Liljeborgia associata Marin 2020
- Dataset
- A new species of the genus Liljeborgia Spence Bate, 1862 (Crustacea: Amphipoda: Liljeborgiidae) associated with the burrows of the spoon worm Urechis unicinctus in the Sea of Japan
- Rank
- SPECIES
- Published in
- Marin, Ivan (2020): A new species of the genus Liljeborgia Spence Bate, 1862 (Crustacea: Amphipoda: Liljeborgiidae) associated with the burrows of the spoon worm Urechis unicinctus in the Sea of Japan. European Journal of Taxonomy 613: 1-19, DOI: 10.5852/ejt.2020.613
Classification
- kingdom
- Animalia
- phylum
- Arthropoda
- class
- Malacostraca
- order
- Amphipoda
- family
- Liljeborgiidae
- genus
- Liljeborgia
- species
- Liljeborgia associata
description
Description HEAD (Fig. 2 c). Rostrum turned downward, distally acute; eye large (Fig. 1), with well-developed ommatidia, eye brightly white in alive specimens (Fig. 1). ANTENNA 1 (Fig. 2 d). Article 3 stout, about 1.5 times as long as wide; article 2 about as long as wide, with dorsal projection produced into a rounded lobe; major flagellum with 15 – 17 articles; accessory flagellum with 10 – 11 articles. ANTENNA 2 (Fig. 2 e). Article 3 about as long as wide, unarmed; article 2 about 3 times as long as wide, with 4 small dorsal spines, with 1 long distodorsal and 2 long simple distoventral spines, with simple setae ventrally; article 1 about 4 – 4.5 times as long as wide, with small dorsal spines, with 1 distoventral long spine, unarmed ventrally; flagellum with 13 – 15 articles. LABRUM (Fig. 2 a). Upper lip with labrum broader than long and smaller than epistome, apical margin sinuous. EPISTOME (Fig. 2 b). With rounded lobes, protruding in lateral view, armed with small setae dorsally. MANDIBLE (Fig. 2 f). Lacinia mobilis large, anterior margin armed with 5 small strong teeth; palp consists of 3 long slender articles, similar in size, covered with long simple setae, article 1 almost equal to article 2, about 5 – 6 times as long as wide; article 2 about 5 – 6 times as long as wide; article 3 almost equal to articles 1 and 2, about 5 times as long as wide. MAXILLA 1 (Fig. 2 g). Outer plate with 8 large slender spines, ventrally denticulated; inner plate with a single long plumose seta; palp consists of 4 articles, article 1 shovel-shaped, with broad median part, about 1.5 – 2 times as long as wide, with 8 – 9 sharp robust spines along anterior margin, and simple small setae along dorsal margin. MAXILLA 2 (Fig. 2 h). Inner and outer plates distally rounded, robust, covered with numerous long simple setae along anterior and lateral margins. MAXILLIPED (Fig. 2 i). Palp consists of 4 articles: article 1 of palp unarmed, article 2 with a cluster of long setae distodorsally, small robust setae distally and long simple setae along the inner margin, outer margin unarmed; article 3 with a cluster of long simple setae along anterior border and distal part of inner margin, outer margin unarmed, article 4 (dactylus) slender, curved, about 0.8 times as long as article 3, unarmed; outer plate with 13 – 15 robust spines along medial border (distal spines are narrow and rather long); inner plate covered with small setae along anterior margin. GNATHOPOD 1 (Fig. 3 a). Coxa trapezoidal, with anterior medial setae only, posterior border weakly concave; basis slender, about 6 – 7 times as long as wide, with ventral projection in proximal part, with long simple setae; ischium about as long as wide, with long simple setae along distoventral border; merus about 1.5 times as long as wide, sharping distoventrally, with several groups of setae along ventral margin; carpus slender, with blunt distoventral process, reaching ⅓ of palm length, not reaching propodal group of strong spines, armed with several groups of setae; propodus about twice as long as wide both in male and females (Fig. 3 b), with convex ventral margin, armed with small simple setae along almost all its length, with a depression and 3 long simple setae in proximal part level with end of dactylus, dorsal margin straight and unarmed; dactylus with 5 – 7 triangular teeth. GNATHOPOD 2 (Fig. 3 c). Very similar to Gn 1 in shape and slightly larger in size; coxa triangulo-elliptic; basis slender, about 6 times as long as wide, with long simple setae; ischium about as long as wide, with long simple setae along distoventral border; merus about 1.5 times as long as wide, sharpening distoventrally, with several groups of setae along ventral margin; carpus slender, with blunt distoventral process, reaching ¼ of palm length, not quite reaching propodal group of strong spines, armed with several groups of setae; propodus about 2 times as long as wide in both male (Fig. 5 a) and females (Fig. 3 d), dorsal margin straight and unarmed, with convex ventral margin, armed with small simple setae along almost entire length, with a depression and 3 long simple setae in proximal part level with end of dactylus; dactylus with 10 – 11 triangular teeth. PEREIOPOD 3 (Fig. 4 a). Coxa elliptic and narrow; basis slender, about 8 – 9 times as long as wide, with straight margins, covered with long simple setae; ischium about as long as wide, with long simple setae along distoventral border; merus broad, about 3 times as long as wide, slightly longer than carpus and equal to propodus, dorsal margin produced forward, with long simple setae along dorsal and ventral margins; carpus about 3 times as long as wide, with straight margins, unarmed dorsally and with simple long setae along ventral margin; propodus about 4 – 4.5 times as long as wide, slightly curved, unarmed dorsally and ventrally, with several long simple setae at distodorsal angle; dactylus of normal length, slender, weakly curved, slightly shorter than propodus and equal to carpus in length. PEREIOPOD 4 (Fig. 4 b). Coxa wide, with parallel anterior and posterior border, ventral border with 3 wellmarked serrations; basis slender, about 7 – 7.5 times as long as wide, with straight margins, covered with long simple setae; ischium about as long as wide, with long simple setae along distoventral border; merus broad, about 3 times as long as wide, longer than carpus and slightly shorter than propodus, dorsal margin produced forward, with long simple setae along dorsal and ventral margins; carpus about 2.5 – 3 times as long as wide, with straight margins, unarmed dorsally and with long simple setae along ventral margin; propodus about 5 – 5.5 times as long as wide, slightly curved, unarmed dorsally, with several long simple setae at distodorsal angle, with 5 tiny spines along ventral margin; dactylus of normal length, slender, weakly curved, slightly shorter than propodus and slightly longer than carpus. PEREIOPOD 5 (Fig. 4 c). Coxa subquadrate, with medially concave ventral margin, unarmed; basis broad, with anterior and posterior border convex; anterior border with 12 – 13 small spines accompanied by small setae, posterior border with well-marked serration; ischium about as long as wide, with large simple spine on anterodistal corner; merus about 4 times as long as wide, with 4 short anterior spines, 1 large distodorsal spine paired with a spinule, and 1 simple distoventral spine; carpus about 4 times as long as wide, slightly shorter than merus, unarmed posteriorly, with 3 small anterior spines, and with a distal pair of spines anteriorly and posteriorly; propodus (Fig. 4 d) about 6 times as long as proximal width, slightly tapering distally, with 10 anterior spines and series of long medial setae; dactylus distinctly curved and of normal stoutness, with tip entire, about ½ of the length of propodus. PEREIOPOD 6 (Fig. 4 e). Coxa subquadrate, with medially concave ventral margin, unarmed; basis broad, with anterior and posterior border convex; anterior border with 10 small spines accompanied with small setae, posterior border with well-marked serration; ischium about as long as wide, with large simple spine on anterodistal corner; merus about 4 times as long as wide, with 5 short anterior spines, a pair of large distodorsal spines and 1 simple distoventral spine paired with a spinule; carpus about 4.5 – 5 times as long as wide, slightly shorter than merus, unarmed posteriorly, with 4 small anterior spines, and a distal pair of spines anteriorly and posteriorly; propodus (Fig. 4 f) about 7 times as long as proximal width, tapering distally, with 4 long anterior spines and series of long medial setae; dactylus distinctly curved, sharp, about ⅓ of the length of propodus. PEREIOPOD 7 (Fig. 4 g). Coxa almost rectangular; basis greatly broad, almost round, with convex anterior border and strongly convex posterior border; anterior border with 12 small conical spines, posterior border serrated, distal border with strong long spine; ischium about as long as wide, unarmed; merus broad, about 2.5 – 3 times as long as wide, with 4 anterior small spines and pair of anterodistal simple spines, 3 posterior spines and a pair of long posterodistal long spines; carpus about 5.5 times as long as wide, slightly longer than merus, with single or paired anterior spines and long simple setae posteriorly; propodus about 10 times as long as wide, tapering distally, with 4 small anterior spines and long setae posteriorly; dactylus straight, very long and slender, entire, about ⅓ of the length of propodus. PLEONITE 1 (Fig. 5 b). Posterodorsal area produced into 3 small teeth of which median is longest (Fig. 5 e); Ep 1 with normally developed posteroventral tooth, with posterior border weakly convex, covered with numerous simple setae. PLEONITE 2 (Fig. 5 b). Posterodorsal area produced into 3 small teeth of which median is longest (Fig. 5 e); Ep 2 with normally developed posteroventral triangular tooth, with posterior border distinctly convex, covered with numerous simple setae. PLEONITE 3 (Fig. 5 b). Posterodorsal area toothless (Fig. 5 e); Ep 3 with small posteroventral tooth and distinct rounded notch (Fig. 5 c), with posterior border convex. UROSOMITE 1. With well-developed dorsal lamina and posterodorsal tooth (Fig. 5 d); peduncle of U 1 with medial distal corner rounded, with 4 dorsolateral spines of which proximal is longest, with 1 dorsomedial spine and 1 ventromedial spine; outer ramus with 5 small outer spines and 4 small medial spines; inner ramus with 4 small outer spines and 7 small medial spines. UROSOMITE 2. With well-developed dorsal lamina and posterodorsal tooth (Fig. 5 d); peduncle of U 2 with 4 slender dorsolateral distal spines, with 1 dorsomedial spine and 1 ventromedial spine; outer ramus with 5 small outer spines and 4 small medial spines; inner ramus with 4 small outer spines and 4 small medial spines. UROSOMITE 3. With sharp medial projection (Fig. 5 i), with 1 – 2 lateral spines, 1 long posterolateral tooth and 3 posterodorsal spines; outer ramus with 3 – 4 small outer spines and 4 small medial spines; inner ramus with 6 small outer spines and 4 small medial spines (Fig. 5 h). TELSON (Fig. 2 k). With cleft reaching 0.85 – 0.9 of telson length; distal teeth about ¼ of the length of telson, medial teeth longer than outer teeth, 2 interdental spines long and slender, overreaching outer teeth. COLORATION. General coloration of body and all appendages translucent white with large light and dark brown spots; some segments of appendages dark red or with dark red spots; eyes brightly white (Fig. 1). BODY SIZE. Largest collected female = bl 6.5 mm; largest collected male mostly similar in size to largest female, with bl 6.5 mm. Taxonomic remarks The new species is distinctly morphologically similar to L. geminata and L. serratoides. At the same time, the new species can be clearly distinguished by several morphological features not known from the latter species. From L. geminata (see description, presented by Barnard (1969 )), the new species can be distinguished by the following characters: smaller dorsal crest on urosomites 1 and 2 (Fig. 5 d); Mx 1 with wide, shovelshaped article 3 of palp (Fig. 2 h); shorter and wider merus of P 1 and P 2 (see Fig. 4 a – b); slender propodal segments of PP 5 – 7 (see Fig. 4 c – g); absence of long proximal seta of peduncle of U 1 (see Fig. 5 f); shape of medial teeth of telson (Fig. 2 k), which are significantly longer and accompanied by 2 long interdental spines. At the same time, L. geminata seems to be more closely related to the new species by its very similar body coloration, the presence of a small dorsal crest on urosomites 1 and 2, short articles of peduncle of A 1, relatively stout distal segments of PP 3 – 4 (especially merus), and other morphological features that clearly separate both species from their relative L. serratoides. From L. serratiodes (after Tzvetkova 1967), the new species is easily separated by the following characters: presence of a dorsal crest on urosomites 1 and 2; stout articles of peduncle of A 1 and A 2 (Fig. 2 d – e); wide distal article of palp of Mx 1; stout and wider distal segments, especially merus, of PP 1 – 2; slender propodal segment of PP 5 – 7; length and shape of medial teeth of telson, which are significantly longer and accompanied by 2 long interdental spines. In addition, relatively stout and wide segments of PP 3 – 4 are distinguishing features that separate the aforementioned species from tropical relatives, such as L. japonica and L. serrata (e. g., Nagata 1965; Azman & Othman 2013). From L. japonica and L. serrata, known from the Seto Inland Sea in southern Japan (see Nagata 1965), the new species can be distinguished by longer rostrum, mandibular palp with longer and slender articles, especially distal one; shorter and stouter articles of peduncle A 1 and A 2; stouter distal segments of PP 3 – 4, especially stout and wide merus of P 3; significantly shorted dactyli of PP 5 – 7; slender rami of U 3 and longer median teeth of telson. From Liljeborgia hwanghaensis Kim & Kim, 1990, known from the Korean coasts of the Yellow Sea (37 ° 23 ′ N, 126 ° 35 ′ E) (see Kim & Kim 1990), the new species can be clearly separated by the posterodorsal armature of pleonites 1 and 2 (3 teeth in the new species vs 5 teeth in L. hwanghaensis) and shorter median teeth of telson. Habitat and ecology Specimens of Liljeborgia associata sp. nov. were collected inside the burrows of Urechis unicinctus (Drasche, 1880) (Polychaeta: Echiura: Urechidae), representing the first case of an association between liljeborgiid amphipods and spoon worms (Echiura). The spoon worm U. unicinctus lives in large U-shaped burrows constructed in muddy and sandy sediments in the inter- and subtidal zones in the Sea of Japan and the Yellow Sea (Abe et al. 2014; pers. obs.). About 20 % of the studied spoon worms burrows were inhabited by a single individual of the new species, which may indicate aggressive territorial behavior.
description
Figs 1 – 5
diagnosis
Diagnosis A 1 with stout articles 2 (about as long as wide) and 3 (about 1.5 times as long as wide), article 2 with dorsal projection produced into a rounded lobe; palp of Md with long and slender articles, article 3 almost equal to articles 1 and 2, about 5 times as long as wide; palp of Mx 1 with broad shovel-shaped article 1; stout articles 3 and 2 of A 2, article 3 about as long as wide and article 2 about 3 times as long as wide; P 1 and P 2 with short and wide merus, about 3 times as long as wide; PP 5 – 7 with slender propodal segments, about 6, 7 and 10 times as long as wide, respectively; posterodorsal area of Pleonites 1 and 2 produced into 3 small teeth of which the median one is the longest; Urosomites 1 and 2 with wellmarked dorsal crest; Telson with long distal teeth, accompanied by 2 interdental long and slender spines.
distribution
Distribution The specimens of Liljeborgia associata sp. nov. were found in the southern part of the Peter the Great Bay and the northern part of Posjeta Bay in the Sea of Japan (Russian Federation) (see Fig. 1), where the present study was accomplished. The distribution of the new species is probably related with the distribution range of its host, U. unicinctus (see Abe et al. 2014).
etymology
Etymology The species is named after its symbiotic lifestyle.
materials_examined
Type material Holotype PACIFIC OCEAN • ♀ (bl 6.5 mm); Sea of Japan, Primorye, Peter the Great Bay, Vostok Bay, in front of the scientific station “ Vostok ”; 42 ° 54 ′ 35.8 ″ N, 132 ° 44 ′ 08.7 ″ E; depth 1 – 1.5 m; 30 – 31 Jul. 2017; I. Marin leg.; shore in front of the laboratory, sandy-gravel bottom overgrown with sea grass; yabbypump; from burrows of spoon worm U. unicinctus; ZMMU Mb- 1153. Paratypes PACIFIC OCEAN • 1 ♂; same data as for holotype; ZMMU Mb- 1154 • 1 ♀; same data as for holotype; GenBank: MN 704855, MN 704856; ZMMU Mb- 1155. Additional material PACIFIC OCEAN • 8 ♀♀, 1 ♂; same data as for holotype; LEMMI • 5 ♀♀; Sea of Japan, Primorye, Posjeta Bay, Troitza Bay; 42 ° 38 ′ 60.0 ″ N, 131 ° 07 ′ 27.8 ″ E; depth 1 – 1.5 m; Jul. 2019; I. Marin leg.; muddy sand; inside burrow of spoon worm U. unicinctus; yabby-pump; LEMMI • 1 ♀; Peter the Great Bay, Astafieva Bay; 42 ° 36 ′ 52.2 ″ N, 131 ° 12 ′ 01.1 ″ E; depth 1 – 1.5 m; Jul. 2019; I. Marin leg.; sand bottom; inside burrow of spoon worm U. unicinctus; yabby-pump; LEMMI.
Name
- Homonyms
- Liljeborgia associata Marin 2020