Betaeus levifrons Vinogradov, 1950

Marin, Ivan, 2010, Redescription of the alpheid shrimp Betaeus levifrons Vinogradov, 1950 (Crustacea, Decapoda, Alpheidae) from Peter the Great Bay, Russian coast of the Sea of Japan, Zootaxa 2613, pp. 51-60 : 52-59

publication ID	https://doi.org/ 10.5281/zenodo.197833
DOI	https://doi.org/10.5281/zenodo.6198561
persistent identifier	https://treatment.plazi.org/id/EB412848-2258-9C2D-FF6E-FF6A5055FA43
treatment provided by	Plazi
scientific name	Betaeus levifrons Vinogradov, 1950
status

Treatment

Betaeus levifrons Vinogradov, 1950 View in CoL

( Fig. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 , 5 View FIGURE 5 a)

Betaeus levifrons Vinogradov 1950: 198 View in CoL , pl. 10, fig. 32 [type locality - Zolotoi Rog Bay, Vladivostok, Sea of Japan]

Material examined: 1 adult male (dissected, LEMMI) - Russian Far East, Sea of Japan, Peter the Great Bay, Vostok Bay, near scientific station “Vostok”, 42°51΄14.48ʺN 132°46΄47.24ʺE, shore in front of the laboratory, depth 1 m, sandy-gravel bottom overgrown with sea-grass -,, in burrow, coll. I. Marin, 25 Sept. 2009; 1 adult non-ovigerous female and 1 adult male ( NTOU M 00955 View Materials )—same locality as previous specimen, coll. I. Marin, 27 May 2010; 1 adult non-ovigerous female and 2 adult males ( LEMMI)—same locality as previous specimen, from burrows, together with specimens of mud shrimps Upogebia major and U. issaeffi , coll. I. Marin & O. Korn, 29 May 2010; 2 adult males ( MIMB) — same locality as previous specimen, coll. I. Marin & O. Korn, 0 2 June 2010.

Description. Medium-sized alpheid shrimp. Carapace ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 a, b) smooth; frontal margin without orbital teeth and rostrum, broadly rounded, exceeding anterolateral margin; pterygostomian angle rounded; cardiac notch deep.

Pleura of first to fifth abdominal somites rounded posteroventrally ( Fig. 1 View FIGURE 1 ); sixth somite with articulated, distally truncate posteroventral flap ( Fig. 2 View FIGURE 2 c). Telson ( Fig. 2 View FIGURE 2 d) about twice as long as wide, slightly widening in central part, narrowing posteriorly, with two pairs of spines situated close to lateral margin, anterior pair at about half-length of telson, posterior pair closer to midline, at about 0.7 telson length; posterior margin convex, furnished with numerous long setae and two pair of spines at each posterolateral angle, mesial spines twice longer than lateral spines.

Eyes completely concealed by orbital hood; anteromesial margin with acute process.

Antennule ( Fig. 2 View FIGURE 2 e, f) overreaching distal margin of scaphocerite; basal segment about twice as long as wide, with strong tooth at ventromesial carina; stylocerite slender, sharp distally, overreaching mid-length of intermediate segment; intermediate segment slender, about 2.5 times as long as wide, with straight lateral margin bearing long plumose setae; distal segment about same length as width, with long plumose setae along lateral margin; lateral flagellum with basal fused portion consisting of 15 segments; secondary aesthetascsbearing branch composed of four segments; mesial flagellum slender, about twice longer than lateral.

Antenna ( Fig. 2 View FIGURE 2 g) with basicerite ending in strong ventrolateral tooth; carpocerite robust, about four times as long as wide, overreaching distal margin of scaphocerite; flagellum well developed, longer than carapace length; scaphocerite wide, about 2.5 times as long as maximal width, with convex lateral margin, distolateral tooth strong, acute, distinctly overreaching blade.

Mandible ( Fig. 3 View FIGURE 3 a), with two-segmented palp; incisor process broad, with five blunt teeth; molar process with sharp distal ridges. Maxillule ( Fig. 3 View FIGURE 3 b) with bilobed palp, each lobe carrying long apical seta. Maxilla ( Fig. 3 View FIGURE 3 c) with simple, distally blunt palp furnished with long simple setae proximally and one stiff seta distally; distal endite bilobed. First maxilliped ( Fig. 3 View FIGURE 3 d) with large bilobed epipod; palp slender, furnished with long plumose setae along lateral margin; caridean lobe narrow. Second maxilliped ( Fig. 3 View FIGURE 3 e, f) typical for genus, with ear-shaped epipod. Third maxilliped ( Fig. 3 View FIGURE 3 g) with well-developed arthrobranch; exopod reaching to distal margin of antepenultimate segment, latter about five times as long as wide, with serrated distodorsal margin ( Fig. 3 View FIGURE 3 h); penultimate segment about three times as long as wide, with six transverse rows of serrulate setae along lateral surface; ultimate segment tapering distally, with numerous transverse rows of serrulate setae along lateral surface; distal margin with long stiff setae, without spines.

First pereiopods (chelipeds) equal in size, similar in shape, carried extended ( Fig. 1 View FIGURE 1 ), surface covered with minute sharp teeth ( Fig. 4 View FIGURE 4 a, b); ischium about 1.5 times as long as wide; merus about five times as long as wide, with smooth dorsal margin, ventral and ventrolateral margins covered with numerous minute tubercles; carpus about as long as wide, slightly flaring distally, with distal margin ventrally embracing carpo-propodal articulation; propodus ( Fig. 4 View FIGURE 4 c) subcylindrical, somewhat compressed laterally, about three times as long as wide, covered with minute tubercles; fingers somewhat compressed, about four times as long as wide, about 0.6 times length of propodus, covered with small tubercles dorsally and dorso-laterally; cutting margins with two triangular teeth proximally, otherwise straight; tips crossing, sharp.

Second pereiopod slender ( Fig. 4 View FIGURE 4 d); ischium subequal to merus, latter about 5.5 times as long as wide; carpus equal to merus, five-segmented, ratio of segments approximately 3: 1: 1: 1: 2; palm subcylindrical, equal to distal carpal segment, about 1.5 times as long as wide; fingers equal to palm, simple, with tufts of setae.

Third to fifth pereiopods ( Fig. 5 View FIGURE 5 e-g) similar in general shape, relatively robust with unarmed proximal segments. Third pereiopod ( Fig. 5 View FIGURE 5 e) with ischium about twice as long as wide, unarmed; merus about five times as long as wide, with slightly convex margins; distoventral surface with minute tubercles; ventrolateral surface with stout spine proximally; carpus about 0.3 times length of merus, about twice as long as wide, flaring distally, distodorsal margin overhanging carpo-propodal articulation, distoventral angle with two small spines; propodus about 5.5 times as long as wide, with seven spines along ventral surface and one pair of longer distoventral spines; dactylus relatively slender, about 2.5 times as long as wide, simple, somewhat curved distally, with tufts of setae. Fourth pereiopod ( Fig. 4 View FIGURE 4 f) generally similar to third, but more slender segments and with fewer spines on ventral surface of propodus. Fifth pereiopod ( Fig. 4 View FIGURE 4 g) significantly more slender than third and fourth; merus about five times as long as wide, with short spine ventroproximally; carpus about four times as long as wide, flaring distally, distoventral angle unarmed; propodus with three spines along ventral surface and one pair of distoventral spines; cleaning brush well developed, consisting of at least 10 transverse rows of stiff setae; dactylus slender, about four times as long as wide, curved distally.

Uropods distinctly exceeding telson ( Fig. 2 View FIGURE 2 c); protopod with two subacute teeth, lateral tooth slightly larger than mesial, distal margin between these teeth concave, furnished with eight long simple setae; exopod with long stout distolateral spine; diaeresis with 12 blunt subtriangular teeth ( Fig. 2 View FIGURE 2 h).

Gill formula typical for genus: 5 pleurobranchs (P1-5), 1 arthrobranch (Mxp3), 0 podobranchs, 5 mastigobranchs (Mxp3, P1-4), 5 setobranchs (P1-4).

Sexual dimorphism between males and female presents by larger size of chelipeds in adult males ( Fig. 1 View FIGURE 1 ). Coloration. Body, antennules, antennae and chelipeds uniform-brown; ambulatory pereiopods reddish; corneas golden brown ( Fig. 5 View FIGURE 5 a).

Measurements. The largest collected specimen (male, LEMMI) has cl. 8.1 mm; tl. 26.4 mm; the largest female (NTOU M 0 0 955) has cl. 8.0 mm; tl. 25.0 mm.

Remarks. Two other species of Betaeus , B. granulimanus Yokoya, 1927 (synonyms: B. yokoyai Kubo, 1936 and B. murayamai Yokoya, 1938 ) ( Miya 1972; Kim 1976) and B. gelasinifer Nomura & Komai, 2000 ( Nomura & Komai 2000; Yang et al. 2007) are known from the northeastern Pacific Ocean, including the Sea of Japan ( Fig. 6 View FIGURE 6 ).

Betaeus levifrons can be separated from B. gelasinifer by the rounded orbital hood (vs. centrally emarginated in B. gelasinifer ); the distinctly longer antennular segments; the presence of one stout distolateral spine on the uropodal exopod (vs. two slender spines in B. gelasinifer ); the more slender chelipeds, with elongate subcylindrical chela covered with numerous minute sharp teeth (vs. shorter, more rounded, compressed and smooth chelipeds in B. gelasinifer ); the much longer proximal carpal segment of the second pereiopod; and the simple, slender dactyli on the third to fifth pereiopods (vs. stout and biunguiculate in B. gelasinifer ) (cf. Nomura & Komai 2000).

Betaeus levifrons can be separated from B. granulimanus by the rounded orbital hood (vs. centrally emarginated in B. granulimanus ); and the absence of a strong mesioventral tooth on the first segment of the antennular peduncle (present in B. granulimanus , see Miya 1972); the more slender chelipeds covered with numerous minute sharp teeth (vs. shorter, more rounded, chelipeds covered with large tubercles in B. granulimanus ). Betaeus levifrons also clearly separates from any species of the genus by the sequence of DNA (A. Baeza, personal comm.)

Ecology. The specimens were collected with a bait suction pump (yabby pump) from burrows of Upogebia major (de Haan, 1841) ( Fig. 5 View FIGURE 5 b-3) and U. issaeffi (Balss, 1914) . Burrows of Upogebia spp . were particularly abundant between the rootstocks of Zostera marina Linnaeus, 1753 or Z. asiatica Miki, 1932 (Zosteraceae) overgrowing a sandy gravel bottom. All specimens were collected separately suggesting that the species is probably inhabits each burrow of the host by a single individual. Several other species of Betaeus are known to inhabit upogebiid or callianassid burrows along the Pacific coast of North America (e.g., Hart 1964) while two other species of the genus Betaeus known from the Sea of Japan, B. granulimanus Yokoya, 1927 and B. gelasinifer Nomura & Komai, 2000 , were found free-living occurring on sandy and muddy bottom under large stones and rocks ( Kubo, 1936; Kim, 1976; Yang et al, 2007; Nomura Komai, 2000). All collected female were non-ovigerous; the spawning time of the species in Peter the Great Bay is early spring, from early March to late April, when the water temperature remains cold, below 10-12ºC ( O. Korn, pers. comm.). The other burrowing decapod observed at the collection site of B. levifrons is the callianassid ghost-shrimp Callianasa petalura Stimpson, 1860 (following to Sakai 1987, 2004) ( Fig. 5 View FIGURE 5 b-1-2).

Distribution. Betaeus levifrons is presently known only from the Russian coast of the Sea of Japan, more precisely from two neighboring localities in Zolotoi Rog Bay and Vostok Bay, both are parts of large Peter the Great Bay bounded east by the Cape Gamov (42°33΄27.97ʺN, 131°13΄4.85ʺE) and west by the Cape Povorotnyy (42°40΄46.13ʺN, 133°2΄30.28ʺE) (see Fig. 6 View FIGURE 6 ).