Zeuxoides aka, Bird, Graham J, 2008

Bird, Graham J, 2008, Untying the Gordian Knot: on Tanais novaezealandiae Thomson (Crustacea, Tanaidacea, Tanaidae) from New Zealand, with descriptions of two new Zeuxoides species, Zootaxa 1877, pp. 1-36 : 18-26

Zeuxoides aka n.sp.

Figs 7–12

Material examined. Holotype: ovigerous Ψ (5.73 mm), Ports of NZ 2 TIU 84-TN, ( NIWA.44911).

Allotype: ɗ (3.58 mm), Ports of NZ 2 TIU 84-TN, ( NIWA.44912)

Paratypes: one prep. Ψ, one ɗ, Ports of NZ 2DUD246-TN (NIWA.44913); one ɗ, KBZ037-TN (NIWA.44914); one neuter, one prep. Ψ, KBZ041-TN (NIWA.44915); one prep. ɗ, 2LYT025-TN (NIWA.44916); one ovig. Ψ, one ɗ, 2LYT041-TN (NIWA.44917); two ovig. ΨΨ, one prep. Ψ (one ovig. Ψ and one prep. Ψ as NMNZ Cr. 012189), 2LYT042-TN (NIWA.44918); one neuter, one prep. Ψ, one ovig. Ψ (NIWA.44919), one ɗ (NIWA.44920), 2LYT066-TN; one ɗ, 2LYT077-TN (NIWA.44921); one prep. Ψ, one ovig. Ψ, 2TIU014-TN (NIWA.44922); one prep. Ψ, 2TIU045-TN (NIWA.44923); one prep. Ψ (dissected on microslide, NIWA.449215), one ovig. Ψ (NIWA.44924), 2TIU084-TN; one ovig. Ψ, 2TIU085-TN (NIWA.44926).

Diagnosis. Zeuxoides with dorso-lateral plumose setae on pleonites 1–3. Antennule articles 3–4 only half length of article-2. Left mandible with tooth-like lacinia mobilis and setal row of one small spine, right lacinia reduced to small, minutely bifid, spine, setal row absent. Maxilliped basis with distal lobiform process. Maxillule palp with six terminal setae. Pereopod-1 coxa with bi-digitate spur; pereopods 2–3 carpus with nine to twelve spines; pereopods 4–6 carpus with 11–13 spines. Pleopod basis with one inner and five outer plumose setae; exopod with four inner plumose setae. Uropods seven-articled (but up to eight or nine). Sexual dimorphism moderate to strong, males with proportionately larger cephalothorax, shorter pereon and enlarged chelipeds.

Description. Ovigerous female: Body ( Fig. 7 A) about 4.6 times longer than broad, length 4.15–6.37 mm. Pigmentation dark purple-brown, as figured. Two large ovisacs, attached posterior to pereopod-4. Cephalothorax just longer than broad, longer than pereonites 1–3 combined, with setal groups posterior to eye-lobe and mid-laterally; rostrum weak. Pereon about 54% of body length, pereonites 1–3 progressively longer, pereonite-1 with lateral and dorso-lateral setae, pereonites 2–3 with lateral setal groups; pereonites 4–5 equally long, pereonite-6 just longer than pereonite-3; other setation as figured. Pleon ( Fig. 7 B) about 18% of total body length., pleonites 1–3 progressively smaller, with about one, five and two lateral plumose setae and about seven or eight plumose setae in dorso-lateral clusters; other setation as figured; pleonites 4–5 short and broad, with dorsal and lateral setal groups. Pleotelson ( Fig. 7 B) 0.62 times as long as broad; with two long apical setae and two pairs of setae on each lateral margin.

Antennule ( Fig. 8 A) 0.6 times as long as carapace; article-1 three times longer than broad, 2.6–3.4 times longer than article-2 (3.4, holotype), with several simple and pinnate lateral setae and inner and outer distal setal groups; article-2 with about four inner and six outer simple setae, in addition to several pinnate setae; article-3 less than half as long as article-2, with several simple and pinnate setae; article-4 very short, with three long setae, about six shorter setae and seven aesthetascs. Antenna ( Fig. 8 B) just longer than antennule; article-1 short; article-2 with one dorsal and two ventral setae, with dorsal spinulose margin; article-3 short, with ventral seta and spinulose dorsal margin; article-4 two proximal setae and about five distal setae; article- 5 with several simple and pinnate setae; article-6 short, with at least five setae; article-7 cap-like with at least six terminal setae.

Labrum ( Fig. 9 A) typical of genus, hood-like and distally setose. Mandibles ( Figs 9 B–C) typical of genus, robust; right mandible with weakly bifid incisor and small spiniform lacinia mobilis, minutely bifid, without setal row; left mandible with tooth-like lacinia mobilis and minute spine on setal row. Labium ( Fig. 9 D) typical of genus; inner and outer lobes setose, outer margin spinose, and with small conical, setose process. Maxillule ( Fig. 9 E) typical of genus; palp with six terminal setae; endite with eight terminal spines (one thinner than rest) and distal array of setae. Maxillipeds ( Figs 9 F–H) typical, robust; each basis with proximal lobe with two setae, distal margin with three unequal setae and disto-lateral process, densely armed with combs; endites with setose lateral and distal margin, each with two coupling hooks and inner distal margin with two large, articulated pinnate setae; palps typical, article-2 with three strong pectinate setae. Epignath ( Fig. 9 I) typical of genus.

Cheliped ( Fig. 10 A) typical of genus; sclerite with triangular ventral process and three anterior setae; basis with ventral seta and three unequal setae near articulation with sclerite; merus with two setae near articulation with carpus, and five ventral setae; carpus 1.6 times longer than broad, with disto-dorsal and ventral setal groups (as figured); chela 2.4 times longer than broad, propodus with five outer setae near dactylus; fixed finger with seven ventral setae and nine setae on outer incisive margin; dactylus with incisive margin set with small spines.

Pereopod-1 ( Fig. 10 B) Coxa with distinct anterior bicuspid spur, with three setae; ischio-basis, with two simple and one pinnate proximal setae, and two unequal disto-ventral setae; merus short, with single dorsal and ventral setae; carpus 1.2 times as long as merus, with two dorsal and three ventral setae; propodus as long as merus and carpus together, with strong anterior seta, dorsal pinnate seta, one dorso-terminal seta and four ventral and seta; dactylus and unguis about a third length of propodus, unguis with hollow (spinning) tip.

Pereopod-2 ( Fig. 11 A) much stronger than pereopod-1, coxa annular, with setae; ischio-basis with three proximal setae and five ventro-terminal setae; merus over half length of ischio-basis, with two dorsal and six ventral setae and a ventro-lateral complex spine; carpus shorter than merus, as long as broad, with about three dorsal and five ventral setae and ten complex spines; propodus 1.5 times length of carpus, with seven ventral setae, one dorsal pinnate seta and one dorso-terminal seta; dactylus and unguis together two-thirds length of propodus, dactylus with accessory seta and unguis with spinning pore.

Pereopod-3 ( Fig. 11 B) similar to pereopod-2, but with ventral ischio-basis pinnate seta; merus with dorsal pinnate seta; carpus with twelve complex spines; propodus with six ventral setae and longer dorso-terminal seta.

Pereopod-4 ( Fig. 11 C) ischio-basis broader than in pereopods 1–3, with proximal pinnate seta and seven ventral setae; merus about twice as long as broad, with group of three dorsal and four ventral setae and two complex spines; carpus shorter than merus, with dorsal paired groups each of four setae, and twelve complex spines; propodus weakly expanded distally, with four ventral setae and four distal setae, one pair of which are long and strong, and one dorso-terminal pinnate seta; claw typical of genus.

Pereopod-5 ( Fig. 11 D) Similar to pereopod-4, but carpus with 13 complex spines.

Pereopod-6 ( Fig. 11 E) Similar to pereopod-5 but carpus with eleven complex spines; propodus with distolateral comb of about ten leaf-shaped spines.

Pleopod ( Fig. 12 A) All of similar size; basis just longer than broad, with one inner and five outer plumose setae; endopod with four setae on outer margin, and about 20 on inner margin, thicker distally; exopod with about 36 marginal setae.

Uropod ( Fig. 12 B) Robust, seven-articled (some individuals eight or nine-articled); basis with about four inner and two outer distal setae; endopod with short articles, articles 2–5 with numerous long distal setae (about seven, eight, ten and eight respectively), article-6 very short with about five long terminal setae.

Non-ovigerous/neuter: Length 2.88 mm; essentially similar to ovigerous female; uropod five or six-articled.

Preparatory female: Length 4.15–4.98 mm; uropod six, seven or eight-articled.

Preparatory male: Length 3.44 mm; cheliped slightly enlarged; uropod six-articled.

Male ( Fig.7 C): Much more robust and compact than female, only 3.8 times longer than broad (allotype), length 3.58–4.93 mm; cephalothorax ( Fig 8 C) proportionately longer, and narrower anteriorly; pereonites 1–3 shorter; pleonites 4–5 distinct ( Fig. 7 D) or fused together ( Fig. 7 E). Antennule ( Fig. 8 D) longer than in female, 0.8 times as long as cephalothorax, article-1 3.5 times longer than broad; very short terminal article with about eight aesthetascs and eight long setae. Cheliped ( Figs 10 C–D) very robust and large, carpus only 1.2 times longer than broad; propodus and fixed finger 1.8 times longer than carpus, fixed finger bent slightly medially; dactylus inserted somewhat medially, tip slightly bent laterally. Uropod ( Fig 12 C) six or seven articled (up to eight-articled).

Etymology: From Te reo Mãori ‘aka’ = ‘harbour’, noun.

Type locality: Port of Timaru, east coast of South Island, New Zealand.

Distribution: The East coast of the South Island including Dunedin, Timaru, Lyttelton and Kaikoura.

Remarks: This large and robust Zeuxoides species was a candidate to be the true Tanais novaezealandiae Thomson , particularly since there are records from Dunedin Harbour (the type locality) which is the innermost zone of the larger Otago Harbour. It may also be found sympatrically or in close proximity to Zeuxoides rimuwhero n.sp. (see below). Tanais novaezealandiae sensu Tattersall (1921) is a possible synonym.

It is similar in general size and robustness to Z. pseudolitoralis that was described from the Kerguelen Islands but the current specimens are larger and have more uropod articles; similarly, specimens of ‘ Z. pseudolitoralis ’ from Macquarie Island, SW of New Zealand (identified by J. Sieg) are different from both these populations, with a larger cephalothorax. Zeuxoides aka n.sp. exhibits significant dimorphism, some males approaching those of Hexapleomera in body shape, and one (Stn 2LYT-066) also has visibly fused pleonites 4–5. The mandibular lacinia lacks a setal row (present as a seta or thin spine in Z. helleri and Z. pseudolitoralis ) but shares the smaller lacinia of the left mandible – making it close to the Tasmanian Z. mawbeyi . Compared to Z. casanunda , Z. aka n.sp. is more compact, lacks the terminal spine on the left mandible lacinia mobilis and has more pereopod carpal spines. It also possesses a cusped pereopod-1 coxa and the uropods are stouter than in Z. mawbeyi . The lateral process on the maxillipeds appears to be diagnostic and unique among Zeuxoides species.

The known distribution in the ports on the eastern seaboard of the South Island might suggest that the species is an alien or invasive species rather than an endemic but none of the recently described Zeuxoides from Australia and New Caledonia ( Bamber 2005, 2006; Edgar 2008) match this description.

Figures

FIGURE 7 Zeuxoides aka n. sp. Holotype Ψ (5.73 mm; Timaru, Stn 2 TIU 84; NIWA. 44911): A, dorsal view, typical pigmentation shown; B, pleon and pleotelson. Allotype ♂ (3.58 mm; Timaru, Stn 2 TIU 84; NIWA. 44912): C, dorsal view, pigmentation not shown; D, pleon and pleotelson. Paratype ♂ (5.75 mm; Lyttelton, Stn 2 LYT- 066,): E, fused pleonites 4 – 5 and pleotelson. Scale bar = 1 mm for A and C, 0.51 mm for B, D and E.

FIGURE 8 Zeuxoides aka n. sp. Paratype Ψ (Lyttelton): A, antennule; B, antenna. Allotype ♂ (Timaru): rostral area of cephalothorax; D, antennule. Scale bar = 0.75 mm for C, 0.5 mm for A, B and D.

FIGURE 9 Zeuxoides aka n. sp. Paratype Ψ (Lyttelton): A, labrum; B – C, right and left mandibles respectively, with detail of lacinia mobilis and setal row; D, labium (half shown); E, maxillule; F; maxilliped, palp setation omitted for clarity; G, maxilliped palp; H maxilliped endite, inner face; I, epignath. Scale bar = 0.5 mm.

FIGURE 10 Zeuxoides aka n. sp. Paratype Ψ (Lyttelton): A, cheliped; B, pereopod- 1. Allotype ♂: C, cheliped; D, inner view of chela. Scale bar = 0.5 mm for A, C and D, 0.35 mm for B.

FIGURE 11 Zeuxoides aka n. sp. Paratype Ψ (Lyttelton): A, pereopod- 2, with detail of longest carpal spine and dactylus / unguis; B – E, pereopods 3 – 6 respectively. Scale bar = 0.5 mm.

FIGURE 12 Zeuxoides aka n. sp. Paratype Ψ (Lyttelton): A, pleopod; B, uropod. Allotype ♂: C, uropod. Scale bar = 0.5 mm.