Bioacoustics of Mursia arabica

Description. Carapace transversely subovate, convex, regions poorly marked, 1.3 wide as long (excluding lateral spines). Dorsal surface covered with uniformly-sized closely-spaced rounded granules. Conic, granular protuberances, diminishing in size posteriorly, disposed in 7 radial rows on dorsal surface of carapace. Mesogastric region highest part of carapace. Gastric, cardiac, intestinal regions separated from branchial regions by shallow, sinuous longitudinal grooves. Anterolateral margin arcuate, crenulate, with 11–12 granular triangular denticles. Lateral spine slim, acuminate, slightly curved forward, upward, about one tenth carapace width, minutely granular on upper surface. Posterolateral margins closely beaded, undulate, sharply convergent. Posterior margin beaded, lateral teeth broadly triangular, dorsoventrally flattened, median lobe obsolescent. Front as wide as orbit, setose. Frontal margin projecting beyond orbits, trilobate, median lobe on lower plane than lateral lobes, triangular, tip upcurved; lateral lobes rounded, separated from supraorbital margin by shallow concavity. Antennules obliquely folded. Supraorbital margin with single fissured, closely beaded, with long plumose setae. Inner orbital tooth ogival, separated from outer orbital margin by U-shaped cleft, by orbital hiatus from front. Antennae small, slender, basal segment article subrectangular, lodged in orbital hiatus. Eyes retractable, eyestalk short, granular, setose. Buccal frame rhomboidal, narrowing anteriorly. Third maxilliped exopod thickly fringed with plumose setae; ischium endopod bears granular row distally that forms stridulating organ when rasped against milled ridge on dactylus of chela. Subhepatic region tomentose. Sternum granular. Male abdomen with prominent trilobate carina on second somite, rounded lateral lobes separated from lower, wider median lobe by deep grooves; somites 3–5 fused; sixth somite subquadrate, lateral margins sinuous; telson triangular, slightly shorter than sixth somite. Female abdomen with somites 3–6 articulated; sixth abdominal somite trapezoidal, lateral margins sinuous, distally with rounded concavities fitting conic ‘buttons’ raised on margins of abdominal cavity; telson ogival, as long as sixth somite. Chelipeds massive, subequal. Merus dorsodistally bispinose, distal spine longer, stouter than subdistal spine. Antero-distal margin of carpus ending in triangular denticle. Upper margin of manus crested, setose, with 7 denticles, 3 proximal teeth successively larger, distal teeth laciniate. External surface of manus with rounded granules, 3 granular conic tubercles horizontally in mid chela; keel-like, indistinctly trilobate ridge above lower margin, proximal lobe triangular, margin minutely granular. Lower margin granular, serrate, serrations successively smaller proximally. Internal surface of manus with tomentose band near lower margin. Upper margin of dactylus crested, setose, proximally prominently granular; inner surface of dactylus with stridulating ridge consisting of about 30 striae, elongated, closely stacked proximally, rounded, spaced in distal half. Right chela with curved rounded tooth proximally fitting into depression in molariform tooth in pollex. Pereiopods 2–5 long, slender, laterally compressed; upper, lower margins of meri 2–5 minutely granular; carpi 2, 3 with 3 granular carinae, middle carina more prominently granular, distally spinose, carpus 4 with 2 granulate carina, distally spinose, carpus 5 with obsolete carinae, lacking terminal spine; propodi 2–4 with cristate, granular upper margin, crested upper margin of fifth P5 propodus smooth, slanted posteriorly; dactyli longer than propodi, styliform, fluted, tips corneous. First male gonopod tapering evenly, curved, distally spinous ( Fig. 9 a–d). Second male gonopod long, slender; corneous distal portion tightly crook-shaped, tip twisted inwards, up-curved ( Fig. 7 c, d). Female abdominal cavity densely set with minute setae, distally (covered by telson) with patches of longer setae. Vulva covered with subhemispherical hard cap laterally bordered by smooth protuberance, triangular knob mesially.