Centropages mohamedi, El-Sherbiny, Mohsen M. & Al-Aidaroos, Ali M., 2015

El-Sherbiny, Mohsen M. & Al-Aidaroos, Ali M., 2015, A new species of Centropages (Copepoda: Calanoida: Centropagidae) from the central Red Sea based on morphological and molecular evidence, Zootaxa 3911 (3), pp. 396-410 : 397-405

Centropages mohamedi sp. nov.

(Figs 2,4–6)

Type material. Holotype. Adult female, 1.39 mm, dissected and mounted on 1 glass slide with CMC-10 (Reg. No NHMUK 2014.613-622) collected at coastal water off Obhur Creek, Jeddah, central Red Sea, (21° 41.398' N, 39° 3.002' E) on 31 May 2012, 0.5 m depth.

Allotype. Adult male, 1.20 mm, partly dissected and mounted in 1 glass slide with CMC-10 (Reg. No NHMUK 2014.623-632) collected at coastal water off Obhur Creek, Jeddah, central Red Sea (21° 41.398' N, 39° 3.002' E), on 31 May 2012, 0.5 m depth.

Additional paratypes. 20 adult females (body length: 1.31–1.45 mm, mean ± SD = 1.36 ± 0.06 mm) and 17 adult males (body length: 1.18–1.35 mm, mean ± SD = 1.26 ± 0.07 mm) in 70% alcohol (Registration number: NHMUK 2014.613-622 and NHMUK 2014.623-632 respectively) collected at coastal water off Obhur Creek, Jeddah, central Red Sea (21° 41.398' N, 39° 3.002' E), on 31 May 2012, 0.5 m depth.

Description. Female (holotype). Body ( Fig. 2 A) robust, prosome plump comprising cephalosome and five pedigerous somites; prosome about 2.3 times as long as urosome; cephalosome distinctly separated from first pediger; fourth and fifth pedigerous somites separated; fifth pedigerous somite symmetrical with posterolateral corners slightly pointed in dorsal and lateral aspects ( Fig. 2 A, B). Rostrum bearing long pair of frontal filaments directed postero-ventrally with broad base ( Figs 2 C, 3A). Urosome ( Figs 2 D–F, 3B) of 3 free somites; genital double somite symmetrical ( Figs 3 B–C); genital receptacle located half way along ventral surface covered with blunt operculum. Second urosomite symmetrical, slightly shorter than genital double somite; anal somite symmetrical and shorter than preceding free abdominal somite. Caudal rami symmetrical and approximately 2.3 times as long as wide.

Antennules ( Fig. 2 G, H) symmetrical, 24-segmented, extending about to middle of anal somite. Armature formula as follows: (segment 1) = 2 setae + aesthetasc (ae), (2) = 2 setae + ae, (3) = 2 + ae, VI (4) = 2 + ae,(5) = 2 + ae, (6) = 1 + ae, (7) = 2 + ae, (8) = 2 (1 spiniform) + ae, (9) = 2 + ae, (10) = 2 + ae, (11) =1 + ae, (12) = 2 (1 spiniform) + ae, (13) = 1 + ae, (14) = 2 + ae, (15) = 2 + ae, (16) = 2 + ae, (17) = 2 + ae, (18) = 2 + ae, (19) = 2 + ae, (20) = 1 + ae, (21) = 1, (22) = 1 + 1, (23) = 1 + 1, (24) = 5+ae.

Antenna ( Fig. 4 A) biramous with short coxa bearing plumose seta at distomedial angle; basis with 2 subequal setae on distomedially; exopod indistinctly 7-segmented with setal formula of 1, 4, 1, 1, 1, 1, 3; endopod 2- segmented, proximal segment with 2 unequal subterminal setae; distal segment bilobed, with medial (proximal) lobe bearing 8 setae, and with lateral (distal) lobe crowned with 7 setae and transverse row of long spinules subdistally on lateral margin.

Mandibular gnathobase ( Fig. 4 B) with cutting edge carrying 8 teeth on coxal cutting edge and dorsal spinulose seta; ventralmost tooth largest, smooth and unicuspid, third to sixth teeth bicuspidate and third to seventh teeth ornamented with 2 rows of short spinules anterodistally at base. Palp ( Fig. 4 C) basis with 4 unequal setae on medial margin; exopod 5-segmented with setal formula of 1, 1, 1, 1, 2; endopod 2-segmented, proximal segment with 4 setae at distomedial corner; distal segment with 8 unequal setae and subapical random patch of spinules row of fine spinules.

Maxillule ( Fig. 4 D) with praecoxal arthrite bearing 9 marginal strong spines plus four on posterior surface. Coxal epipodite with 9 setae; coxal endite with 3 spinulose setae; basal exite with 1 vestigial seta. Basis fused to exopod and endopod; proximal basal endite armed with 4 setae and on distal endite 7 setae. Exopod carrying 11 marginal setae; endopod indistinctly 2-segmented with 4 and 5 setae respectively.

Maxilla ( Fig. 4 E) indistinctly 7-segmented, containing partially coalesced praecoxa and coxa, basis and 2- segmented endopod. Praecoxal and coxal endites carrying 5, 3, 3 and 3 bilaterally spinulate setae respectively; basal endite with 4 setae, one longer than others; endopod 2-segmented, carrying 7 bilaterally spinulate setae.

Maxilliped ( Fig. 4 F) 8-segmented comprising syncoxa, basoendopod and free 6-segmented endopod (first endopodal segment almost completely incorporated into basis). Syncoxal lobes with 1, 2, 3, 4 setae on its medial margin, small patch of spinules on medial surface proximal to seta of first syncoxal lobe and other patch near the third lobe. Basis slightly shorter than syncoxa, with 3 setae (middle seta with proximal setule located in spiral pattern, Fig. 3 D), row of strong spinules and long hairs along medial margin of segment proximal to basal setae; endopod with setal formula of 2, 4, 4, 3, 3 + 1, 1+2+ 1.

Swimming legs 1–4 ( Fig. 5 A–D) with 3 segmented exopod; endopod 2-segmented in legs 1–3, and 3- segmented in legs 4–5. Leg 1 with medial basal seta reaching to end of proximal endopodal segment. Leg 5 ( Fig. 5 E–H) symmetrical; second exopodal segment with strong medial process medially, slightly longer than segment itself with bilateral serration along distal half of lateral margin ( Figs 5 F–G, 3E–F). Armature of legs as follows: Coxa Basis Exopod Endopod

1 2 3 1 2 3 Leg 1 0-1 0-1 I-1; I-1; II, I, 4 0-3; 1, 2, 3 Leg 2 0-1 0-0 I-1; I-1; III, I, 5 0-3; 2, 2, 4 Leg 3 0-1 0-0 I-1; I-1; III, I, 5 0-3; 2, 2, 4 Leg 4 0-1 0-0 I-1; I-1; III, I, 5 0-1; 0-2; 2, 2, 3 Leg 5 (F) 0-0 0-0 I-0; I-0; II, I, 4 0-1; 0-1; 2, 2, 2 Male (allotype). Body ( Fig. 6 A) robust, prosome plump, widest at posterior border of second pediger; prosome about 2.2 times as long as urosome comprising cephalosome and five pedigerous somites; cephalosome distinctly separated from first pediger; fifth pedigerous somite produced into slightly pointed and slightly asymmetrical corners, extending posteriorly slightly further on left side ( Fig. 6 A). Rostrum bearing long pair of frontal filaments sinuate at distal part and terminally directed postero-ventrally ( Figs 6 B, 7A). Urosome ( Fig. 6 C) comprising 4 free somites, symmetrical except for genital somite with single gonopore opening posterolaterally on left side ventral surface; anal somite slightly shorter than 2 preceding free somites. Caudal rami ( Fig. 6 C) symmetrical, about 2.3 times longer than wide.

Right antennule ( Fig. 6 D) 21-segmented, geniculate between segments XX and XXI (18 and 19). Ancestral segments XIX (17) and XX (18) with row of spinules produced from anterior margin respectively; segment XXI (19) with row of relatively longer spinules on proximal 1/3 terminating in long spine along segment margin. Armature as follows: (1) = 2 + ae, (2) = 2+ ae, (3) = 2 + ae, (4) = 2 + ae, (5) = 2 + ae, (6) = 2 + ae, (7) = 2 + ae, (8) = 1 + ae, (9) = 2 + ae, (10) = 2 (1 spiniform) + ae, (11) = 1 + ae, (12) = 2 (1 spiniform) + ae, (13) = 2 + ae, (14) = 2 + ae, (15) = 2 + ae, (16) = 2 + ae, (17) = 1 + ae, XX (18) = 1 + ae, (19) = 1 + process + ae, (20) = 2+ 2, (21) = 6 + ae.

Mouthpart appendages, legs 1 to 3 similar to those in female. Leg 4 asymmetrical, basis of right leg with three rounded digitiform processes spreading along lateral surface, proximal and middle ones originated from same base (proximal one smaller) ( Figs 6 E–F, 7B); these digitiform processes outlined with papilla-like structures ( Fig. 7 B).

Leg 5 ( Fig. 6 G) strongly asymmetrical; first endopodal segment of both legs produced distolaterally into rounded process. Left leg biramous, with 2-segmented heavily sclerotised exopod and 3-segmented endopod; second exopodal segment nearly 2.3 times as long as first one, hirsute on posteromedial surface, bearing 2 lateral spines, one medial pointed process and bilaterally serrated, long distal spine fused to segment ( Fig. 7 C). Right leg ( Fig. 6 G) biramous, with broader basis than that of left leg; exopod 3-segmented; first exopodal segment short, with lateral articulated spine and adjacent pointed process distolaterally; second exopodal segment with short spine very near distolateral corner and with strongly-curved inner process originating at nearly 90 degree proximally on to medial margin; third exopodal segment long, curved inward, serrated along outer convex margin ( Figs 6 G, 7D), armed with slender seta on proximomedial margin and recurved distally; endopod exceeding second exopodal segment, second endopodal segment with pointed distolateral process. Setal formula of right endopod same as left endopod (0-1; 0-1; 2-2-2); right endopod slightly wider than left one.

Molecular diversity. A 544-bp region of the mtCOI was obtained for three individuals of C. mohamedi (GenBank accession Nos. KM288701 - KM288703 ) collected from the coastal water off Obhur Creek, central Red Sea and four individuals of C. orsinii collected from Obhur Creek (GenBank accession Nos. KM288704 - KM288707 ). Individuals from the same species have identical mtCOI sequences (0.000), while individuals of different species differed by 20.8 % ( Table 1 ). The mtCOI gene tree also showed that C. mohamedi is clearly an undescribed species separate from C. orsinii ( Fig. 8 ).

Etymology. The specific name mohamedi is dedicated to the first author’s son (Mohamed) who passed away on May 2009 at 5 years old.

Figures

FIGURE 2. Centropages mohamedi sp. nov. Female (holotype). (A) Habitus, dorsal view; (B) Habitus, lateral view; (C) Rostrum, lateral view; (D) Urosome, dorsal view; (E) Urosome, ventral view; (F) Urosome, lateral view; (G – H) Antennule. Scale bars in mm.

FIGURE 3. SEM micrographs of Centropages mohamedi sp. nov. female. (A) Rostrum, lateral view; (B) Urosome, lateral view; (C) Genital double somite, lateral view, (D) Maxillipod basis (middle seta with proximal, spirally located spinule indicated by arrow), lateral view; (E) Medial process of second exopodal segment of female leg 5 indicated by arrow; (F) Enlarged medial process of second expodal segment of female leg 5.

FIGURE 4. Centropages mohamedi sp. nov. Female (holotype). (A) Antenna; (B) Mandibular gnathobase; (C) Mandibular palp; (D) Maxillule; (E) Maxilla, (F) Maxilliped. Scale bars in mm.

FIGURE 5. Centropages mohamedi sp. nov. Female (holotype). (A) Leg 1; (B) Leg 2; (C) Leg 3; (D) Leg 4; (E) Leg 5; (F) Endopod of left leg 5; (G) Left medial process of second exopodal segment of female leg 5; (H) Right medial process of second exopodal segment of female leg 5. Scale bars in mm.

FIGURE 6. Centropages mohamedi sp. nov. Male (allotype). (A) Habitus, dorsal view; (B) Rostrum, ventro-lateral view; (C) Urosome, dorsal view; (D) Right antennule; (E) Right leg 4; (F) Basis of right leg 4, posterior view; (G) Leg 5, posterior view. Scale bars in mm.

FIGURE 7. SEM micrograph of Centropages mohamedi sp. nov. male from the Red Sea. (A) Rostrum, ventral view; (B) Basis of right leg 4, posterior view; (C) Fused exopodal segments 2 and 3 of male left leg 5; (D) Third exopodal segment of male right leg 5 (serration of distal part indicated by arrow).

FIGURE 8. Gene tree for mtCOI showing proportional differences between individual females of Centropages mohamedi sp. nov. and C. orsinii from neritic waters of the central Red Sea. Numbers at branch points are bootstrap values (i. e., percentage of trees with that branch point among 1000 subreplicates). The specimen numbers correspond to those in Table 1.