Bysone brevicaudatus Kim & Boxshall 2020, sp. nov.
Creators: name: Kim, Il-Hoi
name: Boxshall, Geoff A.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Copepoda
Cyclopoida
Notodelphyidae
Bysone
Bysone brevicaudatus

description: Bysone brevicaudatus sp. nov.
(Figs. 292, 293)
Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21355) from Stolonica multitestis Monniot C., Monniot F., Griffiths & Schleyer, 2001 (MNHN-IT-2008-8032 = MNHN A1/RIT/25), south of Matemo, Ibo I., Mozambique, Monniot coll., 17 November 1995.
Etymology. The specific name is derived from the Latin brev (=short) and caud (=tail) and refers to the relatively stout caudal rami.
Descriptionoffemale. Body (Fig. 292A) stout, curved ventrally. Prosome 1.40 mm long: dorsal cephalic shield clearly defined; first to fourth pedigerous somites discernible by constrictions; second and third pedigerous somites each with trace of tergite. Third and fourth pedigerous somites forming brood pouch. Free urosome (Fig. 292B) 5-segmented: genital somite well defined ventrally from preceding somite, but dorsally confluent. Anal somite about 1.5 times longer than preceding abdominal somite. Caudalramus (Fig. 292C) nearly rectangular, about 2.7 times longerthan wide (148×54 μm) and aslongas anal somite: armedwith 6 smallsetae (outer proximal, ventral, and 4 distal); all setae small, less than half of width of ramus at base; outer proximal and ventral setae located at 38 and 62% of ramus length, respectively.
Rostrum (Fig. 292D) 95×118 μm, indistinctly articulated at base tapering distally towards rounded apex. Antennule (Fig. 292E) 270 μmlong, 6-segmented; armatureformula 3, 14, 7+aesthetasc, 3+aesthetasc, 2+aesthetasc, and 9+2 aesthetascs; setae naked and short; distal seta on fourth and fifth segment annulated at base. Antenna (Fig. 292F) 4-segmented; coxa, basis, and first endopodal segment unarmed; compound distal endopodal segment about 3.1 times longer than wide (75×24 μm) and 1.3 times longerthan firstendopodal segment: armed with 1 subdistal and 3 distal setae, plus strongly curved terminal claw, about 0.65 times as long as segment.
Labrum (Fig. 292G) with concave posterior margin, pointed posterolateral corners, and broad posteromedian lobe bearing 2 denticles at apex. Mandible (Fig. 292H) withbroadcoxalgnathobasebearing 5 teethand 1 spinulelike subsidiary tooth distally at base of distalmost tooth: basis with 1 setaon medial margin; exopod as long as endopod, armed with 2 long proximal and 2 short distal setae: endopodarmedwith 2 and 5 setaeon firstand second segments, respectively; middle seta on second segment markedly longer than other 4 setae. Maxillule (Fig. 292I) with 9 setae on arthrite, 1 thin seta on coxal endite, 2 unequal setaeon epipodite, 3 unequal setae onmedial margin of basis, 3 setae distally on exopod and 2 setae distally on endopod. Maxilla (Fig. 293A) 5-segmented; syncoxa with 8 setae arranged as 3, 1, 2, and 2; basis with robust claw plus 1 seta; endopod with 1, 1, and 3 setae on first to third segments, respectively. Maxilliped (Fig. 293B) unsegmented, armed with 8 medial setae and 1 long outer seta.
Leg 1 (Fig. 293C) small, with 2-segmented rami; second segments of both rami compound, with traces of articulation; inner coxal seta pinnate; outer seta on basis much larger than that of legs 2–4; first exopodal segment lacking inner seta. Legs 2–4 each with 3-segmented exopod and 2-segmented endopod (Fig. 293D, E); both rami elongate; endopod extending to distal border of second exopodal segment; second endopodal segment about 3 times longer than first in legs 2 and 3, about 4 times longer in leg 4. Inner coxal seta present in legs 2–4, but that of leg 4 minute. Outer and distal setae on exopod of leg 2-4 short, naked, and bluntly tipped. Inner setae on exopod and all setae on endopod of leg 4 small and naked. Armature formula for legs 1–4 as follows:
CoxaBasisExopodEndopodLeg 10-11-0I-0; IV, I, 30-1; 1, 2, 4Legs 2 & 30-11-01-1; 1-1; 3, 1, 50-1; 1, 2, 5Leg 40-11-01-1; 1-1; 2, 1, 50-1; 1, 2, 4
Leg 5 (Fig. 293F) represented by small ventrodistal lobe bearing 2 small exopodal setae distally; protopodal seta lacking.
Male. Unknown.
Remarks. The genus Bysone has comprised only the type species, B. operculatus since it was originally established based on material collected in Madagascar (Stock & Humes, 1970). Bysone brevicaudatus sp. nov. shares important character states with the type species including: a 6-segmented antennule, 4 setae on the mandibular exopod, 2 and 5 setae, respectively, on the first and second segments of mandibular endopod, a 2- segmented exopod of leg 1, a similar form of maxilliped, and a similar form of the mandibular gnathobase which bears a spinule-like distal subsidiary denticle and has no proximal seta. These similarities are sufficient to confirm the placement of the new species in Bysone. The two species can be distinguished by reference to the maxilla, which has a stong claw plus a seta on the basis and the endopod is 3-segmented in the new species. In contrast, B. operculatus has the maxillary basis armed with only 2 setae and the endopod is 2-segmented. These differences in the maxilla are significant.
There are other differences between these two species: the maxilliped is armed with 9 (8+1) setae in B. brevicaudatus sp. nov. (vs. 5+1 setaein B. operculatus), the maxillulary arthrite is armed with 9 setae in B. brevicaudatus sp. nov. (vs. 5 setaein B. operculatus), the basis of leg 1 bears an outer seta (vs. seta absent in B. operculatus), the second endopodal segment of leg 1 is armed with 7 setae (vs. 6 setae), and leg 5 is short, lobate (vs. digitiform in B. operculatus). These differences are sufficient to support the establishment of the new species.
description: Published as part of 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), pp. 1-6 in Megataxa 4 (1) on pages 441-444, DOI: 10.11646/megataxa.4.1.1, http://zenodo.org/record/4591138