Aegla marginata Bond-Buckup & Buckup, 1994

Bueno, Sérgio Luiz De Siqueira, 2017, Taxonomic review of Aegla marginata Bond-Buckup & Buckup, 1994 (Decapoda, Anomura, Aeglidae) with description of a new species, Zootaxa 4323 (4), pp. 519-533 : 521-523

Aegla marginata Bond-Buckup & Buckup, 1994

( Figs 2 ; 4A; 5A; 6A, C, E; 7A, C, E; 8A–C; 9A, C)

Aegla marginata Bond-Buckup & Buckup, 1994: 218 , fig. 34 [male holotype], 70d [distribution map].— Bond-Buckup & Buckup, 1994 [pro parte; specimens from Morretes– Paraná and Santa Catarina only].— Trevisan et al. 2012: 78 [sexual dimorphism].— Boos et al. 2012: 1023 [distribution].

Type material. Holotype: Male ( CLE 18.80 mm), second to fourth right pereiopods missing, Brazil, Paraná, Litorânea Basin, Morretes, Morcego stream , J. Caetano coll., November 1971, geographic coordinates and altitude unknown (MHNCI 759H). Paratypes: 1 male ( CLE 17.52 mm), same data as holotype , J. Caetano coll., November 1971 ( MHNCI 759 P); 3 males, 5 females and 2 juveniles (not measured), Brazil, Santa Catarina, Litorânea Basin, Joinville, Tronn stream (tributary of Prata river ) , G. Sato coll., 26 June 1985, geographical coordinates and altitude unknown (MZUSP 20455).

Other material examined. 9 males ( CLE 15.43–18.81 mm), Brazil, Paraná, Litorânea Basin, Morretes, Santuário Nhundiaquara, unnamed stream, 25°25’33.9”S, 048°53’25.4”W, altitude: 72.2 m, J.C.B. Moraes, S.L.S. Bueno and J.R. Debastiani-Júnior coll., 15 April 2014 ( MZUSP 34808, including SEM voucher).

Geographical distribution. This species is only known from small streams from low altitudes of southern Brazil (Litorânea Hydrographic Basin): Morretes (state of Paraná), and Joinville (state of Santa Catarina).

Diagnosis. Rostrum narrow at base. Extra-orbital sinus deep. Anterolateral spines slightly inclined upward. Epigastric prominences poorly pronounced. Protogastric lobes pronounced, with one corneous scale each. Anterior margin of first hepatic lobe and axis of rostrum oriented with respect to each other about 90°. Hepatic lobes well demarcated. Transverse dorsal linea nearly straight mesially, sinuous laterally. Areola sub-rectangular. Cardiac area trapezoidal. Anterolateral angle and lateral margin of epibranchial area with small corneous scales. Third thoracic sternite abruptly constricted subterminally. Major cheliped propodus with palmar crest rudimentary, low, poorly jagged, outer surface not excavated. Anterolateral angle of second abdominal epimeron and ventral angles of third and fourth abdominal epimera unarmed. Sexual tube long, narrow. Uropods narrow-shaped. Telson with anterolateral and posterolateral margins poorly differentiated, posterolateral margin straight.

Redescription of the holotype. Carapace moderately convex, gastric region swollen, dorsal surface poorly scabrous, covered with punctations. Rostrum triangular, blunt distally, base narrow-shaped (RBW/LMR = 0.88), straight, extending beyond distal apex of compound eyes, corneous scales on lateral margins and tip. Rostral carina beginning at level of protogastric lobes, extending to apex, with corneous scales. Subrostral margin markedly high ( Fig. 5A ). Subrostral process well developed, occupying posterior half of subrostral margin, oriented downward and forward, tip rounded, anterior and posterior margins forming distinct acute angle relative to each other ( Figs 2 , 4A , 5A , 6A ).

Eyestalk and cornea well developed. Orbital and extra-orbital sinuses deep. Orbital sinus U-shaped, with row of long setae subventrally. Orbital spines well developed, tip rounded, with small terminal corneous scale. Anterolateral spines rounded apically with small corneous scales terminally, slightly inclined upward, reaching basal margin of cornea ( Figs 2 , 4A ).

Epigastric prominence poorly pronounced, one corneous scale on right prominence. Protogastric lobe pronounced, one corneous scale on each lobe. Gastric area moderately swollen relative to hepatic lobe and rostrum in lateral view. Gastric pits inconspicuous ( Figs 2 , 4A , 5A ).

Anterior margin of first hepatic lobe and axis of rostrum oriented with respect to each other about 90° ( Fig. 4A ). Hepatic lobes well demarcated, flat-topped ( Figs 4A , 5A ). Lateral margins of hepatic lobes with some small corneous scales and sparse small setae.

Transverse dorsal linea nearly straight mesially, sinuous laterally. Areola sub-rectangular (ratio = 1.79), cardiac area trapezoidal (ratio = 1.64) ( Fig. 2 ).

Epibranchial area shortened, anterolateral angle blunt, with corneous scale, lateral margin with row of small corneous scales ( Figs 2 , 6C ).

Third thoracic sternite with scattered long setae, abruptly constricted subterminally. Fourth thoracic sternite with anterolateral angles produced anteriorly, corneous scales absent ( Fig. 6E ).

Chelipeds unequal in size. Major cheliped dactylus ( Figs 2 , 7A, C, E ): dorsal margin and outer surface with small corneous scales, inner surface smooth. Proximal lobe on dorsal margin rudimentary. Cutting margin with rudimentary lobular basal tooth, flattened corneous scales followed by row of wide corneous scales up to distal end. Row of small tufts of long setae next to cutting margin. Propodus: outer surface granulate, palm high (ratio = 3.97). Palmar crest rudimentary, low, poorly serrated, outer surface not excavated, covered by corneous scales. Cutting margin of fixed finger with lobular basal tooth moderately developed, flattened corneous scales followed by row of wide corneous scales up to distal end. Inner and outer surfaces of fixed finger with rows of tufts of long, simple setae next to cutting margin. Carpus: dorsal margin with subterminal lobe well developed. Lobe blunt, with scattered small setae, four small corneous scales apically, followed by subdistal spine and two subproximal tubercles, most subproximal one devoid of terminal corneous scale. Inner surface of carpus with one distinct tubercle with acute corneous scale terminally, scattered small setae near dorsal margin. Outer surface with carpal ridge poorly pronounced, small corneous scales and setae. Merus: dorsal margin with small corneous scales, devoid of tubercles. Dorsolateral edge with nine, blunt tubercles decreasing in size posteriorly. Ventromesial edge with one distal spine, three tubercles decreasing in size posteriorly, most proximal one naked, remaining tubercles provided with one corneous scale each. Ventrolateral border of merus with two tubercles, distal one provided with terminal corneous scale, subdistal one naked. Ischium: dorsolateral edge with one distal spine with minute corneous scale. Ventromesial border with row of four low tubercles with small setae and terminal corneous scale, proximal tubercle with setae only. Ventrolateral border smooth.

Minor cheliped similar to major cheliped except as noted ( Fig. 2 ). Dactylus: cutting margin formed by narrow corneous scales. Propodus: cutting margin of fixed finger formed by row of narrow corneous scales up to distal end, lobular basal tooth absent. Carpus: dorsal margin provided with three spines, subdistal strongest, proximal smallest, with minute corneous terminal scale. Merus: dorsolateral edge with ten blunt tubercles decreasing in size proximally. Ventromesial edge with one spine and five tubercles. Ischium: ventromesial border with five low tubercles, distal-most largest, proximal-most naked.

Second, third and fourth pereiopods morphologically similar. Dactylus with several rows of setal tufts and small corneous scales on general surface. Propodus and carpus with scattered, short setae mainly along dorsal margin, small corneous scales along dorsal margin. Merus and ischium with scattered, short and long setae concentrated along dorsal margin.

Fifth pereiopods reduced, chelate. Dactylus small, flattened, forming setose minute chela with propodus. Sexual tube long, narrow ( Fig. 8A–C , topotype).

Pleopods 2–5 rudimentary, showing as buds.

Anterolateral angle of second abdominal epimeron and ventral angles of third and fourth abdominal epimera well defined, unarmed. Anterior margin of second abdominal epimeron almost straight ( Fig. 9A ).

Uropods well developed, narrow ( Fig. 9C ).

Telson with anterolateral and posterolateral margins poorly differentiated, posterolateral margin straight ( Fig. 9C ).

Variations. In Aegla marginata sensu stricto, the rostral length/width ratio is 0.97 ± 0.06; n = 9. In some specimens, the anterolateral spines do not reach to the basal margin of cornea, and the anterolateral and posterolateral margins of the telson are well differentiated. In the male paratype (MHNCI 759P, CLE 17.52 mm) and topotypes (MZUSP 34808) the subrostral process is narrower with tip oriented anteriorly ( Fig. 6A ).

Remarks. Bond-Buckup & Buckup (1994) described Aegla marginata based upon several males and females from two isolated hydrographic basins, the Ribeira de Iguape Basin and the Litorânea Basin (also known as Coastal Basin). Aegla marginata Bond-Buckup & Buckup, 1994 is restricted herein to the southern population from the Litorânea Basin (Paraná and Santa Catarina, Brazil), whereas a new species is described for the northern population from the Ribeira de Iguape Basin, Aegla quilombola n. sp. The morphological differences between the two species are discussed below.

Figures

FIGURE 2. Aegla marginata Bond-Buckup & Buckup, 1994 sensu stricto, male topotype, CLE 17.86 mm (MZUSP 34808). Scale bar: 3.0 mm.

FIGURE 4. A, B. Dorsal view of the anterior region of the cephalothorax. (A) Aegla marginata sensu stricto, male holotype, CLE 18.80 mm (MHNCI 759). (B) Aegla quilombola n. sp., male holotype, CLE 15.70 mm (MZUSP 34809). Note: A (thick arrows) well defined hepatic lobes (lobes poorly defined in Aegla quilombola n. sp.); deep, wide extraorbital sinus (thin arrow) (sinus much shallower and narrower in Aegla quilombola n. sp.). Scale bars: 1.0 mm.

FIGURE 5. A, B. Lateral view of anterior region of the cephalothorax. (A) Aegla marginata sensu stricto, male holotype, CLE 18.80 mm (MHNCI 759). (B) Aegla quilombola n. sp., male holotype CLE 15.70 mm (MZUSP 34809). Note: A: (i) epigastric prominences low and flattened (thick arrow) (prominences distinctly higher and swollen in A. quilombola n. sp.); (ii) protogastric lobes more produced in A. marginata (thin arrow) (lobes lower in A. quilombola n. sp.); (iii) large height of ventral surface of rostrum (vertical bar showing upper and lower limits) (height markedly lower in A. quilombola n. sp.). Scale bars = 1.0 mm.

FIGURE 6. A, C, E. Aegla marginata sensu stricto, A, male topotype CLE 17.86 mm (MZUSP 34808). C, E, male holotype, CLE 18.80 mm (MHNCI 759). B, D, F. Aegla quilombola n. sp., male holotype CLE 15.70 mm (MZUSP 34809). (A) (B) Rostral region of the cephalothorax in lateral view. (C) (D) Epibranchial area. (E) (F) Third and fourth thoracic sternites. Note: A, long subrostral process (arrow) (markedly shorter in Aegla quilombola n. sp.). Scale bars: A, B, D, F = 0.5 mm; C = 0.2 mm; E = 1.0 mm.

FIGURE 7. A, C, E. Aegla marginata sensu stricto, male holotype, CLE 18.80 mm (MHNCI 759). B, D, F. Aegla quilombola n. sp., CLE 15.70 mm (MZUSP 34809). (A) (B) Palmar crest of major cheliped. (C) (D) Carpus of the major cheliped. (E) (F) Ischium of major cheliped. Note: C and D, low carpal ridges of major cheliped in A. marginata compared to more pronounced condition in Aegla quilombola n. sp.; E and F, different density of tubercles on cheliped ischia (higher in A. marginata than in A. quilombola n. sp.). Scale bars = 1.0 mm.

FIGURE 8. A – F. Sexual tube. A – C. Aegla marginata sensu stricto, male topotype, CLE 16.35 mm (MZUSP 34808). D – F. Aegla quilombola n. sp. male paratype, CLE 9.46 mm (MZUSP 34812). (A) (D) Dorsal view. (B) (E) Lateral view. (C) (F) Ventral view. Scale bars: A – C = 200 µm; D – F = 100 µm.

FIGURE 9. A, C. Aegla marginata sensu stricto, male holotype, CLE 18.80 mm (MHNCI 759). B, D. Aegla quilombola n. sp., male holotype, CLE 15.70 mm (MZUSP 34809). (A) (B) Posterior and anterior regions of carapace and abdomen in dorsal view. (C) (D) Fifth and sixth abdominal segments, uropods and telson. Note: B, curvature (arrows) on anterior margin of the second abdominal segment more pronounced in A. quilombola n. sp. Scale bars: A, C, D = 2.0 mm; B = 1.0 mm.