Tanaella quintanai, a new deep-water tanaellid (Crustacea: Peracarida: Tanaidacea) from the Colombian Caribbean Coast, with a key to the species of the genus Tanaella Norman & Stebbing, 1886

A new tanaidacean, Tanaella quintanai sp. nov., is described based on specimens collected from depths of 1,598 to 2,853 m during 2014–2015. The new species appears to be most closely related to the western Atlantic species, T. kroyeri and T. mclellandi. Tanaella quintanai can be separated from the two former, as well as from the other members of the genus by a combination of characters, including (1) a labium with apical lobe bearing one blunt seta (2) a cheliped with the inner margin of the dactylus bearing a sub-proximal bipinnate seta, (3) pereopods 1−3 with basis having sub-dorsoproximal and sub-ventroproximal margins setulose, (4) pereopods 4−6 with basis having ventroproximal margin setulose, (5) pereopods 4−6 with unguis bearing two parallel rows of small setules, and (6) a pleotelson as long as pleonites 1–5 combined. A key separating the currently recognized species of Tanaella is presented.


INTRODUCTION
The Tanaidacean fauna from Colombia has received minimal attention thus far. Recently, Morales-Núñez & Ardila (2018) reported the first record for the family Tanaellidae Larsen & Wilson, 2002 in the Colombian Caribbean region. In addition, Morales-Núñez, Morales-Ruiz & Ardila (2017) described a new sphyrapodid tanaidacean, Sphyrapus caribensis Morales-Núñez, Morales-Ruiz & Ardila, 2017, reported Kudinopasternakia siegi (Viskup & Heard, 1989, and presented detailed information about the species of tanaidaceans that had been previously reported in the Caribbean and Pacific Colombian coasts.
This publication is the second in a series dealing with the Tanaidacea from the Colombian Caribbean region, and it presents a description of a new species of Tanaella Norman & Stebbing, 1886.

MATERIALS & METHODS
Specimens were collected using a box corer of 0.25 m 2 during cruises, aboard the R/V Proteus and R/V Don Rodrigo-B, working off the southwestern Caribbean Sea of Colombia at depths of 1,598-2,821 m ( Fig. 1). Tanaidaceans were sorted, fixed in 6% formalin, and subsequently stored in 70% ethanol. Collection permits were granted by the National Authority of Environmental Licenses-ANLA (FSD, ANLA No. 0723 de 2012; FND, ANLA 1016 de 2012; PAC, ANLA No. 0880 de 2014).
Specimens were dissected under an Olympus SXZ-16 stereomicroscope. Appendages were mounted on glass slides in glycerine and observed with an Olympus BX41 microscope, and drawings were made with a camera lucida. Illustrations were prepared with Adobe Illustrator CC (2019) and figures with Photoshop CC (2019). Photographs were taken using an Olympus DP73 digital camera mounted on a stereomicroscope and all specimens were measured with CellSens Dimension 1.11 Imaging Software (Olympus). Maps were created using ArcGIS 10.4.1 software (University of Maryland Eastern Shore (UMES)).
All specimens of Tanaella sp. were measured and classified into two life-stages categories ( Table 1).
Type material has been deposited in the ''Centro de Colecciones Biológicas, Universidad del Magdalena (CBUMAG)'', Santa Marta, Colombia. All measurements were taken in millimeters (mm). Total body length was measured from the tip of the rostrum to the tip of the pleotelson. Terminology generally follows that of Larsen (2003); however, the term ''PSS'' is here applied for delicate plumose sensory setae found on antennules, antennae, pereopods and uropods (Bird, 2011).
Etymology. Named in honor of renowned Colombian racing cyclist Nairo Alexander Quintana Rojas, in recognition and appreciation for his outstanding effort and dedication, as well as for bringing pride and happiness to the Colombian nation.
Pleotelson ( Figs. 2A-2B). About 13% of TL, sub-equal length that of pleonites 1-5 combined, asetose; apex rounded. Antennule (Figs. 3A-3B). Slightly shorter than cephalothorax, with four articles. Article-1 longer than combined length of articles 2-4, about three times as long as wide; ventral margin with sub-distal very finely bipinnate seta (Fig. 3B); dorsal proximal margin with setules; inner ventral margin with two (one horizontal and one oblique) sub-distal rows (six and three, respectively) of PSS. Article-2 about 1.8 times as long as wide; ventral margin with sub-distal long very finely bipinnate seta; inner ventral margin with sub-distal oblique row of four PSS. Article-3 about five times wider than long; distoventral margin setulose; mid margin with very finely bipinnate seta; sub-distal dorsal margin with very finely bipinnate seta. Article-4 length almost half of article-2, about 2.5 times as long as wide; distal margin with five (i.e., four simple, possibly very finely bipinnate, and one very finely bipinnate) setae of unequal lengths; sub-distal dorsal margin with simple seta. Antenna (Fig. 3C). With five articles (article-3 with fusion line). Article-1 broader than following articles; outer mid distal margin with simple seta; anterior dorsal half margin with several rows of setules and distodorsal very finely bipinnate seta; inner mid ventral margin with oblique of setules. Article-2 shorter than article-1, sub-quadrate, with distodorsal very finely bipinnate seta. Article-3 longer than other articles, with clear fusion line; distoventral margin with one small simple seta and two long very finely bipinnate setae; mid sub-distal outer margin with simple seta; posterior dorsal half margin with several rows of setules; inner margin with one mid PSS and distal oblique row of three PSS. Article-4 longer than article-2, about 2.4 times as long as wide; inner distal margin with mid long very finely bipinnate seta. Article-5 minute, with distal margin bearing four (i.e., three simple (possibly very finely bipinnate) and one very finely bipinnate) setae of unequal lengths.
Maxilliped (Figs. 4D-4E). Basis fused, setose, each with very finely bipinnate seta near palp insertion. Endites with distal process and two pairs of very finely bipinnate setae of unequal lengths; outer margin with oblique row of setules (Fig. 4E). Palp article-1 with several rows of setules; article-2 with several rows of setules, inner distal margin with two simple setae and one very finely bipinnate seta (Fig. 4D), outer margin with simple seta; article-3 with inner margin having four setae (two very finely bipinnate and two simple) of unequal lengths (Fig. 4D), mid margin with oblique row of setules, outer margin with several rows of setulate; article-4 with distal margin bearing four setae (two very finely bipinnate and two simple) (Fig. 4D), mid margin with sub-distal simple seta and oblique row of setules (Fig. 4D), outer margin with sub-distal simple seta (Fig. 4D).
Epignath. Not recovered. Cheliped (Figs. 5A-5F). Basis length subequal to carpus, about 1.7 times as long as wide, posterior lobe larger than anterior mass, with sub-distal dorsal seta on outer margin (Fig. 5A). Merus triangular with simple seta on mid ventral margin. Carpus about 1.4 times as long as wide; mid ventral margin with two simple setae; dorsal margin with two (one proximal and one distal) small simple setae. Propodus as long as wide, with distodorsal simple seta (Fig. 5B), palm 1.4 times longer than fixed finger, outer margin with simple seta near to insertion of dactylus, inner face with five bipinnate setae (one distinctly longest) near to articulation of dactylus (Figs. 5E-5F); fixed finger with two ventral setae, with three sub-marginal simple setae on outer incisive margin, cutting edge with proximal serrated depression (Figs. 5A-5C) and five (three rounded and two sharp) denticles (Fig. 5C), claw short. Dactylus and unguis curving downward; ventral margin with two small blade-like pectinate setae (Fig. 5D); inner face with bipinnate seta on sub-proximal margin (Fig. 5E).
Pereopod-1 (Figs. 6A-6C). Coxa with simple seta on anterodistal margin. Basis as long as combined length of ischium, merus, carpus, and half of propodus, about six times as long as wide; sub-ventroproximal margin setulose; sub-dorsoproximal margin setulose with one PSS. Ischium wider than long, with one simple seta on ventral margin. Merus slightly shorter than carpus, about 2.2 time as long as wide; distoventral margin with bipinnate seta (Fig. 6B); inner margin with sub-distal simple seta. Carpus about two times as long as wide; distoventral margin with bipinnate seta; distodorsal margin with bipinnate seta, inner margin with mid sub-distal bipinnate seta. Propodus about four times as long as wide; ventral margin with two (one on inner view (Fig. 6C)) rows of spinules and one distal spiniform seta (possibly bipinnate); dorsal margin with a row of setules (Fig. 6A) and distally with spine-like apophysis; inner face with sub-distal dorsal simple seta and distally setose (Fig. 6C). Dactylus together with unguis shorter than propodus; dactylus slightly longer than unguis.
Pleopods. Absent. Uropod (Figs. 2B-7E). Shorter than pleotelson (Fig. 2B). Basal article less than half length of endopod, about 1.3 times as long as wide, with two (one long and one short) distal simple setae on outer margin. Exopod vestigial, indicated by two simple setae. Endopod one-articled, about five times as long as wide, with four (two sub-distal and two distal) PSS, with two sub-distal and two distal simple setae of unequal lengths.

Size-distribution
The body sizes of Tanaella quintanai individuals were measured and presented in Table 1.

Color in alcohol
Upon being preserved in 70% ethanol for more than four years, the four non-ovigerous females (Figs. 8, 9A-9B) presented a yellowish-orange coloration (intensity can vary) on some parts of the habitus and appendages as follows: (1)

Ecological notes
Specimens of T. quintanai sp. nov. (Figs. 8 and 9) were collected from muddy bottoms with a content of mud and clay between 94 and 98%. Other physicochemical parameters of the surrounding waters were a temperature of 4.1-4.4 • C, salinity of 35 ppm, pH of 7.7-8.0, and DO of 4.7-6.8 mg/L.

DISCUSSION
With the description of new Colombian species, seven of 18 species of Tanaella (Table 2) are known to be from the western Atlantic Ocean; among them, Tanaella ochracea from the western tip of Greenland, three (T. busteri, T. mclellandi, and T. prolixcauda) from Gulf of Mexico, T. kroyeri from off Brazil, T. unisetosa from the tip of Argentina, and T. quintanai sp. nov., which represents the first species of the genus described from the Caribbean (Fig. 10). During an earlier study by Morales-Núñez & Ardila (2018), it was first reported as Tanaella sp. in Caribbean waters, establishing the presence of the Family Tanaellidae in deep-waters off the Colombian Coast. Sixteen out of eighteen of the described species of Tanaella have included at least a female, with only two species been described as males: T. busteri and T. prolixcauda. The new species from the Caribbean differs from T. busteri and T. prolixcauda by having (1) labium with apical lobe having a blunt seta (absent in busteri and prolixcauda) (Table 3), (2) cheliped with dactylus having a sub-proximal bipinnate seta on inner face (absent in busteri and prolixcauda) (Table 3), (3) pereopods 1-3 with basis having sub-dorsoproximal and sub-ventroproximal margins setulose (lacking setulose margins in busteri and prolixcauda) (Table 3), (4) pleotelson as long as pleonites 1-5 combined (shorter in busteri and prolixcauda) (Tables 1 and 3), and (5) uropod shorter than pleotelson (longer in busteri and prolixcauda) ( Table 3).
Full-size DOI: 10.7717/peerj.7571/fig-10 Aside from the features indicated above, which were utilized to separate Tanaella quintanai from his congeners, Tanaella quintanai appears to be similar to T. unisetosa by having a maxilliped basis setose (Table 3), and also seems to be similar to T. forcifera by having the cheliped basis with sub-distal simple seta on dorsal margin (Table 3). Although it might be possible that these two characters have been overlooked and were not mentioned on the original descriptions and re-descriptions (Larsen & Heard, 2004) along the other members (i.e., 15 species) of the genus Tanaella. This indicates examination of addition type material or topotypic specimens of the other members of the genus needed to determine whether or not they exhibit these features.
of small setules. The lack of records for Tanaella in the coastal and deep waters of the Caribbean may be due to the lack of sampling in live-bottom habitats.

Author Contributions
• Andrés G. Morales-Núñez conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
• Néstor E. Ardila contributed reagents/materials/analysis tools, prepared figures and/or tables, approved the final draft.

Field Study Permissions
The following information was supplied relating to field study approvals (i.e., approving body and any reference numbers):