A new species of Echinolaophonte and record of E. armiger (Gurney, 1927) (Crustacea, Copepoda, Harpacticoida, Laophontidae) from the Caribbean with a key to species

Abstract A new species of the harpacticoid copepod genus Echinolaophonte is described here from specimens obtained during a biological survey of Rodadero Bay, a coastal system in the Colombian Caribbean. This species has been previously recorded as E. armiger Gurney, 1927 in different geographic areas (Indian and Pacific Oceans). The Colombian specimens recognized as E. villabonae sp. n. and true E. armiger are deemed as distinct species based on differences in several features of which the shape of the rostrum and the dorsal spinous process on the prosome are among the most distinctive. These and other characters are shared by specimens recorded as E. armiger from Caroline Islands and Australia that are now incorporated to the new species. The finding of the true E. armiger, previously known only from Egypt, the Texan coast, Brazil, and possibly Bermuda, constitutes the first record of this species in the western Caribbean and a regional range extension. A key to the identification of the 13 known species of the genus is also provided.

During a survey of the zooplankton community of Rodadero Bay, a shallow coastal system in the Colombian Caribbean, several male and female specimens of harpacticoid copepods of the genus Echinolaophonte were obtained. The taxonomic examination of these specimens revealed that some of them were assignable to the strict form of E. armiger (Gurney, 1927). Another group of individuals resemble closely E. armiger sensu Vervoort (1964) and following the opinion by Lee et al. (2006), it was realized that they represent an undescribed species of Echinolaophonte. The aim of this paper is to review the status of the records related to E. armiger sensu Vervoort (1964) and propose a species rank to this taxon by comparing it with its closest congeners based on Colombian specimens. A key to the species currently contained in the genus Echinolaophonte is also provided.

Materials and methods
Biological samples of littoral habitats were obtained from Rodadero Bay, Magdalena, northern Colombia (11°14'10"N, 74°12'06"W) during fieldwork carried out from August 2015 to March 2016, mainly at the inshore areas covered by vegetation (mangrove) and with a bank of oysters. Water salinity, pH, temperature were measured with a multiparameter WTW 350i equipment. Water samples were collected manually using a 25-l bucket at both littoral and limnetic habitats. Samples were then filtered with a plankton net (mesh size = 45 μm) and preserved in 70% ethanol. Copepods were sorted from all the samples and then processed for taxonomical identification including the examination of the whole specimen and dissection of selected appendages. Dissected appendages were mounted on slides with glycerin and sealed with Canada balsam. The specimens were measured in ventral position, from the anterior end of the rostral area to the posterior margin of the caudal rami. Drawings were made with the aid of a camera lucida mounted on an Olympus BX51 compound microscope equipped with Nomarski DIC. Some specimens were prepared for SEM examination with a JEOL LV 5900 microscope at the University of Aguascalientes, Mexico. The process included dehydration of specimens in progressively higher ethanol solutions (60, 70, 80, 96, 100 %), critical point drying, and gold coating following standard methods. The specimens examined were deposited at the Museo de Colecciones Biológicas de la Universidad del Atlántico, Barranquilla-Atlántico, Colombia (UARC) and in the Centro de Colecciones Biológicas of the Universidad del Magdalena-Colombia (CBUMAG) where they are available for consultation and/or further examination. Morphologi cal terminology follows Huys and Boxshall (1991). The following abbreviations are used in the description: P1-P6 = first to sixth legs, EXP = exopod, ENP = endopod.  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; speci mens dissected, semi-permanent slides (UARC302M-UARC315M). Non-type specimens: two adult females, one adult male in collection of first author (JMFR), one female prepared for SEM analysis, same collection data.
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, pro some 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 1B-C, 5B).
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. P6 (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 most closely resembles E. gladiator Vervoort, 1964 andE. 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.
Variability. One male was observed to have three setal elements on the antennal exopod instead of the usual pattern of four.
Remarks. The present record, from the Caribbean coast of Colombia, is the fifth of E. armiger sensu Gurney, 1927 worldwide. In the surveyed area this species coexists  with the closely related E. villabonae, which is locally more abundant. Lee et al. (2006) redescribed E. armiger from syntypic specimens from the Suez Canal and complemented their report with specimens from the Gulf of Mexico (Texan Coast, USA); the species is characterized by: 1) the smooth apical margin of the rostrum, 2) the simple dorsal spinous process on the cephalosome, 3) the armature formula of the swimming legs, 4) the short ENP2 of P2-P4, 5) the unmodified P3 endopod in male, 6) the slightly modified exopods of P3 and P4 in male, 7) the short setophore of the P5 outer basal seta, 8) short caudal ramus (only 1.4 times longer than wide), 9) the shape of dorsal spiny processes in the prosome and urosome and 10) the shape of pseudoperculum. Most of these distinctive traits were observed in the Colombian specimens. However, subtle differences were detected in our specimens from Colombia, thus allowing an expan sion of the morphological range of this species: 1) a maxillary coxal seta is present in the Colombian specimens (Fig. 7H) whereas it is absent in the Texan material (Lee et al. 2006: fig. 2F), 2) the P1ENP1 length/width ratio. It is 5.6 in the Colombian specimen (Fig. 7I) whereas in the Texas specimens the figure is slightly higher: 5.8 (Lee et al. 2006: fig. 3A).