Paguristes aztatlanensis Glassell, 1937

Ayón-Parente, Manuel, Hendrickx, Michel E. & Cáceres, Ignacio, 2022, Redescription of Paguristes aztatlanensis Glassell, 1937 and description of a new species of the genus Paguristes Dana, 1851 (Anomura, Paguroidea, Diogenidae) from western Mexico, Zootaxa 5128 (2), pp. 269-283 : 270-275

Paguristes aztatlanensis Glassell, 1937

( Figs. 1–3 )

Paguristes aztatlanensis Glassell, 1937: 249 . — Rodríguez de la Cruz 1987: 87 (list). — Hendrickx 1993: 309 (tab. 8). — Hendrickx & Harvey 1999: 369. — Ayón-Parente & Hendrickx 2007: 65, 67; 2010b: 5, fig. 3, tab. 1–3. — McLaughlin et al. 2010: 22 (list).

Type material. Holotype: ovigerous female (SL 6.2 mm), 5.4 km north from Cabo Pulmo (23°28’N, 109°24’W), Gulf of California, Baja California Sur, Mexico, 30 Apr 1936, coll. William Beebe (AMNH-12224) . Paratype: female (SL 5.7 mm), same locality (AMNH-12225).

Description. Thirteen pairs of biserial gills. Shield ( Fig. 1A ) 1.1 × as long as broad; anterolateral margins slopping, anterior margin between rostrum and lateral projections concave, fringed with long setae; posterior margin truncated, tip rounded; dorsal surface rugose anteriorly, a few small spines or spinules laterally and tufts of long setae; anterolateral angles with strong spine concealed partially with tufts of long setae. Rostrum ( Fig. 1A ) long, triangular, terminating in small spine and tufts of setae, exceeding slightly lateral projections. Lateral projections obtusely triangular, with small marginal spine. Branchiostegites each with few spinules on distal and dorsal margins, concealed by moderately dense long setae.

Ocular peduncles ( Fig. 1A ) straight, cylindrical, 0.7 × length of shield, base slightly broad; dorsal surface with tufts of short setae; corneal diameter 0.16 × peduncular length. Ocular acicles subrectangular at their base, triangular apically, terminating in 1 or 2 spines, mesial and lateral margins unarmed, separated basally by 0.5 × basal width of 1 acicle.

Antennular peduncles ( Fig. 1A ) when fully extended overreaching slightly distal margin of corneas; ultimate segment with row of very fine dorsal setae; penultimate segment with small spine on ventromesial margin in proximal half; basal segment with moderately strong spine on ventrodistal margin, mesial and lateral surfaces with strong spine on distal margin, small spine on lateral face of statocyst lobe.

Antennal peduncle ( Fig. 1A ) moderately long, reaching 0.67 × length of ocular peduncles; fifth segment with few scattered tufts of setae; fourth segment with strong dorsodistal spine; third segment with ventral margin strongly produced, ending in strong spine, mesial margin unarmed or with 1 or 2 spinules; second segment with dorsolateral distal angle produced, ending in bifid spine, lateral margin with 1 or 2 strong spines, dorsomesial angle with 1 strong spine, mesial margin with 1 small spine and tufts of setae; first segment unarmed or with 1 laterodistal small spine, ventral margin strongly produced, rounded. Antennal acicle moderately long, reaching to distal margin of fifth peduncular segment, terminating in prominent bifid spine, dorsolateral margin with 2 spines, mesial margin with 3 or 4 spines, partially obscured by long setae. Antennal flagellum as long as shield, articles with short setae on proximal half, these setae shorter than article length, distal 1/2 with 2 setae longer than 2 articles length and several additional setae shorter than 1 article length.

Third maxilliped ( Fig. 3B, C ) with basis-ischium fusion incomplete, basis with 1 small spine on ventral margin, ischium with crista dentata well developed, bearing 15 corneous denticles, without accessory tooth, with 1 small spine at ventrodistal angle, merus with 4 spines on ventral margin, dorsodistal margin with 1 small spine, carpus with 1 small spine in dorsodistal margin.

Chelipeds subequal, somewhat dissimilar ( Fig. 1D–G ), left slightly longer than right. Dactyl 1.8–2.0 × length of palm, ending in moderately strong, spoon-shaped claw, dorsomesial margin with row of strong, corneous-tipped spines decreasing in size distally, and tufts of long setae, dorsal surface with 1 (right) or 2 (left) rows of tipped spines, smaller than mesial spine, and tufts of short setae, mesial surface with proximal area unarmed, the rest with irregular vertical rows of flattened tubercles ending in small, triangular, corneous-tipped spines and tufts of short setae, cutting edge with row of calcareous (proximally) and corneous (distally) teeth. Palm with row of 3 (left) or 4 (right) prominent corneous-tipped spines and tufts of long setae on dorsomesial margin, dorsolateral margin not well delimited, rounded, with spine-like tubercles, stronger and more sharper on fixed finger, obscured by long plumose setae, dorsal surface with 6 or 7 irregular longitudinal rows of corneous-tipped spines, 2 or 3 of these rows extending on fixed finger, mesial face with some spine-like tubercles or spines, lateral face of palm and fixed finger with numerous spine-like tubercles decreasing in size on fixed finger and tufts of setae, ventral surface with strong spine-like tubercles and tufts of long, stiff setae. Carpus with 2 (right) or 4 (left) prominent corneous-tipped spines on dorsomesial margin, distal margin with 1–4 spines, dorsolateral margin with 6 or 7 corneous-tipped spines, dorsal surface with numerous spines, principally near dorsomesial margin, mesial face smooth, ventromesial distal angle with 1 or 2 small tipped-corneous spines, lateral face with numerous spine-like tubercles or spines. Merus subtriangular, dorsal face with 1 row of small tipped spines increasing in size distally and forming transversal rows of strong or moderately strong tipped spines accompanied with tufts of long plumose setae, subdistal and distal margins with strong or moderately strong corneous-tipped spines extending on lateral and mesial margins, mesial face smooth, lateral face with spinules or small spines, ventromesial and ventrolateral margins with row of small spines increasing in size distally, ventral surface with scattered spinules distally. Ischium with row of small spines on ventromesial margin, laterodistal margin with 2 spines, dorsodistal margin with 1 small spine.

Second and third pereopods ( Fig. 2A–D ) with dactyl 1.7–1.9 × length of propodus, dorsal margin with row of tufts of moderately long setae, dorsomesial margin with row of tubular or conical, small corneous-tipped spines proximally, becoming corneous spines distally (second) or only corneous spines (third), mesial and lateral surfaces with numerous small corneous spines and tufts of short setae, ventral margin each with 9–13 corneous spines increasing in size distally, concealed by tufts of long setae. Propodus of second pereopods with row of prominent spines on dorsal surface and one additional row of smaller spines or tubercles accompanied by tufts of long setae. Dorsal surfaces of third pereopods with two irregular rows of small spine-like tubercles or spines and tufts of long setae, lateral surfaces with 4 (second) or 2 or 3 (third) irregular longitudinal rows of small spines and tufts of short setae, distal margin spiny, mesial surfaces with 2 or 3 irregular longitudinal rows of spine-like tubercles or spines, short vertical rows of spine-like tubercles ventrally, and tufts of short setae, ventral surfaces with transversal rows of tubercles and tufts of setae. Carpus with tufts of long setae and 2 or 3 irregular rows of moderately large spines on dorsal margins (second) or dorsodistal spine and 2 rows of smaller additional spines (third), lateral faces each with weak longitudinal sulcus, 2 or 3 irregular longitudinal rows of small or moderately large spines on distal 2/3, and tufts of short to moderately long setae, mesial surfaces with few small spines distally, ventral surfaces with few tufts of moderately long setae. Merus with dorsal row of low protuberances and tufts of long setae, lateral surfaces with few small spines ventrally (second) or dorsally (third), ventral margins with row of small spines and tufts of moderately long setae (second) or only low protuberances and long setae (third), ventrolateral distal angle with 1 small spine and tufts of moderately long setae. Ischium of second pereopods each with few small spinules on ventromesial margin concealed by long setae; third unarmed, but with tufts of setae.

Sternite XII (pereopods 3) ( Fig. 3A, B ) subrectangular; a median lobule with tufts of long setae.

Pereopod 4 ( Fig. 3C ) with propodal rasp well developed, 3 or 4 rows of ovate scales; dactyl moderately long, 4 corneous spines posterior to claw, preungual process present, slender, almost as long as dactyl, 2 large spines on dorsal surface of propodus and carpus.

Female paired first pleopods ( Fig. 3D ) basial segment with few, moderately long, marginal setae; distal segment with long marginal setae. Brood pouch ( Fig. 3E ) subcircular, large, with fringe of setae.

Telson ( Fig. 3F ) with posterior lobes subcircular, asymmetrical, left larger than right, separated by small, median, shallow cleft, posterior margin of lobes armed with 4 strong, corneous-tipped spines, lateral margins of left lobule with 1 corneous-tipped spines and tufts of long setae; anterior lobes unarmed, with tufts of long setae.

Color. In alcohol, a pinkish tint on an ivory ground ( Glassell 1937).

Habitat. The two specimens were collected on sandy bottom with rock ( Glassell 1937).

Distribution. Until now only known from the type locality, Cabo Pulmo, Gulf of California, Mexico; 90 m ( Glassell 1937).

Remarks. The paratype female of Paguristes aztatlanensis has a compressed carapace and the shield is slightly broader than long; the rostrum is obtusely triangular, shorter than lateral projections. There is a widening of thoracic sternites X and XI with apparent fusion ( Fig. 3A ). According to Glassell (1937: 250), this constriction and distortion of the carapace is the result of the shape of the shell occupied by the hermit crab (i.e., a species of Conus ), which has a very narrow opening. This morphological adaptation has also been observed ( Bouvier 1893; Glassell 1938) in Paguristes digueti , P. sanguinimanus and P. turkayi n. sp., which also occupy shells with a very narrow slit-like aperture (species of Strombus and Conu s).

Glassell (1937) mentioned that P. aztatlanensis shows a close resemblance to P. fecundus Faxon, 1893 , but several morphological characters differentiate these two species. A character not mentioned in the original description of these two species is the presence of spines on the dorsal margin of the propodus and carpus of the fourth pereopods, absent in other known species of Paguristes described from the eastern Pacific. Paguristes aztatlanensis can be distinguished from P. fecundus by: 1) the antennal acicle bearing 3 or 4 spines on mesial margin versus only one spine in P. fecundus ( Fig. 4A ); 2) the dorsal margin of the propodus and carpus of the fourth pereopods is armed with 2 spines in P. aztatlanensis (versus 3 + 3 spines), plus one in the dorsodistal margin of the carpus in P. fecundus ( Fig. 4B ); 3) the posterior margins of the telson in P. aztatlanensis bear few, spaced teeth (4 on each lobe) versus posterior margins of the telson in P. fecundus obscurely toothed (7 or 8 teeth on each lobe; Fig. 4C ). Glassell (1937) stated that these two species differ in the length of the antennal acicle, but it is not so; in both species, the antennal acicle reaches 0.67 of the ocular peduncle length. Glassell (1937) might have been confused by the fact that Faxon (1893: 173) mentioned that “The antennal acicle reaches almost to the end of the peduncle”, but this statement referred to the antennal peduncle, not to the ocular peduncle. Glassell (1937) also mentioned that these two species differ in the armature of the third maxilliped. However, when we examined this feature in the type of P. aztatlanensis , the ventrolateral margin of the merus of the third maxillipeds appeared to be armed with 4 teeth, not unarmed as described by Glassell (1937). In P. fecundus , the third maxilliped is armed with 3 or 4 teeth and, consequently, this character is not adequate to differentiate these two species.

Figures

FIGURE 1. Paguristes aztatlanensis Glassell, 1937. Holotype female (AMNH-12224): A, shield and cephalic appendages, dorsal view; B, left third maxilliped, outer view; C, same, basis and ischium, inner view; D, Palm and carpus of right cheliped, dorsal view (setae omitted); E, palm and carpus of left cheliped, dorsal view (setae omitted); F, left cheliped, mesial view (setae omitted); G, dactyl of right cheliped, mesial view (setae omitted). Scales: A, 5 mm; D‒G, 3 mm.

FIGURE 2. Paguristes aztatlanensis Glassell, 1937. Holotype female (AMNH-12224): A, left second pereopod, mesial view; B, same, lateral view; C, left third pereopod, mesial view (setae omitted); D, left third pereopod, lateral view (setae omitted). Scales: 5 mm.

FIGURE 3. Paguristes aztatlanensis Glassell, 1937: A, C–F, holotype female (AMNH-12224); B, paratype female (AMNH- 12225). A, B, sternites X–XII of chelipeds, second and third pereopods; C, left fourth pereopod, lateral view, setae omitted; D, first female pleopod; E, brood pouch; F, telson, dorsal view. Scales: A, B, 2 mm; C–F, 1 mm.

FIGURE 4. Paguristes fecundus Faxon, 1893, holotype (CRU-4523): A, carapace and abdomen, dorsal view; B, fourth left pereopod, lateral view; C, telson, dorsal view. (Photographs by Adam J. Baldinger).