Agononida polycerta, Poore, Gary C. B. & Andreakis, Nikos, 2014

Poore, Gary C. B. & Andreakis, Nikos, 2014, More species of the Agononida incerta complex revealed by molecules and morphology (Crustacea: Decapoda: Anomura: Munididae), Zootaxa 3860 (3), pp. 201-225 : 215-218

Agononida polycerta n. sp.

( Figs 2 f, 8, 9)

Agononida aff. incerta .— Macpherson 2013b: 292.

Material examined. Holotype. FRENCH POLYNESIA. Tuamotu group, Kaukura Atoll: 15°41'S, 146°54'W, 646–737 m (TARASOC stn CP3376), MNHN IU- 2010-6095* (male, 32 mm)

Paratypes. FRENCH POLYNESIA. Collected with holotype: MNHN IU- 2010-6157 (4 males, 20–28 mm; 9 females, 21–26 mm), MNHN IU- 2010-6094* (male, 28 mm), MNHN IU- 2010-6092* (female, 25 mm), MNHN IU- 2010-6089* (supermale, 32 mm), MNHN IU- 2010-6090* (female, 29 mm), MNHN IU- 2010-6091* (male, 28 mm), MNHN IU- 2010-6096* (male, 14 mm). Tuamotu group, Kaukura Atoll: 15°39'S, 146°54'W, 460–647 m (TARASOC stn CP3375), MNHN IU- 2010-6093 (female, 22 mm). Punu Taipu Guyot: 19°17'S, 150°59'W, (TARASOC stn CP3306), MNHN IU- 2010-6158 (male, 18 mm); 19°15'S, 150°56'W, 587 –704 m (TARASOC stn CP3303), MNHN IU- 2010-6159 (2 females, 14 mm).

Diagnosis. Telson anterolateral margin oblique, 3-lobed, straight over anterior 40%, convex and thickened over middle 30%, and most posterior section convex but more sharply curved anteriorly. Pereopods 2–4 with dactyli about 5–6 times as long as basal width; robust setae on flexor margin of pereopod 2 number 11–28 (median 25); of pereopod 3, 3–12 (median 9); and of pereopod 4, 1–6 (median 2, 10 rare). Pereopod 4 merus with 1–4 spines on upper face.

Description. Holotype, supermale, cl. 32 mm. Carapace 0.95 times as long as greatest width. Gastric region with pair of small epigastric spines. Frontal margin inclined posteriorly at 15° from midline. Rostrum spiniform, 0.44 length of carapace (both measured from base of supraocular spines); supraocular spine 0.65 length of rostrum (both measured from base of rostrum). Thoracic sternite 3 0.45 width of sternite 4; midlength of sternal plastron (sternites 4–7) 0.6 width of sternite 7. Abdominal somite 4 with median spine on posterior ridge having ancillary lateral spines.

Telson 2.5 times as wide as long; anterolateral margin oblique, 3-lobed, straight over anterior 40%, convex and thickened over middle 30%, and most posterior section convex but more sharply curved anteriorly; lateral margin evenly convex.

b Eye with maximum corneal diameter 0.85 basal width of supraocular spines. Maxilliped 3 ischium 0.6 times as long as merus.

Pereopod 1 (cheliped) 4.5 times as long as carapace, merus 1.45 times as long as carapace, carpus 0.5 times as long as merus, propodus 1.4 times as long as merus, fingers 0.5 times as long as total propodus length. Merus with 1+12 spines along upper margin, 1+15 spines along mesial face, 1+21 spines along lateral face, 1+8 spines on lower margin; carpus with 1+4 spines on upper margin, 1+6 spines on mesial face, 1+5 spine on lateral face; propodus oval in cross-section, with 10 emerging scales-spines on upper margin, with 1+5 emerging scales along mesial face, with 1+20 spines on lateral face, with scales only along lower margin; dactylus cutting edge with ridge of c. 50 uneven teeth, few more prominent than others; all rows of spines with intermediate smaller spines and emerging scales.

Pereopod 2 3.3 times carapace length, merus 1.5 times carapace length, 7.5 times a long as greatest width, carpus 0.25 times as long as merus, propodus 0.5 times as long as merus, dactylus 0.5 times as long as propodus; merus with 1+16 spines along extensor margin, with 1+12 spines along flexor margin; carpus with 1+2 spines along extensor margin; dactylus sinusoidal on extensor margin, tapering over distal half, 5.0 times as long as greatest basal width, with row of 25 robust setae distal to heel of flexor margin.

Pereopod 3 3.3 times carapace length, merus 1.4 times carapace length, 7.5 times a long as greatest width, carpus 0.25 times as long as merus, propodus 0.6 times as long as merus, dactylus 0.5 times as long as propodus; merus with 1+17 spines along extensor margin, with 1+11 spines along flexor margin; carpus with 1+2 spines along extensor margin; dactylus sinusoidal on extensor margin, tapering evenly, 5.4 times as long as greatest basal width, with row of 7 robust setae distal to heel of flexor margin.

Pereopod 4 3 times carapace length, merus 1.3 times carapace length, 7.0 times a long as greatest width, carpus 0.25 times as long as merus, propodus 0.6 times as long as merus, dactylus 0.5 times as long as propodus; merus with 1+16 spines along extensor margin, with 1+10 spines along flexor margin, with 2–4 spines on upper face; carpus with 1+2 spines along extensor margin; dactylus more gently curved than dactylus 2, distally less setose, 5.5 times as long as greatest basal width, with 6 robust setae distal to heel of flexor margin.

Paratype, female, 29 mm, MNHN IU-2010-6090. Telson anterolateral margin oblique, almost straight over anterior 70%, separated from more posterior section with slightly crenellate margin by shallow concavity.

Pereopod 1 (cheliped) of slender form, covered with prominent flat squamae fringed with short setae; 4.1 times as long as carapace, merus 1.4 times as long as carapace, carpus 0.5 times as long as merus, propodus 1.4 times as long as merus, fingers 0.5 times as long as total propodus length. Pereopod 1 merus with 1+5 spines along upper margin, 1+5 spines along mesial face, 1+13 spines along lateral face, 1 spine on lower margin; carpus with 1+2 spines on upper margin, 1+4 spines on mesial face, 1+2 spines on lateral face, 1+2 spines on lower margin; propodus round in cross-section, with 1+4 spines on upper margin, with 1+3 spines mesial face, with 1 spine on lateral face, with 1+2 spines on lower margin; dactylus cutting edge with ridge of c. 50 uneven teeth, few more prominent than others; all rows of spines with smaller intermediate spines.

Pereopods 2–4 similar to male; meri each with 18–22 spines along extensor margin, 8–10 along flexor margin plus intermediate smaller spines and emerging scales; dactyli 6 times as long as greatest basal width, with 27, 17 and 10 robust setae distal to heel of flexor margin respectively.

Colour. From photo of specimen from TARASOC stn DW3377 not located. Carapace, abdomen and pereopods dull yellow, more orange on anterior carapace. Pereopod 1 with orange transverse bands distally on merus, carpus, proximally on propodus and at bases of fingers. Pereopods 2–4 with orange transverse bands subdistally on merus and over distal third-half of propodus ( Fig. 2 f).

Variation. Based on counts from 20 individuals the numbers of robust setae on flexor margin are: pereopod 2 with 11–28 (median 25); pereopod 3 with 3–12 (median 9) and pereopod 4 with 1–6 (median 2, 10 rare). The merus of pereopod 4 has one or more facial spines on many, but not all, individuals and not always on both sides (cf. Figs 8 g, h). In some individuals the median spine on the posterior ridge of abdominal somite 4 is trifid while others carried an ancillary spine on only one side ( Fig. 8 c). As in other species in this complex, the anterolateral margin of the telson is more convoluted in adults males than in females and smaller males (cf. Figs 8 a, 9a, e).

Etymology. From Polynesia, type locality and incerta , original species in this complex.

Distribution. French Polynesia, 460–737 m (median 646 m) depth.

Remarks. Agononida polycerta has an isolated geographical distribution. The presence of this new species in the Agononida incerta species complex was suggested by the molecular analysis. Agononida polycerta is basal to the group of species, A. africerta , A. indocerta and A. vanuacerta of clade A ( Fig. 1 ). All four species of this clade are characterized by one or more spines on the upper face of the merus of pereopod 4 ( Fig. 8 g, f).

The numbers of spines on the extensor margins of the meri of pereopods 2–4 (at least 16 and up to 22) are greater than in all other species (usually 9–14). Further, these spine rows often include several intermediate shorter spines and elevated squamae not counted in these figure. The cheliped is similarly more spinose than in other species and has more prominent squamae, even in smaller individuals. Other species have few small intermediate spines. The species is also unusual in that the posterior transverse ridge of abdominal somite 4 often bears an ancillary spine on one side or both sides of the median spine typical of members of this complex ( Fig. 8 c).

The dactylus of pereopod 2 of the supermale is shorter and relatively broader over most of its length than those of pereopods 3 and 4. In a typical male, dactyli of all pereopods 2–4 are similar, about 5 times as long as wide while in the female they are slightly more slender, 6 times as long as wide (cf. Figs 8 d–f, 9b–d, f–g). This variation is typical of all species.

b f

c g

d h

Figures

FIGURE 1. Distribution (based on 189 museum records) of ten species of the Agononida incerta complex in the Indo-West Pacific, largely in the Southern Hemisphere, separated into two clades, A and B; overlaid by a model-constrained maximumlikelihood phylogeny inferred from 6 COI and 5 16 S new sequences merged with previously produced molecular data. Bootstrap support values for species are given. Species of clade A – A. africerta, yellow circle (12); A. indocerta, red triangle (18); A. polycerta, blue square (4); A. vanuacerta, white triangle (2). Species of clade B – A. auscerta, black asterisk (11); A. incerta, blue square (20); A. madagascerta, black triangle (3); A. rubrizonata, red triangle (34); A. tasmancerta, white square (8). Numbers of records are in parentheses. A. tasmancerta does not appear in the phylogeny. Agononida incerta is likely to occur further north than these records indicate, as far as central Japan.

FIGURE 2. Colour photographs of living animals by T. - Y. Chan unless otherwise noted. a, Agononida africerta, paratype, Mozambique, MNHN IU- 2008 - 10190; b, A. auscerta, PNG, MNHN IU- 2011 - 2426; c, A. incerta, Taiwan (from Baba et al. 2009 and Poore & Andreakis 2012); d, A. indocerta, Western Australia, D. Evans (from Jones & Morgan 2002 and Poore & Andreakis 2012); e, A. madagascerta n. sp., paratype, Madagascar, MNHN IU- 2009 - 1891; f, A. norfocerta, PNG, MNHN IU- 2011 - 891; g, A. polycerta n. sp., French Polynesia, TARASOC stn DW 3377 (specimen not located), L. Corbari; h, A. rubrizonata, paratype, Taiwan (from Poore & Andreakis 2012); i, A. tasmancerta, New South Wales (specimen not located), Image # 741 reproduced from 35 mm slide courtesy of The Neville Coleman Collection.

FIGURE 8. Agononida polycerta n. sp. Holotype, supermale, 32 mm, MNHN IU- 2010 - 6095: a (top row), telson and detail of anterolateral margin; b, pereopod 1, upper and lateral views; c, abdominal somites (showing 1 ancillary spine on somite 4); d – f, dactyli of pereopods 2 – 4 (with robust setae magnified); g, merus of left pereopod 4 (showing 4 facial spines in proximal half); h, right pereopodal meri (pereopod 4 merus with 1 facial spine).