Salmoneus pinguis, Komai, Tomoyuki & Anker, Arthur, 2012

Komai, Tomoyuki & Anker, Arthur, 2012, A distinctive new species of the alpheid genus Salmoneus Holthuis, 1955 (Crustacea: Decapoda: Caridea) from the northwestern Pacific, Zootaxa 3344, pp. 60-68 : 61-67

publication ID	https://doi.org/ 10.5281/zenodo.281468
DOI	https://doi.org/10.5281/zenodo.6167410
persistent identifier	https://treatment.plazi.org/id/03E2878C-8C7F-7602-FF2E-A1D0E159EEB9
treatment provided by	Plazi
scientific name	Salmoneus pinguis
status	sp. nov.

Treatment

Salmoneus pinguis View in CoL sp. nov.

Figs. 1–6 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6

Type material. Holotype: ovigerous specimen (cl 5.7 mm), Japan, Ryukyu Archipelago, Okinawa Island, Manza, depth 2 m, cracking of coral rocks with a hammer, 1 July 2011, coll. N. Shirakawa, CBM-ZC 10666.

Additional material examined. 1 non-ovigerous specimen (cl 3.0 mm), Philippines, Bohol Sea, Panglao Island, Station B8, Napaling, 9°37.1'N, 123°46.1'E, depth 3 m, subtidal reef platform, dead coral and rubble brushing, 7 June 2004, coll. Panglao 2004 Marine Biodiversity Project, MNHN-IU-2010-5564.

Description (based on holotype). Body stout, bulky, plump, with relatively soft integuments. Carapace glabrous, conspicuously domed dorsally, steeply sloping anteriorly into rostrum; anterolateral region without distinct suture, however, with shallow notch on anterolateral margin dorsal to rounded pterygostomial angle ( Fig. 1 View FIGURE 1 ); posterior margin with deep cardiac notch. Rostrum very short, broadly triangular, with rounded tip, reaching distal margin of second article of antennular peduncle, strongly deflexed; dorsal surface smooth, without a distinct carina; ventral surface flattened, unarmed ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 A, C). Orbital teeth absent ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 A, C).

Pleura of first four abdominal somites enlarged, rounded posteroventrally; fourth pleuron greatly overlapping fifth pleuron, latter with rounded posteroventral angle ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 A); sixth somite without distinct articulated flap, with very faint suture only ( Fig. 2 View FIGURE 2 D); preanal plate rounded. Telson relatively broad, widest at base, posteriorly tapering; dorsal surface with two pairs of minute spiniform setae inserted at some distance from lateral margin, located at about 0.63 and 0.82 telson length, respectively; posterior margin approximately half as long as anterior margin, with moderately deep, U-shaped, median incision, two pairs of long spiniform setae on either side of median incision (mesial ones slightly longer and stouter than lateral ones), and one pair of long stiff setae arising from lateral margins of median incision ( Fig. 2 View FIGURE 2 B, E).

Eyestalks stout, short, concealed in dorsal view, fully visible in lateral view ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 A, C); cornea somewhat reduced, occupying only dorsolateral part of eyestalk ( Fig. 2 View FIGURE 2 F). Epistomial sclerites without conspicuous processes.

Antennular peduncles widely separated basally, short, stout, with second article slightly wider than long; first article without distinct tooth on ventromesial carina; stylocerite with subacute tip reaching distal margin of second article; lateral flagellum biramous, fused portion short, with two or three very short articles; accessory ramus consisting of four articles with aesthetascs; both flagella setose ( Fig. 2 View FIGURE 2 C). Antenna with basicerite ending in short subacute tooth distolaterally, with prominent, blunt process distodorsally; scaphocerite more rounded than ovate, short, 1.4 times longer than wide, reaching distal margin of third article of antennular peduncle; distal margin of blade broad, rounded, reaching well beyond small, subacute, distolateral tooth; carpocerite very short, stout, barely reaching mid-length of scaphocerite; flagellum conspicuously setose ( Figs. 2 View FIGURE 2 A, C; 3A).

Mouthparts fairly typical for genus. Mandible with moderately strong molar process bearing setal rows on dorsal surface; incisor process strong, distal margin with seven teeth, latter unequal in size; palp flattened, with oval distal article ( Fig. 3 View FIGURE 3 B–E). Maxillule with slender, inwardly curved coxal endite; basial endite curved, armed with two rows of slender spinules on distal margin; endopod strongly curved, ventral lobe bearing one stiff apical seta, dorsal lobe broad, rounded, with smaller setae ( Fig. 3 View FIGURE 3 F, G). Maxilla comparatively small; coxal endite not reaching basial endite; basial endite divided into two subequal, subquadrate lobes; endopod stout, tapering distally; scaphognathite with short, rounded posterior lobe ( Fig. 3 View FIGURE 3 H). First maxilliped with a few short setae on mesial margin of coxal endite; basial endite distally rounded; endopod biarticulated, consisting of broad basal article and slender, distally tapering distal article; exopod with narrow caridean lobe, flagellum well developed; epipod moderately large, subquadrate ( Fig. 3 View FIGURE 3 I, J). Second maxilliped with prominently produced mesial margin of coxa; propodus and dactylus apparently partly fused (articulation distinct only dorsally); exopodal flagellum well developed, with one long, stiff seta on lateral margin proximal to mid-length; epipod suboval ( Fig. 3 View FIGURE 3 K).

Third maxilliped slender, falling short of distal margin of antennal scale when fully extended; coxa with ovate lateral plate above mastigobranch; antepenultimate article longer than penultimate and ultimate articles combined; penultimate article about 2.5 times as long as wide, slightly widening distally, with two transverse rows of serrulate setae distomesially; ultimate article tapering distally, with transverse rows of thick serrulate setae mesially, apex with at least one small spiniform seta; exopod falling short of distal margin of antepenultimate article ( Fig. 4 View FIGURE 4 A–C); arthrobranch well developed (not drawn in Fig. 4 View FIGURE 4 A).

Chelipeds short relative to body and other pereopods ( Fig. 1 View FIGURE 1 ), slightly unequal in size, asymmetrical in shape ( Fig. 4 View FIGURE 4 D, F); minor (right) cheliped about 0.9 length of major (left) cheliped, with stouter ischium and merus, comparatively longer carpus, and significantly smaller and shorter chela ( Fig. 4 View FIGURE 4 F, G); both chelipeds capable of folding under cephalothorax when not in use (therefore mostly invisible in Fig. 5 View FIGURE 5 ). Major cheliped reaching beyond distal margin of antennal scale, slender; ischium not widening distally, unarmed on ventrolateral surface; merus about 5.2 times as long as wide, smooth, compressed laterally; carpus short, cup-shaped, about 0.3 merus length; chela somewhat compressed, smooth, mesial margin slightly concave; palm with deep proximal constriction; fingers distinctly longer than palm, terminating in blunt, slightly bulbous, curving and crossing tips; cutting edges of both dactylus and pollex with row of low, blunt teeth ( Fig. 4 View FIGURE 4 D, E). Minor cheliped with ischium lacking spiniform seta on ventrolateral surface; merus about 3.5 times as long as wide, smooth, dorsal margin slightly convex, ventral surface shallowly sulcate in distal half; carpus elongate, slightly shorter than merus, distally widening; chela smooth, simple, with slightly swollen palm; fingers moderately stout, in length subequal to palm; cutting edges smooth, unarmed; tips slightly curved, not strongly crossing ( Fig 4 View FIGURE 4 F, G).

Second pereopod slender; ischium without spiniform setae; merus slightly longer than ischium; carpus fourarticulated (but see under Variation), ratio of carpal articles (from proximal to distal) approximately equal to: 2.5: 0.4: 0.5: 1.0; chela simple, slightly longer than distal-most carpal article ( Fig. 4 View FIGURE 4 H). Third pereopod relatively stout, compressed laterally; ischium with two tiny spiniform setae on ventrolateral surface; merus about 3.2 times as long as wide, unarmed, with stiff setae along on dorsal margin; carpus more slender than merus, about 0.8 merus length, with stiff setae on dorsal surface; propodus with one spiniform seta on ventral margin distal to mid-length and one pair of stouter, longer spiniform setae on distoventral margin, dorsal margin with rows of stiff setae; dactylus about 0.4 times as long as propodus, simple, moderately slender, slightly curving distally, unguis clearly demarcated ( Fig. 4 View FIGURE 4 I, J). Fourth pereopod generally very similar to third pereopod ( Fig. 4 View FIGURE 4 K). Fifth pereopod in length subequal to third pereopod, however, with longer carpus and propodus combined; ischium unarmed; merus in length subequal to carpus; propodus with two spiniform setae and about five rows of short, serrulate setae in distal 0.4, distoventral margin with two slender spiniform setae ( Fig. 4 View FIGURE 4 L).

Second pleopod with appendix masculina about half-length of appendix interna, its apex and mesial margin being furnished with stiff setae ( Fig. 3 View FIGURE 3 L). Uropod with lateral lobe of protopod unarmed; endopod and exopod narrowly ovoid; diaeresis on exopod not distinct; exopod with minute distolateral tooth adjacent to slender spiniform seta ( Fig. 3 View FIGURE 3 M).

Gill-exopod formula typical for genus.

Colour in life. Semitransparent, with yellowish tinge; ovary and eggs bright yellow-orange ( Fig. 5 View FIGURE 5 ). Variation. The apparently post-ovigerous specimen from Panglao is much smaller than the holotype (cl 3.0 mm compared to cl 5.7 mm in the holotype) and differs from the latter by the more triangular rostrum ( Fig. 6 View FIGURE 6 A), the eyestalks being more concealed in lateral view ( Fig. 6 View FIGURE 6 B), the second pereopods with a five-articulated carpus (vs. four-articulated in the holotype) ( Fig. 6 View FIGURE 6 D), and the third pereopod with a somewhat more slender dactylus, and with two spiniform setae on the ventral margin of the propodus (vs. one in the holotype) ( Fig. 6 View FIGURE 6 E). In all other features, this specimen agrees well with the holotype, including all of the new species’ diagnostic features, such as the stout, plump body; the general shape of the frontal margin of the carapace (including the absence of orbital teeth); the general shape and proportions of the antennules and antennae, including their setose flagella ( Fig. 6 View FIGURE 6 A); the general shape and details of the major cheliped, including the very diagnostic blunt fingertips of the major chela ( Fig. 6 View FIGURE 6 C); the proportions and ischial armature of the third pereopod ( Fig. 6 View FIGURE 6 E), and the general shape and dorsal armature of the telson. Therefore, the Panglao specimen is tentatively assigned to S. pinguis sp. nov., awaiting collection of more specimens in both the Philippines and southern Japan.

Etymology. From the Latin word “ pinguis ”, meaning bulky, plump, referring to the new species’ general body shape.

Type locality. Manza, Okinawa Island, Ryukyu Archipelago, Japan.

Distribution. Tropical northwestern Pacific: presently known only from the Ryukyu Archipelago, Japan; possibly also in the Bohol Sea, the Philippines (see above).

Habitat. The holotype was extracted from a crevice in large coral rock broken apart with a hammer. No association with other invertebrates was noted in the field (N. Shirakawa and R. Minemizu, pers. comm.). The nontype specimen was collected by brushing coral rubble lifted from about 3 m, on a reef platform.

Remarks. In spite of its morphological distinctiveness, S. pinguis sp. nov. is clearly a species of Salmoneus , as indicated by the possession of an appendix masculine in ovigerous specimens, the presence of a median notch on the posterior margin of the telson, the major chela with a deep proximal constriction on the palm and with serrate finger cutting edges, all features typical to Salmoneus ( Anker & Marin 2006; Anker et al. 2006). Salmoneus pinguis sp. nov. is presently the only species in the genus combining the carapace strongly domed or swollen dorsally ( Fig. 1 View FIGURE 1 ); the frontal margin of the carapace broadly triangular, with a rounded rostrum and no trace of orbital teeth ( Fig. 2 View FIGURE 2 C); the second abdominal pleuron conspicuously enlarged ( Fig. 1 View FIGURE 1 , 2 View FIGURE 2 A); the fourth pleuron greatly overlapping the fifth pleuron ( Fig. 1 View FIGURE 1 ); the antennular and antennal flagella densely covered with long setae ( Fig. 2 View FIGURE 2 A); the major cheliped with distally blunt, slightly bulbous fingertips ( Fig. 4 View FIGURE 4 D, E); and the uropodal exopod without a distinct diaeresis ( Fig. 3 View FIGURE 3 M). The orbital teeth are absent or greatly reduced in two other species of Salmoneus : S. brucei Komai, 2009 and S. degravei Anker, 2010 ; however, both differ from S. pinguis sp. nov. by numerous other morphological characters and ecology ( Komai 2009; Anker 2010), and are not closely related to the new species. The carapace of S. babai Miyake & Miya, 1966 is somewhat domed, but this species has sharp orbital teeth and additionally differs from S. pinguis sp. nov. by the shape of the major cheliped and the much stouter dactylus on the third to fifth pereopods ( Miyake & Miya 1966).

The great number of autapomorphic characters of S. pinguis sp. nov. obscures its affinities and makes it difficult to place in one of the previously established species groups of Salmoneus ( Anker & Marin 2006) . As pointed out by Anker (2011a), with the rapidly increasing number of species and new character combinations, some of these species groups are becoming of rather limited usage. The intra-generic structure of Salmoneus will need to be assessed with a comprehensive phylogenetic analysis based on both morphological and molecular data. However, such an analysis would only make sense after redescription of some poorly described species (e.g., S. latirostris ( Coutière, 1897) and S. tafaongae Banner & Banner, 1966 ) and description of at least 10 new taxa worldwide (A. Anker, pers. obs.).