taxonID	type	description	language	source
5B2AE879FFEC7000FF3DD803FD70FAA6.taxon	materials_examined	Type material. Holotype, adult male, 2.5 mm, MABIK CR 00259499, Gadeokdo-dong, Gadeokdo, Gangseo-gu, Busan, Korea, 35 ° 00 ′ 44 " N, 128 ° 49 ′ 33 " E, 7 June 2024, collected using Light traps by K. W. Kim. Paratypes, adult female, 2.4 mm, MABIK CR 00259500, data same as holotype. The remaining paratypes (43 ♂, 23 ♀, 32 inds., DKUAMP 202512) in the collection of the corresponding author. Additional material examined. 12 inds. Yeongil-dong, Udo-myeon, Jeju, Korea, 33 ° 30 ' 11 " N, 126 ° 58 ' 07 " E, collected using Light traps, Y. H. Kim, 28 May 2024.	en	Lee, Jeong-Hyeon, Kim, Kyung-Won, Kim, Young-Hyo (2025): First record of the family Maxillipiidae (Crustacea: Malacostraca: Amphipoda) from Korea, including a new species and a new record species of the genus Maxillipius. Zootaxa 5717 (2): 277-290, DOI: 10.11646/zootaxa.5717.2.6, URL: https://doi.org/10.11646/zootaxa.5717.2.6
5B2AE879FFEC7000FF3DD803FD70FAA6.taxon	etymology	Etymology. The new species is named for its occurrence in Korea.	en	Lee, Jeong-Hyeon, Kim, Kyung-Won, Kim, Young-Hyo (2025): First record of the family Maxillipiidae (Crustacea: Malacostraca: Amphipoda) from Korea, including a new species and a new record species of the genus Maxillipius. Zootaxa 5717 (2): 277-290, DOI: 10.11646/zootaxa.5717.2.6, URL: https://doi.org/10.11646/zootaxa.5717.2.6
5B2AE879FFEC7000FF3DD803FD70FAA6.taxon	description	Description. Holotype adult male, MABIK CR 00259499. Body (Figs. 2 A, 3 A) small, 2.5 mm long, pereonites dorsally smooth, pleonites 1 – 2 carinate dorsodistally; head subquadrate, subequal in length to pereonites 1 – 3 combined; eye medium, subcircular, lateral cephalic lobe indistinct; pereonites 1 – 6 short, pereonite 7 longest; pleonites 1 – 2 (Fig. 3 B) with posterodorsal teeth, preceding tooth blunt, divided into two by a shallow notch; succeeding tooth narrow, with a small notch at the apex; epimeral plates 1 – 3, posteroventral corner minutely pointed. Antenna 1 (Fig. 3 C) elongate, sexually dimorphic; peduncular articles 1 – 2 short, subequal in length; peduncular article 3 subquadrate laterally, while medial portion extends into a pointed projection, with several rows of callynophores, fused with flagellum article 1; accessory flagellum absent; flagellum elongate, 25 - articulate. Antenna 2 (Fig. 3 D), peduncular articles 2 – 3 short, peduncular article 4 subrectangular, peduncular article 5 slender, longest; flagellum elongate, 41 - articulate. Upper lip (Fig. 3 E) ovate, apex pubescent. Lower lip (Fig. 3 F), inner lobe well developed, apex with pubescence; outer lobe covered with pubescence apically, mandibular process produced, acute distally, slightly curved. Left mandible (Fig. 3 G), incisor with 10 teeth; lacinia mobilis with 6 blunt teeth; accessory setal row with 3 pectinate setae; molar triturative with a seta; palp absent, replaced by a small simple seta. Right mandible (Fig. 3 H) similar to left mandible, incisor with 9 teeth; lacinia mobilis with over 16 serrated teeth; accessory setal row with 2 pectinate setae. Maxilla 1 (Fig. 3 I), inner plate reduced; outer plate subrectangular with 10 multi-cusped setal-teeth of which the 2 ones are nodular; palp large, broadening distally, uniarticulate, with 5 robust setae on apically, 13 long setae laterodistally. Maxilla 2 (Fig. 3 J), inner plate subrectangular, with 2 medial setae and 6 apical setae; outer plate slightly longer than inner plate, with 8 lateral setae and 7 apical setae. Maxilliped (Fig. 3 K), inner plate narrow with 2 apical setae; outer plate subovate, reaching the half of palp article 2, with 10 simple setae apicomedially; palp 4 - articulate, article 1 short, bearing a pinnate seta mediodistally, article 2 greatly expanded, with marginal and submarginal setae, article 3 longish ovate, curved medially, with long simple setae on the laterodistal region, article 4 falcate, with 3 small setae. Gnathopod 1 (Fig. 4 A) subchelate; coxa vestigial; basis subrectangular, anterior margin with 4 short setae, posterodistal margin nearly bared, with 1 distal seta; ischium short; merus subrectangular, extending posterodistally on half of carpus, with 6 simple setae posterodistally; carpus subtriangular, expanding distally, 11 simple setae posteriorly; propodus subovate, palm oblique, with rows of simple setae; dactylus falcate; length ratio of articles 2 – 7 = 1.00: 0.17: 0.29: 0.62: 0.50: 0.29. Gnathopod 2 (Fig. 4 B) simple, longer than gnathopod 1; coxa subovate, tapering anteroventrally with rounded corner; basis subrectangular, elongate; ischium and merus short; carpus elongate, slightly convex anteriorly, with several setae posteriorly; propodus characteristic in form, without palm, longish elliptical, distal two-thirds of posterior margin with a row of bicuspidate setae and two rows of simple setae submarginally; dactylus falcate; length ratio of articles 2 – 7 = 1.00: 0.12: 0.18: 1.00: 0.76: 0.29. Pereopod 3 (Fig. 4 C), coxa subquadrate, wider than long; basis elongate, subrectangular; ischium short; merus subrectangular, slightly widening distally; carpus subrectangular, slightly convex; propodus elongate, subrectangular, anterior margin with 5 unequal simple setae, posterior margin with 5 simple setae, distally setose; dactylus falcate, with a nail, posterior margin with setules; length ratio of articles 2 – 7 = 1.00: 0.15: 0.40: 0.79: 1.12: 0.59. Pereopod 4 (Fig. 4 D) similar to pereopod 3; length ratio of articles 2 – 7 = 1.00: 0.21: 0.43: 0.90: 1.21: 0.64. Pereopod 5 (Fig. 4 E, left,) subsimilar to both pereopods 3 and 4, but inverted, more elongated; coxa subquadrate, wider than long; basis subrectangular, ridged posterodistally; carpus to propodus elongate, rectangular, length ratio of articles 2 – 7 = 1.00: 0.20: 0.65: 1.38: 2.00: 0.80. Pereopod 6 (Fig. 4 F) characteristic in form, extremely elongate; coxa trapezoidal; basis subovate, posterodistally extending beyond end of ischium with triangular corner, anterior margin with 2 simple setae, posterior margin with 3 simple setae; ischium short, compressed; merus subovate, broad, subequal in size to basis; carpus slender, rectangular, both margins with 2 short setae; propodus extremely elongate, whip-like form, gradually narrowing distally, both margins with a row of short setae; dactylus indistinct; length ratio of articles 2 – 6 = 1.00: 0.19: 0.75: 1.56: 12.31. Pereopod 7 (Fig. 4 G) subsimilar to pereopod 5, but coxa small, subovate; basis subovate, broad, posterodistal corner acutely produced; carpus to propodus moderately setose; length ratio of articles 2 – 7 = 1.00: 0.21: 0.56: 1.32: 1.63: 0.47. Uropod 1 (Fig. 4 H, left) peduncle slender, rectangular, with 4 robust setae dorsolaterally, 2 robust setae dorsomedially, apicolateral corner with 1 process; rami lanceolate, with lateral and medial setules; outer ramus × 0.59 peduncle, with 2 simple setae laterally; inner ramus longer, about 1.46 × outer ramus. Uropod 2 (Fig. 4 I) subsimilar to uropod 1, but peduncle shorter than that of uropod 1, with 1 dorsolateral and 1 apicomedial robust seta; outer ramus short, × 0.84 peduncle, with 1 lateral seta; inner ramus longer, about 1.88 × outer ramus. Uropod 3 (Fig. 4 I) subsimilar to uropod 2; peduncle unarmed, subequal in length to outer ramus; outer ramus slightly short than inner one. Telson (Fig. 4 I) suboval, entire, wider than long, width 1.7 × length, with 4 short setae subdistally. Paratype, adult (ovigerous) female, MABIK CR 00259500. Body (Figs. 2 B, 5 A) about 2.4 mm long; similar to male; slightly depressed dorsoventrally; coxae 2 (Fig 5 C) – 5 more expended than those of male. Antenna 1 (Fig. 5 B) showing sexual dimorphism, peduncular article 3 without mediodistal projection and callynophore, several ventrodistal aesthetascs on flagellum articles. Variation. Body length at maturity of male is 2.5 mm and female is 2.4 mm, based on an ovigerous specimen. The number and shape of dorsal teeth on pleonites 1 and 2 in female exhibit age variation. In this mature female (2.4 mm), pleonite 1 (Fig. 5 D) with 2 dorsal teeth and pleonite 2 posterodorsal tooth with apical notch. Subadult female (1.8 mm), however, pleonite 1 (Fig. 5 E) with 2 dorsal teeth and pleonite 2 posterodorsal tooth without notch. On the other hand, juvenile (1.6 mm), pleonite 1 (Fig. 5 F) dorsal tooth underdeveloped and pleonite 2 posterodorsal tooth without apical notch. Molecular data. CO 1 gene sequences (GenBank accession numbers PV 535648, PV 535649, PV 535650, PV 535651, PV 540241, PV 540243) were obtained from six specimens of Maxillipius koreanus sp. nov. These sequences were aligned and compared with sequences from M. rectitelson (PV 535652, PV 535653, PV 540242) (Table 1). The intraspecific variation of the CO 1 gene sequence of M. koreanus sp. nov. ranged from 0.0 % to 1.0 %, indicating genetic homogeneity within the species. In contrast, the interspecific variation ranged from a low of 21.4 % to a high of 22.7 % (between M. koreanus sp. nov. and M. rectitelson) (Fig. 9, Table 2).	en	Lee, Jeong-Hyeon, Kim, Kyung-Won, Kim, Young-Hyo (2025): First record of the family Maxillipiidae (Crustacea: Malacostraca: Amphipoda) from Korea, including a new species and a new record species of the genus Maxillipius. Zootaxa 5717 (2): 277-290, DOI: 10.11646/zootaxa.5717.2.6, URL: https://doi.org/10.11646/zootaxa.5717.2.6
5B2AE879FFEC7000FF3DD803FD70FAA6.taxon	discussion	Remarks. Among the two known species of Maxillipius, the newly identified species, Maxillipius koreanus sp. nov. is similar to M. rectitelson in having the following characteristics: 1) pleonites 1 – 2 with posterodosal process; 2) gnathopod 1, carpus subtriangular with a posterior lobe; 3) gnathopod 1, propodus subovate. However, M. koreanus sp. nov. is distinguished from M. rectitelson based upon the following features (different characters of M. rectitelson in brackets): 1) pleonite 2, posterodorsal tooth with an apical notch (vs. without notch); 2) female gnathopod 1, basis posteriorly bare (vs. with three posteromarginal setae); 3) gnathopod 2, coxa trapezoidal, narrowing anteroventrally (vs. subrectangular, anterior margin blunt); 4) gnathopod 2 simple, propodus without palm (vs. subchelate, with palm); 5) gnathopod 2, posterior margin of propodus with bicuspidate setae and simple setae (vs. with simple setae); and 6) pereopods 3 – 5 and 7, dactyli posterior margins without serrulation (vs. with serrulation). To validate this distinction, molecular sequences of the COI gene from both previously identified and newly identified samples of M. koreanus sp. nov. and M. rectitelson in Korea were compared and analyzed (Fig. 9, Table 2). Based on these morphological and genetic differences, we conclude that M. koreanus sp. nov. represented a novel species.	en	Lee, Jeong-Hyeon, Kim, Kyung-Won, Kim, Young-Hyo (2025): First record of the family Maxillipiidae (Crustacea: Malacostraca: Amphipoda) from Korea, including a new species and a new record species of the genus Maxillipius. Zootaxa 5717 (2): 277-290, DOI: 10.11646/zootaxa.5717.2.6, URL: https://doi.org/10.11646/zootaxa.5717.2.6
5B2AE879FFEC7000FF3DD803FD70FAA6.taxon	distribution	Distribution. Korea (Busan, Udo Island).	en	Lee, Jeong-Hyeon, Kim, Kyung-Won, Kim, Young-Hyo (2025): First record of the family Maxillipiidae (Crustacea: Malacostraca: Amphipoda) from Korea, including a new species and a new record species of the genus Maxillipius. Zootaxa 5717 (2): 277-290, DOI: 10.11646/zootaxa.5717.2.6, URL: https://doi.org/10.11646/zootaxa.5717.2.6
5B2AE879FFE67004FF3DDAD6FC4CFAF4.taxon	materials_examined	Material examined. Adult male, 2.5 mm, MABIK CR 00259501, adult female, 2.3 mm, MABIK CR 00259502, Udo island, Jeju, Korea, 33 ° 31 ′ 32 " N, 126 ° 54 ′ 54 " E, 29 May 2024, collected with SCUBA by S. J. Lee. The remaining samples (50 inds., DKUAMP 202513) in the collection of the corresponding author.	en	Lee, Jeong-Hyeon, Kim, Kyung-Won, Kim, Young-Hyo (2025): First record of the family Maxillipiidae (Crustacea: Malacostraca: Amphipoda) from Korea, including a new species and a new record species of the genus Maxillipius. Zootaxa 5717 (2): 277-290, DOI: 10.11646/zootaxa.5717.2.6, URL: https://doi.org/10.11646/zootaxa.5717.2.6
5B2AE879FFE67004FF3DDAD6FC4CFAF4.taxon	description	Description. Adult male, MABIK CR 00259501. Body (Figs. 6 A, 7 A) small, 2.5 mm long, pereonites dorsally smooth, pleonites 1 – 2 carinate dorsodistally; slightly depressed dorsoventrally; head subquadrate, subequal in length to pereonites 1 – 3 combined; eye large, subcircular, lateral cephalic lobe indistinct; pereonites 1 – 6 short, pereonite 7 longest; pleonites 1 – 2 (Fig. 7 B) with posterodorsal teeth, posterolaterally ridged with shallow process; preceding tooth blunt, divided into two by a shallow notch, succeeding tooth shallow; epimeral plates 1 – 3 posteroventral corners minutely pointed. Antenna 1 (Fig. 7 C) elongate, sexually dimorphic; peduncular articles 1 – 2 short, peduncular article 2 shorter than peduncular article 1; peduncular article 3 subquadrate laterally, while with a distomedial portion extends into a pointed projection, elongate medial surface, positioned dorsally, expanded into a triangular lobe tapering toward the apex, with several rows of medial callynophores, fused with flagellum article 1; accessory flagellum absent; flagellum elongate. Gnathopod 1 (Fig. 7 D) subchelate; coxa vestigial; basis subrectangular, anterior margin with 4 short setae, posterior margin nearly bared, with 1 simple seta distally; merus subrectangular, extending posterodistally, with 5 simple setae posterodistally; carpus subtriangular, expanding distally, 10 simple setae posteriorly; propodus subovate, palm oblique, with rows of simple setae; dactylus falcate; length ratio of articles 2 – 7 = 1.00: 0.24: 0.35: 0.71: 0.50: 0.34. Gnathopod 2 (Fig. 7 E) subchelate, much longer than gnathopod 1; coxa subrectangular, tapering anteroventrally with rounded corner; basis subrectangular, elongate, nearly bared; carpus elongate, with several setae posteriorly; propodus characteristic in form, longish elliptical, distal half of posterior margin with irregularly arranged setae, palm short, obtuse; dactylus falcate; length ratio of articles 2 – 7 = 1.00: 0.18: 0.26: 1.00: 0.70: 0.26. Pereopod 3 (Fig. 7 F), coxa subquadrate, wider than long; basis elongate, subrectangular, anterior margin with a pinnate seta and 5 short simple setae; merus subrectangular, slightly widening distally; carpus subrectangular; propodus elongate, subrectangular, both margins with simple setae; dactylus falcate, with a nail, posterior margin with serrulation; length ratio of articles 2 – 7 = 1.00: 0.27: 0.45: 0.85: 1.22: 0.69. Pereopod 4 (Fig. 7 G) similar to pereopod 3; length ratio of articles 2 – 7 = 1.00: 0.30: 0.47: 0.89: 1.30: 0.67. Pereopod 5 (Fig. 7 H) coxa subquadrate, wider than long; basis subrectangular, slightly expanded posterodistally, with subacute process, midposterior margin with a pinnate seta, laterodistal surface with a robust seta. Pereopod 6 (Fig. 7 I) characteristic in form, extremely elongate; coxa trapezoidal; basis subcircular, posterodistally extending beyond end of ischium with triangular corner, midposterior margin with a pinnate seta; ischium short; merus subovate, broad, subequal in length to basis. Pereopod 7 (Fig. 7 J), coxa small, subtriangular; basis subovate, broad, posterodistal corner acutely produced, posterior margin with a pinnate seta, laterodistal surface with 2 robust setae. Paratype, adult (ovigerous) female, MABIK CR 00259502. Body (Figs. 6 B, 8 A) about 2.3 mm long; similar to male; coxae 2 – 5 more expended than those of male. Gnathopod 1 (Fig. 8 B) similar to that of male, but basis posterior margin with 3 long setae. Gnathopod 2 (Fig. 8 C) similar to that of male; but coxa subrectangular. Pereopod 6 (Fig. 8 D) similar to that of male; propodus extremely elongate, whip-like form, gradually narrowing distally; dactylus indistinct; length ratio of articles 2 – 6 = 1.00: 0.22: 0.78: 1.52: 15.61. Uropod 1 (Fig. 8 F), peduncle slender, rectangular, with 3 robust setae dorsolaterally, 3 robust setae dorsomedially, and apicolateral corner with 1 process. Uropod 2 (Fig. 8 F) subsimilar to uropod 1, but peduncle shorter than that of uropod 1, marginally bared. Uropod 3 missing Telson (Fig. 8 F) subrectangular, entire, wider than long, width 1.9 × length, with 4 short setae distally. Variation. Body length at maturity of male is 2.5 mm and females are 2.8 – 2.9 mm, based on an ovigerous specimens. Morphological variations among different life stages were observed. In these 2 mature females, pleonite 1 (Figs. 8 H, I) with 3 – 4 dorsal teeth and pleonite 2 posterodorsal tooth without notch. Smaller female (2.3 mm), however, pleonite 1 (Figs. 8 E) with 2 dorsal teeth and pleonite 2 posterodorsal tooth without notch. On the other hand, small juvenile (1.8 mm), pleonite 1 (Figs. 8 G) dorsal tooth underdeveloped and pleonite 2 posterodorsal tooth without apical notch. Molecular data. CO 1 gene sequences (GenBank accession numbers PV 535652, PV 535653, PV 540242) were obtained from three Maxillipius rectitelson specimens from Korean waters. These sequences were aligned and compared with CO 1 sequences from M. koreanus sp. nov. (PV 535648, PV 535649, PV 535650, PV 535651, PV 540241, PV 540243) collected from Korea (Table 1). Intraspecific variation of the CO 1 gene sequence of M. rectitelson ranged from 0.0 to 0.1 %, while interspecific variation ranged from a low of 21.4 % to a high of 22.7 % (M. rectitelson and M. koreanus sp. nov.) (Fig. 9, Table 2). These genetic differences provide additional support for the recognition of M. rectitelson and M. koreanus sp. nov. as distinct species.	en	Lee, Jeong-Hyeon, Kim, Kyung-Won, Kim, Young-Hyo (2025): First record of the family Maxillipiidae (Crustacea: Malacostraca: Amphipoda) from Korea, including a new species and a new record species of the genus Maxillipius. Zootaxa 5717 (2): 277-290, DOI: 10.11646/zootaxa.5717.2.6, URL: https://doi.org/10.11646/zootaxa.5717.2.6
5B2AE879FFE67004FF3DDAD6FC4CFAF4.taxon	discussion	Remarks. As previously mentioned, Maxillipius rectitelson is distinguishable from M. koreanus sp. nov. based on several morphological features. Additionally, M. rectitelson can be differentiated from its congener, M. commensalis based on the following features: 1) gnathopod 1, carpus triangular with posterodistal lobe (vs. subrectangular without lobe); 2) gnathopod 1, propodus ovate (vs. subovate to elliptical); and 3) pleonite with dorsal process (vs. without process) (Thomas 1996). Our specimens are consistent with the descriptions provided by Ledoyer (1973) and Coleman (2009). However, dorsolateral process of pleonites appears less distinct compare to Coleman’s (2009) description. These morphological differences may be attributed to size related variation or local population differences.	en	Lee, Jeong-Hyeon, Kim, Kyung-Won, Kim, Young-Hyo (2025): First record of the family Maxillipiidae (Crustacea: Malacostraca: Amphipoda) from Korea, including a new species and a new record species of the genus Maxillipius. Zootaxa 5717 (2): 277-290, DOI: 10.11646/zootaxa.5717.2.6, URL: https://doi.org/10.11646/zootaxa.5717.2.6
5B2AE879FFE67004FF3DDAD6FC4CFAF4.taxon	distribution	Distribution. Australia, China, Korea (Udo Island), Madagascar.	en	Lee, Jeong-Hyeon, Kim, Kyung-Won, Kim, Young-Hyo (2025): First record of the family Maxillipiidae (Crustacea: Malacostraca: Amphipoda) from Korea, including a new species and a new record species of the genus Maxillipius. Zootaxa 5717 (2): 277-290, DOI: 10.11646/zootaxa.5717.2.6, URL: https://doi.org/10.11646/zootaxa.5717.2.6
