Paranotodelphys saccata Stock, 1967

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 : 48-49

Paranotodelphys saccata Stock, 1967

( Fig. 29 )

Material examined. 1 ♀ (dissected) from Polycarpa sp., Red Sea, collected during the 19 th Century.

Supplementary description of female. Body ( Fig. 29A ) 3.68 mmlong. Prosome 5-segmented, but articulations between somites obscure, represented by transverse constrictions. First to third pedigerous somites without defined epimera. Brood pouch large, completely incorporatingfifthpedigeroussomiteandcomprisingmore than half of total body length. Freeurosome ( Fig. 29B ) 5-segmented, graduallynarrowingposteriorly; somites 136×248, 161×230, 152×220, 121×196, and 94×162 μm, respectively. Caudalramus ( Fig. 29C ) tapering, about 2.2 times as long as wide (109×49 μm), armed with 6 setae; all setae short (= less than width of ramus); outer lateral seta positioned at 48% of ramus length.

Rostrum ( Fig. 29D ) slightly longer than wide, weakly tapering, with rounded distal margin. Antennule ( Fig. 29E ) 9-segmented; segmental fusion pattern as in generic diagnosis; first 2 segments broader than more distal segments; third segment ( XII-XIV) with trace of articulation on one surface; armature formula 3, 20, 7, 6, 4, 4+aesthetasc, 4, 4+aesthetasc, and 7+aesthetasc; all setae naked except 2 on first segment. Antenna ( Fig. 29F ) robust, consisting of coxa, allobasis and compound endopodal segment; coxashortand unarmed; allobasis inflated, convex along inner margin and ornamented with 2 transverse rows of setules on inner side: exopod represented by 1 pinnate seta and 1 short naked seta (short seta 0.6 timesas long as longer one); compound endopodal segment about 2.5 times as long as wide (68×27 μm), armed with terminal claw and 11 setae (arranged as 1, 4, 1, 2, and 3), pinnate outer subdistal seta conspicuously broader than other setae; terminal claw more than half length of segment.

Labrum hirsute on subdistal and distal surfaces, with slightly concave posterior margin. Mandibular basis fused with first endopodal segment, setulose along outer margin, with 1 seta at middle of medial margin and 2 setae at inner-distal corner; free second endopodal segment armed with 8 setae; exopod with 5 setae, distalmost seta much larger than other 4. Maxillule ( Fig. 29G ) with 9 setae on arthrite, 1 on coxal endite, 2 on epipodite, 3 on medial margin of basis (proximal 2 small), 4 on small exopod, and 6 on endopod; endopod subdivided into proximal part bearing 2 medial setae and short distal part bearing 4 setae. Maxilla 5-segmented; syncoxawith 10 enditic setae grouped 4, 1, 2, and 3; basis with 3 setae, distal seta stiff; endopod armed with 1, 1, and 3 setae on first to thid segments, respectively. Maxilliped ( Fig. 29H ) armedwith 9, 0, and 3 setae on first to third segments, respectively; second segment with bulbous swelling distally; third segment small, obscurely articulated at base.

Legs 1–4 with 3-segmented rami. Spines on outer margin of exopods well-developed, strong, as figured in original description ( Stock, 1967). Inner distal spine on basis of leg 1 longer than first endopodal segment. Armature formula for legs 1–4 as in generic diagnosis.

Leg 5 ( Fig. 29B ) represented by pair of small setae on ventral surface of brood pouch near base of free urosome.

Male. Not found.

Remarks. Stock (1967) stated that a patch of ‘cilia’ was found near the tip of the caudal ramus. Careful observation of our specimen, revealed this to be opaque internal tissue within the caudal ramus, rather than a patch of setules.

The interpretation of the segmentation pattern of the antennule presented here is based on setation counts as well as on comparison with the segmental fusion patterns exhibited in related species and other genera within the family Notodelphyidae ( Fig. 30 ). The setation pattern allows the segmental fusions to be elucidated in the more proximal segments up to the sixth segment (which is identified as XXI-XXIII because it carries the long distal seta, articulated at its base, that is a reliable marker for segment XXIII). By comparison with congeners ( Fig. 30 ), the next two segments should be XXIV and XXV, but each carries 2 additional elements: XXIV typically has 1 anterior and 1 posterior seta (see Boxshall & Huys, 1998), butherehas 2 additionalsetaeon theanterior margin; XXV would typically carry 1 seta and 1 aesthetasc anteriorly and 1 seta posteriorly, but also carries 2 additional setae on the anterior margin. There are also 2 additional setae present on the second compound segment (III-XI) which carries 20 setae rather than a maximum of 18 as would be expected (2 each from the 9 incorporated segments), and the thirdsegment (XII-XIV) carries 1 additional seta. These appear to be novel elements since they are not present in any of the species of Notodelphys described here, nor in either of the relatively plesiomorphic new genera, Bathynotodelphys gen. nov. and Pronotodelphys gen. nov., proposed above.

Figures

FIGURE 29. Paranotodelphys saccata Stock, 1967, female. A, habitus, right; B, urosome, ventral; C, left caudal ramus, ventral; D, rostrum; E, antennule; F, antenna; G, maxillule; H, maxilliped. Scale bars: A, 0.5 mm; B, 0.1 mm; C–F, 0.05 mm; G, H, 0.02 mm.

FIGURE 30. Schematic comparison of antennular segmentation patterns in selected notodelphyid taxa. Roman numerals mark ancestral segments, Arabic numerals indicate number of setae on each segment/compound segment. ae = aesthetasc. Supernumerary setae are identified by reference to the observed maximum setal number known within the Copepoda (see Boxshall & Huys, 1998). Supernumerary setae are present on segments III–XI, XII–XIV, XV–XVI, XXIV and XXV of Paranotodelphys polycarpae, on segments III–XI, XII, XV–XVI, XXI–XXIII, XXIV, XXV and XXVI–XXVIII of P. saccata, and on segments XVII–XX, XXI–XXIII, XXIV, and XXV of Doropygopsis novemsetifera.