Journal 
1. INTRODUCTION
Genus Henricia Gray, 1840, belonging to the family Echinasteridae (Asteroidea, Spinulosida), is widely distributed and abundant, particularly in the Arctic, Atlantic, and Pacific Oceans. Despite this extensive distribution, their systematics remain poorly developed, as noted in numerous studies (Verrill 1909;Fisher 1911;Djakonov 1961;Clark and Downey 1992;Clark and Jewett 2010). Some of the widely distributed Henricia species include Henricia leviuscula Stimpson, 1857, Henricia sanguinolenta (O.F. Müller, 1776), and Henricia tumidaVerrill, 1909.
In some cases, the distribution of Henricia species, such as Henricia exiguaHayashi, 1940, is restricted to specific geographical locations. Several factors contribute to this limited distribution. Environmental conditions play a crucial role; specific factors such as water temperature, salinity, depth, and ocean currents can determine where a species can thrive (Witman and Dayton 2001;Pineda et al. 2007). For instance, some Henricia species are adapted to the colder waters of the Arctic, while others are found in the warmer waters of the Atlantic or Pacific (Hayashi 1940;Djakonov 1961;Clark and Downey 1992;Clark and Jewett 2010). Additionally, biological interactions, including those with predators, prey, and competitors, significantly influence the distribution of Henricia species. The presence or absence of these interactions can create conditions that are either favorable or unfavorable for particular species (Dayton 1971). Furthermore, human activities such as shipping, fishing, and climate change impact marine species’ distribution (Halpern et al. 2008;Molnar et al. 2008).
In Korea, research on Henricia has documented a rich diversity of species, with 23 species recorded to date, including the newly reported species in this study. In neighboring countries, Japan has identified 18 Henricia species, and China has documented 8 species. This regional comparison highlights Korea’s relatively high diversity of Henricia species, suggesting potential ecological or environmental factors unique to Korean waters that may support a greater variety of these echinoderms (Hayashi 1940;Shin 2010;Xiao et al. 2011).
In this study, we introduce two distinct species from two coastal regions of Korea, specifically the East Sea and Jeju. These species, previously identified as Henricia exiguaHayashi, 1940, and Henricia tumidaVerrill, 1909, are newly recorded for the Korean fauna.
2. MATERIALS AND METHODS
Asteroid specimens were collected using a fishing net from the adjacent waters of Dongsan Harbor (East Sea) on 6 Jun 2009 at a depth of 25 m, and waters near Chujado (Jeju) on 30 Apr 2014 at a depth of 40 m, respectively. These specimens were preserved in 95% ethanol, and their morphological characteristics were examined, such as the size of the disk, the upper and proximal portions of the arms, the number of abactinal spines, the shape of the abactinal and actinal skeletons, and the number of adambulacral spines. The body shape of Henricia specimens were distinguished by the proportion of the disk and the arm, and is expressed at the rate of R/r. R is the length of radius from the center of the disk to the tip of arm, and r is the length of interradius from the center to the margin of the disk (Shin 2010). The morphological features of the specimen were photographed by using a scanning electron microscope (JSM- 6510; JEOL Ltd., Tokyo, Japan), a stereomicroscope (Nikon SMZ1000; Nikon Co., Tokyo, Japan), and a digital camera (Nikon D7000). The abbreviations for the measurements were those used by Shin (2010) and Ubagan et al. (2023).
3. SYSTEMATIC ACCOUNTS
Phylum Echinodermata Klein, 1778
Class Asteroidea de Blainville, 1830
Order Spinulosida Perrier, 1884
Family Echinasteridae Verrill, 1870
Genus Henricia Gray, 1840
Henricia exiguaHayashi, 1940
Henricia exiguaHayashi, 1940: 138; Xiao et al., 2011: 8; Mah, 2024a: 369108.
Material examined. One specimen, Dongsan: Gangwon- do, Korea (37°58ʹ45.45ʺN 128°45ʹ47.555ʺE), 6 June 2009, Shin S., collected by fishing nets, deposited in the National Institute of Biological Resources (NIBR; NIBR_ OBMVIV0000001442).
Description. Arms five, short, slender, tapering to tips; disc small (Fig. 1A, B). Abactinal paxillae clustered, containing more than five to 15 abactinal spinelets with uneven apical thorns (Fig. 1C, J). Papular areas narrow with irregular shapes, containing one to three papulae in an area (Fig. 1H). Denuded abactinal skeleton closed meshed, imbricated, comprised of lobes, rounded crossshaped, with size larger than papular areas, and arranged irregularly (Fig. 1G). Madreporite small, situated near margin of disk, semi-circular in form, and bearing spines similar as adjacent spines (Fig. 1F). Denuded actinal skeleton showing series of plates (superomarginal, inferomarginal, ventrolateral) slightly diverging near arm base. Superomarginal slightly smaller size than inferomarginal plates, forming reniform plates, reaching tip of arm. Inferomarginal plates imbricated, elongated crossshaped, reaching tip of arm. Ventrolateral plates rounded cross-shaped showing smaller size to adjacent plates; narrow papular areas with one or two papulae (Fig. 1I). Adambulacral armature composed of 10-13 spinelets, inner two or three longer, pointed tip, arranged in transverse rows (Fig. 1D, K). Oral plate bearing two stout tip spines, five sub-oral spines (Fig. 1E). Furrow spine single.
Size. R=25 mm, r=6 mm, R/r=4.1.
Distribution. Korea (East Sea); Japan (Ise Bay, Goto Islands); China (East China Sea).
Remarks. We collected a slender-armed Henricia specimen from the East Sea, compared with other slenderarmed Henricia species, such as Henricia regularis Hayashi, 1940. The key differences between our specimen identified as Henricia exigua and H. regularis are as follows: (1) number of abactinal spinelets (our specimen: 5-15; H. regularis: 10-25); (2) arrangement of abactinal plates (our specimen: closely crowded in varying shapes; H. regularis: regularly arranged in oblique transverse rows). When comparing our specimen to the holotype, we observed that most of the morphological characteristics closely align with Hayashi’s (1940) original description specifically the arrangement of abactinal plates (irregular). However, slight differences were noted in two specific areas: 1) adambulacral spines (our specimens: 10-13, holotype: 13-15); 2) and furrow spines (our specimen: single, holotype: double). These minor morphological variations are not significant enough to justify the classification of our specimen as a separate species (Bratova and Paskerova 2017).
Henricia tumidaVerrill, 1909
Henricia tumidaVerrill, 1909: 554; 1914: 234; Hayashi, 1940: 149; Mah, 2024b: 369147.
Henricia sanguinolenta eschrichtiiFisher, 1911: 276.
Henricia tumida borealis Verrill, 1914: 236.
Henricia sanguinolenta forma tumida Fisher, 1930: 194.
Material examined. Two specimens, Chuja-do: Jeju, Korea (33°56ʹ19.41ʺN 126°19ʹ53.89ʺE), 30 Apr. 2014, Shin S., collected by fishing nets, deposited in the National Institute of Biological Resources (NIBR; NIBR_ OBMVIV0000001443).
Description. Arms five, short, slender, subcylindrical, tapering to tips; disc small (Fig. 2A, B). Abactinal paxillae scattered, containing four to eight abactinal spinelets with rapidly tapering to tip (Fig. 2C, J). Papular areas narrow with irregular shapes, containing one or two papulae in an area (Fig. 2H). Denuded abactinal skeleton closed meshed, imbricated, comprised of rounded cross-shaped, with few elongated cross shaped, size larger than surrounding papular areas (Fig. 2G). Madreporite sunken, situated near margin of disk, small, semicircular in form, and bearing spines similar as adjacent spines (Fig. 2F). Denuded actinal skeleton showing three series of plates (superomarginal, intermarginal, ventrolateral) which slighty diverging near arm base, leaving intermarginal plates spaces. Superomarginal slightly larger size than intermarginal plates, forming elongated cross, reaching tip of arm. Intermarginal plates wide spaces near basal arm, extending threeforth length of arm. Ventrolateral plates rounded crossshaped showing larger size to superomarginal plates; narrow papular areas with one or two papulae (Fig. 2I). Adambulacral armature composed of four to six spinelets, inner spinelet longer, bluntly pointed tip, arranged in transverse rows (Fig. 2D, K). Oral plate bearing two stout tip spines, six sub-oral spines (Fig. 2E). Furrow spine single, double distally.
Size. R=42-44 mm, r=10-11 mm, R/r=4.0-4.2.
Distribution. Korea (Jeju); Japan (Akkeshi); Russia (Kamchatka, Sea of Okhotsk, Kurile Islands); Bering Strait; Arctic Ocean; Alaska; Aleutian Islands.
Remarks. We conducted a detailed morphological analysis of the two short-armed specimens from Jeju Chuja-do. Our investigation included a comparative study with closely related short-armed Henricia species, specifically Henricia kinkasanaHayashi, 1940, and Henricia nipponica Uchida, 1928. Two key morphological differences were identified: (1) our specimen possesses fewer abactinal spines, and (2) it has a fewer number of adambulacral spines (Table 1). Although the size of our specimens falls within the range of the aforementioned congeners, it is best regarded as a distinct species rather than a variety of the related Henricia species (H. kinkasana and H. nipponica). The characteristics of our specimen closely align with Hayashi’s (1940) description of H. tumida, which he classified as an aberrant form of the species. Hayashi’s thorough examination of shortarmed specimens from both Akkeshi and Aleutian Islands on shore led him to conclude that there were no significant differences between these Henricia specimens. The fact that the characteristics of our specimens are comparable to Hayashi’s description suggest that they are determined to be valid.
