Apseudes spinidigitus, Tzeng & Ma & Li, 2022

Tzeng, You-Wei, Ma, Lin & Li, Xinzheng, 2022, Three new species of Apseudomorpha (Crustacea, Tanaidacea) from Jiaozhou Bay, the Yellow Sea, and the South China Sea off coasts of China, ZooKeys 1096, pp. 119-160 : 119

Apseudes spinidigitus sp. nov.

Figs 2 , 3 , 4 , 5

Type material.

Holotype: MBM287293, non-ovigerous simultaneous Simultaneous hermaphrodite , 8.3 mm; the South China Sea off Guangdong Province, China, 21 October 1959, from mud-sandy substrate at a depth of 43 m, 21°15'N, 113°00'E. Paratypes: MBM032095, one non-ovigerous simultaneous Simultaneous hermaphrodite , 8.5 mm, completely dissected and body parts preserved in 75% alcohol; the South China Sea off Guangdong Province, China, 10 January 1960, from muddy substrate at a depth of 55 m, 21°30'N, 114°00'E. MBM032282, four non-ovigerous simultaneous hermaphrodites; same collection data as holotype.

Type locality.

Northern South China Sea.

Etymology.

The name is derived from the Latin spinosus (spinous) and digitus (finger), referring to the dactylus and fixed finger of cheliped both equipped with one conspicuous apophysis on the incisive margins.

Diagnosis.

Non-ovigerous simultaneous Simultaneous hermaphrodite . Rostrum cordiform, distally pointed. Carapace lateral margin with one large spine-like anterior apophysis. Pereonites 3-6 with one curved spine-like anterolateral apophysis. Maxilliped endite inner margin with two coupling hooks. Cheliped fixed finger and dactylus incisive margin with one conspicuous apophysis, respectively. Pereopod 1 merus and carpus each with one dorsodistal and one ventrodistal spiniform seta; propodus with one dorsodistal and four ventral spiniform setae. Pleopod basal article with four inner plumose setae.

Description.

Simultaneous hermaphrodite (non-ovigerous paratype MBM032095). Body (Fig. 2A ) dorsoventrally flattened, 8.5 mm long, 5.8 × as long as broad, posteriorly narrower. Carapace subrectangular, ~ 0.2 × as long as total body length, 1.1 × as long as broad; rostrum cordiform, with proximal half laterally extended, distal half narrow, terminally pointed and slightly down-curved; lateral margin with one large spine-like anterior apophysis adjacent to eye lobe, with three outer and three inner plumose setae on apophysis. Eye lobe well separated, wide and short, without visual elements. Pereon ~ 0.5 × as long as total body length; pereonite 1 broadest, slightly broader than carapace, 0.5 × as long as broad; pereonite 2 0.7 × as long as pereonite 1, 0.5 × as long as broad, with ca. three anterolateral and five posterolateral plumose setae; pereonite 3 slightly longer than pereonite 2, 0.5 × as long as broad, anterolateral margin with one curved spine-like apophysis and three plumose setae, posterolateral margin with ca. seven plumose setae; pereonite 4 1.2 × as long as pereonite 3, 0.7 × as long as broad, anterolateral margin with one curved spine-like apophysis and three plumose setae, posterolateral corner pointed, with ca. seven plumose setae; pereonite 5 similar to pereonite 4 but with three posterolateral plumose setae; pereonite 6 0.9 × as long as pereonite 5, 0.7 × as long as broad, anterolateral margin with one curved spine-like apophysis and ca. three plumose setae, pereonites 1-5 each with one hyposphenia, pereonite 6 with genital cone. Pleon as long as carapace, posteriorly narrower, each pleonite with pointed epimera and ~ 12 lateral plumose setae. Pleotelson 0.9 × as long as carapace, 2.5 × as long as broad, lateral margin with> 20 plumose setae, terminally subtriangular, with ca. six posterior plumose setae.

Antennule (Fig. 2B ) peduncle article 1 3.2 × as long as broad, outer margin with ~ 17 circumplumose setae, two broom setae and one simple seta, inner margin with nine circumplumose setae; article 2 short, 0.3 × as long as article 1, 1.8 × as long as broad, with ca. seven circumplumose setae and three simple setae; article 3 0.6 × as long as article 2, 1.7 × as long as broad, with three circumplumose setae; article 4 naked, 0.5 × as long as article 3, ca. as long as broad; outer flagellum 13-articled, articles 3, 5, 7, 9, 11, and 13 with one distal aesthetasc and 1-4 distal simple setae, other articles with one distal simple seta or naked; inner flagellum 7-articled, articles 1-5 with one or two distal simple setae, articles 6 and 7 with four distal simple setae.

Antenna (Fig. 2C ) peduncle article 1 short and covered with setules, 0.9 × as long as broad, inner margin with conical apophysis; article 2 1.6 × as long as article 1, 1.7 × as long as broad, with two inner simple setae; squama slender, slightly longer than article 2, 3.8 × as long as broad, with 13 circumplumose setae; article 3 short, 0.4 × as long as article 2, 0.9 × as long as broad, with one inner distal simple seta; article 4 0.8 × as long as article 2, 2.4 × as long as broad, with one inner simple seta; article 5 0.8 × as long as article 2, 2.2 × as long as broad, outer margin with three circumplumose and one broom seta, inner margin with four long simple setae; flagellum 11-articled, article 1 with two long distal circumplumose setae, article 3 with two long distal circumplumose setae and five distal simple setae, article 6 with one distal aesthetasc and four distal simple setae, article 11 with eight distal simple setae, and other articles with 1-4 simple setae or naked.

Epistome (Fig. 2D ) with one strong and curved apical apophysis. Labrum (Fig. 2D ) rounded with some setules.

Left mandible (Fig. 2E ) outer margin denticulate; incisor with four or five denticles; lacinia mobilis large and subrectangular, distal margin with four denticles; setal row with four serrate setae and three simple setae; molar not examined; palp 3-articled, article 1 1.7 × as long as broad, inner margin with five simple setae, article 2 shorter than articles 1 and 3 combined, 3 × as long as broad, inner margin with 12 simple setae and one very long simple seta, article 3 1.2 × as long as article 1, 3 × as long as broad, inner margin with 15 simple setae and two very long simple setae. Right mandible similar to left mandible but without lacinia mobilis, setal row (Fig. 2F ) with one trifurcate, four bifurcate, one serrate, and one blunt seta.

Labium (Fig. 3A ) antero-outer corner near palp with one small apophysis; palp large and covered with setules, with three distal simple setae.

Maxillule (Fig. 3B ) covered with setules; inner endite with five distal plumose setae; outer endite with two subdistal simple setae and ten distal spiniform setae; palp 2-articled, article 2 with seven subdistal plumose setae.

Maxilla (Fig. 3C ) outer margin covered with setules; outer lobe of movable endite with two plumose setae and seven serrate setae; inner lobe of movable endite with a row of six blunt setae, a cluster of> 13 simple setae, and two serrate setae; outer lobe of fixed endite with one comb-like seta, two trifurcate setae, one bifurcate seta, two plumose setae, and> 16 simple setae, outer margin covered with setules; inner lobe of fixed endite with two long setae only serrate on distal 1/4, five serrate setae, and ~ 39 simple setae along distal margin.

Maxilliped (Fig. 3D, E ) basis covered with setules; endite (Fig. 3E ) inner margin with two coupling hooks, inner fold with 11 circumplumose setae, distal margin with two blunt, three bifurcate, and eight simple setae; palp 4-articled, article 1 with two short outer-distal circumplumose setae and two inner circumplumose setae, article 2 outer-distal, distal, and inner margin with> 37 simple and five circumplumose setae; article 3 inner margin with ~ 16 simple setae; article 4 distal margin with nine simple setae.

Epignath (Fig. 3F ) typical of genus, partially covered with setules, with one stout plumose seta.

Cheliped (Fig. 4A ) exopod 3-articled, article 3 with four plumose setae; basis 2.2 × as long as broad, ventral margin with one proximal plumose seta, one strong spiniform seta midway, and three distal plumose setae; merus 0.8 × as long as basis, 3 × as long as broad, ventral margin with two plumose setae midway, one very large subdistal spine-like apophysis, eight subdistal and one distal plumose seta; carpus elongate, 1.2 × as long as basis, 2.8 × as long as broad, with one dorsodistal spine-like apophysis, one dorsodistal plumose seta, and six plumose setae along ventral margin; propodus palm 1.4 × as long as broad, with one dorsoproximal plumose seta, two dorsodistal plumose setae, one plumose setae near dactylus articulation, and eight plumose setae along ventral margin of palm and fixed finger; fixed finger (Fig. 4B ) nearly as long as palm, ~ 2.1 × as long as broad, incisive margin with one large apophysis and ten simple setae on distal half; dactylus (Fig. 4B ) plus unguis 4.3 × as long as broad, slightly curved, incisive margin with one conspicuous apophysis.

Pereopod 1 (Fig. 4C, D ) coxa (Fig. 2A ) with large and pointed spine-like apophysis and five plumose setae; exopod 2-articled, article 2 with five plumose setae; basis ~ 2.4 × as long as broad, with one subdorsal proximal apophysis near exopod, ventral margin with one subproximal apophysis, two subdistal simple setae, four distal simple setae and one distal spiniform seta; ischium with one short dorsodistal simple seta and four short ventrodistal simple setae; merus 2.2 × as long as broad, with one dorsodistal spiniform seta and a row of ~ 11 lateral simple setae, ventral margin with a row of ~ 11 simple setae on distal half, one distal spiniform seta and two short distal simple setae; carpus short and thick, dorsally extended, 0.7 × as long as merus, 1.3 × as long as broad, dorsal margin with a row of ~ 12 long simple setae on distal half, one short and three longer distal simple seta, and one large distal spiniform seta, ventral margin with six simple setae midway and one large distal spiniform seta; propodus ca. as long as carpus, slightly thinner than carpus, dorsal margin with ~ 11 simple setae on distal half, and one large distal spiniform seta, ventral margin with six simple setae and four large spiniform setae; dactylus plus unguis 0.9 × as long as propodus, slightly curved, dorsal margin with one simple seta midway, ventral margin with one subdistal spinule.

Pereopod 2 (Fig. 4E ) coxa with one plumose seta; basis 4 × as long as broad, dorsal margin with two short simple setae on proximal half, ventral margin with one short and two longer simple setae on proximal half, three short and one longer simple seta on distal half, and a cluster of five distal simple setae; ischium with one dorsodistal and three ventrodistal simple setae; merus ~ 0.5 × as long as basis, 2.3 × as long as broad, with one subdorsal simple seta on proximal half, a row of six dorsodistal simple setae, one long and slender dorsodistal spiniform seta, ventral margin with eight simple setae along distal half, one long slender subdistal spiniform seta and one shorter subdistal spiniform seta; carpus 0.8 × as long as merus, 2 × as long as broad, dorsal margin with a row of ca. seven simple setae on proximal half, ca. six simple setae on distal half, and two distal simple setae, distal margin with a row of three lateral spiniform setae, ventral margin with eight simple setae, one long and slender spiniform seta, and two shorter spiniform setae; propodus slightly longer than carpus, 2.9 × as long as broad, with ~ 12 simple setae along distal half of dorsal margin, one long and slender dorsodistal spiniform seta, and one lateral spiniform seta, ventral margin with ~ 11 simple setae, one long and slender spiniform seta midway and one distal spiniform seta; dactylus plus unguis thin and curved, nearly as long as propodus, with one doral seta midway, unguis ~ 0.7 × as long as dactylus.

Pereopod 3 (Fig. 4F ) basis 3.7 × as long as broad, dorsal margin with one short simple seta on proximal half, ventral margin with one broom and one short simple seta on proximal half, one broom seta on distal half, and three simple distal setae; ischium with one dorsodistal and three ventrodistal simple setae; merus 0.4 × as long as basis, 2.2 × as long as broad, with one dorsodistal simple seta, one distolateral simple seta, and one distolateral spiniform seta, ventral margin with four simple setae on distal half, one small spiniform seta midway, and one long and slender distal spiniform seta; carpus slightly longer than merus, 2.1 × as long as broad, with three long simple setae on proximal half, a row of ca. seven simple setae on distal half of dorsal margin, and a row of six lateral spiniform setae, distal one longer, ventral margin with six simple setae and one spiniform seta along distal half; propodus slightly longer than carpus, 2.8 × as long as broad, with ~ 11 simple setae and two long and slender spiniform setae on distal half of dorsal margin, three longer and one very short lateral spiniform seta, ventral margin with 11 simple setae and one distal spiniform seta; dactylus plus unguis thin and curved, ~ 0.7 × as long as propodus, unguis 0.5 × as long as dactylus.

Pereopod 4 (Fig. 5A ) coxa with one plumose seta; basis 2.9 × as long as broad, dorsal margin with two short proximal simple setae and two broom setae midway, ventral margin with two longer and one short distal simple seta; ischium with one dorsodistal simple seta and one ventrodistal simple seta; merus ~ 0.4 × as long as basis, 2.3 × as long as broad, dorsal margin with one distal simple seta, ventral margin with three simple setae midway, four spiniform setae and two simple setae on distal half; carpus ~ 1.2 × as long as merus, 2.7 × as long as broad, with ~ 11 spiniform setae and> 17 simple setae along ventral to distal margin; propodus shorter and thinner than carpus, 0.8 × as long as carpus, 2.9 × as long as broad, with a comb-like row of numerous short and fine dorsodistal serrate setae and a cluster of numerous longer dorsodistal simple setae, ventral margin with ~ 11 longer simple setae and ca. seven short simple setae; dactylus plus unguis slender and slightly curved, 0.6 × as long as propodus, dorsal margin with one seta midway, unguis 0.5 × as long as dactylus.

Pereopod 5 (Fig. 5B ) basis dorsal margin with one broom seta on proximal half, ventral margin with one short midway and one longer distal simple seta; ischium with one dorsal and three ventrodistal simple setae; merus 2.4 × as long as broad, with one dorsodistal, one subventral, two ventrodistal simple setae, and three ventrodistal spiniform setae; carpus slightly longer and thinner than merus, 2.6 × as long as broad, with ca. ten spiniform setae and> 19 simple setae along ventral to distal margin; propodus slender, 0.8 × as long as carpus, 3.2 × as long as broad, dorsal margin with one broom seta midway and five strong distal simple setae, ventral margin with seven simple setae on proximal half, two distal simple setae, one strong spiniform seta midway, one distal spiniform seta, and a comb-like row of ~ 20 short and fine serrate setae between those two spiniform setae; dactylus plus unguis slender and slightly curved, 0.8 × as long as propodus, dorsal margin with one simple seta midway, unguis 0.6 × as long as dactylus.

Pereopod 6 (Fig. 5C ) coxa with three simple setae; basis 4 × as long as broad, with one lateral and one subdorsal circumplumose seta on proximal half, dorsal margin with 11 circumplumose setae along distal half, ventral margin with one small spiniform seta midway and 12 circumplumose setae; ischium with three ventrodistal circumplumose setae; merus 0.6 × as long as basis, 3.1 × as long as broad, dorsal margin with one shorter and two very long circumplumose setae on proximal half, three very long circumplumose setae on distal half, ventral margin with two circumplumose setae on proximal half, one small spiniform seta midway, five circumplumose setae and three small spiniform setae on distal half; carpus slightly shorter than merus, 2.9 × as long as broad, dorsal margin with two midway and one distal very long circumplumose seta, ventral to distal margin with ~ 13 circumplumose setae and one distal spiniform seta; propodus 0.8 × as long as carpus, 2.9 × as long as broad, with two ventroproximal circumplumose setae, a comb-like row of numerous serrate setae along ventral to distal margin, one dorsodistal and two ventrodistal circumplumose setae; dactylus plus unguis slender and slightly curved, 0.9 × as long as propodus, dorsal margin with one short simple seta midway, unguis 0.6 × as long as dactylus.

Pleopods (Fig. 5D , all setae plumose, setules omitted in figure) basal article elongate, 2.7 × as long as broad, with four inner plumose setae; exopod slender, 3.6 × as long as broad, outer to distal margin with 33 plumose setae, inner margin with seven short simple setae; endopod longer and slender than exopod, 1.2 × as long as exopod, 5 × as long as broad, with 25 plumose setae and one stronger plumose seta on proximal half of inner margin.

Uropod (Fig. 5E ) basal article 1.6 × as long as broad, outer margin with one midway and three distal circumplumose setae, inner margin with two distal setae; exopod not examined; endopod 36-articled, articles 3, 8, 13, and 18 with 1-3 broom setae and 1-5 simple distal setae, other articles without seta or with at most six simple setae.

Variation.

Non-ovigerous simultaneous Simultaneous hermaphrodite holotype (MBM287293, 8.3 mm long) uropod with 8-articled exopod and 38-articled endopod.

Remarks.

According to Bamber (1998, 2008), only three species of the genus Apseudes have been recorded from South China Sea region previously: A. manna Bamber, 2008 (Hong Kong), A. nagae Shiino, 1963 (Vietnam, Sabah and Brunei), and A. nhatrangensis Shiino, 1963 (Vietnam). Among these three, A. manna is the geographically closest to Apseudes spinidigitus sp. nov.; the new species, however, is conspicuously distinguished from A. manna in morphology, by having the spine-like apophyses on carapace, pereonites, merus, carpus, and fingers of cheliped, and pointed epimera on each pleonite (Fig. 2A , 4A, B , Table 1 ; Bamber 2008: figs 1A, 2A).

Apseudes spinidigitus also closely resembles A. nhatrangensis in morphology. Among all known species of Apseudes , only A. nhatrangensis and the new species have the combination of features of a cordiform and distally pointed rostrum, one large spine-like anterior apophysis on lateral margin of carapace, a pair of wide but short eye lobes without visual elements, one large and curved spine-like anterolateral apophysis on pereonites 3-6, similar numbers of antennule and antenna flagella, uropod exopod and endopod articles, one large spine-like subdistal apophysis on ventral margin of cheliped merus, and one subproximal apophysis on ventral margin of pereopod 1 basis. Nevertheless, there are still several differences between these two species: 1) having two coupling hooks on maxilliped endite in A. spinidigitus , vs. four in A. nhatrangensis , 2) having a distinct spiniform seta midway on ventral margin of cheliped basis in A. spinidigitus , vs. a large apophysis in A. nhatrangensis , 3) the presence of one dorsodistal spine-like apophysis on cheliped carpus in A. spinidigitus , absence in A. nhatrangensis , 4) the presence of one conspicuous apophysis on incisive margin of cheliped dactylus in A. spinidigitus , vs. absence in A. nhatrangensis , 5) the presence of one ventrodistal spiniform seta on pereopod 1 merus and carpus each in A. spinidigitus , vs. absence in A. nhatrangensis , 6) having only one dorsodistal spiniform seta on pereopod 1 carpus and propodus each in A. spinidigitus , vs. two in A. nhatrangensis , 7) having only four plumose setae on inner margin of pleopods basal articles in A. spinidigitus , vs. more than four plumose setae on both sides of pleopods basal articles in A. nhatrangensis (Figs 2A-C , 3E , 4A-C , 5D, E , Table 1 ; Shiino 1963: figs 1A, C, D, 2A, H, I, 3A, B, D, E, G, H, 3H).

In addition to the features mentioned above, the presence of circumplumose setae on the antennule, antenna, maxilliped, pereopod 6 and uropod of A. spinidigitus is also a rare feature only found in a few species among Apseudes , i.e., A. fecunda ( Guţu, 2006), A. nagae , A. nhatrangensis , A. nipponicus Shiino, 1937, A. sculptus Pfeffer, 1888 ( Lang 1953), and A. spectabilis Studer, 1884 ( Shiino 1978).

Figures

Figure 2. Apseudes spinidigitus sp. nov. Paratype (MBM 032095), non-ovigerous simultaneous Simultaneous hermaphrodite A body dorsal view B right antennule C right antenna D epistome and labrum E left mandible F right mandible setal row. Scale bars: 1 mm (A); 0.2 mm (B, C, E); 0.1 mm (D, F).

Figure 3. Apseudes spinidigitus sp. nov. Paratype (MBM 032095), non-ovigerous simultaneous Simultaneous hermaphrodite A labium B maxillule C maxilla D maxilliped E maxilliped endite F epignath. Scale bars: 0.1 mm (A, D-F); 0.2 mm (B, C).

Figure 4. Apseudes spinidigitus sp. nov. Paratype (MBM 032095), non-ovigerous simultaneous Simultaneous hermaphrodite A left cheliped B left cheliped fixed finger and dactylus C right pereopod 1 D proximal end of left pereopod 1 basis E right pereopod 2 F left pereopod 3. Scale bars: 0.2 mm.

Figure 5. Apseudes spinidigitus sp. nov. Paratype (MBM 032095), non-ovigerous simultaneous Simultaneous hermaphrodite A left pereopod 4 B right pereopod 5 C left pereopod 6 D left pleopod 5 (all setules omitted) E left uropod. Scale bars: 0.2 mm.