Paguristes balanophilus Alcock, 1905

Rahayu, Dwi Listyo & McLAUGHLIN, Patsy A., 2006, Clarifications of the identities of Paguristes balanophilus Alcock, 1905 and P. calvus Alcock, 1905 (Crustacea, Decapoda, Anomura, Paguroidea, Diogenidae), and the description of another broadly distributed new species, Zoosystema 28 (4), pp. 865-886 : 868-874

Paguristes balanophilus Alcock, 1905

( Figs 1-3 )

Paguristes balanophilus Alcock, 1905: 33 , pl. 3, fig. 1. — Balss 1924: 769. — Thompson 1943: 414. — Gordan 1956: 321 (list). — Tikader et al. 1986: 163 (list). — Morgan & Forest 1991: 686.

Paguristes calvus – Alcock 1905: 35 (in part), not pl. 1, fig. 4 (see Remarks).

Not Paguristes balanophilus – Miyake 1961: 11 (list); 1975: 294, pl. 112, figs 8, 11; 1978a: 29 (list); 1978b: 40, fig. 14, pl. 2, fig. 7; 1982: 97, pl. 33, fig. 1; 1991: 97, pl. 33, fig. 1; 1998: 97, pl. 33, fig. 1. — Miyake et al. 1962: 125 (list). — Matsuzawa 1977: pl. 79, fig. 2. — Miyake & Imafuku 1980: 4 (see Remarks).

TYPE MATERIAL. — Andaman Sea. Investigator , stn 239, 11°49.5’N, 92°55.0’E, 102 m, 14.IV.1898, ♂ lectotype (herein selected) 7.6 mm ( NHM 1903.4.6.181-191) ; 4 ♂♂ paralectotypes 3.8-10.4 mm; 5 paralectotypes ♀♀ 5.0- 7.1 mm; 1 paralectotype ovig. ♀ 7.4 mm ( NHM 1903.4.6.181-191) .

OTHER MATERIAL EXAMINED. — Gulf of Oman. John Murray Expedition, stn 72, 25°38.3’N, 56°26.6’E, 73 m, 26.XI.1933, 2 ♂♂ 6.0 and 8.8 mm ( NHM 1952.6.17.28-29).

Andaman Sea. Investigator , stn 239, 1 ♀ 6.0 mm; 1 ovig. ♀ 6.5 mm ( MNHN Pg 1533) ; 4 ♂♂ 3.6-6.5 mm; 5 ♀♀ 6.4-7.4 mm ( NHM 1903.4.6.181-191) .

TYPE LOCALITY. — Andaman Sea, Investigator , stn 239, 11°49.5’N, 92°55.0’E, 102 m.

DISTRIBUTION. — Arabian and Andaman Seas.

DESCRIPTION

Thirteen pairs of quadriserial gills; branchiostegites each with few spinules on distal margin. Shield

( Fig. 1A ) longer than broad; dorsal surface with several tubercles laterally. Rostrum slender, elongate, reaching midlength of ocular acicles and considerably overreaching lateral projections, terminating acutely. Lateral projections triangular, each with terminal spinule.

Ocular peduncles subequal, left very slightly longer than right, approximately 0.8 length of shield, each with row of sparse tufts of setae on dorsal surface medially; corneal diameter 0.2 of peduncular length. Ocular acicles subtriangular, terminating in 2-4 small spines; separated by half of basal width of one acicle.

Antennular peduncles, when fully extended, reaching from proximal margin to midlength of cornea of left ocular peduncle; basal segment with small spine on lateral face of statocyst lobe.

Antennal peduncles reaching 0.6 length of ocular peduncles; fifth segment with few scattered setae; fourth segment with small dorsodistal spine and few setae; third segment with sparse setae laterally, ventrodistal margin terminating in acute spine; second segment with dorsolateral distal angle produced, terminating in small bifid or simple spine, dorsomesial distal angle with small spine, lateral and mesial margins with setae; first segment unarmed. Antennal acicle reaching to distal 0.2 or nearly to distal margin of fifth peduncular segment, terminating in prominent bifid spine; three to five spines on dorsal surface mesially, two or three spines on lateral margin, and scattered setae not concealing armature. Antennal flagellum 1.2-2.0 length of shield; articles each with one or two short setae proximally, slightly more numerous distally.

Chelipeds unequal, somewhat dissimilar;left larger. Left cheliped ( Fig. 2A, B ) with dactyl approximately 2 length of palm; dorsomesial margin often not distinctly delimited, distally flattened dorsal surface covered by large, sometimes bifid, closely-spaced, corneous-tipped acute spines or somewhat blunt tubercles, each accompanied by short setae; mesial face ( Fig. 2D ) with row, sometimes somewhat irregular, of small corneous-tipped spines medially, continued to tip, second row ventrally reaching 0.6 length of dactyl, each spine or tubercle usually accompanied by tuft of sparse, short setae; cutting edge with row of small calcareous teeth on proximal 0.3, corneous teeth on remainder, terminating in small corneous claw; no hiatus between dactyl and fixed finger. Palm usually with row of moderate to large spines on dorsomesial margin, convex dorsal surface with covering of closely-spaced, tuberculate spines or tubercles, each armed with bi- or trifid, acute or blunt, spinule, circumscribed by tuft of short, stiff setae ( Fig. 2C ), armature continued onto fixed finger and presenting scale-like appearance; dorsolateral margin not delimited, but rows of moderate to large, often corneous-tipped spines, becoming more prominent and acute distally on fixed finger, each spine accompanied by tuft of moderately long setae; mesial face with scattered tubercles; lateral face of palm and fixed finger with scattered spinulose tubercles, ventral surface with row of large spines, decreasing in size on fixed finger and sparse tufts of setae. Carpus with row of moderately prominent spines on dorsomesial margin, each spine accompanied by tuft of sparse setae, distal margin with row of small spines, extending onto lateral face; dorsolateral margin not delimited, dorsal and lateral surfaces with numerous acute or subacute spines accompanied by tufts of setae; mesial face with scattered spinulose tubercles. Merus with row of large spines on distal margin extending onto lateral and mesial faces, dorsal surface with one or two subdistal short, transverse rows of spines also extending onto lateral and mesial faces, remainder of dorsal margin with row of spines decreasing in size and becoming obsolete proximally; mesial face smooth, ventromesial margin with two irregular rows of small, spinulose tubercles or tuberculate spines and sparse tufts of setae; lateral face spinulose ventrally, ventrolateral margin with row of tuberculate spines and tufts of long setae, ventral surface with scattered tubercles and tufts of setae. Ischium with row of small tubercles on ventromesial margin.

Right cheliped ( Fig. 2E ) with dactyl approximately twice length of palm; dorsomesial margin with row of moderately small, corneous-tipped spines, decreasing in size distally; dorsal surface with numerous, quite small tubercles; cutting edge with row of very small calcareous teeth in proximal 0.2-0.3, corneous teeth distally, terminating in small corneous claw; mesial face ( Fig. 2F ) with row of small corneous-tipped spines near dorsal margin, few tubercles and shallow longitudinal sulcus below midline, each spine and tubercle accompanied by tuft of stiff moderately long setae. Palm with moderate to prominent, corneous-tipped spines on dorsomesial margin, dorsolateral margin not delimited, dorsal surface of palm and fixed finger with covering of closely-spaced tubercles or tuberculate spines, each often with bi- or trifid spinule and accompanied by tuft of short setae, giving overall surface scale-like impression; mesial face of palm with subdistal row of low tubercles and scattered small to large tubercles; ventral surface with row of spines, corneous-tipped proximally, simple and smaller distally; lateral surface of palm and fixed finger with scattered spinulose, sometimes corneoustipped spines, larger spine near ventral margin; cutting edge of fixed finger with row of small calcareous teeth, terminating in small corneous claw; no hiatus between dactyl and fixed finger. Carpus with row of usually prominent, corneous-tipped spines on dorsomesial margin, dorsodistal margin with row of spinules, extending onto lateral face; dorsolateral margin not delimited, dorsal surface and lateral face each with numerous small, tuberculate, sometimes corneous-tipped, spines; shallow longitudinal sulcus in midline; mesial face with few tuberculate spines; each spine accompanied by tuft of short setae. Merus with row of spines on distal margin extending onto lateral and mesial faces, dorsal surface with short, transverse, subdistal row of spines also extending onto lateral face, remainder of dorsal surface with row of spines decreasing in size and becoming obsolete proximally; ventromesial margin with row of tuberculate spines and sparse setae; lateral surface spinulose, ventrolateral margin with row of small spines and sparse short setae. Ischium with row of tubercles and tufts of setae on ventromesial margin.

Second and third pereopods ( Fig 3 ) differing somewhat in armature, right slightly larger. Dactyls approximately 1.6 longer than propodi; dorsal margins each with row of spinules, sometimes corneous-tipped (second), and long setae (second and third); ventral margins each with 16-29 corneous spines and sparse stiff setae; lateral faces of second pereopods with sparse tufts of long setae, third with sparse tufts of short to moderate setae; mesial face of left second pereopod flattened, with longitudinal sulcus and scattered small corneous spines, row of small corneous spines near ventral margin, mesial face of right with scattered tufts of setae and longitudinal sulcus; mesial face of left third pereopod also with row of spinules near ven- tral margin proximally, remainder of surface with scattered small spinules and small corneous spines, shallow longitudinal sulcus proximally, mesial face of right third broader but with similar armament. Propodi of second pereopods each with irregular row of moderately large, corneous-tipped spines on dorsal surface and tufts of long setae, third pereopods each with dorsal row of low protuberances, few additionally small spines and tufts of setae; ventral margins of second pereopods each with row of spinules and tufts of setae, third only with tufts of setae; lateral faces of second pereopods each with transverse rows of long setae near dorsal margin, shallow and narrow longitudinal sulcus accompanied by tufts of sparse short setae medially, and row of small tubercles near ventral margin; lateral faces of third similar but lacking row of small tubercles near each ventral margin; mesial faces of second pereopods each with transverse rows of tubercles and spines ventrally, several tubercles dorsally, each accompanied by tuft of setae denser on left; third pereopods each with row of spines (left) or spinules (right) near dorsal margin and irregular rows of small spines near ventral margin (left), fewer spines (right). Carpi each with shallow longitudinal sulcus and tufts of setae on lateral face; dorsal margins each with irregular double rows of spines and tufts of long setae more prominent on second. Meri of second pereopods each with ventral rows of small spines and tuft of long setae, dorsal margins each with low protuberances and long setae; third unarmed. Ischia unarmed but with long setae on ventral margins. Fourth pereopods ( Fig. 2G ) each with small preungual at base of claw; no dorsodistal spine on carpus.

Male first gonopods ( Fig. 1B, C ) each with single row of small hook-like corneous spines on distal margin of inferior lamella; external lobe slightly longer than inferior lamella, internal lobe short, with marginal setae. Second pleopods ( Fig. 1D ) with basal segment naked, distal segment with tuft of setae distally on endopod, appendix masculina with row of long marginal setae. Female first pleopods each with numerous moderately long setae on distal half of basal segment; distal segment with long marginal setae. Brood pouch ( Fig. 1E ) large, subquadrate, marginally scalloped and fringed with long, plumose setae. Eggs numerous, diameter 0.7-0.9 mm.

Telson ( Fig. 2H ) with moderately deep lateral incisions; median cleft small, shallow; posterior lobes markedly asymmetrical, terminal and lateral margins unarmed, each with row of long setae.

VARIATION

In the smaller specimens (male 3.6 mm, females 5.0 to 6.2 mm) of the series examined, the tubercles on the dactyls and palms of the chelipeds are simple rather than bi- or trifid; the dorsomesial margins of the dactyls of the left chelipeds are delimited by larger corneous-tipped spines. In larger specimens, particularly the males from the Gulf of Oman, the dorsomesial margins of the dactyls and the palms are armed with more flattened tubercles. Additionally, the mesial faces of the propodi of the left second pereopods in larger specimens are armed with irregular rows of spines or tubercles accompanied by tuft of moderately dense setae. The dissimilarity in the armature of the dorsomesial margins of the chelas and carpi of the left and right chelipeds is more prominently apparent in the smaller specimens.

AFFINITIES

Paguristes balanophilus was reported by Alcock (1905) to be closely allied with P.? ciliatus Heller, 1865 , P.calvus , and P. emerita (Linnaeus, 1767) (as the junior synonym, P. oculatus (Fabricius, 1775)) ; with Paguristes sp. from the Red Sea by Lewinsohn (1969); with P. runyanae Haig & Ball, 1988 , by Haig & Ball (1988); with P. kimberleyensis Morgan & Forest, 1991 and P. longirostris Dana, 1852 , by Morgan & Forest (1991); and with P. alcocki McLaughlin & Rahayu, 2005 , and P. lewinsohni McLaughlin & Rahayu, 2005 , by the latter authors. As pointed out by McLaughlin & Rahayu (2005), P. emerita and Heller’s (1865) P. ciliatus are immediately set apart by the spination of their respective telsons. In addition to the spination of the telson also reported for P. longirostris by McLaughlin (2002), the subequal chelipeds of both P. longirostris and P. runyanae will promptly differentiate these two species from the remainder. McLaughlin & Rahayu (2005) determined that Alcock’s (1905) P.? ciliatus was conspecific with P. alcocki and Lewinsohn’s (1969) Paguristes sp. was described as P. lewinsohni . Paguristes balanophilus , P. alcocki , and P. lewinsohni all appear to have a characteristic patch of colour on the distomesial and distolateral surfaces of each cheliped that is also present in P. longirostris , but absent in P. runyanae and P. kimberleyensis . Paguristes alcocki is most easily distinguished from both P. balanophilus and P. lewinsohni by the armature of the mesial faces of the dactyls of the chelipeds. In both latter species those surfaces have one or two principal rows of often corneous-tipped spines, whereas in P. alcocki the mesial faces of the dactyls are armed with several irregular rows of small simple or corneous-tipped spinules. Additionally, the ocular acicles of P. alcocki each terminate acutely or with a single spine, while those of P. lewinsohni and P. balanophilus terminate as a bi- to multifid spinose processes. Paguristes balanophilus and P. lewinsohni clearly are the most closely allied of any of the aforementioned species, and until colours in life are known, small specimens, because of their more acute armature, will probably be separated with difficulty. The mesial faces of the dactyls of the chelipeds ( Fig. 2D, F ), although somewhat variable, are provided with fewer spines and/or tubercles in P. balanophilus and the cutting edges of the dactyls each are provided with small calcareous teeth over only approximately 0.3 of the length. The chelas of P. balanophilus are dissimilar in size and shape, the left being much larger and subtriangular whereas the right is subrectangular. The armature of the dorsal surfaces of both chelipeds of P. balanophilus generally consists of coverings of closely-spaced tubercles or tuberculate spines, each usually muricated or studded with bi- or trifid spinules and accompanied by or circumscribed by short setae; this armature differs primarily in the size and prominence of the spines on the dorsomesial margins of the chelas and carpi. With increased animal size, these tubercles often become more flattened and squamiform. The ventral surfaces of the chelas each have a row of large spines. In contrast, the mesial faces of the dactyls of P. lewinsohni differ from left to right, with the right much more weakly armed; the calcareous teeth of both dactyls extend 0.6-0.8 of the entire lengths of the cutting edges. The chelas of P. lewinsohni , although distinctly differing in size, are both generally subtriangular when viewed dorsally; the dorsal surfaces each have a much less dense covering of individual corneous-tipped spines, those of the right chela typically somewhat larger; the spines on the dorsomesial margins of the chela and carpus of the right cheliped are appreciably larger than those of the left. The ventral surfaces of the chelas both lack a row of large spines. Although both species have the terminal telsonal margins unarmed, a distinct median cleft separates the two lobes in P. balanophilus , whereas the cleft is obsolete or entirely absent in P. lewinsohni .

REMARKS

According to Alcock (1905), a total of 19 specimens of P.balanophilus (IM 2644-59/10, 4239/10, 4248/10, 4310/10) were recorded from four Investigator stations in the Andaman Sea and off Bombay, whereas the five specimens of P. calvus (IM 4701-5/10) came from one station in the northern Bay of Bengal. It was apparently the practice of the Indian Museum at that time that only depths and catalog numbers were provided for the collection localities, while station numbers were mentioned separately in the Biological Collections list (see Anonymous 1914). The Andamans’ depth of 55 fathoms (102 m) corresponds with the data provided for station 239 in the list of stations of the Investigator from 1884 to 1913 ( Anonymous 1914). As previously indicated, it was this station number that accompanied the specimens given as gifts of P. balanophilus to the NHM and the MNHN. The NHM catalog number indicated 11 specimens; however, 20 specimens were present, but only 10 specimens had been removed from their shells. Our reexamination included all of the specimens, of which 19 were P. balanophilus , but one proved to be P. calvus . The label accompanying the three specimens presented to the Paris museum now includes only Investigator station 239, the notation of the gift, the MNHN catalog number, and the identifications of two specimens as P. balanophilus and one as P. calvus . Presumably, this subsequent identification was made by a member of the MNHN staff after 1903 and most probably was done by Bouvier.

In his original description, Alcock (1905: 33) said simply that the left cheliped of P. balanophilus was somewhat larger; however his illustration (ibid.: pl. 3, fig. 1) depicted a significantly larger left cheliped. Miyake and coauthors ( Miyake 1961, 1975, 1978a, b, 1982; Miyake et al. 1961; Miyake & Imafuku 1980) in several publications noted P. balanophilus as a member of the Japanese hermit crab fauna, but only in his monograph of the Anomura of Sagami Bay ( Miyake 1978b) did he provide a diagnosis of the species he had identified as P. balanophilus . His 1975, 1978 and 1982 (reprinted in 1991 and 1998) publications also provided colour illustrations. Matsuzawa (1977) similarly presented a photo of a species identified as P. balanophilus . It is not obvious from any of these reproductions whether the chelipeds are subequal or unequal; however in his diagnosis, Miyake (1978b: 40) clearly stated that the chelipeds of his species were subequal. As indicated in the redescription of P. balanophilus , the left cheliped is routinely appreciably larger than the right. Although we have not had the opportunity to locate any of Miyake’s material, we must conclude that the Japanese species heretofore reported as P. balanophilus is not Alcock’s (1905) taxon. Miyake (1978b: 41) described his species as being easily distinguished from other members of the genus by its particular colour pattern that included a dark red large circular patch in a violet field on both the inner and outer surfaces of the meri of the chelipeds. Unfortunately, there are several species that exhibit similar patches of colour, some with the colour restricted to the meri of the chelipeds, others with similar patches on the meri of the ambulatory legs as well. McLaughlin (2002) commented that the colour pattern of a species she identified from the Andaman Sea off Thailand as P. longirostris agreed better with the coloration described by Miyake (1978b) for P. balanophilus that it did with the colour of P. longirostris reported by Thomas (1989). However, in contrast to Miyake’s (1978b) unarmed telson, McLaughlin (2002) described the telsons of the Thai specimens as being armed with a few spines.At present, the true identity of Miyake and colleagues species is not known, but Dr T. Komai (pers. comm.) suspects it may prove to be P. gonagrus (H. Milne Edwards, 1836) .

Figures

FIG. 1. — Paguristes balanophilus Alcock, 1905: A-D, ♂ 6.5 mm; A, shield and cephalic appendages; B, male first pleopod, dorsal view, setae omitted; C, male first pleopod, mesial view, setae omitted; D, male second pleopod, dorsal view, setae partially omitted; E, ♀ 6.5 mm, brood pouch. Scale bars: 1 mm.

FIG. 2. — Paguristes balanophilus Alcock, 1905, ♂ 6.5 mm: A, left cheliped, lateral view, setae omitted; B, left cheliped, dorsal view, setae omitted;C, spines of cheliped; D, mesial face of dactyl of left cheliped, setae omitted; E, right cheliped, dorsolateral view,setae omitted; F, mesial face of dactyl of right cheliped, setae omitted; G, left fourth pereopod, lateral view, setae omitted; H, telson. Scale bars: 1 mm.

FIG. 3. — Paguristes balanophilus Alcock,1905,♂ 6.5 mm:A, B, left second pereopod;C, D, left third pereopod;E, right third pereopod; F, right second pereopod; A, C, lateral view; B, D-F, mesial view. Setae omitted. Scale bar: 2 mm.