Salmoneus kausti, Anker, 2022

Anker, Arthur, 2022, Three new species of the shrimp genus Salmoneus Holthuis, 1955 from the Red Sea, with a new record of S. poupini Anker, 2010 (Malacostraca: Decapoda Alpheidae), Zootaxa 5138 (3), pp. 261-282 : 271-275

Salmoneus kausti sp. nov.

( Figs. 7–9 )

Salmoneus aff. seticheles – Ďuriš & Horká, 2016: 787, fig. 14.

Type material. Holotype, non-ovig. specimen (cl 3.4 mm), FLMNH UF 36066 , Red Sea , Saudi Arabia, Thuwal , KAUST South Beach near Marine Academy, 22°17'30.4"N, 39°05'17.1"E, sand flat near sparse mangrove, in burrow, depth: 0.5–1 m, leg. A. Anker et al., 15.03.2013 [fcn BDJRS-2813].

Description. Small-sized shrimp with moderately slender, non-compressed body. Carapace ( Fig. 7a, b ) smooth, glabrous, completely covering eyes dorsally and almost completely laterally; anterolateral suture present; pterygostomial angle broadly rounded; cardiac notch deep. Rostrum ( Fig. 7a, b ) subtriangular, as long as broad, with acute tip, latter only slightly overreaching distal margin of first article of antennular peduncle; lateral margins slightly concave; rostral carina absent; ventral margin unarmed. Orbital teeth ( Fig. 7a, b ) well developed, almost 0.25 of rostrum length, narrow, acute, extending well beyond eyes, directed mesially in dorsal view, anteriorly in lateral view.

Eyestalks with cornea significantly reduced, occupying relatively small portion of distal surface; anterodorsal margin angular, without triangular process ( Fig. 7a, b ). Epistomial sclerites each with acute process.

Pleon ( Fig. 7c ) with pleura of first to third pleonite rounded antero- and posteroventrally; fourth pleuron with blunt posteroventral angle; fifth pleuron subacutely produced posteroventrally; sixth pleonite with subacute subtriangular projection flanking base of telson, oblique suture at posteroventral angle not distinct; preanal plate rounded, with median depression.

Telson ( Fig. 7d ) moderately slender, subrectangular, tapering distally, about 2.6 times as long as proximal width; dorsal surface with two pairs of stout spiniform setae situated at about 0.5 and 0.7 telson length, respectively; posterior margin with two pairs of long stout spiniform setae, mesial longer than lateral, and very small U-shaped median notch, latter flanked by two slender plumose setae.

Antennular peduncle ( Fig. 7a, b, e ) relatively stout; dorsally visible portion of first article longer than wide; stylocerite narrow, with acute tip, latter almost reaching distal margin of second article; ventromesial carina with small tooth; second article subquadrate, about as long than wide; lateral antennular flagellum biramous, with fused portion composed of three short subdivisions; shorter free ramus with four poorly demarcated subdivisions each furnished with bundle of long aesthetascs. Antenna ( Fig. 7a, b, f ) with basicerite stout, armed with large subacute distoventral tooth; scaphocerite reaching end of antennular peduncle, ovate, about twice as long as broad; distolateral tooth falling short of distal margin of blade; carpocerite very short, barely reaching half-length of scaphocerite; flagellum not particularly thickened, moderately slender.

Third maxilliped ( Fig. 7g ) slender; coxa with strap-like epipod and prominent rounded lateral plate; antepenultimate article about 2.5 times as long as penultimate article; penultimate article moderately long, about three times as long as wide; ultimate article tapering distally, ending in apical corneous tooth, without spiniform setae; exopod well developed, reaching distal margin of antepenultimate article; arthrobranch normally developed, not enlarged.

First pereiopods = chelipeds ( Fig. 8 ) very different in shape, asymmetrical in size. Major cheliped ( Fig. 8a–c ) slender, carried flexed under body at rest; ischium slender, slightly widening distally, about 3.5 times as long as distal width, armed with one spiniform seta on ventrolateral surface; merus long, slender, almost straight, faintly widening distally, about six times as long as distal width, somewhat depressed ventrally; carpus cup-shaped, slightly elongate, with blunt distal lobes and short blunt ventromesial process; chela feebly enlarged and swollen, slightly longer than merus, with smooth surfaces; palm about twice as long as maximal width, subcylindrical, with deep transverse groove proximo-ventrally; distoventral margin of palm with long fine setae continuing onto pollex; fingers 1.2 length of palm, not gaping when closed, somewhat twisted mesially, with strongly crossing fingertips; cutting edges with about 17 small rounded teeth in form of continuous serration (except for edges near fingertips), distal teeth gradually becoming smaller; ventral margin of pollex and dorsal margin of dactylus fringed with long fine setae. Minor cheliped ( Fig. 8d, e ) much smaller and weaker than major cheliped; ischium about three times times as long as wide, armed with one stout spiniform seta on ventrolateral margin; merus distinctly longer than ischium, slightly expanded, about 3.5 times as long as maximal width, flattened distoventrally; carpus subcylindrical, about 0.6 length of merus, widening distally; chela about 1.2 length of carpus; palm as long as fingers, slightly swollen; finger cutting edges straight over most of their length, with one minute tooth on pollex and similar one on dactylus at about 0.7–0.8 finger length, respectively; small subdistal gape present between these teeth subdistally.

Second pereiopod ( Fig. 7h ) relatively short, slender; ischium about five times as long as wide, with one spiniform seta on ventrolateral surface, at about 0.4 of ischial length; merus distinctly longer than ischium; carpus with five subarticles, proximal subarticle longer than combined length of remaining ones; length ratio of carpal subarticles approximately equal to 6: 1.2: 1: 1: 2.

Third pereiopod ( Fig. 7i, j ) moderately slender; ischium elongate, about 3.7 times as long as wide, with two stout spiniform setae on ventrolateral surface; merus about 1.6 times as long as ischium, about five times as long as maximal width; carpus distinctly slenderer than merus, about 0.6 length of merus, with small spiniform seta on distoventral margin; propodus subequal to carpus in length, with three widely spaced, short spiniform setae along ventral margin and one pair of longer spiniform setae on distoventral margin, near dactylar base; dactylus relatively slender, gently curved, conical, about 0.4 length of propodus. Fourth pereiopod ( Fig. 7k ) generally similar to third pereiopod, slenderer. Fifth pereiopod ( Fig. 7l, m ) slenderer than third and fourth pereiopods; ischium about 2.7 times as long as wide, unarmed; merus almost seven times as long as maximal width; carpus shorter than merus, slenderer, with small spiniform seta on distoventral margin; propodus about 1.6 times as long as carpus, with two spiniform setae on proximal half of ventral margin and one pair of long spiniform setae on distoventral margin, near dactylar base; propodal cleaning brush moderately developed, occupying distal half of propodus, composed of dozen or so transverse rows of microserrulate setae; dactylus slender, conical, curved, about 0.4 length of propodus.

Second pleopod with appendix masculina about 0.6 length of appendix interna ( Fig. 7n ). Uropod ( Fig. 7o ) with lateral lobe of protopod produced into sharp tooth; exopod moderately broad, ovate, with slender spiniform seta flanked by well-developed subacute distolateral tooth and prominent subtriangular lateral tooth of otherwise almost straight diaeresis; endopod as long as exopod, slightly narrower, without specific features.

Colour in life. Semi-transparent white with pale yellow tinge; yellow-orange inner organs visible by translucence of carapace ( Fig. 9 ).

Type locality. Thuwal , Saudi Arabia .

Distribution. Red Sea: presently known only from Thuwal, Saudi Arabia.

Ecology. The holotype was collected on a shallow (less than 1 m), near-shore sand flat, with some silty and muddy patches and about 50 to 100 m distant from some young mangrove trees; the shrimp was associated with a burrow of an unknown host.

Etymology. The new species name refers to the King Abdullah University of Science and Technology (KAUST) in Thuwal; the type locality of S. kausti sp. nov. is in fact situated on the KAUST campus.

Remarks. One of the most important diagnostic features of Salmoneus kausti sp. nov. is the presence of long fine setae on the ventral margin of the pollex and dorsal margin of the dactylus of the major cheliped ( Fig. 8b, c ). Only four other species of Salmoneus share this feature with S. kausti sp. nov.; these species are S. seticheles Anker, 2003 , S. brucei Komai, 2009 , S. durisi and S. spiridonovi Marin, 2021 ( Anker 2003; Komai 2009; Anker & Ashrafi 2019; Marin 2021).

Salmoneus kausti sp. nov. is distinguishable from S. seticheles by the much shorter appendix masculina, barely reaching the mid-length of the appendix interna (vs. reaching far beyond the tip of the appendix interna and even beyond the distal margin of the endopod in S. seticheles ); the presence of a stout spiniform seta on the ischia of the major and minor chelipeds (which are absent in S. seticheles ); the presence of a stout spiniform seta on the ischium of the second pereiopod (which is absent in S. seticheles ); the dactyli of the third to fifth pereiopods noticeably stouter and shorter (vs. elongate and slender in S. seticheles ); and the uropodal exopod with a strong lateral tooth on the diaeresis (vs. with a much smaller tooth in S. seticheles ) ( Anker 2003). The new species can be easily separated from S. brucei , for instance, by the well-developed extra-corneal teeth (which are absent in S. brucei ), as well as several features on the chelipeds, including the non-enlarged minor cheliped, the less swollen major chela, and the presence of spiniform setae on the ischia of both chelipeds (which are lacking in S. brucei ) ( Komai 2009). Along the same lines, S. kausti sp. nov. can be distinguished from both S. durisi and S. spiridonovi by the non-enlarged, unarmed minor cheliped, which is substantially larger, stouter and armed with large teeth on the finger cutting edges in S. durisi and S. spiridonovi ; from S. durisi by the rostrum narrower, laterally broadly concave (vs. broader, laterally slightly convex in S. durisi ), and the presence of spiniform setae on the ischia of the major and minor chelipeds, as well as on the ischium of the second pereiopod (which are unarmed in S. durisi ); and from S. spiridonovi by the unarmed ventral margin of the rostrum (vs. armed with a small subdistal tooth in S. spiridonovi ), the unarmed and dorsally concealed eyes (vs. armed with a triangular tubercle and dorsally partly exposed in S. spiridonovi ), as well as by the uniform whitish body colour (contrasting with the diffuse but bright red transverse bands in S. spiridonovi ) ( Anker & Ashrafi 2019; Marin 2021).

Salmoneus kausti sp. nov. is not closely related to the two above-described species, viz. S. farasan sp. nov. and S. arabicus sp. nov., presenting a series of obvious differences on the major cheliped (cf. Figs. 2 , 5 and 8 ). The only species of Salmoneus , in which a single detached major cheliped is presently unknown is S. hilarulus ( De Man, 1910) , which can be easily separated from S. kausti sp. nov. by the very stout dactylus of the third pereiopod and the posterior position of the dorsal spiniform setae on the telson ( De Man 1911). The record of S. aff. seticheles from an unknown locality in the Red Sea (“Mer Rouge”) by Ďuriš & Horká (2016), which was based on a single detached major cheliped, most likely refers to S. kausti sp. nov., although the presence of S. seticheles in the Red Sea cannot be totally excluded at this stage.

Figures

FIGURE 2. Salmoneus farasan sp. nov., holotype, ovigerous specimen (cl 3.7 mm) from the Farasan Islands, Saudi Arabia (FLMNH UF 36951): a—major (right) cheliped, lateral; b—same, mesial; c—same, carpus and chela, dorsomesial; d—same, chela fingers, dorsomesial; e—minor (left) cheliped, lateral; f—same, carpus and chela, mesial.

FIGURE 5. Salmoneus arabicus sp. nov., holotype, ovigerous specimen (cl 2.8 mm) from Al Fahal Reef off Thuwal, Saudi Arabia (FLMNH UF 35964): a—major (left) cheliped, mesial; b—same, lateral; c—same, chela, dorsomesial; d—minor (right) cheliped, lateral.

FIGURE 7. Salmoneus kausti sp. nov., holotype, non-ovigerous specimen (cl 3.4 mm) from Thuwal, Saudi Arabia (FLMNH UF 36066): a—frontal region, dorsal; b—same, lateral view; c—fourth, fifth and sixth pleonites, lateral; d—telson, lateral; e—ventromesial tooth of first article of antennular peduncle, lateral; f—antennal scaphocerite, dorsal; g—third maxilliped, lateral; h—second pereiopod, lateral; i—third pereiopod, lateral; j—same, propodus and dactylus, mesial; k—fourth pereiopod, lateral; l—fifth pereiopod, lateral; m—same, propodus and dactylus, mesial; n—uropod, dorsal.

FIGURE 8. Salmoneus kausti sp. nov., holotype, non-ovigerous specimen (cl 3.4 mm) from Thuwal, Saudi Arabia (FLMNH UF 36066): a—major (right) cheliped, mesial [detached]; b—same, lateral; c—same, chela, dorsomesial; d—minor (left) cheliped, lateral; e—same, carpus and chela, mesial.

FIGURE 9. Salmoneus kausti sp. nov., holotype, non-ovigerous specimen (cl 3.4 mm) from Thuwal, Saudi Arabia (FLMNH UF 36066), shrimp in life, lateral. Photograph by the author.