Diogenes deflectomanus Wang and Tung, 1980

Komai, Tomoyuki, Liang, Jingzhen & Yang, Tingbao, 2012, Records of four species of the shallow water hermit crab genus Diogenes (Crustacea: Decapoda: Anomura: Diogenidae) from southern China, with description of a new species, Journal of Natural History 46 (19 - 20), pp. 1219-1248 : 1228-1236

Diogenes deflectomanus Wang and Tung, 1980

( Figures 6–9 )

Diogenes deflectomanus Wang and Tung, 1980, p. 35 , figure 1 [type locality: Yangan, Zhejiang, China, 22 m]; Wang 1994, p. 568 (list); Wang 2008, p. 755 (list); McLaughlin et al. 2010, p. 21 (list).

Diogenes defrectomanus (sic): Rahayu 1996, p. 389.

Material examined

Leizhou Bay , Guandong Province, 20 ◦ 10.20 ′ N, 110 ◦ 56.40 ′ E, 10 m, 15 April to 15 May 2007, trawl, 1 male (sl 4.1 mm; No. 8, figured), IOCAS-MBM 119737 ; Hailing Bay , Guandong Province, 21 ◦ 34.48 ′ N, 111 ◦ 43.36 ′ E, 10 m, July to August 2007, trawl, 1 male (sl 4.3 mm; No. 9), CBM-ZC 10522 .

Redescription

Shield ( Figure 6A ) slightly longer than broad, almost subquadrate; anterior margin between rostrum and lateral projections slightly concave, with four to six tiny tubercles near each base of lateral projection; anterolateral margins sloping, with few tiny tubercles near lateral angle; posterior margin truncate; dorsal surface with several transverse spinulose ridges laterally. Rostrum broadly rounded; lateral projections each with moderately strong submarginal spine. Anterior part of branchiostegite with nine to 10 small spines on dorsal margin, anterior angle with one small spine; lateral surface with scattered tufts of short to moderately long setae ( Figure 6B ).

Ocular peduncles ( Figure 6A ) about 0.6 times as long as shield, moderately stout; cornea not dilated, corneal width about 0.3 of peduncular length; ocular acicles with straight inner margins, nearly straight anterolaterally, four or five small spines decreasing in size laterally, not extending to entire length of terminal margin. Intercalary rostriform process reaching nearly to distal end of ocular acicles, broad basally, tapering to slender acute tip.

Antennular peduncles ( Figure 6A ) overreaching distal corneal margins by about 0.8 length of ultimate segment and reaching or slightly overreaching antennal peduncles. Ultimate segment with some setae on dorsal surface and tufts distally on both ultimate and penultimate segments; basal segment unarmed.

Antennal peduncles ( Figure 6A, B ) overreaching distal corneal margins by about 0.7 of fifth segment. Fifth segment with rows of numerous moderately long to long stiff setae ventrolaterally; fourth segment with few scattered tufts of short setae, unarmed; second segment with strong spine at dorsolateral distal angle and small but prominent spine at dorsomesial distal angle, ventrodistal margin with row of spinules; first segment with row of spinules on distal margin laterally. Antennal acicle reaching to distolateral margin of fourth segment of peduncle, terminating in simple or bifid spine, bearing five or six strong accessory spines on mesial margin, and with some tufts of short stiff setae on both lateral and mesial margins. Antennal flagellum ( Figure 6C ) more than twice of shield length, articles with paired long, setulose setae and few additional short setae, forming cast net-like structure.

Third maxilliped ( Figure 6D ) moderately slender. Carpus with minute spine on dorsodistal margin. Ischium-basis fused segment with three moderately strong, corneous-tipped spines (two on ischium and one on basis) on mesial surface ( Figure 6E ). Exopod overreaching distal margin of carpus.

Left cheliped ( Figures 7A–E ; 8A–C ) elongate. Dactylus 1.1–1.2 times longer than palm; double row of moderately small to moderately large tubercles on upper margin (those tubercles sometimes spine-like); outer surface weakly elevated along midline, with short row of tubercles proximally adjacent to upper margin and scattered small tubercles proximally; cutting edge with single row of small rounded calcareous teeth; inner surface nearly smooth with short row of small tubercles in midline proximally. Palm distinctly longer than wide, and shorter than carpus; outer surface with two rows of tubercles, upper row extending from proximal to or beyond midlength of palm, middle row extending from proximal to at most midlength of palm, remaining outer surface with numerous small blunt tubercles; proximo-lower margin not markedly carinate or crested; lower margin nearly straight in outer view, with row of low, rounded tubercles; inner surface with numerous low, sometimes squami-form tubercles increasing in size ventrally. Fixed finger scarcely or slightly deflexed, somewhat curved outward; outer surface with row of tubercles on elevated midline, otherwise nearly smooth; inner surface nearly smooth; cutting edge with row of rounded calcareous teeth, strongest at proximal 0.3 and subterminal. Carpus about twice longer than wide, with double row of moderately small spines on upper margin; outer surface convex, with numerous small, simple to multifid tubercles, dorsodistal margin with row of spinules; lateral surface with numerous low, rounded tubercles (simple to multifid); ventral surface with small tubercles. Merus slightly longer than high; dorsal surface rounded, with tufts of stiff setae and short transverse rows of small spinules or spinulose tubercles, distalmost row adjacent to distal margin longest, extending onto lateral and mesial faces; lateral surface with scattered small, simple to multifid tubercles or granules increasing in size ventrally, ventrolateral margin with row of small rounded tubercles; mesial surface with distally spinulose tubercles dorsally and ventrally (dorsal tubercles with tufts of short setae), ventromesial margin weakly tuberculate; ventral surface with small, low tubercles and tufts of short setae. Ischium with row of small granules on laterodistal margin ventrally and proximal margin; ventromesial margin tuberculate.

Right cheliped ( Figure 8D–G ) moderately stout. Dactylus strongly curved, about 2.6 times longer than palm; dorsal margin with short row of small spines proximal on midline and one additional short row of spines just lateral to median row; two rows of tufts of stiff setae extending entire length on dorsal surface; mesial surface with one short row of moderately small spines on midline proximally and single row of tufts of setae adjacent to ventral margin; cutting edge without conspicuous teeth. Palm about 0.6 times as long as carpus; dorsal surface with tufts of long stiff setae and four or five irregular longitudinal rows of small tubercles or spines (becoming larger and sharper distally), lateral rows extending onto fixed finger, dorsomesial margin with row of moderately small spines, dorsolateral surface sloping ventrally; mesial surface with some small low protuberances; ventral surface very slightly convex, with single row of small spines laterally, extending onto fixed finger. Carpus with row of spines on dorsal margin and row of tubercles on dorsolateral surface, dorsodistal margin with row of tiny spinulose tubercles; mesial surface with row of low, distally spinulose protuberances adjacent to dorsal margin, otherwise with few very low protuberances, distomesial margin spinulose. Merus with short transverse spinulose ridges in distal half and tufts of long setae over entire length of dorsal margin, dorsodistal margin spinose; lateral surface with scattered tiny tubercles or low protuberances and tufts of short setae, ventrolateral margin with two small spines or tubercles subdistally; mesial surface nearly smooth, with small tubercles adjacent to ventral margin, ventromesial margin with row of tiny to small tubercles; ventral surface with small, low tubercles and tufts of setae. Ischium with row of spinulose tubercles on ventromesial margin.

Ambulatory legs ( Figure 9A–D ) similar, but third pair slightly longer than second pair. Dactyli 1.2–1.3 times as long as propodi and 8.2–8.9 times longer than wide; dorsal margins unarmed, each with row of moderately short stiff dense setae; lateral surfaces each with distinct median sulcus over entire length; mesial surfaces each with short median sulcus and median row of setae proximally, otherwise nearly flat, and with dorsal and ventral row of long stiff dense setae; ventral surfaces each with row of short sparse setae. Propodi slightly curved, distinctly longer than carpi; dorsal surfaces each with irregular two rows of spinules and two rows of tufts of stiff setae (second) or nearly smooth but with two irregular rows of stiff setae (third); lateral surfaces each with row of tufts of setae adjacent to dorsal margin and sparse row of tufts of very short setae ventrally; mesial surfaces each with row of tufts of moderately short setae on either side of midline; ventral surfaces with sparse setae. Carpi each with two rows of small spinules and tufts of setae on dorsal margin (spines sometimes fairly reduced on third); lateral surfaces each with row of tufts of short setae dorsally; mesial surfaces each with longitudinal row of tufts of setae dorsal to midline. Meri with dorsal and ventral tufts of setae; dorsal margins each with row of spinules (second) or row of low protuberances (third); lateral surfaces with row of tufts of short setae adjacent to ventral margin; ventral margins each without conspicuous armature. Ischia unarmed, with tufts of moderately long setae.

Fourth pereopods chelate ( Figure 6F ). Propodi each with dorsodistal margin not particularly produced, unarmed; rasp consisting of five or six rows of corneous scales. Carpi without dorsodistal spine.

Anterior lobe of sixth thoracic sternite (of third pereopods) ( Figure 6G ) distinctly bilobed, each lobule with spinule at anterolateral angle.

Telson ( Figure 6H ) with small median cleft, terminal margins of both lobes nearly transverse, with long, curved spines interspersed with minute denticles ( Figure 6I ), extending onto lateral margin of left only.

Coloration

Based on formalin preserved specimen: generally tan; non conspicuous markings on ocular peduncle, antennular peduncle and antenna; cornea black. Left cheliped mottled with brown. Ambulatory legs with brownish markings on middle parts of propodi and meri; carpi with longitudinal brown spots on lateral surfaces.

Distribution

Recorded from the Chinese coast from Bohai to Hainan Island ; intertidal to 30 m ( Wang 2008) .

Remarks

Diogenes deflectomanus was described on the basis of nine specimens from Zhejiang and Guandong Provinces ( Wang and Tung 1980). In spite of our efforts, the type specimens could not be located. The present topotypic specimens from the Guandong Province generally agree with the short original description and illustrations except for the length of the antennular peduncle. In the figure given by Wang and Tung (1980), the antennular peduncle exceeds beyond the antennal peduncle, whereas in the present specimens, it just reaches or slightly overreaches the latter. Wang and Tung (1980) do not specifically mention about the extension of the antennular peduncle, and it is likely that this discrepancy is due to an artistic error. We identify our specimens with D. deflectomanus with little hesitation.

The shape and armature of the left cheliped are substantially variable in this species, as figured ( Figures 7A , 8A ). Similar variation in the male left cheliped is seen in other congeneric species showing a tendency of elongation of that cheliped (e.g. Asakura 1987; Rahayu and Forest 1995).

Diogenes deflectomanus is here referred to the D. edwardsii species group by the characters of the intercalary rostriform process and the antenna ( Asakura and Tachikawa 2010), though Asakura and Tachikawa (2010) did not mention about this species. Wang and Tung (1980) compared Diogenes deflectomanus with D. bicristimanus Alcock, 1905 and D. paracristimanus . In fact, these three species share a diagnostic character, the possession of dorsal row(s) of spinules on the propodi of the second pereopods. Nevertheless, as mentioned by Wang and Tung (1980), D. deflectomanus is distinguished from the latter two species by the poorly defined proximo-lower crest on the left chela in males. As mentioned under the account of D. paracristimanus , the left chela of D. bicristimanus exhibits characteristic distinct sculpture and armature ( Alcock 1905; Tirmizi and Siddiqui 1982). The relatively long antennal acicle (reaching the distolateral margin of the fourth segment of the antennal peduncle versus falling short of it), the lack of conspicuous spines on the ventrolateral and ventromesial margins of the merus of the left cheliped, and the dorsally unarmed propodi of the third pereopods further distinguish D. deflectomanus from D. paracristimanus . Furthermore, the left cheliped of D. deflectomanus exhibits a tendency of elongation, which is not seen in D. paracristimanus . The merus of the second pereopod is unarmed on the ventral margin in D. deflectomanus , whereas it is armed with a row of small spines in D. paracristimanus .

Diogenes deflectomanus is also similar to D. avarus Heller, 1865 and D. nitidimanus Terao, 1913 . These three species have the propodi of the second pereopods armed with row(s) of spinules on the dorsal surfaces; and the lower-proximal crest of the left chela is poorly delimited at least in males. It further shares with D. avarus the anterior lobe of the sixth thoracic sternite armed with a pair of small spines. The outer surface of the left palm distinctly elevated into a blunt ridge along the midline and the usually armed dorsal margins of the propodi of the third pereopods readily distinguish Diogenes avarus from D. deflectomanus (cf. Rahayu 1996; McLaughlin and Dworschak 2001; McLaughlin 2002b). Diogenes nitidimanus differs from D. deflectomanu s in the relatively shorter antennular peduncle overreaching the distal corneal margins by only half of the ultimate segment, the presence of a distinct longitudinal sulcus on the inner face of the dactylus of the left chela, the possession of a row of conspicuous spines on the ventromesial margin of the merus of the left cheliped, the presence of a row of small, blunt calcareous teeth on the cutting edge of the dactylus of the right chela, and the unarmed anterior lobe of the sixth thoracic sternite ( Korn et al. 2008). In D. deflectomanus , the antennular peduncle overreaches the distal corneal margins by 0.8 or more length of the ultimate segment; the dactylus of the left cheliped is devoid of a median sulcus on the inner surface; the ventromesial margin of the merus of the left cheliped is devoid of conspicuous spines; the dactylus of the right chela is almost unarmed; and the anterior lobe of the sixth thoracic sternite is armed with a pair of small spines.

Figures

Figure 6. Diogenes deflectomanus Wang and Tung, 1980, male (sl 4.1 mm), IOCAS-MBM- 119737: (A) shield and cephalic appendages, dorsal view (antennal flagella omitted; setae on left side omitted); (B) anterior part of branchiostegite and antennal peduncle of left side, lateral view; (C) right antennal flagellum, dorsal view; (D) left third maxilliped, lateral view (setae omitted); (E) same, basis-ischium fused segment, dorsal view; (F) chela and distal part of carpus of left fourth pereopod, lateral view (setae omitted); (G) anterior lobe of sixth thoracic sternite, ventral view (setae omitted); (H) telson, dorsal view; (I) same, details of armature of terminal margins, posterior view. Scale bars: 1 mm for A–D, F, H; 0.5 mm for E, G, I.

Figure 7. Diogenes deflectomanus Wang and Tung, 1980, male (sl 4.1 mm), IOCAS-MBM 119737. Left cheliped: (A) chela, outer view; (B) same, inner view; (C) carpus, outer view; (D) carpus and merus, mesial view; (E) same, lateral view. Scale bar: 2 mm.

Figure 8. Diogenes deflectomanus Wang and Tung, 1980. (A–C), male (sl 4.3 mm), CBM-ZC 10522; (D–G), male (sl 4.1 mm), IOCAS-MBM 119737. (A) left chela, outer view (setae and granules omitted); (B) same, lower view (only outline shown); (C) carpus of left cheliped, outer view (setae and surface armature omitted); (D) right chela, dorsal view (setae omitted); (E) right cheliped, mesial view; (F) same, lateral view (setae omitted); (G) carpus, dorsal view (setae omitted). Scale bars 2 mm.

Figure 9. Diogenes deflectomanus Wang and Tung, 1980, male (sl 4.1 mm), IOCAS-MBM 119737:(A) right second pereopod, lateral view; (B) same, mesial view (only mesial setae shown); (C) right third pereopod, lateral view; (D) same, mesial view (only mesial setae shown). Scale bar: 2 mm.