Cholomyzon multisetum, Uyeno & Johnsson, 2018

Uyeno, Daisuke & Johnsson, Rodrigo, 2018, Two new species of Siphonostomatoida (Copepoda) found on cnidarians in Tokara Islands, Southern Japan, Journal of Natural History 52 (41 - 42), pp. 2639-2652 : 2641-2644

Cholomyzon multisetum sp. nov.

( Figures 1 , 2 )

Type material

Holotype adult female (NSMT-Cr 25851), ex Tubastraea coccinea Lesson, 1829 (Hexacorallia: Scleractinia : Dendrophylliidae ), in Nishinohama Port (29°59 ʹ N, 129°54 ʹ E), Kuchino-shima Island, Tokara Islands, Japan, 2 m depth, 28 August 2015, leg. D. Uyeno. Paratype: 1 adult female (NSMT-Cr 25852), sampling data same as holotype.

Description of adult female

Body ( Figure 1 (a)) 896 long. Prosome 637 long, comprising cephalothorax and three free thoracic somites. Cephalothorax ( Figure 1 (a)) round, wider than long, 518 × 593, flattened dorsoventrally, with pair of protruded posterolateral corner. Second to fourth pedigerous somites ( Figure 1 (a)) wider than long; fourth pedigerous somite bearing pair of round posterolateral lobes with median notch ( Figure 1 (c)). Urosome comprising fifth pedigerous somite, genital double somite and abdominal somites. Genital double somite ( Figure 1 (a)) wider than long, 113 × 176. Abdomen composed of two free post genital somites, 77 × 95 and 70 × 68, respectively. Caudal ramus ( Figure 1 (b)) 0.80 times long than wide, 18 × 23, with six setae.

Rostral area with round margin without apex. Antennule ( Figure 1 (d)) 11-segmented, armature formula 1 + 1 aesthetasc, 1 + 1 aesthetasc, 11 + 1 aesthetasc, 3 + 1 aesthetasc, 4 + 1 aesthetasc, 1 + 1 aesthetasc, 2 + 1 aesthetasc, 3, 2, 3, and 7 + 1 aesthetasc; all setae naked. Antenna ( Figure 1 (e)) composed of coxa, basis, and 2-segmented endopod; coxa unarmed; basis bearing row of hairs; proximal endopodal segment bearing row of spinules and distal segment with terminal slightly curved claw. Mandible ( Figure 1 (f)) biramous; elongate stylet bearing 13 teeth on distal tip ( Figure 1 (g)); slender 1-segmented palp bearing long seta with row of fine spinules on inner margin. Oral cone ( Figure 1 (a)) conical. Maxillule ( Figure 1 (h)) bilobed with inner lobe (endite) bearing four distal setae and row of spinules and outer lobe (palp) bearing three setae. Maxilla ( Figure 2 (a)) composed of syncoxa and claw; syncoxa robust, unarmed; claw proximally robust, slender and elongate after patch of hair medially located, row of spinules posteriorly. Maxilliped ( Figure 2 (b)) subchelate, comprising syncoxa, basis, and unsegmented endopod bearing single median and distal elements and claw.

Legs 1 to 3 ( Figure 2 (c–e)) biramous; both rami bearing 3-segmented rami. Leg armature formula as follows:

Intercoxal sclerites ( Figure 2 (c–e)) of legs 1 to 3 unarmed. All spines bearing serrated margins. Basis of leg 1 bearing row of spinules on base of thick seta and inner protrusion. Both rami of legs 1 to 3 bearing rows of spinules on outer margins. Leg 1 ( Figure 2 (c)) bearing distal pointed process on outer margin of second and third endopodal segments. Legs 2 and 3 ( Figure 2 (d,e)) bearing pointed process on outer margins of all exopodal and second and third endopodal segments. Third endopodal segments of legs 1 to 3 ( Figure 2 (c–e)) bearing medial pointed processes on position of outer seta. Leg 4 absent. Leg 5 ( Figure 2 (f)) represented by constricted protrusion with two setae. Leg 6 ( Figure 1 (c)) represented by two protrusions with distal seta.

Variability

The morphology of the female paratype as in the holotype. The measurements of the body parts (n = 1) are as follows: body length 847; cephalothorax length 487; cephalothorax width 574; prosome length 620; genital double somite length 112; genital double somite width 150; first urosomite length 77; first urosomite width 103; anal somite length 63; anal somite width 72; caudal ramus length 15; caudal ramus width 23. Caudal ramus 0.66 times longer than wide.

Remarks

Cholomyzon multisetum sp. nov. differs from C. brevisetigerum Humes, 1997 and C. tubastraeae by the following: third, fourth and fifth segment of the antennule of the female bearing 11, three, and four setae, respectively (vs. seven, two, and two setae); the maxillule bearing the outer lobe with four setae (vs. three setae); distal endopodal segments of legs 2 and 3 bearing five and two elements, respectively (vs. six and three elements, respectively) (see Humes 1997b; Cheng et al. 2011). The new species is also differentiated from C. palpiferum Stock and Humes, 1969 by the following characters: absence of leg 4 (vs. represented by thumb-shaped process with two setae); distal endopodal segments of legs 2 and 3 bearing five and two elements, respectively (vs. six and three elements) (see Stock and Humes 1969).

Etymology

The specific name of the new species ‘ multisetum ’ refers to the antennule of the new species bearing more setae than congeners.

Newly established Japanese name

‘Iboyagi-gakure-kudakuchi-mijinko-ka’ for the family, ‘Iboyagi-gakure-kudakuchi-mijinkozoku’ for the genus, and ‘Iboyagi-gakure-kudakuchi-mijinko’ for the species.

Figures

Figure 1. Cholomyzon multisetum sp. nov., adult female, NSMT-Cr 25851. (a) habitus, dorsal; (b) abdomen and caudal rami, dorsal; (c) right genital opening, dorsal; (d) right antennule, posterior; (e) left antenna, anterior; (f) right mandible, anterior; (g) distal teeth of left mandible; (h) right maxillule, posterior. Scale bars: (a) 200 μm; (b, d, e, f, h) 50 μm; (c) 30 μm; (g) 10 μm.

Figure 2. Cholomyzon multisetum sp. nov., adult female, NSMT-Cr 25851. (a) right maxilla, posterior; (b) right maxilliped, anterior; (c) right leg 1, anterior; (d) right leg 2, anterior; (e) right leg 3, anterior; (f) left leg 5, ventral. Scale bars: (a, b) 50 μm; (c–e) 30 μm; (f) 10 μm.