Corresponding author: Aurora Marrón-Becerra (
Academic editor: T. Horton
A new species,
Marrón-Becerra A, Hermoso-Salazar M, Rivas G (2020) A new species of the genus
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 (
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
We present a key of the species from North America, Central America, and Caribbean region. However,
Family
Genus
The specific epithet
Holotype male, body length 5.4 mm (
Mexico, Durango, Tunal River in La Ferrería:
Type locality. Tunal River, La Ferrería, Durango state, Mexico (
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.
Mean body length of males: 5.7 ± 0.6 mm (
Mean cephalothorax length: 0.6 ± 0.03 mm (
Epimeral plates 1–3 acuminate.
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 (
Morphological differences of males and females among
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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 |
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
1 | Eyes absent |
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– | Pigmented eyes present |
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2 | Antenna 1 is longer than antenna 2; sternal gills on pereonites 3–7; telson with four distal setae |
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– | Antenna 1 shorter than antenna 2; sternal gills on pereonites 2–7; telson without distal setae |
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3 | Body with dorsal mucronations |
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– | Body without dorsal mucronations |
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4 | Ramus of uropod 3 is vestigial or robust, subequal or shorter than peduncle |
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– | Ramus of uropod 3 slender, subequal or longer than peduncle |
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5 | Ramus of male uropod 3 robust, with seven apical spines |
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– | Ramus of male uropod 3 vestigial, with two to four spines |
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6 | Antenna 1 and 2 are subequal in length (antenna 1 slightly shorter) |
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– | Antenna 2 is nearly twice the length of antenna 1 |
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7 | Hind margin of merus of pereopods 3 and 4 with long setae; telson with two closely apical setae |
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– | Hind margin of article 4 of pereopods 3 and 4 with short setae; telson with two long, broadly-spaced, apical setae |
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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 |
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– | 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 |
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9 | Inner plate of maxilla 1 narrow, with two to five apical plumose setae |
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– | Inner plate of maxilla 1 is broad, subtriangular, with two or three apical plumose setae, followed closely by 22–30 similar medial setae |
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10 | Antenna 1 is longer than half the length of antenna 2, and only first or first two abdominal segments bearing dorsal mucronations |
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– | Antenna 1 is less than half the length of antenna 2, with all three abdominal segments bearing dorsal mucronations |
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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 |
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– | 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 |
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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 |
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– | 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 |
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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 |
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– | 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 |
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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 |
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– | 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 |
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The first author is grateful with the Posgrado en Ciencias del Mar y Limnología,
modified from Baldinger 2004; Marrón-Becerra et al. 2014; Soucek et al. 2015; Marrón-Becerra et al. 2018.