Caprella perplexa, Peart & Woods, 2025

Caprella perplexa sp. nov.

( Figs. 1 View FIGURE 1 , 9–11 View FIGURE 9 View FIGURE 10 View FIGURE 11 )

Type material. Holotype: NIWA 155325 View Materials , male (9.5 mm), KAH1706/ Grab 34A/67.19, Spirits Bay, Northland, North Island, New Zealand, 34°23.7402’S 172°48.978’E, 32 m, 2/06/2017, NIWA GoogleMaps . Paratypes: NIWA 155326 View Materials , female (6 mm) ; NIWA 155327 View Materials , 17 specimens (females, males, juveniles, 3–8 mm), same collection data as the holotype GoogleMaps .

Other material examined. NIWA 155328 View Materials , 1 juvenile (3 mm) , KAH1706/ Grab 4A.1/17/41, Piwhane / Spirits Bay, Northland, North Island, New Zealand, 34°21.54’S 172°45.3498’E, 51 m, coll GoogleMaps . NIWA, 30/05/2017 ; NIWA155329 View Materials , 4 juveniles (3–4 mm) , KAH1706/ Grab 36A.1/69.2, Spirit’s Bay, Northland, North Island, New Zealand, 34°23.718’S 172°46.818’E, 31 m, coll GoogleMaps . NIWA, 02/06/2017 ; NIWA 155330 View Materials ( MITS75145 ), OPX30232, Russell , Bay of Islands, North Island, New Zealand, 35°15.7187’S 174°7.2492’E, 0–1 m, collected from a pontoon, coll GoogleMaps . NIWA, 13/11/2019 .

Type locality. Piwhane/Spirits Bay, North Island, New Zealand.

Etymology. The species name, perplexa , refers to the nature of the complex of species associated with Caprella equilibra Say, 1818 to which this new species belongs. It is a Latin adjective used to indicate something is complicated.

Diagnosis. Head rectangular, without projection; body smooth and robust. Antenna 1 over half body; peduncle articles 1–2 slender in male and female, sparsely setose, subequal in length to flagellum. Antenna 2 reaching to ⅓ length of article 3 of peduncle of antenna 1, bearing long dense setae on ventral margin. Gnathopod 1 robust, with palmar margin of propodus setose with proximal robust seta; palm straight; dactylus inner margin serrate. Gnathopod 2 in male arising at distal one-third of pereonite 2; basis approximately ½ length of propodus and halflength of pereonite 2; palmar region of propodus straight, weakly setose with posterior corner subacute bearing robust seta, large subquadrate tooth predactylar and secondary tooth of same length just posterior to predactylar tooth; dactylus strong, apex pointed and unconstricted with distal end smooth. Gnathopod 2 in female inserted midpoint on pereonite 2; palm of propodus convex. Gills long and slender in both sexes. Pereopods 5–7 increasing in length posteriorly; palmar margin of propodus concave bearing short dense setae with two median grasping spines and expanded posterior corner.

Description. (Based on holotype male, 9.5 mm, NIWA 155325). Body. Head anterodistal margin rectangular, not produced forward. Head fused with pereonite 1, suture present and visible. Pereonites no dorsal projections; only slight posterior pointing lateral projections on pereonite 2 at gnathopod insertion point, all other pereonites without lateral projections. Ratio of lengths pereonites 1 (not including head)—7 1: 1.7: 1.3: 1.2: 1.2: 0.8: 0.5. Head. Antenna 1 0.65 × body; peduncular article 2 longest, 1.75 × article 1, 1.3 × article 3; flagellum 0.7 × peduncular length with 16 articles. Antenna 2 0.45 × antenna 1 length, peduncular article 4 subequal to article 5.

Mouthparts: upper lip deeper than wide, bilobed, setose. Lower lip, inner lobe round, significantly shorter than outer lobes. Mandible left incisor with 5 teeth, lacinia mobilis with five teeth followed by three plumose setae, molar distinct, bladed. Maxilla 1 outer plate with seven stout apical setal-teeth; palp two-articulate; article 2 longer than article 1 (4.5 ×) with 10 lateral slender setae and single line of apical robust setae. Maxilla 2 inner plate, oval, with ca. 15 setae; outer plate with ca. 15 apical setae, outer plate longer than inner plate. Maxilliped inner plate (basal endite) with two stout setae on inner half of distal margin, with line of setae on entire distal margin; outer plate (ischial endite) 2.0 × inner plate (basal endite) with five well-spaced robust setae on inner margin, with row seven medial slender setae; palp 4-articulate, article 2 longest, setose along entire inner margin; article 3 2.0 × article 1, setose on lateral to distal part, and medially; dactylus inner and medial surfaces setose with fine hairs; dactylus same length as article 3.

Gnathopod 1 basis subequal to ischium, merus, carpus combined; carpus subtriangular, densely setose, posterior lobe broadly rounded; propodus triangular, length 1.4 × width (at widest point), setae on medially; palm beginning close to posterior margin; proximal projection equipped with robust seta followed by many slender setae of varying lengths along palm; dactylus weakly curved, inner margin with small setae, tip bifid. Gnathopod 2 basis with anterodistal triangular projection, with bifid corner; ischium 0.2 × basis, without distal triangular projection; propodus longer than wide (length 1.7 × width); palm beginning approximately ⅓ along posterior margin, proximal projection with single robust seta followed by one slender seta; palm with predactylar subquadrate projection with grinding surface preceded by rounded excavation and narrower, rounded tooth almost as long as predactylar tooth, sparse slender setae along palm. Gill 3 length 0.5 × pereonite 3, elongate; gill 4 subequal with gill 3. Pereopod 5 basis 0.6 × propodus, with small bifid, distal projection; ischium 0.3 × basis; merus 1.0 × basis; carpus 1.0 × basis, setose along distal inner margin; propodus longest, with paired, combed robust setae on posteroproximal corner, 0.3 along posterior margin, propodus twice as long as wide (at posteroproximal corner); palm concave with sparse slender setae along margin; dactylus strongly curved. Pereopod 6 longer than pereopod 5 (1.3 × longer). Pereopod 6 shorter than pereopod 5, but with similar proportions and shape. Pereopod 7 same length as pereopod 6. Penis short. Uropod 1 vestigial with 3 lateral setae. Uropod 2 vestigial.

Paratype mature female, NIWA 155326, 6 mm. Ratio of lengths pereonites 1 (not including head)—7 1: 4: 3: 3.1: 3: 2: 1.7. Antenna 1 peduncular article 2 longest 1.75 × article 1, 1.6 × article 3; flagellum 1.1 × peduncular length with 12 articles. Antenna 2 0.35 × antenna 1 length. Gnathopod 2 inserted halfway along pereonite 2; basis 0.30 × pereonite 2 length; palm beginning ⅓ along posterior margin.

Ecology. This species was reported from grab samples from a benthic survey from depths of 31– 52 m. The exact habitat is not known.

Distribution. North Island, New Zealand.

New Zealand biosecurity status. Native.

Remarks. Caprella perplexa sp. nov. is closely related to the seemingly cosmopolitan species, Caprella equilibra Say, 1818 . It is highly doubtful, however, that C. equilibra is a true cosmopolitan species. Even though there are numerous comments on the globally conservative nature of the morphology of this species, both morphological and molecular information is provided to suggest that this is in fact a species complex. Caprella perplexa sp. nov. is morphologically similar but does differ from Say’s original description by the position of the gnathopod 2 (positioned in the first third of the body, as opposed to halfway). Caprella equilibra was first recorded in New Zealand waters by Thomson & Chilton (1885).

Caprella novaezealandiae was synonymised with C. equilibra by Thomson & Chilton (1885) (but was removed by McCain 1968). Chilton was notorious for assigning northern hemisphere names to geographically disparate, but morphologically similar species. There are three ( Caprella manneringi , C. perplexa sp. nov. and C. sarahae sp. nov.), and potentially more, species involved in the C. equilibra complex in the New Zealand region. There is also doubt as to whether C. equilibra sensu stricto occurs in the New Zealand region at all. A detailed collection and analysis programme, with both detailed morphological and molecular analysis throughout the New Zealand region is recommended for an accurate picture of this complex. These species generally all have an elongated pereonite 1 and 2, elongated gnathopod 2, and a ventral acute projection on pereonite 2. The differences between these species are compared to other significant records of the C. equilibra complex ( Table 3). Caprella perplexa is closest to C. sarahae sp. nov. but they differ mainly by the proportion and shape of antenna 1 (flagellum long and narrow in C. perplexa , short and robust in C. sarahae ), the gnathopod 1 merus posterior lobe broadly rounded ( C. perplexa ) and subacute and narrow ( C. sarahae ), pereonite 6 longer than 7 ( C. perplexa ), and the same length ( C. sarahae ).

There were difficulties with securing molecular sequences for the material (old material originally rinsed in formalin). Caprella manneringi is predominantly found on asteroids in the subantarctic, C. sarahae has a wider distribution (see species notes) whereas C. perplexa seems to be more restricted to the northern region of the North Island.