Diogenes pugilator, (ROUX, 1829)

Almón, Bruno, Cuesta, Jose A., Schubart, Christoph D., Armenia, Lisa & García-Raso, J. Enrique, 2022, Redescription of the hermit crab Diogenes pugilator (Decapoda: Anomura) reveals the existence of a species complex in the Atlanto-Mediterranean transition zone, resulting in the resurrection of D. curvimanus and the description of a new species, Zoological Journal of the Linnean Society 195, pp. 1116-1146 : 1119-1127

DIOGENES PUGILATOR (ROUX, 1829) S.S.

( FIGS 1A–F , 2A–F , 7A, D, G, J )

Pagurus pugilator P. Roux, 1829 (in Roux, 1828 –30): part 3, pl. XIV, figs 3, 4.

Pagurus varians O.G. Costa, 1838 (in Costa & Costa, 1838 –71).

Type material: Neotype: ♂ 3.0 mm (MNHN-IU-2019- 3215), France, Mediterranean Sea : Frontignan, near Sète, 43°27 ′ 11.5 ′′ N, 3°48 ′ 49 ′′ E, sand, shallow subtidal, 29 August 2019.

Topotypes: 2♂, same data as neotype, ( ZSMA20190 400- 0401) , 1 ♂ ( IEOCD-BR/2664 ) ; 1 ♂ ( IEOCD-BR/2676 ), 09 June 2018 ; 6 ♂ ( IEOCD-BR/2665-2669 ), 29 August 2019 .

Other revised material: Spain: off Ebro Delta, 2 ♂ ( ICMD 143 /1998), 40°35′N, 0°43 ′ E, 3–6 m, 4 May 1982 ; La Carihuela, Torremolinos, Málaga, 13 ♂ and 4 ♀ ( IEOCD-BR/2660-2663 ), 36°36 ′ 28.2 ′′ N, 4°30 ′ 1 3.6 ′′ W, sand, 2–4 m, 11 December 2019 ; Fuengirola, Málaga, 1 ♂ and 1 ♀ ( IEOCD-BR/2670 ), 36°32 ′ 57.92 ′′ N, 4°36 ′ 30.89 ′′ W, sand, 4 m, 4 March 2014 ; Pozuelo, Granada, 5 ♂ ( IEOCD-BR/2677-2678 - 2679 ), 36 °44 ′ 37. 95 ′′ N, 3°39 ′ 30.47 ′′ W, sand, subtidal, 10 January 2020 ; Guadarranque, Algeciras, 1 ♀ ( IEOCD-BR/2675 ), 36°10 ′ 49.7 ′′ N, 5°24 ′ 42.1 ′′ W, sand, 4 m depth, 11 December 2019 ; San García, Algeciras, 1 ♂ ( IEOCD-BR/2674 ), 36°06 ′ 17.5 ′′ N, 5°25 ′ 56.7 ′′ W, sand, 4 m depth, 25 July 1996 ; Tunisia: La Goulette, Tunis, 1 ♂ ( IEOCD-BR/2659 ), 4 ♀ ( IEOCD-BR/2671-2673 ), 36°49 ′ 10.80 ′′ N, 10°18 ′ 45.11 ′′ E, sand, 3–4 m, 24 November 2009 .

Redescription: Shield ( Figs 1A , 7D ) subquadrate, nearly as long as broad; rostral lobe broadly rounded, exceeded by lateral projections that are triangular, acutely pointed, with single spine at apex; anterior margins of shield between rostral lobe and lateral projections slightly concave; anterolateral margins sloping, smooth; anterolateral angles rounded, usually with two to three small spines (two left and three smaller right in holotype); lateral margins slightly convex; posterior margin truncate; dorsal surface slightly vaulted, with lateral margins each usually cut by few transverse spinulose ridges extending on to lateral surface of shield; dorsal surface with additional faint short, transverse rows of small tubercles and tufts of short, stiff setae. Branchiostegites with dorsal margin bearing a row of eight to nine strong spines. Posterolateral plates not well calcified, unarmed.

Ocular peduncles (including corneas) about 0.6 times as long as shield, moderately stout, slightly narrowed in middle; corneas not dilated, corneal diameter about 0.3–0.4 peduncular length; row of short, plumose setae on mesial margin of peduncles. Ocular acicles ( Fig. 1A, B ) subtriangular, with sinuous mesial margin; anterior margin slightly convex, bearing three to four (sometimes a small fifth) distal spines decreasing in size towards outer margin, innermost distal spine distinctly larger and often slightly curved; rest of anterolateral outer margin with 11–12 small tubercles of about the same size, occupying at least half of anterior margin. Intercalary rostriform process simple, slightly shorter than ocular acicles (including spines), tapering acutely.

Antennular peduncles ( Fig. 1A, C ) overreaching distal corneal margin by about 0.8–0.9 length of ultimate segment, reaching distal margin of antennal peduncle; third segment unarmed, not broadened distally, about 3.5 times longer than distal width, subequal in length to penultimate segment, with three simple setae on dorsal margin and a distal tuft near distodorsal margin; second segment unarmed, with row of short setae on dorsodistal margin; basal segment unarmed, except for the spinulose rounded ventrodistal border.

Antennal peduncles ( Fig. 1A ) overreaching distal corneal margin by 0.6–0.7 length of fifth segment; fifth segment with row of moderately long stiff setae on ventral surface and short setae dorsodistally, unarmed; fourth segment unarmed, with tufts of long setae on dorsodistal and ventrodistal border; third segment unarmed; second segment with distolateral outer process stout and acute, with subdistal smaller spine; smaller but strong spine on distomesial angle; plumose setae near both spines and ventral surfaces; ventrodistal border spinose; first segment with spinules of different sizes on distal border; plumose, short setae present on lateral and ventral surfaces. Antennal acicle short, subtriangular, reaching slightly below distal margin of fourth peduncular segment, bearing a simple strong terminal spine plus usually five spines along mesial margin, and tufts of setae on both mesial and lateral margins. Antennal flagellum short and robust, noticeably setose; articles with paired long ventrolateral setae and shorter setae on dorsal and ventral surfaces.

Third maxilliped ( Fig 1D ) basis unarmed; ischium with crista dentata bearing two prominent and two small distal spines, with two additional variably sized spines on proximal half; ischium and merus with rows of scarce setae on lateral margins; carpus, propodus and dactylus with dense tufts of thick, long setae in dorsodistal and dorsomedian margin, concealing part of segments; exopod peduncle reaching one-third of endopod carpal length.

Male left cheliped ( Figs 2A, B, F , 7A, G ) much larger than right ( Fig. 1E ). Dactylus about 0.8 times as long as palm measured along upper margin, slightly arched, ending in large calcareous claw, crossing tip of fixed finger; upper, inner margin well defined by a row of spinose tubercles, upper, outer margin by small spines; two more incomplete rows of small subacute tubercles running parallel to upper, outer margin; conspicuous one to two strong spinose tubercles at beginning of these additional rows, near joint of the dactyl with the palm; outer surface not flattened, covered with small subacute tubercles; lower margin with two rows of tufts of setae; some sparse setae covering outer surface and between dorsal rows; cutting edge sinuous, with row of calcareous teeth of various size, largest at distal half of dactyl; inner surface with irregular rows of tubercles in upper half running parallel to upper margin, reaching distal part of dactylus, defining a shallow concave area between the two rows; two irregular rows of tufts of dense plumose setae just above the cutting edge.

Fixed finger delimited proximoventrally by a shallow concavity separating the slightly convex outer surface of fixed finger from markedly inflated palm surface; lower margin with two to three rows of small, rounded tubercles extending on to palm; outer surface covered with small subacute tubercles; cutting edge sinuous, with single row of various sized teeth, largest in proximal area, with a row of spaced tufts of setae below it; inner surface almost smooth with some tubercles on proximal surfaces and three rows (upper, medial and lower) of tufts of short, stout setae.

Palm robust, about as long as high (max. medial length – maximum height); upper margin shorter than carpus; dorsal surface with irregular rows of spines, more produced on upper, outer margin, decreasing in size towards inner margin; space between rows widening distally and with less produced tubercles; outer surface strongly inflated in upper half, decreasing gently to lower region; distal lower part depressed near fixed finger; upper, outer part (below spinose row on upper margin) slightly concave, covered with small acute tubercles; distinct bispinose protuberance present at upper disto-outer angle; lower margin almost straight, defined by row of obtuse tubercles, with distal lower margin slightly concave; rest of palm outer surface with small spinose tubercles and some slightly larger subacute tubercles forming diffuse and not always well-defined rows; ventral margin of palm with blunt tubercles that continue along lower, inner face, defining a more or less flattened tuberculate area, delimited by sinuous crest-like row of large, rounded tubercles ( Fig. 2B inset; see also Fig. 7G ), defining an inflection change; rest of inner surface slightly flattened, covered with rounded, flat tubercles of different sizes and scarce simple setae associated with some of them; sometimes two rows of longitudinal slightly bigger tubercles outlined on upper half, and on medial zone, similar in extension reaching distal margin.

Carpus longer than high ( Figs 2A, B , 7A ); upper margin with two to three irregular rows of strong spines; outer surface convex, covered with small spines; row of stronger spines present on middle outer surface, largest near distomedial margin; area just below upper, outer and inner margins slightly concave, becoming deeper and widening proximally, innermost shallower; lower margin denticulate, convex in distal two-thirds, forming a marked sinus proximally; distoouter margin spinulose submarginally; pilosity on outer surfaces abundant but not dense; inner surface covered with closely spaced thick tubercles and tufts of stiff, plumose setae.

Merus longer than high ( Fig. 2A, F ), subtriangular in dorsal view; distal margin with spines of different sizes, largest on dorsal area, without setae; dorsal surface with rows of low acute tubercles, turning to obtuse spines distally, and tufts of long, plumose setae; lateral surface with small spines adjacent to dorsolateral and ventrolateral margins and spinose transversal furrow subdistally with sparse long setae, rest of lateral surface smooth and glabrous; ventrolateral margin denticulate, slightly concave in proximal half, accompanied by long, plumose setae and strong subdistal spines; mesial face with weakly calcified, u-shaped patch, distally divided by shallow transversal furrow dorsally bearing denticulate protuberances ( Fig. 2F ) and tufts of long thick setae; dorsodistal margin with spines of different sizes; ventrodistal margin defined by large acute tubercles with associated long, plumose setae. Ischium with short transverse row of small spines on distolateral surface ( Fig. 2A ) and longitudinal row of spines on ventromesial surface ( Fig. 2F ), with tufts of setae associated with spines and tubercles.

Female left cheliped ( Fig. 2C ) similar to males; larger tubercles on outer surface of palm more numerous than in males, but arranged in similar way; lower margin of palm slightly more sinuous, faintly concave distally; lower margin of carpus only slightly convex, forming a less prominent sinus proximally; spines on dorsolateral and ventrolateral merus margins smaller than in males, rest of lateral surface with low, rounded tubercles.

Right cheliped ( Fig. 1E ) appreciably shorter than left, robust, not reaching proximal margin of palm (usually midlength of carpus) of left cheliped; dactylus and fixed finger with relatively narrow hiatus, both terminatinginsmallcalcareousclaws. Dactylus slightly more than 2.0 times longer than palm (measured along mesial margin), gently arched; upper, inner and outer margins defined by rows of small tubercles with long setae; outer surface convex, covered with small spines arranged in rows; cutting edge with row of small calcareous teeth, regular in size, terminating in small calcareous claw and tufts of setae parallel to cutting edge; inner surface smooth except for tufts of setae parallel to cutting edge. Palm with upper, outer margin defined by a row of small spinose tubercles; outer surface broad, strongly convex, with irregular rows of small spinose tubercles, obscured by tufts of long setae; lower margin defined by small, obtuse tubercles; fixed finger broadened proximally; cutting edge with row of small, subacute calcareous teeth and two rows of tufts of long, stout setae parallel to the cutting edge; inner surface covered with evenly distributed low tubercles and associated long, plumose setae.

Carpus widened distally, with row of strong spines on upper, outer margin increasing in size distally, and an additional row of rounded tubercles below it, delimiting a broad depression between them; outer surface with low tubercles and numerous tufts of long setae; lower surface nearly smooth, with some scattered low, rounded tubercles; inner surface with distal margin dentate, rest of inner surface covered with low, rounded tubercles and sparse tufts of short, plumose setae.

Merus distal margin with spines of different size, largest on dorsal area, with long, simple setae; dorsal margin weakly delimited by a row of small, blunt tubercles, becoming obtuse small spines distally and tufts of long, plumose setae; lateral surface with small spines adjacent to dorsolateral margin and crenulate transversal furrow subdistally, with sparse, long setae, rest of lateral surface with small, rounded tubercles and sparse setae; ventrolateral margin delimited by a row of low, acute tubercles increasing in size distally, and tufts of long, plumose setae; mesial face with weakly calcified, u-shaped patch proximally, smooth, with ventromesial margin defined by row of acute tubercles of similar size. Ischium with short, transverse row of small spines on distolateral surface and longitudinal row of acute tubercles on ventromesial margin, with tufts of setae associated with spines and tubercles.

Second and third pereiopods ( Figs 2D , 7J ) moderately stout, subequal in length. Dactylus about 1.2 times as long as propodus, weakly curved; terminating in moderately small corneous claw; upper and lower outer surfaces unarmed, with rows of long, simple setae more numerous in lower outer surface; outer surface with shallow, longitudinal sulcus medially, with row of setae along lower margin of sulcus in one-fifth proximal border, then continuing along upper border; inner surface with longitudinal rows of long, stout setae adjacent to upper and lower margins and a short row of plumose setae occupying proximal one-fifth of inner sulcus.

Propodus about same length as merus (second) or shorter (third), with upper margin defined by row of spinules (second) or tiny blunt tubercles (third), and withrowofsetae; lateralsurfaceseachwithlongitudinal row of setae arising from tiny, low protuberances near upper margin and second inconspicuous row below midline; lower margins smooth with scarce short setae.

Carpus upper margin with row of strong spines, increasing in size distally and with row of sparse, plumose setae dorsally (second), or with small spines on upper margin, with only one dorsodistal spine (third); lateral surfaces with low tubercles arranged in two rows, and setae associated with them; ventral surfaces with sparse, short setae.

Merus upper margin with small spines increasing in size distally (second), almost smooth (third); lower margin dentate, with well-developed distal spine (second), or almost smooth, without distal spine (third); tufts of long, plumose setae on upper and lower surfaces. Ischium unarmed, with long setae on distal margin.

Fourth pereiopods ( Fig. 2E ). Dactyl with row of nine to ten minute spiniform setae on distal part of ventral margin. Propodus suboval, with numerous setae on unarmed dorsal margin; propodal rasp consisting of five to six rows of corneous scales, covering distoventral part, including fixed finger; rest of segments unarmed, with clumps of long, plumose setae.

Fifth pereiopods. Propodus almost as long as merus and two times longer than carpus; group of subacute corneous scales in distodorsal surface of propodus and smaller ones in dactylus and fixed finger; long clumps of strong simple setae.

Male unpaired left pleopods 2–5 uniramous, marginally setose. Female gonopores paired; two to four unpaired pleopods well-developed, biramous; fifth pleopods without exopod, as in male.

Telson ( Fig. 1F ) with small, median cleft, markedly asymmetrical; left posterior lobe with a strong terminal spine and with row of spinules on lateral margin, becoming blunt anteriorly; oblique terminal margin with few small spines; right posterior lobe with row of small spines on less oblique terminal margin, extending on to posterior half of lateral margin.

Coloration ( Fig. 7A, D, G, J ). Whitish ocular peduncles with orange stain at base, projecting towards apex in diffuse narrow line. Antennules with the central dorsal area covered by a brownish orange line; honey yellow flagellum. Antennal scales with a vermilion red stain at the base; antennal flagellum with vermilion red rings evenly spaced. Characteristic vermillion red paired stains on branchial zone of cephalothorax. Left cheliped with snow white background colour; merus and carpus with the upper half orange with greenish tints, and a narrow scarlet red stripe in the middle zone, complete in the merus, partial in the carpus. Hand with broad wood brown well defined spots in: upper half of the base of the dactylus, lower distal area of the palm, and proximal central area of the palm; faint oil green areas on the distal area of the propodus, and pale orange on the upper, proximal area. Right cheliped snow white background colour; arterial blood red spot on the upper, proximal carpal area; orange zones on the superior distal zone of the carpus and proximal of the propodus; buff orange ring near the proximal area of the dactylus. Second and third pereiopods of buff orange colour at the dorsal part (with the proximal and distal parts darker), whiter at the ventral half; arterial blood red dorsal lateral stripes at the mid merus, carpus (incomplete), propodus and base of the dactylus.

Habitat: Sandy beaches of tidal lagoons along intertidal or shallow subtidal areas, up to 25 m, although more frequent around 5 m depth.

Distribution: Known with certainty from the French Mediterranean (Frontignan, neotype locality), northeastern (Barcelona), and south-eastern Iberian Peninsula (Málaga, Granada, Algeciras) and Tunisian coasts (La Goulette). By the figure and coloration of the large cheliped in Costa (1839, T2, f2), its presence in Italy (Gulf of Naples and Taranto), seems also probable.

Remarks: A number of subspecies or varieties of D. pugilator have been established based on morphological differences, e.g. Diogenes pugilator orientalis for the Black Sea and Adriatic populations ( Codreanu & Balcesco, 1968). Currently, none of the European varieties have been accepted so far, because of the consideration of D. pugilator as a highly variable species ( Ingle, 1993). The application of molecular techniques has shown that, even if this consideration is true to a certain extent, there is in fact a number of different well-defined species, previously lumped under D. pugilator and that in future studies, some of these synonymized taxa could be revalidated in the light of new and updated information.

Since the type specimen is missing, and based on what is assumed to be the type locality area for Roux’s Diogenes pugilator , as well as morphological similarities, Diogenes pugilator sensu Roux (1829) is herewith re-described, and a neotype is proposed (based on recent material collected from the presumed type locality area), in order to establish a reference for future studies, helping to elucidate the real identity of D. pugilator s.s. and to distinguish it from other potential species of the complex. This is further achieved by replacing Roux’s missing samples with topotypes that may facilitate future comparisons.

Figures

Figure 1. Diogenes pugilator s.s. ♂ 3.0 mm, Frontignan, France, neotype, (MNHN-IU-2019-3215): A, anterior part of body; B, ophtalmic scales; E, right cheliped, outer aspect; F, telson, dorsal aspect. Diogenes pugilator s.s. ♂ 2.7 mm, Frontignan, France, topotype (ZSMA2019 0400): C, right antennular, inner view; D, left maxiliped 3, (inset: detail of the spines, ventral aspect). (Scales: A, C, E = 1 mm, B, D, F = 0.5 mm).

Figure 2. Diogenes pugilator s.s. ♂ 3.0 mm, Frontignan, France, neotype, (MNHN-IU-2019-3215): A, left cheliped, outer aspect (arrow indicating bispinose protuberance); B, left cheliped, dorsal aspect (inset: detail of the row of tubercles on the lower, inner surface). Diogenes pugilator s.s. ♀ 2.5 mm, La Carihuela, Málaga, Spain, topotype, (IEOCD-BR/2660-2661): C, left cheliped, outer aspect. Diogenes pugilator s.s. ♂ 2.7 mm Frontignan, France, topotype, (ZSMA2019 0400): D, left pereiopod 2 (insets: variations in P3 carpus; dactylus inner aspect); E, pereiopod 4; F, merus, mesial view (setae omitted). (Scales: A–C, F = 2 mm, D = 1 mm, E = 0.5 mm).

Figure 7. Live coloration of the three species of Diogenes: A–C, left cheliped, outer aspect; D–F, cephalothorax and cephalic appendages; G–I, detailed photographs of the inner face of palms, showing the shape of the row of tubercles; J–L, left pereiopod 2. A, D, G, J, Diogenes pugilator; B, E, H, K, Diogenes armatus sp. nov. C, F, I, L, Diogenes curvimanus.