Phimochirus formani, Felder & Lemaitre & Craig, 2019

Felder, Darryl L., Lemaitre, Rafael & Craig, Catherine, 2019, Two new species of the Phimochirus holthuisi complex from the Gulf of Mexico supported by morphology, color, and genetics (Crustacea: Anomura: Paguridae), Zootaxa 4683 (4), pp. 531-551 : 540-544

Phimochirus formani nov. sp.

( Figs 1 ; 2C, D ; 5 A–J; 6A–G; Tab. 1 )

Pylopagurus operculatus .— Holthuis, 1959: fig. 31; Provenzano, 1961: 162 (in part); McLaughlin, 1981b: 336 (in part). [See Remarks].

Phimochirus holthuisi .— McLaughlin, 1981a: 5; McLaughlin, 1981b: 342, figs 4c, 6a–c, 7c (in part); Williams, 1984: 225 (in part), fig. 161; Rodriguez-Almaraz et al., 2005: fig. 40. [See Remarks].

Type material. Holotype: male, sl 2.9 mm ( USNM 1543315 = ULLZ 7841 ), northeastern Gulf of Mexico, 28° 10.13’N, 84° 01.07’W, 42 m, northwestern Florida shelf, 5 Jul 2006.

Paratypes: Northeastern Gulf of Mexico . 1 male, sl 3.1 mm ( USNM 1543129 = ULLZ 7685 ) 28° 29.64’ N, 84° 27.95’ W, 47 m, northwestern Florida shelf, 4 Jul 2006 ; 1 male, sl 2.8 mm ( USNM 1543170 = ULLZ 7711 ) 28° 05.2’ N, 83°46.16’ W, 38 m, northwestern Florida shelf, 5 Jul 2006 ; 1 female, sl 3.6 mm, 1 ov female, sl 4.1 mm ( USNM 1543313 = ULLZ 7847 ) 27° 55.58’ N, 83° 46.15’ W, 43 m, northwestern Florida shelf, 5 Jul 2006 ; 1 male sl 1.6 mm, in worm tube ( USNM 1543428 = ULLZ 8062 ) 29° 20.64’ N, 85° 39.18’ W, 48 m, northwestern Florida shelf, 3 July 2006 ; 1 female sl 6.4 mm ( USNM 1543759 = ULLZ 8488 ) 50 m, due west of Tampa Bay , Florida, 3 Aug 1994 ; 1 juvenile, sl 1.2 mm, in tusk shell ( USNM 1544361 = ULLZ 8950 ) 24° 43.37’ N, 83° 13.58’ W, 62 m, off Dry Tortugas, Florida, 3 Jun 2004 ; 1 male, sl 3.1 mm ( USNM 1547566 = ULLZ 14352 ) 26° 12.77’ N, 83° 21.18’ W, 55 m, southwestern Florida shelf, 11 Jun 2012 . Northwestern Gulf of Mexico. 1 ov female, sl 3.6 mm ( USNM 1547705 = ULLZ 14572 ) 28° 44.76’ N, 90° 14.15’ W, 28 m, off Mississippi River Delta, 24 Aug 2012 ; 1 ov female, sl 3.4 mm ( USNM 1547505 = ULLZ 14134 ) 29° 20.683’ N, 88° 27.136’ W, 63 m, off Mississippi , 23 Apr 2011 . Southeastern Gulf of Mexico . 1 female, sl 2.4 mm, 1 ov female sl 3.3 mm ( USNM 1547876 = ULLZ 14323 ) 24° 47.35’ N, 83° 09.3’ W, 56.6 m, off Florida Keys , 13 Jun 2012 .

Other material: Northeastern Gulf of Mexico. 1 ov female, sl 2.8 mm ( USNM 103707 ) 29° 28’ N, 85° 31’ W, 21.9 m, northwestern Florida shelf, 1 Feb 1956 . Southeastern Gulf of Mexico. 1 female, sl 1.8 mm ( USNM 191095) 24° 18.5’ N, 82° 20.0’W, 196–210 m, south of Marquesas Keys , 26 Apr 1969 ; 1 ov female, sl 3.3 mm ( USNM 191096) 24° 21.5’ N, 82° 26.7’ W, 59–60 m, off Key West , 26 Apr 1969 .

Diagnosis. Carapace shield approximately 1.1 times longer than broad; rostrum acutely triangular, reaching distally beyond lateral projections, terminating in strong spine. Antennular peduncles exceeding distal margins of cornea when fully extended by approximately one-fourth length of ultimate segment. Antennal peduncles reaching to about distal margin of corneas when fully extended, flagellum with alternating long (2 flagellar articles in length) and short setae (less than 1 flagellar article in length). Right chela with dorsal surface of fixed finger with few wellspaced low tubercles; palm smooth dorsally or with few well-spaced low tubercles distally near base of fixed finger, dorsomesial margin sinuous sharply defined as tuberculate or bluntly spinose ridge flaring distally and terminating in spine-like distal angle; carpus with dorsomesial margin sharply defined by spinose ridge including strong, mesially projecting spine. Dactyls of second and third pereopods with ventromesial row of 7–9 corneous spinules (or 4 corneous spinules in very small individuals sl <2.0 mm). Anterior lobe of sternite between third pereopods semisubovate, distal margin with simple setae; sternites between fourth and fifth pereopods with simple setae. GenBank sequence accession numbers for paratype (USNM 1547566 = ULLZ 14352): (H3) MK830053 ; (12s) MK828404; (16s) MK848222 .

Description. Carapace shield ( Fig. 5A ) subtriangular, approximately 1.1 times longer than broad; dorsal surface glabrous except for scattered short setae medially on each side and near anterior margin, lacking linea or grooves except for weakly visible short linea and grooves separating narrow lateral lobe on each side; anterior margin between rostrum and lateral projections concave; anterolateral margins sloping; posterior margin roundly truncate. Rostrum acutely triangular, reaching distally beyond lateral projections, terminating in strong spine. Lateral projections subtriangular, terminating in small marginal spine.

Ocular peduncles ( Fig. 5A ) relatively long, about 0.8 length of shield, width near even throughout; surfaces naked except tuft of short setae on mesial face medially; corneas weakly dilated. Ocular acicles ( Fig. 5B ) narrow (approximately 3.5 times longer than basal width), acutely subtriangular, dorsal surface concave, each terminating in small submarginal spine.

Antennular peduncles exceeding distal margins of corneas when fully extended by approximately one-fourth length of ultimate segment. Segments naked or with scattered short setae; basal segment with blunt ventromesial distal angle, and small spine on lateral face.

Antennal peduncles reaching to about distal margin of corneas when fully extended. Fifth segment slender, with few short setae on lateral and mesial margins. Fourth segment unarmed. Third segment with blunt ventrodistal angle. Second segment with dorsolateral distal angle produced into strong spine-like process with few short distolateral setae; dorsomesial distal angle with small spine. First segment unarmed laterally. Antennal acicles reaching to about proximal margin of corneas, broadly curving outward, terminating in strong spine, with few tufts of setae on mesial margin and tuft of setae distally. Flagellum long, exceeding extended right cheliped, with alternating long (2 flagellar articles in length) and short setae (less than 1 flagellar article in length).

Third maxilliped ( Fig. 5D ) ischium with crista dentata consisting of approximately 18–20 small, sharp teeth slightly diminishing in length distally, and accessory tooth.

Chelipeds ( Fig. 5 E–J) strongly dissimilar in robustness and shape, right massive and distinctly larger and stronger than left; articular membrane between chela and carpus often with fleshy protuberance ( Fig. 5H, I , see Remarks). Right (major) cheliped ( Fig. 5 G–J) operculate, virtually naked on all surfaces except for few scattered short setae. Chela subcircular to subovate in outline; cutting edges of dactyl and fixed finger each with row of slightly unequal calcareous teeth and terminating in blunt, inwardly curved calcareous tips overlapping when closed. Dactyl slightly shorter than palm; mesial margin sharply defined, crenulate; dorsal surface with distinct median ridge, dorsomesial surface concave. Fixed finger broad basally; dorsal surface with few well-spaced low tubercles; ventrolateral margin sharply defined, crenulate. Palm smooth dorsally or with few well-spaced low tubercles distally near base of fixed finger; ventrolateral margin sharply defined, weakly crenulate (or straight in very small individuals sl<2.0 mm); dorsomesial margin sinuous sharply defined as tuberculate or bluntly spinose ridge flaring distally and terminating in spine-like distal angle (or straight and not flaring in very small individuals <2.0 mm); ventromesial surface smooth. Carpus approximately as long as merus; dorsal and lateral surfaces smooth, rounded, with weakly defined ridge on dorsolateral margin distally; dorsodistal margin with row of small blunt spines or tubercles; dorsomesial margin sharply defined by spinose ridge including strong, mesially projecting spine; mesial face nearly vertical, of- ten with small distal spine; ventral surface smooth. Merus subtriangular in cross-section, surfaces smooth, unarmed except for row of small sharp spines on dorsodistal margin and spine on ventrolateral distal angle. Ischium unarmed. Coxa with row of setae on ventromesial distal angle, ventral surface with cluster of low, minute spines or tubercles proximally.

Left (minor) cheliped ( Fig. 5E, F ) slender, reaching to approximately mid-level of right palm, surfaces smooth, with scattered short setae; fingers terminating in inwardly curved corneous tips crossed when closed and ventrally forming spoon-like surface. Dactyl longer than palm; cutting edge with row of fused minute corneous spinules. Fixed finger broader than dactyl; cutting edge with row of minute calcareous teeth and row of fused corneous spinules. Palm dorsal surface with weak median ridge proximally, small median spine distally near cutting edges of fixed finger and dactyl. Carpus approximately as long as merus; dorsal margin with row of small sharp spines and strong dorsodistal spine; lateral surface with small ventrodistal spine. Merus subtriangular in cross-section; lateral surface with minute ventrodistal spine. Ischium and coxa unarmed, latter with row of setae on ventromesial margin.

Ambulatory pereopods 2 and 3 ( Fig. 5 A–E) sparsely setose, left and right subequal, each with dactyl broadly curved, approximately 1.3 times longer than propodus, terminating in sharp corneous claw curving ventrally; dorsal margins with well-spaced long setae; ventral margins with scattered short setae, with ventromesial row of 7–9 corneous spinules (or 4 corneous spinules in small individuals sl <2.0 mm). Propodus nearly straight, subequal in length to carpus, with few tufts of setae dorsally, with 1 or 2 ventrodistal corneous spinules near articulation with dactyl. Carpus with small dorsodistal spine, with few setae or tufts of setae dorsally. Merus and ischium unarmed. Anterior lobe of sternite between third pereopods semisubovate ( Fig. 3C ), distal margin with simple setae.

Fourth pereopod ( Fig. 5F ) semichelate, sparsely setose. Dactyl stout, slender, terminating in inwardly curved corneous claw; dorsal margin with tuft of long setae distally; ventral margin with ventrolateral row of minute, closely-set corneous teeth, and distinctly developed brush-like preungual process at base of corneous claw. Propodal rasp with 1 row of ovate corneous scales. Carpus unarmed except for few long setae dorsally. Merus unarmed, nearly naked. Sternite between coxae rod-like, with simple setae.

Fifth pereopod chelate. Propodal rasp extending for about half length lateral surface of propodus, with long curved setae on ventrodistal angle. Sternite between coxae ( Fig. 5C ) with anterior lobe subdivided into 2 lobes, with distal simple setae.

Uropods markedly asymmetrical, left largest, exopods each with row of long setae dorsally; ventral margin of left and right exopods naked or with few short setae. Telson ( Fig. 6G ) weakly asymmetrical, longer than broad, with distinct lateral indentations; posterior lobes with corneous lateral margins, lobes separated by narrow U-shaped median cleft, terminal margins oblique, each armed with row of 4 strong, slender spines (including spine at distolateral angle) interspersed with 1 or 2 small spines.

Color. In life ( Fig. 2C, D ), ocular peduncle with band of deep bluish purple near midlength, broadest ventrally, dorsally disjunct, blotched with red, or partially incomplete, proximally abutted by ill-defined variable band of red; carapace shield marked by light “trident” pattern consisting of broad median whitish longitudinal bar subdivided by narrow orange center line, a similar bar to either side, lateral bars diverging from median bar anteriorly; distal margins of cheliped and anterior walking leg meri lacking lavender patches.

Etymology. The specific name was selected to honor W. Wayne Forman, a New Orleans based environmental scientist whose talents include an unusually broad grasp of marine biota, and who has over many years brokered access to research sites, acquisition of research specimens, and the securing of financial support for marine scientists working throughout the northern Gulf of Mexico.

Habitat. Occupying variety of small to medium sized gastropod shells, especially faciolariids, turbinids, and muricids; offshore calcareous banks and deep platforms around coral reefs, especially where richly covered by macroalgae and epifauna, including among rhodoliths; inner to middle continental shelf; 27– 62 m.

Distribution. Western Atlantic: northeastern, northwestern, and southeastern Gulf of Mexico; Suriname.

Remarks. As previously noted under the Remarks for Phimochirus holthuisi s.s., McLaughlin’s (1981a, b) report of P. holthuisi includes three species, one of which is P. formani nov. sp. and was represented by Clade I in our molecular genetic analyses ( Fig. 1 ). This new species, and a second new species herein described, is unmistakably distinguished in life by differences in color patterns. Aside from color differences, the two can be separated by subtle morphological differences such as the degree of armature on the dorsal surface of the right chela (with few small tubercles on the fixed finger and distal part of the palm in P. formani nov. sp. vs. numerous small tubercles on the fixed finger and at least distal half of the palm in the other new species); relative development of the dorsomesial ridge of the right chela (sinuous and tuberculate or bluntly spinose, flaring distally in P. formani nov. sp. vs. straight, crenulate, not flaring distally in the other new species); and armature of the dactyl of the second and third pereopods (with rows of 7–9 dorsomesial and ventral corneous spinules in P. formani nov. sp. vs. rows of 10 or 11 dorsomesial and ventral corneous spinules in the other new species). However, these morphological characters must be used with caution and best in combination, as they are subject to some variations with size of specimens and thus are not absolute.

The color description that Holthuis (1959) provided for the Suriname materials that he provisionally assigned to Pylopagurus operculatus fits better to Phimochirus formani nov. sp. than to P. holthuisi s.s. Provenzano (1961) noted the color differences but, even so, included the Suriname record in the synonymy of his Pylopagurus holthuisi (= Phimochirus holthuisi ). Thus, the line illustrations of Holthuis (1959: fig. 31) appear to apply to neither Pylopagurus operculatus (= Phimochrius operculatus ), as originally reported, nor to Phimochirus holthuisi s.s., but instead most likely to P. formani nov. sp. A fleshy protrusion of the joint membrane between the major cheliped carpus and propodus, somewhat similar to that reported in P. operculatus , is evident in some specimens. While P. formani nov. sp. occurs sympatrically with the other herein described new species, in regional collections to date the former appears to be more common than the latter in the eastern Gulf of Mexico, while the other new species is more common in samples from the western Gulf.

The illustration published by Holthuis (1959, fig. 31) for Pylopagurus operculatus , subsequently discussed by Provenzano (1961), was reproduced in whole or in part by Williams (1984) and Rodríguez-Almaraz et al. (2005) and is herein considered to represent Phimochirus formani nov. sp.

Figures

FIGURE 1. Maximum Likelihood phylogeny inferred in RAxML based on H3 nuclear DNA, 12s mtDNA, and 16s mtDNA. Bootstrap support values (bs) and Bayesian posterior probabilities (bp) with values greater than 50 are displayed above branches at tree nodes with the notation bs/bp. Clades I and II, assigned a priori to Phimochirus cf. holthuisi, are delimited by vertical black bars and correspond to two new species herein described. For branch labels, taxon name is followed by voucher catalog number (see Table 1) and collection locality. Abbreviations: eGMx = eastern Gulf of Mexico, ePac = eastern Pacific, neGMx = northeastern Gulf of Mexico, nwGMx = northwestern Gulf of Mexico, seGMx = southeastern Gulf of Mexico, swGMx = southwestern Gulf of Mexico.

FIGURE 2. Phimochirus holthuisi (Provenzano, 1961) s.s.: A, male, sl 3.3 mm (USNM 1542650 = ULLZ 3564), Belize; B, male, sl 2.9 mm (USNM 1558313 = ULLZ 16588), Belize. Phimochirus formani nov. sp.: C, male paratype, sl 3.1 mm (USNM 1547566 = ULLZ 14352), northeastern Gulf of Mexico; D, male paratype, sl 2.8 mm (USNM 1543170 = ULLZ 7711), northeastern Gulf of Mexico. Phimochirus tunnelli nov. sp.: E, male paratype, sl 4.1 mm (USNM 1545269 = ULLZ 10611), northwestern Gulf of Mexico; F, ov female paratype, sl 3.9 mm (USNM 1541146 = ULLZ 5789), northwestern Gulf of Mexico.

FIGURE 3. Phimochirus holthuisi (Provenzano, 1961) male holotype, sl 4.2 mm (USNM 10515), U. S. Virgin Islands. A, cephalothorax, eyes, and frontal appendages, dorsal surface; B, left second pereopod dactyl, lateral surface; C, left second pereopod dactyl, mesial surface; D, left third pereopod dactyl, lateral surface; E, left third pereopod dactyl, mesial surface; F, telson, dorsal surface. Scale bars = 1.0 mm.

FIGURE 5. Phimochirus formani nov. sp. A–I, male holotype, sl 2.9 mm (USNM 1543315 = ULLZ 7841); J, male paratype, sl 3.1 mm (USNM 1547566 = ULLZ 14352); both from northeastern Gulf of Mexico. A, cephalothorax, eyes, and frontal appendages, dorsal surface; B, left ocular acicle, dorsal surface; C, thoracic sternites and coxae, ventral surface; D, right third maxilliped, external surface; E, minor (left) cheliped, dorsal surface; F, minor (left) cheliped, lateral surface; G, major (right) cheliped, dorsal surface; H, major (right) cheliped, mesial surface; I, major (right) cheliped, ventral surface; J, major (right) cheliped, dorsal surface. Scale bars = 1.0 mm (A, C–F); 0.25 mm (B); 2.0 mm (G–I).

FIGURE 6. Phimochirus formani nov. sp. Male holotype, sl 2.9 mm (USNM 1543315 = ULLZ 7841), from northeastern Gulf of Mexico. A, right second pereopod, lateral surface; B, right second pereopod terminal articles, mesial surface; C, right third pereopod, lateral surface; D, right third pereopod terminal articles, mesial surface; E, left third pereopod, lateral surface; F, right fourth pereopod terminal articles, lateral surface; G, telson, dorsal surface. Scale bars = 2.0 mm (A, C, E); 1.0 mm (B, D, F, G).