Patinapta taiwaniensis Chao, Rowe & Chang, 1988

Yamana, Yusuke, Hirashima, Kentarou, Sato, Masanori & Yamamori, Luna, 2025, First revision of the apodid holothurian genus Patinapta Heding, 1928 (Synaptidae) in Japanese waters, with establishment of four new species from Kyushu Island and Ryukyu Islands, southwestern Japan, Zootaxa 5569 (1), pp. 1-54 : 17-23

Patinapta taiwaniensis Chao, Rowe & Chang, 1988

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

( Figs 9–11 ; Tables 1 , 4 , 5 )

Patinapta taiwaniensis Chao, Rowe & Chang, 1988: 33–38 + textfigs 1–5; accepted after Liao 1997: 264–265 + textfig. 157a–e.

Original species description (summarized from original diagnosis and description, figures in Chao et al. 1988: 33–38 + textfigs 1–5).

Type locality, southern end of Taiwan. Six specimens examined in the study reported by Chao et al (1988). Tentacles 12–13 short, body vermiform up to 150 mm. Body color whitish, more or less transparent, five longitudinal muscle bands being visible outside body. Each tentacle possesses 4–5 pairs of digits, with unpaired terminal digit. On the oral-side of tentacle stem, numerous (28–36) sensory cups arranged in V- shape. Calcareous ring the same composition as P. ooplax , but the anterior tips not undulated at all. Polian vesicles double. Ciliated funnels as one crowded row along left dorsal interradius (IR3).

Body wall ossicles consisted of anchors and anchor plates. Anchor plates ranged within 73–103 μm in length, size of perforations noticeably varied between central and marginal locations. Positions of perforations were irregular, largest perforations situated biased from the center, surrounded by a ring of up to 6 smaller perforations. Largest perforations and several larger perforations equipped with 2–6 spaced teeth arraign along with inner rim. Anchor ossicles ranged within 155–160 μm in length, all anchor arms (bills) equipped with 2–4 minute teeth on their outer tips.

Longitudinal muscle ossicles (misidentified as military granules in “body wall” in the original description) consisted of minute curved rods, merely with closed perforations, ranged within 22–58 μm in length and about 10 μm in width.

Tentacle ossicles only rod ossicles, weakly curved and mostly branched or perforated at distal ends. Rod ossicles ranged within 50–90 μm in length and 7–11 μm in breadth.

Description of present result

The largest specimen from Sesoko-jima island, Okinawa (WMNH-2016-INV-237) was identified as this species. External and internal morphologies as follows ( Table 1 ): preserved body color, semi-transparent pink-whitish pale color ( Fig. 9 ). Tentacles 12, each with up to 5 pairs of digits with unpaired terminal digit. On the oral-side of tentacle stem, about 16–26 sensory cups linearly arranged in a V- shape. Sensory cups attached to all tentacles, however sporadically in the dorsal tentacles. Polian vesicle double, narrow, fusiform, 4.11 mm length, attached with posterior end of the water brood circle just behind calcareous ring at medio-ventral position (RI). Tentacles ampullae12 attached with outer circle of calcareous ring, each ampullae narrower and shorter than Polian vesicle. Stone canal single, thread-like, attached to narrow space between basal parts of tentacle ampullae at mediodorsal (IR5), suddenly turned upward and forward, resulting in it facing forward, distally with mold-like madreporite. Ciliated funnels are attached along midline of left dorsal interradial (IR3) inner-side body wall, erupting as one sporadical row in this specimen.

Inside body, two tufts of gonad tubules attached to both sides of anterior dorsal mesentery, also two whitish tubule organs adhered to upper and under sides of intestine canal. Intestine canal lacking loop.

Body wall smooth surface, soft but thick, 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. In the present study, only this species possesses segmented-like body wall as an annelid‐plan (latitudinal contractions occurring at uniform intervals).

The present results of ossicle morphologies

Body wall ossicles are anchors and anchor plates ( Fig. 10B, D ; Table 4 ). Anchor plates ranged within: 94–113 μm in length (mean±SD=104.6±6.0 μm ventrally, 94.4±7.9 μm dorsally). Size of perforations noticeably varied between central area and marginal area. Largest perforation situated slightly biased from the center, surrounded by a ring of up to 6 smaller perforations. Largest perforations and several larger perforations equipped with 2–8 spaced blunt-teeth discontinuously standing along their peripheral edge, however teethed perforations were small number, and several larger perforations lacked teeth. Two calculated indicators for anchor plates and a parameter were variated within APS =0–0.7 (mean±SD=0.4±0.3 ventrally, 0.4±0.3 dorsally); Ntp =3–6 (mean±SD=4.2± 1.1 in ventrally, 3.3± 0.5 in dorsally); APT =4.2–31.6% (mean±SD=21.8±6.0% ventrally, 17.8±2.2% dorsally), thus this specimen had values “ APS =0.3±0.3, Ntp =4.3±2.1, APT =20.4±9.0%,” close to those calculated from Chao’s work (1988) based on the holotype.

Anchor ossicles ranged within 138–163 μm in length (mean±SD=152.0±7.4 μm in ventrally, 150.7±8.0 μm in dorsally) ( Fig. 10B, D ; Table 4 ). All the anchor arms (bills) equipped with minute teeth on their outer tips, numbers of teeth ranged within 2–6 (mean±SD=3.7±1.0 in ventrally, 4.4± 0.9 in dorsally): about 2 teeth on each anchor arms. Two calculated indicators for anchors ranged within ASW =19.1–27.6% (mean±SD= 20.8±1.2% in ventrally, 24.3±1.2% in dorsally); AEW =43.8–63.5% (mean±SD=48.2±4.1% in ventrally, 57.6±3.7% in dorsally), thus this specimen had values of “ AEW =42.6 % (n =2)” close to those calculated from Chao’s work (1988) based on the holotype, however “ ASW =12.3% (n =2)” was different from the holotype, being noticeably larger than that of the syntype.

Body longitudinal muscle ossicles granule ossicles ( Fig. 10C, E ; Table 4 ), both O-shaped and C-shaped granules ossicles were observed, ranging within 20–37 μm in length (mean±SD=29.2±4.0 μm in ventrally, 29.8±4.9 μm in dorsally). The calculated indicator for granule proportions was variated within GP =37.1–70.8% (mean±SD=47.6±6.0% in ventrally, 48.1±11.1% in dorsally) and GCO =66.7% in ventrally, 84.6% in dorsally, thus this specimen showed close value of “ GP =31.0±9.3% (n =11)” which calculated from Chao’s work (1988) based on the holotype, however did not show close value “ GOC =18.2% (n =11),” while more large value for that.

Tentacle ossicles were rods ( Fig. 10A , Table 4 ), their length and calculated indicator for rod proportions (RP) and complexities (RC) ranged within: 69–104 μm in length (mean±SD=81.1±10.3 μm), RP = RP = 9.2–14.7% (mean±SD=11.7±1.9%), and RC =8.9 (mean±SD=9.3±2.9), thus this specimen had values “ RP =10.9% and RC =7.9” close to those calculated from Chao’s work (1988) based on the holotype.

Observation on the morphology of calcareous rings

Calcareous plates 12, firmly bound ( Fig. 11 ), with slight anterior projection and slight posterior depression. All five radial plates (RI, RII, RIII, RIV, RV) perforated in each anterior half. There is no space between the additional interradial plate (IR4’; IR3’) and adjacent radial plate (RIII; RII).

Ossicle variation among three specimens

Three specimens were chosen as representative of different body sizes ( Table 1 ) to investigate if morphological changes in ossicles occur in different body sizes. Tentacle ossicles were rods, their length and calculated indicators ranged within: 58–84 μm length, RP =10.9–14.1%, and RC =6.2–14.1 (in small specimen WMNH-2021-INV-542, Table 4 ); 51–95 μm length, RP =9.2–18.1%, and RC = 4.7–14.9 in middle-size specimen WMNH-2016-INV-236, Table 4 ); and 69–104 μm length, RP =9.2–14.7%, and RC =5.4–14.9 (in large-size specimen WMNH-2016-INV-237, Table 4 ). Among these values, lengths of rod ossicles and rods were not different significantly (P>0.05, Kruskal-Wallis’ test), and also two calculated indicators for proportion (RP) and complexities (RC) were not significantly different (Ps> 0.05, Kruskal-Wallis’ test) among the three specimens. From these results, the rod ossicles in the tentacles of the present three specimens were almost the same in length, proportions and complexities in different body sizes. Therefore, the length (average about 70–80 μm), proportions (average about 12–13%), and complexities (average about 8–9) can be appropriate diagnostic characters.

Body wall ossicles are anchors and anchor plates. Anchor plate ossicles length and calculated indicators ranged within: 98–125 μm in length, APS =0–0.7, Ntp =3–7, APT =9.8–22.7% (in small specimen WMNH-2021-INV-542, Table 4 ); 94–135 μm in length, APS =0–0.7, Ntp =3–6, APT =8.57–31.6% (in middle-size specimen WMNH-2016- INV-236, Table 4 ); and 83–113 μm in length, APS =0–0.7, Ntp =3–6, APT =14.2–31.6% (in large-size specimen WMNH-2016-INV-237, Table 4 ). Among these values, lengths of anchor plate ossicles and the skewness APS, (were not different significantly (Ps>0.05, Kruskal-Wallis’ test, both in ventrally and dorsally) among specimens, while the frequency of teethed perforations APT, and their parameter Ntp differed significantly among specimens (Ps <0.005, Kruskal-Wallis’ test). From these results, the anchor plate ossicles in the body wall of the present three specimens were not different in ossicle lengths or skewness of the layout for perforations, regardless of the different body sizes of the specimens. Therefore, the length (average approximately 100–120 μm), counts of teethed perforations, and frequencies in total perforations of the anchor plate ossicles of this species cannot be appropriate diagnostic characters.

Anchor ossicle lengths and calculated indicators ranged within: 138–165 μm length, ASW =21.2–25.0%, AEW =42.5–48.0% (in small specimen WMNH-2021-INV-542, Table 4 ); 126–167 μm length, ASW =15.9–25.4%, AEW =37.2–57.9% (in middle-size specimen WMNH-2016-INV-236, Table 4 ); and 138–163 μm length, ASW =19.1– 27.6%, AEW =43.8–63.5% (in large-size specimen WMNH-2016-INV-237, Table 4 ). Among these values, lengths of anchor ossicles were not significantly different among specimens (Ps>0.05, Kruskal-Wallis’ test), while the indicator for anchor stem breadth ASW and for basal / distal ends width AEW were significantly different (Ps <0.005, Kruskal-Wallis’ test, both in ventrally and dorsally). From these results, the anchor ossicles in the body wall of the present three specimens were not different in ossicle length for different body sizes, however, the anchor ossicles were different in the stem breadths, and basal / distal ends balances. Therefore, the length of the anchor ossicles of this species can be an appropriate diagnostic character.

Longitudinal muscle included both O-shaped and C-shaped granule ossicles, length and calculated indicators ranged within: 22–45 μm length, GP =34.1–68.2%, GCO =20.0–71.4% (in small specimen WMNH-2021-INV-542, Table 4 ); 19–31 μm length, GP =37.9–70.0%, GCO =50.0–58.3% (in middle-size specimen WMNH-2021-INV-542, Table 4 ); and 20–37 μm length, GP =37.1–70.8%, GCO =66.7–84.6% (in large-size specimen WMNH-2016-INV-237, Table 4 ). Among these values, lengths of granule ossicles were significantly different (Ps <0.005, Kruskal-Wallis’ test, both ventrally and dorsally) among the specimens, and also two calculated indicators GP and GCO were significantly different (GP: Ps <0.005, Kruskal-Wallis’ test, GCO: Ps <0.05, χ 2 -multiple test, both ventrally and dorsally). Therefore, the length, proportions and the ratio C- or O-shape granule ossicles of this species changed due to individual body growth, and cannot be appropriate diagnostic characters.

Remarks

This is the first record of Patinapta taiwaniensis from Japan:the external and internal morphologies of three specimens were largely in agreement with the original description for this species ( Chao et al. 1988), however observed ossicle morphologies, were different from the original description, especially in the indicators GCO and APS, with present values about +40% and +10% larger than the values calculated from the original description, respectively ( Table 4 ). Additionally, numbers of sensory cups (16–26 cups) attached to the tentacle stem of the present specimens were also noticeably smaller than those noted in the original description (28–36 cups). Therefore, the possibility these represent different species remains. However, there were no critical differences detected between ossicle shapes of the original description and the present study, and we judge the present three specimens to be accommodated in this species. Further molecular based studies of these species are desirable.

Distribution

Type locality, south end of Taiwan ( Chao et al. 1988). Also reported from Hainan Island ( Liao 1997). The present two specimens from Sesoko-jima Island were collected from mid-intertidal sandy beach, and one specimen was from the Osato-gawa collected from the estuarine intertidal flats, in the river mouth. The present two localities were intertidal shores on the East China Sea. Basing on the identifying features suggested from the present results, WMNH-INV accommodates a total of 76 specimens preserved in 5 bottles (Kyushu Island 1; Ryukyu Islands 4) ( Table 5 ).

Figures

FIGURE 9. External view of a specimen collected from Sesoko-jima Island, Okinawa, identified as Patinapta taiwaniensis Chao, Rowe & Chang, 1988, in the present study (large-size specimen, WMNH-2016-INV-237): A, lateral view, anterior left, dorsal top; B, oral-side view of the tentacles; C, outside view of the tentacles.

FIGURE 10. SEM images of the ossicles extracted from a specimen collected from Sesoko-jima Island, Okinawa, identified as Patinapta taiwaniensis Chao, Rowe & Chang, 1988, in the present study (one large-size specimen, WMNH-2016-INV-237): A, ossicles from tentacle; B, ossicles from mid-dorsal body wall; C, ossicles from mid-dorsal longitudinal muscle; D, ossicles from mid-ventral body wall; E, ossicles from mid-ventral longitudinal muscle.

FIGURE 11. Outer-surface view of calcareous ring plates of a specimen collected from Sesoko-jima Island, Okinawa, identified as Patinapta taiwaniensis Chao, Rowe & Chang, 1988, in the present study (one large-size specimen, WMNH-2016-INV-237). Positions of the plates denoted by Ludwig’s [1889–1892 (1889), p156] system: RI–RV and IR1–IR5 where R and IR stands for positions for radius and interradius, respectively. Hence RI, mid-ventral; RII, left ventral; RIII, right ventral; RIV, left dorsal; RV, right dorsal; and: IR1, left ventral; IR2, right ventral; IR3-IR3’, left dorso-lateral; IR4-IR4’, right dorso-lateral; IR5, mid-dorsal. Anterior top.