A new species of the genus Cephalodella (Rotifera, Monogononta) from Korea, with reports of four additional cephalodellid species Author Yang, Hee-Min https://orcid.org/0000-0001-6288-1534 Department of Biological Sciences and Bioengineering, Inha University, Incheon 22212, Republic of Korea Author Min, Gi-Sik https://orcid.org/0000-0003-2739-3978 Department of Biological Sciences and Bioengineering, Inha University, Incheon 22212, Republic of Korea mingisik@inha.ac.kr text ZooKeys 2023 2023-01-23 1141 185 199 http://dx.doi.org/10.3897/zookeys.1141.91147 journal article http://dx.doi.org/10.3897/zookeys.1141.91147 1313-2970-1141-185 22AFCBD86E4B4C03B5251643237FE073 1E6205803C4058FEAEECB7905A4ABCD6 Cephalodella binoculata sp. nov. Material examined. Type locality. Soil from Incheon , Republic of Korea ( 37°24.788'N , 126°44.738'E ), 19 Jun. 2019 , Kyu-Seok Chae leg. Holotype . 1 female , glycerol permanent slide, NIBRIV0000896982. Paratype . 2 female , glycerol permanent slides, NIBRIV0000896983, NIBRIV0000896984; trophi preparation for SEM, NIBRIV0000896985 . Differential diagnosis. Cephalodella binoculata sp. nov. was most similar to C. carina Wulfert, 1959 in terms of frontal eyes, type B virgate trophi, dorsally curved toes, total length/toe length ratio, and short tail. The new species, however, was distinguished from C. carina by the following characteristics: (1) the new species has two distinct eyespots, whereas C. carina has one small eyespot; (2) the vitellarium of the new species contains eight nuclei, while that of C. carina contains six; and (3) the fulcrum of the new species is straight and without extension at the distal end, while the fulcrum of C. carina is thicker at the distal end. The new species also resembles C. gibboides Wulfert, 1951 and C. graciosa Wulfert, 1956. However, it is distinguished from C. gibboides by the shape of its manubrium and tail length. The manubrium of C. gibboides has a bump in the middle with no basal lamellae, whereas the new species has basal lamellae in the manubrium and no bumps in the middle. The shape of the distal end of the manubrium also differed between the two species. The tail of C. gibboides covers the foot, whereas that of the new species is short. The new species is distinguished from C. graciosa in several morphological characteristics as follows: (1) the trophi of the new species is symmetrical, while that of C. graciosa is asymmetrical; (2) the manubrium of the new species has basal lamellae, while that of C. graciosa does not; (3) the new species has two eyespots, while C. graciosa has one eyespot; and (4) the new species has eight nuclei in the vitellarium, while C. graciosa has six. Description. Female. Body moderately elongated and not laterally compressed (Figs 2 , 3A, B ). Dorsal and ventral margins slightly convex; posterior third of trunk gradually tapered to the foot. Lorica soft, transparent, and comprised of three body plates. Dorsal and ventral plates separated by narrow lateral sulci. Tail short and rounded. Head large, almost one-quarter of the total length. Head and trunk clearly distinguished by the neck fold. Corona oblique, convex, without lips. Dorsal antenna located near the junction of the head and trunk. Foot trapezoidal shape and moderate size, approximately 15% of the total length. Foot widest at the front and narrowed toward the back. Caudal setae absent. Short tail covered only part of the foot. Toes symmetrical and short, accounting for 16-17% of the total length. Toes smoothly tapered to posterior end, without any spines. In the lateral view, toes curved dorsally. In the dorsal view, toes always curved outwards. Saccate large brain extending over the neck fold. No retrocerebral organ. Two distinct red eyespots located in front of the head (Fig. 3C ). Distance between the two eyespots far and clear. Mastax large, with elongated salivary gland. Esophagus thin, passing between the brain and mastax. Gastric glands large, oval shaped, containing round granules, and located in the antero-dorsal part of the stomach (Fig. 3D ). Stomach colorless and indistinctly separated from the intestine. Anus located near the posterior end of the foot. Bladder round and large when fully filled. Vitellarium large with eight nuclei. Pedal glands short, sac-shaped. Trophi virgate, type B (see Fischer and Ahlrichs 2011 ), almost symmetrical (Fig. 4A ). Rami with no alulae on posterior end (Fig. 4C ). Basal chamber of rami wide, left side relatively larger than right at distal end. Shape of the subbasal chamber foramina also slightly asymmetrical; both foramina oval shaped, but the right foramen larger in length. Inner margin of rami with two distinct teeth and several comb-like teeth (Fig. 4C ). Fulcrum long and straight in the ventral view (Fig. 4A ). Terminal end of fulcrum simple, without any thickening or expanded shape. In the lateral view, the ventral margin straight and relatively thick (Fig. 4B ). No basal apophysis on fulcrum. Uncus with a large, single tooth. Manubria symmetrical. Each manubrium with a basal lamella, the length of which was approximately half of that of the manubrium (Fig. 4D ). Middle part of the manubrium with oblong-shaped foramina. Shaft of the manubrium thick and straight in lateral view; while terminal end curved inward in ventral view. Terminal end crutch-shaped, dorsal side stubby, ventral side pointed and curved upwards (Fig. 4B, D ). Figure 2. Line drawing of Cephalodella binoculata sp. nov., lateral view. Scale bar: 50 μm . Figure 3. Live specimen of Cephalodella binoculata sp. nov. observed under the optical microscope A lateral view B ventral view C eyespots D neck region and gastric glands, dorsal view. Scale bars: 50 μm ( A, B ); 20 μm ( C, D ). Figure 4. SEM image of the trophi of Cephalodella binoculata sp. nov. A ventral view B dorsolateral view C detail rami and unci, ventral view D detail manubrium, lateral view. Scale bars: 10 μm ( A, B ); 5 μm ( C, D ). Characteristics of male and eggs remain unknown. Measurement . Total length 134-155 μm , toe 26-29 μm , trophi 24-28 μm , ramus 8-9 μm , fulcrum 15-17 μm , manubrium 14-17 μm . Etymology. The specific name, binoculata , derived from the Latin word bi , meaning "two" and oculata , meaning "eyed" . Molecular data. Partial COI sequences were obtained from three specimens of C. binoculata sp. nov. (NIBR deposit numbers, NIBRGR0000649735-NIBRGR0000649737; GenBank accession numbers, ON898529-ON898531).