Swireapseudes planafrontis, 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

Swireapseudes planafrontis sp. nov.

Figs 11 , 12 , 13 , 14 , 15

Type material.

Holotype: MBM287312, non-ovigerous female, 6.8 mm; Jiaozhou Bay, Qingdao, Shandong Province, China, 20 November 2003, from mud-sandy substrate with shell fragments at depth of 10 m, 36°09'N, 120°19'E. Allotype: MBM287302, male, 5.0 mm, completely dissected and body parts preserved in 75% alcohol; Jiaozhou Bay, Qingdao, Shandong Province, China, 15 March 2021, from muddy substrate with shell fragments at depth of 6 m, 36°06'N, 120°17'E. Paratypes: MBM287301, one ovigerous female, 6.9 mm, completely dissected and body parts preserved in 75% alcohol; Jiaozhou Bay, Qingdao, Shandong Province, China, 12 November 2020, from muddy substrate at depth of 6 m, 36°05'N, 120°10'E. MBM287303, one non-ovigerous female, 6.8 mm, partially dissected and body parts preserved in 75% alcohol; same collection data as allotype. MBM287304, one non-ovigerous female, 6.8 mm, partially dissected, and body parts preserved in 75% alcohol; same collection data as allotype. MBM287305, one non-ovigerous female, 7.1 mm, partially dissected and body parts preserved in 75% alcohol; Jiaozhou Bay, Qingdao, Shandong Province, China, 11 November 2020, from muddy substrate with shell fragments at depth of 4 m, 36°06'N, 120°17'E. MBM287306, one male, 5.2 mm, partially dissected and body parts preserved in 75% alcohol; same collection data as allotype. MBM287307, one male, 4.2 mm, partially dissected and body parts preserved in 75% alcohol; same collection data as allotype. MBM287308, one male, 4.2 mm; same collection data as allotype. MBM287309, one non-ovigerous female, 5.0 mm; Jiaozhou Bay, Qingdao, Shandong Province, China, 3 February 2021, from muddy substrate at depth of 14 m, 36°06'N, 120°15'E. MBM287310, one ovigerous female, 6.0 mm; same collection data as paratype MBM287305. MBM287311, one non-ovigerous female, 7.8 mm; same collection data as allotype.

Other material.

MBM147029, two females, Jiaozhou Bay, Qingdao , Shandong Province, China, 2 August 1964, from muddy substrate at depth of 7 m, 36°08'N, 120°15'E .

Type locality.

Jiaozhou Bay, Qingdao, Shandong Province, China.

Etymology.

The name is derived from the Latin planula (flat) and frontis (forehead), referring to the wide and flat rostrum.

Diagnosis.

Ovigerous female. Rostrum rounded, with wide and flat distal margin. Antennule article 1 inner margin with one strong spiniform seta midway. Antenna article 2 with one inner distal spiniform seta. Labium palp without inner distal expansion. Cheliped slightly dimorphic; left cheliped more setose; right cheliped more slender, exopod article 3 small and naked. Pereopod 1 merus with one short and strong ventrodistal spiniform seta; carpus with two short and strong ventral spiniform setae; dactylus with six pointed ventral denticles and one small ventrodistal spiniform seta, together with unguis subchela-like. Pereopods 2, 3, 5, and 6 with chela-like dactylus. Pereopod 4 dactylus with particularly long ventrodistal prolongation,> 2 × as long as unguis. Male. Similar to female except: Antennule outer flagellum proximal articles short and wide, covered with numerous aesthetascs. Antenna article 2 without inner distal spiniform seta, flagellum inner half covered with numerous aesthetascs, proximal articles very wide and short, distal articles narrower. Cheliped relatively robust; left and right cheliped dimorphic or not; fixed finger incisive margin with or without one large and blunt apophysis.

Description.

Female (ovigerous paratype MBM287301). Body (Fig. 11A , figure and description based on non-ovigerous female paratype MBM287303) elongate, dorsoventrally flattened, 6.8 mm long, 6.6 × as long as broad, posteriorly narrower. Carapace subrectangular, ~ 0.1 × as long as total body length, 0.9 × as long as broad, rostrum wide and rounded, anterior margin flat, with four short simple setae, lateral margin with several simple setae. Eye lobe well separated, pigmented. Pereon ~ 0.6 × as long as total body length; pereonite 1 broadest, 0.6 × as long as broad; pereonite 2 shortest, 0.9 × as long as pereonite 1, 0.6 × as long as broad; pereonite 3 1.3 × as long as pereonite 2, 0.8 × as long as broad; pereonite 4 longest, 1.4 × as long as pereonite 3, ca. as long as broad; pereonite 5 0.8 × as long as pereonite 4, ca. as long as broad; pereonite 6 0.9 × as long as pereonite 5, 0.9 × as long as broad, each pereonite with a few anterolateral simple setae. Pleon ~ 0.25 × body length, posteriorly narrower; each pleonite rectangular and similar in length, with several lateral plumose setae. Pleotelson subrectangular, 1.4 × as long as one pleonite, narrower than pleonite 5, 1.2 × as long as broad, with four lateral plumose setae, posterior margin rounded, with two pairs of simple setae.

Antennule (Fig. 11B , figure and description based on non-ovigerous female paratype MBM287304, 6.8 mm long) peduncle article 1 2.8 × as long as broad, outer margin with three broom and 12 simple setae, inner margin with nine simple setae and one strong spiniform seta midway; article 2 half as long as article 1, twice as long as broad, with 11 outer setae and six inner simple setae; article 3 short, half as long as article 2, 1.2 × as long as broad, with seven outer and six inner simple setae; article 4 naked; outer flagellum 16-articled, longer than peduncle, each article naked or with at most five distal simple setae; inner flagellum 13-articled, slightly shorter than outer flagellum, each article with two to five distal simple setae.

Antenna (Fig. 11C ) peduncle article 1 not examined; article 2 proximal half not examined, distal margin with one short outer simple seta and one inner spiniform seta, squama elongate, with five outer, five inner, and two distal simple setae; article 3 short and naked; articles 4 and 5 not well separated, naked; flagellum 14-articled, each article with 1-8 setae.

Labrum (Fig. 11D ) rounded, distal margin slightly concave, covered with setules; epistomal apophysis present.

Left mandible (Fig. 11E ) outer margin denticulate and covered with setules; incisor and lacinia mobilis (Fig. 11F ) four-denticled, setal row with one simple and five trifurcate or multifurcate setae; molar (Fig. 11G ) crenulate; palp 3-articled, article 1 short, 0.9 × as long as broad, with nine simple setae along distal and inner margin, article 2 2.5 × as long as article 1, with one simple seta on inner margin, article 3 ca. as long as article 2, with five distal simple setae. Right mandible (Fig. 12A ) outer margin covered with setules; incisor (Fig. 12B ) five-denticled, without lacinia mobilis, setal row similar to that of left mandible; molar not examined; palp similar to that of left mandible but article 2 with two inner simple setae, and article 3 with three distal simple setae.

Labium (Fig. 12C ) palp covered with setules, with two distal simple setae.

Maxillule (Fig. 12D ) outer endite with ten distal spiniform setae and two subdistal setae, inner and outer margins covered with setules; inner endite with one distal trifurcate seta and four distal plumose setae, inner and outer margin covered with setules; palp 2-articled, article 2 with five distal simple setae.

Maxilla (Fig. 12E ) outer lobe of movable endite with eight long distal simple setae; inner lobe of movable endite with ~ 12 distal simple setae; outer lobe of fixed endite distal margin with seven blunt, one leaf-like, four trifurcate, two simple setae, and one seta with several spinules on single side; inner lobe of fixed endite distal margin with a row of ~ 25 “articulate” setae (with distinct demarcation on midway of each seta), a cluster of seven simple setae, and four blunt setae with a row of short setules and serrations on distal one third; inner margin with spinules.

Maxilliped (Fig. 12F ) basis outer margin covered with setules covered with setules, distal margin with one seta; endite covered with setules, distal margin with five simple setae and six spiniform setae, inner margin with three coupling hooks, inner fold with six plumose setae; palp article 1 outer margin with one distal simple seta, distal margin with three simple setae, article 2 outer margin with seven long distal simple setae, inner margin with five long simple setae and a row of 45-50 shorter simple setae, article 3 outer margin with one distal simple seta, inner margin with ~ 12 simple setae, article 4 with ~ 12 distal simple setae.

Chelipeds (Fig. 13A, B ) left and right slightly dimorphic, differences in size and setal pattern. Left cheliped (Fig. 13A ) exopod 3-articled, article 3 with four plumose setae; basis 3 × as long as broad, dorsal margin with two simple setae on distal half, ventral margin with five long simple setae and four shorter simple setae; merus 0.7 × as long as basis, 2.3 × as long as broad, covered with totally ~ 25 simple setae; carpus long, ~ 1.9 × as long as merus, 4.6 × as long as broad, covered with totally ~ 44 simple setae; propodus palm 0.5 × as long as carpus, 2.4 × as long as broad, with three dorsal simple setae, one outer simple seta near insertion of dactylus, and two inner simple setae, fixed finger 0.8 × as long as palm, ~ 4 × as long as broad, with six ventral and two short distal simple setae; dactylus plus unguis 6.5 × as long as broad, slightly curved. Right cheliped (Fig. 13B ) slenderer and less setose than left cheliped, ~ 0.7 × as long as left cheliped; exopod 3-articled, article 3 small and naked; basis ~ 3 × as long as broad, ventral margin with one subdistal simple seta; merus 0.7 × as long as basis, ~ 3 × as long as broad, with two outer and two ventral setae; carpus long and slender, 1.9 × as long as merus, ~ 5 × as long as broad, with one outer subdistal simple seta, dorsal margin with one subdistal simple seta, ventral margin with three midway and one subdistal simple seta; propodus palm 0.4 × as long as carpus, 2.1 × as long as broad, with one outer simple seta near insertion of dactylus, dorsal margin with one subdistal simple seta, fixed finger 0.7 × as long as palm, 3 × as long as broad, with two ventral and two distal simple setae, incisive margin with one proximal simple seta; dactylus plus unguis 4.9 × as long as broad, slightly curved, with seven subdistal simple setae.

Pereopod 1 (Fig. 13C ) exopod 3-articled, article 3 with six plumose setae; basis 2.7 × as long as broad, dorsal margin with three short, two longer simple setae and a few setules, ventral margin with six simple setae midway and a cluster of eight distal simple setae; ischium with four ventrodistal simple setae; merus 0.6 × as long as basis, 1.4 × as long as broad, dorsal margin with a cluster of seven distal simple setae and one spiniform seta, ventral margin with a cluster of four simple setae midway, eight simple setae along distal half, three distal simple setae, and one distal short but strong spiniform seta; carpus 0.9 × as long as merus, 1.3 × as long as broad, distal margin with one long dorsal spiniform seta, a cluster of ca. eight dorsal simple setae and two outer setae, ventral margin with nine simple setae and two short but strong spiniform setae; propodus 1.2 × as long as carpus, 1.6 × as long as broad, dorsal margin with three shorter simple setae on proximal half, six long simple setae and three long spiniform setae on distal half, ventral margin with 11 simple setae and four strong spiniform setae, distal margin with one short subventral simple seta; dactylus (Fig. 13D ) plus unguis 0.7 × as long as propodus, 5.7 × as long as broad, ventral margin with six pointed denticles and one small distal spiniform seta, spiniform seta much shorter than unguis, together subchela-like.

Pereopod 2 (Fig. 13E ) basis 3.5 × as long as broad, with two short dorsal simple setae, one dorsal broom seta, three subventral distal simple setae, and a cluster of five ventrodistal simple setae; ischium with one dorsal simple seta and a cluster of six ventrodistal simple setae; merus 0.4 × as long as basis, 1.7 × as long as broad, with one outer subdistal and three outer distal simple setae, ventral margin with seven simple setae and one long spiniform seta on distal half; carpus 1.2 × as long as merus, 2.2 × as long as broad, outer surface with a row of ten simple setae and two long spiniform setae from midway to dorsodistal corner, ventral margin with eight simple setae and two long spiniform setae on distal half, distal margin with three inner simple setae; propodus 0.9 × as long as carpus, ~ 3 × as long as broad, distal half with a row of five subdorsal simple setae and three spiniform setae, ventral margin with seven simple setae and three spiniform setae; dactylus (Fig. 13F ) plus unguis 0.8 × as long as propodus, ~ 6 × as long as broad, dactylus slightly curved, with one indistinct demarcation midway and one pointed ventrodistal prolongation, unguis curved, slightly longer than prolongation, together chela-like.

Pereopod 3 (Fig. 13G ) basis 3.2 × as long as broad, with a cluster of six ventrodistal simple setae; ischium with a cluster of seven ventral subdistal simple setae; merus 0.3 × as long as basis, 1.8 × as long as broad, with eight ventral or subventral simple setae and one ventral spiniform seta on distal half, ventral margin slightly denticulate; carpus 1.4 × as long as merus, 2.6 × as long as broad, ventral to distal margin and subventral surface covered with ~ 16 simple setae and three spiniform setae, ventral margin slightly denticulate; propodus 0.7 × as long as carpus, 2.7 × as long as broad, with one dorsoproximal broom seta and a row of six simple setae and three spiniform setae from outer midway surface to dorsodistal corner, ventral margin with four simple setae and three spiniform setae on distal half; dactylus (Fig. 13H ) attached to propodus subdistally, similar to that of pereopod 2 but not articled.

Pereopod 4 (Fig. 14A , figure and description based on non-ovigerous female paratype MBM287305, 7.1 mm long) basis 3.2 × as long as broad, with a cluster of five ventrodistal simple setae; ischium with a cluster of six ventrodistal simple setae; merus 0.3 × as long as basis, 1.6 × as long as broad, with one dorsodistal, two outer subdistal, and three ventral simple setae, ventral margin slightly denticulate; carpus 1.8 × as long as merus, 2.5 × as long as broad, ventral to distal margin covered with ~ 17 simple setae and six spiniform setae, ventral margin slightly denticulate; propodus 0.6 × as long as carpus, 3.2 × as long as broad, ventral margin with ca. eight simple setae and 10 spiniform setae; dactylus (Fig. 13B , figure and description based on MBM287305) attached to propodus subdistally, nearly as long as propodus,> 9 × as long as broad, with three ventral spinules and one long ventrodistal prolongation that is 2.3 × as long as unguis, together subchela-like.

Pereopod 5 (Fig. 14C ) basis 3.2 ×as long as broad, dorsal margin with two broom setae midway, ventral margin with a cluster of five distal simple setae; ischium dorsal margin with one short subdistal simple seta, ventral margin with a cluster of five distal simple setae, merus 0.3 × as long as basis, 1.8 × as long as broad, with one dorsodistal simple seta, ventral margin denticulate, six simple setae on distal half; carpus 1.7 × as long as merus, ~ 3 × as as long as broad, ventral to distal margin covered with ~ 17 simple setae and eight spiniform setae, the distal two spiniform setae very long, ventral margin denticulate; propodus 0.8 × as long as carpus, 3.2 × as long as broad, ventral margin denticulate, covered with ca. ten simple setae and nine spiniform setae; dactylus similar to that of pereopod 3.

Pereopod 6 (Fig. 14D ) basis long, 4.8 × as long as broad, dorsal margin with one subproximal broom seta, ventral margin with two subdistal simple setae; ischium with two dorsal and three ventral subdistal simple setae; merus 0.3 × as long as basis, nearly 2 × as long as broad, with one dorsodistal simple seta and one simple seta on inner surface, ventral margin with six simple setae on distal half; carpus 1.7 × as long as merus, 3.3 × as long as broad, with three dorsodistal simple setae, ventral to distal margin with ~ 17 simple setae and five long spiniform setae, ventral margin slightly denticulate; propodus 0.8 × as long as carpus, 3.6 × as long as broad, with one dorsodistal, one ventrodistal simple seta, two long and one shorter dorsodistal spiniform setae, ventral margin with one proximal simple seta and a row of ~ 28 serrate setae along ventral margin to distal margin; dactylus similar to that of pereopod 5.

Pleopod 1 (Fig. 14E , all setae plumose, setules omitted in figure) basal article with seven outer and five inner plumose setae; exopod with 30 plumose setae; endopod with 27 plumose setae, most proximal one on inner margin strong.

Uropod basal article with four or five distal and subdistal simple setae; exopod and endopod not examined.

Male (allotype MBM287302). Body (Fig. 11H ) elongate, dorsoventrally flattened, allotype 5.0 mm long, 6.4 × as long as broad. Carapace subrectangular, ~ 0.1 × as long as total body length, 0.8 × as long as broad; rostrum rounded, anterior margin flat, with two short simple setae; lateral margin with one simple seta. Pereon half as long as total body length; each pereonite with at most seven anterolateral simple setae and without or with one posterolateral simple seta, pereonite 1 broadest, as wide as carapace, half as long as broad, pereonite 2 shortest, pereonite 4 longest but narrowest. Pleon 0.3 × as long as total body length, posteriorly narrower; each pleonite similar in length, with several lateral plumose setae, pleonites 1-4 trapezoidal, pleonite 5 subrectangular. Pleotelson subrectangular, 1.3 × as long as pleonite 5, 1.5 × as long as broad, with three lateral plumose setae, posterior margin with two pairs of blunt apophyses.

Antennule (Fig. 15A , most aesthetascs represented by fine lines) peduncle article 1 ~ 3 × as long as broad, outer margin with 11 simple setae, inner margin with seven simple setae and one strong spiniform seta midway; article 2 ~ 0.5 × as long as article 1, 1.6 × as long as broad, with one ventral simple seta, outer margin with six simple setae, inner margin with one simple seta on proximal half and a cluster of three subdistal simple setae; article 3 short, 0.4 × as long as article 2, 0.7 × as long as broad, distal margin with three outer and two inner simple setae; article 4 with one inner simple seta; outer flagellum 21-articled, ca. as long as peduncle, proximal articles shorter and broader, covered with numerous aesthetascs, distal articles longer and slenderer, each article without or with at most four distal simple setae; inner flagellum 12-articled, slightly longer than outer flagellum, articles 5 and 7 with one distal broom seta, each article without or with at most four distal simple setae.

Antenna (Fig. 15B , most aesthetascs represented by fine lines) peduncle article 1 naked; article 2 with two short outer simple setae, squama elongate, with three outer, three inner, two longer and one short distal simple seta; article 3 very short, naked; article 4 longest, 0.8 × as long as broad, with three short outer simple setae; article 5 similar to flagellum articles, covered with aesthetascs, with one outer distal simple seta; flagellum 20-articled, each article very short, proximal articles broader, outer half covered with numerous aesthetascs, each article without or with at most four distal simple setae.

Left cheliped (Fig. 15C , figure and description based on male paratype MBM287307, 4.2 mm long) basis proximal part missing, dorsal margin with one short subdistal simple seta, ventral margin with one short and two longer simple setae; merus 2.2 × as long as broad, outer surface with one subdistal simple seta, inner surface with two dorsodistal simple setae, ventral margin with four subdistal simple setae; carpus 2.1 × as long as merus, 3.5 × as long as broad, with seven ventral simple setae, inner surface with ca. ten subdorsal simple setae; propodus palm and fixed finger combined ~ 0.8 × as long as carpus, palm 1.8 × as long as broad, with one long outer simple seta near insertion of dactylus, dorsal margin with one subproximal and three subdistal simple setae, inner surface with two long subdistal simple setae, fixed finger 2.7 × as long as broad, with six ventral, one outer and one inner simple seta, incisive margin with one large and blunt apophysis, and six distal simple setae; dactylus curved, 4.7 × as long as broad. Right cheliped (Fig. 15D ) exopod 3-articled, article 3 with four plumose setae; basis 2.3 × as long as broad, ventral margin with one longer and three short but strong simple setae on proximal half, and one longer simple seta on distal half; merus 0.6 × as long as basis, 2.4 × as long as broad, ventral margin with four simple setae on proximal half, four longer and one short but strong simple setae on distal half, distal margin with two outer and three inner simple setae; carpus 1.7 × as long as merus, 3.4 × as long as broad, with one inner subventral simple setae, ventral margin with five simple setae and three subdistal simple setae; propodus attached to carpus subdistally, palm half as long as carpus, almost 2 × as long as broad, with one outer simple seta near insertion of dactylus, dorsal margin with one proximal simple seta, a cluster of three simple setae on proximal half, one midway and a row of five subdistal simple setae, fixed finger distal part missing, with six ventral and three distal simple setae, incisive margin crenulate; dactylus plus unguis as long as palm, with three outer simple setae, unguis long and slender.

Remarks.

The specimens of Swireapseudes planafrontis sp. nov. are extremely fragile, with appendages frequently missing. This phenomenon was also found in species of some other parapseudid genera, e.g., Parapseudes , Pakistanapseudes and Saltipedis , and considered to be autotomy ( Guţu 1996). As a result, the morphological description of S. planafrontis could only be made up by the sum of parts of the several paratypes and allotype. It may be a novel discovery that the chelipeds of the present species not only display sexual dimorphism but also exhibit a little dimorphism between left and right chelipeds of a single female individual. Unfortunately, no male specimens were collected with complete left and right chelipeds, so it is not possible to confirm that the morphological differences between right cheliped of the allotype and left cheliped of the male paratype MBM287307 are the results of dimorphism or simply the result of variation (Figs 13A, B , 15C, D ).

Apart from the dimorphism of female left and right cheliped, there are several other unique morphological features that easily distinguish Swireapseudes planafrontis sp. nov. from the two previously recorded species, S. birdi and S. toloensis : 1) rostrum distally wide and flat; 2) the presence of one strong spiniform seta midway on the inner margin of the antennule peduncle article 1; 3) the presence of one inner distal spiniform seta on the female antenna article 2; 4) the presence of one small ventrodistal spiniform seta (rather than prolongation) on pereopod 1 dactylus; 5) the long ventrodistal prolongation on pereopod 4 dactylus (Figs 11A-C, H , 13C, D , 14A, B , 15A , Table 3 ; see also Guţu and Iliffe 2008: figs 1A-D, 2D, 3C, 4A; Bamber 1997: figs 7A, B, 8A, B, 9H).

Figures

Figure 11. Swireapseudes planafrontis sp. nov. Paratype (MBM 287303), non-ovigerous female A body dorsal view. Paratype (MBM 287304), non-ovigerous female B left antennule. Paratype (MBM 287301), ovigerous female C right antenna D epistome and labrum E left mandible F left mandible incisor, lacinia mobilis and setal row G left mandible molar. Allotype (MBM 287302), male H body dorsal view. Scale bars: 2 mm (A, H); 0.2 mm (B, C, E); 0.1 mm (D, F, G).

Figure 12. Swireapseudes planafrontis sp. nov. Paratype (MBM 287301), ovigerous female A right mandible B right mandible incisor C labium D maxillule E maxilla F maxilliped. Scale bars: 0.2 mm (A, D); 0.1 mm (B, C, E, F).

Figure 13. Swireapseudes planafrontis sp. nov. Paratype (MBM 287301), ovigerous female A left cheliped B right cheliped C right pereopod 1 D right pereopod 1 dactylus E right pereopod 2 F right pereopod 2 dactylus G right pereopod 3 H right pereopod 3 dactylus. Scale bars: 0.2 mm (A-C, E, G).

Figure 14. Swireapseudes planafrontis sp. nov. Paratype (MBM 287305), non-ovigerous female A right pereopod 4 B right pereopod 4 dactylus. Paratype (MBM 287301), ovigerous female C right pereopod 5 D right pereopod 6 E right pleopod 1 (all setules omitted). Scale bars: 0.2 mm (A, C-E).

Figure 15. Swireapseudes planafrontis sp. nov. Allotype (MBM 287302), male A left antennule B left antenna D right cheliped. Paratype (MBM 287307), male C left cheliped. Scale bars: 0.2 mm.