Aegla pomerana, Bond-Buckup & Jara & Buckup & Pérez-Losada & Bueno & Crandall & Santos, 2010

Bond-Buckup, Georgina, Jara, Carlos G., Buckup, Ludwig, Pérez-Losada, Marcos, Bueno, Alessandra A. P., Crandall, Keith A. & Santos, Sandro, 2010, New Species And New Records Of Endemic Freshwater Crabs From The Atlantic Forest In Southern Brazil (Anomura: Aeglidae), Journal Of Crustacean Biology 30 (3), pp. 495-502 : 496-498

Aegla pomerana n. sp. Bond-Buckup and Buckup

( Fig. 2 )

Type-material.— Holotype male, Brazil, state of Santa Catarina, Pomerode, Sítio Mundo Antigo tributary in the Rio Itajaí-Açú Basin , 26°46'22''S, 49°11'26''W; 276 m a.s.l., 18.viii.1999, G. Bond-Buckup and L. Buckup col. ( MZUSP 20463 ).

Paratypes: 2 m, 1 f with juveniles, 2 j, same data as holotype ( UFRGS 2679 P) ; 1 m, same data as holotype, 02.i.2001, F. Faraco col. ( UFRGS 2993 ) ; 4 m, 1 f, Campo Alegre , Joinvile, i.2002 ( UFRGS 3262 ).

Diagnosis.—Antero-lateral spine of carapace extending beyond base of cornea; protogastric lobes present; extraorbital sinus absent, rostrum triangular, slightly ligulate, slightly recurved distally, lacking carena on distal third, outer proximal margin of movable finger of cheliped with lobe; palmar crest of cheliped subrectangular; anterior angle of ventral margin of epimeron 2 unarmed; inner margin of ventral surface of ischium of cheliped with a distal tubercle. Description.—Carapace moderately compressed dorsoventrally, area of gastric region more elevated, dorsal surface scabrous, covered with punctae. Front wide; LPC/LF ratio of holotype male 1.87.

Rostrum triangular, slightly ligulate, elevated in median portion, slightly recurved distally, without carena on distal third. Sub-rostral process developed; in profile, rostrum with ventral portion deeper than dorsal. Rostral carena begins between protogastric lobes, with two parallel rows of scales that do not reach apex; excavated in median portion. Lateral margins of rostrum with small scales.

Orbits wide, deep, without orbital spine. Orbital margin with small sparse scales. Extraorbital sinus lacking.

Antero-lateral angle of carapace projecting anteriorly in a spine, which extends beyond base of cornea. Outer and inner margins of antero-lateral lobe with sparse scales. First hepatic lobe delimited anteriorly by a distinct fissure; lateral margin with scales; second and third hepatic lobes not delimited, with only a slight indication; lateral margins with scales.

Epigastric prominences little pronounced, surface irregular, of indefinite shape, elongated toward base of first hepatic lobe, with sparse scales. Protogastric lobes moderately elevated, anterior margin marked by row of scales.

Transverse dorsal line sinuous. Areola subquadrate to subrectangular. CA/LA ratio of holotype male 1.5.

Epibranchial area triangular, with an apical tubercle followed by scales. Lateral margins of anterior and posterior branchial areas with subequal scales.

Anterior angle of ventral margin of epimeron 2 unarmed, with only small scales; ventrolateral margin slightly convex; posterior angle of ventral margin obtuse, unarmed. Epimera of third to sixth segments projecting; on third and fourth the lateral projection ornamented with a small apical scale.

Telson divided by longitudinal suture.

Anterior extremity of third sternite truncate, projected between the coxae of the exopods of the third maxillipeds. Fourth thoracic sternite elevated in median region, without ornament, lateral margins slightly recurved.

Chelipeds subequal, hand subrectangular. Smaller chela delicate in appearance, elongated, covered by scales. Larger cheliped with more globose appearance, palm slightly more inflated in posterolateral region, covered with corneal scales. Palmar crest subrectangular, with margin ornamented with scaliform tubercles, indicating lobes. Pre-dactylar lobe forming asmall angle with anterior margin of propodus, ornamented with scales. Fingers slender, covered by setae, scales, and scaliform tubercles. Proximal outer margin of movable finger with distinct lobe tipped with scales. Prehensile margins of fingers with scaliform denticles on their entire length, and with pronounced fitted opposed lobular teeth. Dorsal surface of carpus scabrous, with scales; inner margin with four spines, with distalmost spine being most developed; these spines with sparse scales on the lateral margins; small spine between the distal spine and the inner antero-lateral angle of the carpus; inner antero-lateral angle sub-obtuse, with apical spine; anterodorsal margin with scales. Distal part of dorsal surface with depression parallel to distal margin. Carpal crest pronounced, more elevated in proximal region, with clumps of three to five scales on elevations of crest; outer ventral angle of carpus with scales; ventral surface with one conical spine and tufts of setae. Dorsal margin of merus of cheliped with one spine, remainder of margin with scaliform tubercles; antero-dorsal margin with scales. Lateral surfaces with sparse punctae. Inner ventral margin of merus with one distal spine followed by scaliform tubercles; outer ventral margin with pronounced distal tubercle followed by scales. Dorsal margin of ischium with one spine; inner margin of ventral surface with small distal spine, followed by several spines along margin. Dorsal margin of dactylus, propodus, and carpus of second, third, and fourth pereiopods with rows of setae, scales, and scaliform tubercles arranged in longitudinal series, lending the surface a pubescent appearance.

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Variations.—The rostrum is more excavated in the larger paratypes, and the larger chela is more globose.

Morphometry.—Holotype male with LC 16.89 mm. Paratypes (n = 5) with mean LC 13.60 mm. Asmall-sized species. LPC/LF ratios of paratypes (n = 3) ranging from 1.50 to 1.90.

CA/LA ratios of paratypes varying little, from 1.7 to 1.8.

Distribution.—Brazil: State of Santa Catarina, Rio Itajaí- Açú Basin.

Remarks.—The Bayesian phylogenetic analysis of the molecular data showed that A. pomerana belongs to Clade Cas defined in Pérez-Losada et al. (2004). With regard to the relationship to other species, this was considered a sister-species of A. leptodactyla ( Fig. 3 ), which occurs in the Rio Uruguay basin on the high plateau of Rio Grande do Sul and Santa Catarina. Nevertheless, there are several morphological differences between these two species. A. pomerana does not bear an extra-orbital sinus, whereas A. leptodactyla possesses this character. The rostrum of A. pomerana is only slightly ligulate, recurved, lacks a carina on the distal third, and ends without a spine on the tip; whereas this structure in A. leptodactyla is of medium length, and its distal end terminates in a spine. A. pomerana has wide chelipeds; its sister species has narrow chelipeds.

The relationship of A. pomerana with species found in the Rio Uruguay basin, which at present has no direct connection to the Rio Itajaí basin, can be attributed to a common geological origin of the two basins, which is related to the formation of the Serra Geral in southern Brazil ( Ribeiro, 2006). The uplift of the Serra Geral separated the Uruguay and Itajaí-Açú rivers creating the opportunity for new species to arise through allopatric speciation.

Morphologically, A. pomerana resembles A. marginata Bond-Buckup and Buckup, 1994 , in some aspects, particularly in the slightly arched antero-lateral border of the carapace. However, A. pomerana has a subrectangular palmar crest, and A. marginata has no palmar crest.

Biology.—Unknown.

Etymology —Named in honor of the inhabitants of Pomerode, the type-locality of the species.

Figures

Fig. 2. Aegla pomerana, n. sp. a: male holotype (MZUSP 20463), dorsal view; b: precervical portion of carapace, lateral view; c: ischium of cheliped, ventral view; d: third and fourth sterna, ventral view; e: second pleomere epimeron

Fig. 3. Maximum likelihood and Bayesian trees as modified from Pérez-Losada et al. (2009). Posterior probabilities (if> 0.5) are indicated for each clade. Aegla pomerana and Aegla muelleri are presented in bold