Paguristes calvus 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 : 875-879

Paguristes calvus Alcock, 1905

( Figs 4 ; 5 )

Paguristes calvus Alcock, 1905: 35 , pl. 1, fig. 4. — Balss 1915: 9; 1929: 25. — Ramadan 1936: 4 (list). — Gordan 1956: 321 (list). — Lewinsohn 1969: 13. — Türkay 1986: 132.

TYPE MATERIAL. — Northern Bay of Bengal. Investigator , stn not listed, 120 m, 5 syntypes ( IM 4701-5/10) not seen.

OTHER MATERIAL EXAMINED. — Andaman Sea. Investigator , stn 239, 11°49.5’N, 92°55.0’E, 102 m, 14. IV.1898, 1 ♀ 5.6 mm ( NHM 1903.4.6.181-191) ; 1 ♀ c. 6.0 mm, shield damaged ( MNHN Pg 1533) .

Red Sea. Pola Expedition, stn 179, 26°34’N, 34°14’E, 490 m, 28.II.1898, 1 ♀ 5.7 mm (NHMW 7492).

TYPE LOCALITY. — Northern Bay of Bengal ; 120 m.

DISTRIBUTION. — Northern Bay of Bengal; Andaman and Red seas.

DESCRIPTION

Thirteen pairs of quadriserial gills; branchiostegites each with few spinules on distal margin and dorsal margin distally. Shield ( Fig. 4A ) longer than broad; dorsal surface with few tubercles laterally. Rostrum slender, elongate, reaching distal 0.3 of ocular acicles and considerably overreaching lateral projections, terminating acutely. Lateral projections triangular, each with tiny terminal spinule.

Ocular peduncles shorter than shield length, each with row of sparse tufts of setae on dorsal surface; corneal diameter 0.3 of peduncular length. Ocular acicles subtriangular, terminating acutely or in simple spine; separated by considerably more than basal width of one acicle.

Antennular peduncles, when fully extended, slightly longer than ocular peduncles; basal segment with small spine on lateral face of statocyst lobe.

Antennal peduncles reaching bases of corneas; fifth segment with few scattered setae; fourth segment with small dorsodistal spine and few setae; third segment with sparse setae laterally, ventrodistal margin with one or two acute spines; second segment with dorsolateral distal angle produced, terminating in simple or small to moderately large bifid spine, dorsomesial distal angle with small spine, lateral and mesial margins with setae; first segment unarmed. Antennal acicle reaching distal 0.2 to nearly distal margin of fifth peduncular segment, terminating in prominent bifid spine; two spines on lateral margin, four or five spines on mesial margin, with scattered setae not concealing armature. Antennal flagellum considerably longer than shield; articles each with one or two short setae proximally, slightly more numerous setae distally.

Chelipeds unequal, dissimilar; left larger.Left cheliped ( Fig. 4B )with dactyl approximately 1.7 length of palm; dorsomesial margin delimited by row of large corneous-tipped spines, dorsal surface with irregular row of moderately small corneous-tipped spines and row of tubercles laterad of midline, near cutting edge, few setae on dorsal surface; mesial face ( Fig. 4C ) with row of small corneous-tipped spines medially, several tubercles and small corneous-tipped spines below midline accompanied by sparse setae; cutting edge with row of small calcareous teeth, terminating in small corneous claw; without hiatus between dactyl and fixed finger. Palm with row of moderate to large spines on dorsomesial margin, convex dorsal surface with covering of prominent corneous-tipped spines and sparse tufts of setae, dorsolateral margin weakly delimited by row of large and small corneoustipped spines, becoming more prominent and acute distally on fixed finger; mesial face with scattered small 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 accompanied by tufts of sparse setae, distal margin with row of small spines extending onto lateral face; dorsolateral margin not delimited, dorsal and lateral surfaces with numerous spines, each spine with tuft of sparse setae; mesial face with subdistal row of small spinulose tubercles and two rows of tubercles dorsally. Merus with row of large spines on distal margin extending onto lateral and mesial faces, dorsal surface with subdistal short, transverse row of spines also extending onto lateral and mesial faces, remainder of dorsal margin with row of spines decreasing in size proximally and becoming obsolete; mesial face spinulose, ventromesial margin with row of small, spinulose tubercles or tuberculate spines and sparse tufts of setae; lateral face spinulose near ventral margin, ventrolateral margin with row of small, tuberculate spines and tufts of long setae. Ischium with row of small tubercles on ventromesial margin.

Right cheliped ( Fig.4D ) with dactyl approximately 1.6 length of palm; dorsomesial margin with row of moderately small, corneous-tipped spines, decreasing in size distally, each spine accompanied by tuft of sparse setae; dorsal surface with numerous quite small tubercles; cutting edge with row of very small calcareous teeth in proximal 0.2, corneous teeth distally, terminating in small corneous claw; mesial face ( Fig. 4E ) with row of small corneous-tipped spines dorsally, second irregular row and few tubercles ventrally. Palm with prominent, corneous-tipped spines on dorsomesial margin, dorsolateral margin not delimited, dorsal surface of palm and fixed finger with irregular rows of moderately large, sometimes corneous-tipped spines, each accompanied by sparse short setae; cutting edge of fixed finger with row of small calcareous teeth, terminating in small corneous claw; mesial face of palm with subdistal row of low tubercles and scattered smaller and larger tubercles; ventral surface with row of spines, corneous-tipped proximally, smaller spines distally; lateral surface of palm and fixed finger with scattered, sometimes corneous-tipped, spines, largest near ventral margin. Carpus with row of prominent corneous-tipped spines on dorsomesial margin, dorsodistal margin with row of spinules, extending onto lateral face; dorsolateral margin not delimited, dorsal and lateral surfaces each with numerous small, tuberculate, sometimes corneous-tipped spines; mesial face with few tuberculate spines. Merus with row of spines on distal margin extending onto lateral and mesial faces, dorsal surface with short, transverse row of subdistal spines also extending onto lateral face, remainder of dorsal surface with row of spines decreasing in size proximally and becoming obsolete; 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. 5 ) differing somewhat in armature.Dactyls about twice length of propodi; dorsal margins each with row of spinules, sometimes corneous-tipped (second), and long setae (second and third); ventral margins each with 29-40 corneous spines; lateral faces each with sparse tufts of setae and weak longitudinal sulcus proximally; mesial face of second left pereopod slightly flattened, with row of small corneous spines near ventral margin and scattered small corneous spines, right with row of stiff setae near ventral margin, sparse corneous spines near dorsal margin, and weak longitudinal sulcus proximally; mesial faces of third pereopods each with shallow longitudinal sulcus proximally, row of setae near ventral margin and row of tufts of sparse setae medially. Propodi of second pereopods each with irregular row of moderately small spines and tufts of long setae on dorsal surface; ventral margins each with row of spinules and tufts of setae, mesial faces with numerous scattered tubercles (left) or sparse tubercles and corneous-tipped spinules (right). Propodi of third pereopods each with dorsal row of low protuberances and tufts of setae on dorsal surface; ventral margins with tufts of setae and mesial faces each with few tiny tubercles. Carpi each with shallow longitudinal sulcus on lateral face; second pereopods each with dorsal row of prominent spines and tufts of long setae, third with prominent dorsodistal spine and small spines or protuberances and tufts of setae on remainder of dorsal surface. Meri of second pereopods each with ventral rows of small spines and tuft of long setae, third unarmed. Ischia of second with few spinules on ventral margin, third unarmed. Fourth pereopods ( Fig. 4F ) each with small preungual at base of claw; no dorsodistal spine on carpus.

Female first pleopods each with numerous moderately long setae on distal half of basal segment; distal segment with long marginal setae. Brood pouch ( Fig. 4G ) large, subtriangular, margin slightly scalloped, fringed with long, plumose setae.

Telson ( Fig. 4H ) with moderately deep lateral incisions; median cleft small, shallow; posterior lobes markedly asymmetrical, terminal and lateral margins unarmed, each with row of long setae.

AFFINITIES

As noted by Alcock (1905), P. calvus is morphologically quite similar to P. balanophilus . Alcock distinguished P. calvus by its shorter, stouter ocular peduncles, longer antennal flagella and less setation. However, as demonstrated by McLaughlin (2004), ocular peduncular length and stoutness are frequently growth-related variables.Antennal flagellar length and setal densities are subject to appreciable intraspecific variation. With the few specimens of P. calvus that have ever been reported, it is not possible to assess variation in this species. However, there are characters that clearly are not subject to as much variation that can be used to differentiate between the two taxa. The number of spines on ventral margins of dactyls of the second and third pereopods tends to be greater in P. calvus , 29-40 rather than the 16-29 seen in P. balanophilus . The three specimens of P. calvus that we have been able to examine all have simple ocular acicles, although the left acicle of the Red Sea specimen is damaged. The acicles of P.balanophilus are bi- to multifid. The mesial faces of dactyl and propodus of the left second pereopod of P.calvus , while slightly flattened, are not as distinctively so as is seen in P. balanophilus ; the surfaces lack the longitudinal sulci; and the number and arrangement of spines are different. Although in smaller specimens of P. balanophilus the spines and tubercles on the dorsal surfaces of the chelipeds have not yet taken on squamiform appearances, the encircling short setae that accompany them are present. These arcs of setae are not seen in P. calvus where only 1-3 longer setae may occasionally accompany individual spines.

REMARKS

For the identification of P. calvus from the Valdivia Expedition, Türkay (1986) compared his four males and one female with the female identified by Balss (1915). Although Türkay (1986) gave no information on the morphology of his specimens, he did confirm the species’ occurrence in the Red Sea and called attention to new depth record for the taxon. Balss’ (1915) specimen had been collected at a depth of 490 m; the Valdivia specimens came from depths between 748 and 804 m. Alcock’s (1905) specimens were from the much shallower depth of 120 m.

Figures

FIG. 4. — Paguristes calvus Alcock, 1905, ♀ 5.6 mm: A, shield and cephalic appendages, setae omitted; B, left cheliped, dorsal view, setae omitted; C, mesial face of dactyl of left cheliped, setae omitted; D, right cheliped, dorsal view, setae omitted; E, mesial face of dactyl of right cheliped, setae partially omitted; F, left fourth pereopod, lateral view, setae omitted; G, brood pouch, setae partially omitted; H, telson. Scale bars: 1 mm.

FIG. 5. — Paguristes calvus Alcock,1905 ♀, 5.6 mm:A, B, left second pereopod,setae omitted;C, D, left third pereopod,setae omitted; E, right second pereopod, setae partially omitted; A, C, lateral view; B, D, E, mesial view. Scale bar: 1 mm.