Diogenes hawisi, Fitrian & Rahayu & Ismet, 2024

Fitrian, Tyani, Rahayu, Dwi Listyo & Ismet, Meutia Samira, 2024, A new species of hermit crab genus Diogenes Dana, 1851 from Papua, Indonesia (Crustacea, Decapoda, Anomura, Diogenidae), Zootaxa 5458 (1), pp. 130-140 : 132-136

Diogenes hawisi n. sp.

( Figs. 1‒3 )

Diogenes sp. 2 Fitrian, Madduppa, Ismet & Rahayu, 2022: 5306, fig. 1C. Type material. Holotype: male (4.6 mm), MZB Cru 5769 , st. Mi1 , 5°01’20.89”S, 137°05’42.73”E, 6 April 2021 . Paratypes: 2 males (3.0, 3.8 mm), 1 ovigerous female (3.0 mm), MZB Cru 5770 , same locality as holotype ; 2 males (3.2, 3.4 mm), 1 ovigerous female (2.8 mm), ZRC 2024.0057 , same locality as holotype ; 2 males (3.2, 4.2 mm), 2 ovigerous females (2.8, 3.2mm), MZB Cru 5771 , same locality as holotype, 6 October 2021 ; 3 males (4.4, 4.6, 4.8 mm), MZB Cru 5772, st. A1, 4°57’49.75”S, 136°49’47.53”E, 31 March 2021 ; 2 males (2.4, 3.0 mm), ZRC 2024.0058 , st. EM330, 4°48’90.00”S, 136°38’73.10”E, 26 May 2021 ; 2 males (2.5, 4.4 mm), ZRC 2024.0059 , st. Ma 1, 5°02’16.56”S, 137°05’42.73”E, 8 October 2020 ; 3 males (3.0, 4.0, 4.4 mm), MZB Cru 5773, Mi 1, 5°01’20.89”S, 137°05’42.73”E, 12 July 2022 ; 2 males (5.0, 5.4 mm), ZRC 2024.0060 , K1, 4°49’19,67”S, 136°35’06.14”E 2 June 2023 .

Other material examined. 3males, 1ovigerous female, ZRC2024.0061 , st.Mi 1, 5°01’20.89”S, 137°05’42.73”E, 6 April 2021 ; 1 female (2.9 mm), ZRC 2024.0062 , st. T5 , 4°55’04.64”S, 136°42’16.25”E, 21 February 2023 .

Description. Shield ( Fig. 1A ) approximately as long as broad; anterior margin between rostral lobe and lateral projections concave; anterolateral margins sloping anterolateral angles spinulose; lateral margin with few spines, posterior margin roundly truncate; dorsal surface with sparse tubercles, and transverse row of small spines or tubercles on third posterior. Rostral lobe tapered, produced, shorter or as far as lateral projections. Lateral projections triangular, each with terminal spinule. Branchiostegites with row of 7–9 small spines on dorsal margins.

Ocular peduncles ( Fig. 1A ) moderately short, 0.8 times as long as shield, stout, slightly widened distally, left slightly shorter than right; corneal width 0.3 times as long as peduncular length. Ocular acicles broad, subrectangular, basally separated by approximately 0.3 width of 1 acicle, with row of spines on terminal margin, mesialmost spine largest. Intercalary rostriform process stout, simple, not reaching tip of mesial spine of ocular acicle, with few long setae; no ventral spine.

Antennular peduncle ( Fig. 1A ) overreaching distal corneal margin by full length of ultimate article. Ultimate article with few setae, penultimate article almost glabrous. Basal article with strongly produced, acute ventrodistal margin; statocyst lobe weakly inflated in proximal half of article.

Antennal peduncle ( Fig. 1A ) overreaching distal corneal margin by 0.7–0.8 length of article 5.Articles 5 with few setae.Article 4 with few setae, small subdistal spine on dorsal surface. Article 3 unarmed. Article 2 with dorsolateral distal angle produced, spiniform; dorsomesial distal angle with smaller spine. Article 1 unarmed. Antennal acicle not reaching distal margin of article 4, terminating in strong spine, mesial margin with 5–7 spines, lateral margin with strong subdistal spine. Antennal flagellum about 2.4 times as long as shield, each article with long lateral setae, and sometimes with additional short seta dorsally.

Third maxilliped with dactyl slightly shorter than propodus, dense setae ventrally, propodus, carpus and merus approximately as long as each other, with numerous long setae on mesial margin, lateral margin with fewer setae, ischium with crista dentata composed of 4 teeth; basis with 2 strong teeth ( Fig. 1B, C ). Exopod overreaching base of carpus, with well-developed flagellum.

Left cheliped ( Figs. 1D–F , 2A ) elongate, much larger than right, narrow gape between dactyl and fixed finger. Dactyl 1.3–1.5 times as long as palm measured along upper margin, slightly arched; cutting edge with 1 large blunt calcareous tooth and additional much smaller calcareous teeth, terminating in strong calcareous claw, overlapped by claw of fixed finger; outer surface with broad, deep longitudinal sulcus, strong tuberculate ridge adjacent to cutting edge; upper margin with 3 rows of strong spines coalescent distally; inner surface with deep longitudinal sulcus near upper margin, and strong longitudinal median tuberculate ridges, sparse tubercles on remaining portion ( Fig. 1E ). Palm shorter than carpus, upper surface becoming broader distally, with irregular 3 rows of moderately large spines coalescent proximally; convex outer surface finely granulated; pronounced, broad tuberculate crest extending from proximoventral angle, oblique to carpal articulation then curving distally onto outer face in midline, not reaching articulation with dactyl, tubercles becoming smaller distally; smaller spines forming longitudinal row between medial crest and upper margin; lower margin with row of spines continued onto proximal margin as moderately large tubercles; fixed finger triangular, slightly deflexed, cutting edge with most pronounced tooth just proximal to midlength; lower margin with row of tubercles; outer face with pronounced tuberculate ridge extending proximally to point even with dactylar articulation, surface adjacent to cutting edge deeply concave, smooth; sparse tubercles near lower margin; inner face of palm tuberculate, with tufts of sparse setae on fixed finger ( Fig. 1E ). Carpus slightly longer than merus, distinctly longer than broad; upper margin with row of strong spines, largest distally; outer face covered by large tubercles, distal margin of outer face with row of small spines; lower margin with blunt spines; inner surface coarsely tuberculate. Merus ( Fig. 1F ) with upper margin and inner and outer lower margins irregularly spinose and tuberculate, larger spine distally on lower margin; remaining portion tuberculate. Setae very sparse on upper margin of dactyl and propodus; tufts of setae on cutting edges of dactyl and fixed finger, longer simple setae on upper margin of carpus and merus.

Right cheliped ( Figs. 1G , 2B ) when fully extended, reaching to distal margin of carpus of left cheliped, moderately narrow gape between dactyl and fixed finger, surface covered by tufts of long setae, not obscuring armature. Dactylus arched, 3 times as long as palm measured along upper margin; upper margin with 2 rows of spinulose tubercles; outer surface with irregular longitudinal rows of spines; cutting edge with row of small, calcareous teeth, terminating in small calcareous claw, slightly overlapped by fixed finger; inner surface with deep longitudinal sulcus near upper margin, and longitudinal median ridges with tufts of setae. Palm with double rows of moderately large spines on upper margin; outer surface with smooth area adjacent to upper margin, remaining portion with rows of spines extending onto fixed finger, lower margin with row of spines, inner face of palm with sparse spinules; fixed finger with small spines and tufts of setae, cutting edge with row of pointed calcareous teeth. Carpus longer than palm, row of large spines on upper margin, and shallow sulcus on outer face adjacent to upper margin, remaining portion with moderately large spines; distal margin of outer face with row of moderately large spines; lower margin not delimited; inner face with sparse tubercles. Merus with strong spines on distal margin continued to distolateral and part of distomesial faces; dorsal margin with numerous long setae arising from low protuberance, lateral face with few small spines.

Pereopods 2 and 3 left and right generally similar, slender ( Fig. 3 ). Dactylus 1.5 times as long as propodus, slightly curved ventrally, but not twisted, terminating in calcareous claw; dorsal margin with row of sparse moderately long setae; longitudinal median sulcus on lateral face; ventral margin with row of sparse short setae. Propodus distinctly longer than carpus; dorsal margin with row of small spines, and with row of sparse, moderately short setae; lateral face with irregular rows of small spines on left pereopod 2, right pereopod 2 smooth, row of sparser spines on left and right of pereopod 3. Carpus with row of small spines on dorsal margin and with row of moderately short setae; distolateral surface with row of small spines; ventral margin unarmed. Merus with moderately short setae on dorsal margin; dorsal and ventral margin of pereopod 2 with row of small spines, lateral face with sparse small spines, pereopod 3 unarmed. Ischium with row of setae on dorsal and ventral margin.

Pereopod 4 semichelate ( Fig. 1H ). Dactylus slightly curved, with long, dense setae dorsodistally. Propodus unarmed; propodal rasp consisting of numerous rows of small corneous scales. Carpus with small distal spine on dorsal margin. Pleon dextrally twisted. Male with 4 well-developed, unpaired left pleopods, uniramous, female also with 4 unpaired left pleopods, biramous.

Telson ( Fig. 1I ) with indistinct median cleft on terminal margin. Left lobe slightly larger but not longer than right, terminal margin with row of large spines interspersed with small spines, extending onto lateral margin; right lobe with large spines not extending on lateral margin; both terminal margin with row of short to long setae

Colour in preservative. Shield mottled with cream and light brown. Ocular peduncles pinkish cream, dark brown or reddish-brown rounded spot on each lateral face proximally, corneas black; ocular acicle and intercalary rostral process pinkish brown. Antennular peduncles ultimate segment with reddish brown band distally. Antennal peduncles cream, flagellum alternately transparent and brown. Chelipeds generally cream, spines and tubercles pink or reddish brown.

Etymology. This species is named after the late Dr. Hawis Maduppa, our esteemed colleague, good friend and very supportive supervisor of the first author. He is a researcher, field scientist and also avid educator in Department of Marine Science and Technology, Faculty of Fisheries and Marine Sciences, Institut Pertanian Bogor, Indonesia, specializing in marine bioecology, biodiversity and molecular ecology.

Variation. The left P2 of the holotype is slightly shorter than the left P3, right P2 and P3, possibly because it was regenerating after being injured. In other specimens examined, the P2 and P3 are of the same size. The morphological variation of the left cheliped is related to the size and sex of the individual. In the larger male (shield length 4.2 mm), the left cheliped is elongate, the palm is as long as broad, while in small specimens (less than 2.8 mm) and in females, it is broader, about 0.6‒0.7 times as long as broad. The telson varies from subequal between the left and the right lobes to the left lobe being longer and larger than the right. Morphological variability of this kind and sexual dimorphism is very often observed in species of Diogenes (see Forest 1956; Rahayu & Forest 1995; Siddiqui & McLaughlin 2003)

Remarks. Diogenes hawisi n. sp. mostly closely resembles D. edwardsii and D. laevicarpus in having longitudinal sulcus on the outer surface of the left cheliped dactyl, and a pronounced ridge on the outer surface of the left cheliped fixed finger. Nevertheless, D. edwardsii differs from D. hawisi n. sp. in the following characters: the outer surface of the left cheliped palm lacks a broad longitudinal tuberculate crest medially; the pronounced ridge of the left cheliped fixed finger consists of a row of well separated, large spinous tubercles, without a sulcus between this ridge and the cutting edge; the sulcus on the dorsal surface of the left cheliped dactyl is narrow and deep; the dorsal margin of the dactyl and palm, and ventral margin of the fixed finger and palm of the left cheliped is armed with well-separated, large, spine-like tubercles; the right cheliped has a relatively broad gape ( Fig. 2C, D ). As described above in D. hawisi n. sp. the outer surface of the left cheliped palm has a broad, tuberculate longitudinal crest medially; the pronounced ridge of the left cheliped fixed finger consists of rows of small tubercles, with the presence of a deep sulcus between this ridge and the cutting edge; the sulcus on outer surface of the left cheliped dactyl is also broad and deep; the upper margin of the dactyl and palm, and lower margin of the fixed finger and the palm of the left cheliped is armed with small, spine-like tubercles; the right cheliped has a narrow gape between the fingers ( Figs. 1D , 2A, B ). Furthermore, the fourth article of the antennal peduncles are unarmed in D. edwardsii (a small spine presence in the new species, Fig. 1A ).

Diogenes laevicarpus is distinguished from D. hawisi n. sp. by the short, narrow, longitudinal tuberculate crest that stops abruptly before the mid-length of the outer surface of the left cheliped palm; the ridge of the left cheliped fixed fingers is smooth, without a deep sulcus between this ridge and cutting edge, the dactyl of the left cheliped is relatively short, about 1.1 times as long as the palm; the tubercles on the outer surface of the left cheliped palm and fixed finger are drop-like or flattened tubercles; the right cheliped has a broad gape between fingers ( Fig. 2E, F )

Figures

FIGURE 1. Diogenes hawisi n. sp., holotype, male, 4.6 mm, MZB Cru 5769. A, shield and cephalic appendages; B, right third maxilliped, lateral view; C, ischium and basis of left third maxilliped, lateral view; D, chela and carpus of left cheliped, outer view; E, chela of left cheliped, inner view; F, merus of left cheliped, lateral view; G, chela, carpus and merus of right cheliped, outer view; H, left pereopod 4, lateral view; I, telson. Scale: A, B, D‒G = 1 mm; C, H, I = 0.5 mm. Setae partially omitted.

FIGURE 2. A, B, Diogenes hawisi n. sp., holotype, male, 4.6 mm, MZB Cru 5769. C, D, Diogenes edwardsii (De Haan, 1849), male, 8.9 mm MZB Cru 5775; D, E, Diogenes laevicarpus Rahayu, 1996, male, 5.0 mm (MZB Cru 5776).A, C, E, left cheliped, B, D, F, right cheliped.

FIGURE 3. Diogenes hawisi n. sp., holotype, male, 4.6 mm, MZB Cru 5769.A, right P2, lateral view; B, right P3, lateral view; C, left P2 lateral view; D, left P3 lateral view. Scale = 1 mm. Setae omitted.