Henricia irregularis Hayashi, 1940

Ubagan, Michael Dadole, Lee, Jinho & Lee, Sook Shin and Taekjun, 2023, Two newly recorded echinoderms from the mesophotic zone in Korea, Journal of Species Research 12 (2), pp. 180-188 : 181-182

Henricia irregularis Hayashi, 1940 ( Figs. 1-3 )

ḆRṆOinjḆḦĤH (ṳffi)

Henricia irregularis Hayashi, 1940: 164 .

Material examined. One specimen, adjacent water of Jumunjin : Gangneung-si : Gangwon-do , Korea (37°52 ʹ 13 ʺ N, 128°58 ʹ 11 ʺ E), February 27, 2018, Lee T., a depth of 85 m, collected with a fishing net, deposited in the National Marine Biodiversity Institute of Korea ( MABIK; MABIK _ IV00172917 ) ( Fig. 1 ) .

Description. Arms five, long, flexible, gradually tapering to tips (R = 202 mm). Disk small (R = 5.8r) ( Fig. 2 ). Abactinal skeleton weakly reticulated structure with narrow meshes ( Fig. 3A, 3B ). Abactinal plate small, low, rod-like shape with one or two well discernible tubercles, with ambiguous series. Abactinal paxillae small, com- posed eight to ten spines. Abactinal papular areas narrow, with one or two papulae in an area, irregular in shape, and subdivided by small ossicles. Madreporite circular, slightly convex, near center of disk, containing scattered spines like those found on adjacent spines. Superomarginal plates elongated cross shape, with rows extending near middle of arm and gradually bending upward toward base. Intermarginal plates rod- or lobe-shape, not in regular series, with a narrow papular area and a single papula in each area; intermarginal areas spacious. Inferomarginal plates crescent-shaped, not forming a regular series. Ventrolateral plates rounded and some slightly elongated shape, larger than adjacent plates, not in regular series. Adambulacral plates elongated cross shape, covered with 13-20 slender spines with blunt tips and arranged trans- versely in three uneven rows ( Fig. 3D ). Furrow spines double ( Fig. 3C, 3D ). Two oral spines with spatulate tip, three marginal spines, four or five sub-oral spines in oral part ( Fig. 3C ).

Habitat. This species was collected at a depth of 85 meters. It is likely to inhabit the mixed substrate (coarse sand and rocks), based on other echinoderms collected in the same area.

Distribution. Korea (Jumunjin: the East Sea), Japan (Yezo

Strait: Hokkaido).

Remarks. Henricia irregularis is similar in appearance to H. sanguinolenta Fisher, 1911 . Specifically, both species have long arms and a small disk, and their abactinal plates are characterized by narrow meshes. Some morphological differences are the following: 1) abactinal skeleton structure ( H. irregularis : weak; H. sanguinolenta : stout); 2) number of abactinal spines ( H. irregularis : 8-10; H. sanguinolenta : 7-16); 3) number of abactinal papulae ( H. irregularis : 1 or 2; H. sanguinolenta : 1-5); 4) actinal plate series of superomarginal, inferomarginal, ventrolateral ( H. irregularis : irregular series; H. sanguinolenta : regular series).

Our specimen has slightly different morphological characteristics from the holotype specimen in Hayashi (1940). Hayashi (1940) described the abactinal plate of H. irregularis as elongated with a plain appearance, while our specimen shows elongated plates with tubercles. Nev- ertheless, the major key features in our specimen match a description of Hayashi about the holotype. We conclude that our specimen belongs to the species H. irregularis , based on its observed morphological features, which match those of the description of holotype.

Figures

Fig. 1. Distribution of Henricia irregularis Hayashi, 1940 based on the present and previous study.

Fig. 2. Abactinal and actinal side of Henricia irregularis Hayashi, 1940 in this study.

Fig. 3. Henricia irregularis Hayashi, 1940 in this study. (A) abactinal paxillae; (B) abactinal skeleton; (C) papulae (arrows); (D) madrepo- rite; (E) actinal skeleton; (F), (I) adambulacral spines; (G) oral part and interradii of actinal side;(H) abactinal spines. Scale bars: A-E=1 mm, F=5 mm, G=3 mm, H=100 μm, I=200 μm (H, I, SEM images). Abbreviations: a, adambulacral plates; i, inferomarginal plates; in, intermarginal plates; s, superomarginal plates; v, ventrolateral plates.