A New Kelp Crab Species of the Genus Pugettia (Crustacea: Decapoda: Brachyura: Epialtidae) from Shandong Peninsula, Northeast China

1 International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, 1-19-8 Akahama, Otsuchi-cho, Iwate 028-1102, Japan E-mail: ohtsuchi@g.ecc.u-tokyo.ac.jp 2 Department of Zoology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan 3 Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China 4 Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China 5 University of Chinese Academy of Sciences, Beijing, China 6 Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, China 7 Corresponding author

Recently, a taxonomic revision of P. quadridens (De Haan, 1837) and P. intermedia Sakai, 1938 by the first author resulted in P. ferox Ohtsuchi and Kawamura, 2019 being found. The authors also revisited many previous studies in the East Asian waters, and clarified the historical confusion regarding P. quadridens not only in relation to congeners, but also to various species of different majoid genera (Ohtsuchi and Kawamura 2019).
In Chinese waters, Pugettia is represented by five species: P. ferox, P. incisa (De Haan, 1837), P. intermedia, P. marissinica Takeda and Miyake, 1972, and P. quadridens (Griffin and Tranter 1986;Ohtsuchi and Kawamura 2019). Our reexamination of the Pugettia specimens preserved in the Institute of Oceanography, Chinese Academy of Science, Qingdao (IOCAS) resulted in the finding of another Pugettia species, which cannot be identified with any known species of this genus. In this paper, we describe and illustrate this species as a new species, and provide a taxonomic key to all the shallow water Pugettia species distributed in East Asian waters.

Materials and Methods
The newly examined specimens in this study are deposited in the IOCAS. The morphological terms and abbreviations essentially follow Davie et al. (2015) and Ohtsuchi and Kawamura (2019): CW, maximum carapace width excluding epibranchial spines; ChH, maximum chela height; ChL, maximum chela length (along lower margin); PCL, maximum carapace length excluding pseudorostral spines; HpL/PoL, hepatic lobe length/postorbital lobe length ratio; PRL, pseudorostral spine length; PW3, PW6, pleon width at proximal margin of pleomeres 3, 6, respectively. Other abbreviations used in the text: P1-5, the first to fifth pereiopods (the cheliped and the first to fourth ambulatory legs), respectively; G1 and G2, the first and second gonopods, respectively. The terms used to identify the growth phase of each specimen follows the concept of "ontogenetic stages" (cf. Ohtsuchi and Kawamura 2019).
All the measurements were made by referring to Ohtsu-chi and Kawamura (2019), using digital vernier calipers to 0.1 mm, and are given as mean with standard deviation. All the statistical analyses were performed using R version 3.5.1. (R Core Team 2018) to test both intra-and interspecific morphometric differences. For comparative purposes, the following specimens deposited in the National Museum of Nature and Science, Tokyo (NSMT), Natural History Museum and Institute, Chiba (CBM), and Ryukyu University Museum, Fujukan (RUMF), and University of the Ryukyus were examined. Description. Male. Full-grown specimens (PCL 12.9-17.6 mm, n=3). Carapace (Fig. 1A) pyriform, 1.4 longer than width (mean PCL/CW±SD=1.4±0.0); surface smooth to naked eyes but closely covered with microscopic, apically flattened setae; gastric, cardiac, branchial, intestinal regions unclearly separated from each other. Gastric region ( Fig. 2A) moderately elevated, sometimes anteriorly with short, oblique row of hooked setae on either side of midline (Figs 1A, 2A; mostly abraded in holotype); mesogastric, metagastric, both protogastric regions each with rudimentary protuberance (protogastric ones much closer to mesogastric one than to metagastric one) (Fig. 1A). Cardiac, branchial regions (Figs 1A, 2A) moderately elevated; mesobranchial region weakly elevated, never higher than gastric region ( Fig. 2A), with two rudimentally tubercles apically (lateral one larger than mesial one); metabranchial region faintly elevated, with low protuberance medially. Intestinal region (  Subhepatic region (Figs 1B, 2A) without sparse, hooked setae. Pterygostomial region not prominently inflated, with four papiliform tubercles along pleural suture. Anterolateral angle of buccal frame ( Fig. 2A) subrectangular, produced anteriorly, not overlapped by anterolateral angle of third maxilliped merus when closed.
Remarks. The present new species closely resembles Pugettia ferox and P. quadridens. Shared characters with P. ferox include: acute, triangular preorbital spine as long as postorbital lobe; sinuous lateral margin of supraorbital eave; orbital hiatus appeared as broad concavity; shallow concavity on lateral margin between postorbital and hepatic lobes; basal antennal article clearly separated from suborbital region by basal protrusion on lateral margin; small, lobular projection at basis of G1 dorsal lobe (cf. Ohtsuchi and Kawamura 2019: figs 28 A, 33A-G). Pugettia longipes n. sp. and P. quadridens shares the following features: smooth carapace surface covered with microscopic, apically-flattened setae; rows or groups of hooked setae on carapace which can be absent in male specimens; rudimentary tuberculation on gastric, branchial regions; long, broad, basally inflated hepatic lobe; secondary sexual difference in the relative length of pseudorostral spines (only in the full-grown stage) (cf. Ohtsuchi and Kawamura 2019: figs 2-13). However, these species can be distinguished from each other by the morphological differences discussed below. The pseudorostrum is more divergent in P. longipes n. sp. (divergent angle=45-60°) than in P. ferox and P. quadridens (30-40°) at least when compared among full-grown individuals ( Fig. 3; cf. Ohtsuchi and Kawamura 2019: figs 3A, B, D, E, 26 A, 34A, 37A, C, F, G).
The anterolateral margin of gastric region is poorly defined, and the slope from protogastric region to hepatic lobe tip is almost straight in males of P. longipes n. sp. (Fig.  3A). On the other hand, the anterolateral margin of gastric region weakly demarcated, and the slope is shallowly concave or weakly sinuous in both males and females of P. quadridens and P. ferox (Fig. 3B, C). This character is unique to P. longipes n. sp. among all the extant western Pacific Pugettia.
The supraorbital eave is deeply demarcated from the frontal region by a groove in P. longipes n. sp. (Figs 3A, 4A), whereas it is not markedly demarcated in P. quadridens and P. ferox (Fig. 3B, C).
The relative length of the hepatic lobe (HpL/PoL) in P. longipes n. sp. shows different growth tendencies from that of P. quadridens and P. ferox (Fig. 12), but we can also see that HpL/PoL cannot fully distinguish P. longipes n. sp. from the other two species because of potentially wide overlap.
The lateral margin of the basal antennal article being clearly separated from the suborbital region at the basis distinguishes P. longipes n. sp. and P. ferox from P. quadridens, in which the article is confluent to the suborbital region ( Fig. 4B versus Ohtsuchi and Kawamura 2019: figs 4B, 28B). The basal protrusion of the lateral margin of P. longipes n. sp. resembles that of P. ferox. However, in the present new species, the protrusion is rounded (Fig. 4B) and never pointed as seen in large specimens of P. ferox (Ohtsuchi and Kawamura 2019: fig. 28B).
The patterns of morphometric and morphological change of male chelae differ among these three species. The ChL/ ChH of P. longipes n. sp. changes from 2.8 (median) in adolescents to 2.4±0.1 (mean±SD) in full-grown males, and this pattern resembles P. ferox, in which ChL/ChH changes from 2.8±0.0 in adolescents to 2.3±0.1 in full-grown males (Ohtsuchi and Kawamura 2019: table 1). On the other hand, the chelae of P. quadridens is relatively shorter than in P. longipes n. sp. and P. ferox at all ontogenetic stages: the ChL/ ChH changes from 2.4±0.0 in adolescent males to 2.0±0.0 in full-grown males (Ohtsuchi and Kawamura 2019: table  1). In addition, P. longipes n. sp. differed in the chelae dentition from both of the other two species when compared among full-grown males, although the chela of adolescent males are similar in general shape and dentition on both fingers: the chela has a narrow gap when both fingers are closed, and the movable finger is uniformly dentate in P. longipes n. sp. (Fig. 7A). In P. quadridens, the chela is widely gaped, and the movable finger bears a group of two or three, large, isolated teeth on the proximal one-third (Fig. 7G) and has narrow gaps, and the movable finger bears no peculiar teeth in P. ferox (Fig. 7D).
The tri-dentate longitudinal ridge on the dorsal surface of the cheliped merus is more lamellar in P. longipes n. sp. (Fig. 6F) than in the other two species (cf. Ohtsuchi and Kawamura 2019: figs 5E, 29E). The distalmost tooth is mod- erately high and acuminate in P. longipes n. sp. and P. ferox, but it is low and blunt in P. quadridens. However, this character should be used with caution because it is often rudimentary in small, immature specimens in P. quadridens and P. ferox (Ohtsuchi and Kawamura 2019).
In each ambulatory leg, the relative length of the merus compared to PCL is greater in P. longipes n. sp. than in the other two species when compared among the same ontogenetic stages (Tukey-Kramer HSD test, p<0.05) (Fig. 13). All the ambulatory legs have meri that are much more slender in P. longipes n. sp. than in the other two species (Table 1). For example, the P2 merus is much more slender in P. longipes n. sp. (mean length/height±SD: 7.9±0.3) than in the other two species (5.7±0.3 in P. quadridens; 6.3±0.9 in P. ferox; Tukey-Kramer HSD test, p<0.05) (Fig. 8).
The absence of a small, lobular projection at the G1 dorsal lobe basis, and the elevation of the lateral margin of G1 apex (higher than mesial margin), distinguish P. quadridens from both P. longipes n. sp. and P. ferox (Fig. 9). In the latter two species, the mesial margin of the G1 apex is continuous to the upper margin of the ventral lobe (Fig. 9A), but it is distinct in P. ferox (Fig. 9C). See also Ohtsuchi and Kawamura (2019: figs 9A-D, 33A-G). Shen (1937) provided a comparison table between P. minor Ortmann, 1893 and P. quadridens based on some specimens from Kiachow Bay (=Jiazhou Bay), Shandong, northern China. Although we have no opportunity to examine his specimens in the present study, his P. quadridens should be attributed to our new species, since it shows the proportionally long hepatic lobe [estimated HpL/PoL=3.8 in 17.3 mm PCL, based on text fig. 5b in Shen (1937)] and the characteristic structure of G1 (Shen 1937: text- fig. 5b,   13. Proportional length of the cheliped (P1) and ambulatory legs (P2-5) meri in Pugettia longipes n. sp., P. ferox Kawamura, 2019, andP. quadridens (De Haan, 1837). A, fullgrown males; B, adolescent males; C, full-grown females. Bars with different letters are significantly different (Tukey HSD test, otherwise Steel-Dwass test, p<0.01) from each other. See Table 1 for sample numbers. In some groups marked with an asterisk, the significance of differences among the three species were not tested statistically due to small sample number (n<3) of P. longipes n. sp. Table 1. Comparison of proportional length (length/height) of cheliped and ambulatory legs meri among P. longipes n. sp., P. ferox Kawamura, 2019, andP. quadridens (De Haan, 1837 c, e, h). The shape of the basal antennal article must have belonged to the same specimen as previous characters, but unfortunately, it cannot be referred to any known species of Pugettia because its basis was incompletely drawn (Shen 1937: text fig. 5c). The transverse ridge on the thoracic sternum was not found in our specimens, but this is not a useful character: in some Pugettia, the sternite 1 is slightly depressed anteriorly and the boundary between sternites 1 and 2 appears as if there is a transverse ridge in some cases (Figs 1B, 5A). Despite many previous records of Pugettia in Northeast Asian waters (see Discussion in Ohtsuchi and Kawamura 2019), we found no further records of P. longipes n. sp. at least based on the figures and drawings. If possible, however, it is worth re-examining the non-figured specimens examined in these previous studies.
Distribution. This species is at present known only from the both northern and southern coast of Shandong Peninsula, Northeast China (Shen 1937;this study). Although habitat and depth were not recorded, our specimens were likely collected from shallow water because they were originally preserved in the same glass jar with P. ferox (MBM 160513), which is known mainly from depths shallower than 20 m (Ohtsuchi and Kawamura 2019).
Etymology. This species was named "longipes" alluding to their long, ambulatory legs.