Floresorchestia mkomani, Bichang’A & Kioko & Liu & Li & Hou, 2021

Bichang’A, Joshua Sese, Kioko, Esther N., Liu, Hongguang, Li, Shuqiang & Hou, Zhonge, 2021, Two species of Talitridae (Crustacea, Amphipoda) from Kenya, Zootaxa 4927 (3), pp. 331-358 : 334-349

publication ID	https://doi.org/ 10.11646/zootaxa.4927.3.2
publication LSID	lsid:zoobank.org:pub:D3F302C7-DE38-4226-8BCD-06A82675105B
DOI	https://doi.org/10.5281/zenodo.4542302
persistent identifier	https://treatment.plazi.org/id/038BC150-3714-8A52-FF10-FF71AFF34539
treatment provided by	Plazi
scientific name	Floresorchestia mkomani
status

Treatment

Floresorchestia mkomani View in CoL Bichang’a & Hou, sp. nov.

( Figs 2 View FIGURE 2 , 4–11 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 View FIGURE 10 View FIGURE 11 )

Type material. Holotype ³, 7.0 mm ( NMK /INV/ AMP/0001 View Materials ), English Point Beach , Mkomani, Mombasa County, Kenya, S 04.05763 °, E 039.68376 °, 4 m a. s. l., 29 th July 2018, J. Sese and G. Kioko GoogleMaps . Paratype ♀ ( NMK /INV/ AMP/0002 View Materials ), same data as holotype GoogleMaps .

Other materials. Two males, four females, and one juvenile ( NMK /INV/ AMP/0003 View Materials ), both with the same data as holotype. Two male specimens were used for molecular analysis, and the sequences were submitted to GenBank ( MW 363126 View Materials and MW 363127 View Materials ) GoogleMaps .

Ecological type. Beach hoppers supralittoral type, often burrowing in sand and leaf litter on the beach during low tide when temperatures are high. No Mangroves or other significant coastal vegetation was recorded at the collection site.

Etymology. The specific name refers to the type locality and is a noun in apposition.

Diagnosis. F. mkomani Bichang’a & Hou, sp. nov., a relatively small-sized species, can be easily distinguished by male gnathopod I posterior margins of merus, carpus, and propodus with a prominent tumescent hump; five dentate lacinia mobilis of the left mandible in male and only four in female; pereopod IV dactylus thickened proximally and have a small protrusion towards the mid of its posterior margin; pereopod VII sexually dimorphic; uropod I outer ramus marginally bare; epimera II and III with vertical slits just above the ventral margin.

Description of male. Based on the holotype (NMK/INV/AMP/0001), 7.0 mm ( Fig. 2 View FIGURE 2 ). Antenna I ( Fig. 4A View FIGURE 4 ), shorter than antenna II, not exceeding two-fifths of antenna II peduncle article V; flagellum with four articles. Antenna II ( Fig. 4B View FIGURE 4 ), 0.4 times as long as body length; peduncle article V 1.5 times as long as peduncle article IV; flagellum 2.8 times as long as peduncle article V, with 15 articles, final article ( Fig. 4C View FIGURE 4 ), cone-shaped and minute with an apical cluster of overlapping setae.

Lower lip ( Fig. 4D View FIGURE 4 ), bilobed, apical and inner margins of the outer plate covered with fine setae. Left mandible ( Fig. 4E View FIGURE 4 ), with seven dentate incisor, five cuspidate lacinia mobilis, and five pappose setae; right mandible ( Fig. 4F View FIGURE 4 ), with five dentate incisor; bicuspidate lacinia mobilis with inner plate with 12–15 dentitions and an outer plate with four dentitions; molar well developed and with one pappose seta. Maxilla I ( Fig. 4G View FIGURE 4 ), with a slender inner plate with two terminal setae; outer plate distal margin with nine robust setae with dentition formulae 4̅4̅4̅4̅4̅3̅4̅2̅2; one small articulate palp present. Maxilla II, inner plate ( Fig. 4I View FIGURE 4 ), distal margin edge with smooth-edged blunt setae, ventral side with rugged edged setae, and a large subapical pappose seta; outer plate ( Fig. 4H View FIGURE 4 ), with 9̅11 smooth-edged, short and blunt setae, and six slightly rugged edged relatively longer setae. Maxilliped ( Fig. 4J View FIGURE 4 ), inner plate distal margin with three unequal sized stout teeth and pappose setae; outer plate with apical setae; palp article II distomedial lobe well developed, palp article III slightly longer than wide, palp article IV button-shaped and reduced.

Gnathopod I ( Fig. 5 View FIGURE 5 A–B), subchelate and sexually dimorphic; coxa I smaller than coxa II, ventral margin with four spines; merus, carpus, and propodus posterior margins with a well-developed tumescent hump; basis 1.2 times as long as the carpus; merus posterolateral side, at the base of the lobe, with one robust bifid seta; carpus 1.9 times as long as broad, posterodistal lobe well developed, with three robust bifid setae; propodus subtriangular, 0.8 times as long as carpus, with four robust setae at the base of the well-developed posterodistal lobe, posterior margin with four evenly spaced robust setae and three grouped set of long stiff setae; dactlylus cuspidactylate. Gnathopod II ( Fig. 5 View FIGURE 5 C–E), subchelate and sexually dimorphic; basis with a reduced proximal end, anterior margin smooth, and the posterior margin with five short robust setae; ischium ( Fig. 5 D View FIGURE 5 ), with a rounded lobe on mid anterior margin; propodus oval in shape and 1.6 times as long as wide; palm acute reaching about 41% along the posterior margin, posterior margin with 18 long and short bifid setae; dactylus curved, slender distally, with smooth posterior margin, and anterior margin with six small stout setae.

Pereopods III–VII ( Fig. 6 View FIGURE 6 A–E), cuspidactylate. Pereopod III ( Fig. 6A View FIGURE 6 ), coxa, wider than deep and with a posterior process; basis anteriorly reduced, with robust setae and spines on both margins; carpus 0.9 times as long as propodus. Pereopod IV ( Fig. 6B View FIGURE 6 ), smaller than pereopod III; coxa wider than deep, with a smaller posterior process than pereopod III; propodus, slightly longer than carpus; dactylus ( Fig. 6G View FIGURE 6 ), proximally enlarged along the anterior margin, and shorter than dactyla of pereopods III and V–VII. Pereopod V ( Fig. 6C View FIGURE 6 ), coxa bilobed; basis oval, with robust setae and spines on both margins; merus distally enlarged; merus and carpus subequal in length but distinctively shorter than propodus; propodus slender and long. Pereopod VI ( Fig. 6D View FIGURE 6 ), coxa posterior lobe posteroventral corner rounded; propodus slender and long with a slightly reduced distal end. Pereopod VII ( Fig. 6E View FIGURE 6 ), basis subcircular, posterior margin serrated, anterior margin with more than nine short, stout setae; merus and carpus distally expanded; carpus subquadrate; propodus, slender and longest of all the pereopods; merus, carpus, and propodus lengths in the ratio 7: 8: 12 respectively.

Pleopods I–III ( Fig. 7 View FIGURE 7 A–C), all similar in appearance, biramous and well-developed; rami subequal, with plumose setae. Pleopods I–II peduncle margins without marginal setae. Pleopod III peduncle with three marginal setae. Uropod I ( Fig. 7D View FIGURE 7 ), peduncle with four spines on outer margin and five spines on inner margin; inner ramus subequal in length to outer ramus, with four spines on outer margin, and two short and one long bifid spine apically; outer ramus without marginal spines, with four apical spines. Uropod II ( Fig. 7E View FIGURE 7 ), peduncle with three spines on outer margin and two spines on inner margin; inner ramus with two spines on inner margin and five apical spines; outer ramus with one marginal spine and three apical spines. Uropod III ( Fig. 7 View FIGURE 7 F–G), peduncle with four spines on the distal margin of lateral side; ramus 0.5 times as long as the peduncle, with two marginal bifid spines and four to five apical bifid spines.

Epimera II–III ( Fig. 7 View FIGURE 7 I–J), with vertical slits just above the ventral margins. Epimeron II ( Fig. 7I View FIGURE 7 ), with 20–22 slits. Epimeron III ( Fig. 7J View FIGURE 7 ), with 24–29 slits, posteroventral corner with a small subacute stout spine. Telson ( Fig. 7K View FIGURE 7 ), apically incised and bilobed; dorsal midline at least halfway, with two bifid marginal spines and three bifid terminal spines per lobe.

Description of female. Based on the paratype, 8.0 mm (NMK/INV/AMP/0002). Antenna I ( Fig. 8A View FIGURE 8 ), similar to that of male. Antenna II ( Fig. 8B View FIGURE 8 ), 0.3 times as long as body length; five articled peduncle; flagellum with 15 articles, 2.4 times as long as peduncle article V, final article ( Fig. 8C View FIGURE 8 ), cone-shaped, minute, and with an apical cluster of overlapping setae.

Left mandible ( Fig. 8D View FIGURE 8 ), with five dentate incisor, four cuspidate lacinia mobilis, more than five pappose setae, and a well-developed molar. Maxilla I ( Fig. 8E View FIGURE 8 ), outer plate distal margin with nine robust spines, with dentition formulae 3̅4̅4̅4̅3̅3̅4̅2̅4; one small articulate palp present. Maxilla II ( Fig. 8F View FIGURE 8 ), outer plate with 11 smoothedged, short and blunt setae and five relatively longer rugged edged setae; inner plate distal margin with more than 14 smooth-edged, short and blunt setae on the edge, five rugged edged setae on the ventral side, and one large subapical pappose seta. Maxilliped ( Fig. 8J View FIGURE 8 ), similar to that of males.

Gnathopod I ( Fig. 9 View FIGURE 9 A–B), basis sub-rectangular; merus, carpus, and propodus posterior margin without a tumescent hump; merus posterior margin with seven robust setae; propodus 0.7 times as long as carpus, palm slightly acute, anterior margin with two groups of three to four robust setae while the posterior margin with eight robust bifid setae; dactylus, cuspidactylate. Gnathopod II ( Fig. 9 View FIGURE 9 C–D), basis anteroproximally extended; merus, carpus, and propodus posterior margins modified in a tumescent hump; carpus, well developed, with one short, robust seta at the base of the tumescent hump; propodus longer than wide; dactylus cuspidate and subequal in length to the palm.

Brood plates longer than wide, with 13, 16, and 10 simple-tipped setae on distal half margins of gnathopod II, pereopods III and IV respectively. Pereopods III̅VI ( Fig. 10 View FIGURE 10 A–D), similar to those of males. Pereopod VII ( Fig. 10E View FIGURE 10 ), basis subcircular and highly incrassate. Pleopods I–III ( Fig. 11 View FIGURE 11 A–C), similar to those of males.

Uropod I ( Fig. 11D View FIGURE 11 ), peduncle with five spines on inner and outer margins, respectively; inner ramus with three marginal and four apical spines; outer ramus marginally bare, with four apical setae. Uropod II ( Fig. 11E View FIGURE 11 ), peduncle with four spines on inner and outer margins, respectively; inner ramus with two marginal and five apical spines; outer ramus with two marginal and three apical spines. Uropod III ( Fig. 11F View FIGURE 11 ), peduncle longer than wide, with five spines on the lateral side’s distal margin; ramus with two bifid marginal spines and four bifid apical spines. Epimeron II ( Fig. 11H View FIGURE 11 ), with 20–22 slits; epimeron III ( Fig. 11I View FIGURE 11 ), with 34–36 slits just above the ventral margin. Telson ( Fig. 11J View FIGURE 11 ), similar to males, with five to six spines per lobe.

The main differences between male and female are: seven dentate incisor and five cuspidate lacinia mobilis of the left mandible in male vs five dentate incisor and four cuspidate lacinia mobilis in female; sexually dimorphic gnathopods I and II; brood plates in female; incrassate pereopod VII basis only in females; 24–29 slits on epimeron III in male vs 34 in female.

Distribution. Only known from the type locality.

Remarks. Following the key by Lowry & Springthorpe (2015), F. mkomani Bichang’a & Hou, sp. nov. appears to be closely related to F. anpingensis , F. anomala , and F. yehyuensis in having: antenna I short, not exceeding half of antenna II peduncle article V; male gnathopod I posterior margins of merus, carpus, and propodus with prominent tumescent humps; gnathopod II palm reaching between 38% and 45% along the posterior margin; pereopod IV dactylus thickened proximally; uropod I outer ramus marginally bare; epimera II–III with slits above ventral margins; and telson with five robust spines per lobe. The new species can be distinguished from them by left mandible lacinia mobilis five cuspidate (vs four in F. anomala and F. yehyuensis ); male gnathopod I dactylus grasping margin bare (vs one to three spines in the three species); pereopod VII sexually dimorphic, incrassate basis in female (vs similar in male and female); 22 slits on epimera II and 29 on epimeron III (vs 27–33 on epimeron II and 19–20 on epimeron III of the three species).

Besides the outlined distinguishing characteristics, F. mkomani Bichang’a & Hou, sp. nov. female can also be distinguished from F. yehyuensis female by gnathopod II grasping margin without spines (vs three spines), uropod III peduncle with five robust marginal spines (vs two); supralittoral habitat marine environment, only exposed during low tides (vs terrestrial habitat, living among grassroots in a sugar cane near the seashore).

Due to the close morphological relationship between F. mkomani Bichang’a & Hou, sp. nov. and the three Floresorchestia species, their COI sequences were used for molecular analysis. The uncorrected p-distances between F. mkomani Bichang’a & Hou, sp. nov., the three Floresorchestia species and Gazia gazi are more than 21% ( Table 1 View TABLE 1 ), larger than the accepted threshold (16%) for crustacean species delimitation ( Hou & Li, 2010; Lefébure et al. 2006). Molecular and morphological data presented support the idea that F. mkomani Bichang’a & Hou, sp. nov., is a species new to science.