Catapagurus insolitus , Komai, Tomoyuki & Osawa, Masayuki, 2009

Komai, Tomoyuki & Osawa, Masayuki, 2009, A new hermit crab species of the genus Catapagurus (Crustacea: Decapoda: Anomura: Paguridae) from the Ryukyu Islands, southern Japan, Zootaxa 2211, pp. 57-68: 58-67

publication ID 10.5281/zenodo.189867

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scientific name

Catapagurus insolitus

n. sp.

Catapagurus insolitus  n. sp.

[new Japanese name: Uruma-ebisu-yadokari] ( Figs. 1–5View FIGURE 1View FIGURE 2View FIGURE 3View FIGURE 4View FIGURE 5)

Material examined. Holotype: male (sl 1.8 mm), Awa, Nago, Okinawa Island, 10 m, sand, 2 February 2009, scuba diving, night, coll. Yusuke Yamada, CBM-ZC 9576.

Paratypes: 2 ovigerous females (sl 1.8, 1.9 mm), same data as holotype, CBM-ZC 9577; 1 male (sl 2.1 mm), Maeda, Onna, Okinawa Island, 8.8 m, fine sand, near submarine cave, 26 January 2003, scuba diving, night, coll. Yoshihisa Fujita, CBM-ZC 9578, 1 male (sl 2.1 mm), Maeda, Onna, Okinawa Island, 10 m, 26 February 2003, scuba diving, night, coll. Yoshihisa Fujita, CBM-ZC 9579; 1 ovigerous female (sl 3.2 mm), Maeda, Onna, Okinawa Island, 10.1 m, 26 February 2003, scuba diving, night, coll. Yoshihisa Fujita, CBM- ZC 9580; 1 male (sl 2.4 mm), Maeda, Onna, Okinawa Island, 9.9 m ,, 26 February 2003, scuba diving, night, coll. Yoshihisa Fujita, NSMT-Cr 20820; 2 males (sl 2.2, 2.5 mm), 1 female (sl 2.7 mm), 2 ovigerous females (sl 2.1, 2.5 mm), Maeda, Onna, Okinawa Island, 10 m, 26 February 2003, scuba diving, night, coll. Yoshihisa Fujita, NSMT-Cr 20821.

Description. Eleven pairs of biserial phyllobranchiae. Shield ( Fig. 1View FIGURE 1 A) slightly longer than broad; anterior margin between rostral lobe and lateral projections concave; anterolateral margins sloping; posterior margin roundly truncate; dorsal surface with numerous tufts of short stiff setae, arranged in longitudinal rows. Rostral lobe roundly triangular, extending as far as prominent lateral projections. Lateral projections roundly triangular, each with slender, submarginal spine. Carapace lateral lobes (not illustrated) narrow, weakly calcified. Posterior carapace 0.5–0.7 length of shield, poorly calcified generally; posterolateral plates moderately narrow anteriorly, narrowing into thin bands reaching to posterior margins; posteromedian plate short.

Ocular peduncles ( Fig. 1View FIGURE 1 A) relatively long, about 0.7 times as long as shield, slightly broadened basally, with scattered, minute ridges and short stiff setae; dorsolateral extension of ocular peduncle into corneal margin weakly bilobed; cornea somewhat dilated, diameter about 0.4 peduncular length. Ocular acicles narrowly triangular, moderately slender, falling far short of midlength of ocular peduncles, terminating acutely; moderately widely separated basally.

Antennular peduncles ( Fig. 1View FIGURE 1 A) overreaching distal corneal margins by at least full length of ultimate segments. Ultimate segment with 2 long setae at dorsodistal margin and with some very short setae on dorsal surface. Penultimate segment with few very short setae. Basal segment with slightly produced ventrodistal margin; statocyst lobe with tiny distal lobe.

Antennal peduncles ( Fig. 1View FIGURE 1 A) relatively stout, reaching or distinctly overreaching distal corneal margins. Fifth segment subequal in length to fourth segment, with some short stiff setae. Fourth segment also with some short stiff setae. Third segment unarmed on ventromesial distal angle but with few short stiff setae. Second segment with produced dorsolateral distal angle falling far short of midlength of fourth segment; dorsomesial distal angle with small spine. First segment with 1 spinule on lateral surface and with 1 spinule at ventromesial distal angle. Antennal acicle short, reaching or not reaching midlength of fourth segment, terminating in sharp spine, bearing 2–4 spines on mesial margin. Antennal flagellum long, distinctly overreaching stretched chelipeds and ambulatory legs; each article with few short setae.

Third maxilliped ( Fig. 1View FIGURE 1 B) with stout propodus and carpus; merus with prominent dorsodistal spine; ischium ( Fig. 1View FIGURE 1 C) with crista dentata consisting of 3–6 moderately small to large, acute teeth; accessory tooth prominent; basis with few minute teeth on mesial margin.

Chelipeds distinctly dissimilar, right stronger and longer in males ( Figs. 2View FIGURE 2 A –D, 3 A, B); subequal with right slightly stouter in females ( Fig. 3View FIGURE 3 C –E). Male right cheliped ( Figs. 2View FIGURE 2 A, B, 3 A) relatively stout, weakly compressed dorsoventrally. Chela elongate subovate, longer than carpus, 2.2–2.5 times longer than broad; lateral margin slightly convex in dorsal view. Dactylus 0.7–0.8 length of palm, slightly curved ventrally, crossing with fixed finger; dorsal surface minutely granular, with scattered moderately long to long setae, dorsomesial margin not delimited; mesial surface nearly smooth, with scattered setae; ventral surface also with scattered long setae; cutting edge with 1 blunt, prominent tooth at midlength and row of minute calcareous or corneous teeth in distal half, terminating in small calcareous claw. Palm slightly shorter than carpus; dorsal surface weakly convex, coarsely granular, with few short setae distally, dorsolateral and dorsomesial margins not delimited, proximolateral and proximomesial portions slightly elevated; lateral face granular; ventral surface weakly convex, nearly smooth, with scattered long setae. Fixed finger with 1 broadly triangular tooth at midlength and row of tiny calcareous teeth in distal half of cutting edge, terminating in small calcareous claw. Carpus subequal in length to merus, broadened distally, length 1.6–1.7 of distal width; dorsomesial margin slightly elevated, with irregular, partially double row of small, rounded tubercles, dorsolateral margin more strongly elevated than dorsomesial margin, also with irregular, partially double row of small, rounded or subacute tubercles; dorsal surface sparsely granular; lateral surface with numerous small rounded tubercles or granules becoming lower and smaller ventrally, ventrolateral margin unarmed; mesial face with rounded granules or tiny tubercles dorsally and with scattered minute longitudinal ridges ventrally, ventromesial margin tuberculate distally; ventral surface weakly convex, with scattered long setae. Merus with few short transverse ridges subdistally and with row of moderately short stiff setae on dorsal surface, dorsodistal margin with 1 small spine; lateral face with short vertical ridges (particularly numerous in distal half) and scattered short setae, ventrodistal margin sinuous, with row of tiny spinulose tubercles; mesial face nearly smooth, with scattered setae ventrally, ventromesial margin faintly sinuous, with 1 blunt distal spine followed by short row of tiny spinulose tubercles; ventrolateral margin also faintly sinuous, with row of tiny spinulose tubercles; ventral surface granular, with scattered setae. Ischium with 1 spinule at ventrolateral distal angle; ventral surface minutely granular; otherwise unarmed. Coxa unarmed or with 1 spinule at ventrolateral distal angle.

Female right cheliped ( Fig. 3View FIGURE 3 C –E) slender. Chela longer than carpus, somewhat compressed dorsoventrally, 3.1–3.6 times longer than broad, with weakly sinuous or faintly convex lateral margin. Dactylus slightly longer than palm, surfaces nearly smooth, with scattered tufts of short to moderately short setae; cutting edge with row of very small calcareous teeth interspersed by 1 or 2 minute corneous spinules, terminating in small, curved corneal claw. Palm distinctly shorter than carpus; dorsal surface slightly convex, sparsely granular particularly mesially, dorsolateral or dorsomesial margin not delimited; ventral surface also slightly convex, with several tufts of long setae extending onto fixed finger. Fixed finger with scattered tufts of setae on dorsal surface; cutting edge with row of small triangular teeth, terminating in small, curved corneous claw. Carpus subcylindrical, slightly broadened distally in dorsal view, length 2.4–2.9 of greatest breadth; dorsal surface sparsely granular, dorsolateral or dorsomesial margin weakly delimited, dorsodistal margin unarmed; lateral face sparsely granular dorsally, otherwise nearly smooth, ventrolateral margins entire; mesial face also granular dorsally, with scattered setae along midline, ventromesial margin also entire; ventral surface weakly convex, with few short to long setae. Merus with distinct transverse ridge subdistally and row of stiff setae on dorsal surface, dorsodistal margin with 1 prominent spine; lateral surface with few granules, ventrolateral margin faintly granular, with or without small distal spine; mesial face with sparse granules ventrally, ventromesial margin also faintly granular, with or without small distal spine; ventral surface with few setae. Ischium with small spine at ventrolateral distal angle; ventromesial margin smooth. Coxa with 1 spinule at ventrolateral distal angle.

Left cheliped ( Figs. 2View FIGURE 2 C, D, 3 B) slender, similar between males and females. Chela 3.1–3.5 times longer than broad, distinctly longer than carpus. Dactylus 1.5–1.6 times longer than palm, in lateral view slightly curved ventrally, in dorsal view nearly straight, with strongly curved, long corneous claw; dorsomesial margin not delimited; surfaces with tufts of short to long setae; cutting edge with row of small, narrowly spaced corneous spinules. Palm about half-length of carpus, slightly convex dorsal and lateral surfaces ornamented with minute longitudinal ridges and with few short setae; mesial face nearly smooth, with few setae; ventral surface convex, nearly smooth, with scattered long setae. Fixed finger terminating in curved, slender corneous teeth, with tufts of long setae on ventral surface; cutting edge with row of small calcareous teeth interspersed by 2 or 3 corneous spinules. Carpus slightly broadened distally, length 2.6 –3.0 of distal width; dorsolateral and dorsomesial margins each delimited with single or irregularly double row of rounded granules, dorsodistal margin unarmed; dorsal surface with sparse granules; lateral face coarsely granular, unarmed on ventrolateral margin; mesial face sparsely granular, with sparse short to long setae, unarmed on ventromesial margin; ventral surface slightly convex, with few long setae. Merus slightly longer than carpus, with 1 or 2 subdistal transverse ridges and row of moderately long setae on dorsal surface, dorsodistal margin unarmed or with tiny tubercle or spine; lateral face with minute vertical ridges on distal half and granules adjacent to ventral margin, and with short setae, ventrolateral margin weakly sinuous, with row of small tubercles or granules, terminating distally in small blunt or acute spine; mesial face nearly smooth, with few setae distally and ventrally, ventromesial margin sinuous, with small blunt distal spine and row of minute spinulose granules; ventral surface sparsely granular, with moderately long setae. Ischium with small spine at ventrolateral distal angle; ventromesial margin faintly denticulate; lateral surface sparsely granular ventrally; no conspicuous spines. Coxa unarmed or with 1 spinule at ventrolateral distal angle.

Ambulatory legs (second and third pereopods) ( Fig. 4View FIGURE 4 A, B) long, generally similar, right second overreaching right cheliped by almost full length of dactylus. Dactyli weakly blade-shaped, 0.9 –1.0 times as long as propodi, strongly compressed laterally, nearly straight in dorsal view, slightly curved ventrally in lateral view; greatest height at midlength, about 0.1 length; dorsal margins each armed with 17–30 slender corneous spinules or bristles becoming generally longer and more widely spaced distally; lateral surfaces slightly convex, with scattered short setae; mesial surfaces ( Fig. 4View FIGURE 4 C, D) shallowly sulcate with dorsal and ventral margins somewhat upturned, occasionally bearing sparse setules and with row of 13–23 bristles adjacent to ventral margin; ventral margin faintly sinuous. Propodi slender, slightly twisted, strongly compressed in distal halves; dorsal margins minutely granular, each with row of widely spaced, slender bristles mesially; lateral and mesial faces ( Fig. 4View FIGURE 4 E, F) minutely granular; ventral margins sharply carinate, minutely granular or denticulate, each with row of widely spaced, slender spinules at least in distal half. Carpi each with obliquely truncate dorsodistal margin, with or without dorsodistal tubercle, dorsal margins otherwise unarmed, only with few short setae; lateral faces minutely granular. Meri broad with convex dorsal and ventral margins; dorsal surfaces each with 1–3 small but distinct spines in distal 0.2 followed by row of low transverse ridges, and with sparse setae; lateral faces minutely granular, with few short setae dorsally; mesial faces ( Fig. 4View FIGURE 4 G, H) nearly smooth; ventral margins naked, ventrolateral distal angles each with 1 small spine; ventral surfaces in distal halves concave to accommodate ventral surfaces of flexed carpi, ventral halves granular (second) or nearly smooth (third). Ischia with few long setae on dorsal margins.

Fourth pereopods ( Fig. 1View FIGURE 1 D) semichelate; dactylus with row of 4 or 5 minute corneous spinules on ventral margin; preungual process ( Fig. 4View FIGURE 4 E) exceeding far beyond corneous claw, covered with short, stiff setae; propodal rasp composed of single row of corneous scales; carpus unarmed at dorsodistal margin. Fifth pereopods chelate.

Sixth thoracic sternite ( Fig. 1View FIGURE 1 F) with anterior lobe much smaller than posterior lobe, weakly divided into two rounded lobes, each lobe bearing short stiff setae anteriorly; posterior lobe broadly rounded, ventral surface flattish. Eighth thoracic sternite ( Fig. 1View FIGURE 1 G) very small, faintly or clearly bilobed, with 2 tufts of setae anteriorly.

Male with long right sexual tube ( Fig. 1View FIGURE 1 G, H) directed toward exterior and upward over dorsal surface of pleon, reaching left side, terminally bilobed. Left coxa ( Fig. 1View FIGURE 1 G) with small gonopore encircled by short stiff setae, occasionally with slightly protruding papilla (vas deferens). Female with paired gonopores.

Pleon dextrally twisted. Third and fourth pleopods in males ( Fig. 1View FIGURE 1 I, J) short, uniramous, fifth pleopod absent. Female with biramous second to fourth pleopods, fifth pleopod absent. Uropods greatly asymmetrical, with protopods not produced posteriorly. Telson ( Fig. 1View FIGURE 1 K) with triangular posterior lobes separated by moderately deep, broad subrectangular median cleft, each lobe terminating bluntlly or subacutely; oblique terminal margins each with row of minute bristles; lateral margins not chitinized, unarmed.

Coloration. Shield and ocular peduncles generally whitish, with scattered minute brown spots. Posterior carapace also whitish. Antennular peduncle translucent; ultimate segment with 2 dark brown bands each on proximal and subdistal parts. Antennal peduncle generally whitish, with minute brown spots. Chelipeds also whitish, with irregular-shaped, pale brown markings, most numerous on left chela. Ambulatory legs translucent on dactyli and propodi; propodi with some brown marks on dorsal surface; carpi and meri whitish, with some brown markings. See Fig. 5View FIGURE 5.

Size. Largest male sl 2.5 mm, largest female sl 3.2 mm, ovigerous females sl 1.8–3.2 mm.

Variation. As known in other congeneric species, the carpus of the right cheliped is much stouter in males than in females. The numbers of bristles on the dorsal and ventral mesial margins are highly variable. They are not always related to the size of the individual, but generally more numerous in larger specimens.

Distribution. So far known only from Okinawa Island, Ryukyus Islands.

Ecology. The specimens examined were collected from fine-sand or silt bottoms, which were occasionally near entrances of submarine caves on outer reef slopes, at depths of 8.8–10.1 m. The animals were very active at night and rapidly moved on the bottom. Gastropod shells for carcinoecia are rather small, and thus chelipeds and ambulatory legs are not fully retracted in the shell

Etymology. The specific name is from the Latin, insolitus  (uncommon), referring to the unusual armature on the antennal acicle of the new species.

Remarks. The present new species is assigned to the informal species group characterized by the bladeshaped ambulatory dactyli ( Asakura 2001; McLaughlin 2004), represented by the following ten species: C. albatrossae ( Asakura, 2001)  , C. alcocki McLaughlin  in Hogarth, Gherardi & McLaughlin, 1998, C. ensifer ( Henderson, 1893)  , C. granulatus Edmondson, 1951  , C. haigae ( Asakura, 2001)  , C. kosugei ( Asakura, 2001)  , C. lewinsohni ( Asakura, 2001)  , and C. maclaughlinae ( Asakura, 2001)  , C. sharreri A. Milne-Edwards, 1880  , and C. tuberculosus ( Asakura, 1999)  . Morphologically, C. insolitus  n. sp. is most similar to C. kosugei  in sharing the following characters: ocular acicles narrowly triangular; annenal acicle short, only barely reaching to midlength of fourth peduncular segment; coxae of chelipeds each with minute spinule distolaterally instead of distinct spine distomesially; ambulatory dactyli relatively narrow (greatest breadth 0.10–0.15 length), each with ventral row consisting of less than 30 bristles on mesial face; dorsodistal margins of propodi of ambulatory legs with spiniform bristles; carpi of ambulatory legs without strong dorsodistal spines; meri of ambulatory legs each with one to three distinct subdistal spines on dorsal surface; and protopods of uropods not produced posteriorly. However, the new species is unique within the genus, as well as the species group, in having multispinose antennal acicles. In other congeneric species, the antennal acicle lacks distinct spines. Other differences between the new species and C. kosugei  include the shape of the rostral lobe and the structure of the ambulatory dactyli. The rostral lobe is narrower and more conspicuous in C. insolitus  n. sp. than in C. kosugei  . The dactyli of the ambulatory legs in mesial view are much more strongly tapering distally in the new species than in C. kosugei  .

Multispinose antennal acicles are rare in the family Paguridae  , heretofore known only in Alloeopagurodes spiniacicula Komai, 1998 ( Komai 1998)  . In addition to that species, Alainopaguroides andamanensis McLaughlin, 2002  has an antennal acicle bearing one acute spine proximally on the mesial margin ( McLaughlin 2002; Komai & McLaughlin 2005). Komai (1998) considered the possession of a multispinose antennal acicle of generic level significance in the family Paguridae  . Although the possession of such a character may raise a question regarding generic assignment of the present new species, C. insolitus  agrees well with Catapagurus  in all other diagnostic aspects (cf. McLaughlin 2004), and thus we believe that the present generic assignment is valid. In addition, Asakura (2001: fig. 21 A) illustrated C. ensifer  as having a small median blunt spine on the mesial margin of the antennal acicle, although he did not mention the presence of the spine. The discovery of the present new species has shown that the armament of the antennal acicle is intragenerically variable in Catapagurus  .

Another unusual character of the new species is the possession of only third and fourth pleopods in males. Within Catapagurus  , this character is also seen in C. danida McLaughlin, 2002  , known only from the Andaman Sea off Phuket ( McLaughlin 2002). However, C. insolitus  n. sp. is easily distinguished from C. danida  by the possession of blade-shaped ambulatory dactyli in addition to the multispinose antennal acicle.

From Japanese waters, the following six species of the genus are known: C. hirayamai ( Asakura, 2001)  , C. imperialis ( Asakura, 2001)  , C. kosugei  , C. misakiensis  , C. toyoshioae ( Asakura, 2001)  , and C. tuberculosus  ( Asakura, 2001; Komai & Takeda 2006). The present new species is the seventh of the genus known from Japan. All these species have been recorded from warm temperate to tropical waters of the Japanese Archipelago, although actual distribution of each species is still poorly known. There is no doubt that cooperative work with scuba divers, who are interested in the local marine fauna, will be fruitful in documenting the biodiversity.