Sakaila wanawana, Martin & Godwin & Moffitt, 2009

Martin, Joel W., Godwin, Scott & Moffitt, Robert, 2009, Additions to the decapod crustacean fauna of the Hawaiian Islands, I. A review of the genus Sakaila Manning and Holthuis, 1981 (Decapoda, Brachyura, Aethridae), with the description of a new species from the Northwestern Hawaiian Islands, Zootaxa 2018, pp. 25-44 : 27-38

Sakaila wanawana sp. nov.

( Figs. 1–5, 6A–C)

Material. Hawaiian Islands, NWI, French Frigate Shoals: one female, CL = 56.4 mm, CW = 73.4 mm, 247–274 m depth, Oscar Elton Sette, FFS "event" number 129, site DRS 10, Bait 3, lobster trap, 23° 45.72 N 166° 00.844 W, 10 October 2006, field specimen number JM0175 , JWM photograph numbers 994–1014. Holotype: LACM CR 2006 – 014.20 .

Hawaiian Islands, NWI, Maro Reef: one male, CL = 43.0 mm, CW = 55.6 mm, 66–100 fathoms (121 – 183 m) depth, NMFS REF C–0167, Townsend Cromwell, Cruise 95–01, Station 99, lobster trap, 25° 17.12' N, 170° 39.12' W, 4 July 1995. Paratype: LACM CR 1995 – 165.1 .

Johnston Atoll, one male, CL = 59.3 mm mm, CW = 86.2 mm, 367 m, HURL (Hawaii Undersea Research Lab) Dive 206, 21 October 1983, coll. L. Eldredge. Paratype: ZRC 2008.0555 .

Diagnosis. Large, heavy carapace, covered dorsally and bordered on all sides by short spines or tubercles; no region of carapace lacking tubercles. Regions of carapace indistinct in dorsal view due to covering spination; 8 protuberances (bosses) also indistinct in dorsal view. Lateral, posterolateral emarginations (lobes) of carapace similarly indistinct. Protogastric regions greatly inflated in frontal view, extending dorsally further than (higher than) any other part of carapace; more lateral branchial regions also enlarged but not extending as high as protogastric regions. Front of carapace thick, strongly bilobed in dorsal view. Lateral margins of carapace forming distinct, sharp border covered by sharp spinules anteriorly and posteriorly. Chelae bearing large, acute spines on dorsal, ventral borders of cheliped fingers, with strongest (in width and height) spine on propodus just proximal to articulation with dactylus; smaller, less acute spines arising from outer face of chela bearing no reticulated pattern; fingers meeting closely in tight "zig zag" line, not gaping. All cheliped articles strongly cristate; articles except carpus bearing sharp, dorsally-directed spines. Pereopods covered with small, sharp spinules, especially prominent along dorsal border. Pereopod merus strongly triangular in cross section. Efferent branchial chambers clearly separated; third maxilliped merus with distinct notch near medial border.

Description. Carapace: Broadly, irregularly oval, with strongly protruding, markedly bilobed front; front with deep median fissure visible in frontal and dorsal views. Entire carapace densely covered with minute rounded tubercles, some acute, spine-like, especially toward lateral borders; no dorsal region of carapace smooth. Protograstric regions greatly swollen, extending dorsally further (higher) than any other region; in frontal view ( Fig. 2A, 4A) extending approximately twice as high as more lateral anterobranchial regions. Protogastric, anterobranchial regions connected by high ridge. Lateral lobes of carapace indistinct.

Eyestalks: Extremely short, broad, recessed within orbits, sloping downward with slight bend at approximate midlength; pigment restricted to upper (dorsal), distal surfaces; eyestalks not visible in dorsal view.

Antennae: Antennular peduncle short, rounded, set deeply within well defined pocket; antennular palp folded obliquely between peduncle and wall of pocket. Antennal peduncle very short, not reaching lateral extremity of antennular peduncle or upper margin of eyestalk; palp minute.

Buccal frame terminating anteriorly in truncate margin rather than acutely, with widely spaced, obvious efferent branchial openings. Epistome terminating anteriorly in broad triangle, not quite reaching dorsal extent of antennular peduncle.

Third maxillipeds ( Fig. 5B) covered externally with small tubercles; merus, basis with very straight medial borders; merus somewhat quadrate; exopod fitting tightly against lateral borders of merus, basis. Efferent branchial chambers clearly separated; merus with distinct notch located near medial border. Ischium with deep longitudinal slightly oblique groove.

Chelipeds: Fingers meeting in tight, zig zag border; both fingers nearly straight, acutely tipped. Dactylus with row of 3–4 sharp, dorsally directed spines, decreasing in length distally. Propodus with series of 5–7 strong, sharp spines along ventral border, directed ventrally. Propodus with series of flange-like spines on dorsal border, distalmost (just proximal to articulation with dactylus) by far widest, highest ( Fig. 4B). Inner surface of this spine-flange flat, slightly curved, continuing row from dorsal teeth of dactylus, oppressed against pterygostomial region of carapace. Inner surface of propodus (palm or hand) with longitudinal row of 4–5 sharp teeth directed inward, located at about 1/3 height of inner palm. Merus with 3 strong, sharp spines on ventral border. All articles heavily tuberculated. Right chela of holotype female: dactylus length 20.9 mm, palm height (from distal tip of largest spine on dorsal margin to tip of longest spine along ventral margin of hand) 23.7 mm; propodus length (measured along bottom margin from tip of finger to posteroventral bosse) 34.0 mm.

Ambulatory legs: Decreasing in length from P2 through P5. Merus by far longest article in all legs. Tubercles sharp, spine-like, most noticeably on dactylus, propodus, carpus of all legs. Measurements of articles (maximum length) of right pereopod 2 of holotype: dactylus 12.2 mm, propodus 11.5 mm, carpus 10.8 mm, merus 22.7 mm.

Abdomen and sternum: Six free (unfused) somites in both sexes; female abdomen widest at proximal border of somite 6, base of telson (equal widths); somites increasing in length, width posteriorly, telson longer than any preceding somite. All segments, telson highly ornamented, covered with tubercles. Telson broadly rounded distally but with tip protruding just slightly beyond distal curve in both sexes.

Vulva: Female vulva sternal, oval, located near anterior border of P3 sternite; vulva not covered by flap or process, covered by abdomen when closed.

Male pleopods (gonopods): First pleopod ( Fig. 6A, B) large, stout, slightly curved, with scattered, short setae and small distal spinules on approximate distal 1/8; spinules located mostly on side of pleopod opposite the wide, longitudinal groove traversing length of pleopod. Small, subdistal flap or bend of cuticle at approximate 7/8 length of pleopod slightly narrowing aperture of longitudinal groove. Second pleopod ( Fig. 6C) relatively simple, curving smoothly without interruption from base to tip, bearing small setae, spinules; tip minutely spinose.

Male openings coxal.

Coloration: The single known live specimen (the holotype female) was a splotchy mixture of reddish brown and tan or beige, becoming lighter on the tips of the spines and legs ( Fig. 1A, B). The teeth and fingers of the chelae were light beige to almost white, with distinctive vertical bars of reddish orange near the fingertips ( Fig. 2B). The underside of the carapace was light brown with scattered reddish orange spots. The pereopods approximately matched the carapace in coloration. The coloration fades rapidly; the female specimen described above faded within several months (by April, 2007) to the same light beige color as the long-preserved and smaller male specimen from Maro Reef and the larger male from Johnston Atoll.

Sexual dimorphism: Apart from their sizes (the holotype female is more than 1.3 times larger than the Maro Reef male in both CW and CL; her length is more than the male's width) and the male pleopods (gonopods), the two specimens differ in that overall spination of the smaller male is less noticeable than on the larger female. The larger male from Johnston Atoll is more similar to the holotype female. The male abdomen is narrower than that of the female, as is true for most crabs .

Etymology. From wanawana, Hawaiian for “spiny,” in reference to the spinose nature of the carapace, especially its borders, and of the pereopods.

Distribution. Known only from French Frigate Shoals (type locality) and Maro Reef, both part of the Northwestern Hawaiian Islands chain; depths of 121–274 m, and from Johnston Atoll (approximately 1400 km west of Hawaii, 16° 45' N, 169° 31' W), 367 m. This report is the first record of the genus from any of the Hawaiian Islands and only the third record of any species of Sakaila in the Pacific Ocean.

Remarks. In their revision of the genus Osachila and establishment of Sakaila, Manning and Holthuis (1981) recognized morphological differences, first pointed out by T. Sakai, and also indicated by Guinot (1966, 1967), that distinguish the western Pacific and eastern Atlantic species of Sakaila from species of Osachila . These differences include the position of the orbits (scarcely or not at all visible in dorsal view in Sakaila ; visible in dorsal view in Osachila ), the distinctly separated efferent branchial chambers in Sakaila (efferent chambers approximated in Osachila ), the merus of the third maxilliped being shorter than the ischium and notched anteriorly in Sakaila (not shorter than ischium and not noticeably notched in Osachila ), and the spined or tuberculate walking legs in Sakaila (vs. smooth or at most rugose in Osachila ) (see Manning and Holthuis, 1981: 325). Manning and Holthuis unfortunately reversed the merus and the ischium in their remarks section. Sakaila wanawana conforms well to the original description of the genus Sakaila by Manning and Holthuis (1981). The orbits are essentially hidden from above ( Fig. 1A), the efferent branchial chambers are widely separated (visible in Figs. 2A, 4A), all ambulatory legs (P2–5) are covered with spines or tubercles ( Fig. 1A, B, 5C), and the third maxilliped bears a merus that is clearly shorter than the ischium and is slightly notched on the anterior medial border ( Figs. 3B, 5B, male). The new species can be distinguished from all of its congeners by the high degree of spination on the dorsal regions of the carapace and on the pereopods, more so than could be explained by its significantly larger size alone. Further comparisons with all other species of the genus are given below.

Sakai (1963: 225) described S. japonica (as O. japonica ) as "apparently the largest of all known species of this genus." This is noteworthy considering that the genus Osachila at that time contained all of the tropical eastern Pacific American and Atlantic species in addition to the Pacific and Atlantic species now belonging to Sakaila . Sakai's largest specimen of S. japonica was the holotype (stated to be a female but now known to be a male) measuring CL 39 mm and CW 51 mm. In contrast, the smallest of the three specimens of our new species is larger than this; the Maro Reef male measuring CW 55.6 mm. The female holotype is CW 73.4 mm, and the Johnston Atoll specimen is larger still (CW 86.2 mm), making the new species by far the largest species of Sakaila and to our knowledge larger than any known species of Osachila . Thus, size alone could be used as a somewhat weak argument for the separate status of S. japonica and S. wanawana .

The morphology of the male first pleopod is known for only one of the other species of Sakaila , S. africana . The gonopods of this species were illustrated by Guinot (1967, figs. 32, 33; as Osachila stimpsoni ; see Manning and Holthuis, 1981: 325 for synonymy) based on a specimen from Senegal. Those figures are repeated here as Figs. 6D, E. Although similar in the overall appearance, there are some potentially important differences between Guinot's figures of the gonopods of S. africana and those of the smaller (Maro Reef) specimen of S. wanawana . The first gonopod in both species is large and stout and slightly curved, and it bears scattered short setae and small distal spinules on approximately the distal 1/8 of the gonopod. These spinules are found mostly on the side of the pleopod that is opposite from the longitudinal groove. Also located at approximately 1/8 of the length of the pleopod is a small, subdistal flap of cuticle that serves to somehow close or narrow the aperture of the longitudinal groove; this closure appears much more complete in S. africana based on Guinot's figures. In the second male pleopod, in S. africana there is a distinct and spinose separation between a proximal and distal portion at approximately 2/3 of its length (seen also in many other species of brachyuran crabs), at which point the curvature of the pleopod gonopod slightly changes direction. This is also seen in the larger ( Johnston Atoll) male specimen of S. wananwana , although not in the smaller male from Maro Reef (shown in Fig. 6C), a point worth noting because the size of this species could lead one to think that the smaller male is mature, when in fact, based on this character, it is not yet fully developed. In the immature Maro Reef male, there is no separation between the two portions, and the second pleopod instead curves smoothly without interruption from proximal portion to tip [apex] ( Fig. 6C).