Areopaguristes rafaeli, Craig & Felder, 2022

Craig, Catherine W. & Felder, Darryl L., 2022, Two new marine hermit crabs allied with the Paguristes tortugae complex (Crustacea: Decapoda: Anomura) from the western Atlantic, Zootaxa 5178 (1), pp. 1-25 : 4-10

publication ID	https://doi.org/ 10.11646/zootaxa.5178.1.1
publication LSID	lsid:zoobank.org:pub:57010543-9D74-4F61-BCC1-8BDF61ED135D
DOI	https://doi.org/10.5281/zenodo.7025057
persistent identifier	https://treatment.plazi.org/id/A85087D5-5B5E-3066-FF37-F5AF1BDAF801
treatment provided by	Plazi
scientific name	Areopaguristes rafaeli
status	sp. nov.

Treatment

Areopaguristes rafaeli View in CoL n. sp.

( Figs 1D, C View FIGURE 1 , 2A–G, I View FIGURE 2 , 3 View FIGURE 3 , 4 View FIGURE 4 )

Areopaguristes nr. hummi .— Craig & Felder, 2021: table 1, 304, 311, 317.

Areopaguristes “nr. hummi nov. sp. ” ― Craig & Felder, 2021: fig. 1.

Type material. Holotype: male DNA and photo voucher, sl 2.5 mm ( ULLZ 15009 View Materials / USNM 1548225 View Materials ), Panama, Bocas del Toro, stn. 9, by SCUBA, 3 m, 03 Aug 2004, coll. D. Felder, R. Lemaitre, and colleagues.

Paratypes: 2 males, sl 2.5, 2.3 mm ( ULLZ 18007 View Materials / USNM 1661768 View Materials ), Panama, Bocas del Toro, stn. 48, Almirante pilings, 9°16.218’N, 82°23.382’W, snorkeling, 11 Aug 2004 GoogleMaps .

Diagnosis. Twelve pairs biserial gills. Antennal flagellum short with dense setae approximately 6–8 articles in length originating on ventral surfaces. Antennular peduncles extending beyond cornea distal margins by at least 0.5 length of ultimate peduncular segment. Ocular acicles subtriangular, flushly abutted along mesial margins with numerous spines along lateral border. Rostrum obsolete. Maxillule proximal and distal endite mesial borders bearing brushes of short, finger-like setae, exopod external lobe with dorsal projection well developed. Second and third pereopod dactyli unarmed. Second pereopod propodi, carpi, and meri dorsal margins each bearing row of acute spines, many with corneous tips. Telson weakly asymmetrical, posterior lobe terminal margins well armed. Male first pleopod inferior lamella distal margin bearing single row of curved spines. In life, eyestalks uniformly golden or straw colored, cheliped merus mesial surface lacking blue markings, with distinct black crescent at distal extremity. Applicable GenBank sequence accession numbers from Craig & Felder (2021) for holotype, ULLZ 15009/USNM 1548225: (H3) MW160335 View Materials ; (12S) MW160980 View Materials ; (16S) MW167181 View Materials .

Description. Twelve pairs of biserial gills. Shield ( Fig. 2B View FIGURE 2 ) subtriangular, length slightly exceeding width. Dorsal surface central region convex, bearing widely spaced tufts of setae, most abutting spines or tubercles; lateral surface bearing widely-spaced low tubercles and small spinules; anterior margins between rostrum and lateral projections weakly concave; anterolateral angle obtuse, bearing irregularly spaced spines and spinules. Rostrum obsolete, unarmed, not extending distally beyond lateral projections. Lateral projections each bearing prominent spine and tuft of setae. Branchiostegite lateral surface with granular texture, moderately setose, with dorsal and anterior margins each bearing row of small spines. Posterior carapace poorly calcified, lateral surfaces bearing scattered setae.

Ocular peduncles ( Fig. 2B View FIGURE 2 ) subcylindrical, narrowing slightly at mid-length, diameter at base approximately equal to that at cornea, lacking any banding, spotting, or other patterning, corneas black. Ocular acicles subtriangular; mesial margins unarmed and flushly abutted at midline; lateral margins somewhat oblique, bearing numerous small spines.

Antennular peduncles ( Fig. 2B View FIGURE 2 ) extending anteriorly beyond cornea distal margin by approximately 0.7 times length of ultimate segment; ultimate segment dorsal surface with row of minute setae; basal segment lateral surface bearing minute spine, distolateral angle bearing spine; flagellum secondary (ventral) ramus well developed.

Antennal peduncles ( Fig. 2B View FIGURE 2 ) extending anteriorly slightly beyond cornea distal margin. Fifth segment without remarkable characteristics. Fourth segment dorsodistal angle bearing small spine, easily obscured by antennal acicle from dorsal view. Third segment ventromesial distal angle bearing acute spine; ventral margin sparsely setose. Second segment dorsolateral distal angle bearing acute spine; dorsomesial distal angle likewise. First segment unarmed. Antennal acicles extending anteriorly slightly beyond 0.5 distal length of ocular peduncles; lateral margin unarmed and sparsely setose; mesial margin oblique, bearing numerous spines and short setae. Antennal flagellum short, not extending beyond chelae fingertips, densely setose, setae approximately 6–8 articles in length and originating on ventral surface of articles.

Mandible ( Fig. 2F View FIGURE 2 ) with incisor edge calcareous; ultimate segment of palp relatively narrow, length shorter than combined length of penultimate and basal segments. Maxillule ( Fig. 2D, E View FIGURE 2 ) with proximal and distal endite mesial margins bearing robust, finger-like setae interspersed with fine, hair-like setae; endopod internal lobe distal angle with dorsal projection well developed ( Fig. 2D View FIGURE 2 ), external lobe sharply recurved, length approximately 0.7 times that of internal lobe, margins of both lobes bearing scattered setae. Maxilla ( Fig. 2I View FIGURE 2 ) proximal and distal endite mesial margins densely setose; endopod tapered distally, not overeaching distal apex of scaphognathite; scaphognathite recurved, margins densely setose. First maxilliped ( Fig. 2A View FIGURE 2 ) endopod length approximately 0.7 times that of exopod; exopod tapering distally; epipod well developed. Second maxilliped ( Fig. 2G View FIGURE 2 ) endopod basis bearing sparse small spinules. Third maxilliped ( Fig. 2C View FIGURE 2 ) endopod merus internal surface with distomesial angle bearing acute spine, external surface bearing small spine at midline; ischium with crista dentata well developed, lacking accessory tooth.

Chelipeds ( Fig. 3A–D View FIGURE 3 ) subequal in size, similarly armed, fingers opening transversely, tips slightly crossed; dorsal surfaces of chelae and carpi densely covered with tufts of plumose setae partially obscuring armature beneath, longer setae forming dense fringe along dorsolateral and dorsomesial margins of chelae, and carpus; fixed and moveable finger each terminating in tapered corneous tip. Dactyl length approximately 3 times maximum height; cutting edge bearing calcareous teeth and widely spaced tufts of stiff bristles; dorsal surface bearing irregularly spaced spines, most abutting tuft of setae; dorsomesial margin bearing irregular row of corneous-tipped spines decreasing in size distally, most abutting tuft of setae; mesial surface bearing irregular row of conical spines continuing distally as unevenly spaced small tubercles, most abutting tufts of setae. Fixed finger not extending beyond cheliped dactyl; cutting edge bearing calcareous teeth bordered with row of stiff bristles ventrally. Palm dorsal surface somewhat convex; dorsolateral surface bearing 2 irregular longitudinal rows of strong spines, each spine abutting tuft of setae; dorsolateral margin bearing longitudinal row of spines continuing onto fixed finger lateral margin; ventral surface bearing widely spaced tubercles, spines, and tufts of setae; lateral surface bearing irregular, longitudinal row of spines interspersed with tufts of short setae; mesial surface slightly convex, bearing shallow rugae and small tubercles. Carpus length approximately 0.3 times that of chela; dorsal surface bearing scattered conical spines and spinules interspersed with setae; dorsolateral and dorsomesial margins well defined and slightly elevated, each bearing row of corneous-tipped spines; dorsolateral surface bearing evenly spaced spines; mesial surface bearing scattered small tubercles and spines. Merus length approximately 2.5 times that of carpus, subtriangular in cross section; dorsal margin bearing small tubercles proximally, as well as dense cluster of conical spines and spinules distally, some with corneous tips, ultimate distal margin bearing widely spaced spines; ventromesial margin bearing unevenly spaced, irregular spines; lateral surface bearing irregularly spaced spines ventrally; ventrolateral margin with row of conical spines increasing in size distally. Ischium ventromesial margin bearing row of blunt spinules and scattered setae. Coxa ventrodistal angle with dense tuft of setae visible in mesial view.

Second pereopod ( Fig. 3E, F View FIGURE 3 ) slender, extending beyond cheliped by approximately 0.5 length of second pereopod dactyl; dorsal and ventral margins of dactyl, propodus, carpus and merus bearing dense fringe of setae. Dactyl subcylindrical, length as much as 10 times maximum height, curved ventrally from lateral view and terminating in curved corneous claw; dorsal and ventral margins unarmed, bearing widely spaced tufts of setae; mesial and lateral surfaces likewise. Propodus length approximately 0.7 times that of dactyl; dorsal margin armed with slender spines decreasing in size distally (in mesial view); ventral margin unarmed; dorsolateral surface bearing widely spaced low tubercles, some abutting tufts of setae; mesial surface bearing scattered small tubercles and widely spaced tufts of setae. Carpus length approximately 0.5 times that of propodus; dorsal margin bearing row of irregularly spaced spines (in mesial view); ventral margin unarmed; lateral surface ( Fig. 3E View FIGURE 3 ) moderately convex, dorsolateral surface with slight longitudinal ridge bearing low tubercles abutting tufts of setae; dorsomesial surface bearing sparse small tubercles and tufts of setae. Merus length approximately 2 times that of carpus, somewhat laterally compressed; dorsal margin bearing irregular tubercles and spines abutting tufts of setae; lateral surface bearing prominent tubercle abutting dense tuft of setae distally; dorsolateral surface bearing irregularly spaced, small tubercles and scattered tufts of setae. Ischium laterally compressed, mesial and lateral surfaces subtriangular, dorsodistal angle bearing prominent spines. Coxa without distinguishing characters.

Third pereopod ( Fig. 4A, B View FIGURE 4 ) similar in proportions and armature to second pereopod except as noted. Propodus length approximately 8 times that of dactyl; dorsal margins lacking distinct spines or spinules. Carpus dorsal margin unarmed except for small spine at dorsodistal angle; lateral surface longitudinal ridge less prominent than that of second pereopod. Merus length approximately 1.5 that of carpus; dorsal margin lacking distinct spines or spinules. Ischium length approximately 0.5 times that of merus; mesial and lateral surfaces subrectangular; dorsolateral surface bearing irregularly spaced minute tubercles. Sternite of third pereopod with anterior lobe subrectangular, bearing rounded tubercles with dense tufts of setae.

Fourth pereopod ( Fig. 4D View FIGURE 4 ) not extending beyond distal margin of third pereopod merus, segments somewhat laterally compressed; propodus, carpus, and merus dorsal margins bearing dense fringe of long setae. Dactyl ( Fig. 4E View FIGURE 4 ) terminating in elongate corneous claw abutting dense tuft of bristles dorsally; distoventral margin bearing 2 (in holotype) acute spines abutting preungual process. Preungual process well-developed, slender, length slightly less than that of corneous claw. Propodus length approximately 2 times that of dactyl; ventrolateral surface bearing narrow propodal rasp extending approximately 0.3 length of segment. Carpus, merus, and ischium/basis similar in length, dorsal and ventral margins of each bearing dense fringe of setae. Coxa distal margin with fringe of stiff setae; ventromesial surface with row of minute spines interspersed with setae.

Fifth pereopod ( Fig. 4C View FIGURE 4 ) chelate; fixed finger subequal in length to dactyl; appendage segments generally subcylindrical. Propodus elongate, length approximately 3 times maximum height; lateral surface bearing rasp continuous across dactyl, fixed finger and approximately 0.3 distal length of segment; ventromesial surface concave, bearing dense patch of setae distally.

Abdomen curled, poorly sclerotized. Male first ( Fig. 4F, G View FIGURE 4 ) and second ( Fig. 4H View FIGURE 4 ) pleopods each paired and modified as gonopods; pleopods 3–5 unpaired, uniramous. Male first pleopod inferior lamella lateral margin fringed with setae, distal margin with single row of curved spines; internal lamella narrow and somewhat reduced, distal margin bearing tuft of long setae; external lamella extending slightly beyond inferior lamella distal margins; second pleopod ( Fig. 4H View FIGURE 4 ) ultimate segment terminal lobe somewhat deflected laterally and densely setose.

Uropods ( Fig. 4I View FIGURE 4 ) strongly asymmetrical, left robust and elongate. Telson ( Fig. 4I View FIGURE 4 ) weakly asymmetrical (in holotype); left lobe somewhat longer than right, deep lateral incisions dividing anterior and posterior portions; anterior lobes subovate; posterior lobes subtriangular to subquadrate, left and right separated by well-defined cleft, left lobe terminal margin bearing prominent conical spines with corneous tips, curving outward somewhat, right lobe bearing smaller, irregular spines, some with corneous tips.

Size. Largest examined, male, sl 2.5 mm

Color. ( Fig. 1C, D View FIGURE 1 ). Pale buff or peach background color marked with irregular orange to rust patches over cheliped and carapace shield. Walking legs bearing irregular orange to rust banding on propodus, carpus, and merus. Second and third pereopod dactyls each bearing two distinct orange to rust bands alternating with white. Cheliped merus mesial surface bearing black, crescent shaped marking at distal extremity and lacking any blue markings. Eyestalks solid golden yellow, lacking any bands, stripes, or spotting.

Etymology. The species name, “rafaeli”, honors our colleague and friend, Rafael Lemaitre, for his many contributions to studies of paguroid and other decapod crustaceans, as well as his assistance in field collections and valuable editorial advice that facilitated the present project.

Distribution and habitat. So far known only from the type series, A. rafaeli n. sp. is found near Bocas del Toro, Panama, in the southwestern Caribbean and has been collected in shallow water approximately 3 m deep.

Morphological variations. In general, smaller paratypes show reductions in the number and prominence of spines on the thoracic appendages and telson terminal margins. This is especially evident on the dorsal surfaces of the chelae and carpus. Accompanying this variation, the number of spines abutting the preungular process of the fourth pereopod is reduced from two to one when our smallest male (sl 2.1 mm) is compared to our largest, the holotype male (sl 2.5 mm). For the ocular acicles, the mesial margins are always unarmed and flushly abutted at the midline, although the lateral margin shape can range from straight and oblique as in the holotype male ( Fig. 2B View FIGURE 2 ), to fan-shaped in the smaller paratypes, resembling more closely what is provisionally the generic type of Paguristes (see Craig & Felder 2021: 301–302), Paguristes weddellii H. Milne Edwards, 1848 ( Fig. 2H View FIGURE 2 ) or Areopaguristes lemaitrei ( Fig. 2J View FIGURE 2 ). However, the most notable variation among paratypes is in the shape of the telson, which shows higher degrees of asymmetry in the smaller individuals.

Remarks. In addition to molecular genetic and coloration characters that separate Areopaguristes rafaeli n. sp. from its sister species, A. hummi , the two species appear to be well-separated in range. So far, the known occurrence of our new species is restricted to a small area of the Caribbean coast, while A. hummi is recorded from many localities in the Gulf of Mexico ( Table 1 View TABLE 1 ). Differences in color between the new species and A. hummi are very evident in life, especially in pigmentation and patterning of the cheliped merus, eyestalks, and cephalic appendages. The latter species ( Fig. 1A, B View FIGURE 1 ) is readily recognized by the prominent blue spot upon the cheliped merus mesial surface that is bordered along the distal edge by a black semicircular band ( Fig. 1A View FIGURE 1 ), whereas this new species ( Fig. 1C, D View FIGURE 1 ) lacks the blue meral spot, and the semicircular black band at the distal margin of the merus mesial surface is reduced to a black crescent-shaped marking ( Fig. 1C View FIGURE 1 ). As confirmed via photographic records, the eyestalks, antennular peduncles, and antennal flagella of A. hummi are predominantly solid blue in color ( Fig. 1B View FIGURE 1 ). This coloration of the cephalic appendages and eyestalks definitively sets A. hummi apart from A. rafaeli n. sp., which has light orange to straw-colored eyestalks, likewise confirmed through photographic documentation ( Fig. 1D View FIGURE 1 ). However, no definitive characters based on structural morphology are known to separate the two species.

In addition to its striking morphological similarity to Areopaguristes hummi , the new species shares several general characteristics with other species of Areopaguristes and the P. tortugae complex ( Table 2 View TABLE 2 ). However, as suggested by genetic evidence ( Craig & Felder 2021), the treatment of A. hummi and its closest genetic allies as closely related to the P. tortugae complex may not be warranted, and morphological characters offer conflicting support. Favoring their inclusion in the P. tortugae complex, A. hummi , A. rafaeli n. sp., and their nearest genetic associates exhibit the characteristic fringe of setae on the thoracic appendages, an armed telson, and spines on the male gonopod external lobe inferior lamella. As with all other members of the complex, both A. hummi and A. rafaeli n. sp. bear an epipod on the first maxilliped. This epipod is likewise present in the generic type species A. setosus (H. Milne Edwards, 1848) (see Rahayu 2005), but recent emendments to the generic diagnosis based on evaluations of A. oxyophthalmus ( Holthuis, 1959) and A. praedator (Glassell, 1937) assert that the presence of the first maxilliped epipod is not diagnostic at the genus level ( Ayon-Parente et al. 2015). The full significance of variability in this character across the presently accepted membership of Areopaguristes remains unexplored, but the presence or absence of the first maxilliped epipod is so far diagnostic at the species level and shows potential utility in the designation of Areopaguristes subgroups, or perhaps even future generic diagnoses.

Casting doubt on the affinity of Areopaguristes hummi and A. rafaeli n. sp. with other P. tortugae complex constituents, the pereopods of A. hummi and its genetic allies are slender and generally subcylindrical with the proportions of the pereopod segments, especially the elongate nature of the dactyl, drastically different from those of P. tortugae and its genetic allies such as A. hewatti . Additionally, the ocular acicles of A. hummi and A. rafaeli n. sp. are greatly dissimilar in shape and orientation from those of other species currently considered members of the P. tortugae complex. Being flushly abutted at the midline and accompanied by a greatly reduced rostrum, the configuration most closely resembles that of a handful of eastern Pacific species including A. lemaitrei Ayon-Parente & Hendrickx, 2012 ( Fig. 2J View FIGURE 2 ), A. waldoschmitti Ayon-Parente & Hendrickx, 2012 , and P. weddellii ( Fig. 2H View FIGURE 2 ). Further, for A. hummi and A. rafaeli n. sp., the gonopod ( Fig. 4G, H View FIGURE 4 ) in males is shorter and stouter than that of most other species of Paguristes and Areopaguristes from the western Atlantic, aside from A. tudgei .