Peltogaster lineata Shiino, 1943

Jung, Jibom, Yoshida, Ryuta & Kim, Won, 2019, Ophiacantha scissionis Lee & Stöhr & Bae & Shin 2019, sp. nov., Zoological Studies (Zool. Stud.) 58 (33), pp. 1-12 : 7-11

Peltogaster lineata Shiino, 1943 ( Fig. 5A )

Peltogastridae Lilljeborg, 1859

Peltogaster Rathke, 1842

Material examined: On Pagurus brachiomastus : 1 Ind., Yangyang, 37°55'49.00"N 128°47'25.00"E, Scuba, 10 Apr. 2014, Coll. Park JH, MADBK 430101_001, host: male, SL 4.7 mm.

On P. filholi : 1 Ind., Busan, 35°8'16.83"N 129°9'37.01"E, 8 Oct. 2015, Coll. Jung J, MADBK 160707_043, host: male, SL 3.4 mm.

Hosts: P. brachiomastus , P. filholi , P. nigrivittatus , P. maculosus ( Paguridae ).

Distribution: Japan, Korea.

Remarks: Morphologically, the externa on the examined materials showed a single oval shape of whole externa, terminal located and slightly projected mantle, circular mantle opening, and presence of a chitinous shield, in close agreement with the original description ( Shiino 1943) and re-description of Peltogaster lineata by Yoshida et al. (2014). In Korean P. lineata , the projection of the mantle aperture is slightly elevated. In addition, the mitochondrial sequence of the examined material ( MK 604142, MK 604143, MK 604159, MK 604160) is similar to the DNA sequences ( AB 778060, AB 778092) of the species reported by Yoshida et al. (2014). The present study reports Pagurus brachiomastus as the fifth host of Peltogaster lineata after Pagurus japonicus , P. filholi , P. nigrivittatus , and P. maculosus ( Shiino 1943; Yoshida et al. 2014). In addition, the specimen of Peltogaster lineata ( MADBK 430101_001) was found in Yangyang, Korea, much farther north (37°55'N) than the previous record in southern Japan (35°09'N) ( Shiino 1943; Yoshida et al. 2014). Furthermore, this is the first report of this species collected from outside of Japanese waters.

The mantle of the Pagurus filholi specimen ( MADBK 160707_043) has a U-shaped opening, similar to that of Peltogaster postica . However, the former’s mitochondrial sequence ( MK 604143, MK 604160) differed from that of P. postica , but it constituted a single clade of sequences with those of P. lineata in this study ( MK 604142, MK 604159) and previous studies ( AB 778060, AB 778092) (Figs. 3, 4). In addition, Yoshida et al. (2014) reported that P. lineata can parasitize Pagurus filholi . Therefore, the present study identified this specimen as Peltogaster lineata based on molecular and ecological characteristics.

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Fig. 3. Maximum likelihood rooted trees of COI sequences of Peltogastridae from Korea and NCBI. The number next to the branches is the percentage of replicate trees in which the associated taxa clustered together in the bootstrap test. *means NCBI sequence.

Peltogaster postica Yoshida and Osawa in Yoshida, Osawa, Hirose, and Hirose, 2011 ( Fig. 5B, 5C )

Material examined: On Pagurus filholi : 4 Inds., Jeju, 33°31'38.25"N 126°35'4.60"E, 31 Oct. 2010, Coll. Kang SH, MADBK 160707_009, host: 3 males, SL 3.1- 4.0 mm, 1 female, SL 3.3 mm; 1 Ind. (2 externae), Jeju, 33°31'23.00"N 126°33'31.60"E, 4 May 2016, Coll. Jung J, MADBK 160707_052, host: male, SL 3.7 mm; 1 Ind., same as MADBK 160707_052, MADBK 430102_001, host: male, SL 3.2 mm.

Host: P. filholi , P. minutus , P. nigrivittatus , P. angustus ( Paguridae ).

Distribution: Southern Honshu and Okinawa ( Japan), Taiwan, Korea.

Remarks: The externa of examined materials had morphological characteristics, such as irregularly elongated body, terminal-posited elevated mantle, U-shaped mantle opening, and chitinous shield similar to the original description ( Yoshida et al. 2011) and re-description of Peltogaster postica by Yoshida et al.

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Fig. 4. Maximum likelihood rooted trees of 16S rRNA sequences of Peltogastridae from Korea and NCBI. The number next to the branches is the percentage of replicate trees in which the associated taxa clustered together in the bootstrap test. *means NCBI sequence.

(2014). Furthermore, the COI (MK604144-MK604149) and 16S rRNA sequences (MK604161-MK604165) of the examined material belonged to a single clade of DNA sequences (AB602392, AB778105) as that of P. postica reported by Yoshida et al. (2011 2014). According to Yoshida et al. (2011 2014), P. postica is found on Pagurus filholi as well as on P. minutus and P. nigrivittatus in Japan. However, the Korean Peltogaster postica is found in the abdomen of Pagurus filholi only, even though P. minutus and P. nigrivittatus are also present in Korea. Therefore, the examination of additional specimens is necessary to determine whether Peltogaster postica is parasitic on Korean Pagurus minutus and P. nigrivittatus .

Figures

Fig. 5. Korean peltogastrids. A, Peltogaster lineata on Pagurus brachiomastus and its mantle, MADBK 430101_001; B, Peltogaster postica on Pagurus filholi, MADBK 160707_009; C, mantle of B; D, Peltogaster aff. ovalis on Pagurus rathbuni, EVOSYS 260720#013; E, mantle of D; F, G, Peltogaster aff. reticulatus on Pagurus proximus and its mantle, MADBK 160718_040; H, Peltogaster sp. 2 on Areopaguristes nigroapiculus and its mantle, EVOSYS 260510#008; I, Peltogasterella gracilis on Pagurus pectinatus, MADBK 160715_016; J, mantle of I; K, Peltogasterella aff. gracilis on Porcellanopagurus nihonkaiensis, MADBK 160730_002.