Merlionia zeeae Uyeno & Hashimoto & Watanabe 2023, gen. et sp. nov.
Creators: name: Uyeno, Daisuke
name: Hashimoto, Rina
name: Watanabe, Hiromi K.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Copepoda
Cyclopoida
Anthessiidae
Merlionia
Merlionia zeeae

description: Merlionia zeeae gen. et sp. nov.
(Figs 2–5)
ZooBank registration: urn:lsid:zoobank.org:act: A84151CD -C746-42FB-BFE7-532621A8F7CA
Type material: Holotype: adult female (ZRC 2023.0305), ex Ichthyscopus lebeck Bloch & Schneider, 1801 (Actinopterygii: Perciformes: Uranoscopidae), 170.0 mm standard length (SL), off Tanah Merah Beach (1°18ʹN, 103°59ʹE), Singapore, Johor Strait, at a depth of ~ 1.2 m, 5 July 2019 (Fig. 6). Allotype: adult male (ZRC 2023.0306), with collection data same as that of holotype. Two adult females and one adult male paratype (ZRC 2023.0307), with collection data same as that of holotype.
Etymology: The specific name ‘ zeeae ’ refers to Dr Zeehan Jaafar, for her great contribution to our study as one of the Principal Investigators of Singapore Marine Fishes Expedition 2019.
Description: Female holotype: body elongate cyclopiform (Fig. 2A–C), 3368 long, composed of cephalosome, first to fifth pedigerous somites, genital double somite and three-segmented abdomen. Cephalosome (Fig. 2A–D) longer than wide, 600 × 573, bearing dorsal chitinous frame, separated by constriction from the first pedigerous somite; rostral area (Fig. 2D) with small apex in between antennae. Prosome 2120 long. First to fourth pedigerous somites gradually narrower posteriorly. Genital double somite (Fig. 2E–G) composed of wide anterior part and narrow posterior part, 383 × 373, bearing pair of posterolateral lobes; dorsal boundaries to fifth pedigerous and first abdominal somites distinct; genital openings situated dorsolaterally, bearing irregular protrusions on margins. Abdomen composed of three free somites, 185 × 208, 143 × 188 and 133 × 170, respectively (Fig. 2E). Caudal rami (Fig. 2E, H) 7.83 times longer than wide, 450 × 58, with one outer and five distal setae. Egg sac (Fig. 2A) multiseriate.
Antennule (Fig. 3A, B) five-segmented, angled between fourth and fifth segments; armature formula 3, 18, 5, 4, 11; all setae naked. Antenna (Fig. 3C) two-segmented, composed of coxobasis and endopod; coxobasis short, bearing one element; endopodal segment represented by an uncinate claw with two basal elements, accessory subdistal process, and pointed distal tip with hood (Fig. 3D). Labrum (Fig. 3E) bilobed, with median incision, and lamellar on posterior margin; posterolateral lobes bearing small spinules. Mandible (Fig. 3F) two-segmented, composed of unarmed coxa and gnathobase bearing two long setiform flagella covered with numerous spinules, two spines and row of fine spinules. Maxillule (Fig. 3G) knob-like and bifid; inner tip with one small seta; outer tip with three unequal setae. Maxilla (Fig. 3H) composed of unarmed syncoxa and basis tapering into blunt tip covered with numerous spinules bearing two elements. Labium (Fig. 3I) lobate, bearing pair of protuberances. Maxilliped absent.
Legs 1–4 (Fig. 4A–D) biramous; both rami three-segmented. Leg armature formula shown in Table 2. Intercoxal sclerites of legs 1–4 rod shaped, bearing pair of conical pointed processes near connecting parts to coxae.
Inner coxal setae of legs 1–5 0.88, 0.78, 0.99 and 1.10 times longer than coxae of legs 1–5, respectively. All spines serrated and all setae plumose, except naked outer setae on bases. All endopodal segments bearing pointed processes on outer distal ends. Leg 5 (Fig. 4D, E) two-segmented; proximal segment unornamented, fused to pedigerous somite; distal segment rod shaped, bearing one outer spine and with two spines and one simple seta on distal tip. Leg 6 not observed.
Adult male: body (Fig. 5A) cyclopiform, 2156 long, composed of cephalosome, second to fifth pedigerous somites, genital somite and five-segmented abdomen. Cephalosome (Fig. 5B) wider than long, 366 × 454, bearing dorsal chitinous frame; rostral area (Fig. 5B, C) irregularly protruded, wrinkled. Prosome 1045 long. Genital somite (Fig. 5A, D) wider than long, 163 × 223, with paired opercula with posterior protrusion. Abdomen (Fig. 5A) composed of four free somites, 150 × 171, 159 × 162, 130 × 135 and 102 × 123, respectively. Caudal rami (Fig. 5A) 7.88 times longer than wide, 355 × 45; armature as in female.
Antennule (Fig. 5E) five-segmented; armature formula 3, 16, 5, 4, 11; all setae naked. Antenna, mandible, maxillule and maxilla as in female. Maxilliped (Fig. 5F) subchelate, five-segmented; first segment (syncoxa) small, unarmed; second segment (basis) robust, bearing two setae on anterior margin and rows of fine spinules on posterior surface; third segment (proximal endopodal segment) unarmed; fourth segment (middle endopodal segment) bearing a single seta and pointed projection; fifth segment (distal endopodal segment) forming a terminal claw, bearing two tips and one subdistal conical process and a marginal row of spinules on inner margin.
Armature formula of legs 1–5 as in female. Leg 6 (Fig. 5D) represented by genital flap without armature.
Variability: morphology of the female paratypes as in the holotype. The measurements of the body parts (N = 2) are as follows: body length, 3669–4077 (3873 ± 288); cephalothorax wider than long, 800–869 (835 ± 49) × 672–728 (700 ± 39); prosome length, 2538–2823 (2681 ± 201); genital double somite 354–455 (405 ± 72) long and 377–415 (396 ± 27) wide; first and second urosomites and anal somite length and width as follows: 155–177 (167 ± 14) × 200–251 (225 ± 36), 149–166 (158 ± 12) × 180–231 (205 ± 36) and 114–115 (115 ± 1) × 178–198 (188 ± 14); Caudal ramus 6.63–7.40 (7.01 ± 0.55) times longer than wide, 455–489 (472 ± 24) × 62–74 (68 ± 9). Morphology of the male paratype as in the allotype. The measurements of the body parts (N = 1) are as follows: body length, 2452; cephalothorax wider than long, 438 × 534; prosome length, 1232; genital somite wider than long, 178 × 218; first to third urosomites and anal somite length and width as follows: 157 × 172, 172 × 154, 134 × 134 and 97 × 135; caudal ramus 6.80 times longer than wide, 366 × 54.
Attachment site: Gill cavities.
description: Published as part of Uyeno, Daisuke, Hashimoto, Rina & Watanabe, Hiromi K., 2023, What causes transformation of the parasitic copepod? A new example of host switching in the family Anthessiidae (Cyclopoida) from Singaporean waters, with the proposal of a new genus, pp. 216-227 in Zoological Journal of the Linnean Society 199 (1) on pages 218-224, DOI: 10.1093/zoolinnean/zlad033, http://zenodo.org/record/8328924