Neolithodes yaldwyni, Ahyong, Shane T. & Dawson, Elliot W., 2006

Ahyong, Shane T. & Dawson, Elliot W., 2006, Lithodidae from the Ross Sea, Antarctica, with descriptions of two new species (Crustacea: Decapoda: Anomura), Zootaxa 1303, pp. 45-68 : 46-55

Neolithodes yaldwyni sp. nov. ( Figs. 1–4 )

Neolithodes brodiei .— Thatje & Lörz, 2005: 335 –336, fig. 2A [NIWA 3433, 3434 only; not N. brodiei Dawson & Yaldwyn, 1970 ].

Not Neolithodes brodiei .— Thatje & Lörz, 2005: 335 [NIWA 3432 = Paralomis birsteini Macpherson, 1988 ].

Not Neolithodes brodiei .— Thatje & Lörz, 2005: 335 [NIWA 3435 = Paralomis stevensi sp. nov].

Type material. HOLOTYPE: NIWA 3434, male (cl 141.5 mm, cw 124.1 mm, tcl 159 mm), N of Sturge I., Balleny Is., 67°13.22–11.97’S, 164°17.78–14.87’E, 522–538 m, TAN0402/226, RV Tangaroa , 3 Mar 2004. PARATYPES: NIWA 3433, 1 male (cl 120.0 mm, cw 108.7 mm, tcl 144.0 mm), seamount W of Sturge I., Balleny Is., 67°26.09–26.37’S, 163°52.98–51.79’E, 124–170 m, TAN0402/235, RV Tangaroa , 4 Mar 2004; NMNZ CR11002, 2 males (cl 101.7–103.6, cw 91.6–95.2, tcl 124.1–131.8 mm), between Scott and Balleny Is., 67°08–06’S, 170°54–47’E, 900–1160 m, RV San Aotea II, trip 2010, haul 180, E. Winslade, 14 Feb 2005; NMNZ CR11003, 1 male (cl 136.6, cw 131.1, tcl 183.3 mm), near Scott I., 68°23–21’S, 179°53–57’E, 1337– 1050 m, RV San Aotea II, trip 2010, haul 137B, on hook, B, E. Winslade, 31 Jan 2005.

Diagnosis of adults. Carapace dorsal surface with thick, conical spines and scattered, widely separated granules or minute secondary spines; longest spine not exceeding 0.2 times carapace length. Rostrum 0.1–0.3 times carapace length; ventral surface smooth. Posterior orbital margin near vertical; outer orbital spine slender, reaching to but not beyond cornea. Scaphocerite shorter than fourth antennal segment. Major cheliped palm with prominent dorsal and lateral spines; dactylus with convex dorsal margin, slightly longer than dorsal margin of palm. Ambulatory legs spinose, secondary spines absent or sparsely distributed; meri ovate in cross­section, shorter than carapace; propodi subcylindrical in cross­section; dactyli distinctly longer than half propodal length.

Description. Carapace: Pyriform, about 1.1 times longer than wide; dorsal surface armed with thick, conical spines and scattered, widely separated granules or minute secondary spines, surface otherwise smooth; longest spine shorter than 0.2 carapace length. Gastric region bearing 6 large spines forming transverse hexagon; with 2 near transverse rows of 3 smaller spines, first across centre of hexagon and second slightly anterior to hexagon. Hepatic spine strong, anterolaterally directed; margin between outer orbital spine and hepatic spine with 2 or 3 spines. Branchial regions with 8 or 9 large dorsal spines in addition to scattered smaller secondary spines; margins with 13 large spines in addition to several smaller spines. Cardiac region with 4 equal spines of similar size to gastric spines and pair of smaller spines near intestinal region. Intestinal region with 2 upright spines in transverse row and 2 smaller posterior directed spines. Pterygostomian region spinose or tuberculate, with small distal spine.

Rostrum and orbit: Rostrum 0.1–0.3 times carapace length; median spine nearly horizontal, with pair of divergent dorsal spines and smaller pair of basal spines; ventral surface smooth. Posterior orbital margin near vertical; outer orbital spine slender, reaching to but not beyond cornea (when eyes directed forwards). Anterolateral spine about half as long as outer orbital spine.

Ocular peduncle: longer than cornea; with scattered dorsal granules or spinules. Antennule: peduncle unarmed, reaching anteriorly beyond antennal peduncle by about half­length of distal antennular peduncle segment.

Antenna: basal antennal segment with small anterolateral spine; outer margin of second segment with small basal spine and long slender spine that reaches beyond end of fourth segment but not beyond midlength; third segment with sharp to angular inner distal tooth; scaphocerite minute, shorter than fourth segment, apex sharp to blunt; fourth segment unarmed, about half as long as fifth segment.

Abdomen: Second abdominal somite with 10 long spines and several smaller spines on median plate; submedian plate with 4 or 5 long spines on posterior border and 2–4 shorter spines on surface; lateral border of lateral plates with 6–8 teeth; surface and margins of remaining segments multispinose or nodulose; telson and penultimate segment spinose.

Chelipeds: Major cheliped 1.3–1.6 times carapace length; minor cheliped 1.2–1.4 times carapace length. Coxa with blunt tubercles and tufts of setae, unarmed; ischiobasis with 4 or 5 stout ventral spines. Merus inner margin smooth or granular, with stout subdistal spine; ventral margin with two rows of stout spines, mesial row with 2 spines, lateral row with 4 spines; dorsal and lateral surface spinose, spines largest distally. Carpus with prominent spines on dorsal and lateral surfaces; dorsal margin with row of 4 or 5 stout spines; lateral margin with 2 or 3 rows of 4 or 5 stout spines of similar size to dorsal row; ventral margin small scattered acute tubercles. Upper palm length 1.1–1.2 times height (major chela), 1.3–1.4 times height (minor chela); prominently spinose on dorsal, lateral and ventral surfaces, inner surface with acute tubercles; dorsal margin with row of about 5 prominent conical spines; midlateral surface with 2 rows of 4 or 5 spines of similar size to dorsal row; ventral surface with 2 rows of about 6 or 7 spines, smaller than lateral and dorsal spines. Fingers with 2 or 3 basal spines and rows of tufts of golden setae. Fingers of major chela with occlusal margins corneous for slightly less than distal half, proximally with 3 calcareous nodules; dactylus dorsal margin convex, 1.2–1.4 times longer than dorsal margin of palm (apex broken in holotype). Fingers of minor chela with occlusal margins corneous for slightly more than distal half, proximally crenulate; dactylus dorsal margin convex, 1.5–1.8 times longer than dorsal margin of palm.

Ambulatory legs: Segments spinose, surface between major spines smooth or with few, minute, sparsely distributed spines. Third ambulatory leg longest, 2.8–3.0 times carapace length. Distal margins of coxae with short spines, longest on third coxa. Ischiobasis with 3 or 4 distal spines and 2 or 3 smaller ventral spines. Merus ovate in cross section, shorter than carapace; 5.8–7.3 times longer than high; extensor margin with 8 or 9 spines in addition to paired distal spines; dorsal surface with row of 4–6 spines of similar size to extensor spines; flexor margin with 2 rows of 5–7 spines. Carpus slightly longer than half merus length; extensor margin with 5 or 6 spines, distal and second proximal spines longest, about twice as long as other spines; dorsal surface with 4 or 5 spines. Propodus ovate to subcircular in cross­section; about 0.9 merus length, 8.9–11.9 times longer than high; with 7–9 spines on extensor margin and 8–10 similar spines on dorsal surface; flexor margin with 6–10 smaller spines. Dactylus curved, rounded in cross section, with 4–6 small proximal spines, apex corneous; exceeding 0.6 propodus length.

Colour in life. Deep red.

Etymology. Named in honour of the late John Yaldwyn, in recognition of his important contributions to New Zealand and subantarctic zoology, including the systematics of the Lithodidae .

Remarks. Neolithodes yaldwyni sp. nov. belongs to the group of species in the genus in which the carapace and ambulatory legs at most bear scattered, minute secondary spines or tubercles amongst the primary dorsal spines. These species are: N. diomedeae ( Benedict, 1895) , N. capensis Stebbing, 1905 , N. grimaldii (A. Milne Edwards & Bouvier, 1894) and N. vinogradovi Macpherson, 1988 b. Neolithodes diomedeae is distinguished from all others in the group by the shape of the cheliped fingers, which are triangular instead of rounded in cross­section and dorsally flattened or concave instead of convex. Neolithodes grimaldii and N. vinogradovi are readily distinguished from N. yaldwyni and N. capensis by the considerably longer dorsal spines in adults, many of which exceed half the carapace length. Thus, N. yaldwyni is closest to N. capensis , which it resembles in most respects. The strong resemblance between N. capensis and N. yaldwyni gave some pause to referring the latter to a new species, but the morphological differences between the two forms are consistent. Adult N. yaldwyni differ most obviously from N. capensis in the proportional lengths of the dactyli of the ambulatory legs, being distinctly more than half the propodus length (exceeding 0.6) instead of less than half (about 0.4). Although the proportional lengths of the dactyli of the ambulatory legs vary allometrically in Neolithodes , the dactyli become proportionally shorter with increasing body size. Thus, the morphometric differences in dactyl length between N. yaldwyni and N. capensis are not attributable to allometry. The largest specimen of N. yaldwyni (cl 141.5 mm) is larger than the largest reported specimen of N. capensis (cl 131 mm, Macpherson 1988b: 40) in which the dactylus measured about 0.43 propodus length (based on Macpherson 1988b: fig. 17H). Thus, proportional differences in dactyl/propodal lengths can be expected to be even greater in size­matched individuals of N. yaldwyni and N. capensis . Similar dactylar proportions (0.45) were reported by Stebbing (1905) in the type description of N. capensis , and figured for the female syntype (tcl 148 mm, cl 120 mm). Macpherson (1988b: pl. 5A) also figured an 82 mm specimen of N. capensis in which the dactyli of the ambulatory legs are half the length of their respective propodi. Thus, even at 82 mm cl, the two species are distinguishable based on the relative length of the ambulatory leg dactyli. The dactylus/ propodus proportions of the last ambulatory leg of the 65 mm specimen of N. capensis figured by Macpherson (1988b: fig. 17G) approaches that of the much larger (+ 100 mm) type specimens of N. yaldwyni , and as such, small specimens of the two species might be difficult to differentiate.

Barnard (1950) noted that the relative lengths of the cheliped fingers do not change appreciably with size in Neolithodes . Thus, N. yaldwyni may also be distinguished from N. capensis in having a proportionally longer dactylus on the major cheliped, being longer than instead of as long as or slightly shorter than the dorsal margin of the palm.

Spine development in lithodids is inversely related to body size and evident in the type series of N. yaldwyni . Even so, the overall spination of N. yaldwyni is distinctly more pronounced than in size­matched N. capensis : the dorsal carapace spines are proportionally longer (compare Fig. 1 B, 4 with Macpherson 1988b: pl. 5B) and the spines of the cheliped palm are well developed. In N. yaldwyni , the spines on the outer surface of the palm are of similar size to the dorsal spines, whereas in N. capensis , the spines on the outer palm are poorly developed and distinctly smaller than the dorsal spines.

The development of the outer orbital spine might also prove useful in separating large specimens of N. yaldwyni from N. capensis . The outer orbital spine is well­developed in all specimens of N. yaldwyni , reaching to, but not beyond the cornea (when the eyes are directed forward), whereas in the l 31 mm specimen of N. capensis reported by Macpherson (1988b), the outer orbital spine is reduced to a short triangular tooth, not reaching the midlength of the ocular peduncle. Further studies are required to assess the degree of allometric and intraspecific variation.

Aside from size­related differences, the type material is in most respects morphologically uniform. Two paratypes, however, are noteworthy: a 136.6 mm cl male (NMNZ CR11003) ( Fig. 4 B) and a 120.0 mm cl male (NIWA 3433) ( Fig. 3 E, F). Though the dorsal spine development and body size are inversely related in most specimens, spination of the 136.6 mm cl paratype is more pronounced than other specimens, including the smallest paratype (cl 101.7 mm, Fig. 4 A). The longest spine on the 136 mm cl paratype measures almost 0.2 cl in contrast to 0.1 cl in the smallest paratype. In other specimens, the carapace spines are less than 0.1 cl. Similarly, the spines on the ambulatory legs of 136 mm cl paratype are noticeably longer than in other specimens, with the length of the longest spines of the carpi and propodi exceeding, rather than at most equaling, the respective segment heights. Aside from spine length, the more spinous paratype agrees well with other specimens of N. yaldwyni . One might speculate that the more spinous paratype of N. yaldwyni represents a large specimen of N. vinogradovi Macpherson, 1988 . Aside from the much longer dorsal spines of N. vinogradovi , however, Macpherson’s species is immediately excluded by the length of the merus of the third ambulatory leg in males—longer than the carapace in N. vinogradovi ; shorter than carapace in N. yaldwyni .

The 120 mm cl paratype (NIWA 3433, Fig. 3 E, F) is unusual in the reversed asymmetry of the chelipeds whereby the left chela is larger than the right, forming the ‘crushing’ claw. The right chela is usually the larger in Lithodidae , and reversed asymmetry is perhaps a result of autotomy and replacement ( Zaklan 2000).

Though Thatje & Lörz (2005) confused N. yaldwyni with N. brodiei , the two species are readily separated. Thatje & Lörz (2005) noted the differences in secondary dorsal spinulation between typical N. brodiei and the Ross Sea specimens, which is the most obvious distinguishing feature. Secondary spinules or tubercles are only sparsely distributed on the dorsum of N. yaldwyni but densely and uniformly distributed in N. brodiei . The differences in dorsal spinulation between N. yaldwyni and N. brodiei (both as N. brodiei ) were well illustrated by Thatje & Lörz (2005: fig. 2A, B). Although the text discussion attributes the figures correctly, Thatje & Lörz’s (2005) caption for figures 2A & B were inadvertently reversed: figure 2A depicts a Balleny Island specimen (the holotype of N. yaldwyni ) and figure 2B the holotype of N. brodiei . Aside from dorsal spinulation, N. yaldwyni also differs from N. brodiei in numerous other features including the near straight and vertical instead of distinctly concave posterior orbital margin, the smooth instead of minutely spinulose ventral proximal surface of the rostrum, and the subcylindrical instead of dorsoventrally flattened propodi of the ambulatory legs. The smallest specimen reported by Thatje & Lörz (2005) as N. brodiei , a 75 mm cl ovigerous female, is referable to Paralomis birsteini Macpherson, 1988 . The fourth specimen reported Thatje & Lörz (2005), a “severely damaged” ovigerous female (NIWA 3435) is referable to Paralomis stevensi sp. nov., described below.

Presently, N. yaldwyni is known only from the vicinity of Scott Island and the Balleny Islands, Ross Sea (see Dawson 1969 for bathymetry). Neolithodes capensis has been reported from South Africa, the subantarctic (Banzare Bank, Kerguelen Islands), and Antarctica (Bellingshausen Sea) ( Macpherson 2004; García Raso et al. 2005). In view of the strong similarities between N. yaldwyni and N. capensis, the Antarctic and subantarctic records of N. capensis require verification.

Distribution. Presently known only from the Ross Sea, Antarctica; 124–1337 m.

Figures

FIGURE 1. Neolithodes yaldwyni sp. nov., male holotype (cl 141.5 mm, cw 124.1 mm, NIWA 3434). A, overall dorsal view. B, carapace, dorsal view. C, anterior carapace, right lateral view.

FIGURE 2. Neolithodes yaldwyni sp. nov., male holotype (cl 141.5 mm, cw 124.1 mm, NIWA 3434). A, carapace, right lateral view. B, left antenna, dorsal view. C, ventral surface. D, posterior carapace and abdomen, posterior view. E, coxa and basis of left third ambulatory leg, ventral view. F, rostrum and anterior carapace, dorsal view.

FIGURE 3. Neolithodes yaldwyni sp. nov. A – D, male holotype (cl 141.5 mm, cw 124.1 mm, NIWA 3434). E – F, male paratype (cl 120.0 mm, cw 108.7 mm, NIWA 3433). A, left cheliped, dorsal view. B, left chela, outer surface. C, right cheliped, dorsal view. D, right chela, outer surface. E, left chela, outer surface. F, right chela, outer surface.

FIGURE 4. Neolithodes yaldwyni sp. nov., overall view, dorsal. A, male paratype (cl 101.7 mm, cw 91.6 mm, NMNZ CR 11002). B, male paratype (cl 136.6 mm, cw 131.1 mm, NMNZ CR 11003).