Araphura whakarakaia, Bird, 2011

BIRD, GRAHAM J., 2011, Paratanaoidean tanaidaceans (Crustacea: Peracarida) from littoral and shallow sublittoral habitats in New Zealand, with descriptions of three new genera and seven new species, Zootaxa 2891 (1), pp. 1-62 : 42-47

Araphura whakarakaia n. sp.

Figs 23–26

Material examined. Holotype: neuter/non-ovigerous female, 2.54 mm, Aotea Harbour, muddy sand, 8/4/10, GJB/ 5-10, [CR.21789]. Paratypes: one neuter partly dissected on microslide, GJB/5-10, [CR.21790]; one neuter, PB Stn 2.2, [CR.21791]; two neuters, one ov. female, PB Stn 10.3, [CR.21792]; 13 neuters/non-ov. females, two prep. males, GJB/5-10, [ NIWA: 70537]; one prep. male [?}, O.543/BS.799, [CR.21808]. Other material: two neuters/ non-ov. females, GJB/2-10; two neuters/non-ov. females, GJB/2-10; four neuters, one post-ov. female, one prep. male, GJB:RW/19-11.

Diagnosis. Female: Araphura with pereonites 2–4 just longer than broad. Pleotelson shorter than broad, with apical process. Antenna article-4 without fusion-line. Mandible molar broad, coarsely denticulate. Cheliped carpus, palm, fixed finger and dactylus with rows of nodules. Pereopods 1–3 carpus with one spine and one seta. Uropod exopod reaching two-thirds of endopod segment-1.

Etymology. From Te reo Māori adjective whakar ā kai, ‘ornate’ [as in a carving]; this alludes to the nodulose cheliped carpus, propodus and dactylus.

Type locality. Pourewa Point , Aotea Harbour, Waikato, North Island, New Zealand, low intertidal sand .

Description. Neuter [body proportions refer to largest individuals]: Habitus ( Figs 23A ) typical Araphura , shiny-white, cheliped crenulations clearly visible in dorsal view under low magnification; very slender, 9.9 times ltb; length 1.84–2.71 mm. Cephalothorax ( Fig. 23B ) elongate, almost as long as pereonites 1–2, 1.7 times ltb with anterolateral seta; coxal sclerites form entire posterioventral part of cephalothorax and are fused ventromesially, with complex depression posterior to cheliped bases. Pereon 59% of body length, pereonites parallel-sided with slightly rounded corners, all with anterolateral seta; pereonites 1 and 6 shortest, equally long, pereonites 0.67, 1.1, 1.2, 1.2, 1.0, and 0.75 times as long as broad respectively. Pleon ( Fig. 23C ) 16% of body length, just shorter than pereonites 5–6, sternites with raised keel-like processes, epimera with simple seta. Pleotelson ( Figs 23D–E ) pentagonal, as long as pleonites 4–5, 0.8 times as long as broad, with two posteriolateral setae and two simple and two pinnate posterior seta; with small apical process bearing two setae.

Antennule ( Fig. 23H ) typical, article-1 2.6 times ltb; article-4 with six setae and one aesthetasc. Antenna ( Fig. 23J ) typical, article-4 five times ltb, without fusion line.

Labrum ( Fig. 24A ) typical, distally setose. Labium ( Fig. 24B ) typical, with few anterolateral setules. Mandibles ( Figs 24C–F ) typical, left and right incisors denticulate, lacinia mobilis narrow with two denticles; molars relatively broad with blunt and acuminate apophyses. Maxillule ( Fig. 23G ) typical, endite with eight terminal spines, one pectinate. Maxilla ( Fig. 23H ) elongate, located posteriolaterally to maxillipeds. Maxilliped ( Figs 23J–K ) typical, set on ovoid pedestal; endite with mesial round spine, mesial seta, and setose anterolateral margin.

Cheliped ( Figs 23F , 24L–M ) basis with free posterior process small; carpus 1.6 times ltb, inferior margin crenate; propodus with crenate superior distal margin and lateral crenate ridge extending onto fixed finger, palm with two mesial spines; dactylus with nodulose superior margin and one mesial seta.

Pereopod-1 (Fig. 25A) typical for genus, small relative to body size; coxa with seta; basis shorter than distal articles combined, with a superior PSS; ischium with one seta; merus 1.4 times ltb, with two inferior setae; carpus pleon sternal processes (lateral view); D pleotelson; E pleotelson apical process (lateral view); F right cheliped (dorsal view); G uropod; paratype non-ovigerous female: H antennule; J antenna. Scale bars: (i) 1 mm for A; (ii) 0.25 mm for B–C, 0.125 mm for D–E; (iii) 0.125 mm for G–J. distal seta; dactylus shorter than unguis, with accessory seta, together subequal to propodus. Pereopod-2 (Fig. 25B) similar to pereopod-1 but carpus and propodus slightly shorter, propodus without superior seta. Pereopod-3 (Fig. 25C) similar to pereopod-2.

Pereopod-4 (Figs 25D–E) basis slightly broader than pereopods 1–3, with two large inferior PSS; ischium with rior distal spine and two inferior distal spines, all delicately pectinate; dactylus longer than unguis, together as long as propodus. Pereopod-5 (Fig. 25F) similar to pereopod-4. Pereopod-6 (Fig. 25G) similar to pereopods 4–5 but basis without PSS; propodus with two pectinate spines and one longer smooth (?) superior distal spine.

Pleopod (Fig. 25H) typical of genus, relatively small; endopod with distomesial seta, lateral margin with about six setae, naked for proximal half; exopod broader, with one proximal seta and about fifteen other lateral setae separated by small gap.

Uropod ( Fig. 23G ) just longer than pleotelson; fused exopod held close to endopod, elongate, reaching just over two-thirds length of endopod segment-1, setation typical of genus; endopod slender, segment-1 about twothirds total length, with one simple and two distal PSS, segment-2 with five unequal simple setae and two PSS.

Neuter [small]: Habitus ( Fig. 26A ) similar to larger neuter/non-ovigerous female but only 8.7 times ltb; length 1.49–1.66 mm. Pereonites 2–4 shorter than broad, pereonite-6 shorter.

Ovigerous female: similar to non-ovigerous female; length 2.22 mm. The single specimen with six large ova in marsupium.

Post-ovigerous female: similar to ovigerous female (dorsoventrally compressed) but lacking oostegites; length 2.29 mm.

Preparatory male: Habitus ( Fig 26.B ) similar to female/neuter but pleon more developed, 19 % of body length; length 1.78–2.24 mm. Antennule ( Fig. 26C ) thicker. Pleopods larger.

Remarks. This Araphura species resembles the Californian A. cuspirostris Dojiri & Sieg, 1997 in possession of a small, square, apical process on the pleotelson, and the nodulose chelipeds are rare among described species of this genus. This ‘ornamentation’ is also expressed in A. elongata (Shiino) , from the subantarctic South Shetland Islands and, among others, the apparently unrelated genera Chauliopleona Dojiri & Sieg, 1997 , Akanthophoreus Sieg, 1986 , Kanikipa n. gen. (see below), and Tanaissus Norman & Scott. An adaptationist view of these nodulose (or, alternatively, crenulated) chelipeds has been put forward by Bird & Heard (in prep), namely that they may assist traction between sand-grains, since many of the taxa mentioned have been recorded in sandy substrata.

If it were not for the pleotelson process and cheliped nodules, A. whakarakaia n. sp. would appear at the same position as A. higginsi Sieg & Dojiri 1989 in the Larsen et al (2009) key. Its pereopods 1–3 all have a reduced carpal setation, with a single superior spine and one inferior seta; this is the same pattern as in A. joubinensis Sieg & Dojiri 1989 . In the type species, A. brevimanus , three carpal setae (or spines) are present. Araphura whakarakaia n. sp. has the most robust mandible molars of any Araphura species , comparable only to A. elongata or A. spinithenari Larsen 2005 , but it does not essentially diverge from the generic pattern of distal denticles, variously enlarged or reduced.

A small elongate swimming male (1.32 mm) was also recorded in one of the Aotea Harbour samples (GJB/5- 10) but it was in relatively poor condition and more evidence is required before it can be confidently assigned to A. whakarakaia .

Distribution and ecology. It is only known from four localities: the west coast of North Island at Aotea Harbour and offshore Ninety Mile Beach, Northland at 53 m; the Cook Strait region of North Island, and off the Canterbury coast, South Island, at 0–14 m ( Knox et al 1978, listed only as ‘Tanaid sp.1’). Recorded sympatric tanaidaceans are Paratanais tara n. sp. and Kanikipa portobelloensis n. gen. n. sp. (see below). It shows a typical pattern for shallow soft-sediment dwelling tanaidaceans, being tolerant of intertidal situations as well as sublittoralshelf habitats and appears to be an ecological equivalent of A. brevimanus from British and north European waters ( Holdich & Jones 1983). It is probably much more common and widespread than these records suggest.

Figures

FIGURE 23. Araphura whakarakaia n. sp. Holotype non-ovigerous female: A dorsum; B cephalothorax (ventral view); C

FIGURE 24. Araphura whakarakaia n. sp. Paratype non-ovigerous female: A labrum; B labium; C–D left and right mandibles; E–F left and right molars; G maxillule endite, distal; H maxilla; J maxilliped; K maxilliped palp articles 2–4; L right cheliped; M right chela (mesial view). Scale bars: (i) 0.125 mm for A–D and H–M; (ii) 0.05 mm for E–G.

FIGURE 26. Araphura whakarakaia n. sp. Paratype small neuter: A dorsum; Allotype preparatory male: B dorsum; C antennule. Scale bars: (i) 1 mm for A–B; (ii) 0.125 mm for C.