Synchaeta grimpei Remane, 1929

Min, Hee-Min Yang and Gi-Sik, 2022, New record of two marine synchaetid rotifers (Monogononta: Synchaeta) from Korea, Journal of Species Research 11 (3), pp. 174-179 : 175-176

Synchaeta grimpei Remane, 1929 ( Figs. 1A , 2A , 3 )

나ḚṴẠḆḝ (ljḑ)

Synchaeta grimpei Remane, 1929: 122 .

Synchaeta procera Galliford, 1946: 15 - 16 .

A

Material examined. Korea, Incheon, Incheon Port (37° 27 ʹ 00 ʺ N, 126°39 ʹ 22 ʺ E), 24 Oct 2019, Hee-Min Yang. Voucher Number: NIBRIV0000879588 .

Diagnosis. Body 285 - 366 μm in length, cone-shaped, and gradually tapering to foot. Apical field wide and flat, with four lateral and dorsolateral styles. Color of auricles and rotatory organ orange. Red eyespot located near mastax. One pair of lateral antennae at the end of the trunk. Foot long, one-fourth of body length, 81 - 85 μm. Pedal glands symmetrical and elongated, each gland with two swollen parts. Length of pedal glands approximately equal to length of foot. Two small toes on the tip of the foot. Toe tips completely separated. Trophi virgate type. Apical rami with frontal hook, one distinct tooth, and serrated inner margin. Fine needle structure on the inner margin of mid-rami. Hypopharynx located in front of needle structure. Manubrium straight with broad lamella. Tip of manubrium knob-shaped. Fulcrum thick and dagger-like. Fulcrum consisted of thick rod on dorsal side with broad lamella on ventral side.

Distribution. Korea (this study), Baltic Sea ( Remane, 1929), British Atlantic coast ( Galliford, 1946), Gulf of Mexico ( Koste, 1981), Peter the Great Bay (Pacific Ocean) ( Chernyshev, 2005).

Remarks. Synchaeta grimpei is easily distinguished from other synchaetid species based on the following characteristics: (1) cone-shaped body, (2) wide and flat apical field, (3) indistinct auricles, and (4) long foot with two separated small toes. This species has been recorded from brackish water or marine environments ( Hollowday, 2002; Wilke et al., 2019). The Korean specimens were collected in September and October, at a water temperature of 20 - 24℃ and salinity of 28.5 - 29.6‰. The morphological characteristics of the Korean specimens were generally consistent with those observed in previous studies ( Hollowday, 2002; Wilke et al., 2019), except for the number of rami teeth. The descriptions by Koste (1981) and Hollowday (2002) documented the presence of multiple distinct teeth on rami; however, Korean specimens did not have distinct teeth in rami as described by Wilke et al. (2019). This is the second record of S. grimpei from the Pacific Ocean after Chernyshev (2005).

Molecular analysis. Partial COI sequences were obtained from five specimens. The intra-specific genetic distances were 0.0 - 1.7% within the Korean population (627 bp) (GenBank accession numbers: ON038411 - ON038415). The genetic distances of Korean and German S. grimpei specimen were 0.4 - 1.2% (483 bp, Table 1) (GenBank accession numbers: MK905783 - MK905785 ) ( Wilke et al., 2020) .

Figures

Fig. 1. Line drawing of rotifers.A. Synchaeta grimpei. B. Synchaeta vorax. Scale bars: 100 μm.

Fig. 2. Optical microscopic images of rotifers.A. Synchaeta grimpei. B. Synchaeta vorax. Scale bars: 100 μm.

Fig. 3. SEM image of the trophi of Synchaeta grimpei. A. ventral view. B. manubrium, lateral view. C. incus, ventral view. Scale bar: 50 μm.