Cerapus bumbumiensis, Nurshazwan & Ahmad-Zaki & Azman, 2020

Nurshazwan, J., Ahmad-Zaki, A. B. & Azman, B. A. R., 2020, A new species of Cerapus (Amphipoda: Senticaudata: Ischyroceridae) from Pulau Bum Bum, Sabah, Malaysia, with an identification key to Cerapus species, Zootaxa 4802 (3), pp. 519-533 : 521-531

publication ID	https://doi.org/ 10.11646/zootaxa.4802.3.7
publication LSID	lsid:zoobank.org:pub:80A69FB8-8A14-4EB1-A909-CA78AC635835
DOI	https://doi.org/10.5281/zenodo.10564423
persistent identifier	https://treatment.plazi.org/id/472487E1-0A6E-FFD3-FF46-FCACFDFC7DC2
treatment provided by	Plazi
scientific name	Cerapus bumbumiensis
status	sp. nov.

Treatment

Cerapus bumbumiensis View in CoL sp. nov.

Figs 2–10 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 View FIGURE 10

Etymology. Named after the type locality, Pulau Bum Bum, Sabah, Malaysia.

Material examined. Holotype: male, 3.5 mm, UKMMZ-1606 ( Fig. 2 A View FIGURE 2 ), ND Divers House reef, Pulau Bum Bum, Semporna, Sabah, Malaysia, 4°26’43.2”N 118°39’08.1”E, SCUBA diving, 29 November 2018, depth 10.5 m, coll. Abu-Bakar, A.Z., Azman, B.A.R., Dendy, A.O., & Avilla, G.S. GoogleMaps Allotype: female, 3.5 mm, UKMMZ-1607 ( Fig. 2 C View FIGURE 2 ); same station data.

Paratypes: 1 male, 3 females, 2 juveniles, UKMMZ-1608; 1 male, 2 females, 2 juveniles, UKMMZ-1609; 1 male, 2 females, 2 juveniles, UKMMZ-1610; same station data.

Type locality. ND Divers House reef, Pulau Bum Bum, Semporna, Sabah, Malaysia.

Diagnosis. Head, rostrum short. Male and female antenna 1 with aesthetascs at flagellum. Constriction between pereonite 1 and 2 present. Male gnathopod 2 carpochelate, carpus large with long defining posterior tooth and welldeveloped anterodistal tooth. Male and female pereopod 6 coxa with fine hair/fringe setae ventrally, pereopod 5 merus posterior lobe with 1 plumose seta and pereopod 5 to 7 dactylus with accessory hook. Female pereopod coxa large, about 2.7 x as broad as deep. Telson with deep cleft.

Description. Based of male (holotype, UKMMZ-1606). Size, 3.5 mm ( Fig. 3 View FIGURE 3 ). Body elongated, cylindrical.

Head. Rostrum short; apically subacute/apically acute; 0.1 x length of head. Head with lateral cephalic lobe with distal corner acute with ventral corner rounded. Rudimentary sternal keel between pereonite 1 and 2. Antenna 1 ( Fig. 3 A View FIGURE 3 1 View FIGURE 1 ) well developed, short setae dorsally, long setae ventrally, about 0.6 x length of body; peduncle 1.6 x length of flagellum, peduncle article 1 with proximoventral swelling, peduncle article 3 subequal to peduncle article 2, both are slender; flagellum 0.6 x length of peduncle, with 5 articles with several aesthetascs, flagellum article 1 the longest, flagellum article 5 the shortest with 1 aesthetasc. Antenna 2 ( Fig. 3 A View FIGURE 3 2 View FIGURE 2 ) well developed, slightly shorter than antenna 1, setation similar to antenna 1; peduncle article 5 longer than article 4; flagellum with 4 articles, article 4 is the smallest, flagellum article 1 about as long as flagellum article 2 and 3 combined. Upper lip ( Fig. 4 View FIGURE 4 UL) symmetrically bilobed, small setulae apically. Lower lip ( Fig. 4 View FIGURE 4 LL) setulose on inner and outer lobes. Mandibles ( Fig. 4 View FIGURE 4 MD) right incisor with 5 teeth; right lacinia mobilis 5 – cuspidate (5 teeth); right mandible with 2 broad accessory spine and 2 intermediate plumose setae; molar triturating; molar flake absent; palp elongated, slender; article 2 slightly longer than article 3, 1.03 x as long as article 3, no seta present; article 3 with 4 long plumose setae and 2 long setae and 1 short seta. Maxilla 1 ( Fig. 4 View FIGURE 4 MX 1) inner plate small with apical plumose seta; outer plate with 1 apical robust seta, 9 apical setae with 4 serrated laterally (5 apical setae and 4 bifurcate) and 1 seta (subapical seta); palp biarticulate, with 5 serrated apical robust setae and 3 setae (subapical setae). Maxilla 2 ( Fig. 4 View FIGURE 4 MX 2) outer plate broader than inner plate, with 6 plumose setae and 7 simple setae; inner plate with 6 setae and 4 plumose setae. Maxilliped ( Fig. 4 View FIGURE 4 MP) inner plate subquadrate; with 4 stout nodular setae/spine and 5 setae; outer plate with 3 long apical setae, 3 strong setae, 1 stout nodular spine and 22 setae (10 of them are submerginal); palp article 1 with single median seta; article 2 is the longest with a few distomedial simple setae; article 3 with setae distally; article 4 with 2 median setae.

Pereon. Gnathopod 1 ( Fig. 3G View FIGURE 3 1 View FIGURE 1 )weakly subchelate, length ratio from basis to dactylus 2.5:1:1.3:2.3:2.3:1.7;coxa broader than depth; carpus subequal length to propodus, lobate posterior margin with setae and plumose setae, anterior margin less setae; propodus oval shape, length 2.1 x width, posterior with setae and plumose setae, palm oblique, serrated and with setae; dactylus well developed, palmar margin lacking serration, crenulated posterior margin with 2 spines. Gnathopod 2 ( Fig. 3 G View FIGURE 3 2 View FIGURE 2 ) carpochelate, length ratio from basis to dactylus 2.6:1:1.6:5.3:3.3:1.7; coxa broader than depth, larger than coxa 1; basis length equal to width, short setae on both anterior and posterior margin; carpus massive, length 2.1 x width, palmer margin oblique with long posterior defining tooth and well-developed anterodistal tooth adjacent to propodus articulation, anterodistal tooth with serrated; propodus length 4.1 x width, not recurved, with short setae on anterior and posterior margins, posterior serrated near anterodistal tooth of carpus and near articulation of dactylus; dactylus length 6 x width, with short setae on anterior and posterior margin. Pereopod 3 ( Fig. 5 P View FIGURE 5 3 View FIGURE 3 ) length ratio from basis to dactylus 6.3:3.1:3.1:1.3:1.2:1; coxa more than 3 times as broad as deep; basis length 2.1 x width, anterior margin with 4 short setae and 1 on the anteroproximal corner; ischium same length as merus; merus without ridges; carpus with 2 short setae along distal of posterior margin; propodus with 1 setae on anterior margin near articulation of dactylus. Pereopod 4 ( Fig. 5 P View FIGURE 5 4 View FIGURE 4 ) length ratio from basis to dactylus 7.6:4.3:4.3:1.3:2.3:1; coxa with more than twice as broad as deep; basis, length 1.9 x width; ischium length equal to merus; merus without ridges; dactylus with nail. Pereopod 5 ( Fig. 5 P5 View FIGURE 5 ) length ratio from basis to dactylus 4.3:1.8:2.6:1.4:2.4:1; coxa 1.6 times as broad as deep, as long as 2.3 x basis width; basis globular, length equals to width; merus posterior lobe with 1 plumose seta, smaller anterior lobe with 1 seta; carpus smaller than merus, posterior lobe with fine hair, bearing a seta; propodus cylindrical; dactylus unguis with 3 accessory hooks. Pereopod 6 ( Fig. 5 P View FIGURE 5 6 View FIGURE 6 ) length ratio from basis to dactylus 8.5:2.9:5.3:2.9:3.8:1; coxa dorsal margin with fine hair, about 2.1 times as broad as deep; basis length 1.8 x width with short setae on anterior and posterior margin; ischium length equal to carpus, length 2.1 x width; merus 2.1 x as long as broad with short simple setae on anterior and posterior margin; carpus slightly longer than broad, with long setae on anterodistal corner and 2 short simple setae on posterodistal corner; propodus shorter than merus; dactylus unguis with 2 accessory hooks. Pereopod 7 ( Fig. 5 P View FIGURE 5 7 View FIGURE 7 ) length ratio from basis to dactylus 6.2:1.8:4.5:2.7:3.8:1; coxa 1.7 x as long as deep; basis with several short simple setae on anterior and posterior margin; ischium with 1 short posterodistal seta; merus with several short simple setae on anterior and posterior margin; carpus shorter than merus with long simple setae at anterodistal and posterodistal; propodus slightly longer than carpus with anterodistal groups of long and medium size simple setae; dactylus unguis with 2 accessory hooks. Gills on gnathopod 2 to peraeopod 6.

Pleon. Pleopods 1 to 3 decreasing in size. Pleopod 1 ( Fig. 6 View FIGURE 6 PL1) peduncle bearing 2 retinacula, without plumose setae distomarginally; outer ramus slightly shorter than inner ramus, with 5 articles; outer ramus broader than inner ramus, with 2 articles, first article is the largest. Pleopod 2 ( Fig. 6 View FIGURE 6 PL2) peduncle with 2 retinacula, without plumose setae distomarginally; outer ramus 3.3 x as long as inner ramus, with single article; inner ramus reduced, 3.2 x as long as broad, 1 plumose seta and single article. Pleopod 3 ( Fig. 6 View FIGURE 6 PL3) peduncle with 2 retinacula, without plumose setae distomarginally; outer ramus about more than (2.3 x) twice as long as inner ramus; single article; inner ramus reduced, about (1.9 x) twice as long as broad, single article with 2 plumose setae.

Urosome. Uropod 1 ( Fig. 6 U View FIGURE 6 1 View FIGURE 1 ) biramous; peduncle 3.2 x as long as wide, provided with 3 dorsodistal row of robust setae and 1 simple outer distal seta; outer ramus shorter than peduncle, 1.5 x length of inner ramus, with outer row of spinules and 1 large apical spine, corona of short robust setae surrounding large terminal spine; inner ramus 0.7 x as long as outer ramus, with large apical spine, corona of short robust setae surrounding large terminal spine. Uropod 2 ( Fig. 6 U View FIGURE 6 2 View FIGURE 2 ) uniramous; peduncle 3.3 x as long as broad, 6.3 x as long as vestigial ramus; ramus with 2 hooks and 1 seta. Uropod 3 ( Fig. 6 U View FIGURE 6 3 View FIGURE 3 ) uniramous; peduncle 2.2 x as long as wide, with one seta on inner margin; ramus vestigial, conspicuously small with 2 hooks. Telson ( Fig. 6 T View FIGURE 6 ) deeply cleft, 0.7 x length of uropod 3, each lobe with 5 or 6 recurved hooks in two rows and an apical seta.

Female (Sexually dimorphic character). Based on allotype (UKMMZ-1607), length 3.5 mm ( Fig. 7 View FIGURE 7 ). Similar to male except for the following; Antenna 1 ( Fig 7 A View FIGURE 7 1 View FIGURE 1 ) less setae and less aesthetascs. Gnathopod 1 ( Fig. 7 G View FIGURE 7 1 View FIGURE 1 ) dactylus posterior margin serrated, with 4 spines. Gnathopod 2 ( Fig. 7 G View FIGURE 7 2 View FIGURE 2 ) slightly larger than gnathopod 1; carpus triangular, posterodistal corner with plumose setae and normal setae; propodus palm not serrated, with plumose setae and normal setae; dactylus posterior margin crenulated. Pereopod 5 ( Fig. 9 P View FIGURE 9 5 View FIGURE 5 ) coxa larger about 2.7 x as broad as deep, about 6.3 x longer than basis width; basis slight globular; dactylus with 2 accessory hooks. With 6 oostegites on segments 4–6.

Remarks. This new species has large carpus of male gnathopod 2 with long defining posterior tooth and welldeveloped anterodistal tooth. These inimitable characters are shared with the following nine other species: Cerapus alquirta ( Barnard & Drummond, 1981) , C. chaomai Lowry & Berents, 2002 , C. cudjoe Lowry & Thomas, 1991 , C. jonsoni Valério-Berardo, Thiago de Souza & Waiteman Rodrigues, 2008 , C. maculanigra Zeina & Asakura, 2017 , C. oceanicus Lowry, 1985 , C. thomasi Ortiz & Lemaitre, 1997 , C. volucola Lowry & Berents, 2005 and C. yuyatalay Lowry & Berents, 2002 . From these nine species, only two species ( C. jonsoni and C. yuyatalay ) exhibit the distinctive constriction between pereonite 1 and 2 that akin to C. bumbumiensis . However, C. bumbumiensis can be separated from C. jonsoni and C. yuyatalay by having deeply cleft telson.

This new species has close affinities to Cerapus chaomai from the Andaman Sea and C. pacificus from Fiji by having ventral setal fringe on coxa 6. However, by comparing the illustrations of both seagrass associated cerapids ( C. chaomai and C. pacificus ), Cerapus bumbumiensis sp. nov. clearly differs in the presence of unique constriction between pereonite 1 and 2; presence of 3 dorsodistal row of robust setae of uropod 1; lacking serration along inner palmar margin of dactylus gnathopod 1; and telson deeply cleft.

Cerapus bumbumiensis sp. nov. can be easily differentiated from the recently described Cerapus of the Northwest Atlantic ( C. slayeri ) and Gulf of Mexico ( C. ryanadamsi ) specimens by Drumm (2018) by the absence of hook on ventrodistal margin of uropod 1.