Zeuxoides rapaitii, Bird, 2019

Bird, Graham J., 2019, Tanaidacea (Crustacea: Peracarida) from the Southern French Polynesia Expedition, 2014. I. Tanaidomorpha, Zootaxa 4548 (1), pp. 1-75 : 57-67

Zeuxoides rapaitii n. sp.

( Figs 29–35 )

Material examined. Holotype —non-ovigerous ♀, 4.9 mm, P.98933, Stn 18.3, Pariati Bay , Rapa Iti, Austral Islands, 27° 34' 21" S 144° 22' 09" W, littoral algae, 3 October 2014, coll. A. Berthelsen, A. Reid, S.J. Keable, and S.E. Reader.

Allotype —copulatory ♂, 2.7 mm, P. 102367; details as for holotype.

Paratypes— AUSTRAL ISLANDS: one manca-II, three manca-III, seven non-ov. ♀♀, one prep. ♀ P.98953, Stn 18.2; five non-ov. ♀♀, two prep. ♀♀, one prep. ♂♂ MA73587, 15 manca-II, 13 manca-III P. 102371, 69 nonov. ♀♀ /neuters P. 102370, two prep. ♀♀, two ov. ♀♀ P. 102368, six prep. ♂♂ P. 102369, one prep. ♀ dissected on two microslides P.102372.001, one prep. ♀ (mandibles and chelipeds dissected on microslide P. 102373, P.102373.001), one prep. ♀ pleon dissected on microslide P. 102374, P.102374.001, one prep. ♂ right cheliped dissected on microslide P. 102375, P.102375.001, one cop. ♂ chelipeds and antennule dissected on microslide P. 102376, P.102376.001, one cop. ♂ P.98942, Stn 18.3.

Diagnosis. Female: Zeuxoides with antennule articles 2–3 together about half as long as article-1; terminal article very short, with 1–6 aesthetascs in females (body-size related); left mandible with triangular/subrectangular lacinia mobilis, right mandible with lacinia mobilis reduced to a small spine, both without accessory spines/setae; maxillule with eight terminal spines; cheliped fixed finger cutting edge not convex in female, with more defined proximal diastema in males; pereopod-1 coxa with cuspate apophysis, bearing five setae; pereopods 2–3 carpus with 8–10 crotchets; pereopods 4–6 carpus with 9–11 crotchets; pleopods 1–2 peduncle with one mesial and 5–6 lateral plumose setae, pleopod-3 peduncle with three outer setae; uropod with peduncle and six segments, terminal segment minute.

Male: as female but slightly dimorphic. Antennule more elongate with 7–9 distal aesthetascs. Cheliped larger and stouter than female.

Type locality. Pariati Bay, Rapa Iti, Austral Islands, 27° 34' 21" S 144° 22' 09" W, littoral algae.

Etymology. A Latin male genitive use of the island Rapa Iti.

Description. Holotype non-ovigerous female, 4.9 mm (P.98933). Habitus ( Fig. 30A–B ) fairly stout, 5.1 times ltb; pigmented brown on cephalothorax, pereonites, pleonites, and pleotelson. Cephalothorax 21% of body length (holotype), as long as pereonites 1–2 and half of pereonite-3 combined, 1.24 times ltb, with distolateral seta; setae of coxal sclerite and cheliped basis also visible from dorsal view. Pereon with pereonite-1 shortest, pereonites 2–3 subequal, pereonites 4–5 longest, pereonite-6 about length of pereonite-2, narrower than pereonite-5; all with several dorsolateral and posterolateral setae. Paratype preparatory female (P. 102374). Pleon length of pereonite-6 and half of pereonite-5 combined; pleonites 1–3 with several lateral-epimeral plumose setae (c. five, seven and three respectively) and four or five simple dorsal and dorsolateral setae, pleonites 1–2 also with group of dorsolateral plumose setae (four and three respectively); pleonites 4–5 ( Fig. 30C ) very short, pleonite-4 with two unequal dorsolateral setae and three unequal lateral setae (per margin); pleonite-5 with four unequal lateral setae (per margin). Pleotelson ( Fig. 30C ) 0.5 times as long as broad, with three unequal posterolateral setae, four unequal posterodorsal setae and one PSS (per margin), and four apical setae, the outer pair much longer.

Paratype non-ovigerous female, 4.0 mm (P.102372.001, P. 102373, P.102373.001). Antennule ( Fig. 30D ) about 0.6 times length of cephalothorax; article-1 63% of total length, 2.4 times ltb, and 2.6 times longer than article-2; article-2 1.6 times ltb; article-3 half length of article-2; article-4 very short, with six aesthetascs; other setation as figured. Antenna ( Fig. 30E ) article- 1 short, naked; article-2 about 1.5 times ltb, with dorsodistal seta, and five ventral/ventrodistal setae, dorsal margin spinulate; article-3 shorter than broad, naked; article-4 slightly longer than article-2, 2.2 times ltb, with one ventral PSS and five distal setae; article-5 0.7 times length of article-4, 1.2 times ltb, with three distal setae and three small PSS; article-6 just longer than broad, with distal corona of ten unequal setae.

(2012). Antennule articles 2– 3 v article-1: short <<0.5x, intermediate (int.) 0.5–0.75x, long>0.75x.

Mouthparts. Labrum (not figured) typical of genus, hood-like; densely setulate. Mandibles ( Fig. 31A–C ) typical, left mandible ( Fig. 31A ) lacinia subconical (fresh) or subrectangular (worn), without accessory spine; right mandible ( Fig. 31C ) incisor bifid, lacinia minute, spiniform. Labium ( Fig. 31D ) typical of genus; both lobes distally setulate, outer lobe with small setulate fused lobe (palp). Maxillule ( Fig. 31E–F ) endite with distal setules and eight terminal spines of various thickness, some weakly pectinate; palp with at least two apical setae. Maxilla ( Fig. 31G ) irregular oval, with group of 2–4 spines.

Maxilliped ( Fig. 31H–J ) typical, apex of coxa with two setae; bases together 1.2 times ltb, each with lateral margin setulate and one distal seta. Endite distally setulate, with two medial coupling hooks and two aboral setulate setae. Palp article-1 lateral margin distally setulate and with three unequal setae; article-2 with lateral seta, six distomesial smooth setae and three pectinate setae; article-3 subequal to article- 2 in size, with two rows (eight and six) mesial setae; article-4 twice as long as broad, with two subdistal seta and about eleven distal setae. Epignath ( Fig. 31K ) typical, linguiform,, apex with setulate process (not figured).

Cheliped ( Fig. 32A–B ) coxal sclerite with four unequal dorsal setae; basis posterior lobe about as large as anterior mass, latter with dorsodistal seta and ventrodistal seta; merus ventral margin twice as long as that of carpus, with three ventral setae and three dorsolateral setae near articulation with basis; carpus 1.6 times ltb, dorsal margin with one subdistal seta and distal group of two unequal setae, ventrolateral margin with four unequal setae, ventromesial with one small seta. Chela longer but narrower than carpus, 2.2 times ltb; propodus palm 1.4 times ltb, with mesial pectinate spine and three lateral setae near articulation with dactylus; fixed finger with eight ventral setae, two distomesial setae and eight lateral setae near incisive margin, incisive margin with raised laminar distal apophysis; dactylus with mesial seta, and ventral margin with row of three small spines.

Pereopod-1 ( Fig. 33A–B ) coxa with three-cuspate acuminate spur about twice as long as broad, with five setae; ischio-basis 4.7 times ltb, with four unequal superoproximal setae and inferodistal seta; merus about twice as long as broad, with single supero- and inferodistal setae; carpus subrectangular, just longer than merus, 2.2 times ltb, with two superodistal seta and two inferodistal setae; propodus as long as merus and carpus combined, 5.2 times ltb, tapering, with subdistal superior pectinate seta, one long superodistal seta and four unequal inferodistal setae; dactylus just shorter than unguis, with accessory seta, together 0.6 times as long as propodus.

Pereopod-2 ( Fig. 33C ) ischio-basis broader than in pereopod-1, 2.6 times ltb, with single superoproximal PSS, inferodistal margin with five setae; merus geniculate, 2.2 times ltb, with two superodistal setae, five inferodistal setae, inferodistal (lateral) crotchet and numerous microtrichia; carpus 0.6 times length of merus, 1.3 times ltb, with three superodistal setae, five inferodistal setae, eight crotchets and numerous microtrichia; propodus 0.6 times as wide as carpus, 1.25 times longer, with two superodistal setae (one small) and five unequal inferodistal setae, inferodistal margin near dactylus with numerous microtrichia and spinules; dactylus with accessory seta, together with unguis 0.6 times length of propodus.

Pereopod-3 ( Fig. 33D ) like pereopod-2 but ischio-basis with two superoproximal setae and a PSS; merus slightly shorter, 1.9 times ltb; carpus with four inferodistal seta and ten crotchets; propodus slightly shorter, with one superodistal seta

Pereopod-4 ( Fig. 33E ) ischio-basis broader than in pereopods 2–3, 2.8 times ltb, with six inferodistal setae; merus geniculate, 2.5 times ltb, with four unequal superodistal setae, three inferodistal setae, two inferodistal crotchets, and numerous microtrichia; carpus 0.8 times length of merus, 2.5 times ltb, with four superodistal setae, nine distal unequal crotchets, and numerous microtrichia; propodus just longer than carpus, narrower and slightly arcuate, about 3.5 times ltb, with superodistal PSS, three inferior setae, two long distal setae and two inferodistal setae; dactylus and unguis claw-like, dactylus with proximal spinules, unguis with double comb of four broad spines.

Pereopod-5 ( Fig. 33F ) like pereopod-4 but ischio-basis with five inferodistal setae; merus with two inferodistal setae; carpus with three superodistal setae and nine or ten crotchets.

Pereopod-6 ( Fig. 33G–H ) like pereopod-5 but merus with three superodistal setae and five inferodistal setae; carpus with six superodistal setae and eleven crotchets; propodus with distolateral fringe of c. eight pectinate spines, and small superodistal seta adjacent to PSS.

Pleopods ( Fig. 32C–E ) progressively smaller and less setose from pleopod-1 to pleopod-3. Pleopod-1 ( Fig. 32C–D ) peduncle 1.2 times ltb, mesial margin with one plumose seta, lateral margin with six plumose setae; endopod 2.3 times ltb, with three proximal setae; lateral margin with fringe of c. 13 setae, distalmost short and thick, with whip-like tip; exopod longer and wider than endopod, 2.4 times ltb, with lateral fringe of about 26 setae. Pleopod-2 ( Fig. 32E ) similar but peduncle slightly smaller, with five lateral plumose setae, exopod with 25 setae. Pleopod-3 ( Fig. 32F ) similar to pleopod-2 but peduncle smaller, with three lateral plumose setae, exopod with 16 setae (endopod obscured in dissected material).

Uropod ( Fig. 32G–H ) peduncle twice as long as broad, with five distal setae (one distolateral, four distomesial); endopod 6-segmented, segments 1–4 subequal in length (in figured specimen), terminal segment short, as long as broad; segments 1–5 each with one distal PSS and one (segment-1) or six (segments 2–5) distal simple setae.

Intraspecific variation. Manca-II. Without pereopods-6 and pleopods; length 0.8–1.06 mm (n=10). Antennule article-4 with one aesthetasc. Uropod with three-segmented endopod, terminal segment not reduced.

Manca-III. With rudimentary pereopods-6 and pleopods; length 1.00– 1.35 mm (n=15). Antennule article-4 with one aesthetasc. Uropod with three-segmented endopod, terminal segment not reduced.

Small non-ovigerous female/neuter. Habitus essentially like holotype female; length 1.3–1.8 mm (n=21). Antennule article-4 with two to four aesthetascs (mostly three). Uropod endopod 3–4 segmented (mostly threesegmented).

Larger non-ovigerous and preparatory female. Habitus essentially like holotype female; length 1.8–3.9 mm (non-ovigerous females, n=46); 2.4–4.4 mm preparatory females, n=8). Antennule article-4 with 5–7 aesthetascs. Uropod 4–5 segmented (non-ovigerous females), 5-segmented (preparatory females).

Ovigerous female. Habitus essentially like non-ovigerous female, but with ovisac on pereopod-4; length 4.9 mm (n=1). Antennule article-4 with 5–7 aesthetascs. Uropod 5-segmented.

Preparatory male. Habitus like female or neuter progressively to copulatory male; length 2.8–3.9 mm (n=8). Pereonite-6 sternum with slightly raised, paired genital cones. Paratype preparatory male, 3.16 mm (P. 102375, P.102375.001). Antennule ( Fig. 34A–B ) 0.7 times length of cephalothorax, article-1 2.5 times ltb, article-4 with 6– 9 aesthetascs. Cheliped ( Fig. 35A–B ) as female or progressively like copulatory male. Uropod endopod 4–5 segmented.

Allotype copulatory male, 2.7 mm (P. 102367). Habitus ( Fig. 34C ) fairly stout, 4.9 times ltb; length 2.7–3.5 mm (n=3). Cephalothorax proportionately slightly larger than female, 24% of total length, as long as pereonites 1–3 combined, 1.2 times ltb. Genital cones more elevated than in preparatory male. Paratype copulatory male, 2.8 mm (P. 102376, P.102376.001). Antennule ( Fig. 34D–E ) more slender than in female, 0.6 times length of cephalothorax; article-1 3.2 times ltb, article-4 with seven to nine aesthetascs. Cheliped ( Fig. 35C–D ) larger and stouter than female; sclerite with two anterodorsal setae; basis posterior lobe as large as anterior mass, latter with single dorsal and ventral setae; merus with three ventral and three dorsolateral setae; carpus 1.3 times lth, superior margin with one proximal and four distal setae, inferior margin with five setae; fixed finger with proximal diastema and raised distal incisive margin, inferior margin with eight setae. Uropod ( Fig. 34F ) endopod five-segmented.

Distribution and habitat. From littoral algae, Pariati Bay, Rapa Iti, Bass (Austral) Islands.

Remarks. Of the eleven previously-described Zeuxoides species, none have been recorded from the Indo- Pacific although six have been described from adjacent regions, essentially Australia and New Zealand. ( Z. aka Bird, 2008 ; Z. casanunda Bamber, 2005 ; Z. lasti Edgar, 2008 ; Z. lauriebourqueae Edgar, 2008 ; Z. mawbeyi Edgar, 2008 ; Z. rimuwhero Bird, 2008 ). Table 9 outlines differences in some, largely external, characters between all twelve species, focusing on aspects of antennular, mandibular, pereopodal, pleopodal and uropodal morphology. Based on this, Zeuxoides rapaitii n. sp. most closely resembles the New Zealand species Z. rimuwhero , sharing eight of the twelve character states (although including overlapping numeric ranges), differing in having eight instead of seven maxillule spines, generally fewer crotchets on the carpus of pereopods 2–6 (8–11 versus 9–12) and lateral setae (six versus eight) on the pleopod peduncle, and a different shape of the male’s cheliped fixed finger. Also, Z. rimuwhero gains more uropod segments at smaller sizes than Z. rapaitii ( Fig. 29B ), the female cheliped carpus has 6–7 ventral setae ( Bird 2008: fig.16) rather than four, and the pereopod-1 propodus has fewer inferodistal setae, inter alia.

Figures

FIGURE 29. Comparison of body size with number of uropod articles. A, Zeuxo seurati and Z. kermadecensis; data points for Z. kermadecensis slightly displaced on y-axis for clarity; non-integer values indicate specimens with uropods of different segment count. B, Zeuxoides rapaitii and Z. rimuwhero; data points for Z. rimuwhero slightly displaced on y-axis for clarity.

FIGURE 30. Zeuxoides rapaitii n. sp. non-ovigerous female holotype (P.98933). A, habitus; B, cephalothorax pigmentation. Preparatory female paratype (P.102374). C, pleonites 4–5 and pleotelson. Non-ovigerous female paratype (P.102372.001). D, antennule; E, antenna. Scale bars: habitus 2 mm, others 0.2 mm.

FIGURE 31. Zeuxoides rapaitii non-ovigerous female paratype (P.102372.001). A, left mandible; B, variation (wear) in left mandible lacinia; C, right mandible; D, labium; E, maxillule endite; F, maxillule palp; G, maxilla; H, maxilliped; I, maxilliped articles 3–4; J maxilliped articles 3–4 inner (oral) setae; K, epignath (distal obscured). Scale bars: 0.1 mm

FIGURE 32. Zeuxoides rapaitii non-ovigerous female paratype (P.102372.001). A, cheliped; B, cheliped fixed finger distomesial setae; C, pleopod-1 (all setae plumose, many omitted for clarity); D, pleopod-1 endopod; E, pleopod-2 peduncle; F, pleopod-3 peduncle; G, uropod; H, uropod segment-6 terminal setae. Scale bars: 0.2 mm.

FIGURE 33. Zeuxoides rapaitii non-ovigerous female paratype (P.102372.001). A, D–G, pereopods 1–6 respectively, with details of obscured setation; C, pereopod-1 coxal spur (setae omitted); H, pereopod-6 propodus. Scale bars: 0.1 mm.

FIGURE 34. Zeuxoides rapaitii preparatory male paratype, 3.16 mm (P.102376, P.102376.001). A, antennule; B, antennule aesthetascs. Copulatory male allotype (P.102367). C, habitus. Copulatory male paratype, 2.81 mm (P.102376, P.102376.001). D, antennule; E, antennule aesthetascs; F, uropod. Scale bars: habitus 1 mm, others 0.2 mm.

FIGURE 35. Zeuxoides rapaitii preparatory male, 3.16 mm (P.102375, P.102375.001). A, cheliped; B, cheliped fixed finger distomesial setae. Copulatory male paratype, 2.81 mm (P.102376, P.102376.001). C, cheliped; D, cheliped fixed finger distomesial setae Scale bars: 0.2 mm.