Eiconaxius farreae Ortmann, 1891

(Figs. 1–7)

Eiconaxius farreae Ortmann, 1891: 49–50 (in part), pl. 1, fig. 4. –– Sakai 1992: 162–163, fig. 5; 2011: 278–279 (in part). –– Komai 1999: 63; 2011: 328 (in part), fig. 10D. –– Sakai & Ohta 2005: 70–73 (in part). –– Komai & Tsuchida 2012: 37, table 1 (list).

? Axius (Iconaxiopsis) farreae. — Borradaile 1903: 537 (list).

? Axius (Eiconaxius) farreae. — Balss 1914: 88. –– Yokoya 1933: 52.

Iconaxiopsis farreae. — Balss 1925: 209 (list), 211 (list).

Axius (Eiconaxius) farreae. — De Man 1925a: 16 (list); 1925b: 125–126, text-figs. 3–3d.

Axius farreae — Sakai 1987: 304 (list).

Eiconaxius farrear (sic). –– Sakai 2014: 624, table 2.

Not Eiconaxius farreae. –– Sakai & Ohta 2005: figs. 1, 2.

Not Eiconaxius farreae. –– Komai et al. 2019: 11. = Eiconaxius reconditus n. sp.

Type material. Lectotype: MZS Cru313, male (cl 5.6 mm), Sagami Bay, 100–200 fathoms (180–360 m), 1881, coll. L. Döderlein, herein designated to stabilize the species identity.

Paralectotypes: MZS Cru4428, 5 males (cl 3.2–4.7 mm; one male not measured because of damage), 1 female (cl 5.8 mm), 1 ovigerous female (cl 5.4 mm), 2 juveniles (cl 2.5 mm; one specimen not measured because of damage), same data as lectotype; MZS Cru314, 1 specimen (not sexed or measured), same data as lectotype, inside host sponge; MZS Cru315, 1 specimen (not sexed or measured), same data as lectotype, inside host sponge.

Other material examined. CBM-ZC 10048, 1 juvenile (cl 3.6 mm), Sagami Bay, SE of Hatsushima Island, 35°00.51’N, 139°12.30’E, 486–549 m, TRV Shin’yo-maru, 2002 research cruise, stn 23, 23 October 2002, dredge, coll. T. Komai; CBM-ZC 10058, 3 males (cl 4.7–6.4 mm), 1 ovigerous female (cl 6.4 mm), Sagami Bay, W of Arasaki, 35°12.19’N, 139°29.62’E, 338–351 m, RV Rinkai-maru, dredge, 22 January 2003, coll. T. Komai; CBM-ZC 10098, 2 males (cl 5.8, 6.0 mm), 1 female (cl 4.7 mm), Sagami Bay, S of Jogashima, 35°03.39’N, 139°35.53’E, 587–651 m, RV Tansei-maru, KT07-31 cruise, stn L-2’-500, 28 November 2007, dredge, coll. T. Komai; CBM-ZC 12753, 3 males (cl 3.4–5.9 mm), 3 females (cl 4.5–5.6 mm), Sagami Bay, off Jogashima, 35°06.10’N, 139°34.28’E, 218–318 m, RV Rinkai-maru, dredge, 10 January 2012, coll. H. Kohtsuka (specimens of E. mortenseni and E. reconditus n. sp. were collected together); CBM-ZC 12985, 1 ovigerous female (cl 5.4 mm), Sagami Bay, off Jogashima, 35°06.04’N, 139°34.05’E, 364– 158 m, RV Rinkai-maru, dredge, 13 January 2012, coll. H. Kohtsuka (specimens of E. mortenseni and E. reconditus n. sp. were collected together); CBM-ZC 13786, 1 male (cl 6.0 mm), Sagami Bay, W of Jogashima, 35°07.24’N, 139°33.52’E, 287–309 m, RV Rinkai-maru, dredge, 20 October 2014, coll. H. Kohtsuka; CBM-ZC 13861, 1 male (cl 5.7 mm), similar locality, 35°06.97’N, 139°34.17’E, 256–261 m, 25 June 2015, RV Rinkai-maru, dredge, coll. T. Komai; CBM-ZC 14488, 2 males (cl 4.0, 4.3 mm), 2 females (cl 5.4, 5.8 mm), 2 ovigerous females (cl 5.1, 5.9 mm), Sagami Bay, W of Jogashima, 35°07.35’N, 139°34.26’E, 219–320 m, 10 December 2015, RV Rinkai-maru, dredge, coll. H. Kohtsuka (specimens of E. mortenseni were collected together); CBM-ZC 16730, 3 males (cl 3.3–5.3 mm), 3 females (cl 4.9–5.4 mm), Sagami Bay, SW of Jogashima, 35°06.81’N, 139°33.78’E, 360– 292 m, RV Rinkai-maru, dredge, associated with Farrea sp., 15 February 2017, coll. T. Komai (specimens of E. reconditus n. sp. were collected together); CBM-ZC 16733, 2 males (cl 5.4, 6.0 mm), 5 females (cl 3.9–5.5 mm), 1 ovigerous female (cl 6.8 mm), Sagami Bay, W of Jogashima, 35°07.00’N, 139°34.20’E, 157–323 m, RV Rinkai-maru, dredge, associated with Farrea sp., 15 February 2017, coll. T. Komai (specimens of E. reconditus n. sp. were collected together); CBM-ZC 16738, 4 males (cl 5.0– 5.7 mm), 5 females (cl 4.1–5.9 mm), 1 ovigerous female (cl 6.2 mm), similar locality, 35°06.80’E, 139°33.40’E, 407–541 m, RV Rinkai-maru, dredge, 16 February 2017, coll. T. Komai; CBM-ZC 17523, 1 male (cl 5.3 mm), same data as CBM-ZC 14488; CBM-ZC 17524, 1 male (cl 5.9 mm), same data as CBM-ZC 14488; CBM-ZC 9910, 1 male (cl 7.3 mm), 1 female (cl 7.3 mm), Enshu Sea, S of Hamamatsu, Shizuoka Prefecture, 34°05.43’N, 137°57.29’E, 952–1060 m, RV Tansei-maru, KT04-6 cruise, stn EN-5, beam trawl, coll. T. Akiyama.

Diagnosis. Rostrum tapering evenly to subacute apex, 1.8 times as long as wide; dorsolateral margins crenulate or weakly denticulate; ventral surface unarmed. Carapace median gastric carina sharply delimited, unarmed; submedian and lateral gastric carinae absent. Pleuron 2 posteroventral angle weakly produced, subacutely or acutely pointed. Telson posterior margin roundly truncate. Cornea with light brown pigmentation; ommatidia distinct. Major cheliped merus with at least 1 denticle distally; palm wider distally than at mid-point; lateral and mesial faces smooth, devoid of tubercles; fixed finger occlusal margin proximally with broad blade-like tooth with point at midlength; proximal gape on palm deeply incised, unarmed, forming a conspicuous triangular gape when dactylus closed; dactylus occlusal margin entire, without conspicuous tooth or notch. Minor cheliped palm distolateral margin with triangular tooth at base of dactylus, distomesial margin with small acute tooth at base of dactylus. Pereopods 3–5 dactyli with few spiniform setae on lateral surfaces adjacent to flexor margin.

Redescription. Carapace (Figs. 2A, B, 3A–C) smooth, compressed laterally. Rostrum 0.2 carapace length, concave dorsally, tapering evenly to subacute or acute apex, 1.8 times as long as wide at base; lateral margins distinctly carinate, crenulate or almost smooth; middorsal carina sharp, extending from near apex of rostrum to anterior part of gastric region, depressed below level of lateral carinae in distal half of rostrum, elevated above lateral margins in posterior half of rostrum, posterior end not widened; ventral surface rounded, unarmed. Submedian and lateral gastric carinae absent. Antennal lobe obtuse. Anterolateral margin gently sinuous with broadly rounded pterygostomial margin. Cervical groove hardly discernible. Cardiac notch distinct.

Pleon (Figs. 2C, 3D) depressed dorsoventrally. Pleuron 1 ventrally rounded; pleuron 2 posteroventral angle weakly produced, acutely or subacutely pointed; pleuron 3 posteroventral angle acutely or subacutely pointed; pleuron 4 truncate, posteroventrally square; pleuron 5 generally rounded; anteroventral denticle present or absent in each pleuron 3–5; pleuron 6 triangular with blunt to acute apex, flared laterally. Tergites 1–6 all rounded. Pleomere 6 posterolateral process triangular with acute or subacute apex; posterodorsal margin with row of minute denticles. Telson (Figs. 2D, 3E) 1.3 times as long as wide, widest at third length, then slightly tapering to posterolateral angles, lateral margin slightly upturned, serrate with minute denticles, posterior margin roundly truncate or slightly convex, usually with small posteromedian spine; dorsal face unarmed.

Eyestalk (Figs. 2A, B, 3B, C) reaching third length of rostrum; cornea globular, with light brown pigmentation; ommatidia distinct.

Antennular peduncle (Figs. 2A, B, 3B, C) not reaching end of antennal peduncle article 4. Basal article unarmed.

Antennal peduncle (Figs. 2A, B, 3B, C) with article 1 unarmed. Article 2 with distolateral angle produced into elongate triangular blade, reaching nearly distal margin of antennular peduncle article 3. Scaphocerite a vertical blade, reaching midlength of article 5. Article 3 lower margin with distomesial tooth. Article 5 about half-length of article 4.

Maxilliped 3 (Fig. 6A) coxa with small spine on lower surface. Basis with small spine on lower distal margin. Ischium crista dentata consisting of c. 15 minute denticles. Merus slightly narrowing distally, unarmed. Carpus widened distally, unarmed. Propodus slightly concave on lower margin, subequal in length to carpus. Dactylus distinctly shorter than propodus. Exopod well-developed, reaching mid-length of merus, flagellum-like, multi-articulate, longest proximal article noticeably curved.

Chelipeds (pereopods 1) massive, compressed laterally, dissimilar from left to right, but subequal in length. Major cheliped (Figs. 4A, 5A) with ischium having 2 small denticles on lower mesial margin. Merus upper margin bluntly carinate, noticeably convex in outline, with 0–5 minute denticles; lower margin sharply carinate, with 1–8 denticles, decreasing in size proximally; lateral and mesial faces smooth, unarmed. Carpus distinctly wider than long; upper margin bluntly carinate, unarmed; lower margin with 1 small acute tooth. Chela 1.8–2.1 times as long as greatest width. Palm distal width subequal to width at midpoint, 1.1–1.2 times as long as greatest width; upper margin sharply carinate, nearly straight, unarmed, terminating in small spine; lateral surface gently convex, without tubercles or spines, but with sparse setae distally, dorsally and ventrally, and with distinct keel-like carina along lower margin, extending onto fixed finger, distolateral margin produced into broadly triangular lobe; mesial surface also unarmed, with scattered short setae and few tufts of longer setae distally, distomesial margin also produced into broadly triangular lobe; lower margin faintly sinuous. Fixed finger about 0.6 times as long as upper palm, slightly curved distally, terminating in subacute tip; mesial face with deep excavation along occlusal margin, delimited by distinct longitudinal ridge; occlusal margin proximally with broad blade-like tooth with point at midlength, proximal part leaving deeply incised, triangular gape between dactylus. Dactylus distally curved, terminating in subacute tip crossed with tip of fixed finger; upper margin carinate; lateral surface shallowly sulcate along midline; mesial surface bluntly carinate along midline; occlusal margin without distinct tooth.

Minor cheliped (Figs. 4B, 5B) with ischium having 1 or 2 tiny denticles on lower margin. Merus upper margin bluntly carinate, noticeably convex, with 0–6 minute denticles; lower margin minutely serrate; lateral and mesial faces smooth, unarmed. Carpus distinctly wider than long; upper margin bluntly carinate, unarmed; lower margin with 1 small acute tooth. Chela 2.0–2.2 times as long as greatest width. Palm widened distally, 0.9–1.0 times as long as greatest width; upper margin sharply carinate, nearly straight, unarmed, terminating in small spine; lateral surface gently convex, without tubercles or spines, but with sparse setae, and with distinct keel-like carina along lower margin, extending onto fixed finger, distolateral margin oblique, with distinct triangular tooth at base of dactylus; mesial surface also unarmed, with scattered short setae and few tufts of longer setae distally, distomesial margin oblique, with small acute tooth at base of dactylus; lower margin faintly sinuous. Fixed finger 1.2–1.3 times as long as upper palm, slightly curved distally, terminating in acute tip; mesial face with deep excavation along occlusal margin, delimited by distinct longitudinal ridge; occlusal margin slightly denticulate in proximal half, nearly smooth in distal half. Dactylus 1.5–1.6 times as long as upper palm, slightly curved, terminating in acute tip crossed with tip of fixed finger; upper margin carinate; lateral surface bluntly elevated along midline; mesial surface nearly flat; occlusal margin nearly straight, faintly to weakly denticulate. No hiatus between fingers.

Pereopod 2 (Fig. 6B) with ischium lower margin unarmed. Merus upper and lower margins unarmed. Carpus widened distally, subequal in length to palm upper margin. Palm 2.7 times as long as greatest width, with scattered tufts of short to long setae on surfaces; fixed finger deflexed, with numerous tufts of setae, obscuring tip; dactylus about half-length of palm, also with numerous tufts of setae, obscuring tip.

Pereopod 3 (Fig. 6C) with ischium and merus unarmed. Carpus 0.7 times as long as propodus. Propodus with 6 rows of spiniform setae on lateral surface adjacent to flexor margin, each of 2 or 3 setae. Dactylus (Fig. 6D) 0.3 times as long as propodus, laterally compressed, ovate, spatulate, with 8–9 closely spaced spiniform setae on convex flexor margin, plus unguis, and 4 facial spiniform setae on proximal part.

Pereopod 4 (Fig. 6E) shorter than, similar to pereopod 3. Propodus with 5 rows of spiniform setae, each of 2 or 3 setae. Dactylus (Fig. 6F) ovate, spatulate, with 7–8 spiniform setae on convex flexor margin, plus unguis, and 3 or 4 facial spiniform setae on proximal part.

Pereopod 5 (Fig. 6G) shorter than pereopods 3 and 4. Ischium unarmed. Merus about half-length of carpus and propodus combined, unarmed. Carpus about half-length of propodus. Propodus without transverse rows of spiniform setae, with distal brush-like setae consisting of grooming apparatus (Fig. 6G). Dactylus (Fig. 6G) ovate, spatulate, with 7–9 spiniform setae on convex flexor margin, plus unguis, no facial spiniform setae.

Branchial formula summarized in Table 2: pleurobranchs absent; arthrobranchs on maxilliped 3 to pereopod 4; epipods on maxilliped 1 to pereopod 4; podobranchs on maxilliped 2 to pereopod 4, that on maxilliped 2 rudimentary; flagellum-like exopods on maxilliped 1–3.

Pleopod 1 absent in males; consisting of 2 articles, uniramous in females. Male pleopod 2 with appendix masculina rod-like, slightly shorter than appendix interna, bearing some stiff setae in distal half (Fig. 3G). Pleopods 3–5 each with appendix interna.

Uropodal protopod with small spine on outer margin. Endopod (Fig. 3E) 2.0 times as long as wide, elongate oval, outer-distal margin serrate with 8–13 small teeth or denticles, no prominent lobe distally, with faint median ridge on upper surface. Exopod (Fig. 3F) 1.6 times as long as wide, oval, not reaching endopod, outer margin serrate with 11–22 small teeth or denticles, with faint longitudinal ridge on upper surface.

Eggs large, c. 1.7 mm in diameter.

Coloration in life. Body and appendages entirely whitish; cornea with light yellow-brown pigmentation (Fig. 7).

Size. Largest male cl 7.3 mm; largest female cl 7.3 mm, ovigerous females cl 5.1–6.8 mm.

Distribution. Restricted to Japanese Pacific side, from Boso Peninsula to Kumano Sea; at depths of 218–1060 m.

Habitat. The specimens examined were found in association with the farreaid sponge Farrea sp. Two other species, E. mortenseni and E. reconditus n. sp., were sometimes found in the same haul of dredging, although it remains unconfirmed if multiple species inhabit the same host sponge colony.

Remarks. Ortmann (1891) listed 16 specimens from Sagami Bay, Japan, in his original account of Eiconaxius farreae, but no holotype was designated at the time. De Man (1925b) redescribed E. farreae based on the syntypes. Sakai & Ohta (2005) listed one specimen remaining inside its host sponge (MZS Cru314) as the lectotype, but the authors did not express any deliberate intention to make a lectotype designation. Therefore, Sakai & Ohta’s (2005) action is invalid because it does not meet the requirements of the ICZN code article 74.7.3 as amended under ICZN Declaration 44 (International Commission on Zoological Nomenclature 1999, 2003), which requires a statement of deliberate intent.

During my visits to the Musée Zoologique, Strasbourg, in 1997 and 1998, I examined the type material of E. farreae, confirming that 13 specimens, separated into three lots (MZS Cru313–315), remained (see “ Material examined ”). Specimens in the lot MZS Cru313 seemed to have been once dried out. I did not try to confirm the identity of the two specimens still within the host sponge (MZS Cru314, 315), one of which (MZS Cru314) was later listed as the lectotype of E. farreae by Sakai & Ohta (2005), because it would require destruction of the host sponge. On the other hand, I found that one of the female specimens in the lot MZS Cru313, consisting of six male specimens, three female specimens (including one ovigerous) and two juveniles, did represent a species other than E. farreae. Herein, I designate one of the six male specimens (cl 5.6 mm) as the lectotype of E. farreae to stabilize the specific identity. The female specimen distinct from E. farreae is herein referred to E. reconditus n. sp. (see also “Remarks” under the account of E. reconditus n. sp.). Recently, I asked Dr. Marie Meister of MZS about whereabouts of the type material of E. farreae. At present, only one specimen, here designated as the lectotype of E. farreae, is present in MZS. It would appear that the other type specimens have not been returned after the loan to Dr. Katsushi Sakai (cf. Sakai & Ohta 2005). A new registration number MZS Cru4428 was given for the paralectotypes originally labelled as MZS Cru313 to isolate the lectotype in spite of the present condition.

Eiconaxius farreae is rather distinctive within the genus in the absence of lateral gastric carinae and the presence of a deep, triangular gape near the base of the fixed finger of the major chela. In most other congeneric species, the carapace is provided with lateral gastric carinae; the occlusal margin of the fixed finger of the major chela is configured otherwise (De Man 1925; Sakai 1992, 2011, 2014; Kensley 1996; Sakai & Ohta 2005; Poore & Collins 2009; Komai et al. 2010; Komai & Tsuchida 2012; Poore 2017, 2018, 2020; Poore & Dworschak 2018; Kou et al. 2020). Eiconaxius singularis (Zarenkov in Zarenkov & Khodkina, 1983), known from the Kapingamarangi Seamounts, NE of New Guinea, at depths of 1000–1350 m, is the only other species without lateral gastric carinae on the carapace, but differs from E. farreae in the narrowly triangular rostrum, the presence of short gastric submedian carinae on the carapace and the absence of a deep triangular proximal gape on the fixed finger of the major cheliped (Zarenkov in Zarenkov & Khodkina 1983: fig. 2).

Balss (1914) provided a record of E. farreae [as Axius (Eiconaxius)] with material from Uraga Strait, Sagami Bay and Tokyo Bay, but the confirmation of the real identity of the specimens studied by Balss (1914) requires reexamination of the specimens. Here the record by Balss (1914) is included questionably in the synonymy.

Yokoya (1933) recorded E. farreae [as Axius (Eiconaxius)] from two Japanese locations (near Omae-zaki, Shizuoka Prefecture and Goto Islands, Nagasaki Prefecture) with a statement “it strictly agrees with description of the author”. Nevertheless, reexamination of the material is recommended to confirm the identification by Yokoya (1933).

Sakai & Ohta (2005), who examined the type series of Eiconaxius farreae, identified one specimen from Merase Bank, SW of Tateyama, Boso Peninsula, as that species. However, the figures provided by the authors (Sakai & Ohta 2005: figs. 1, 2) show that their specimen is substantially different from E. farreae rediagnosed herein: the carapace bears clearly delimited lateral gastric carinae; submedian gastric carinae are also present following the median gastric carina; the major cheliped fixed finger is devoid of a proximal triangular gape on the occlusal margin, but armed with a row of minute teeth distal to the prominent blade-like tooth on the proximal half; the major cheliped dactylus bears a distinct proximal tooth on the occlusal margin. It is likely that the specimen reported by Sakai & Ohta (2005) represent an undescribed species of Eiconaxius (see also the account of E. reconditus n. sp.).

Komai (2011) recorded E. farreae from Sagami Bay. Reexamination of part of the material studied by Komai (2011) has revealed that E. reconditus n. sp. was mixed up (CBM-ZC 10058, 1 female cl 5.2 mm; CBM-ZC 10099, 1 female cl 3.8 mm).

Sakai (2014) compared his new species Eiconaxius kumejimaensis Sakai, 2014 with E. farreae (as E. farrear, sic), but the characters mentioned above immediately differentiate the two species. Sakai’s (2014) taxon is rather similar to E. reconditus n. sp. (see below).