Aegla muelleri, 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 : 498-501

Aegla muelleri n. sp. Bond-Buckup and Buckup

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Type-material.— Holotype male, Brazil, state of Santa Catarina, Indaial, Serra do Itajaí National Park, Rio Itajaí- Açú basin , 27°01'24''S, 49°09'06''W; ii.2006, H. Boos col. ( MZUSP 20464 ).

Paratypes: 1 m, 6 f, same data as holotype ( UFRGS 4117 P); 2 m, 2 f, same data as holotype, 11.v.2001, H. Boos and G. Bond-Buckup col. ( UFRGS 2982 ); id. , 2 m, 21.ix.2002 ( UFRGS 3570 ); id., juvenile ( UFRGS 3571 ); 1 m, Cascata do Rio Passa Quatro , Monte Castelo, Rio Itajaí-Açú basin , 26o28'14''S, 50°11'59''W; 24.x.2000, A.A.P. Bueno, G. Bond-Buckup, C. Jara and M. Pérez- Losada col. ( UFRGS 2979 ); id., ib., ib. , 11 m, 11 f, 1 f ov, 5 j ( UFRGS 2980 ).

Material Examined.— Brazil, Santa Catarina, Espingarda Creek , Serra do Itajaí National Park, Rio Itajaí-Açú basin , 27°01'24.1''S, 49°09'6.7''W; 20.vi.2002, H. Boos and K. Schacht col., 4 dissected specimens, ( UFRGS 3385 ) .

Diagnosis.—Antero-lateral spine of carapace reaching base of cornea; protogastric and epigastric lobes absent; extraorbital sinus absent, rostrum triangular, tapered, slightly recurved distally, carinate, proximal outer margin of movable finger of cheliped without lobe; palmar crest of cheliped small, subrectangular; anterior angle of ventral margin of epimeron 2 with small scale; inner margin of ventral surface of ischium of cheliped with distal scaliform tubercle.

Description.—Carapace strongly compressed dorsoventrally, dorsal surface scabrous, covered by punctations and scales; anterior dorsal region delimiting base of rostrum by V-shaped depression.

Front wide; LPC/LF ratio of holotype male 1.73.

Rostrum long, triangular, tapering, slightly recurved distally, carinate, distal part of rostrum slightly recurved. Sub-rostral process well developed; in profile, ventral portion of rostrum deeper than dorsal portion. Rostral carina begins at height of orbits, with two juxtaposed rows of scales that reach to apex; carina elevated in middle portion and very low in distal third. Lateral margins of rostrum scabrous.

Orbits wide and deep, orbital spine indicated by an incision. Orbital margin scabrous. Extra-orbital sinus absent.

Antero-lateral angle of carapace projecting anteriorly in a spine, extending beyond base of cornea. Outer and inner margins of antero-lateral lobe with sparse scales. First hepatic lobe delimited anteriorly by small incision; lateral margin smooth; 2 nd hepatic lobe with small indication, and 3rd not delimited; lateral margins scabrous. Epigastric prominences lacking, surface scabrous. Protogastric lobes lacking, without indication.

Transverse dorsal line sinuous. Areole quadrate. CA/LA ratio of holotype male 1.34.

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

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Anterior angle of ventral margin of epimeron 2 unarmed, indicated by smallscale; ventro-lateral margin slightly convex; posterior angle of ventral margin obtuse, unarmed. Epimera of third to sixth segments projected; on the third and fourth the lateral projection ornamented with a small apical scale.

Telson divided by longitudinal suture.

Anterior extremity of third sternite triangular, projecting between coxae of exopods of third maxillipeds. Fourth thoracic sternite slightly elevated in medial region, without ornament, lateral margins slightly recurved.

Chelipeds subequal, hand sub-rectangular. Chelae with delicate appearance, covered by scales. Larger cheliped slightly more robust. Palmar crest subrectangular, with margin ornamented with scaliform tubercles, indicating lobes. Pre-dactylar lobe forming small angle with anterior margin of propodus, scabrous. Fingers slender, covered by sparse scales and setae. Outer proximal margin of movable finger without lobe. Prehensile margin of fingers with scaliform denticles along its entire length, and with fitted opposed lobular teeth. Dorsal surface of carpus scabrous, with scales; inner margin with three spines, the distalmost spine being the most developed of them; these spines without scales on their lateral margins; inner anterolateral angle projecting in apical spine; anterodorsal margin with scales. Dorsal surface distally with small depression parallel to distal margin. Carpal crest distinct, more elevated in proximal region; medial and distal portions with scales clumped in groups of three to five on elevations of crest; outer ventral angle of carpus obtuse, unarmed; ventral surface with small conical spine. Dorsal margin of merus of cheliped with elevations tipped with scales, which decrease in size proximally, followed by long setae; anterodorsal margin with sparse scales. Lateral surfaces with punctae and scales. Inner ventral margin of merus with a distal spine followed by scaliform tubercles and scales; prominent distal tubercle followed by scales on outer ventral margin. Dorsal margin of ischium with conical tubercle and long setae; inner margin of ventral surface of ischium elevation tipped with scale.

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Dorsal margins of dactylus, propodus, and carpus of second, third, and fourth pereiopods with rows of setae and scales arranged in longitudinal rows. Dorsal margins of second, third, and fourth pereiopods covered with long setae, lending the surface a pubescent appearance.

Variations.—In some paratypes, the protogastric lobes are delimited anteriorly by sparse scales, although these are lacking in other specimens. Proximal outer margin of movable finger, in some specimens, bears scales suggesting a lobe. Other paratypes do not possess fitted opposed lobular teeth on the prehensile margin of the fingers, but only scaliform denticles on their entire length. The lot UFRGS 2979 has more-developed tubercles on the pereiopods, and the palmar crest is slightly more distinct. This is a small-sized species, comparable to A. violacea Bond-Buckup and Buckup, 1994 and A. leptodactyla .

Morphometry.—Holotype male with LC 12.20 mm. The ovigerous female measured 13.29 mm LC. The mean LC of 25 paratypes was 11.52 mm, ranging from 8.0 to 15.33 mm.

LPC/LF ratio of paratypes (n = 10) ranging from 1.71 to 1.91, i.e., characterizing a wide front. CA/LA ratio of paratypes (n = 11) ranging from 1.14 to 1.32.

Etymology.—Named in honor of Fritz Müller, the first scientist to describe an aeglid from Brazilian waters.

Biology.—Unknown.

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

Remarks.—The new species A. muelleri resembles A. plana Buckup and Rossi, 1977 in the dorsoventrally compressed cephalothorax and the absence of the epigastric and protogastric lobes. However it is distinguished from A. plana by the shape of the chelipeds, which are wider in A. plana ; by the configuration of the spines of the carpus; and by the shape of the palmar crest, which is more developed in A. plana . This latter species also possesses an extraorbital spine, which is lacking in A. muelleri .

The total length of the cephalothorax of the paratypes (n = 7) reached only 13.43 mm, showing it to be a small-sized species.

The species occurs in sympatry with A. jarai in the Ribeirão Garcia in the Parque das Nascentes, an environ- mental preservation area that is among the few localities that shelter species in Atlantic Forest.

The Bayesian phylogenetic analysis of the molecular data showed that A. muelleri belongs to Clade Eas defined in Pérez-Losada et al. (2004). Aegla muelleri has a sister relationship to A. leptochela ( Fig. 3 ), with which it shares the delicate form of the chelipeds and the convexity of the carapace. However, the two species differ in relation to the antero-lateral spine of the carapace, which in A. muelleri reaches the base of the cornea, and in A. leptochela does not. In A. muelleri , the extra-orbital sinus and the lobe of the movable finger are lacking, and the palmar crest is subrectangular; whereas in A. leptochela the extra-orbital sinus as well as the lobe of the movable finger are present, and the palmar crest is lacking.

Figures

Fig. 4. Aegla muelleri, n. sp. a: male holotype (MZUSP 20464), 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