Machatrium wongat, Bruce, Niel L. & Buxton, Chad, 2013

Bruce, Niel L. & Buxton, Chad, 2013, Review of the marine isopod crustacean genus Hansenium Serov and Wilson, 1995 (Asellota: Stenetriidae) from tropical Australia and Papua New Guinea, with description of a new genus, Zootaxa 3664 (4), pp. 445-478 : 469-473

Machatrium wongat sp. nov.

( Figures 15–18 )

Material examined. All material from the Madang region, Papua New Guinea.

Holotype. 3 (3.8 mm), Madang, barrier reef south of Wongat Island, 5.1411°S, 145.8267°E, 3 May 1989, coral rock on buttress, 21–25 m, coll. N.L. Bruce & M. Jebb (MTQ W34001).

Paratypes. 3 3 (3.3; juv. 2.6, 2.7 mm), 4 Ƥ (ovig. 3.5–3.7; non-ovig 3.5, 3.6 mm), same data as holotype (MTQ W34002). 3 3 (3.3–4.0 mm), Ƥ (3.3 mm), Madang, Wongat Island, 5.1366°S, 145.8225°E, 25 April 1989, small rubble on sand, 10 m, coll. N.L. Bruce & M. Jebb (MTQ W34004). 3 3 (3.5; juv. 2.0, 2.4 mm), 4 Ƥ (ovig. 3.0, 3.5; non-ovig 3.1, 4.0 mm), Madang, outer reef south of Wongat Island, 5.1367°S, 145.8255°E, 21 April 1989, reef slope, dead coral on buttress, 27 m, coll. N.L. Bruce & M. Jebb (MTQ W34005). 2 3 (2.9, 3.2 mm), 5 Ƥ (3.2, 3.3, 3.6, 3.8; ovig. 3.9 mm), Madang, 5.1411°S, 145.8267°E, 3 May 1989, 21– 25 m, coll. N.L. Bruce & M. Jebb (MTQ W34003).

Description of male. Body length 3.9 as greatest width; pereonite 1 medial width 2.5 length; pleotelson length 1.0 width.

Cephalon length 0.6 width; lateral margins acute, sparsely setose; antennal spines rounded; eyes with 14–18 ommatidia, ommatidia orange, arranged in two parallel rows.

Antennula length 0.9 cephalon width; article 1 length 1.3 width, anterolateral margin with 1 large penicillate seta; article 2 length 1.6 width, 1 penicillate seta, anterolateral margin with 1 cluster of setae, 1 penicillate seta; article 3 length 2 width, medial margin with 1 cluster of setae, anterolateral margin with 1 cluster of setae; article 4 length 0.3 width, anterior margin with 3 short setae; flagellum with 14 articles, flagellar article 1 distinctly longer than other flagellum articles, length 1.6 flagellar article 2 length.

Mandible left spine row with 4 spines, right spine row with 9 spines; palp article 1 distolateral margin with 2 long setae; article 2 with submarginal row of 7 short serrate setae. Maxillula lateral lobe apex with 9 serrate setae; mesial lobe apex with 2 serrate setae. Maxilla mesial lobe mesial margin with 7 serrate setae. Maxilliped basis length 2.4 width, width 0.95 endite width; endite mesiodistal margin with 5 serrate setae, distal margin with 5 fan setae; palp article 2 length 0.8 basis width; epipod length 3.5 width, width 1.1 basis width, apex acute, mesial margin with 7 regularly spaced setae.

Pereopod 1 basis length 3.1 width, submarginal mesial ridge with regularly spaced setae along length. Ischium length 2.0 width; inferodistal margin with 2 short setae; superodistal margin produced, acute, densely covered with long setae; mediodistal margin with 1 long seta. Merus angular, length 1.1 width, length 1.3 carpus length; inferior margin densely covered with setae; inferodistal margin not produced; superodistal margin slightly produced, apex acute, densely covered with long setae. Carpus length 1.0 width; distal margin convex, without short setae; carpal process short, length 2.2 width, extending less than halfway to propodal palm articulation, tapering, triangular; inferior margin smooth, straight, densely setose, 1 row of stiff setae, 2 rows of long serrate setae; superior margin slightly convex, densely covered with setae. Propodus inferior half of article flattened, length 5.3 width; inferior margin length 0.7 superior margin length, densely covered with rows of long and serrate setae; superior margin sparsely setose, setae regularly spaced, restricted to distal two-thirds of margin, superior mesial surface densely covered with long, bi-denticulate setae; propodal palm parallel, margin with 3 medial teeth, row of long setae, row of short setae on each side of margin, cluster of setae at articulation, terminal end with single RS. Dactylus 3.8 times as long as basal width, length 1.1 propodal palm length, curved, distal margin setose, setae regularly spaced along entire length, opposing margin with regularly spaced rows of setae and serrate setae, mesial surface lightly setose. Pereopod 2 basis medial inferior margin with stiff seta absent, anterosuperior margin with 3 penicillate setae; ischium superior margin apex with 1 stiff seta; merus superodistal apex with 1 stiff seta, inferodistal margin with 1 long setae, 1 short seta; carpus superodistal margin with 3 short and long setae, 1 penicillate seta, inferior margin with 4 flagellated RS, inferodistal margin with 1 RS, and 3 setae; propodus superior margin with regularly spaced setae, superodistal margin with 1 penicillate seta, 2 long setae, inferior margin with 4 flagellated RS. Pereopod 7 basis superior margin with 4 penicillate setae, inferior margin with 1 stiff seta; carpus inferior margin with 1 flagellated RS, propodus inferior margin with 4 flagellated RS.

Pleopod 1 protopod length 0.9 width, lateral margins with greater than 1 seta, posterior lobes with pair of RS, surface setae absent; rami lateral margins with regular setae along distal half of margin, apex with clustered setae, ventral surface with setae. Pleopod 2 protopod length 3.1 width; lateral margin with 1–2 setae; endopod proximal segment length 0.6 protopod length, without setae; appendix masculina length 1.4 endopod proximal length, 0.8 protopod length, lateral margin without distal groove, apex concave, depression fringed with setae, interior pocket with fine setae, 5 anteriorly projecting distolateral spines, mesial margin without setae. Pleopod 3 endopod apex with 4 plumose setae. Pleopod 4 exopod apex with 7 plumose setae. Pleopod 5 apex with 4 plumose setae.

Uropods length 0.7 pleotelson length; protopod length 3.2 width; endopod length 1.1 protopod length, 2 latitudinal rows of sensillate setae, distal and sub-distal margins with 7 penicillate setae; exopod length 0.7 protopod length, 2 latitudinal rows of sensillate setae.

Female. Pereopod 1 basis length 3.0 times as long as wide, mesial submarginal ridge with regular short setae; ischium superodistal process developed, acute; merus superodistal process developed, acute; carpus inferodistal process rounded; propodus 3.1 times as long as wide, with one row of setae and one row of serrate setae; propodal palm length 1.6 times propodus proximal width, 4 teeth along margin, row of serrate setae present; dactylus length 3.4 width, length 1.0 propodal palm length, proximal margin with 11 denticulate setae.

Pleopod 2 length 1.5 width; lateral margins with 2–5 setae; apex notched, asymmetric, a seta on each lobe; ventral surface sparsely setose.

Size. Males 3.3–4.0 mm (mean 3.61, n=8), females ovig. 3.0–3.7 (mean 3.46, n=5).

Coloration. Cephalon with two small spots mesial to eyes, not adjoining, slightly posterior to anterior margin; pseudorostrum and dorsal surface of clypeus with pigmentation. Slight spotted pattern of pigmentation on all pereonites. Pleotelson with light reticulate pattern on anterior margin.

Distribution. Outer reef slopes at Madang, Papua New Guinea; at depths of 4 to 27 metres.

Remarks. Machatrium wongat sp. nov. can be identified by the male pereopod 1 having a relatively short and broadly sub-triangular carpal process and the propodal palm having three teeth.

Etymology. Named after Wongat Island, the type locality; noun in apposition.

Figures

FIGURE 15. Machatrium wongat sp. nov. A, B, male holotype (MTQ W 34001). A, dorsal view; B, dorsal view of cephalon; C – E, male paratype (MTQ W 34002); C, uropod; D, right antennula; E, right antenna articles.

FIGURE 16. Machatrium wongat sp. nov. All male paratype (MTQ W 34002). A, left mandible; B, left maxillula; C, right maxilliped; D, detail of maxilliped endite; E, left maxilla.

FIGURE 17. Machatrium wongat sp. nov. A, B, male holotype (MTQ W 34001). A, pereopod 1; B, enlargement of dactylus, pereopod 1; C, male paratype (MTQ W 34002), pereopod 2; D – G, female paratype (MTQ W 34002): D, pereopod 2; E, pereopod 1; F, enlargement of dactylus, pereopod 1; G, pereopod 7; H, I, male paratype (MTQ W 34002); H, pereopod 7; I, pereopod 6.

FIGURE 18. Machatrium wongat sp. nov. A – E, male paratype (MTQ W 34002). A, pleopod 1; B, pleopod 2, with detail of appendix masculina apex; C, pleopod 3; D, pleopod 4; E, pleopod 5; F, female paratype (MTQ W 34002), pleopod 2.