Diogenes chhapgari Trivedi, Osawa & Vachhrajani, 2016, n. sp.
Creators: name: Trivedi, Jigneshkumar N.
name: Osawa, Masayuki
name: Vachhrajani, Kauresh D.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Diogenidae
Diogenes
Diogenes chhapgari

description: Diogenes chhapgari n. sp.
(Figs1–4)
Material examined. Holotype. ZL-AR-AN-09, ♂ (SL 3.61 mm, SW 3.70 mm), Koliyak (21°36'02"N, 72°17'23"E), Gulf of Khambhat, Gujarat, India, sand and mud, 29 January 2014 (coll. Jignesh Trivedi and Kauresh Vachhrajani).
Paratypes. ZL-AR-AN-16, 11 males (SL 3.05–3.50 mm, SW 3.13–3.69 mm), 4 females (2 ovigerous; SL 2.23– 2.72 mm, SW 2.49–2.92 mm), Koliyak (21°36'02"N, 72°17'23"E), Gulf of Khambhat, Gujarat, India, sand and mud, 26 October 2015 (coll. Jignesh Trivedi and Gunjan Soni).
Non-types. ZL-AR-AN-17, 10 males (SL 2.17–3.07 mm, SW 2.28–3.25 mm), 5 females (3 ovigerous; SL 1.91–2.51 mm, SW 2.10–2.61 mm), Dandi (20°53'10"N, 72°47'47"E), Gulf of Khambhat, Gujarat, India, sand and mud, 3 July 2014 (coll. Jignesh Trivedi, Gunjan Soni, and Dhruva Trivedi)..
Description. Shield (Fig. 1 A) slightly broader than long, suboctagonal; anterior margin between rostrum and lateral projection slightly concave; lateral projections with 2 tubercles laterally, terminally each with small submarginal spinule; anterolateral margin sloping; posterior margin roundly truncate; dorsal surface laterally with setae-bearing, short transverse ridges, setose tubercles lateral to midline. Rostrum (Fig. 1 A) obtuse. Anterior part of branchiostegite (Fig. 1 E) with row of about 10 small spines on dorsal margin, anterior margin rounded.
Ocular peduncles (Fig. 1 A) equal in length, about 0.7 times as long as shield, moderately stout, not inflated basally; cornea not dilated, corneal width 0.3 of peduncular length, subequal to basal width of peduncle; ocular acicles each with slightly concave mesial margin, anterolateral margin nearly straight or slightly convex, bearing 5–7 spinules decreasing in size laterally. Intercalary rostral process not reaching distal end of ocular acicles, slightly broadened medially, anteriorly ending in slender acute tip.
Antennular peduncle (Fig. 1 A) overreaching distal corneal margin by 0.4–0.5 length of ultimate segment, extending slightly beyond distal margin of antennal peduncle. Ultimate segment 4.4 times longer than distal width, slightly longer than penultimate segment, with scattered setae on dorsal surface. Penultimate segment with tuft of setae on dorsodistal margin. Basal segment with tuft of setae on dorsodistal mesial angle and on median part of mesial margin.
Antennal peduncle (Fig. 1 A) overreaching distal corneal margin by 0.5–0.6 length of fifth segment. Fifth segment with row of long stiff setae on ventral surface. Fourth and third segments unarmed. Second segment with strong spine on dorsolateral distal angle and small but prominent spine on dorsomesial distal angle. First segment with small but prominent spine dorsolaterally on distal margin. Antennal acicle reaching slightly beyond distal margin of fourth peduncular segment, bearing simple or bifid terminal spine, armed with 4 or 5 spines on mesial margin and some tufts of setae on both mesial and lateral margins. Antennal flagellum (Fig. 1 F) more than twice length of shield, articles each with paired long setae on ventral margin.
Third maxillipeds (Fig. 1 B) moderately slender. Merus with small spine at dorsolateral distal angle. Ischiumbasis (Fig. 1 C) fused segment with 3 strong, corneous–tipped spines on ventral margin. Coxa unarmed. Exopod slightly overreaching distal margin of merus.
Left cheliped much larger than right. Chela (Figs. 2 A, B) with narrow hiatus between dactylus and fixed finger. Dactylus about 1.1 times longer than palm, terminating in small calcareous claw; upper margin with double row of small tubercles or spines (becoming single row on distal half); outer surface covered with scattered small tubercles or spines, and with single row of tubercles or spines running parallel to upper margin and merging row of upper margin proximal to midlength; cutting edge sinuous, with row of small calcareous teeth increasing in size proximally; inner surface (Fig. 2 B) with tuft of short setae and row of tubercles or spines running parallel to upper margin on entire length, lower half with scattered tubercles or spines. Palm longer than carpus; upper margin with 2 rows of spines, spines on mesial row stronger and more produced, space between rows narrowing distally and with few spines or tubercles; outer surface strongly convex, with distinctly produced, subacute median crest extending beyond half length of palm but not reaching fixed finger (crest becoming stronger and wider distally, spines or spinulose tubercles forming crest increasing in size distally); upper part of outer surface flattened or slightly convex, with rows of tubercles, spines or spinules, distinct spinulose protuberance present at distal angle just below upper margin; lower part of outer surface covered with closely spaced rows of spines or spinulose tubercles along with long setae; inner surface (Fig. 2 B) covered with scattered spines or spinulose tubercles and long setae, 2 strong longitudinal ridges of large spines or spinulose tubercles on upper half and midline, upper ridge not reaching distal margin, median ridge running parallel to upper ridge and ending at midlength, additional small spinulose protuberances near dorsodistal angle just below upper margin; lower surface rounded, noticeably sinuous, with irregular rows of spines or spinulose tubercles; outer surface of fixed finger covered with small spines or tubercles, more closely packed in lower part; cutting edge sinus, with single row of large teeth increasing in size proximally; dense tuft of long setae on inner surface. Carpus longer than wide (Figs. 2 C, D); upper margin with 2 rows of spines; outer surface slightly convex, with scattered, small spines or spinulose tubercles and tufts of stiff setae, spines or tubercles decreasing in size proximally, small cluster of spines or tubercles present below upper margin distally, prominent spine present on distal margin, shallow and smooth depression or furrow present just below upper margin and widening distally; lower margin denticulate; inner surface (mesial) covered with closely spaced small spines or spinulose tubercles and tufts of stiff setae. Merus (Figs. 2 D, E) distinctly longer than wide; upper margin with small spine (visible in mesial view) on proximal one third; outer surface with row of strong spines just below upper margin, spines decreasing in size distally, upper half with scattered small spines or tubercles and tufts of stiff setae, lower half with few scattered tubercles; lower margin with distal strong spines followed by row of smaller spines (Fig. 2 D); inner (mesial) surface with scattered spinulose tubercles and tufts of setae (Fig. 2 E). Ischium with few scattered spinulose tubercles on ventral surface, ventromesial margin with row of setae.
Right cheliped (Figs. 3 A–C) moderately stout, with numerous tufts of long setae. Chela with wide hiatus between dactylus and fixed finger. Dactylus gently arched, about 1.7 times longer than palm; dorsal surface with few scattered tubercles (Fig. 3 A); mesial surface with 2 rows of spines continuing to tip of dactylus, space between rows narrowing distally and with small granules; cutting edge with few tiny calcareous teeth on distal half (Fig. 3 C). Palm longer than carpus; dorsal surface with scattered spinulose tubercles mesially and row of small spines or spinulose tubercles along lateral margin; ventral surface slightly convex, with scattered spines (Fig. 3 A). Fixed finger slightly curved; dorsal surface with small spines or spinulose tubercles, small scattered pits present distally; cutting edge with few acute calcareous teeth distally and proximally, no teeth on median part; ventrolateral margin with scattered pits (Fig. 3 B). Carpus with large distal spine followed by 3 or 4 small spines on dorsomesial margin (Figs. 3 A, C); dorsal surface covered with small spines or spinulose tubercles mesially and laterally, wide furrow present on midline(Figs. 3 A); lateral surface with scattered tufts of setae ventrally (Fig. 3 B). Merus covered with long setae entirely on dorsal margin; lateral surface with scattered tufts of short setae on dorsal half distally and with row of long setae along ventral margin; mesial surface smooth (Figs. 3 B, C). Ischium with few scattered spinulose tubercles on ventral surface, ventromesial margin with row of setae.
Ambulatory legs (second and third pereopods) (Figs. 4 A–D) subequal in length. Dactyli 1.3–1.4 times longer than propodi, 7.6–7.8 times longer than wide; dorsal margins unarmed; lateral surfaces each with single furrow running parallel to dorsal margin in second pereopods (Fig. 4 A) but without such furrow in third pereopods (Fig. 4 C); mesial surfaces each with 2 rows of moderately short setae and no median furrow in second (Fig. 4 B), and with a single median furrow covered with short setae in third (Fig. 4 D). Propodi with moderately long setae scattered on dorsal, ventral and lateral surfaces; dorsal and ventral surfaces unarmed but slightly crenulated (Figs. 4 A–D). Carpi of second pereopods each with strong distal spine followed by row of smaller spines and with tufts of setae on dorsal margin (Figs. 4 A, B); lateral faces each with dorsal row of moderately long setae, not reaching distal margin (Fig. 4 A); mesial faces with long scattered setae (Fig. 4 B). Carpi of third pereopods each with only strong dorsodistal spine (Fig. 4 C); mesial faces each with small but distinct spine near dorsodistal angle (Fig. 4 D); lateral and mesial surfaces with scattered tufts of short setae. Meri with tufts of long setae on dorsal and ventral margins; dorsal margins of second pereopods each with row of small spines (Fig. 4 A) but unarmed in third pereopods (Fig. 4 C); mesial faces of second each with dorsal row of long stiff setae in second (Fig. 4 B) and with scattered tufts of setae in third; lateral faces with long scattered setae (Fig. 4 A); ventral surfaces unarmed. Ischia each with tufts of long setae but without spines on dorsal and ventral margins.
Fourth pereopods chelate. Dactylus slightly shorter than length of rasp of corneous scales on propodus; dorsal margin with row of minute spines, terminating in sharp tip; ventral margin with 2 or 3 small spines distally. Propodus with produced dorsodistal margin; rasp composed of numerous corneous scales becoming larger marginally. Carpus with 3 distinct (1 median and 2 distal) and few smaller spines on dorsal margin (Fig. 1 D).
Anterior lobe of sixth thoracic sternite faintly bilobed, each lobe with 2 tiny spines anterolaterally on large depression and tuft of moderately long setae (Fig. 1 G).
Pleon twisted or weakly straight. Males and females with unpaired second to fifth pleopod.
Telson with very small medial cleft; left posterior lobe larger than right; terminal margin of left lobe slightly rounded, with and 5or 6 prominent spines and row of numerous spinules extending to lateral margin; right posterior lobe with terminal margin almost straight and armed with 3 or 4 prominent spines and row of smaller spines (Fig.1 H).
Variation. The degree of the sculpture on the outer and inner surface of the left chela varies between smaller (<3 mm SL) and larger specimens. The longitudinal ridges on the outer and inner surfaces of the palm are weaker in the smaller specimens than in the larger specimens.
Coloration. In fresh condition. Shield, ocular, and antennular and antennal peduncles cream. Left cheliped generally cream, median ridge on palm light brown, carpus and merus also cream. Right cheliped entirely cream. Second and third pereopods cream, with light orange bands on carpi and dactyli.
Habitat. Sandy or muddy substratum near the low tide mark.
Distribution. So far known only from Koliyak and Dandi, the Gulf of Khambhat, Gujarat State, northwestern India.
Etymology. The new species is named in honor of Dr. B. F. Chhapgar for his valuable contribution to the study of crustacean fauna of Gujarat and Maharashtra States, India.
Remarks. Diogenes chhapgari n. sp. belongs to the D. edwardsii species group as defined by Asakura & Tachikawa (2010). Within the informal species group, the new species appears closest to D. singaporensis Rahayu, 2015 in having the following characters: the antennal acicle being elongate and triangular; the palm of the left cheliped with more or less developed median crest, but without a transverse row or arc of proximal spines on the outer surface, and with two crests of tubercles on the dorsal half of the inner surface; and the carpi of the second pereopods each with a row of small but distinct spines on the dorsal surface. However, D. chhapgari n. sp. differs from D. singaporensis in the absences of a dorsodistal spine on the fourth segment of the antennal peduncle, a distal spinulose protuberance or low ridge on the upper margin of the palm of the left cheliped, and a distomedian spinulose protuberance on the outer surface of the carpus of the left cheliped (cf. Rahayu 2015). The absences of such spinulose protuberances on the carpus and palm of the left cheliped immediately distinguish D. chhapgari n. sp. from D. goniochirus Forest 1956 of the D. edwardsii species group (cf. Forest 1956; McLaughlin 2002b).
Diogenes chhapgari n. sp. is also allied to D. avarus and D. karwarensis in the general morphology of the antennal acicle, palm and carpus of the left cheliped, and carpi of the second pereopods. The new species is, however, distinguished from the two known species by the palm of the left cheliped with a distinct spinulose protuberance on each outer and inner surface near the distal angle just below the upper margin and two crests of tubercles on the dorsal half of the inner surface of the left palm, which have not been described and illustrated in the latter two species (cf. Siddiqui et al. 2004). The new species further differs from D. karwarensis in the absence of a dorsodistal spine on the fourth segment of the antennal peduncle.
description: Published as part of Trivedi, Jigneshkumar N., Osawa, Masayuki & Vachhrajani, Kauresh D., 2016, A new species of the genus Diogenes Dana, 1851 (Crustacea: Decapoda: Anomura: Diogenidae) from Gujarat, northwestern India, pp. 189-197 in Zootaxa 4208 (2) on pages 190-195, DOI: 10.5281/zenodo.203900