Patinapta neglectus, Yamana & Hirashima & Sato & Yamamori, 2025

Patinapta neglectus sp. nov.

[New Japanese name: Satsuma-himo-ikari-namako]

( Figs 18–20 View FIGURE 18 View FIGURE 19 View FIGURE 20 ; Tables 1 View TABLE 1 , 11 View TABLE 11 , 12)

Two specimens from Nagaura-higata (WMNH-2024-INV-193, 194) and one specimen from Kagoshima Bay (WMNH-2022- INV-154) were identified as new to science .

Diagnosis. Tentacles possessing sensory cups, situated on basal part of stem, not only on oral-side, but also on outer oral-side, numerous (50–80 cups in total). Body wall soft and thick, covered with verrucous surface layer, which sparsely includes ossicles. Anchor and anchor plate ossicles small. Anchor plate ossicles often exceed 110 μm, while anchor ossicles often exceed 140 μm, rarely equipped with teeth on bills (arms) of anchor ossicles, Total shapes of anchor plates strongly distorted, however basally without a concave. Outer edge of anchor plate ossicles lacking minute teeth at all, while one or two perforations of anchor plate ossicles with only one or two minute teeth. Ciliated funnels attached to inner side body wall along midline of left dorso-lateral interradius (IR3).

Type series. Holotype, WMNH-2022-INV-154; two paratypes, WMNH-2024-INV-193, 194.

Description of holotype (WMNH-2022-INV-154: middle-size depressed specimen). External and internal morphologies as follows ( Table 1 View TABLE 1 ): 5 year-old preserved specimen pale peanut color ( Fig. 18 View FIGURE 18 ). Tentacles 12, each with 9 digits of 4 pairs and unpaired 1. On oral-side of tentacle stem, about 30–40 sensory cups, also on outer oral-side tentacle stem, about 20–40 sensory cups present densely arranged in a V- shape band.

Polian vesicle in medio-ventral position, fusiform, single ( Table 1 View TABLE 1 ), stone canal single and thread-like, attached to narrow space between basal parts of tentacle ampullae at mediodorsal (IR5), suddenly turned upward and forward, resulted in it facing forward, distally with moldy surface madreporite. Ciliated funnels in one crowded band along left dorsal interradius (IR3).

Inside body, two tufts of gonad tubules attached with both sides of anterior dorsal mesentery. Intestine canal lacking loop, upper and under sides of intestine canal left blank, no whitish tubule organs adhered to intestine canal.

Body wall smooth surface, soft but thick, covered by a surface layer like "intestinal villi," with ossicle arranging latitudinal layout of all as sets of anchor and plate. Both sides along five longitudinal muscles with distal ends of anchor ossicles facing towards interradial area, however ossicles on radial body walls upon longitudinal muscles and interradial body walls have distal ends randomly facing either direction.

The present results of ossicle morphologies

Body wall ossicles anchors and anchor plates ( Fig. 19B; D View FIGURE 19 , Table 11 View TABLE 11 ). Anchor plates ranged within 85–123 μm in length. Size of perforations not noticeably variable between central area and marginal area, and instead almost constant between central area and marginal area, because of only few marginal perforations rarely equipped. Plates showed strong distortion, with approximate hexagonal arrangement perforations. Perforations of anchor plate ossicles mostly teethless, but seldomly possessing 1–2 minute teeth, while outer edge of all anchor plate ossicles lacking minute teeth. Two calculated indicators for anchor plates and a parameter varied; APS = 0–11.3; Ntp = 0–2; APT = 0–11.8% ( Fig. 19B; D View FIGURE 19 , Table 11 View TABLE 11 ).

Anchor ossicles ranged within 140–188 μm in length ( Fig. 19B; D View FIGURE 19 , Table 11 View TABLE 11 ). Most anchor arms (bills) devoid of minute teeth on their outer tips, numbers of teeth very small within 0–4 (mostly 0–2 in one arm of the anchor ossicle), and anchor ossicles of this specimen possessed narrow stem and also relatively narrow anchor arm width, with ASW = 22.7–28.3%; AEW = 38.5–55.1%. T-shaped basal end of the anchor ossicle of this species crescent-shaped ( Fig. 19B; D View FIGURE 19 ).

Body longitudinal muscle, granule ossicles of this specimen ranged within 21–54 μm in length ( Fig. 19C; E View FIGURE 19 , Table 11 View TABLE 11 ). Both C-shaped and O-shaped granule ossicles, mostly flattened, distorted and roundish triangle form, rarely not distorted and usual oval form. The calculated indicator for granule proportions were varied within GP = 29.5–123.0%; GCO = 46.1–52.9% and did not have noticeable differences in amounts between the O-shape and C-shape granules.

Tentacle ossicles rods, often with complex shape, ranging within 62–85 μm in length ( Fig. 19A View FIGURE 19 , Table 9 View TABLE 9 ). Two calculated indicators for rod proportions and complexities varied within RP = 9.6–21.5%; RC =2.7–17.8 ( Table 11 View TABLE 11 ).

Etymology. The species name neglectus , alluding to Y.Y.’s misidentification of the holotype specimen (WMNH-2022-INV-154). Previously, this specimen was reported as P. ooplax with young and small ossicles, to Mr. Soichiro Tashima of Kusunoki-Shizenkan (N.P.O. Kusunoki Nature Study Museum), Aira City, Kagoshima. This misjudgment was made due to Y.Y.’s unsympathetic view on ossicle morphologies at that time (December 2022).

Observation on the morphologies of calcareous ring

Calcareous plates 12, mostly firmly bound ( Fig. 20 View FIGURE 20 ), with slight anterior projection and deep posterior depression in interradial plates, while only posterior depression in radial plates. Only medio-ventral radial plate perforated in its anterior half, relatively large perforation. Other four radial plates devoid of perforation, however, there were narrow “interradial perforations” situated in the connections between 4 plates situated in right and left dorso-lateral positions (IR4’; RIII; IR3’; RII), where additional interradial plate (IR4’; IR3’) formed triangular shapes and adjacent radial plate (RIII; RII) form creviced squarish shapes, and weakly bound by their apical ends.

Ossicle variation among the type specimens

Among three specimens, two specimens (WMNH-2022-INV-154; 2024-INV-194) were mature and possessed gonad tubules, while one specimen (WMNH-2024-INV-193) was immature and was the smallest specimen, which also possessed under-developed ossicles as below: short rod ossicles in tentacles, stout anchor and small anchor plate ossicles in body wall. In tentacles, simple short rod ossicles possess up to only two perforations and only four minute branches, anchor stem short and stout; the single basal tip of anchor plate ossicles with besides noticeable defections, resulting in the “table-tennis racket-form” those of congeners of the apodid genus Labidoplax Ōstergren , as such feature was not observed from two mature specimens, which possessed normal ovoid anchor plates. Body wall ossicles anchors and anchor plates. Anchor plate ossicle length and calculated indicators of three specimens ranged within: 85–123 μm in length, APS =0–11.3, Ntp =0–2, APT =0–11.8%. Among these values, length and non—size dependance indicator of plate skewness APS of anchor plate ossicles were not significantly different (Ps>0.05, Kruskal-Wallis’ test), while frequency of teethed perforations APT and their parameter Ntp were significantly different on the ventral side (Ps <0.005, Kruskal-Wallis’ test) but not significantly different on dorsal side (Ps>0.05, Kruskal-Wallis’ test). From these results, the anchor plate ossicles in the body wall of the present three specimens were not different in ossicle length or the skewness of the layout for perforations However, number of teethed perforation and their occupancies were different on the ventral body wall. Therefore, the length (about 85–120 μm), numbers of teethed perforations (0–2) on dorsal side, and slightly distorted (up to 11.3) anchor plate ossicles can be appropriate diagnostic characters.

Anchor ossicle length and calculated indicators ranged within: 108–188 μm in length, ASW =17.3–28.3%, AEW =29.6–55.4% ( Table 11 View TABLE 11 ). Among these values, lengths, the indicator for anchor stem breadth ASW of anchor ossicles and for basal / distal ends width AEW were significantly different (Ps <0.005, Kruskal-Wallis’ test, both in ventrally and dorsally), while number of the teeth was not significantly different (Ps>0.05, Kruskal-Wallis’ test, both ventrally and dorsally). From these results, total shapes of anchor ossicles in the body wall of the present three specimens cannot be appropriate keys, but the excessively low number of the counts for teeth can be the accurate key.

Longitudinal muscle involved both O-shaped and C-shaped granule ossicles, length and calculated indicators ranged within: 28–54 μm length, GP =28.9–123.0%, GCO =33.3–66.7% ( Table 11 View TABLE 11 ). Among these values, length of granule ossicles and calculated indicator for proportions GP were different significantly (Ps <0.005, Kruskal-Wallis’ test, both in ventrally and dorsally), while the ratio C- or O-shaped granule ossicles GCO were not different significantly (Ps>0.05, Kruskal-Wallis’ test, both ventrally and dorsally), but different significantly in GCO (Ps <0.05, χ 2 -multiple test, both in ventrally and dorsally). Therefore, the length and proportion of the granule ossicles cannot be appropriate keys, while ratio C- or O-shaped granule and the feature of granule ossicles being “flattened, distorted and roundish triangle form” of this species can be appropriate keys.

Tentacle ossicles rods, length and calculated indicators of three specimens ranged within: 44–98 μm in length, RP =9.6–21.5%, and RC =2.7–17.8. Among these values, length of rod ossicles, nonsize dependence complexities (RC) were significantly different (Ps <0.005, Kruskal-Wallis’ test), while nonsize dependence indicator for proportion (RP) was not different significantly (Ps>0.05, Kruskal-Wallis’ test). From these results, the rod ossicles in the tentacles of the present three specimens had similar proportions, simultaneously complexities and length increased by body growth ( Table 11 View TABLE 11 ). Therefore, the morphologies of the rod ossicles of this species cannot be appropriate diagnostic characters.

Remarks

In the present three type materials, ossicle morphologies were noticeably different between matured holotype and two small paratypes, one immature and one in the development-stage of tubules ( Table 1 View TABLE 1 ). From the present results of measurements and counts on ossicles ( Table 11 View TABLE 11 ), it can be assumed that several morphological changes relating with individual growth: i) in anchor ossicles, minute teeth on outer edge of anchor-bills take numbers larger in small animals than in large animals; ii) in anchor plate ossicles, teethed perforationstake larger number in small animals than in large animals; however, iii) in tentacle rods, complexity of rod-shape (RC) take values higher in large animals than in small animals, and complexity may not be increasing or decreasing by individual growth. In the previous nominal species, none of the species possessed calcareous ring only perforated on medio-ventral plate (Table 7-3), and this must be largest difference of the present new species among all the congeners of genus Patinapta previously described.

Distribution

Only known from Kyushu Island and adjacent islands, Mature specimen has been collected only from Iso Beach (the type locality) on the inner coast of Kagoshima Bay ( Table 12). At the type locality, the holotype material was collected from intertidal sandy beach with boulders. Among the specimens housed in WMNH-INV, including the present specimens, 3 bottles including 5 specimens were identified as this species ( Table 12). Other than the type locality, 2 immature and mature specimens were collected from Nagaura-higata flat, Amakusa City, Kumamoto and 2 immature specimens collected from Uchiura Bay, Kamikoshiki-jima Island, adjacent to Kagoshima, Kyushu Island, Japan, and were identified as this species.