Macrobrachium pantanalense, Santos, Antonina Dos, Hayd, Liliam & Anger, Klaus, 2013
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publication ID |
https://doi.org/ 10.11646/zootaxa.3700.4.2 |
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publication LSID |
lsid:zoobank.org:pub:5C2CFE85-3B62-47FE-8823-65A7A68A5404 |
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DOI |
https://doi.org/10.5281/zenodo.5664248 |
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persistent identifier |
https://treatment.plazi.org/id/A12C87D9-FFA2-FFE3-FF29-F8F4A854FB29 |
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treatment provided by |
Plazi |
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scientific name |
Macrobrachium pantanalense |
| status |
sp. nov. |
Macrobrachium pantanalense View in CoL sp. nov.
( Figs 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )
Material examined. Male holotype: (5.2 mm CL, 30.5 mm TL, 7.1 mm rostrum) MZUSP 26207. 1 Ovigerous female paratype: (7.9 mm CL, 42.6 mm TL, 11.5 mm rostrum, 0.92± 0.08 mm eggs diameter). 2 female paratypes: (9.0 and 9.6 mm CL, 54.8 and 55.0 mm TL, 14.4 and 14.3 mm rostrum). 1 male paratype: (and 7.4 mm CL, and 43.0 mm TL, and 10.7 mm rostrum) MZUSP 26208, Baiazinha Lagoon (20º16’S / 56º23’ W), an adjacent shallow lake connected to the Miranda river and located in the Pantanal of Miranda, State of Mato Grosso do Sul (MS), Brazil, <1 m depth, coll. L. Hayd, October 2009.
Diagnosis. Small caridean shrimp with well developed, dorsally and ventrally toothed rostrum. Carapace presents antennal and hepatic spines and branchiostegal sulcus. Mandible with 3-segmented palp. All maxillipeds with exopods. First two pairs of pereiopods chelate, slender, as long as the carapace. Last three pairs of pereiopods simple. Telson with two pairs of dorsal and two pairs of posterior spines.
Description. Small sized palaemonid shrimp of subcylindrical form ( Figs 1 View FIGURE 1 , 2 View FIGURE 2 , 5 View FIGURE 5 ). Carapace smooth, glabrous, hepatic and antennal spines present. Rostrum long with anterior half directed obliquely upwards, about 1.6 of the carapace length (1.2 for individuals with less than 35 mm long), with 9 to 11 teeth on dorsal margin, the first one placed on the orbit or slightly behind the orbit (smaller individuals); the last three teeth, one is placed between two distinct naked spaces, the last two near the tip ( Figs 1 View FIGURE 1 , 2 View FIGURE 2 ). However, some males have the teeth equally distributed along the dorsal margin ( Fig. 4 View FIGURE 4 A). The ventral margin has 5 to 9 teeth ( Figs 1 View FIGURE 1 , 2 View FIGURE 2 , 4 View FIGURE 4 A). Eye with globular cornea, about 0.2 times of carapace length ( Fig. 3 View FIGURE 3 A).
Abdomen smooth. The sixth segment about 1.5 times length of the fifth, with the posterolateral and posteroventral angles strongly produced and acute. First four pleurae broadly rounded, the fifth produced posteriorly and acute ( Figs 1–2 View FIGURE 1 View FIGURE 2 ).
Telson about 1.2 times the sixth segment length and about 3 times longer than the proximal width, lateral margins are straight and convergent, ending in sharp median point ( Figs. 4 View FIGURE 4 N–4P). The dorsal surface bears two pairs of spines, at about 0.5 and 0.7 of telson length. On the posterior margin presents two pairs of spines, the exterior pair distinctly smaller than the interior one, which overreaches the apex of the telson. In most of specimens, the inner pair of spines reaches farther beyond the tip of telson. All specimens present a pair of plumose setae placed between the apex of telson and the interior pair of spines. The plumose setae are longer than the spines ( Fig. 4 View FIGURE 4 P).
Antennule ( Fig. 3 View FIGURE 3 B): proximal peduncular segment about 1.8 times longer than wide, anterolateral margin strongly produced, with stout distolateral tooth extending to about 0.4 of intermediate peduncular segment length, stylocerite acute, short, reaching about 0.4 of the proximal segment length; intermediate peduncular segment about 0.3 of proximal segment length, with lamellae very obliquely articulated with distal segment; distal segment about 0.2 of proximal segment length; upper flagellum biramous with about 12 rami fused proximally.
Antenna ( Fig. 3 View FIGURE 3 C): distal peduncular segment reaching about 0.3 of scaphocerite length; flagellum about 5 times carapace length; scaphocerite exceeds the antennular peduncle, about 3.5 times longer than wide, lateral margin strait, with stout distolateral tooth slightly exceeded by broad distal margin.
Mandible ( Fig. 3 View FIGURE 3 D): robust incisor process with three teeth; mandibular palp slender with three segments, distal segment slightly longer than the two proximal segments, as figured. Maxillulla ( Fig. 3 View FIGURE 3 E): palp bilobed, unarmed, as figured. Maxilla ( Fig. 3 View FIGURE 3 F) with basal endite deeply bilobed; palp unarmed; scaphognathite well developed, lobes distally rounded, with about 183 setae along margins.
First maxilliped ( Fig. 3 View FIGURE 3 G) with distinct basal and coxal endites, epipod bilobed (not figured), palp small with 2 simple setae, exopod with caridean lobe and flagellum with long plumose setae on the distal part. Second maxilliped ( Fig. 3 View FIGURE 3 H) with stout endopod, terminal dactyl article, distally elongated, with rows of long marginal setae; propodus broader than long, with sparsely distributed setae along the upper margin; carpus short, with very small simple setae; merus longer than ischium; exopod two-segmented, proximolaterally with lamellar expansion, plumose setae on distal segment; epipod simple. Third maxilliped ( Fig. 3 View FIGURE 3 I) with robust endopod, all three segments strongly setose, proximal segment with lamellar expansion; exopod not reaching distal margin of ischiomerus, with plumose setae on distal margin; coxa armed with a few setae on inner lateral margin; ventral arthrobranchs larger than dorsal ones.
First pereiopod ( Fig. 4 View FIGURE 4 B) slender, slightly overreaching scaphocerite (in smaller specimens reaching scaphocerite), chela with palm slightly compressed, fingers about equal to palm length, with entire cutting edges along almost all finger length, carpus about 2.6 times chela length and 1.2 times merus length.
Second pereiopods ( Fig. 4 View FIGURE 4 C) similar, equal, overreaching tip of rostrum; chela slender, palm about 8 times longer than wide, glabrous, fingers sparsely setose with tufts of setae on tip, fingers about 0.44 of palm length, with stout, feebly hooked tip, distal 0.7 with entire cutting edge, proximal edge with one small tooth; carpus slender, unarmed, about 1.7 times longer than chela; merus unarmed, about 0.6 of carpus length; ischium sparsely setose, about as long as merus; basis and coxa without special features.
Third to fifth pereiopods ( Figs 4 View FIGURE 4 D–4F) similar, slender, not reach tip of scaphocerite; third pereiopod with feebly curved dactylus, dorsal with sparse packs of short setae, ventral border sharp, propodus about 2.2 times dactyl length, with 5 single ventral spines, 2 single spines placed dorso-distally and 1 pair placed distally, carpus about 0.44 of propod length, merus about 2.6 times carpus length; fourth pereiopod with dactyl feebly curved, dorsally with sparse setae, ventral border sharp, propodus about 2.9 times dactyl length, with 5 spines along ventral margin and 2 spines placed distally, carpus about 0.4 of propod length, with distal margin strongly produced; fifth pereiopod with feebly curved dactylus, with sparse simple small setae on both margins, propod about 3.5 times dactyl length, with small simple setae on dorso-distal margin, carpus about 0.44 of propod length, with distal margin strongly produced.
First pleopod ( Figs 4 View FIGURE 4 G–4H) with basipodite 2.9 times longer than wide, endopod 0.4 of basipodite length, proximally wider than distally, with 13 fine plumose setae along the half distal margin, 9 very small simple setae placed sub-marginally. In males the endopod is 0.7 of basipodite length, slightly tapering distally, medial border centrally emarginated, with 33 long finely plumose setae along margin, proximally 9 longer, fine plumose setae, sub-marginally,5 small setae. Appendix interna absent in first pleopod but present on second to fifth pleopod. Appendix masculina ( Fig. 4 View FIGURE 4 J) on second pleopod of males about 2/3 the size of the endopod and two times as long as appendix interna. Appendix masculina has one sparsely setose spine near the anterior end, 11 simple setae along margin, and a strong seta at posterior end. Third to fifth pleopods ( Fig. 4 View FIGURE 4 K–4L) with endopod slightly smaller than exopod, all with plumose setae on margins, as figured.
Uropod ( Fig. 4 View FIGURE 4 M) protopod with lateral small tooth; exopod with daeresis bearing very small tooth laterally; endopod subequal to exopod length.
Color in life. The animals are semi-transparent with small brownish patches all over the body, including appendices such as the pereiopods, the uropods, and the scaphocerite, which gives it an overall beige appearance ( Fig. 5 View FIGURE 5 A).
Etymology. The new species is named after the region where it was spotted for the first time, the Pantanal (Portuguese name, meaning large wetland or swamp). This seasonally flooded savanna region is considered as the world’s largest wetland, being a UNESCO World Heritage Site since the year 2000.
Type locality and distribution. All specimens of Macrobrachium pantanalense were collected from the Baiazinha Lagoon, a shallow lake connected to the Miranda River in the Pantanal of the State of Mato Grosso do Sul, Brazil.
Habitat and ecology. The Rio Miranda is one of the major rivers of the Pantanal section in the state of Mato Grosso do Sul, Brazil. Shrimps are most commonly found in lentic habitats connected to the main river (e.g. Lagoa Baiazinha; see Hayd and Anger, 2013) as well as near the river banks, where currents are reduced and where fallen trees, overreaching riparian vegetation, or floating mats of aquatic plants ( Eichhornia azurea , E. crassipes , Alchornea castaneifolia ) provide shelter and some shade. Ecological and hydrological characteristics of the Rio Miranda have been described by Depaula et al. (1995), Resende et al. (2000), Hayd and Nakagaki (2002), Mendes et al. (2004), Resende et al. (2006), Pivari et al. (2008), Soares and Oliveira (2009); shallow Pantanal lakes, in general, were described in more detail by Heckman (1998), Willink et al. (2000), Suarez et al. (2004), Wantzen et al. (2008), and Tondato et al. (2010).
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