Heterotanoides muimui, Bird, Graham J., 2012

Bird, Graham J., 2012, A new leptochelioid family, Heterotanoididae (Crustacea: Peracarida: Tanaidacea), and a new species of Heterotanoides from New Zealand, Zootaxa 3481, pp. 1-26 : 3-10

Heterotanoides muimui n. sp.

Figs 1–4 ; 5H,O

Material. All from Waiheke Island, New Zealand. Holotype: ovigerous female, GJB/7-11, [accession no. CR.023294]. Allotype: male, GJB/7-11, [CR.023295]. Paratypes: seven non-ovigerous Ƥ, ten preparatory Ƥ, three ovigerous Ƥ seven preparatory 33, nine 33, GJB/7-11, [one preparatory female dissected on microslides CR.023296 and CR.023297]; 13 non-ovigerous Ƥ, 30 preparatory Ƥ, five ovigerous Ƥ, one post-ovigerous Ƥ, 13 preparatory 33, 13 33, GJB/8-11, [14 preparatory and mature males as CR.023298; 15 females as CR.023299; one 3 [entire] and one preparatory 3 cheliped on microslide CR.023300].

Diagnosis. Heterotanoides with pleonites 1–4 epimera with plumose sensory seta. Female antennule article-3 with subdistal aesthetasc; with cap-like segment, terminal aesthetasc apical. Antenna articles 2–3 with stiff superior seta. Maxilliped endite with four spines; palp article-2 with four inner setae, article-3 with seven inner setae. Cheliped carpus with four superior setae; propodus margins weakly divergent. Pereopods 4–6 carpus with three setal loci. Male antennule with basal aesthetasc and subdistal bundle of three aesthetascs on article-3; without caplike terminal segment.

Etymology. From Te reo Māori muimui (noun), “anything small or diminutive”.

Type locality. Among low-water stones, Corallina - Hormosira zone, Omiha Bay, Waiheke Island, North Island, New Zealand; 36.8201°S 175.0596°E (retrieved from Google Earth).

Description. Ovigerous and preparatory female: Habitus ( Fig. 1 A) fairly slender, 6.2 times longer than broad [ltb], length 0.9–1.35 mm (ovigerous 1.16–1.25 mm). Cephalothorax 1.2 times ltb, as long as pereonites 1–2 and half of P-3 combined; carapace entire, with brown pigmentation on anterior half; rostrum ( Fig. 1 B) shallow and extended over base of antennules and eyes. Pereonites all shorter than broad, pereonite-1 shortest, pereonite-4 longest. Pleon slightly tapering posteriorly, 15% of body length; epimera ( Fig. 1 C) of pleonites 1–4 with simple seta and delicate PSS, pleonite-5 with two simple setae. Pleotelson ( Figs 1 D–E) as long as pleonites 4–5, with projecting apex bearing four setae.

Antennule ( Fig. 1 F) 0.7 times as long as cephalothorax; article-1 compound, 0.6 times total length, distolateral seta just longer than article-2, 2.6 times ltb; article-2 about twice as long as broad, with lateral and mesial setae and mesial PSS; article-3 as long as article-2 but narrower, with subdistal aesthetasc, distal PSS and simple seta; terminal segment small, with three setae, one PSS, and apical aesthetasc. Antenna ( Fig. 1 G) article-2 larger than article-3, with lateral seta; article-3 as long as broad; article-4 as long as article-2, with long inferodistal seta and superodistal PSS; article-5 as long as but slightly narrower than article-4, with two setae and PSS; article-6 with suggestion of fusion line, as long as article-5, with distal seta and PSS; article-7 minute, with two short and two long setae.

Mouthparts: Labrum ( Fig. 2 A) subrectangular, finely setulate distally. Mandibles ( Figs 2 B–C) typical, right mandible incisor superior margin weakly crenulate, very weakly bifid; left mandible incisor with several processes, lacinia mobilis broad with one digitiform process and several smaller processes. Labium ( Fig. 2 D) typical, sparsely setulate. Maxillule ( Fig. 2 E) endite spines (nine?) short; palp with two terminal setae. Maxilla not observed. Maxilliped ( Figs 2 F–H) typical, bases together about as long as broad, each with seta over-reaching endite distal margin; endites relatively short, each with four distal spines (two pointed, two digitiform), distal ridge, and mesial coupling hook; palp article-2 with four mesial setae, article-3 as large as articles 1–2 combined, with seven inner setae, article-4 with subdistal lateral seta and six terminal setae. Epignath not observed.

Cheliped ( Fig. 2 J). Coxal sclerite with seta. Basis 1.2 times ltb, with superolateral seta; merus with two setae; carpus about twice as long as broad, with three proximal and one distal superior setae, and two unequal inferior setae; chela shorter and narrower than carpus; propodus 2.4 times ltb, palm 1.4 times longer than fixed finger, with inner comb of five setae and seta near articulation with dactylus; fixed finger with four setae in addition to three near incisive margin (three inferior or inferolateral, distal-most seta thicker and blunt), incisive margin with distal series of low teeth, terminal spine relatively narrow; dactylus with proximal-mesial seta, unguis relatively narrow.

Pereopod-1 ( Fig. 3 A) typical; coxa with seta [and oostegite bud in preparatory female]; basis arcuate, shorter than succeeding articles together, 4.5 times ltb, with two proximal superior setae; ischium with one seta; merus with one seta; carpus as long as merus, with three distal setae; propodus as long as carpus, with two distolateral setae; dactylus longer than unguis, together shorter than propodus. Pereopod-2 ( Fig. 3 B) similar to pereopod-1 but basis slightly stouter, with simple setae and PSS; merus shorter, naked; carpus with two distal setae; propodus with superodistal, distolateral and inferodistal setae; dactylus and unguis slightly shorter. Pereopod-3 ( Fig. 3 C) similar to pereopod-2 but basis with one simple seta and two PSS; carpus with one inferodistal seta.

Pereopod-4 ( Fig. 3 D) typical [with oostegite bud in preparatory female], basis 3.3 times ltb, with proximal superior seta; ischium with two setae; merus with two inferodistal spines; carpus as long as merus, with three unequal spines [or two spines and a simple superodistal seta]; propodus slightly narrower than, but as long as, carpus, with two inferodistal spines and three superodistal spines; dactylus and unguis together claw-like, shorter than propodus, dactylus-unguis junction marked by setule. Pereopod-5 ( Fig. 3 E) similar to pereopod-4 [but without oostegite]; basis without proximal seta (?). Pereopod-6 ( Fig. 3 F) similar to pereopod-5 but propodus with two additional superodistal spines.

Pleopod ( Fig. 3 G) endopod elongate-oval, 2.4 times ltb, with inner seta and fringe of five setae; exopod larger, oval, and twice as long as broad, with vestigial proximal article bearing a seta and fringe of nine setae on main article; all setae plumose.

Uropod ( Fig. 1 H) peduncle 1.8 times ltb, with long mesial-distal seta; endopod segments sub-equal; exopod two-segmented, longer than segment-1 of endopod.

Non-ovigerous female: similar to preparatory and ovigerous females; length 0.62–0.87 mm.

Preparatory male: Habitus similar to neuter and non-ovigerous female; length 0.73–0.89mm. Antennule of similar article proportions to female but article-3 with setation of male (see below). Cheliped ( Fig. 4 A) intermediate in size and shape between those of females and males (see below).

Male: Habitus ( Fig. 4 B) generally similar to female, fairly stout, five times ltb; length 0.85–1.23 mm. Cephalothorax proportionately larger, 1.33 times ltb. Pereonites 1–3 shorter, each about 0.3 times as long as broad. Antennule ( Fig. 4 C) longer, 0.9 times length of carapace, article-1 3.5 times ltb; article-3 with proximal aesthetasc, subdistal bundle of three aesthetascs, otherwise as female. Mouthparts functional, as in female. Cheliped ( Fig. 4 D) proportionately larger than female; carpus stouter, 1.5 times ltb, chela stouter, 2.3 times ltb, longer than carpus; dactylus ( Fig. 4 E) with two peg-like spines near incisive margin.

Remarks. Of the described species of Heterotanoides , H. muimui most closely resembles H. cognatus from Hong Kong: females share the single subdistal aesthetasc on antennule article-3, stiff (or spiniform) setae on antenna articles 2–3, and relatively elongate antennal articles 4–5. It differs from that species in having a more slender cheliped carpus and epimeral plumose setae (none in H. cognatus , Fig. 4 F). The terminal aesthetasc is apical in H. muimui n.sp, but subapical in H. cognatus ( Fig. 4 G); the maxilliped endite setation ( Fig. 4 H) of H. cognatus is similar to, but weaker than that of H. muimui . The males of the species are more distinct, H. muimui having a proportionately longer cephalothorax and shorter pereonites 1–3.

Distribution and ecology. So far, this species has been recorded only from Waiheke Island but was not present in coralline turf on the exposed northern coast, at Little Oneroa Bay. Out of 3179 tanaidaceans recorded from the Omiha Bay samples, Heterotanoides muimui n. sp. was represented by 113, or 3.6%. By far the most numerous species was Parakonarus kopure (95.1%), with Paratanais paraoa (1.0%) and Zeuxoides sp. (0.3%) minor contributors to the assemblage. It remains to be determined if the habitat preference for H. muimui is the algae or the accompanying silt in this sheltered locality.

The Heterotanoides population in this early summer sample was dominated by mature or maturing individuals (82%), with a male: female ratio of 0.86:1 (accounting for all maturation stages) or 2.6:1 (allowing for only fully mature males and ovigerous females). The small size of the species, the shortest measured at 0.62 mm, suggests that mancae stages, if present, may have passed through the sieve, or were overlooked.

Figures

FIGURE 1. Heterotanoides muimui n. sp. Holotype female: A habitus; B cephalothorax, anterior; C pleonal setae; D pleotelson, dorsal; E pleotelson, lateral; F antennule; G antenna; H uropod. Scale bars: i, 0.5 mm for A, 0.25 mm for B – E; ii, 0.125 mm for F – H.

FIGURE 2. Heterotanoides muimui n. sp. Paratype female: A labrum; B – C left and right mandibles respectively; D labium; E maxillule; F maxilliped (one palp omitted for clarity); G maxilliped endite; H maxilliped palp article- 4; J cheliped. Scale bar: 0.1 mm for A – H, 0.25 mm for J.

FIGURE 3. Heterotanoides muimui n. sp. Paratype female: A – F pereopods 1 – 6 respectively; G pleopod (all setae are plumose, simplified for clarity). Scale bar: 0.125 mm for A – G.

FIGURE 4. Heterotanoides muimui n. sp. Paratype preparatory male: A cheliped. Allotype male: B habitus; C antennule; D cephalothorax and cheliped, lateral view; E cheliped dactylus. Heterotanoides cognatus Bamber & Bird topotype ovigerous female: F pleonite margins; G antennule articles 2 – 3; H maxilliped endites. Scale bar: 0.5 mm for B, 0.25 mm for A, D, E, 0.125 mm for F, H, 0.2 mm for C, G.