Chromadorina communis, Guo & Wang & Li & Wang, 2023

Guo, Wen, Wang, Mengna, Li, Haotian & Wang, Chunming, 2023, Description of a new nematode species, Chromadorina communis sp. nov. (Nematoda, Chromadoridae), from Changdao Island, China and phylogenetic analysis of Chromadorida based on small subunit rRNA gene sequences, ZooKeys 1159, pp. 121-131 : 121

Chromadorina communis sp. nov.

Figs 2 , 3

Diagnosis.

Chromadorina communis sp. nov. is characterized by its medium-sized body, finely striate cuticle with punctuations, buccal cavity with three equally sized teeth, absent ocelli, four cephalic setae 6-8 μm long, oval amphidial fovea level with cephalic setae, curved spicules with tapered distal end, boat-shaped gubernaculums, five or six cup-shaped precloacal supplements, and a conical tail with a short spinneret.

Material examined.

Four males and two females were measured and studied. Holotype: m#1 on slide 22YTCD6-2-17; paratypes: m#2 on 22YTCD6-2-15, m#3 on 22YTCD6-2-18, m#4 on 22YTCD6-2-11, f#1 on 22YTCD6-2-1, and f#2 on 22YTCD6-2-18. Type specimens were deposited in the Institute of Oceanology, Chinese Academy of Sciences, Qingdao.

Measurements.

Detailed measurements information of individual specimens are shown in the Table 1 .

Description.

Males. Body cylindrical and medium-sized. Inner and outer cephalic setae inconspicuous. Four cephalic setae 6-8 μm in length (0.55-0.73 head diameter long), two pairs of sublateral cervical setae (4-5 μm long) present. Somatic setae (3-4 μm long) scarcely present in pharynx and on caudal region. Cuticle faintly striate, with homogeneous punctuations without longitudinal differentiation. Ocelli absent. Amphidial fovea oval, level with cephalic setae, in some specimens difficult to observe. Buccal cavity slightly cuticularized and funnel-shaped, with three equally sized, solid teeth. Pharynx cylindrical, with posterior end widened into obvious bulb (20.1-21.8% of pharynx length). Nerve ring slightly posterior to middle pharynx region (54-63% of pharynx length). Secretory-excretory system pore on anterior end of body (3-4 μm from anterior end).

Reproductive system monorchic, with anterior testis outstretched, located to right of intestine. Spicules paired, curved, 1.2-1.3 cloacal body diameters long; proximal end slightly cephalate and distal end tapered. Gubernaculum simple, boat-shaped, parallel to the distal end of spicules. Five or six cup-shaped precloacal supplements, 12 μm from cloacal opening and 12-16 μm apart. Tail conical, with short spinneret, with three caudal glands in line.

Females. Similar to males in most characteristics. Reproductive system didelphic and amphidelphic, with reflexed ovaries. Anterior ovary to right of intestine and posterior ovary to left of intestine. Vulva slightly anterior to mid-body. Vagina short and sclerotized.

Type locality and habitat.

Changdao Island, Shandong Province, China, 37°57'N, 120°43'E, at the confluence of the Yellow and the Bohai seas. Salinity 28.1‰ ± 0.36.

Distribution.

Occurred on rock surfaces with Ulva lactuca and U. prolifera .

Etymology.

Latin, communis, “common”.

Differential diagnosis.

Chromadorina communis sp. nov. is similar to the cultured species C. hirommi Kito & Nakamura, 2001 in body length, length of cephalic setae, and numbers of precloacal supplements, but it differs in tooth shape (three equally sized teeth vs dorsal tooth large and subventral teeth small), absence of ocelli (brownish pigment present in C. hirommi ), position of excretory pore (0.3 head diameter from anterior body end vs 1.8 head diameter from anterior body end), spicule length and shape (27-28 μm, distal end tapered vs 22-25 μm, distal end blunt and bifurcate), and gubernaculum shape (slightly cuticularized and boat-shaped vs well cuticularized with wavy dorsal fringe, distal parts of lateral pieces distinct and directed ventrad).

Eleven sequences of Chromadorina are included in the phylogenetic analysis, but only three species ( C. bioculata , C. germanica , and C. communis sp. nov.) are identified to species, and C. bioculata was found in freshwater. Chromadorina communis sp. nov. shows a close relationship with Chromadorina sp. (KJ636255), but it differs by 3.1% (52 in 1678 bp, including three gaps). Chromadorina communis sp. nov. is supported as a new species by both phylogenetic and morphological analyses.

Figures

Figure 2. Chromadorina communis sp. nov. A lateral view of male anterior region showing buccal cavity and pharyngeal region (holotype) B lateral view of male anterior region showing buccal cavity (holotype) C lateral view of male anterior region showing cuticle and amphids (holotype) D lateral view of male whole body (holotype) E lateral view of female anterior body showing buccal cavity and pharyngeal region (22 YTCD 6 - 2 - 1) F lateral view of female entire body showing vulva (22 YTCD 6 - 2 - 1) G lateral view of female posterior body (22 YTCD 6 - 2 - 1) H lateral view of male posterior body, showing precloacal supplements and tail (holotype) I lateral view of spicules and gubernaculums. Scale bars: 20 µm (A-C, E); 50 µm (D, F); 30 µm (G, H).

Figure 3. Chromadorina communis sp. nov. A lateral view of male anterior region showing buccal cavity and teeth (arrow) (holotype) B lateral view of male anterior region showing cuticle (holotype) C lateral view of female anterior region showing amphids (arrow) and cephalic setae (22 YTCD 6 - 2 - 1) D-F lateral view of male posterior body showing spicules, precloacal supplements, and gubernaculum (holotype). Scale bars: 20 µm.