Echinolaophonte villabonae, Fuentes-Reines, Juan Manuel & Suarez-Morales, Eduardo, 2017

Fuentes-Reines, Juan Manuel & Suarez-Morales, Eduardo, 2017, A new species of Echinolaophonte and record of E. armiger (Gurney, 1927) (Crustacea, Copepoda, Harpacticoida, Laophontidae) from the Caribbean with a key to species, ZooKeys 722, pp. 19-36 : 20-26

Echinolaophonte villabonae sp. n. Figs 1, 2, 3, 4, 5, 6A, B

Syn.: Echinolaophonte armiger Nicholls, 1945; Echinolaophonte armiger Vervoort, 1964.

Material examined.

Adult female holotype (UARC290M), male allotype (UARC291M), Rodadero Bay, Magdalena, Colombia, coll. J. Fuentes-Reinés, August-June 2016. Paratypes: five females (UARC292M) and two males (UARC293M) from same locality, coll. Juan M. Fuentes-Reinés. Two adult females, two adult males from same locality, date, and collector; specimens dissected, semi-permanent slides (UARC302 M–UARC 315M). Non-type specimens: two adult females, one adult male in collection of first author (JMFR), one female prepared for SEM analysis, same collection data.

Type locality.

Rodadero Bay, Magdalena, northern Colombia (11°14'10"N, 74°12'06"W).

Diagnosis.

Body cylindrical, rostrum wide, subrectangular, medially flat, posterior margin of cephalic shield with strong dorsal spiniform which possess two notches. Female antennule six-segmented; male antennule subchirocer, seven-segmented. Antenna three-segmented, EXP one-segmented with four strong setae, inner longest. Mandible ENP and EXP reduced, with three and one short pinnate setae, respectively. Maxillule with well-developed arthrite and eight distal elements; EXP one-segmented, with two apical setae. Maxilliped three-segmented, endopodal claw with single seta. P1-P4ENP and EXP being two and three-segmented, respectively, but P1EXP two-segmented. P1ENP 7.5 times as long as wide. Female and male P5 with long setophore and apical seta, female P5 EXP and ENP with three and four setae, respectively, male P5EXP with three setae. Female and male caudal rami with seven setae.

Description.

Female. Habitus as in Figure 1A. Body cylindrical in dorsal view, prosome gradually tapering anteriorly. Total body length measured from anterior margin of rostrum to posterior margin of caudal rami ranging from 560 to 616μm (average = 586.7 μm, n = 11; holotype: 588 μm). Strong dorsal spiniform process present at median posterior margin of cephalic shield (Figs 1A, 5A) and reaching middle of second pedigerous somite. Process with two distinctive notches on posterior margin, distal end represented by curved point (Figs 1 B–C, 5B).

Cephalothorax with smooth posterior margin; lateral posterior corners of cephalic shield produced into triangular expansions (Fig. 1D) and intricate cuticular ornamentation (Fig. 5B, C). Urosome five-segmented, in lateral view urosomites 3-5 with strong expansion, cuticular surface ornamented with minute denticles, posterior margins spinulate (Figs 1A, 5D). Genital double-somite (Fig. 1G, H) with transverse, shallow suture on ventral surface, indicating original intersomite segmentation; dorsal surface with ornamentation as in figure 1E, including a field of minute spinules on proximal dorsal surface (arrowed). Genital pore inconspicuous, located medially on anteriormost end of somite (Fig. 1H). Some specimens carrying single egg sac ventrally; egg mass set close to ventral surface of genital and postgenital somites (Fig. 1A). Postgenital somite relatively narrow, with large dorsal spiniform process in lateral view (Fig. 5G); with medial expansions visible in dorsal view (Fig. 1F); surface with cuticular reticulation. Posterior margin ornamented with row of short setules and ventral rows of spinules (Fig. 5G). Succeeding preanal somite lacking large dorsal spiniform process but with posterodorsal expansions visible in dorsal view (Fig. 1E); distal margin of somite and posterolateral surface furnished with spinules and reticulate cuticular surface (Figs 1E, 5G). Anal somite tapering posteriorly, with row of minute spinules on posterior margins (Fig. 5G).

Caudal rami 1.4-1.9 times longer than wide; each ramus with seven setae: setae I–III bare, first one shortest, setae IV and V pinnate, fused at base, seta VI approximately half-length of seta IV, seta VII articulated (Fig. 2I, arrow in Fig. 5G). Rostrum wide, subrectangular, medially flat (Fig. 2B), with rounded protuberance on each end of distal margin (arrows in Fig. 2B), and pair of sensilla. Antennule (Fig. 6A) and antenna (Figs 2A, C, D, 5E, F) as in E. armiger sensu Vervoort (1964) (Lee et al. 2016).

Mandible (Fig. 2E) gnathal blade with several multicuspid teeth plus pinnate dorsal seta, dorsal margin with subdistal rounded protuberance. Palp with small basal seta; endopod and exopod reduced, represented by expansions armed with three and one short pinnate setae, respectively.

Maxillule (Fig. 2G). Precoxal arthrite with eight distal spines/setae. Subdistal row of small spinules on inner margin of arthrite. Coxa with cylindrical endite bearing stout smooth seta and curved, distally uniserially pinnate spine. Basal endite cylindrical, armed with two naked setae and pinnate spine. Endopod incorporated in basis, forming small peduncle with two naked slender setae. Exopod one-segmented, with two apical setae.

Maxilla (Fig. 2F) comprising syncoxa with two endites furnished with spinules along outer margin plus short inner distal seta. Coxal endites each with three pinnate spines. Allobasis transformed into strong, slightly curved, distally pinnate claw. Endopod represented by two setae.

Maxilliped (Figs 2H, 6B) represented by cylindrical syncoxa armed with two distal plumose setae with rows of slender hair-like elements at insertion of setae. Basis nearly twice as thick as syncoxa, widest at midlength, ornamented with comb of spinules on proximal 1/3 (arrowed in Fig. 6B), medial field of scattered spinules, and distal rows of slender setae. Endopod forming long curved claw with short setulated seta at base.

P 1 (Fig. 3A, G). Coxa ornamented with rows of spinules on inner and outer margins, as figured. Protuberant tube pore on subdistal medial position. Basis with single slender seta on proximal 1/3 of segment, segment furnished with spinules on inner and outer margins. EXP short, two-segmented, EXP1 with one outer seta, EXP2 with five setae, two apical. ENP1 7.5 times as long as wide, ENP2 short, 2.1 long as wide with strong, denticulate apical claw and small, naked seta at base. EXP short, ¼ the length of ENP1.

P2 (Fig. 3B). Coxa and basis ornamented as figured. Basis with stout outer basipodal seta. EXP three-segmented, longer than endopod; EXP1 lacking inner seta, EXP 2 with inner seta. ENP1 lacking inner seta, ENP2 four times as long as wide with one inner and two apical elements. ENP reaching halflength of EXP3.

P3 (Fig. 3C). Coxa and basis ornamented as figured. Basis with outer basal seta. EXP three-segmented. EXP1 without inner seta, EXP2 with inner seta. ENP two-segmented, ENP1 lacking inner seta, second segment almost five times as long as wide with two inner and two apical elements. ENP barely reaching beyond distal margin of EXP2.

P4 (Fig. 3D) Coxa and basis ornamented as figured. Basis with outer basipodal seta. Exopodal ramus three-segmented. EXP1 without inner seta, EXP2 with inner seta. ENP two-segmented, ENP1 lacking inner seta, ENP2 segment almost four times as long as wide with one inner and two apical elements. ENP short, not reaching distal margin of EXP1. Spine/ setal formula of P2-P4 as follows:

P5 (Fig. 3E). EXP and baseoendopod covered with small spinules as figured. Baseoendopod with long outer setophore armed with single apical seta. Endopodal lobe not reaching distal margin of exopod, with one apical and three lateral, pinnate setae. EXP elongate, twice as long as wide, with three pinnate setae.

P6 (Fig. 3F). Represented by two setae, a short inner one, and a longer outer one.

Male. Habitus resembling that of female but somewhat smaller. Total body length measured from anterior margin of rostrum to posterior margin of caudal rami ranging from 476 to 508 μm (average = 478 μm, n = 7; holotype: 476 μm).Cephalosome with strong dorsal spiniform at median posterior margin of cephalic shield as in female (Fig. 4B). Antennule (Fig. 4A) subchirocer, seven-segmented, geniculation between fourth and fifth segments. First segment with row of spinules, second segment with small subdistal knob. Fourth segment swollen; fifth segment with spiniform processes. Seventh segment with triangular expansion on distal half.

Antenna, mandible, maxillule, and maxilla as in female. Maxilliped as in female (Fig. 4C) except for narrower basis and relatively longer claw. P1 and P2 as in female (not illustrated). P3 (Fig. 4D) as in female except for outer spines on EXP1-3, slightly stronger than in female.

P4 (Fig. 4E) as in female except for EXP3 and outer spine on EXP1-2, narrower and slightly stronger, respectively, than in female.

P5 (Fig. 4F) clearly separated at base. Baseoendopod with long setophore bearing apical seta. Exopod slightly longer than maximum width, with three pinnate setae and row of spinules on anterior surface.

P 6 (Fig. 4G) represented by one bipinnate inner and one naked outer seta. Outer seta arising from setophore.

Caudal rami 1.5-1.6 times as long as wide (Fig. 4H).

Etymology.

The species is named after Dr. Silvia Lucía Villabona-González, for her intense research on the zooplankton communities of Colombia and for her legacy and leadership of new generations of planktologists in this country.

Remarks.

The genus Echinolaophonte was divided by Lang (1965) into two lineages, the first one is characterized by its possession of 3, 3, 2 outer spines on P2-P4 EXP3, respectively, and the male P3ENP is transformed, with an apophysis in the second segment. The second lineage shows 2, 3, 2 outer spines on P2-P4 EXP3, respectively, and the male P3ENP is not modified; it lacks an apophysis on the second segment, as in the female. Most species can be accommodated in these two lineages but E. minuta has a mixture of such characters and could fit in both groups (spinal formula 2, 3, 2, and male P3ENP2 with apophysis); a similar situation is true for E. tetracheir Mielke, 1981. Two species do not match the characters of any of these linages: E. gladiator (Vervoort, 1964) and E. mirabilis (Gurney, 1927). They have an outer spine formula of 2, 2, 2 and 3, 3, 3, respectively; males of both species remain unknown. The new species, E. villabonae shares the same set of lineage characters with E. gladiator ; therefore, this division should be reevaluated or expanded.

The redescription of E. armiger based on type material from the Suez Canal, Egypt supported the notion that only a few of the previous records of E. armiger sensu Gurney (1927) actually correspond to this species ( Lee et al. 2006). One of these uncertain records of E. armiger is that provided by Vervoort (1964); these specimens differ from the "true E. armiger (Gurney, 1927)" in several characters as previously outlined by Lee et al. (2006) who suggested that Vervoort’s (1964) specimens represent an undescribed species. They also recognized that Nicholl’s (1945) Australian record of E. armiger is assignable to E. armiger sensu Vervoort (1964). However, the specific identity of these two groups of specimens was not established because of the difficulty to observe and confirm key characters in the preserved specimens and by the low number of individuals available for examination. The recent finding of a large number of specimens of E. cf. armiger in plankton samples from Rodadero Bay, Colombia, which are almost identical to those reported as E. armiger sensu Vervoort, 1964 from Port Denison (Australia) ( Nicholls 1945) and Caroline Islands ( Vervoort 1964), motivated a wider analysis of this problem in order to determine and establish the true identity of these specimens. As a result, a new species of Echinolaophonte is erected based on the Colombian specimens after comparing them with Gurney’s true E. armiger (Gurney, 1927).

The new species, Echinolaophonte villabonae sp. n. can be distinguished from E. armiger Gurney, 1927 by several characters:1) the rostrum has two protuberances in its anterior margin in E. villabonae (Fig. 2B) whereas it is flat in E. armiger (Fig. 7B, Lee et al. 2006, fig. 1A) 2) the maxilla bears a small inner coxal seta in E. villabonae (Fig. 2F) whereas this seta is absent in E. armiger from the type locality ( Lee et al. 2006, fig. 2F), but it was observed in the Colombian material (arrow in Fig. 7H; 3) the maxillipedal base has a spinule comb in the proximal 1/3 in E. villabonae (Fig. 2H) whereas this comb is medial or subdistal in E. armiger (Fig. 6C, Lee et al. 2006, fig. 2C); in both species male maxillipeds are slenderer than in the female (Figs 4C, 6D); 4) the shape of the dorsal spinous process has two distinctive notches on the dorsal margin in E. villabonae (visible in lateral view, Figs 1B, C, 5B) whereas in E. armiger the same structure is smooth (Fig. 7A, C, Lee et al. 2006, fig. 1B); 5) the length/width ratio of P1ENP1 is 7-7.5 in E. villabonae (Vervoort, 1964, fig. 143a, as Onychocamptus armiger , Fig. 3A, G) vs. 5.6-5.8 in E. armiger (fig. 7I, Lee et al. 2006, fig. 3A); 6) the length/width ratio of P2-P4ENP2 is 6.25, 6.0,and 2.5, respectively in E. villabonae sp. n. vs. 3.9, 5.8, and 3.8 in E. armiger ; 7) in E. armiger the distal margin of P4ENP reaches beyond the point of insertion of the outer spine of the elongate P4EXP1( Lee et al. 2006, fig. 4B) whereas in E. villabonae the endopod is clearly shorter and does not reach this level (Fig. 3D); 8) the number of setal elements on P3EXP3 also differs between these two species: it has 6 in E. villabonae ( Vervoort 1964, fig. 143C, as O. armiger ; Fig. 3C) vs. 7 in E. armiger ( Lee et al. 2006, fig. 4A); 9) the setophore of the P5 outer basal seta is relatively longer in E. villabonae (Fig. 3E) than in E. armiger ( Lee et al. 2006, fig. 3C); 10) the dorsal ornamentation of the urosome is clearly stronger in E. villabonae (Figs 1 E–G, 5G) than in E. armiger ( Lee et al. 2006, figs 1B, 5B). The male of E. villabonae sp. n. shows some additional differences with respect to E. armiger : 1) the antennule is 7-segmented in E. villabonae (Fig. 4A) vs. 8-segmented in E. armiger ( Lee et al. 2006, fig. 6B); 2) the caudal rami ratio is 1.5-1.6 in E. villabonae (Fig. 4H) vs. 1.4 in E. armiger ( Lee et al. 2006, fig. 6A). The erection of this new taxon and the comparisons with the other related records of this species allows us to allocate all previous records of Echinolaophonte armiger sensu Vervoort (1964) in the Indian and Pacific Ocean as belonging to the new species, E. villabonae .

The new species most closely resembles E. gladiator Vervoort, 1964 and E. tropica Ummerkutty, 1970. They share an identical armature formula of P1-P4. The female fifth leg armature, with 3 and 4 setal elements on the fifth leg EXP and ENP, respectively also resembles the pattern found in E. gladiator ( Vervoort 1964, fig. 145e), and E. tropica ( Ummerkutty 1970, fig. 3O; Wells and Rao 1987, fig.145a). However, E. villabonae can be separated from these species when comparing the length/width ratio of P1ENP which is 4.4 in E. tropica ( Wells and Rao 1987, fig. 144c), 5.8 in E. gladiator ( Vervoort 1964, fig. 145a) and 7.5in E. villabonae (Fig. 3A). Also, the length of P4ENP with respect to the elongate P4EXP1 is different in these species: in E. tropica ( Wells and Rao 1987: fig. 144f) and E. gladiator ( Vervoort 1964, fig. 145d), the endopod reaches the point of insertion of the outer spine of the first exopodal segment, whereas in E. villabonae the endopod is clearly shorter and does not reach this level (Fig. 4E). The structure of the dorsal spinous process reveals additional differences: in E. villabonae (Figs 1B, C, 5B; Vervoort 1964: fig. 142b) and E. gladiator ( Vervoort 1964: fig. 144c) a conspicuous process is present, being much longer and with two notches in the former whereas in E. gladiator the structure is clearly smaller and lacks such processes; this process is absent in E. tropica ( Ummerkutty 1970: fig. 3B; Wells and Rao 1987: fig. 142d). We consider that the evidence presented justifies the separation of a new species of Echinolaophonte ; it comprises previous records of E. armiger by Nicholls (1945) and Vervoort (1964) and raises the number of known nominal species to 13.

Distribution and habitat.

This species is known to be associated mainly with coral reef areas. It has been reported (as E. armiger ) from the reef area at Port Denison, Australia ( Nicholls 1945) and also from the Ifaluk Atoll, Caroline Islands in the Pacific ( Vervoort 1964). In Colombia this species was found in the littoral zone of the Rodadero Bay in an area covered by mangrove with a small adjacent bank of oysters at a depth of 0.70 m and a water temperature ranging between 30 and 32 °C, salinity 36.1 psu, pH 8.3. Its finding in the Northwestern Atlantic Ocean suggests that it is widely distributed in tropical latitudes.