Ptycholaimellus luoyang, Shih & Chen & Guo, 2022

Shih, Yi-Jia, Chen, Yu-Zhen & Guo, Yu-Qing, 2022, Fig. 7 in Fig. 3 in Fig. 5 in Fig. 3 in Fig. 1 in Fig. 20. A-E in Establishment of A New Bornean Genus of Gecarcinucidae (Crustacea: Brachyura), with Descriptions of Five New Species., Zoological Studies 61 (20), pp. 1-9 : 3-6

Family Chromadoridae Filipjev, 1917 Genus Ptycholaimellus Cobb, 1920

Ptycholaimellus luoyang sp. nov. ( Figs. 1A–G ; 2A–E ; Table 3) urn:lsid:zoobank.org:act:DF62ED83-B149-41B1-9A64-63850F9683B7

Material examined: Holotype: one male (ò 1: QZLYJ 201704262 U 1002) ; Paratypes: four males (ò 2: QZLYJ 201704262U2004, ò 3: QZLYJ 201704261D1010, ò 4: QZLYJ 201704262U2001, ò 5: QZLYJ 201704261M2002), two females (ñ 1: QZLYJ 201704262U3003, ñ 2: QZLYJ 201704263D1001), one juvenile ( QZLYJ 201704261U2004). All specimens were collected from the Luoyang River estuary in

Quanzhou City, Fujian Province (118.69°E; 24.95°N) in April 2017.

Type locality and habitat: Intertidal mud sediment from a mangrove wetland in the Luoyang River estuary, Fujian Province (24.94°N, 118.67°E). Specimens present in the surface layer sediment to a depth of 0–5 cm. Total nitrogen: 1.31 mg /g; total phosphorus: 0.40 mg /g; total organic carbon: 1.72%.

Etymology: The species name refers to its first sampling location, Luoyang River.

Diagnosis: Body cylindrical ( Fig. 1A ), tapering acutely at posterior extremity, length 0.87–1.2 mm, with maximum body diameter 55–77 μm (a = 15.7–19.3). Cuticle annulated, about 6 annulus per 10 μm, and has homogeneous punctations with lateral differentiation of two longitudinal rows of coarse dots which begins at 5–7 μm from anterior end and the distance between these two longitudinal rows gradually widens from head to mid-body part and then narrows to the tail ( Figs. 1B , 2A–D ), except the terminal of tail about 8–12 μm without punctations nor lateral differentiation ( Fig. 2B, D ). Somatic setae exist near the two rows of dots. Amphids not observed. Body anterior end slightly rounded, separated from rest of body by a collar (groove). Inner and outer labial sensillae inconspicuous. Four cephalic setae inserted on collar ( Figs. 1B , 2A ), length approximate 1.9–2.3 μm. Buccal cavity with an S-shaped hollow dorsal tooth, apical end of tooth hook-like. Sclerotized transverse ridges occur near the dorsal tooth ( Figs. 1C , 2C ). Pharynx cylindrical with anterior slightly swelling 19–23 μm in stomatal region and gradually enlarging posterior to be double well developed pharyngeal bulbs ( Figs. 1D , 2A, 2C ). The pharyngeal posterior double bulb 45–69 μm, pearshaped with a constriction to split it into two parts, anterior part width 27–39 μm and posterior part width 31–44 μm. Cardia small, surrounding by intestine. Ventral gland cell large, located posterior to the terminal pharyngeal bulb, excretory pore opening at the collar through a slender duct. Nerve ring located at 52%–57% of pharynx, 65–80 μm from anterior end. Two tail setae present, tail conical with prominent spinneret, length 114–144 μm. Spinneret finger-like, neither somatic setae exist nor annulated.

Male: reproductive system monorchic with outstretched testis located to the right of intestine. Spicules slender, arch-like, proximal with a slightly waved, middle curved, distal pointed, 33–43 μm length along arc. Gubernaculum rod-like, length 12–17 μm ( Figs. 1E , 2B ). Precloacal supplements absent.

Female: reproductive system with two opposed, reflexed ovaries, the anterior one located to the right of intestine, and the posterior one to the left ( Figs. 1F , 2E ). The Vulva located approximate at 46.1%–47.6% body length from cephalic part.

Juvenile: length 461 μm, with maximum body diameter 29 μm (a = 15.8). Without lateral differentiation ( Fig. 1G ). Other main characteristics are shared with adult except reproductive system.

Distribution: P. luoyang sp. nov. occurs within the mangrove wetlands of the Luoyang River estuary, the Jiulong River estuary (Fujian Province), the Neilingding Futian National Nature Reserve, Shenzhen City (Guangdong Province), and the Xinying Port, Danzhou City (Hainan Province) in China.

Ecological note: Due to the relationships between specific nematode and mangrove species, it is important to understand the dispersal mechanism of free-living marine nematodes and their impact on nutrient cycling in the food web. Hence, the composition of mangroves species was recorded from each sampling site. Acanthus ilicifolius , Aegiceras corniculatum , Avicennia marina , and Kandelia obovata were recorded in Luoyang River estuary, Quanzhou Bay, Fujian Province. Kandelia obovata was recorded in the Jiulong River estuary, Fujian Province. Bruguiera gymnoihiza , Kandelia obovate and Acanthus ilicifolius were recorded in Guangdong Neilingding Futian National Nature Reserve, Shenzhen City, Guangdong Province. Bruguiera sexangula was recorded in Xinying Port, Danzhou City, Hainan Province.

DNA sequence results: A 294 base pair (bp) fragment of COI, a 264 bp fragment of 18S rDNA and a 302 bp fragment of 28S rDNA were used in this study. Therefore, the combined dataset consisted of 860 bp for phylogenetic analysis. “N” denotes a lack of fragments for said species. The Bayesian topology was identical for each species, strongly supporting monophyly with strong nodal support (0.99–1 posterior probability) ( Fig. 3 ). The genetic results complement morphological evidence of P. luoyang sp. nov. being a distinct species. Interspecific and intrageneric thresholds of K2P distance divergence were as follows: 0–0.4% and 9.3%–18.4% for COI; 0 and 1.6%–4.4% for 18S rDNA; 0–1% and 8.9% for 28S rDNA, respectively.

Measurements: Holotype and a female paratype are present as follows. Detailed information of individual measurements are shown on the table 3.

Key to genus Ptycholaimellus Cobb, 1920 from China with the new species

1 Presence of ocelli at anterior end of body .................................. 2

- Absence of ocelli at anterior end of body .................................. 3

2 Cervical region abruptly narrowing, cephalic setae 1/4 h.d. long ..................................................................................... P. ocellatus

- Cervical region not abruptly narrowing, cephalic setae 2/3 h.d. long ............................................................................... P. adocius

3 Body slimmer, width less than 50 μm ........................................ 4

- Body stout, width more than 50 μm ............... P. luoyang sp. nov.

4 Double pharyngeal bulb shorter than 40% of pharyngeal length .. ..................................................................................................... 5

- Double pharyngeal bulb longer than 40% of pharyngeal length ... ................................................................................ P. longibulbus

5 Cuticle with only two lateral longitudinal rows of double dots .... ............................................................................ P. macrodentatus

- Cuticle with six longitudinal rows of double dots ............ P. pirus

Figures

Fig. 1. Ptycholaimellus luoyang sp. nov. A, adult male under stereo microscope; B, lateral view of head, showing cephalic setae and lateral differentiation; C, lateral view of male head end, showing S-shaped dorsal tooth; D, double pharyngeal bulbs; E, lateral view of male body part, showing spicules and gubernaculum; F, lateral view of female body part, showing vulva and reflexed ovaries; G, lateral view of juvenile without lateral differentiation. Scale bars, A = 200 μm; B, D, E, G = 20 μm; C = 10 μm; F = 100 μm.

Fig. 2. Ptycholaimellus luoyang sp. nov. A, lateral view of male head end; B, lateral view of male tail region; C, lateral view of female head end and double pharyngeal bulbs; D, lateral view of female tail region; E: lateral view of female body part, showing ovaries. Scale bar: A–D = 50 μm; E = 125 μm.

Fig. 3. Phylogenetic tree from MrBayes analysis of combined data set (860 bp from three genes). The branches of the new species are strongly supported by BI (PP> 0.90).