Diogenes paracristimanus Wang and Dong, 1977

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 : 1236-1245

Diogenes paracristimanus Wang and Dong, 1977

( Figures 10–14 )

Diogenes paracristimanus Wang and Dong, 1977, p. 109 , figure 1 [type locality: north coast of Shandong Province, China]; Wang 1994, p. 568 (list); Wang 2008, p. 755 (list); McLaughlin et al. 2010, p. 21 (list).

Material examined

Dapeng Bay , near Hong Kong, Guandong Province, 22 ◦ 33.59 ′ N, 114 ◦ 25.09 ′ E, 18 m, mud, 15 April to 15 May 2007, trawl, 1 male (sl 6.8 mm; No. 1), CBM-ZC 10518 ; same data, 1 male (sl 7.4 mm; No. 2, figured), IOCAS-MBM 119738 ; Hailing Bay , Guandong Province, 21 ◦ 34.48 ′ N, 111 ◦ 43.36 ′ E, 10 m, 7 November 2007, 1 male (sl 4.9 mm; No. 3), IOCAS-MBM 119739 ; same data, 1 male (sl 5.3 mm; No. 4), CBM-ZC 10519 ; same data (sl 4.9 mm; No. 5), CBM-ZC 10520 .

Redescription

Shield ( Figure 10A ) 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 or spines near or at lateral angle; posterior margin truncate; dorsal surface with some transverse spinulose ridges laterally. Rostrum broadly rounded; lateral projections each with small, simple or bifid submarginal spine. Anterior part of branchiostegite with row of about 10 small spines on dorsal margin, anterior angle with one small spine; lateral surface with scattered small tubercles bearing tuft of setae ( Figure 10B ).

Ocular peduncles ( Figure 10A ) 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 or slightly concave inner margins, nearly straight or slightly convex anterolaterally, with about 10 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, slightly broadened basally, tapering to slender acute tip.

Antennular peduncles ( Figure 10A ) overreaching distal corneal margins by 0.5–0.6 length of ultimate segment and extending as far as antennal peduncles. Ultimate segment with some setae on dorsal surface and tufts distally on both ultimate and penultimate segments; basal segment with row of minute spinules on distolateral margin.

Antennal peduncles ( Figure 10A, B ) overreaching distal corneal margins by 0.8–0.9 length of fifth segment. Fifth segment with rows of moderately long to long stiff setae ventrolaterally; fourth and third segments 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 slightly falling short of distolateral margin of fourth segment, terminating in simple or bifid spine, bearing six or seven strong accessory spines on mesial margin, and with some tufts of short stiff setae on both lateral and mesial margins. Antennal flagellum ( Figure 10C ) more than twice shield length, articles with paired long, setulose setae and few additional short setae, forming cast net-like structure.

Third maxilliped ( Figure 10D ) moderately slender. Carpus unarmed on dorsodistal margin. Ischium-basis fused segment with five strong, corneous-tipped spines (three on ischium and two on basis) on mesial surface ( Figure 10E ). Exopod slightly overreaching distal margin of merus.

Left cheliped ( Figure 11A–F ) large but not particularly elongate in male, shape and armature rather variable; not particularly setose. Dactylus distinctly longer than palm; three irregular longitudinal rows of moderately small, spine-like tubercles on upper margin; outer surface very slightly concave, with scattered tiny tubercles or granules in lower part; cutting edge with two irregular rows of small tubercles; inner surface slightly elevated along midline with row of small tubercles, upper half nearly smooth, and lower half with scattered tiny tubercles. Palm slightly shorter than carpus; upper surface with three irregular rows of small, spine-like tubercles; outer surface with two rows of small tubercles, upper row extending from proximal to or beyond midlength of palm, middle row extending from proximal to at most midlength of palm, latter forming weak crest extending from carpal articulation, remaining outer surface with numerous microscopically small tubercles or granules (greater part apparently smooth to naked eye); proximal margin carinate; lower margin slightly sinuous in outer view (including fixed finger), with row of small rounded tubercles extending to base of fixed finger and continuous to proximal margin; inner surface with scattered, numerous tiny tubercles. Fixed finger slightly deflexed, not curved outward; outer surface elevated along midline, with scattered small granules, but without distinct row of tubercles or ridge; inner surface with scattered small tubercles proximally; cutting edge with row of rounded calcareous teeth in proximal half and two irregular rows of small tubercles in distal half. Carpus about as long as wide, with single row of moderately large spines on upper margin; outer surface convex, with scattered numerous small spines or spine-like tubercles, dorsodistal margin finely denticulate; mesial surface with row of small spines adjacent to upper margin and with scattered spinules; ventral surface also with scattered spine-like tubercles. Merus slightly longer than high; dorsal surface rounded, with tufts of stiff setae and short irregular transverse rows of small spines, distalmost row adjacent to distal margin longest, extending onto lateral and mesial surfaces; dorsodistal margin with row of spines; lateral surface with scattered tiny, simple or bifid tubercles or granules increasing in size ventrally, distolateral margin finely denticulate, ventrolateral margin with row of spines decreasing in size proximally; mesial surface nearly smooth except for dorsal part bearing tiny spines or spinules and longitudinal row of spines adjacent to ventromesial margin, distomesial margin with row of spines increasing in size ventrally and extending onto ventromesial margin; spines on ventromesial margin large; ventral surface with scattered minute spinules. Ischium with row of small tubercles on laterodistal margin ventrally and proximal margin; ventromesial margin with row of small tubercles.

Right cheliped ( Figure 12A–D ) moderately stout, setose. Dactylus fairly arched, about 2.6 times longer than palm; dorsal surface with two irregular longitudinal rows of small spines and accompanying tufts of stiff setae extending beyond midlength; mesial surface with median row of small tubercles and accompanying tufts of setae and prominent groove inferior to midline in proximal half; ventral surface with row of tiny tubercles and tufts of stiff setae on midline and with few small tubercles proximomesially; cutting edge with row of low, tiny tubercles. Palm about twice length of carpus; dorsal surface with tufts of stiff setae and four or five irregular longitudinal rows of small tubercles or spines (spines strongest around base of fixed finger), lateral rows extending onto fixed finger, dorsomesial face with numerous spines; mesial surface with some small tubercles dorsally, otherwise nearly smooth; ventral surface very slightly convex, with two rows of small spines laterally, extending onto fixed finger. Carpus with row of spines on dorsal margin and on dorsolateral surface, dorsodistal margin spinose; mesial surface with row of small spines or spine-like tubercles adjacent to dorsal margin and median row of small spinulose tubercles, distomesial margin spinulose. Merus with short transverse spinulose ridges or row of spines and tufts of long setae over entire length of dorsal margin, dorsodistal margin spinose; lateral surface with scattered tiny spinulose tubercles and tufts of short setae, ventrolateral margin only delimited in distal part, with two small spines or tubercles subdistally; mesial surface nearly smooth, with small spine-like tubercles adjacent to ventral margin, ventromesial margin with row of tiny to small spines; ventral surface with tiny spines and tufts of setae. Ischium with row of small tubercles on ventromesial margin; some small tubercles present on ventral surface.

Ambulatory legs ( Figures 13A, B , 14A, B ) similar, but third pair slightly longer than second pair. Dactyli about 1.5 times as long as propodi and 7.5–8.0 times longer than wide; dorsal margins unarmed (second and right third) or armed with row of minute spinules (left third) ( Figure 14C ), and each with row of moderately short stiff dense setae; lateral surfaces each with shallow median sulcus running over entire length; mesial surfaces each with short median sulcus and median row of setae proximally, otherwise nearly flat, and with dorsal and ventral rows 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 two rows of spinules and tufts of short stiff setae; lateral surface each with one row of small spinules and tufts of short stiff setae dorsally, otherwise nearly smooth; mesial surfaces each with row of small spinules dorsally (second) or unarmed (third), and with few tufts of short setae; ventral margins nearly smooth (second) or with row of small, low protuberances (third). Carpi each with row of small spines and tufts of setae on dorsal margin (spines smaller in third than in second; distalmost spine strongest); lateral surfaces each with median row of minute tubercles (second) or row of tiny, low protuberances (third); mesial surfaces each with one or more additional spine near base of dorsodistal spine (second) or unarmed (third). Meri with dorsal and ventral tufts of setae; dorsal margins each with row of spinules; lateral surfaces with minute spinulose tubercles dorsally and ventrally; mesial surfaces each with row of tufts of moderately long setae adjacent to dorsal margin; ventral surfaces each with two rows of spinules and row of tufts of setae. Ischia with rounded tubercles on ventral surfaces, dorsal margins bearing small spine (second) or unarmed (third).

Fourth pereopods chelate ( Figure 10F ). Dactyli reaching distal margins of propodi. Propodi each with distinctly produced dorsodistal margin sometimes bearing one small spine; rasp consisting of about 10 rows of corneous scales. Carpi each with or without dorsodistal spine.

Anterior lobe of sixth thoracic sternite (of third pereopods) ( Figure 10G ) distinctly bilobed, each lobe with two small spines laterally and anteriorly.

Telson ( Figure 10H ) with small median cleft, terminal margin oblique on left, nearly transverse on right, both with row of spinules or small spines (row of spinules extending onto left lateral margin), left with three prominent spines at lateral angle.

Coloration

Based on formalin preserved specimen: generally tan; non conspicuous markings on ocular peduncle, antennular peduncle and antenna; cornea black. Left chela with sparse brown dots on outer surface; carpus and merus with few brown dots. Ambulatory legs with trace of browning markings on middle parts of propodi and carpi.

Distribution

Known only from Chinese coast from Bohai to Zhejiang; intertidal to 30 m.

Remarks

Diogenes paracristimanus was originally described on the basis of three specimens, including two males and one female, from Shandong and Zhejiang Provinces ( Wang and Dong 1977). Wang (2008) added locality records of the species, but no morphological information was provided. In spite of our efforts, the type material could not be located. The present specimens from Guandong Province, located south of the known localities of this species, agree well with the original description except for the length of the antennular peduncle. In the original figure, the antennular peduncle exceeds beyond the antennal peduncle, but in the present two specimens it just reaches the latter. In the original description, the authors did not specifically mention about the extension of the antennular peduncle. It is most probable that this discrepancy is due to artistic inaccuracy.

The armature of the ambulatory legs seems to be ontogenetically variable in this species. In the three larger specimens (sl 5.3–7.4 mm), small spines on the ventral margin of the meri of the second pereopods and on the dorsal margins of the propodi of the third pereopods are conspicuous, but those spines are reduced to minute granules or spinules in the other two smaller specimens (sl 4.9, 4.9 mm).

Diogenes paracristimanus is here referred to the Diogenes 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 this species. Although Wang and Dong (1977) compared the present species only with D. bicristimanus Alcock, 1905 , we have found that it is also very similar to D. costatus Henderson, 1893 and D. lophochir Morgan, 1989 . The shared characters of these four species include: (1) left palm bearing distinct spinose or tuberculate crest extending from lower margin to proximo-lower margin near carpal articulation; and (2) propodi and carpi of second pereopods bearing rows of spinules on dorsal margins. Diogenes bicristimanus can be easily distinguished from D. paracristimanus by the sharp, stronger spines on or adjacent to the lower margin of the left palm, the presence of deep depressions on the outer surface of the left palm adjacent to the upper and lower margins, the smooth dorsal margins of the propodi of the second and third pereopods, and the reduced armature on the anterior lobe of the sixth thoracic sternite ( Alcock 1905; Tirmizi and Siddiqui 1982; Komai, unpublished data). In D. paracristimanus , tubercles on the lower part of the left palm are blunt; there are no marked depressions on the outer surface of the left palm; the propodi of the second and third pereopods are each armed with a dorsal row of small spines; the anterior lobe of the sixth thoracic sternite bears two pairs of spiniform tubercles. Diogenes costatus is separated from D. paracristimanus by the more pronounced crest on the left palm, extending from the lower proximal angle to at least the midlength, and the absence of a dorsal row of spinules on the propodi of the third pereopod ( Henderson 1893; Alcock 1905; Tirmizi and Siddiqui 1982; McLaughlin 2002b). In D. paracristimanus , the crest extending from the lower proximal angle of the left palm is weak, not extending to the midlength of the palm; and the propodi of the third pereopods are each armed with a dorsal row of spinules. Diogenes lophochir differs from D. paracristimanus in the possession of six or seven large spines on the dorsal margin of the anterior part of each branchiostegite, the prominent crest on the left palm extending from the lower proximal angle nearly to the base of the dactylus along the midline, the unarmed dorsal and mesial surfaces of the dactylus of the right cheliped, and the presence of a distinct longitudinal sulcus on the dactyli of the ambulatory legs ( Morgan 1989). In D. paracristimanus , the branchiostegite is armed with a row of about 10 small spines on the anterior part of the dorsal margin; the dactylus of the right cheliped is armed with longitudinal rows of small spines on the dorsal surface and a longitudinal row of small tubercles on the mesial surface; the dactyli of the ambulatory legs are devoid of distinct longitudinal sulci.

As mentioned above, Diogenes paracristimanus is also similar to D. deflectomanus , which has an overlapping distribution in Chinese waters (for comparison, see the account of D. deflectomanus ).

Figures

Figure 10. Diogenes paracristimanus Wang and Dong, 1977, male (sl 7.4 mm), IOCAS-MBM 119738: (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; (H) telson, dorsal view; (I) same, details of armature of left terminal to posterolateral margins, obliquely dorsal view. Scale bars: 2 mm for A–D; 1 mm for E–I.

Figure 11. Diogenes paracristimanus Wang and Dong, 1977: (A, B–F), male (sl 7.4 mm), IOCAS-MBM 119738; (B) male (sl 5.3 mm), CBM-ZC 10519. Left cheliped: (A, B), chela, outer view; (C) dactylus and fixed finger, inner view; (D) carpus, outer view; (E) carpus and merus, mesial view; (F) merus, lateral view. Scale bars: 5 mm for A, C–F; 2 mm for B.

Figure 12. Diogenes paracristimanus Wang and Dong, 1977, male (sl 7.4 mm), IOCAS-MBM 119738. Right cheliped: (A) chela, dorsal view (setae omitted); (B) entire cheliped, mesial view; (C) same, lateral view (setae omitted); (D) carpus, dorsal view (setae omitted). Scale bar: 2 mm.

Figure 13. Diogenes paracristimanus Wang and Dong, 1977, male (sl 7.4 mm), IOCAS-MBM 119738:(A) right second pereopod, lateral view; (B) same, mesial view (only mesial setae shown). Scale bar: 5 mm.

Figure 14. Diogenes paracristimanus Wang and Dong, 1977, male (sl 7.4 mm), IOCAS-MBM 119738: (A) left third pereopod, lateral view; (B) same, mesial view (only mesial setae shown): (C) same, dactylus, lateral view, showing armature on dorsal margin. Scale bars: 5 mm for A, B; 2 mm for C.