Pseudopaguristes flavioculus Komai & Miller & Malay 2022, n. sp.
Creators: name: Komai, Tomoyuki
name: Miller, Allison K.
name: Malay, Maria Celia D.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Diogenidae
Pseudopaguristes
Pseudopaguristes flavioculus

description: Pseudopaguristes flavioculus n. sp.
(Figs. 1–6)
Pseudopaguristes sp. — Malay et al. 2021: 12.
Material examined. Holotype. SIO-BIC C14508, male (sl 2.7 mm), off Sarigan Island, Northern Mariana Islands, station AKM-SAR-03, 16.711N, 145.808E, 131–133 m, 24 June 2015, crab trap.
Description. 12 pairs of gills present: 8 functional pairs including 2 arthrobranchs each on pereopods 2–4 and pleurobranchs on thoracomeres 6 and 7, all these gills distally quadriserial; 2 arthrobranchs on maxilliped 3 reduced into simple rudimentary buds, those on cheliped (= pereopod 1) reduced to bi-lobed bud (anterior) or row of tiny lamellae (posterior) (Fig. 1A).
Shield (Fig. 1B) 1.3 times longer than broad; dorsal surface with scattered spinules laterally. Lateral projections broadly triangular, with tiny terminal spinule. Rostrum moderately long, triangular, reaching well beyond bases of ocular acicles, without terminal spinule. Branchiostegites each with row of spines on dorsal margin in distal half.
Ocular peduncles (Fig. 1B) subequal; moderately slender; 0.7 length of shield; corneas not dilated, corneal width 0.2 times of ocular peduncle length. Ocular acicles moderately large, subtriangular, with 2 (left) or 3 (right) terminal spinules.
Antennular peduncles (Fig. 1B, C), when fully extended, not reaching bases of corneas. Ultimate and penultimate articles glabrous; ultimate article short, becoming deep distally, 0.4 times as long as shield, 2.6 times as long as distal height; penultimate article ventral margin convex, unarmed. Basal article with slender spine on dorsolateral margin of statocyst lobe, ventrodistal margin not particularly produced.
Antennal peduncles (Fig. 1B, D, E), when fully extended, not reaching to bases of corneas. Article 5 unarmed. Article 4 with small dorsodistal spine and even smaller ventrodistal spine. Article 3 with prominent ventrodistal mesial spine. Article 2 with dorsolateral distal angle produced, terminating in cluster of 4 spines; dorsomesial distal angle with small spine. Article 1 ventrodistal margin produced, but unarmed. Antennal acicle overreaching midlength of fully extended peduncular article 5; terminating in bifid spine, dorsomesial margin with row of 5 spines, ventromesial margin with row of 7 spines, lateral margin with 3 subterminal spines (Fig. 1F). Antennal flagellum (Fig. 1G) moderately long, 1.7 times as long as shield, overreaching tip of right cheliped; each article with few short setae, and 2 or 3 longer setae every 2 or 3 articles.
Maxilliped 3 endopod (Fig. 1H, I) with basis bearing few acute denticles on dorsomesial margin. Ischium crista dentata consisting of 1 hooked corneous-tipped spine at ventromesial distal angle followed by row of minute, fine corneous spinules. Merus ventral margin with 4 spines; dorsodistal margin with spinule. Carpus with 1 dorsodistal spinule. Exopod reaching distal margin of endopod carpus.
Chelipeds grossly unequal, right distinctly larger; armature dissimilar; most spines on chela corneous-tipped; setae sparse (Figs. 2, 3A–D). Right cheliped (Figs. 2A, B, 3A, B) with dactyl subequal in length to palm, slightly curved ventrally, somewhat deflexed at base against horizontal plane of palm; dorsomesial margin with row of small spines and few sparse setae, dorsal surface with 2 irregular longitudinal rows of small spines; mesial surface with few tiny to small spines adjacent to dorsomesial margin; occlusal margin with row of 3 moderately small, blunt calcareous teeth, 1 prominent calcareous tooth near proximal angle, and row of small corneous teeth in distal 0.2; terminating in small corneous claw and slightly overlapped by fixed finger. Palm 1.1 times as long as wide, 1.2 times length of carpus, dorsoventrally somewhat swollen, but becoming thinner on fixed finger; dorsomesial margin with row of 8 spines increasing in size proximally; dorsolateral margin with continuous row of small spines, becoming larger and more widely-spaced on fixed finger; dorsal surface of palm and fixed finger with numerous, but not densely-packed, small spines; mesial face with few spinules or minute tubercles; lateral face with scattered minute tubercles; ventral surface with sparse tufts of setae; occlusal margin of fixed finger with row of small calcareous teeth becoming smaller and more obtuse distally; terminating in small corneous claw. Carpus slightly more than 0.5 length of merus; dorsomesial margin with row of 5 prominent spines, dorsal surface with few spinules or minute denticles, but without conspicuous spines; lateral face with few granules, ventrolateral distal angle with small spine; mesial face unarmed, with few long setae along distal margin. Merus dorsodistal margin only with 1 tiny spinule mesially; dorsal margin with1 subdistal transverse rows of spines, extending laterally, row of tiny spines becoming smaller proximally; lateral face with scattered granules and minute setae, ventrolateral margin with row of small spines, including one at distal angle; mesial face almost glabrous, without armature, ventromesial margin with row of spines strongest distally, and 1 additional tiny spine on distomesial margin. Ischium with row of small spines on ventromesial margin. Coxa with small spine at ventromesial distal angle, while ventrolateral distal angle unarmed.
Left cheliped (Figs. 2C, D, 3C, D) reaching slightly beyond midlength of dactyl of right; dactyl and fixed finger slightly curved ventrally. Dactylus 2.3 times as long palm, armed with row of small spines on dorsomesial margin, dorsal surface with few spinules; mesial face with few spinules mainly along midline; ventral surface unarmed; occlusal margin with row of small, contiguous corneous teeth in distal 0.7, unarmed in proximal 0.3, terminating in large corneous claw. Palm with dorsomesial margin armed with row of 5 large spines, dorsal surface with irregular longitudinal rows of small to moderately small spines, 2 rows extending onto fixed finger; dorsolateral margin not delineated, but rounded surface with scattered small spines; mesial face with few spinules; ventral surface with low protuberances distally; occlusal margin of fixed finger with row of small calcareous teeth, terminating in large, corneous claw. Carpus with row of 5 spines on dorsomesial margin, dorsolateral margin also with row of small spines, dorsal surface with row of tiny spines on midline; mesial face unarmed; lateral face with scattered tiny spines, ventrolateral distal angle with small spine, proximal margin unarmed. Merus with 2 tiny spines at dorsodistal margin; dorsal surface with transverse rows of small spines and spinules, extending onto lateral and mesial faces, followed by row of small spines becoming obtuse proximally; lateral face with scattered minute tubercles, ventrolateral margin with row of small spines in distal half; mesial face unarmed except for 2 tiny spines adjacent to ventromesial margin, ventromesial margin slightly expanded, with row of large spines, strongest medially; ventral surface with few small spines. Ischium with row of small denticles on ventromesial margin; lateral face also with few minute spines or tubercles ventrally. Coxa with small spine at ventromesial distal angle, while ventrolateral distal angle unarmed.
Pereopods 2 and 3 (ambulatory legs) (Figs. 4, 5) moderately stout, left second slightly shorter than others. Dactyli (see also Fig. 3F, E) 1.2–1.3 times longer than propodi, each terminating in moderately strong corneous claw; dorsal margins each with row of tiny, corneous-tipped spines on proximal half, and sparse setae (second) or with only setae (third); lateral faces of second and third, and mesial faces of second with few short setae; mesial faces of third each with sparse minute setae; ventral margins each with row of 11 or 12 small corneous spines and 1 slender subterminal spine closely contiguous with terminal claw. Propodi considerably longer than carpi; dorsal margins each with row of small spines and sparse setae (second), or only sparse setae (third); mesial faces with tufts of setae, setae more numerous on third; ventral margins of second pair each with small corneous spinule at distal margin, and 1 additional subdistal spinule, third pair with only sparse setae. Carpi approximately 0.75 length of meri; dorsal margins each with single row of spines mesially (second) or only with dorsodistal spine (third); lateral, mesial and ventral surfaces unarmed, but with sparse setae (setae numerous on dorsomesial faces of third). Meri each with single row of small spines in proximal 0.5 to 0.7 of dorsal margin (spines less acute on third); lateral and mesial faces unarmed; ventral margins each with partially double row of small spines (second) or unarmed (third). Ischia with spinules on dorsal margins, less acute on third.
Pereopod 4 (only left preserved) (Fig. 3G–I) with dactylus subequal in length to propodus measured along dorsal margin, stiffly setose, prominent, slender preungual process at base of claw giving chelate appearance; ventral margin with 3 corneous spinules. Propodus with 2 rows of corneous scales in propodal rasp. Carpus with small dorsodistal spine and thick tuft of stout, flattened setae (Fig. 3J) on ventral margin distally. Merus unarmed. Ischium with small ventromesial distal spine.
Pereopod 5 chelate.
Thoracic sternite 6 anterior lobe (Fig. 1J) wide, with slightly convex anterior margin; posterior lobe not divided.
Pleopods 1 (Fig. 3K) symmetrical, each with tuft of setae on basal lobe; inferior lamella somewhat twisted distally, distal margin with row of very small, curved spines not extending down to mesial margin; internal lobe moderately small, with row of moderately long setae on mesial margin; external lobe not reaching distal margin of inferior lamella. Pleopods 2 (Fig. 3L–N) also symmetrical; distal article with blunt shoulder at about midlength, distal part flattened, bearing marginal row of setae on distal to mesial margin.
Posterior part of pleon and telson broken off, not preserved.
Colouration in life. Shield generally whitish with pink rostrum; posterior carapace whitish dorsally, pinkish laterally, branchiostegite also pinkish; ocular peduncles yellow with tinge of orange basally, cornea bright yellow; antennular peduncle article 2 yellow, article 1 with tinge of orange; antennal peduncle article 2 pinkish, article 4 generally orange with white distal band, antennal acicle bright yellow; antennal flagellum translucent with bands of dark brown every few articles; chelipeds and pereopods 2–4 entirely pink (Fig. 6).
Distribution. Presently known only from off Sarigan Island, Northern Mariana Islands, at a depth of 131– 133 m.
Remarks. One of the original diagnostic characters of Pseudopaguristes was the unequal, dissimilar chelipeds with the right largest in the male (McLaughlin 2002). Subsequent discovery of new species and reassignment of species from Paguristes has discounted the significance of this character to interspecific level in the genus (Asakura 2004; Rahayu 2005, 2008). The monophyly of Pseudopaguristes as currently diagnosed is questionable in the perspective of molecular phylogenetic analysis (cf. Craig 2021). In the present new species, the right cheliped is distinctly larger than the left cheliped in male, and in this regard, it is comparable with P. bollandi, P. janetkae, P. kuekenthali, and P. shidarai (cf. Asakura & McLaughlin 2003; Asakura 2004; Rahayu 2005, 2008). In the general armature of the cheliped palms, P. flavioculus n. sp. is most similar to P. janetkae, the type species of Pseudopaguristes: in these two species, the dorsal surfaces of the palms are armed with scattered small spines. In P. bollandi and P. shidarai, the dorsal surface of the right palm bears scattered tubercles instead of spines (tubercles are relatively larger and fewer in P. shidarai than in P. bollandi) (Asakura & McLaughlin 2003; Asakura 2004); in P. kuekenthali, the dorsal surface of the right cheliped palm is covered with small pointed granules (Haig & Ball 1988). Pseudopaguristes flavioculus n. sp. differs from P. janetkae in the presence of a median row of tiny spines (seven in number) on the dorsal face of the left cheliped carpus (Fig. 3D). In P. janetkae, there is a row of two or three spines, which are stronger than those of P. flavioculus n. sp., along the midline of the dorsal face (McLaughlin 2002: figs. 11, 22). The armature of the carpus of the right cheliped seems to be also different between P. flavioculus n. sp. and P. janetkae: in the new species, the carpus of the right cheliped is devoid of conspicuous spines on the dorsal face (Fig. 3B), whereas there are scattered small but conspicuous spines on that face in P. janetkae (cf. McLaughlin 2002: fig. 10). The distal two articles of the maxilliped 3 are much slenderer in P. flavioculus n. sp. than in P. janetkae (cf. Fig. 1H versus McLaughlin 2002: fig. 6). The carpus of the pereopod 4 is armed with a small dorsodistal spine in the new species (Fig. 13G), but such a spine is absent in P. janetkae (cf. McLaughlin 2002: fig. 7). Finally, the living colouration is quite different between P. flavioculus n. sp. and P. janetkae (Fig. 6 versus McLaughlin 2002: pl. 1). For example, in the new species, the ambulatory legs are uniformly pink. In contrast, in P. janetkae, the proximal portions of meri are cranberry-red, with the color continuing distally in an oblique, ventrally-directed pattern, and the dorsodistal, lateral and mesial faces are distally light yellow and white, tinged with cranberry-red; and the carpi, propodi and dactyli are light cream tinged with yellow.
In the general colour pattern, P. bollandi is superficially similar to P. flavioculus n. sp.; in both species, the chelipeds and ambulatory legs are uniformly coloured (Fig. 6 and Asakura & McLaughlin 2003: fig. 8). Nevertheless, details are still different. In the new species, the ocular, antennular and antennal peduncles are generally yellow with the pink article 2 of the antennal peduncle, whereas in P. bollandi, the ocular and antennal peduncles are generally red. In addition to the different armature of the cheliped palms as mentioned above, the new species is distinguished from P. bollandi by the presence of more numerous, smaller spines on the dorsal midline of the left cheliped carpus (seven in number versus four in P. bollandi).
The present new species represents the third species of Pseudopaguristes known from the Mariana Islands. The other two are P. janetkae and P. monoporus (cf. Paulay et al. 2003; Malay et al. 2021). The real distribution of the new species remains unknown. Pseudopaguristes janetkae is so far known only from Japanese Ryukyu Islands besides the Marianas (Arima 2004), whereas P. monoporus has been recorded from wide areas in the Indo-West Pacific (Rahayu 2005; Malay et al. 2021).
Etymology. From the combination of the Latin words, flavus (= yellow) and oculus (= eye), in reference to the living colouration of the ocular peduncles in the new species. Used as a noun in apposition.
description: Published as part of Komai, Tomoyuki, Miller, Allison K. & Malay, Maria Celia D., 2022, A new species of the diogenid hermit crab genus Pseudopaguristes McLaughlin 2002 from the Northern Mariana Islands, Micronesia, pp. 570-582 in Zootaxa 5175 (5) on pages 572-580, DOI: 10.11646/zootaxa.5175.5.6, http://zenodo.org/record/7009572