Pusanomyicola, Lee & Chang & Kim, 2022

Lee, Jimin, Chang, Cheon Young & Kim, Il-Hoi, 2022, Symbiotic copepods (Cyclopoida and Siphonostomatoida) collected by light trap from Korea, ZooKeys 1115, pp. 1-71 : 1

Pusanomyicola gen. nov.

Diagnosis.

Male. Body narrow, cyclopiform, clearly segmented. Prosome consisting of cephalosome and four pedigerous somites. Urosome six-segmented. Caudal ramus with six setae, Antennule seven-segmented, heavily armed with setae and aesthetascs; first and second segments with multiple aesthetascs. Antenna three-segmented, consisting of coxobasis and two-segmented endopod, and terminated in single, strong claw. Labrum broader than long, with short posterolateral lobes. Mandible distally armed with three denticle-like elements, innermost one articulate at base. Maxillule as lobe tipped with two setae. Maxilla as lobe tipped with single seta. Maxilliped four-segmented; armature formula 0, 2, 0, and 1; terminal claw reduced, rudimentary. Legs 1-4 biramous, with three-segmented rami. Coxa of all swimming legs with small inner seta. Leg 1 lacking inner distal armature element on basis. Second endopodal segment of legs 2-4 armed with two inner setae. Third endopodal segment of legs 2 and 3 armed with three spines plus three setae (formula I, II, 3). Third exopodal segment of legs 3 and 4 armed with three spines plus five setae (formula II, I, 5). Leg 5 consisting of protopod and exopod; protopod well-defined from somite; exopod armed with three setae. Leg 6 represented by three setae on genital operculum.

Type species.

Pusanomyicola sensitivus gen. nov., sp. nov. (original designation).

Etymology.

The generic name is the combination of “Pusan”, the type locality of the type species, and Myicola , the type genus of the family. Gender masculine.

Remarks.

Boxshall and Halsey (2004) recognized eight genera in the family Myicolidae , including the highly transformed genus Crucisoma Kabata, 1981. While establishing the family Anthessiidae , Humes (1986) excluded Conchocheres Sars, 1918 from this family due to the lack of long elements on the mandible, the absence of the maxilliped in the female, and the presence of three setae only on the exopod of leg 5, but he did not determine the familial position of Conchocheres . Boxshall and Halsey (2004) tentatively placed Conchocheres in the Myicolidae on the basis of similarities in the armature of the antenna and in the form of the caudal rami, but they mentioned that the genus differed from all myicolids in the absence of the inner seta on the basis of leg 1, a characteristic found in the Anthessiidae .

It is notable that one typical feature of the Anthessiidae is in the antennule. In poecilostome cyclopods, the armature of three terminal segments of the antennule (4+aesthetasc, 2+aesthetasc, and 7+aesthetasc) is generally determined as early as the copepodid II stage, and this armature formula remains unchanged throughout subsequent developmental stages. However, the position of the aesthetasc on the antepenultimate segment (the segment of 4+aesthetasc) differs between the Anthessiidae and other poecilostome families, since the aesthetasc in the Anthessiidae is inserted at the distal corner, accompanied with anterodistal seta (Fig. 15B ), whereas it is inserted near the proximal seta (Fig. 15A ) in other poecilostome families, such as the Myicolidae , Clausidiidae , Ergasilidae , and lichomolgoid families. Pusanomyicola gen. nov. and Conchocheres share the armature pattern of the latter poecilostome families.

Pusanomyicola gen. nov. is more similar to Conchocheres than to any other known genera of the Myicolidae ; their shared features are the unsegmented maxilla bearing a single distal element, the absence of the inner distal element on the basis of leg 1, and the possession of only three setae on the exopod of leg 5. Nevertheless, Pusanomyicola gen. nov. cannot be considered congeneric with Conchocheres due to their significant differences on the generic level, as follows: (1) the male urosome is five-segmented in Conchocheres malleolatus Sars, 1918, the type and only species of Conchocheres , while it is six-segmented in Pusanomyicola sensitivus gen. nov., sp. nov.; (2) the male antennule of C. malleolatus bears five aesthetascs as illustrated by Sars (1918), but as many as 28 aesthetascs in P. sensitivus gen. nov., sp. nov.; (3) the male maxilliped of C. malleolatus bears a large terminal hook, while it is markedly reduced in P. sensitivus gen. nov., sp. nov.; (4) the third exopodal segment of leg 1 is armed with three spines plus four setae (II, I, 4) in C. malleolatus , but with four spines plus four setae (III, I, 4) in P. sensitivus gen. nov., sp. nov.; and (5) the third endopodal segment of leg 4 is armed with one spine plus three setae (I, 3) in C. malleolatus , but with three spines plus two setae (I, II, 2) in P. sensitivus gen. nov., sp. nov.

We place Pusanomyicola gen. nov. in the Myicolidae on the basis of its myicolid form of antenna bearing a single robust terminal claw and a truncate inner distal seta on the terminal segment, the presence of a group of spinules on the labrum, maxilla and genital operculum, and the myicolid form mandible. We confirm that Conchocheres , which shares important character states with Pusanomyicola gen. nov., is placed in the Myicolidae , as well.

Figures

Figure 15. Antennule of copepodid II stage of Critomolgus anthopleurus Kim (A) and Anthessius dolabellae Humes & Ho, 1965 (B). Scale bars: 0.02 mm. A redrawn from Kim (2003).