Paguristes pusillus Henderson, 1896

Mclaughlin, Patsy A. & Rahayu, Dwi Listyo, 2005, Two new species of Paguristes sensu stricto (Decapoda: Anomura: Paguroidea: Diogenidae) and a review of Paguristes pusillus Henderson, Zootaxa 1083, pp. 37-62 : 55-60

Paguristes pusillus Henderson, 1896 ( Fig. 6 )

Paguristes pusillus Henderson 1896: 526 ; Alcock & Anderson, 1897, pl. 31: fig. 4, 4a; Alcock, 1905: 37 , pl. 3: fig. 3; Southwell, 1906: 216.

? Paguristes pusillus—Balss, 1913: 40; Yokoya, 1933: 43; Miyake, 1978: 37; Wang, 1983: 50, pl. 1: fig. 3; Huang, 1989: 232, fig. 192; Wang, 1992: 60 (list); 1994: 568 (list); Rahayu, 2000: 392; (in press) (see Remarks).

? Paguristes p. pusillus — Wang & Tung, 1982: 368 (see Remarks).

Not Paguristes pusillus var—Nobili, 1906: 88 (see Remarks).

Not Paguristes pusillus — Thompson, 1943: 414 (= Paguristes lewinsohni n. sp.)

Material Examined. Sri Lanka (as Ceylon), 1 female (3.3 mm), Investigator stn 59, coll. J.R. Henderson, NMH 1903.4.6.209.

Description. Thirteen pairs of distally quadriserial gills. Shield ( Fig. 6 a) slightly longer than broad; dorsal surface damaged in posterior 0.7. Rostrum triangular, reaching mid­length of ocular acicles, somewhat depressed distally, with minute terminal spinule. Lateral projections triangular, each with submarginal terminal spinule. Branchiostegites with few moderately prominent small spines on dorsal margins distally, largest at distal margin. Posterior carapace with posterior median plate moderately broad, weakly calcified anteriorly.

Ocular peduncles subequal in length, left slightly longer, 0.9 length of shield; corneal diameter 0.2 of peduncular length. Ocular acicles subovate, each terminating bluntly, with 1 or 2 terminal spines; separated basally basal width of 1 acicle.

Antennular peduncles when fully extended not quite reaching basal margins of corneas. Ultimate segment unarmed; penultimate segment with small spine on ventral surface at midlength; basal segment with ventrolateral distal margin produced into spiniform process, 1 spine on lateral margin of statocyst lobe.

Antennal peduncles not reaching midlength of ocular peduncles; fifth segment unarmed; fourth segment with small dorsodistal spine; third segment with prominent ventrodistal spine; second segment with dorsolateral distal angle produced, terminating in simple or bifid spine, dorsomesial distal angle with small spine; first segment with ventrodistal angle produced, unarmed. Antennal acicle reaching approximately 0.8 of fifth peduncular segment, with terminal bifid spine; mesial margin with 1 spine, lateral margin with 2 or 3 spines. Antennal flagellum short, not quite as long as carapace; each article with only 1 or 2 moderately long setae.

Chelipeds with propodal/carpal counterclockwise rotation of approximately 30°; subequal, left ( Fig. 6 b) slightly larger; armature similar; dactyl and fixed finger without hiatus. Dactyl with row of moderately small, tuberculate spines on dorsomesial margin, dorsal surface with few tubercles; mesial face ( Fig. 6 c) with longitudinal row of tuberculate, weakly corneous­tipped spines, extending nearly to tip and few smaller tubercles ventrally; cutting edge with row of very small calcareous teeth and few corneous teeth distally; terminating in small corneous claw and very slightly overlapped by fixed finger. Palm with row of tuberculate spines on dorsomesial margin, dorsolateral margin not delimited, convex dorsal surface with covering of smaller tuberculate spines and tubercles, extending nearly entire length of fixed finger; mesial face with few low tubercles; ventral surface with scattered tubercles laterally and row of corneous­tipped tubercles and sparse tufts of setae extending almost entire length of fixed finger; cutting edge of fixed finger with row of small calcareous teeth; terminating in small corneous claw. Carpus with row of prominent tuberculate spines on dorsomesial margin, distal margin with tubercles, dorsal surface with covering of smaller tuberculate spines, dorsolateral margin not delimited; ventrolateral distal angle with acute spine; mesial face with few low tubercles. Merus with 1 prominent spine at dorsodistal margin and several smaller spines on distal margin laterally; dorsal margin with subdistal row of moderately large bi­ or multifid spines, decreasing in size proximally; mesial face unarmed but with few very small spinules on distal margin ventrally, ventromesial margin with several prominent spines; lateral face with numerous scattered tubercles, largest ventrally, ventrolateral margin with row of small tubercles. Ischium with row of small, tuberculate spines on ventromesial margin.

Second and third pereopods ( Fig 6 d–g) with dactyls approximately 1.4 length of propodi; dorsal margins each with row of long stiff bristles, also row of small, often corneous­tipped spines on second pereopods, low protuberances on third; lateral faces each with moderately faint longitudinal sulcus proximally and row of sparse tufts of short setae dorsally; mesial faces of second pereopods each with longitudinal sulcus flanked dorsally and ventrally by row of tiny corneous spinules and few low protuberances ventrally; third with dorsal and ventral row of tiny corneous spinules but no sulcus; ventral margins each with row of 16–19 corneous spines and sparse setae. Propodi of second pereopods each with row of spines accompanied by sparse tufts of setae; dorsal surfaces of third with low protuberances and tufts of setae; mesial faces of second pereopods with numerous scattered tubercles, third with tubercles only ventrally; ventral margins each with row of spinulose protuberances (third pereopods) or tuberculate spines (second). Carpi each with sparse tufts of setae and irregular row of moderately small to moderately large spines on dorsal margins, second pereopods also with few additional tiny spines laterally; lateral faces each with weak longitudinal sulcus; ventral surfaces with few tufts of setae. Meri each with dorsal row of low protuberances and sparse tufts of setae; ventral margins each with short row of prominent spines and few setae (second) or only 1 or 2 spines (third). Ischia each with 1 or 2 spinules on ventromesial margin distally. Fourth pereopod (left missing) with prominent preungual process at base of claw; carpus without dorsodistal spine.

Male not seen. Female paired first pleopods 2­segmented. Brood pouch large, almost fan­shaped, margins weakly scalloped, with marginal long setae. Tergal thickenings above acetabula of pleopods 2–4 with fringe of long, moderately dense setae. Eggs large, diameter 1.2 mm ( Alcock, 1905 ).

Telson ( Fig. 6 h) with moderately deep lateral incisions separating anterior and posterior portions; slightly asymmetrical posterior lobes separated by very small V­shaped median cleft; lobes subtriangular with rounded apices, terminal margins unarmed but each with row of long setae, partially extending onto lateral margins.

Color in preservative. “The eye­stalks, antennal, and antennular peduncles are purplish. The meral joints of the chelipeds exhibit a single pale blue spot on the outer surface and two similar spots on the inner surface ­ all three near the distal ends of the joints. The ambulatory legs are.faintly banded with red” ( Henderson, 1896). Alcock (1905) reported that in preservative the meri of the chelipeds each had a well defined white patch on faint pink ground

Habitat. Not reported.

Distribution. Known with certainty only from northeast of Sri Lanka; 51 m.

Remarks. Although not a paratype of P. pusillus , the specimen in The Natural History Museum collection is accompanied by a note stating that this specimen was compared with the type series (apparently by Henderson); it bears the IM number 1623/7. As with the other Indian materials, loan of the type series, three males and two ovigerous females, was not possible, but it is reasonable to assume that the identifications by Alcock (1905) and Southwell (1906) were correct. The illustration by Alcock & Anderson (1897) was of a specimen of the type series.

The accuracy of the subsequent records of P. pusillus is uncertain. Although Nobili’s (1906) material has not been reexamined, his description of a species he referred to as P. pusillus var. from the Persian Gulf clearly indicated his doubts that his taxon was conspecific with Henderson’s (1896) species. Balss (1913) listed one male and one female from Sagami Bay, and said only that they agreed completely with Alcock’s (1905) description. Efforts to locate Balss (1913) specimens have been unsuccessful. Yokoya (1933) listed one specimen of his own and cited Balss’ (1913) report, but provided no pertinent information that would identify his specimen. His material apparently is also no longer extant.

Thompson’s (1943) specimens from the Arabian Sea and Gulf of Oman were reexamined. All of the specimens from John Murray station 45 and the ovigerous female from station 72 represent P. lewinsohni n. sp. Thompson (1943) had two additional specimens from station 72 that he identified as P. balanophilus . We reexamined those two specimens and concur with Thompson’s opinion that they differed from the specimens he attributed to P. pusillus . They do agree with Alcock’s (1905) description of muricated and crystalloid tubercles on the dorsal surfaces of the chelae of P. balanophilus and on one chela, a faint patch of color is still apparent on the mesial face of the merus. Until the type series of P. balanophilus can be examined, we accept Thompson’s (1943) interpretation.

Miyake (1978) stated that he had no personal knowledge of P. pusillus . His diagnosis was quoted directly from Alcock (1905) , and his distributions were based on Alcock , Balss (1913) and Yokoya (1933). However in his key to the species of Paguristes, Miyake (1978: 26) erroneously cited the antennular peduncles as being longer than the ocular peduncles. It is uncertain whether Hendersons (1896) species actually occurs in Japanese waters. The reports of P. p u s i l l u s from the South China Sea by Wang (1992, 1994) and Rahayu (2000) were taken from existing literature and did not involve examined specimens.

When they described the new subspecies, P. pusillus zhejiangensis, Wang & Tung (1982) probably based their very brief, and somewhat contradictory, comparative remarks ( Wang & Tung, 1982: 371) on Alcock & Anderson’s (1897) illustration rather than on actual specimens of P. pusillus . Wang (1983), in a preliminary account on the hermit crabs of China, gave a brief description of a species he identified as P. pusillus ; his illustration bears more resemblance to P. balanophilus that to P. p u s i l l u s. Huang (1989) provided somewhat more detailed information on Henderson’s (1896) taxon, but the information also appears to be based on Alcock’s (1905) description. His illustration was reproduced from Wang’s (1983) previous publication. However, Huang (1989) indicated that his specimen was collected from Putuo Island in the East China Sea. From his description and the illustration, it is impossible to determine what species of Paguristes either Wang (1983) or Huang (1989) may have studied. According to Huang (1989), P. p. zhejiangensis was also collected from the area around Putuo Island. His description was taken almost verbatim from Wang & Tung’s (1982) original account, and his illustration was identical. The illustrated straight, elongate abdomen of this species is not an artistic error. The authors noted that the species commonly inhabited tusk shells and thus the straight abdomen. However, when a specimen was found in a gastropod shell, the abdomen had the typical hermit crab twist. Brief as the description of P. p. zhejiangensis is, it is based on a rather large specimen with a carapace length of 10 mm. Several characters including the ocular peduncles that are shorter than the antennular peduncles, the unequal but similarly armed chelipeds, and elongate ambulatory dactyls (almost as long as the sum of the propodus and carpus combined), have convinced us that this taxon cannot be considered a subspecies of P. pusillus but must be afforded specific rank. The specimens upon which Wang & Tung’s (1982) description was based appear to no longer be extant ( Y.­L. Wang, pers. comm.). Thus we are not able, on the limited data available, to elaborate further on their taxon.

Rahayu (in press) reported P. pusillus based in part on the description of the female used in this study and in part on four males from Indonesian deep waters. The author noted several differences between Henderson’s (1896) specimen and her own, including unequal chelipeds, longer antennal flagella, and appreciably longer ambulatory dactyls. Because we have been unable to examine the type series, it is not possible to determine if the differences observed by Rahayu (in press) represent sexual dimorphism not noted by Henderson (1896) and Alcock (1905) or whether the Indonesian specimens actually represent a distinct but very similar species.

Figures

FIGURE 6. Paguristes pusillus Henderson, 1896, Sri Lanka, Investigator stn 59, female (3.3 mm), (NMH 1903.4.6.209). a, shield and cephalic appendages (aesthetascs and setae omitted); b, carpus and chela of left cheliped (dorsal view, setae omitted); c, dactyl of left chela (mesial view, setae omitted); d, left second pereopod (lateral view); e, dactyl and propodus of left second pereopod (mesial view, setae omitted); f, left third pereopod (lateral view); g, propodus of left third pereopod (ventral view, setae omitted); h, telson. Scales equal 1 mm.