp on maxilla 1, the number of setae on the uropods, and the shape of the telson.
Durango, freshwater amphipod, Nearctic region, scud, taxonomy
Mexico is in the transition zone between two biogeographic regions: the Nearctic and the Neotropical regions. In the Neotropical region, the genus has been found to be highly diverse, with three species in Mexico, three species in the Caribbean region, two species in Central America, and more than 60 species in South America (
The material was collected using a net with fine, 250 µm mesh on aquatic vegetation in the Tunal River in Durango state, Mexico (Fig.
The body parts of the collected material were dissected and mounted: semi-permanent slides were mounted on glycerol, and permanent slides on Entellan, a synthetic resin. The terminology used for the setae follows that of
The type material was deposited in the Colección Nacional de Crustáceos (CNCR), Instituto de Biología, Universidad Nacional Autónoma de México (
Scanning electron micrographs were taken from paratypes (one female and one male) with a Hitachi SU1510 scanning electron microscope at the Laboratory of Microscopy and Photography of Biodiversity I, Instituto de Biología,
We compared our specimens with the lectotype and syntype material (now paralectotype) of Amphitoe aztecus, originally collected by
We present a key of the species from North America, Central America, and Caribbean region. However, Hyalella sapropelica Brehm, 1939 is excluded because the short description and incomplete drawings, make it is necessary to redescribe this species. In the key, we retain the subgenus Hyalella (Hyalella), proposed by
Family Hyalellidae Bulycheva, 1957
Genus Hyalella Smith, 1874
The specific epithet tepehuana refers to the great Tepehuan ethnic group, whose current settlement is in southern Durango. The name Tepehuan comes from Náhuatl and has two meanings: “owners of the hills”, tepetl (hill) and huan (possessive), and “winner of battles”, tepehuani.
Holotype male, body length 5.4 mm (CNCR 35295), from Tunal River in La Ferrería Durango, Mexico (23°57.905'N, 104°39.817'W) 12 June, 2016. Collectors: A. Marrón-Becerra and G. Rivas. Paratypes (n = 10 males, n = 10 females): males mean size 5.7 ± 0.6 mm, female body length 5.6 ± 0.6 mm (CNCR 35296, permanent slides and CNCR 35297 SEM preparations), same locality, date and collectors as holotype.
Pleonite 1 and 2 with dorsoposterior carina. Coxa 4 excavated posteriorly. Eyes pigmented. Antenna 1 shorter than Antenna 2 without accessory flagellum. Antenna 2 less than one-half body length. Maxilla 1 palp short, reaching less than half distance between base of palp and tip of setae of outer plate, with one stout distal seta; inner plate slender with three or four strong pappose distal setae. Maxilla 2 inner plate with two or three strong pappose setae on inner margin. Gnathopod 1, propodus hammer-shaped, palm slope transverse, inner face with three or four pappose setae, comb scales on distoposterior and distoanterior border. Gnathopod 2, basis hind margin with two setae. Uropods without curved setae. Uropod 3, peduncle and ramus subequal in length, styliform. Telson slightly longer than wide, narrowing posteriorly, with two long simple setae widely separated.
Body
, tergites of pleon 1 and 2 with dorsoposterior carina (Fig.
Mean body length of males: 5.7 ± 0.6 mm (n = 10).
Mean cephalothorax length: 0.6 ± 0.03 mm (n = 10).
Epimeral plates 1–3 acuminate.
Coxae 1–3
(Fig.
Head
typically gammaridean (Fig.
Antenna 1
(Figs
Antenna 2
(Figs
Buccal parts
: upper lip (Fig.
Lower lip (Figs
Mandibles
(Figs
Hyalella tepehuana sp. nov., male antennae A antenna 1 B antenna 2. Buccal parts C maxilla 1 D maxilla 2 E upper lip F lower lip G left mandible (dotted line shows the form and angle of molar in lateral view) H right mandible (dotted line shows the form and angle of molar in lateral view) I maxilliped. Scale bars: 100 µm.
Maxilla 1
(Figs
Maxilla 2
(Figs
Maxilliped
(Figs
Gnathopod 1
(Figs
Gnathopod 2
(Figs
Pereopods 3–7
(Figs
Pereopod 3
(Figs
Pereopod 4
(Figs
Pereopods 5–7
(Figs
Pleopods 1–3
(Fig.
Uropod 1
(Figs
Uropod 2
(Figs
Uropod 3
(Figs
Telson
(Figs
Coxal
gills sac-like, present on segments 2–6 (Fig.
Female (Fig.
Intraspecific variation: Maxilla 1, inner plate usually with four setae, the smaller adults could have three setae and the young ones two setae. Maxilla 1 palp, length quite variable during the molt process. Maxilla 2 inner plate with two or three setae, even in the same organism.
Freshwater, epigean.
La Ferrería, Durango, Tunal river (23°57.905'N, 104°39.817'W).
Hyalella tepehuana sp. nov. is the first species described from northern Mexico. It is easily distinguished from other species of Hyalella from the USA, Mexico, and the Caribbean by the atypical number of setae on the inner plate of maxilla 1 (four setae) and maxilla 2 (three setae), and by the shape of the telson. The species morphologically most similar to H. tepehuana sp. nov. is H. faxoni Stebbing, 1903 from the Volcan Barva in Costa Rica, but Hyalella tepehuana sp. nov. differs by the presence of dorsal processes on pereionites 1 and 2, and by the following characters: number of articles on antennae 1 and 2 (9–11 and 11 or 12, respectively, in H. tepehuana sp. nov. versus 12 and 15–17, respectively, in H. faxoni); number of setae on propodus inner face of gnathopod 1 (four in H. tepehuana sp. nov. versus five in H. faxoni); number of setae on the posterior basis of male gnathopod 2 (two in H. tepehuana sp. nov. versus four in H. faxoni); shape of uropod 3 (styliform in H. tepehuana sp. nov. versus globose in H. faxoni); and telson shape (longer than wide in H. tepehuana sp. nov. versus quadrate and wider than long in H. faxoni). Furthermore, in the new species, the fourth article (= dactyl) of maxilliped is more slender than in H. faxoni, according to
Morphological differences of males and females among Hyalella azteca (De Saussure, 1858) (based in redescription by
Character | Hyalella azteca (De Saussure, 1858) | Hyalella faxoni Stebbing, 1903 | H. tepehuana sp. nov. |
Size (mm) | 7.8 | 8.7 | 5–6.75 |
Dorsal process in pereionites 1–2 (mucronations) | yes | no | yes |
Maxilla 1, number of pappose setae on the inner plate | 3 | 4 | 3–4 |
Maxilla 1, palp apical stout setae | no | yes | yes |
Maxilla 2, inner plate pappose setae | 2 | 3 | 2–3 |
Mandibles, lacinia mobilis number of teeth | 5 | 5 | 5–6 |
Antenna 1, number of flagellum articles | 7 | 12 | 9–11 |
Antenna 1, number of flagellum articles | 8 | 15–17 | 11–12 |
Uropod 3 | styliform | globose | styliform |
Male gnathopod 2, hind margin setae | 2 | 4–6 | 2 |
Male gnathopod 1, carpus lobe, inner face, number of pappose setae | 1–3 | 1–3 | 3 |
Male gnathopod 1, propodus, inner face, number of pappose setae | 4 | 5 | 3–4 |
Female gnathopod 1, propodus palm | reverse oblique | slightly reverse oblique | slightly reverse oblique |
Uropod 1, outer ramus dorsal setae | 2 | 3 | 3 |
Telson | width ≈ length, apically pointed with two apposed long simple setae | width > length, quadrate with two short widely apart setae | width < length, apically narrowed (semitriangular) with two long widely apart simple seta |
Due to the subtle variations within species, and lack of morphological studies and formal descriptions, the identification of species of Hyalella in North America is complex. Hence, the new characters proposed by
Hyalella tepehuana sp. nov. is also similar to the recently described H. wakulla Drumm & Knight-Gray, 2019, from Florida, USA. These two species have a similar body length, about 5.5 mm, by which they may be considered to be smaller ecomorphs; however, the main differences between these two species are the number of articles in antennae 1 and 2, and the number of setae on the buccal parts: Hyalella tepehuana sp. nov. has more articles in antenna 1 (9–11) and antenna 2 (11–12) while H. wakallua has fewer articles in antenna 1 (eight) and antenna 2 (nine). The new species also bears a maximum of four setae on the inner plate of maxilla 1 and bears setules on the palp, whereas, H. wakulla bears three setae on inner plate of maxilla 1, and the palp lacks setules. Also, H. tepehuana sp. nov. has a maximum of three pappose setae on the inner plate of maxilla 2, while H. wakulla has only two, and the maxilliped fourth article in H. tepehuana sp. nov. has fewer than four subterminal setae on the medial margin in contrast to H. wakulla, which has a maximum of four subterminal setae in adults. We consider the differences presented here sufficient to consider Hyalella tepehuana sp. nov. as a new species.
1 | Eyes absent | 2 |
– | Pigmented eyes present | 3 |
2 | Antenna 1 is longer than antenna 2; sternal gills on pereonites 3–7; telson with four distal setae | H. muerta |
– | Antenna 1 shorter than antenna 2; sternal gills on pereonites 2–7; telson without distal setae | H. cenotensis |
3 | Body with dorsal mucronations | 9 |
– | Body without dorsal mucronations | 4 |
4 | Ramus of uropod 3 is vestigial or robust, subequal or shorter than peduncle | 5 |
– | Ramus of uropod 3 slender, subequal or longer than peduncle | 6 |
5 | Ramus of male uropod 3 robust, with seven apical spines | H. sandra |
– | Ramus of male uropod 3 vestigial, with two to four spines | H. meraspinosa |
6 | Antenna 1 and 2 are subequal in length (antenna 1 slightly shorter) | 7 |
– | Antenna 2 is nearly twice the length of antenna 1 | H. longicornis |
7 | Hind margin of merus of pereopods 3 and 4 with long setae; telson with two closely apical setae | H. caribbeana (H. squamosa, material needs revision and redescription, but the main differences seem to be the length of antennae and the chaetotaxia in the gnathopods (basis, carpus, and propodus)) |
– | Hind margin of article 4 of pereopods 3 and 4 with short setae; telson with two long, broadly-spaced, apical setae | 8 |
8 | Maxilla 1 inner plate with two setae, pereiopod 7 basis lobe ventral margin with three stout setae; pereiopod 7 basis anterior margin half distal margin with short stout setae (4); uropod 2 ramus with two dorsal setae; maxilla 2 with serrate setules |
H. cheyennis (H. inermis, material needs revision and redescription, but the main difference seems to be the maxilla 2 with serrate setules according to |
– | Maxilla 1 inner plate with more than two setae (4), pereiopod 7 basis lobe ventral margin without stout setae; pereiopod 7 basis anterior margin half of proximal and distal margin with short stout setae (7); uropod 2 peduncle ramus with three dorsal setae; maxilla 2 probably without serrate setules | H. faxoni |
9 | Inner plate of maxilla 1 narrow, with two to five apical plumose setae | 10 |
– | Inner plate of maxilla 1 is broad, subtriangular, with two or three apical plumose setae, followed closely by 22–30 similar medial setae | H. montezuma |
10 | Antenna 1 is longer than half the length of antenna 2, and only first or first two abdominal segments bearing dorsal mucronations | 11 |
– | Antenna 1 is less than half the length of antenna 2, with all three abdominal segments bearing dorsal mucronations | H. texana |
11 | Gnathopod 2 of males, carpus posterior lobe is about as long as width of merus; in pereopod 7, the distal/ventral margin of basis posterior lobe, dentate or not, with one or two very small setae if any | 13 |
– | Gnathopod 2 of males, carpus posterior lobe approximately 1.5× as long as width of merus, pereiopod 7, distal/ventral margin of basis posterior lobe dentate with at least three stout setae | 12 |
12 | Pereiopod 3 posterior margin with one setae; pereiopod 5 merus and carpus length subequal; pereopod 7 with distal/ventral margin of the basis posterior lobe strongly dentate, with two or more (five) relatively long spines; telson distal margin acute with two apposed setae; female gnathopod 1; carpus inner face with two setae; mandible incisor with six teeth | H. azteca |
– | Pereiopod 3 posterior margin with two setae; pereiopod 5 merus longer than carpus; pereopod 7 with distal/ventral margin of the basis posterior lobe strongly dentate, and with one or two relatively long spines (fewer than three), distal end of telson narrowing , distal margin rounded or truncated with two widely apart setae; female gnathopod 1, carpus inner face with four setae; mandible incisor with seven teeth | H. tepehuana sp. nov. |
13 | Gnathopod 2 propodus in males: palm with a distinct angle step (visible under high power), tip of dactyl approximately aligns vertically with distal end of posterior lobe of carpus; telson distal setae is separated, short, and at least as stout as setae on uropod 3 ramus | H. spinicauda |
– | Gnathopod 2 propodus in males: palm without a distinct angle step or notch, tip of dactyl aligning vertically well beyond (posteriorly) distal end of posterior lobe of carpus; telson terminal setae clearly thinner and longer than setae on uropod 3 ramus | 14 |
14 | Telson with two long and slender apposed setae; uropod 3 ramus approximately as long as or slightly longer than the longest seta on peduncle; pereopod 7 posterior lobe ventral margin without stout setae; maxilla 1, inner plate with two pappose setae; maxilliped nail short, less than half the length of palp article 4 | H. wellborni |
– | Telson with two long and slender setae widely separated; uropod 3 ramus longer than the longest setae on peduncle; pereopod 7 posterior lobe ventral margin with one stout setae; maxilla 1, inner plate with three pappose setae; maxilliped nail long, more than half length of palp article 4 | H. maya |
The first author is grateful with the Posgrado en Ciencias del Mar y Limnología,