Aegla urussanga, Arantes & Souza-Shibatta & Teixeira, 2024

Arantes, Tiago, Souza-Shibatta, Lenice & Teixeira, Gustavo Monteiro, 2024, Description of a new species of Aegla (Decapoda, Anomura) from the Paraná 3 hydrographic basin, Brazil, Zootaxa 5418 (4), pp. 371-384 : 374-378

Aegla urussanga n. sp.

( Figs. 2 , 3 )

Type material. Holotype: male (CLE 22.0 mm), Brazil, Paraná, São Miguel do Iguaçu, set of drainages named Paraná 3 River Basin , nameless stream, 25°16'15.8"S, 54°13'31.7"W, altitude 238 m, October 2022, T. Arantes, G. M. Barbosa, MZUEL 545 .

Paratypes: 3 males (CLE 12–19.2 mm) , 4 females (CLE 10.9–13.3 mm), same holotype data, collected in December 2020, MZUEL 525 ; 20 males (CLE 10–18.6 mm) , 12 females ( CLE 9–15.4 mm) Vera Cruz do Oeste , Córrego Surucuá, 25°01'54.2"S, 53°55'00.0"W, July 2022, MZUEL 533 ; 9 males (CLE 10.4–15.4 mm) , 3 females ( CLE 9.5–12 mm), Matelândia , Rio Xaxim, 25°06'44.3"S, 53°56'54.7"W, July 2022, MZUEL 534 ; 1 male (CLE 13.4 mm) , 4 females (CLE 11–16 mm), holotype data, MZUEL 546 ; 2 ovigerous females (CLE 12–13.5 mm), holotype site, July 2021, MZUEL 528 ; 4 males (CLE 12.7–16 mm) , 3 females (CLE 9–11.2 mm), holotype site, December 2021, MZUEL 526 ; 1 male (CLE 16 mm) , 4 females ( CLE 12.6 – 14.4 ), Toledo , nameless stream, 24°48'43.3''S, 53°42'31.3''W, January 2023, MZUEL 579 ; 11 males (CLE 13–20.5 mm) , 12 females ( CLE 11.4–17.7mm), Toledo , nameless stream, 24°51'47.2''S, 53°45'35.7''W, January 2023, MZUEL 578 .

Additional material for DNA extraction. 1 juvenile and 1 adult, holotype data, July 2021, MZUEL 523 ; 2 juveniles, MZUEL 533 ; 2 juveniles, MZUEL 534 ; 1 juvenile, 578; 1 juvenile 579 used for DNA extraction.

Diagnosis. Carapace anterolateral spine not reaching the base of the cornea; outer orbital margin bluntly rounded; shallow and open extraorbital sinus; non-elevated epigastric prominences indicated by scales; protogastric lobes robust, scaled. Anterior margin of abdominal epimeron 2 with a pronounced concavity (in dorsal view) and lateral spine. Thoracic sternite 3 tapered with armed apical end. Chelipeds with sub-rectangular palmar crest; ischium inner ventral surface with proximal stout spine, distal stout spine, and up to 3 tubercles with spiniform scale.

Holotype description. Cephalothorax slightly convex, gastric region convex, scabrous dorsal surface. Rostrum triangular, base narrow ( RBW /LMR = 0.93), extending beyond apex of eyes, carinated along entire length, slightly deflected dorsally; dorsal carina beginning at level of protogastric lobes, with row of corneous scales extending to apex; subrostral margin with well-developed, obtusely rounded process, occupying the proximal one-third of margin ( Fig. 4B ). Carapace anterolateral spines with corneous, acuminate apex, not reaching base cornea. Orbital sinuses deep, extraorbital sinuses shallow; outer orbital margin bluntly rounded, unarmed. Epigastric prominences not elevated, demarcated by subtle scales. Protogastric lobes pronounced, with corneous scales. Gastric region elevated above hepatic lobes. The demarcation between the first and second hepatic lobes is clearly defined, while the demarcation between the second and third hepatic lobes is weak on the left side but well-defined on the right side. Lateral margins of hepatic lobes with small corneous scales.

Cervical groove with subtrapezoidal shape. Sub-rectangular areola (AH/[( APM +AAD)/2] = 2.08). Trapezoidal cardiac area ( TDL /PMC = 1.28) ( Fig. 2A ). Triangular epibranchial area, slightly elongated, with a small spine at its apex and the lateral line acuminated by scales, anterolateral angle with corneous scales, lateral margin with a row of corneous scales ( Fig. 4A ). Lateral margins of anterior and posterior branchial regions with row of corneous scales.

Thoracic sternite 3 tapered, apex armed; sternite 4 also armed ( Fig. 2C , 5B ).

Abdominal epimeron 2 (in dorsal view) with pronounced anterior concavity ending with sharp lateral spine ( Fig. 2D , 5A ).

Chelipeds of similar form, size unequal, left larger. Dactylus with unarmed dorsal margin and external surface; proximal dorsal margin without lobe. Palm with sub-rectangular crest, all surface scabrous. Ischium ventromesial border of the major cheliped (left) with stout proximal spine, stout distal spine, and only one spiniform scale between spines ( Fig. 2B ) (Fig. 6A, B). Smaller cheliped (right) ischium with stout proximal spine, stout distal spine, and 2 tubercles with spiniform scale between spines (Fig. 6C, D). Pereiopod 2 merus with proximal dorsal margin acuminate, with setae and tubercles with conical scales, with small subdistal spine and longer distal spine; posteroventral distal margin with 2 spines and conical tubercle between them. Carpus dorsal margin ornamented with longitudinal scales along entire length, ending in robust distal spine.

Variations. Females and small individuals of both sexes have conical tubercles or spines and scattered bristles on the cheliped palmar crests, with variation in number of these structures (Fig. 7, 8). The ventromesial margin of the ischium may vary in shape and number of tubercles between the larger spines, and may be absent and have up to 3 tubercles or scales. The spine of abdominal epimeron 2 may be smaller than that of the holotype. In small individuals, the distal spines on the dorsal surface of the merus of the second pereiopod may be reduced to tubercles or acute scales.

Etymology. The specific epithet is derived from the Tupi-Guarani language, the word "Urussanga is formed by two words from the indigenous language, meaning "place of a river with very cold water", referring to the type locality, Urussanga community.

Molecular data. We analyzed 916 base pairs (bp) of the COI gene with an excellent resolution. The genetic distances between A. urussanga n. sp. and its congeners ranged from 1.2% to 5.1% ( Tab. 1 ), with the species with the lowest genetic distance being A. castro (1.2%), A. parana 1 (1.4%), A. buenoi (1.7%), A. jacutinga (1.7%), A. meloi (1.7%) and A. parva (1.9%). Aegla marginata exhibited the highest divergence from the new species at 5.1%. Both GMYC and ASAP analyzes ( Fig. 9 ) suggests the presence of 17 distinct species, separating A. parana into two clades.

Figures

FIGURE 2. Aegla urussanga n. sp., male holotype, CLE 22.0 mm, Paraná 3 River Basin, Paraná, Brazil, MZUEL 545:A, dorsal view of cephalothorax and anterior portion of abdomen; B, ventral view of ischium of greater cheliped (left) with two spines and one tubercle; C, third sternite abrupt with armed apical end; D, dorsal view of anterior margin of epimeron 2 with very pronounced concavity ending with sharp spine. Scale: A = 10.0 mm; B–D = 1.0 mm.

FIGURE 3. Aegla urussanga n. sp., male holotype, CLE 22.0 mm, Paraná 3 River Basin, Paraná, Brazil, MZUEL 545. Scale = 10.0 mm.

FIGURE 4. Aegla urussanga n. sp., male holotype, CLE 22.0 mm, Paraná 3 River Basin, Paraná, Brazil, MZUEL 545: A, dorsal view of anterior region of cephalothorax showing trapezoidal cervical sulcus (black arrow) and shortened epibranchial area (white arrow); view of anterior region of cephalothorax showing pronounced protogastric lobes (white arrow) and welldeveloped subrostral process (black arrow). Scale = 1.0 mm.

FIGURE 5. Aegla urussanga n. sp., male holotype, CLE 22.0 mm, Paraná 3 River Basin, Paraná, Brazil, MZUEL 545:A, dorsal view of anterior margin of epimeron 2 with very pronounced concavity (white arrow) ending with sharp spine (gray arrow); B, third sternite (black arrow), fourth sternite spines (white arrows). Scale = 1.0 mm.

FIGURE 9. Bayesian tree (HKY+I+G) for species of Aegla based on partial COI gene sequences. Generalized Mixed Yule- Coalescent (GMYC) (Bayesian analysis) and Assemble Species by Automatic Partitioning (ASAP) (genetic distance analysis) both test for species delimitation. The vertical bars, from left to right, indicate GMYC and ASAP, respectively.