Neoferdina longibrachia, Kogure & Fujita, 2012

Kogure, Yoichi & Fujita, Yoshihisa, 2012, A new species of Neoferdina and three new records of sea stars (Echinodermata: Asteroidea) collected from Kumejima Island, southwestern Japan *, Zootaxa 3367 (1), pp. 252-260 : 255-257

Neoferdina longibrachia n. sp.

[New Japanese name: Udenaga-akamon-hitode]

( Fig. 3 )

Material examined. Holotype, one specimen, RUMF-ZE-00034, KUMEJIMA 2009 Stn. Trawl-25, 26° 16.554 –16.655 ʹN, 126° 52.714 –53.487 ʹE, 151–160 m, 12 November 2009.

Diagnosis. A species of Neoferdina with long, narrow arms; R/r exceeding 5.0. Size of superomarginal plates decreasing gradually from arm base to tip. At arm base, 3 regular longitudinal series of abactinal plates between superomarginals. Marginal plates, except for 1st inferomarginal plate, having central bare smooth surface surrounded by fine granules. Abactinal, actinal, adambulacral plates completely covered with granules. Adambulacral armature consisting of 3 short, thick, blunt furrow spines. Single papula, counting 2–4 around abactinal plate at arm base.

Description. Flattened body with 5 long, narrow arms ( Fig. 3A ). Body proportions as follows: R = 21.6 mm, r = 3.8 mm (R/r = 5.7), width of arm base between 1st and 2nd superomarginal plates 2.9 mm.

Abactinal surface composed of round or elliptical plates. All abactinal plates covered with fine granules. Abactinal plates arranged in 3 regular longitudinal series at arm base ( Fig. 3B ); carinal plates extending to 8th superomarginal plates, other outer 2 series ending at 2nd superomarginal plates.

Madreporite triangular in shape, with rounded corners, 0.8 mm wide, located interradially about half way between center of disk and disk margin.

Number of superomarginal plates, 12; inferomarginal plates, 12; all of them in contact with each other. Superomarginal plates elongated ellipse; 1st plate with following dimensions: length = 2.0 mm, width = 1.2 mm. Superomarginal plates gradually reduced in size from arm base to tip. Fine granules confined to peripheral areas of superomarginal plate; center of plate completely naked.

Inferomarginal plates elongated ellipse, approximately 2 times longer than width. All plates aligned opposite to superomarginals. First inferomarginal plate entirely covered with granules; other plates with fine granules at their bases; center of each plate lacking granules, with a smooth appearance.

Actinal plate square or rectangular in shape, with rounded corners, entirely covered with dense granules. Arrangements of actinal plates, excluding adambulacral pates, as follows: single odd plate adjacent to mouth plate; innermost series composed of 18–20 plates adjacent to adambulacrals, extending to 9th inferomarginal plate; outer 2nd series composed of 4 plates, reaching only 2nd inferomarginals; single outermost plate situated just below 1st inferomarginal plate ( Fig. 3C ).

Adambulacral plate narrow, longer than width, completely covered with granules. Adambulacral armature consisted of 3 short, thick, blunt furrow spines, arranged in one longitudinal series along ambulacral furrow ( Fig. 3D ). Adambulacral plate lacking subambulacral spines.

Mouth plate, having 5–6 marginal spines, covered with granules. Single marginal spine at proximal end conspicuous, forming paired apical spines together with adjoining proximal spine.

Terminal plate conspicuous, 1.2 mm long, 1.2 mm wide; two tiny conical projections at tip of plate.

Single papula, counting 2–4 around each abactinal plate at arm base. No papulae on actinal surface.

Etymology. The specific epithet is named for its long arms, which are the remarkable body shape characteristics that separate this species from most other Neoferdina species.

Remarks. The genus Neoferdina is known from the tropical and subtropical waters of the Indo-Pacific regions. At present, 5 species are recognized as valid member of this genus: N. cumingi ( Gray, 1840) , N. glyptodisca ( Fisher, 1913) , N. japonica Oguro & Misaki, 1986 , N. kuhli ( Müller & Troschel, 1842) , and N. offreti ( Koehler, 1910) . Among them, N. cumingi , N. japonica , and N. offreti are distributed in southern Japanese waters ( Saba & Irimura 2002).

The present species differs from the previously known Japanese species by virtue of the extremely long, narrow arms; the ratio of R to r of N. longibrachia is more than 5, whereas that of the other Japanese species is less than 4. In addition to the body shape, the arrangements of the marginal and abactinal plates are the main distinguishing characteristics. The present species is distinct from N. cumingi , based on the arrangement of the superomarginal plates, which are gradually reduced in size from the base of arm to the tip; those of N. cumingi are arranged in an alternating pattern of large, bare plates and small, granule-covered plates (A.M. Clark & Rowe 1971). Neoferdina japonica and N. offreti have no such alternating pattern of large and small superomarginals; however, in addition to the remarkable difference of the R/r value between these species and N. longibrachia , they can be distinguished from N. longibrachia by having more abactinal plates at the base of arms: N. japonica and N. offreti has 7 and 5 longitudinal series, respectively, whereas N. longibrachia has 3 series.

It is expected that the R/r value and the number of marginal plates may change in accordance with the body size. However, the original description of N. japonica , and the examination of small individuals of N. cumingi and N. offreti collected in the KUMEJIMA 2009 Expedition firmly establish the peculiarity of N. longibrachia . The body shape and the number of marginal plates of each species compared are as follows: N. japonica (R = 40–42 mm, R/r = 2.5–2.8, number of marginal plates = 11–12), N. cumingi (R = 14 mm, R/r = 2.5, number of marginal plates = 7–8), and N. offreti (R = 19 mm, R/r = 2.9, number of marginal plates = 8–9).

Two Neoferdina species , N. glyptodisca and N. kuhli have never been recorded in Japanese waters. One of them, N. glyptodisca , differs from N. longibrachia by virtue of a small R/r, which of the type specimen with R = 35 mm is 3.2 ( Fisher, 1919), as well as large, prominent, and centrally bare abactinal plates.

The other species, N. kuhli , was insufficiently described by Müller & Troschel (1842) in Germany, with little morphological information and no figures. Unfortunately the only specimen as the holotype of N. kuhli obtained from Java has been lost ( Jangoux 1973). The original description of N. kuhli indicated the body proportion of R/r = 5.0, which resembles that of N. longibrachia . However, N. kuhli clearly differs from N. longibrachia by having an irregular arrangement of abactinal plates, and large, bare abactinal plates that lack central granules ( Müller & Troschel 1842).

Figures

FIGURE 3. Neoferdina longibrachia n. sp. (RUMF-ZE-00034): A, abactinal view of entire animal in living condition; B, close-up of the abactinal surface; C, close-up of the actinal surface; D, furrow spines on the 14th–12th adambulacral plates (proximal region is on the right). Scales: A = 10 mm; B, C = 2 mm; D = 0.5 mm.