Pronotodelphys, Kim & Boxshall, 2020

Kim, Il-Hoi & Boxshall, Geoff A., 2020, Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata), Megataxa 4 (1), pp. 1-6 : 13

Pronotodelphys gen. nov.

Diagnosis. Female body with modified prosome comprising cephalosome, free first to third pedigerous somites (first somite largely concealed), and dorsal brood pouch incorporating fourth and fifth pedigerous somites (as typical for Notodelphys ). Freeurosome of female 5-segmented, but genital and first abdominal somites indistinctly defined. Male urosome 6-segmented. Antennule 13-segmented in female; segmental fusion pattern: I-II, III-XI, XII-XIV, XV-XVI, XVII-XVIII, XIX, XX, XXI, XXII, XXIII, XXIV, XXV, XXVI-XXVIII. Male antennule geniculate, 12-segmented; segmental fusion pattern: I-II, III-V, VI-XI, XII, XIII, XIV, XV-XVI, XVII, XVIII, XIX-XX, XXI-XXIII, XXIV-XXVIII. Antenna consistingof coxa, basis, and 2- segmented endopod; basis with 1 inner seta plus 2 outer setae representing exopod; distal endopodal segment compound. Mandible with biramous palp armed with 5 setae on exopod, and 4 + 10 setae on first and second endopodal segments, respectively. Maxillulewith 2- segmented endopod bearing 3 and 4 setae on first and second segments, respectively. Maxilla 5-segmented; syncoxa with endite formula 3 + minute seta, 1, 2, and 3; basis with clawplus 2 setae; endopod with setal formula 1, 1, and 4. Maxilliped 4-segmented; first segment with 9 setae; second segment unarmed; third and fourth segments with 5 setaein total. Legs 1–4 biramous with 3-segmented rami: armatureformula as follows:

Leg 5 with left and right protopods fused to form broad transverse plate; free exopodal segment with 2 setal elements.

Type species. Pronotodelphys caledonica gen. et sp. nov. by original designation.

Other included species: Pronotodelphys villosa ( Ooishi, 1962) comb. nov. (originally described as Notodelphys agilis villosus )

Etymology. The generic name is the combination of pro -(“before”inGreek)andthegenericname Notodelphys . It alludes to the relatively primitive features exhibited by the new genus relative to the genus Notodelphys .

Remarks. The new genus belongs in the family Notodelphyidae and is a close relative of the type genus Notodelphys . However, Pronotodelphys gen. nov. exhibits plesiomorphic states of the mandible, maxillule, and maxilliped relative to the type genus, as follows: (1) the maxillulary endopod is armed with 7 setae, whereas a maximum of 5 setae is reported from all species of Notodelphys ; (2) the maxilliped is 4-segmented and armed with 9, 0, 3, and 2, or 9, 0, 2, and 3 setae on the first to fourth segments, respectively. In contrast, the maxilliped of Notodelphys is invariably 3-segmented and is armed with between 8 and 10 setae on the first segment, a single seta on the second, and between 2 to 4 setae on the third; and (3) the mandible is armed with 10 setae on the second endopodal segment, whereas in species of Notodelphys it carries a maximum of 9 setae, with the sole exception of N. weberi Stock, 1950 which also carries 10 setae ( Stock, 1950), The combination of these differences suggests that the new genus diverged early, at the base of the lineage leading to Notodelphys and may well represent the sister group of the type genus. These differences justify the establishment of a new genus, Pronotodelphys gen. nov., distinct from Notodelphys . The fusion of the protopods of thefifthlegpairtoforma transverseplate isacharacteristic apomorphy of the new genus.

In a redescription of Notodelphys agilis villosus Ooishi, 1962 based on newly collected specimens from Korean waters, Kim (2012) elevated this subspecies to species rank, as Notodelphys villosus . In the original description of N. agilis villosus, Ooishi (1962) described the maxilliped as 3-segmented with a setation pattern of 9, 0, and 5 on the first to third segments, respectively. However, after examination of additional material, Kim (2014) recognized that the maxilliped was 4-segmented with a setation pattern of 9, 0, 3, and 2. During the course of the present study, were-examined additional material of the same species and confirmed Kim’s (2014) observations. This species shares the 4-segmented maxilliped with Pronotodelphys caledonica gen. et sp. nov., and we here transfer Ooishi’s species to the new genus as Pronotodelphys villosa ( Ooishi, 1962) comb. nov.