Atemtanais, 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 : 17-25

Atemtanais n. gen.

Diagnosis. Female: robust paratanaidid. Cephalothorax sub-hexagonal, carapace entire. Pereonites all shorter than broad. Pleonites with simple epimeral setae. Pleotelson with broad, rounded posterior margin. Antennule 4-articled, with blunt-tipped setae on all articles. Antenna six-articled, article-2 with superior and inferior setae; article-3 with stiff superior seta (not thorn-like). Mandible robust, molar with broad, tuberculose crushing margin; right incisor weakly bifid. Maxillule endite with eight terminal spines. Maxilliped endite with two close-paired mesial teeth and slender seta; palp segment-2 with strong multifurcate spine. Cheliped coxal sclerite triangular insertion into basis, with large posterior process. Pereopods with blunt setae on most segments; pereopods 1-6 ischium with seta; pereopods 2–3 carpus with three spines, superior largest; pereopods 4–6 carpus with four stout spines and blunt seta. Pleopods present, biramous; endopod with gap between proximal seta and outer setal fringe, exopod with gap between setal fringe and peduncle. Uropod biramous, endopod and exopod stout, shorter than peduncle, both with blunt-tipped setae.

Male: Habitus paratanaidid primary male form. Cephalothorax as long as pereonites 1–4. Pereonites 4-6 longer than pereonites 1-3 and pleonites. Antennule with 3-articled peduncle, flagellum 4-segmented, without cap-like terminal. Antenna different from female, articles 2–3 with acuminate setae. Cheliped dactylus incisive margin with rounded apophyses with adjacent digitiform spines. Pereopods 4-6 carpal spines longer than female. Pleopod setal fringes without proximal gap. Uropod more slender than female, exopod 2-segmented.

Type species. Atemtanais taikaha n.sp, by monotypy.

Gender: male (following Metatanais Shiino, 1952 ).

Etymology. a partial anagram of Metatanais , to indicate its apparent affinity.

rounded pleotelson, similar antennal setation, large cheliped coxal sclerite, and widespread distribution of rather stiff, blunt-tipped setae. Metatanais was a rather poorly known genus, variously assigned to the Nototanaidae (e.g. Larsen & Wilson 2002; Błażewicz-Paszkowycz & Zemko 2009) or to incertae sedis family status, albeit with a possible affinity (as a sister group) to the Paratanaidae ( Bird & Larsen 2009) . An Australian species, Metatanais bipunctatus , was described recently by Błażewicz-Paszkowycz & Zemko (op.cit.), along with a new look at the type species Metatanais cylindricus Shiino, 1952 .

In contrast, Atemtanais n. gen. also has close affinities to Paratanais , in possession of a 4-articled antennule, similar maxilliped endite shape and armament, stronger pereopod setation, and a uropod exopod. Furthermore, Paratanais denticulatus Gutu & Ramos, 1995 , P. intermedius Dojiri & Sieg, 1997 , and P. spinanotandus Sieg, 1981 share a similar multifurcate spine on maxilliped palp article-2, and the pereopod setation is near-identical in Atemtanais and the first of these three species. The lack of a small terminal flagellar segment on the antennule of the male of Atemtanais is similar to the un-named Antarctic species described by Sieg (1986a: 97-63), who tentatively linked that taxon with the species group mentioned above.

Atemtanais is considered to be a separate genus from Paratanais as, aside from the Metatanais -like characters mentioned above, it lacks supposedly diagnostic pleonal plumose setae (see below), the cephalothorax is strongly hexagonal, and its pleopod setation is reduced. This taxon appears to represent an intermediate morphology between Metatanais and Paratanais (but closer to the latter) and tends to support the phylogenetic analysis given by Bird & Larsen (op.cit.).

Atemtanais taikaha n. sp.

Figs 7–11

Material examined. Holotype: ovigerous female, 2.38 mm, Ruby’s Reef, Kaikoura, Horning-1, [ CR.21782] . Allotype: one swimming male, Fifth Bay , Kaikoura, Horning-3, [ CR.21783] . Paratypes: one neuter (partly dissected), Horning-2, [ CR.21784]; one prep. female, Lowry-1, [ CR.21805] .

Etymology. from Te reo Māori noun taikaha , ‘a tough customer’, alluding to the powerful and strong habitus; noun in apposition.

Type locality. Ruby’s Reef , Kaikoura, South Island, New Zealand, among shallow (4–12 m) sublittoral epifauna (bryozoans, hydroids and sponges) and green alga Caulerpa ; ca. 42 o 23.92’S 173 o 41.66’E .

Description. Female: Habitus ( Figs 7A,E ) robust, shiny and well calcified; stout to fairly slender, 4–6 times ltb (contracted c.f. relaxed-extended condition); length 2.38–3.34 mm (ov. female and prep. female respectively). Cephalothorax ( Fig. 7B ) strongly hexagonal, as long as broad, longer than pereonites 1–3 (contracted holotype); rostrum overhanging base of antennules; small seta posterior to eye. Pereon 48% (contracted holotype) of body length, all pereonites much shorter than broad, with weakly rounded lateral margins, pereonite-1 shortest, pereonites 2–3 and pereonite-6 subequal, pereonites 4–5 longest, subequal. Pleon ( Fig. 7F ) 16% (contracted) of body length, pleonites much wider than long; epimera with simple seta. Pleotelson ( Fig. 7D ) twice as wide as long, with broad rounded posterior margin, with two superior distal blunt setae and two PSS.

Antennule ( Fig. 7G ) 0.73 times as long as cephalothorax; article-1 just longer than article 2–4 combined, 1.9 times ltb, with stiff distolateral seta and group of three PSS; artile-2 just shorter than broad, with distolateral seta, smaller distomesial seta, and group of inferior PSS; article-3 0.6 times as long as article-2, with mesial and lateral setae; article-4 with five unequal blunt-tipped setae, one aesthetasc, and small PSS. Antenna ( Fig. 7H ) about 0.8 times as long as antennule; article-1 short, naked, annular; article-2 twice as long as article-3, and wider, with stiff superior and inferior distal setae; article-3 as long as broad, with stiff superior seta; article-4 2.6 times ltb, with proximal superior PSS, one blunt-tipped distal seta and about three distal PSS; article-5 half as long as article-4, with blunt-tipped seta; article-6 short, with two short stiff setae and complex fused (?) seta of four elements. Labrum ( Fig. 8A ) distally conical, finely setose. Mandibles ( Figs 8B–C ) left incisor crenulate, with sub-quadrate lacinia mobilis, molar with broad crushing margin with several conical denticles; right incisor weakly bifid, dorsal margin crenulate, molar similar to left mandible. Labium ( Fig. 8D ) lobes with distal process setose, and scattered distal setae or microtrichia. Maxillule ( Figs 8E–F ) endite with setules or microtrichia along length, with eight (?) with setose margin, distomesial margin with two rounded teeth and slender seta; palp segment-1 as long as segment-2 or segment-3, segment-2 with distolateral seta, one long finely pectinate seta, one shorter similar seta and a broad, multifurcate spine, segment-3 with three pinnate setae and smaller seta, segment-4 with lateral seta, five pinnate terminal setae, and setose mesial margin. Epignath not recovered.

Cheliped ( Figs 7C , 8N–P ) powerful; coxal sclerite large, with triangular insertion into basis and broad posterior section confluent with cephalothorax margin; basis with posterior free process much smaller than anterior part; merus large, forming over 75% of inferior margin with carpus, with one blunt seta; carpus stout, 1.3 times ltb, with large free posterior process and short free inferior margin, with two superior setae and two unequal inferior blunt seta; chela about as long as carpus, but narrower, 1.7 times ltb, palm about twice as long as fixed finger, with two unequal inferior setae, and one superior mesial spine, fixed finger with large kukri-shaped spine near articulation with dactylus, three blunt-tipped setae at incisive margin, large granular distal tooth, and brown-chitinised terminal spine; dactylus with blunt proximal spine on incisive margin, small superior mesial spine, and brown-chitinised unguis.

Pereopod-1 (Fig. 9A) larger than pereopods 2–3, coxa with blunt seta [and oostegite bud in prep. female]; basis 4.4 times ltb, with superior proximal blunt seta; ischium with small seta; merus about 2.4 times ltb, with oblique distal margin, with small inferior mesial blunt seta; carpus sub-rectangular, just longer than merus, 1.8 times ltb, with three distal blunt setae; propodus 1.3 times longer than carpus, inferior and superior margins with a few spinules, with superior distomesial blunt seta and smaller inferodistal seta; dactylus half length of unguis, with accessory seta, unguis blunt-tipped, together half length of propodus. Pereopod-2 (Fig. 9B) coxa, basis and ischium similar to pereopod-1 but basis slightly shorter and broader, naked; merus twice as long as broad, with inferodistal blunt seta and small spine; carpus just longer than merus, with three distal spines; propodus 1.5 times longer than carpus, with small inferior and superior distal setae; dactylus and unguis similar to pereopod-1 but shorter. Pereopod-3 (Fig. 9C) similar to pereopod-2 but with shorter basis, merus and propodus.

Pereopod-4 (Fig. 9D) basis similar to pereopod-3 but broader, with inferior seta and a PSS; ischium with two unequal seta, one blunt; merus with two strong inferodistal spines; carpus as long as merus, with four strong distal spines and superior rod-like seta; propodus 1.2 times longer than carpus, with superior and inferior spinules or microtrichia, a superior PSS, one superior distal spine and two inferodistal spines; dactylus and unguis claw-like, weakly demarcated, 0.6 times as long as propodus. Pereopod-5 (Fig. 9E) similar to pereopod-4 but basis with a small superior PSS, and a blunt inferior seta. Pereopod-6 (Fig. 9F) similar to pereopod-5 but basis without inferior seta; propodus with three pectinate superior distal spines.

Pleopod (Fig. 9G) relatively small; peduncle naked; exopod 2.6 times ltb, with ten lateral plumose setae, separated from peduncle by gap; endopod slightly shorter and narrower, with distomesial seta and seven lateral plumose setae, with gap between proximal seta and distal fringe.

Uropod (Fig. 9H) small, about half as long as pleotelson; peduncle just longer than broad; exopod half length of peduncle, with distal seta and two unequal blunt-tipped setae; endopod about twice as long as exopod, with pseudo-segmentation marked by at least one PSS, with five blunt-tipped terminal setae.

Neuter: Generally similar to female, length 2.36 mm.

Male. Habitus ( Fig. 10A ) fairly stout, 4.7 times ltb, length 2.31 mm. Cephalothorax as long as pereonites 1-4; rostrum ( Fig. 10B ) spatulate; eyes massive, about third as long as cephalothorax. Pereon 43% of body length; pereonites 1-3 subequal, much shorter than broad, pereonites 4-5 longest. Pleon 25% of body length, pleonites shorter than pereonites 1-3; epimera with simple short seta. Pleotelson ( Fig.10C ) just longer than last pleonite, with small rounded apex, with two lateral setae, and four apical setae (two PSS).

Antennule ( Figs 10D–E ) as long as cephalothorax; peduncle article-1 2.4 times ltb, with mesial and lateral blunt setae and two groups of lateral PSS; article-2 shorter than broad with distolateral blunt seta and three PSS; article-3 shorter than broad, with two stiff setae; flagellum 4-segmented, segment-1 short, with inferior row of about twelve aesthetascs; segment-2 slightly longer, with about ten aesthetascs; segment-3 twice as long as segment-2, with about eight inferior aesthetascs; segment-4 as long as segment-3, with four blunt setae, one aesthetasc and one PSS.

Antenna ( Fig.10F ) about half as long as antennule; article-2 longer than broad, with superior and inferior setae; article-3 as long as broad, with stiff superior seta; article-4 longest, 2.5 times ltb, three PSS mid-length, and with long distal seta and two or three PSS; article-5 narrower and just shorter than article-4, with seta; article-6 cap-like with one short and five long, blunt setae.

Cheliped ( Figs 10G–H ) stout, similar to female but propodus broader, palm with long seta near articulation with dactylus and mesial comb of about ten spines; fixed finger with conical proximal process and large distal tooth; dactylus with two conical incisive processes with associated peg-like spines.

Pereopod-1 ( Fig. 11A ) similar to female but basis and propodus more slender, merus with superior proximal seta. Pereopod-2 similar to pereopod-3. Pereopod-3 ( Fig. 11B ) similar to female but basis and propodus more slen- der, merus spines stronger; carpus spines longer, and with superior seta.

Pereopod-4 ( Fig. 11C ) similar to female but merus, carpus and propodus more slender; carpus and propodus

Pleopod ( Fig.11E ) similar to female but larger; endopod broader; exopod and endopod setae proportionately longer, without proximal gap in setal fringe.

Uropod ( Fig.11F ) peduncle longer than broad; exopod 2-segmented, just longer than peduncle; endopod 2-segmented, segmente-1 with pseudo-segmentation marked by row of pinnate setae; other setation as figured.

Remarks. The shape of the cephalothorax and pleotelson, with the stout uropods, should distinguish A. taikaha n. gen. n. sp. from a Paratanais species found in the same area (see below).

Distribution and ecology. This species has been recorded only from Kaikoura, South Island, among various epifauna and the green alga Caulerpa brownii , in the shallow sublittoral at 4– 12 m.

Figures

FIGURE 7. Atemtanais taikaha n. gen. n. sp. Holotype ovigerous female: A habitus; B rostrum; C cheliped-cephalothorax articulation; D pleotelson; paratype preparatory female: E habitus; F epimeral setae; G antennule, with detail of aesthetasc; H antenna, with alternative detail of terminal setae. Scale bar: 0.5 mm for A, E, and F; 0.25 mm for B–D; 0.125 mm for G–H.

FIGURE 8. Atemtanais taikaha n. gen. n. sp. Paratype neuter: A labrum [distal]; B–C left and right mandibles respectively; D labium; E maxillule; F maxillule endite spines; G maxilla; H maxilliped [excluding palps for clarity]; J endite spines; K palp; L

FIGURE 10. Atemtanais taikaha n. gen. n. sp. Allotype swimming male. A habitus; B rostrum; C pleotelson; D antennule

FIGURE 11. Atemtanais taikaha n. gen. n. sp. Allotype swimming male. A pereopod-1; B pereopod-3; C pereopod-4; D pereopod-6 distal articles; E pleopod exopod; F uropod. Scale bar 0.25 mm.