A new species of stygobitic aeglid from lentic subterranean waters in southeastern Brazil, with an unusual morphological trait: short pleopods in adult males

Aegla charon n. sp. is endemic to the “Lago Subterrâneo” cave from the Alto Ribeira karst region, southeastern Brazil. The most remarkable morphological trait observed in the new species was the presence of partially developed pair of uniramous pleopods 2‒5 in adult male specimens, whereas the absence of these pleonal appendages is the general condition in this sex in Aegla Leach, 1820. Some of the pleopods are even morphologically similar to those typically observed in adult females in that they may also be two-segmented, only shorter in size. The pigmented area of the cornea is slightly reduced, which is probably a troglomorphic adaptation to subterranean habitats. Aegla charon n. sp. is also the only obligate cave-dwelling aeglid known to inhabit lentic subterranean waters. A key to all species from the Alto Ribeira karst area is provided.

Key words
Aeglidae; high endemism; pleonal appendages in males; subterranean lake

Authorship

Sérgio Luiz de Siqueira Bueno

Department of Zoology, Institute of Biosciences (IB-USP), University of São Paulo. Rua do Matão, 101. 05508-090 São Paulo, São Paulo, Brazil. SLSB E-mail: sbueno@ib.usp.br; JCBM E-mail: jcbm@ib.usp.brUniversity of São PauloBrazilSão Paulo, São Paulo, BrazilDepartment of Zoology, Institute of Biosciences (IB-USP), University of São Paulo. Rua do Matão, 101. 05508-090 São Paulo, São Paulo, Brazil. SLSB E-mail: sbueno@ib.usp.br; JCBM E-mail: jcbm@ib.usp.br

Alexandre Lopes Camargo
Rua Dr. Curt, 218. 09862-040 São Bernardo, São Paulo, Brazil. ALC E-mail: iscoticave@gmail.com

Juliana Cristina Bertacini Moraes

Corresponding author: Sérgio Luiz de Siqueira Bueno sbueno@ib.usp.br

Rua Dr. Curt, 218. 09862-040 São Bernardo, São Paulo, Brazil. ALC E-mail: iscoticave@gmail.com

SCIMAGO INSTITUTIONS RANKINGS

Figures

Figures (12)

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Figure 1
Map of the Alto Ribeira karst region (partial) in the state of São Paulo, Brazil, showing the border limits of the PETAR (Parque Estadual Turístico do Alto Ribeira) and Intervales State Park (PEI in Portuguese), and the corresponding type locality of the stygobitic aeglids: (a) Aegla leptochela and (b) A. charon n. sp. from Intervales, and (c) A. microphthalma and (d) A. cavernicola from PETAR. Light blue areas on map indicate distribution of limestone lenses. Modified from Fernandes et al. (2013).

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Figure 2
A, Floor plan; B, longitudinal section maps of “Lago Subterrâneo” cave, with indication of sampling site. This map was drawn and produced by Grupo Bambuí de Pesquisas Espeleológicas and used herein by kind permission.

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Figure 3
Visual search for aeglids in shallow areas near margins of the subterranean lake (partial view). Photo by Alexandre L. Camargo.

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Figure 4
Live male specimen of Aegla charon n. sp. Photo by Alexandre L. Camargo.

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Figure 5
Measurements taken to calculate: A, height of palm of both major and minor chelae (solid lines a, b, as indicated on major chela); B, shapes of cardiac (solid lines a, b) and areolar (dashed lines c, d, h) areas. See “Materials and Methods” for details.

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Figure 6
Aegla charon n. sp., male, holotype (CL 20.40 mm; CLR 23.91 mm) (MZUSP 35193), dorsal view. Scale bar = 5.0 mm.

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Figure 7
Aegla charon n. sp., male, holotype (MZUSP 35193). A) Lateral view of anterior region of carapace; B, Coxa, basi-ischium and merus (part); C, Third (in top position) and fourth sternites; D, Second pleonal epimeron. Scale bars = 2.5 mm.

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Figure 8
Aegla charon n. sp., male paratype (CL 20.57 mm; CLR 23.95 mm) (MZUSP 35194), sexual tube (arrow) on the coxa of the left fifth pereopods. Scale bar = 500 μm.

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Figure 9
Aegla charon n. sp., male, holotype (MZUSP 35193), telson and uropods. Scale bar = 5.0 mm.

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Figure 10
Aegla charon n. sp., male paratype (CL 18.11 mm; CLR 21.46 mm) (MZUSP 35194), subrostral process. Scale bar = 5.0 mm.

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Figure 11
Aegla charon n. sp., male paratype (CL 20.57 mm; CLR 23.95 mm) (MZUSP 35194), ventral view of pleon after being streched out, showing pairs of pleopods (PL) 2 through 5. Except for one of the PL2, which is depicted as 1-segmented, all other pleopods are 2-segmented and bearing few long setae distally.

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Figure 12
Distal portion of anterior region of carapace showing relative difference in size of pigmented area of cornea among aeglids: Grade 0 (fully developed) in the epigean species Aegla perobae (A) and in the stygophilic species A. strinatii (B). Grade 1 (slightly reduced) in the stygobitic species A. charon n. sp. (C), and A. leptochela (D). Grade 2 (greatly reduced) in the stygobitic species A. cavernicola (E). Grade 3 (absent) in the stygobitic species A. microphthalma (F). All species are endemic to Alto Ribeira karst region, except A. perobae, which is endemic to the Tietê Hydrographic Basin. Scale bars = 2.0 mm.

Figure 1 Map of the Alto Ribeira karst region (partial) in the state of São Paulo, Brazil, showing the border limits of the PETAR (Parque Estadual Turístico do Alto Ribeira) and Intervales State Park (PEI in Portuguese), and the corresponding type locality of the stygobitic aeglids: (a) Aegla leptochela and (b) A. charon n. sp. from Intervales, and (c) A. microphthalma and (d) A. cavernicola from PETAR. Light blue areas on map indicate distribution of limestone lenses. Modified from Fernandes et al. (2013).

Figure 2 A, Floor plan; B, longitudinal section maps of “Lago Subterrâneo” cave, with indication of sampling site. This map was drawn and produced by Grupo Bambuí de Pesquisas Espeleológicas and used herein by kind permission.

Figure 3 Visual search for aeglids in shallow areas near margins of the subterranean lake (partial view). Photo by Alexandre L. Camargo.

Figure 4 Live male specimen of Aegla charon n. sp. Photo by Alexandre L. Camargo.

Figure 5 Measurements taken to calculate: A, height of palm of both major and minor chelae (solid lines a, b, as indicated on major chela); B, shapes of cardiac (solid lines a, b) and areolar (dashed lines c, d, h) areas. See “Materials and Methods” for details.

Figure 6 Aegla charon n. sp., male, holotype (CL 20.40 mm; CLR 23.91 mm) (MZUSP 35193), dorsal view. Scale bar = 5.0 mm.

Figure 7 Aegla charon n. sp., male, holotype (MZUSP 35193). A) Lateral view of anterior region of carapace; B, Coxa, basi-ischium and merus (part); C, Third (in top position) and fourth sternites; D, Second pleonal epimeron. Scale bars = 2.5 mm.

Figure 8 Aegla charon n. sp., male paratype (CL 20.57 mm; CLR 23.95 mm) (MZUSP 35194), sexual tube (arrow) on the coxa of the left fifth pereopods. Scale bar = 500 μm.

Figure 9 Aegla charon n. sp., male, holotype (MZUSP 35193), telson and uropods. Scale bar = 5.0 mm.

Figure 10 Aegla charon n. sp., male paratype (CL 18.11 mm; CLR 21.46 mm) (MZUSP 35194), subrostral process. Scale bar = 5.0 mm.

Figure 11 Aegla charon n. sp., male paratype (CL 20.57 mm; CLR 23.95 mm) (MZUSP 35194), ventral view of pleon after being streched out, showing pairs of pleopods (PL) 2 through 5. Except for one of the PL2, which is depicted as 1-segmented, all other pleopods are 2-segmented and bearing few long setae distally.

Figure 12 Distal portion of anterior region of carapace showing relative difference in size of pigmented area of cornea among aeglids: Grade 0 (fully developed) in the epigean species Aegla perobae (A) and in the stygophilic species A. strinatii (B). Grade 1 (slightly reduced) in the stygobitic species A. charon n. sp. (C), and A. leptochela (D). Grade 2 (greatly reduced) in the stygobitic species A. cavernicola (E). Grade 3 (absent) in the stygobitic species A. microphthalma (F). All species are endemic to Alto Ribeira karst region, except A. perobae, which is endemic to the Tietê Hydrographic Basin. Scale bars = 2.0 mm.

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A new species of stygobitic aeglid from lentic subterranean waters in southeastern Brazil, with an unusual morphological trait: short pleopods in adult males

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[1] Corresponding author: Sérgio Luiz de Siqueira Bueno sbueno@ib.usp.br