Pachycheles coelhoi, Ferreira & Tavares, 2019

Ferreira, Luciane Augusto De Azevedo & Tavares, Marcos, 2019, A review of the records of Pachycheles rugimanus A. Milne-Edwards, 1880 (Crustacea: Decapoda: Anomura: Porcellanidae) from Brazil, with the description of a new species, Zootaxa 4568 (1), pp. 185-193 : 186-192

Pachycheles coelhoi sp. nov.

( Figs. 1 A–K, 2A–C, 4A,B)

Pachycheles rugimanus . — Coelho 1964: 255; Veloso & Melo 1993: 173, 178 (in part); Melo 1999: 227, 242, figs. 163, 164; Coelho et al. 2007: 1, tab 4; Ferreira & Melo 2016: 183 . [Not Pachycheles rugimanus A. Milne-Edwards, 1880 ].

Type material. Holotype: male cl 6.4 mm, cw 5.9 mm ( MOUFPE 7491 ), Brazil, Amapá, Cabo Orange, Project Geomar III, R/V "Almirante Saldanha", Stn 208, 04°52'N: 50°31'30"W, 1971, 118 m. Paratype: female cl 4.7 mm, cw 4.4 mm ( MZUSP 39043 ), same data as holotype .

Comparative material. Pachycheles ackleianus A. Milne-Edwards, 1880: 2 males, cl 3.6 mm, cw 4.2 mm and cl 3.1 mm, cw 3.8 mm ( MZUSP 12892 , ex- MOUFPE 3082 ), Brazil, Paraíba, Projeto Algas, Stn 86A, 6°36'S– 34°47'W, 26 m.

Pachycheles rugimanus A. Milne-Edwards, 1880: 3 males, largest cl 8.1 mm, cw 7.8 mm; smallest cl 7.3 mm, cw 7.1 mm; 1 ovigerous female, cl 7.9 mm, cw 8.4 mm ( USNM 188445 ), United States, South Carolina, R/ V Dolphin, Stn MARMAP 791041, 32°50'06"N– 78°36'18"W, 21 September 1979, 35 m. 2 males , cl 6.2 mm, cw 5.9 mm and cl 5.8, cw 5.6 mm, 2 ovigerous females, cl 7.1 mm, cw 7.2 mm and cl 7.2 mm, cw 7.4 mm ( USNM 150684 ), Georgia, Sapelo Island , off Sea Buoy, Stn 373, 30°40'43"N– 80°06'07"W, M. Gray coll., 12 September 1963, 50– 59 m.

Pachycheles velerae Haig, 1960: 1 male, cl 5.4 mm, cw 4.9 mm ( USNM 110551 ), Costa Rica, Cocos Island , Chatham Bay, 5°35'50"N– 86°58'55"W, Allan Hancock Expedition, R / V Velero, 14 January 1938, 73– 86 m.

Distribution. Currently known only from Cabo Orange, Amapá ( Brazil).

Description. Carapace subcircular, longer than broad in both males and females, quite rugose dorsally, with scattered flattened tubercles dorsally. Frontal region prominent, rugose, slightly depressed on midline. Frontal width less than half of maximum carapace width. Frontal margin distinctly granulate, trilobate in dorsal and frontal views, devoid of setae; median lobe prominent, rounded, overreaching lateral lobes; lateral lobes broad, rounded. Outer orbital angle terminating in well-developed, long teeth. Orbit with rugose margin. Carapace lateral margin well-defined, wrinkled. Epibranchial region slightly swollen. Cervical groove well defined, ending in distinct notch anteriorly. Posterior branchial region with long, transverse rugae; posterolateral margin gently rounded, devoid of setae. Branchiostegite distinctly rugose, not pubescent, divided into calcified plates of different sizes; anterior plate distinctly larger than posterior; sometimes with several much smaller plates posteriorly.

Thoracic sternite 3 trilobate; median lobe broad, rounded, unarmed, not overreaching lateral lobes; lateral lobes narrow, subtriangular. Sternites 4–7 broad, sutures between sternites incomplete, distinct only laterally. Sternite 8 anterior margin slightly convex, posterior margin concave.

Ocular peduncle short; cornea large, rounded, dilated.

Antennular basal segment large, with 2 small distomesial spines. Segments 2–3 unarmed, subcylindrical; segment 3 broadened distally.

Antennal peduncular segments slightly rugose, short. Segment 1 subtriangular, membranous dorsally, calcified ventrally. Segments 2–3 about 2/3 length of segment 3, with well-developed distomesial tubercle. Segment 4 mesial surface with 2 or 3 well-developed granules. Segment 5 about half length of segment 4.

Mxp3 rugose on external surface. Exopod reniform, reaching about half of total length of merus; flagellum well developed. Ischium lateral lobe distinct, well-developed, separated by deep V-shaped incision. Merus as long as ischium; mesial lobe broad, tip rounded, with serrate margin.

P1 similar between male and female; right and left sides unequal in size but similar in armature, robust, eroded, distinctly granulate dorsally; ventral surface with flattened tubercles. Merus about 1/3 length of carpus; mesial lobe subtriangular, well-developed, granulate; 2–4 distal spines well-developed ventrally. Carpus as long as palm; mesial margin with 3–4 granulate, strongly projecting teeth, progressively decreasing in size distally. Dorsal surface of carpus and propodus with 3 pronounced, longitudinal carinae and series of transverse, discrete ridges between the longitudinal carinae. Palm with large, granular tubercle near base of pollex. Fixed finger about 1/3 length of propodus. Dactylus about 2/3 length of propodus. Cutting edges of fingers furrowed, granulate, devoid of setae. Tip of fingers curved, closing tightly.

Walking legs decreasing in size from P2–4, robust, rugose, fringed with dense, short setae on margins, especially on carpi and propodi, and with scattered long setae. Carpi about 2/3 length of P2–4 meri, lateral surface with 2 low, longitudinal, parallel carinae dorsally; dorsal margin with 1 to 3 discrete, dorsodistal spines. Propodi as long as meri, each with 4 spines on ventral surface: 2 spines along ventral margin, 2 on distoventral margin near articulation with dactylus. Dactyli about half length of propodi, each with row of 4 well-developed spines ventrally.

P5 short, ischium 1/4 of length of merus; merus slightly longer than carpus; propodus about 1/3 of length of carpus; dactylus about 1/3 of length of propodus.

Male and female pleon subrectangular, surface of each somite smooth dorsally, lateral margins with short, plumose setae. Male gonopods well developed on somite 2. Female pleopods well developed on somites 3–5. Uropods broad, reaching to distal margin of telson. Telson broader than long, subdivided into 5 plates, nearly smooth on external surface.

Etymology. The new species is named in honour of the late Prof. Petrônio Alves Coelho (Universidade Federal de Pernambuco) in recognition of his outstanding contributions to the taxonomy of the decapod crustaceans in Brazil.

Remarks. Pachycheles coelhoi sp. nov. superficially resembles P. rugimanus ( Figs. 2 D–F, 4C, D) and P. velerae ( Figs. 3 D–F, 4E, F). However, the new species can be separated from both, P. rugimanus and P. velerae , in that: (1) the major and minor P1 fingers are similar in shape; the fingers have nearly straight cutting edges and are interlocked subdistally, with the dactyli closing tightly against the fixed fingers, Figs. 1G, H , 2C , 4A, B (in the other two species, the major and minor P1 fingers are unequal in shape; the major P1 fingers leave a broad hiatus when closed and are not interlocked distally, with the dactylus strongly curved to ventral side, Figs. 2F , 3F , 4 C-F); (2) the dorsal surface of the major P1 finger is heavily tuberculated rather than nearly smooth in P. rugimanus and P. velerae ( Figs. 2F , 3F , 4C, E ).

Pachycheles coelhoi sp. nov. is further differentiated from P. rugimanus by: (1) the carapace front being slightly deflexed and markedly trilobate in dorsal view; the median lobe being strongly projected, distinctly overreaching the tip of cornea in dorsal view and separated from the lateral lobes by broad concave margins ( Figs. 1A , 2A ) (versus carapace front markedly deflexed, scarcely trilobate; the median lobe is very low, poorly projected, barely overreaching the tip of cornea and separated from the lateral lobes by nearly straight margins in P. rugimanus , Fig. 2D ); (2) the median lobe of the thoracic sternite 3 is rounded and separated from the lateral lobes by shallow, gently concave margins ( Figs. 1K , 2B ) rather than distinctly subtriangular and separated from the lateral lobes by straight, laterally V-shaped margins in P. rugimanus ( Fig. 2E ).

In addition to the above mentioned distinctions, P. coelhoi sp. nov. differs from P. velerae in that: (1) the frontal, protogastric and hepatic regions of the carapace are strongly striated transversally, and the epibranchial region is coarsely squamose ( Figs. 1A , 2A ) (in P. velerae the frontal, protogastric and hepatic regions are nearly smooth and the epibranchial region have few minute squamae ( Fig. 3D ); (2) the major P1 fingers cutting surfaces are markedly hollowed along the longitudinal line, with incisor teeth along hollows, and the dactylus cutting edge has no molar tooth ( Figs. 1H , 2C , 4A, B ), whereas in P. velerae the dactylus and fixed finger are hollowed out only along the distal half and only slightly hollowed distally, respectively. The dactylus and fixed finger each have two longitudinal, subparallel rows of molariform flat teeth along the hollow axes and the dactylus has one strong molar tooth subproximally (considered an autapomorphy of P. velerae by Harvey 1998) ( Figs. 3F , 4E, F ); (3) the major P1 propodus dorsal surface has a wide, high, heavily tuberculated, elongated upper bulge ( Fig. 4A ), versus a narrow, low, rather smooth, elongated upper ridge in P. velerae ( Fig. 4E ); (4) the major P1 propodus dorsal surface has an elongated, large, high, heavily tuberculated axial bulge and is provided with discrete, transverse ridges between its upper margin and the upper bulge ( Fig. 4A ), whereas in P. velerae , the axial bulge is rounded, far smaller and lower ( Fig. 4E ) and there is a net of ridges of different sizes forming a reticulated, wrinkled pattern instead of transverse ridges ( Fig. 4E ). The more elongate carapace and projecting front, the sparse setation on the chelipeds and carapace, and the dense plumose setae on pereopods 2–4 were also regarded as additional autapomorphies of P. velerae by Harvey (1998), but these characters are shared with P. coelhoi sp. nov.

In the past, Pachycheles coelhoi sp. nov. has been confused with P. ackleianus ( Fig. 3 A–C). The two species are somewhat similar, but can be easily separated in that: (1) the carapace is longer than broad in males and females ( Figs. 1A , 2A ), whereas in P. ackleianus , it is distinctly broader than long in males and females ( Fig. 3A ); (2) the front is slightly deflexed and distinctly trilobate in dorsal view ( Figs. 1A , 2A ), versus distinctly deflexed and nearly straight in dorsal view in P. ackleianus ( Fig. 3A ); (3) the P1 carpus and propodus are distinctly granulate and the carpus has 3 pronounced, longitudinal carinae and a series of transverse, discrete ridges between the longitudinal carinae ( Figs. 1G, H , 2C , 4A, B ), whereas in P. ackleianus , the carpus and propodus are covered with flattened tubercles grouped together in longitudinal rows ( Fig. 3C ); and (4) the male gonopods are present on somite 2 versus absent in P. ackleianus .

Haig (1960) and Harvey (1998) put forward a number of distinguishing characters between P. velerae and P. rugimanus . Additional characters differentiating P. velerae from P. rugimanus include the poorly defined carapace regions ( Fig. 3D ), compared to well defined in P. rugimanus , especially the protogastric and epibranchial regions ( Fig. 2D ), and the anteriorly trilobate thoracic sternite 3 with the median lobe rounded and separated from the lateral lobes by shallow, gently concave margins ( Fig. 3E ), whereas in P. rugimanus , the median lobe is distinctly subtriangular and separated from the lateral lobes by straight, laterally V-shaped margins ( Fig. 2E ).

Harvey (1998) considered that P. velerae and P. rugimanus are sister taxa on opposite sides of the Isthmus of Panama based on an unpublished phylogenetic analysis of Pachycheles and Neopisosoma . Future phylogenetic analysis might well reveal that P. velerae is actually sister to P. coelhoi sp. nov.

Figures

FIGURE 1. Pachycheles coelhoi sp. nov., male holotype, cl 6.4 mm, cw 5.9 mm (MOUFPE 7491). (A) carapace, dorsal view. (B) frontal-orbital region of carapace, frontal view. (C) carapace, lateral view, emphasizing the branchiostegite. (D) right antennule, ventral view. (E) right antennal peduncle, dorsal view (flagellum omitted). (F) left Mxp 3, ventral view (exopod flagellum not shown). (G) left minor P1, dorsal view. (H) right major P1, dorsal view. (I) right P2, lateral view. (J) telson, external view. (K) thoracic sternum, ventral view. Setae all omitted. Scale bars: 1 mm.

FIGURE 2. (A–C) Pachycheles coelhoi sp. nov., male holotype, cl 6.4 mm, cw 5.9 mm (MOUFPE 7491). (D–F) Pachycheles rugimanus (A. Milne-Edwards, 1880), male, cl 8.0 mm, cw 7.8 mm (USNM 188445). (A, D) carapace, dorsal view. (B, E) cephalothorax and pleon, ventral view. (C, F) minor and major P1, dorsal view. Scale bars: 1 mm. Arrows: front median lobe strongly projected, separated from lateral lobes by broad concave margins (A); front median lobe very low, poorly projected, separated from lateral lobes by nearly straight margins (D); thoracic sternite 3 median lobe rounded, separated from lateral lobes by shallow, gently concave margins (B); thoracic sternite 3 median lobe distinctly subtriangular, separated from lateral lobes by straight, laterally V-shaped margins (E).

FIGURE 3. (A–C) Pachycheles ackleianus (A. Milne-Edwards, 1880), male, cl 3.6 mm, cw 4.2 mm (MZUSP 12892). (D–F) Pachycheles velerae Haig, 1960, male, cl 5.4 mm, cw 4.9 mm (USNM 110551). (A, D) carapace, dorsal view. (B, E) cephalothorax and pleon, ventral view. (C, F) minor and major P1, dorsal view. Scale bars: 1 mm. Arrows: front distinctly deflexed, nearly straight on dorsal view (A); front slightly deflexed, distinctly trilobate in dorsal view (D).

FIGURE 4. Major chelae. (A, B) Pachycheles coelhoi sp. nov., male holotype, cl 6.4 mm, cw 5.9 mm (MOUFPE 7491). (C, D) Pachycheles rugimanus (A. Milne-Edwards, 1880), male, cl 8.0 mm, cw 7.8 mm (USNM 188445), dorsal and ventral views, respectively. (E, F) Pachycheles velerae Haig, 1960, male, cl 5.4 mm, cw 4.9 mm (USNM 110551). (A, C, E) dorsal view. (B, D, F) ventral view. Scale bars: 1 mm. White arrows: high, heavily tuberculated, elongate upper bulge (A); fixed finger hollowed, interlocking with dactylus (B); narrow, low, rather smooth, elongated upper ridge (E). Black arrows: elongate axial bulge (A); small, rounded bulges (C, E).