Tetralobistes bicentenarius, Ayón-Parente, Manuel & Hendrickx, Michel E., 2010

Ayón-Parente, Manuel & Hendrickx, Michel E., 2010, A new genus and new species of hermit crab (Crustacea: Anomura: Paguroidea: Diogenidae) from the eastern tropical Pacific, Zootaxa 2677, pp. 49-59 : 52-58

publication ID	https://doi.org/ 10.5281/zenodo.199263
DOI	https://doi.org/10.5281/zenodo.6208347
persistent identifier	https://treatment.plazi.org/id/03C587ED-9F2C-FFF2-FF47-F532FCE2F9AB
treatment provided by	Plazi
scientific name	Tetralobistes bicentenarius
status	sp. nov.

Treatment

Tetralobistes bicentenarius View in CoL sp. nov.

( Figs 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Type material. Holotype: female (SL 2.10 mm), Matanchen Bay, Nayarit, Mexico, 21º28.83’ N, 105º12.02’ W, 1.0– 1.5 m, snorkel, 0 4 Nov 2006 (EMU-8730). Paratypes: Matanchen Bay, Nayarit, 21º28.83’ N, 105º12.02’ W, 0.5–1.5 m, snorkel, 3 males (SL 0.95–1.36 mm), 1 female (SL 1.20 mm), 26 June 2005 (EMU- 8731); 5 males (SL 0.90–1.90 mm), 1 female (SL 1.40), 1 ovig. female (SL 1.60 mm), 0 4 Nov 2006 (EMU- 8732); 1 male (SL 1.89 mm), 0 4 Nov 2006 ( LACM CR 2006-022.1); 1 male (SL 1.78 mm), 0 4 Nov 2006 ( CNCR 26182); 3 males (SL 0.88–1.68 mm), 0 7 Oct 2010 (EMU-8866).

Description. Biserial phyllobranchiae. Shield ( Fig. 1 View FIGURE 1 A) longer than broad; anterolateral margins sloping; anterior margin between rostrum and lateral projections concave; posterior margin truncate, slightly convex; dorsal surface anteriorly rugose and with short transversal rows of denticles or spines accompanied by tufts of long setae. Rostrum short, bluntly triangular or ending in small spine, equal or slightly exceeding lateral projections, not reaching bases of ocular acicles. Lateral projections bluntly triangular, each armed with small or moderately large marginal spine. Branchiostegites with small spines or spinules on dorsal and distal margins, concealed by tufts of long setae.

Ocular peduncles long ( Fig. 1 View FIGURE 1 A), 0.60 length of shield, broader basally; cornea weakly dilated, width about 0.60 basal width of cornea. Ocular acicles long, subtriangular or subrectangular, broader basally, contiguous along their mesial margin and ending in large spines, lateral margin armed with 3 to 6 spines, mesial margin unarmed.

Antennular peduncles ( Fig. 1 View FIGURE 1 A) long, when totally extended, exceeding by 0.75–0.80 length of ocular peduncles; ultimate and penultimate segments unarmed, with few tufts of long setae; basal segment armed with 1 large spine at ventromesial distal margin, distal and subdistal lateral margins with moderately large spines and tufts of long setae.

Antennal peduncles ( Fig. 1 View FIGURE 1 A) long, equaling or slightly exceeding ocular peduncles; fifth segment with few tufts of moderately long setae; fourth segment with dorsodistal spine and few tufts of setae; third segment with large spine at mesiodistal margin, distal margin with tufts of long setae; second segment with dorsolateral distal angle produced, ending in large acute spine, lateral margin with small subdistal spine, mesial margin unarmed, dorsomesial distal angle with one large or moderately large spine, mesial margin setose; first segment unarmed, ventral margin produced. Antennal acicles triangularly truncated, with terminal spine and spines on mesial margin, reaching to distal margin of fourth segment; mesial margin armed with row of 3 or 4 (juveniles) or 5 or 6 (adult) large, corneous-tipped spines, partially concealed by long setae, lateral margin unarmed. Antennal flagella moderately long, usually not exceeding tip of chelipeds; articles each with very long setae on ventral margin.

Third maxilliped ( Fig. 2 View FIGURE 2 E) with basis-ischium fusion incomplete; basis usually with one small spine; ischium with crista dentata composed of 23–25 corneous denticles; merus with 2 or 3 large spines on ventral margin, dorsodistal margin with 1 moderately large spine; carpus, propodus and dactyl unarmed.

Chelipeds ( Fig. 1 View FIGURE 1 B, C) similar, each with dactyl moderately long, 1.25 longer than palm, terminating in moderately large or large corneous-tipped claw, overlapped by fixed finger; cutting edge with row of calcareous teeth; dorsomesial margin with 2 or 3 rows of large, corneous-tipped spines and tufts of plumose setae; dorsal surface with 1 row of spines and tufts of plumose setae; mesial surface with irregular vertical rows of single or bifid corneous spines accompanied by pinnate setae; ventromesial margin with row of large, corneous-tipped spines; ventral surface with tufts of setae. Palm moderately long, equaling length of carpus; dorsomesial margin with 4 or 5 prominent corneous-tipped spines, dorsolateral margin with row of strong corneous-tipped spines increasing in size distally on the fixed finger; dorsal surface slightly concave on middle surface, with 3 rows of large corneous-tipped bifid or trifid spines, accompanied with tufts of plumose setae, 1 row extending on fixed finger; mesial surface with spine-like or denticulate tubercles, and corneous spines accompanied with tufts of setae; lateral and ventral surfaces with scattered denticulate or spine-like tubercles, accompanied with tufts of setae; fixed finger with calcareous teeth on cutting edge, terminating in long corneous claw. Carpus moderately short, about 0.50 length of merus; dorsomesial margin with 6 large, corneous-tipped spines accompanied with tufts of long stiff setae; dorsal surface with 2 irregular longitudinal rows of large or moderately large spines, distal margin with 1 to several small, corneous-tipped spines and tufts of long plumose setae; dorsolateral margin not noticeably delimited; mesial surface with scattered granules or spine-like tubercles and tufts of short setae; lateral surface with numerous spine-like tubercles accompanied by tufts of long setae; ventral surface unarmed. Merus subtriangular; dorsal face with row of small spines increasing in size, becoming transverse rows of moderately large spines distally, often corneoustipped spines distally, accompanied by tuffs of long setae, distal margin with row of moderately large corneous-tipped spines extending on lateral and mesial margins; lateral face granulose and spiny subdistally and distally, ventral margin with row of corneous-tipped spines and tufts of long plumose setae; mesial face with few spinules on distal and subdistal margins and scattered tufts of short setae, ventromesial margin with row of small, corneous-tipped spines and tufts of long plumose setae; ventral surface with tufts of long plumose setae. Ischium with row of small spines on ventromesial and dorsolateral margins, distal margin with long plumose setae. Coxa with 1 large, sharp spine at ventromesial angle and tufts of long stiff setae.

Left and right pereopods 2 and pereopods 3 similar ( Fig. 3 View FIGURE 3 A–D), differing somewhat in armature. Dactyls 1.00–1.08 length of propodi; dorsal margins each with row of small corneous spines on proximal 0.50 and tufts of long plumose setae; mesial and lateral faces each with shallow longitudinal groove proximally, and 1 or 2 irregular longitudinal rows of tufts of short setae; ventral margins each with row of 10–13 minute corneous spines increasing in size distally. Propodi 1.48–1.92 length of carpi; dorsal surfaces each with 2 longitudinal rows of flattened denticles accompanied by tufts of long plumose setae; lateral surface with 2 rows of tufts of short setae, 1 middle row usually bearing denticulate, flattened tubercles, and another row ventrally; mesial surfaces each with 3 longitudinal rows of denticulate, flattened tubercles accompanied by tufts of short setae; ventral surfaces each with 2 longitudinal rows of tufts of short setae. Carpi 0.63–0.80 length of meri; dorsal surfaces each with 2-4 irregular rows of moderately large, corneous-tipped spines accompanied by tuffs of long setae (second) or with 2 or 3 rows of denticulate tubercles, and 1 or 2 moderately large, corneous-tipped spines distally (third); mesial surfaces naked; lateral surfaces each bearing shallow longitudinal groove, ventrally flanked by short, transverse rows of denticles accompanied by tuffs of long setae. Meri flattened laterally; dorsal surfaces with spinules partially concealed with tufts of long plumose setae (second) or with only tufts of long plumose setae (third); mesial and lateral surfaces with some flattened denticulate tubercles and tufts of short setae; ventral margins each with double irregular row of denticles and tufts of long plumose setae (second) or only tufts of setae (third). Ischia (second) with 2 small spines on ventromesial margin and 3 or 4 dorsodistal spinules, or with some denticulate tubercles on mesial face (third).

Sternite XII (third pereopods) ( Fig. 1 View FIGURE 1 F) with anterior lobe subrectangular, bearing pair of protuberances and tufts of long setae.

Fourth pereopods simple ( Fig. 3 View FIGURE 3 E); dactyl short, about 0.77 length of propodus, setose, with 2 large corneous spines on ventrolateral margin posterior to claw; propodi each with 3 rows of ovate scales in propodal rasp; carpi as long as propodi, each with small dorsodistal spine.

Male first pleopod paired, modified as gonopods ( Fig. 1 View FIGURE 1 D, E). Basal lobe (see arrow, bl) bearing tuft of long setae, mesial margin naked; inferior lamella with row of long setae on lateral margin, distal margin (see arrow, dm) with row of bifid and multifid corneous, curved spines extending down mesial face; internal lobe (see arrow, il) with marginal setae. Pleopods 2 absent, 3–5 unpaired ( Fig. 1 View FIGURE 1 G), exopod very well developed, endopod absent. Female with paired gonopores, without first paired pleopods, pleopods 2–4 ( Fig. 1 View FIGURE 1 H, I) with both rami well developed, pleopod 5 ( Fig. 1 View FIGURE 1 J) as in male; brood pouch represented by row of setae.

Telson ( Fig. 1 View FIGURE 1 K) with posterior margin divided in 4 lobes; outer left lobe longer than outer right, subrectangular, armed with 2 or 3 distal spines and 2–4 lateral spines; middle lobes subquadrate, each with 11–13 small spines; outer right lobe subrectangular, distal and lateral margins each with 2 or 3 strong spines; anterior section of telson separated from posterior section by indentation, weakly bilobate, lobes unarmed or each with 1–3 small spines and long stiff setae.

Color ( Fig. 4 View FIGURE 4 A, B). In life, abdomen orange with numerous red dots. Telson and uropods pale-yellow or white. Posterior and anterior portions of carapace reddish-brown over yellow-orange background. Ocular acicle pale-yellow to white, with middle reddish-brown band. Base of ocular peduncles with 1 reddish-brown oblique band, 1 rose and 1 reddish-brown band; distal 0.66 light olive. Cornea golden. First, second, third and proximal 0.50 of antennal segments reddish, distal 0.50 of fourth and fifth segments light olive. Antennal acicles whitish-rose proximally, reddish-brown in middle, and olive distally. Antennal flagella light olive, ventral setae transparent. In juveniles, dactyls and fixed fingers of chelipeds white; chelae dark-brown; palms yellow-orange with small reddish-brown spots on dorsal, lateral and ventral surfaces; mesial faces each with oblique longitudinal reddish-brown band; carpi yellow-orange with small reddish-brown spots on dorsal faces; meri reddish-brown, each with middle whitish-rose band. Walking legs with white dactyls. Claws amber; propodi white on proximal halves and reddish-brown distally; carpi white each with brown band on proximal third; meri brown, each with white band; ischia reddish-brown dorsally, ventrolateral and ventromesial faces yellow-orange. In adults specimens chelipeds reddish-brown with small white spots; dactyls and fixed fingers each with white band posterior to claw; carpi reddish-brown; meri reddish-brown each with whitish-rose subdistal band; dactyls of ambulatory legs reddish-brown each with 2 white bands, 1 proximal other distal; propodi reddish-brown, each with 2 short, white, longitudinal bands proximally on lateral surface and 1 white band on mesial surface; carpi and meri reddish-brown with small white spots.

Etymology. The species is named in commemoration of the 200 years of the independence of Mexico (“bicentenario”), and is a combination of the Latin prefix, bi (two), and Latin word, centenarius (centenary), in the masculine.

Distribution. Known only from the type locality.

Habitat. Specimens were captured on rock covered with green algae, in 0.5–1.5 m depth. The species occupied different types of gastropods shell, among them Costoanachis varia (Sowerby, 1832) , Olivella cf. aureacincta Carpenter, 1857, Stramonita biserialis (Blainville, 1832) , Mitrella sp., and Terebra sp.

Variation. Small differences were observed in armature of chelipeds between juvenile and adult specimens. In juveniles the dorsal surface of the palm bears single spines, whereas in adults corneous-tippedbifid or trifid spines are present. As noted earlier, the color pattern also varies between juveniles and adults.

Remarks. There is a superficial resemblance between Tetralobistes bicentenarius gen. nov., sp. nov. and Areopaguristes mclaughlinae from the Mexican Pacific. Both species have a short rostrum, multispinous, contiguous ocular acicles, antennular and antennal peduncles of comparable length, antennal flagella bearing long setae ventrally, and subequal chelipeds with tipped fingers. Both species also feature modified male first pleopods with distal margin of the inferior lamella bearing a row of simple, bifid and multifid corneous, curved spines. In the females of both species the first pleopods and brood pouch are absent. However, in addition to the generic differences (see above), their color pattern is different, the antennal acicles are broader and shorter in T. bicentenarius gen. nov. and sp. nov. than in A. mclaughlinae , and the armature of chelipeds and ambulatory legs is different between the two species.