Metacrangon poorei, Komai & Taylor, 2010

Komai, T. & Taylor, J., 2010, Three new species of the crangonid genus Metacrangon Zarenkov (Crustacea: Decapoda: Caridea) from Australia, Memoirs of Museum Victoria 67, pp. 45-59 : 49-52

Metacrangon poorei sp. nov.

Figures 4, 5

Material examined. Holotype: Australia, off southeastern Victoria, (39°53.76'S, 149°03.39'E), 1608 m, 28 Apr 2000, FRV Southern Surveyor , epibenthic sled, (stn SS01/00/246), NMV J52069 (1 female, cl 8.1 mm).

Description. Based on holotype female. Body (figs 4a–e) moderately robust. Rostrum (figs 4a–b, 5a) triangular with acute apex in dorsal view, strongly ascending (angle against horizontal plane of carapace about 45°), 0.20 times as long as carapace; dorsal surface with low, but clearly delimited middorsal carina; lateral margin faintly sinuous in lateral view, merging into postorbital region of carapace; midventral carina distinct, ventral margin sinuous in lateral view. Carapace (figs 4a–b) not widened posteriorly, longer than wide postorbitally; dorsal midline with two moderately small teeth; anterior (epigastric) tooth arising at 0.18 of carapace length, posterior (cardiac) tooth broken off, arising at 0.68 of carapace length; submedian and hepatic teeth moderately small; antennal tooth moderately strong, directed forward in dorsal view, strongly ascending (same degree as rostrum) in lateral view, acuminate, falling slightly short of rostral apex; orbital cleft distinct; anterolateral margin between antennal and branchiostegal teeth concave, unarmed; branchiostegal tooth moderately strong, directed forward in dorsal view, strongly ascending in lateral view, reaching dorsodistal margin of antennal basicerite; pterygostomial tooth small, clearly visible in lateral view; postorbital carina clearly delimited, accompanied by longitudinal suture; epibranchial carina weakly absent.

Fifth to eighth thoracic sternites each with distinct median keel: on fifth, spiniform, directed forward; on sixth, terminating anteriorly in tiny tooth; on seventh, angulated anteriorly; and on eighth, rounded.

Abdomen (figs 4c–e) slightly sculptured, surface sparsely punctate; first somite with trace of middorsal carina, second to fourth somites with rather broad, clearly delimited middorsal carina. Pleuron of anterior four somites rounded marginally. Fifth somite with low, rather broad, clearly delimited middorsal carina; posterodorsal margin faintly produced medially; posterolateral margin unarmed; pleuron with posteroventral angle rounded, ventral margin gently convex. Sixth somite 1.7 times longer than wide, with distinct, slightly curved submedian carinae, not reaching posterodorsal margin; dorsolateral carina distinct, reaching to posterodorsal margin; posterodorsal margin produced, weakly bilobed; pleuron flared laterally, posteroventral tooth small; posterolateral process moderately strong, directed slightly laterally, terminating in sharp tooth. Telson (fig. 4d) damaged, but one pair of dorsolateral spines still preserved.

Eye (figs 4a, 5a) slightly longer than wide; cornea as wide as proximal part of eyestalk, darkly pigmented, corneal width 0.17 of carapace length; eyestalk with small, papilla-like dorsal tubercle.

Antennular peduncle (figs 4a, 5a) moderately stout. First segment with prominent, blunt distolateral process directed dorsally; distomesial margin unarmed; stylocerite just reaching tip of distolateral process, subacutely pointed, lateral margin gently convex. Second segment slightly widened distally, distinctly longer than wide, with prominent, blunt distolateral process. Third segment wider than long. Outer flagellum consisting of 10–11 articles.

Antennal basicerite (fig. 5a) stout, with rounded dorsodistal lateral angle and long ventrolateral tooth distinctly overreaching dorsodistal lateral angle. Antennal scale damaged (fig. 5a).

Third maxilliped (fig. 5b) relatively slender, overreaching antennal scale by 0.6 length of ultimate segment; ultimate segment gradually tapering distally,6.0 times longer than wide; penultimate segment about 2.7 times longer than wide; antepenultimate segment with two unequal spiniform setae subdistally.

First pereopod (figs 5c–d) moderately stout; palm 3.5 times longer than wide, not widened proximally or distally; lateral and mesial margins faintly sinuous; thumb moderately broad; carpus with small ventrolateral tooth, otherwise unarmed on lateral margin; merus with small dorsodistal tooth, ventral margin sinuous, crested. Second pereopod (fig. 5e) with dactylus about 0.5 times as long as palm; length ratio of chela to ischium 1:1.7:1.6:1.5. Third pereopod (fig. 5f) slender; length ratio of dactylus to ischium 1:1.9:3.4:2.5:2.6. Fourth pereopod (fig. 5g) moderately stout; dactylus (fig. 5h) narrowly spatulate, about 0.6 times as long as propodus, margins naked; dactylus–propodus articulation about 30°; propodus about 5.0 times longer than wide; carpus shorter than propodus, with numerous long setae on dorsal margin; row of long setae on dorsal and ventral margins of merus and ischium (dorsal setae longer than ventral setae). Fifth pereopod (fig. 5i) slightly shorter than fourth pereopod; dactylus slender, subspatulate, longer than dactylus of fourth pereopod, about 0.8 times as long as propodus.

Uropodal exopod with minute posterolateral tooth and minute spinule just located mesial to posterolateral tooth ( Fig. 5j).

Colouration. Not known.

Distribution. Known only from the type locality off southeastern Victoria, at a depth of 1608 m.

Remarks. Metacrangon poorei sp. nov. is morphologically very similar to M. variabilis ( Rathbun, 1902) from the northeastern Pacific and M. proxima Kim, 2005 from Japan in the disposition of teeth on the carapace and the development of the middorsal carina of the abdomen. Nevertheless, the new species is easily distinguished from the latter two species by the following characters: the rostrum is acutely pointed and reaches to the distal corneal margins in M. poorei , whereas it is blunt or subacute at the tip and falls far short of the distal corneal margins in the latter two species; the anterolateral angle of the postorbital carina is rounded in M. poorei , rather than bearing a small triangular tooth or denticle in the latter two species; the lateral carina on the fifth abdominal somite is obsolete in M. poorei sp. nov, but it is distinct in the latter two species; and the stylocerite of the antennule reaches the distolateral process on the first peduncular segment in the new species, rather than falling far short of it in the latter two species.

Etymology. It is our pleasure to dedicate this new species to our esteemed colleague, Dr. Gary C. B. Poore.