Galilia petricola, Komai, Tomoyuki & Tsuchida, Shinji, 2014

Komai, Tomoyuki & Tsuchida, Shinji, 2014, Deep-Sea decapod crustaceans (Caridea, Polychelida, Anomura and Brachyura) collected from the Nikko Seamounts, Mariana Arc, using a remotely operated vehicle “ Hyper-Dolphin ”, Zootaxa 3764 (3), pp. 279-316 : 300-305

Galilia petricola n. sp.

( Figs. 18–21 , 30 C)

Material examined. RV “Natsushima”, NT10-13 cruise, ROV “Hyper-Dolphin”, dive #1165, Northeast Nikko Seamount, 31 July 2010, three of four specimens collected from four points (23°06.712’N, 142°21.848’E, 562 m; 23°06.766’N, 142°21.934’E, 551 m; 23°06.617’N, 142°21.836’E, 595 m; 23°06.639’N, 142°21.848’E, 576 m) were examined: holotype, male (23.8 × 25.2 mm), NSMT-Cr 22721; paratypes, 1 male (22.4 × 23.7 mm), 1 ovigerous female (22.2 × 25.0 mm), JAMSTEC 0 81532.

Description. Males. Carapace ( Figs. 18 , 19 A, B, C) rounded, slightly broader than long; regions well demarcated, grooves between regions distinct, especially branchial ones; surface covered with numerous small pearliform or fungiform granules and numerous bumps; hepatic region with 2 rounded tubercles, lower tubercle larger than upper one; cardiac region prominently swollen, with low tubercle at top; intestinal region with 2 large rounded tubercles, directed posteriorly; branchial region with 16 or 17 small tubercles. Front ( Fig. 19 E) distinctly bilobed, lobes low, separated by broad V-shaped cleft, each lobe triangular, tip rounded, surface covered with numerous small granules. Orbit with 3 fissures; inner orbital lobe clearly separated from lateral angle of front. Suborbital region with deep groove.

Epistome ( Fig. 19 E) very short; anteromedian part of buccal cavern roundly triangular.

Eye ( Fig. 19 A, B, E) small; eyestalk strongly constricted at midlength.

Basal antennular article filling lower half of fossa when retracted ( Fig. 19 E); distal 2 articles of antennular peduncle and flagella retracted slightly obliquely in upper half of fossa. Antennal peduncle fully visible in anterior view, extending into orbit; flagellum filiform.

Mouthparts not dissected. Third maxilliped ( Figs. 19 B, 21A) covered with pearliform or fungiform granules of various sizes on outer surface. Ischium with sharp, entire mesial margin. Merus subtriangular, slightly bent dorsally in situ, about half length of ischium measured along mesial margin; inner face mesially with distinct excavation accommodating carpus to dactylus. Distal 3 segments tapering distally. Exopod slightly narrower than endopod, slightly tapering to rounded distal margin, without conspicuous tooth on lateral margin, proximolateral angle gently rounded; inner surface deeply grooved medially, with strong keel mesially.

Chelipeds ( Figs. 18 , 20 A) less than 2 times of carapace length, entirely covered with pearliform or fungiform granules on all segments, including fingers (granules on fingers fine, minute). Merus subcylindrical, not curved. Carpus about half length of palm, slightly widened distally, without ridges on external surface. Palm slightly inflated, slightly tapering distally; dorsal surface slightly depressed in distal half. Fingers subequal in length to palm, almost straight, cutting edges with row of tiny, blunt or subacute denticles; fixed finger with 2 weak granular ridges along midline on external and internal surfaces, ventral margin sharply keeled; dactylus also with 2 weak granular ridges on external and internal surfaces and distinct dorsal ridge.

Ambulatory legs ( Fig. 18 ) relatively short, surfaces covered with closely packed granules; length decreasing gradually from first to fourth legs. Dactyli subequal to or slightly shorter than propodi, gently arcuate, terminating in sharp corneous unguis.

Thoracic sternum ( Fig. 19 D, F) covered with pearliform or fungiform granules (lateral granules smaller and more closely spaced than mesial ones; sternite 2 medially produced in small triangular process; sternites 3 and 4 swollen, raised; sternites 5–7 medially depressed, appearing sunken; sterno-abdominal cavity narrow, very deep.

Pleon ( Fig. 19 B, D, F) with third to sixth pleomeres fused, shallow transverse grooves, suggesting divisions between third, fourth and fifth pleomeres, seen; distal border of sixth pleomere elevated, with distinct median process directed ventrally. Telson ( Figs. 19 F, 21B) slender, noticeably elongate, about two-thirds of fused third to sixth somites in length, tongue-shaped, strongly curved in proximal half as it fitting into sterno-abdominal cavity of swollen sternites 4 and 5 ( Fig. 19 B).

First gonopod ( Fig. 21 C, D) slender, gradually tapering distally, reaching to midlength of thoracic sternite 4; distal third curving towards sternum at approximately 70° angle, with small terminal pore ( Fig. 21 E); internal surface with scattered microscopic setae ( Fig. 21 F); tip blunt. Second gonopod ( Fig. 21 G–I) with distal segment divided in 2 parts, distal part lance-shaped, subacutely pointed; proximal part gently curved ventrally, strongly compressed laterally, with prominent setose lobe proximolaterally.

Female. Generally similar to male. Cheliped merus proportionally slightly shorter than that of male. Sternoabdominal cavity deeply excavate; valvae each with prominent flange. Abdomen ( Fig. 20 B) dome-shaped, third to six pleomeres fused though shallow transverse grooves suggesting division of these pleomeres still discernible; surfaces covered with rounded, flattened granules. Telson ( Fig. 21 J) subtriangular with distinctly concave lateral margins; tip rounded; surface covered with flattened granules.

Coloration in life. Carapace generally orange; chelipeds and ambulatory legs banded with orange and white.

Distribution. Known only from Northeast Nikko Seamount, 562– 595 m.

Ecology. The collected individuals were found on rock surfaces or rubbles ( Fig. 29 C).

Remarks. The new species is very similar to the type species of the genus, Galilia narusei Ng & Richer de Forges, 2007 in the general structure of the carapace, thoracic sternum, abdomen, telson, and gonopods. Nevertheless, G. petricola n. sp. is distinguished from G. narusei by less prominent tubercles on the branchial regions of the carapace and the different structure of the first gonopod. In the new species, the distal one-third of the first gonopod curves toward the sternum at approximately 70° angle, rather than 90° angle in G. narusei ; the distal part is stouter with the tip more narrowly pointed in G. petricola n. sp. than in G. narusei (cf. Ng & Richer de Forges 2007: Fig. 4 G, H).

In their original description of G. narusei, Ng & Richer de Forges (2007: 18) stated that “Basal antennular article large, completely sealing fossa when retracted.” However, their figure (Ng & Richer de Forges 2007: fig. 2C, E) clearly shows the distal articles of the antennular peduncle are retracted in the upper surface of the fossa and are not concealed by the basal article. Consequently, we assume that the interpretation of the structure of the antennule and antennular fossa by Ng & Richer de Forges (2007) was not correct. In the present new species, the basal antennular article fills only the lower half of the antennular fossa.

Etymology. Combination of the Latin petra (= rock) and colus (= living), in reference to the habitat of this new species.

Figures

FIGURE 4. Plesionika unicolor n. sp., holotype, ovigerous female (pcl 13.0 mm), NSMT-Cr 22719, thoracic appendages, lateral view. A, left third maxilliped; B, left first pereopod; C, left second pereopod; D, right second pereopod; E, right third pereopod; F, left fourth pereopod; G, left fifth pereopod. Scale bar: 2 mm.

FIGURE 18. Galilia petricola n. sp., holotype, male (23.8 × 25.2 mm), NSMT-Cr 22721, entire animal in dorsal view (in preservative).

FIGURE 19. Galilia petricola n. sp., holotype, male (23.8 × 25.2 mm), NSMT-Cr 22721. A, carapace, dorsal view; B, anterior part of cephalothorax, anterior view; C, posterior part of carapace and first and second abdominal somites, posterior view; D, posterior part of carapace, abdomen, and thoracic sternum, posteroventral view; E, close up of frontal region of carapace, anterior view; F, abdomen, telson and thoracic sternum, ventral view.

FIGURE 20. Galilia petricola n. sp. A, holotype, male (23.8 × 25.2 mm), NSMT-Cr 22721; B, paratype, ovigerous female (22.2 × 25.0 mm), JAMSTEC 0 81532. A, chela and carpus of left cheliped, outer view; B, thoracic sternum, abdomen and telson, ventral view.

FIGURE 21. Galilia petricola n. sp. A – I, holotype, male (23.8 × 25.2 mm), NSMT-Cr 22721; J, paratype, ovigerous female (22.2 × 25.0 mm), JAMSTEC 0 81532. A, left third maxilliped, outer view; B, J, telson, ventral (outer) view; C, left first gonopod, lateral view; D, same, mesial view; E, same, distal part, outer view; F, same, inner view; G, left second gonopod, lateral view; H, same, mesial view; I, same, ventral (outer) view. Scale bars: 2 mm for A – D, J; 1 mm for E – I.

FIGURE 29. Photographs in situ. A, Periclimenes sp. riding on the dorsal surface of an unidentified lophiid fish; B, three individuals of Heterocarpus laevigatus Spence Bate, 1888 and one specimen of Chaceon sp.; C, close up of one individual of Herterocarpus laevigatus. Those individuals were not collected.

FIGURE 30. Photographs in situ. A, Homeryon armarium Galil, 2000, resting on rock, ovigerous female (cl 65.0 mm), JAMSTEC 081538; B, Michelopagurus limaturus (Henderson, 1888), climbing on soft coral; C, Galilia petricola n. sp., ovigerous female (22.2 × 25.0 mm), JAMSTEC 0 81532, walking on steep slope of rock; D, Progeryon mus Ng & Guinot, 1999, male (27.2 × 34.3 mm), JAMSTEC 081539 - 1, walking on rock.