Salmoneus yoyo, Anker, Arthur, Firdaus, Muhammad & Pratama, Idham Sumarto, 2014

Anker, Arthur, Firdaus, Muhammad & Pratama, Idham Sumarto, 2014, Salmoneus yoyo nov. sp., a peculiar new infaunal shrimp from Lombok, Indonesia (Decapoda, Caridea, Alpheidae), Zootaxa 3852 (4), pp. 489-495 : 490-494

publication ID	https://doi.org/ 10.11646/zootaxa.3852.4.6
publication LSID	lsid:zoobank.org:pub:DD2AF714-03D7-4D69-8A4D-B6A4A6CB9261
DOI	https://doi.org/10.5281/zenodo.6144282
persistent identifier	https://treatment.plazi.org/id/D706380D-0357-6012-FF6B-01B5FD67F840
treatment provided by	Plazi
scientific name	Salmoneus yoyo
status	sp. nov.

Treatment

Salmoneus yoyo View in CoL sp. nov.

Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3

Type material. Holotype: non-ovigerous specimen (cl 4.0 mm), Indonesia, Lombok, Eastern Teluk Sekotong (Sekotong Bay), 8º44’26.45” S 116°01’24.60” E, shallow seagrass flat 20 m from large rocky area, in burrow, suction pump, depth: 0.2–0.4 m at low tide, leg. F. Muhammad, I.S. Pratama, D.L. Rahayu et al., 14 May 2013 [ MZB Cru 3986].

Description. Carapace smooth, with scattered setae. Rostrum triangular in dorsal view, longer than broad at base, reaching distal margin of second article of antennular peduncle, with tip acute; lateral margins shallowly concave; ventral margin without subdistal tooth; rostral carina not distinct ( Fig. 1 View FIGURE 1 A, B). Orbital teeth narrow, acute, directed slightly mesially, lateral to eyes in dorsal view ( Fig. 1 View FIGURE 1 A, B). Pterygostomial angle rounded ( Fig. 1 View FIGURE 1 B).

First to fourth abdominal somites rounded posteroventrally; fifth somite with slight blunt angle; sixth somite with feebly marked, incomplete suture at posteroventral angle, posterolateral margin subacutely projecting ( Fig. 1 View FIGURE 1 C), preanal plate rounded. Telson subrectangular, relatively narrow, tapering distally; dorsal surface covered with numerous setae and with two pairs of spiniform setae (anterior left spiniform seta lacking in holotype), anterior pair situated at about mid-length, posterior pair at about 0.7 length of telson, both pairs inserted at some distance from lateral margin; posterior margin nearly straight, with slight median emargination furnished with three plumose setae, and two pairs of stout spiniform setae, lateral half as long as mesial ( Fig. 1 View FIGURE 1 D).

Eyes mostly concealed in dorsal view except most-anterior portion, partly visible in lateral view ( Fig. 1 View FIGURE 1 A, B); cornea large and well-pigmented; anteromesial margin of eyestalk not protruding, without tubercle. Antennule with stylocerite reaching distal margin of second article, with acute tip; ventromesial carina of first article with relatively small, sharp, anteriorly directed tooth; second article stout, slightly wider than long; lateral flagellum bifurcating at first segment, secondary ramus well developed, densely furnished with several groups of thick aesthetascs ( Fig. 1 View FIGURE 1 A, B). Antenna with basicerite ending in stout distoventral tooth; scaphocerite broadly ovate, with small subacute distolateral tooth, blade broad, with convex anterior margin surpassing distolateral tooth; carpocerite stout, relatively short, reaching beyond half-length of scaphocerite; flagellum stout ( Fig. 1 View FIGURE 1 A, B).

Mouthparts not dissected. Second and first maxilliped appearing typical for genus. Third maxilliped slender; coxa with subrectangular lateral plate protruding towards enlarged arthrobranch; ultimate article tapering to corneous tip, without spiniform setae; exopod about as long as antepenultimate article ( Fig. 1 View FIGURE 1 E, F).

Chelipeds almost equal in size, but asymmetrical in shape; major1 (right) cheliped not noticeably longer than minor1 (left) cheliped, with shorter palm and longer fingers ( Figs. 2 View FIGURE 2 , 3 View FIGURE 3 ). Major cheliped with ischium widening distally, armed with stout spiniform seta on ventrolateral surface, ventromesial margin bluntly projecting distally; merus feebly inflated, depressed ventrally, ventromesial margin armed with six more or less evenly spaced, blunt teeth of various sizes, distal portion of ventromesial magin with conspicuous, hook-like process curving mesially; carpus cup-shaped, distally with two blunt dorsal lobes and one strongly projecting ventral process; chela subcylindrical, with fingers about 0.8 times as long as palm; palm depressed ventrally, ventromesial margin with six widely spaced tubercles distally, adjacent to pollex, diminishing in size posteriorly; fingers slender, not gaping when closed, with strongly curved, crossing tips; cutting edges serrated with about 11 subtriangular teeth, latter extending to about 0.6 of cutting edge length, distal 0.4 of cutting edge unarmed ( Fig. 2 View FIGURE 2 A–E). Minor cheliped with ischium, merus and carpus similar to those of major cheliped, ventromesial margin of merus with nine spaced rounded teeth, latter smaller in size compared to meral teeth of major cheliped; chela subcylindrical, with fingers about half as long as palm; palm depressed ventrally, ventromesial margin with five widely spaced tubercles distally, adjacent to pollex, distal-most and proximal-most tubercles smallest in size; fingers robust, somewhat gaping when closed, with strongly curved, crossing tips; dorsal margin slightly notched subdistally; cutting edges of dactylus armed with one strong subtriangular tooth, latter fitting into hiatus on opposed edge of pollex; pollex with two stout teeth, larger proximal and smaller subdistal ( Fig. 2 View FIGURE 2 F–I).

Second pereiopod slender; ischium with one small spiniform seta on ventrolateral margin; merus significantly longer than ischium, depressed ventrally; carpus slightly depressed ventrally, composed of five articles, first slightly longer than remaining four together; chela comparatively large, as long as distal four articles of carpus ( Fig. 1 View FIGURE 1 G). Third pereiopod moderately slender; ischium with one stout spiniform seta proximally on ventral margin and one smaller spinform seta more distally on ventrolateral surface; merus with slightly convex dorsal and ventral margins, about four times as long as wide, unarmed; carpus much more slender than merus, about half-length of merus, with short distoventral spiniform seta; propodus with two slender spiniform setae on ventral margin and one pair of stouter distal spiniform setae adjacent to dactylar base, lateral much stronger than mesial; dactylus simple, conical, moderately slender, slightly curving, about 0.4 of propodus length ( Fig. 1 View FIGURE 1 H). Fourth pereiopod generally similar to third, shorter, with more slender merus ( Fig. 1 View FIGURE 1 I). Fifth pereiopod shorter, unarmed ischium; merus with nearly straight margins, about 5.5 times as long as wide; carpus unarmed; propodus with two small spiniform setae on ventral margin, one pair of stouter spiniform setae adjacent to dactylar base, lateral much stronger than mesial, propodal grooming brush well developed, with four rows of thick setae, distal longest ( Fig. 1 View FIGURE 1 J).

Second pleopod with appendix interna and slightly shorter appendix masculina furnished with setae, as illustrated ( Fig. 1 View FIGURE 1 K, L). Uropod with protopod bearing subacute lateral lobe; exopod and endopod moderately broad; diaeresis deeply incised; distolateral spiniform seta stout, adjacent tooth rather small ( Fig. 1 View FIGURE 1 M).

Gill/exopod formula typical for genus.

Colour pattern. Body ground colour whitish-semitransparent; bright red chromatophores occupying most of carapace surface, except for frontal and post-frontal areas; abdomen, chelipeds, second to fifth pereiopods, pleopods and tail fan whitish; gonads yellow (note: carapace bright red immediately after capture due to expansion of chromatophores, after their contraction red colour less intense) ( Fig. 3 View FIGURE 3 ).

Etymology. The new species is named after Dr. Dwi Listyo Rahayu (Lembaga Ilmu Pengetahuan Indonesia = LIPI, Pemenang, Lombok, Indonesia), aka Yoyo for friends and colleagues, for her important contributions to South-East Asian carcinology and for organising the seagrass and mangrove survey in Lombok, diring which this new species of Salmoneus was collected; used as a noun in apposition.

Type locality. Sekotong Bay, Lombok, Indonesia.

Distribution. Presently known only from the type locality in Lombok, central Indonesia.

Biology. The holotype was collected with the aid of a suction (yabby) pump from a burrow of unknown burrowing host, on a partly exposed seagrass flat, about 30 m away from a large rocky area. Other burrows on this seagrass flat were inhabited by several species of burrowing snapping shrimps, e.g., Alpheus rapax Fabricius, 1798 and A. macellarius Chace, 1988 , and strahlaxiid shrimp lobsters, Neaxius glyptocercus (von Martens, 1869) (sensu Sakai 2011).

Remarks. Salmoneus yoyo sp. nov. is one of the most peculiar species in the genus Salmoneus , presenting several unique characters on the chelipeds. It is the only species of Salmoneus with rows of spaced blunt teeth or tubercles on both chelipeds, one on the ventromesial margin of the merus and one on the ventromesial margin of the propodus ( Fig. 2 View FIGURE 2 B, C, E, G, I). Another peculiar and unique feature within the genus and the family Alpheidae in general is the presence of a strong, mesially curved, hook-like process on the distomesial margin of the merus in both chelipeds ( Fig. 2 View FIGURE 2 B, D, G, E). These three cheliped features separate S. yoyo sp. nov. from all other previously described species of Salmoneus .

In the general shape and armature of the finger cutting edges of the chelipeds, S. yoyo sp. nov. approaches the western Atlantic S. degravei Anker, 2010 , the eastern Atlantic S. caboverdensis Dworschak, Anker & Abed- Navandi, 2000, S. erasimorum Dworschak, Anker & Abed-Navandi, 2000 , and the Indo-West Pacific S. brucei Komai, 2009 . The new species can be distinguished from all of them by the three aforementioned autapomorphic characters, as well as several additional, more specific characters, for instance, from S. degravei by the much stronger orbital teeth and proportions of both chelipeds (cf. Anker 2010); from S. caboverdensis by the absence of a strong process on the distolateral surface of the cheliped carpi (cf. Dworschak et al. 2000); from S. erasimorum by the different armature of the finger cutting edges of both chelipeds (cf. Dworschak et al. 2000); and from S. brucei by the presence of orbital teeth and absence of rows of long setae on the cheliped fingers (cf. Komai 2009). Salmoneus yoyo sp. nov. shows some resemblance to the eastern Atlantic Deioneus sandizelli Dworschak, Anker & Abed-Navandi, 2000 , from which it can be easily separated by several differences in the armature of the minor cheliped fingers, much stronger orbital teeth, and an incomplete posterolateral suture on the sixth abdominal somite (cf. Dworschak et al. 2000). The separation of Deioneus from Salmoneus and the validity of the former genus will be discussed elsewhere (Anker, in prep.).

Because of the presence of teeth and tubercles on the chelipeds, S. yoyo sp. nov. at first glance may be mistaken for a species of Athanas Leach, 1814 . However, the presence of a strap-like epipod on the fourth pereiopod and an arthrobranch on the third maxilliped, the absence of a clear posterolateral flap on the sixth abdominal somite, the emarginate posterior margin of the telson, and the general shape of the major cheliped (including serrated finger cutting edges) of S. yoyo sp. nov. are all characters typical for Salmoneus , which do not fit the generic diagnosis of Athanas , as redefined by Anker & Jeng (2007). In addition, the colour pattern of S. yoyo sp. nov. is very untypical of members of Athanas , including infaunal species (cf. Anker & Jeng 2007; Anker & Komai 2010; Anker 2011; Ďuriš & Anker 2014).