Chondrochelia Guţu, 2016 (Crustacea, Peracarida, Tanaidacea, Leptocheliidae) from North America: new species, redescription and distribution using morphological and molecular data

Until now, four species of the genus Chondrochelia Guţu, 2016 have been recorded from America. Using morphological and molecular data, we were able to recognize and describe two new species, Chondrochelia caribensis sp. nov. from the Mexican Caribbean and Chondrochelia winfieldi sp. nov. from the Gulf of Mexico. We found significant genetic divergence values between species based on the nucleotide sequences of cytochrome oxidase subunit I to support the morphological data. Also, the range of distribution of two species: Chondrochelia mexicana (Jarquín-González, García-Madrigal & Carrera-Parra, 2015) and Chondrochelia ortizi (Jarquín-González, 2016), were expanded within their described geographic regions. In contrast, the supposed distribution of the Brazilian C. dubia in the Mexican Caribbean and the Gulf of Mexico was rejected. Additionally, Chondrochelia algicola (Harger, 1878) was redescribed based upon type material. Minute details and ornamentation of some structures of three species were examined using SEM.


INTRODUCTION
The specimens were examined under a Carl Zeiss SV6 stereomicroscope. The total body length of specimens was measured from the anterior end of the cephalothorax (i.e., rostrum) to the posterior margin of the pleotelson. To determine the proportions of the morphological structures (e.g., antennules, pereopods) the total length was measured vs the width at the mid-length. Apart from mouthparts, dissections were performed on the right side of the body and the appendages were mounted in glycerol and sealed with transparent nail varnish. Drawings of the taxonomic structures were made using a camera lucida at 4×-40× magnification. The terminology used for anatomical features is based on Larsen (2003) and Guţu (2016). For the scanning electron microscopy (SEM) analysis, the specimens were dehydrated in a series of different concentration of hexamethyldisilazane (HMDS). Once air-dried, they were mounted on aluminum stubs and coated with gold for observation using a JEOL JSM-6010Plus-LA SEM at the Scanning Electron Microscopy Laboratory (LMEB), ECOSUR, Chetumal. Photographs of some diagnostic characters were obtained to complement the descriptions of the species.
The sequences were aligned using ClustalW method, and no indels or stop codons were found. The final aligned dataset for analysis was 418 base pairs long. The selection of the best model substitution was determined according with the lowest Bayesian Information Criterion (BIC) score. As result, we used Hasegawa-Kishino-Yano (HKY), using a discrete Gamma distribution (+G) with five rate categories and by assuming that a certain fraction of sites is evolutionarily invariable (+I) as model to construct a tree using the Maximum Likelihood analysis. Additionally, we used the Kimura 2-Parameter (K2P) model to estimate the average evolutionary divergence over sequence pairs within and between species. All analyzes were carried out with the MEGA7 program (Kumar, Stecher & Tamura, 2015).
The electronic version of this article in portable document format will represent a published work according to the International Commission on Zoological Nomenclature (ICZN), and hence the new names contained in the electronic version are effectively published under that Code from the electronic edition alone. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix http://zoobank.org/. The LSID for this publication is: urn:lsid: zoobank.org:pub:DB236268-1523-41AF-8701-16A3E1D696F0. The online version of this work is archived and available from the following digital repositories: PeerJ, PubMed Central, and CLOCKSS.
Article-3 0.4 times as long as article-1, 3.1 times longer than broad, with two distal setae and one aesthetasc. Article-4 (¼flagellum) small, with three setae. Antenna ( Fig. 1D) with six articles. Article-1 0.8 times as long as broad, with one small distal seta. Article-2 1.1 times longer than broad, with one subdistal seta and one slender distal spine on distal extremity, and with slender ventrodistal spine. Article-3 as long as broad, with slender dorsodistal spine. Article-4 3.8 times longer than broad, with one mesial seta and three distal setae. Article-5 0.4 times as long as article-4, 2.5 times longer than broad, with distal seta. Article-6 small, with seven setae. Labium and labrum (Figs. 1E and 1F) setose, as figured. Jarquín-González and Carrera-Parra (2022) Mandibles. Pars molaris well developed in both mandibles, with strong rugosity on masticatory surface. Left mandible ( Fig. 1G) with five denticled pars incisiva; lacinia mobilis stout and smooth. Pars incisiva of right mandible (Fig. 1H) bifid and distally crenulate. Maxillule ( Fig 1I) with ten robust distal spines and numerous setae on distal extremity and laterally; palp with two distal setae (not illustrated).
Pereopod 2 (Fig. 2E) smaller than pereopod 1, basis 2.8 times longer than broad, with dorsoproximal seta. Ischium with ventral seta. Merus short, 1.7 times longer than broad, with ventrodistal slender spine and ventrodistal seta. Carpus as long as merus, with two setae and one small spine on distal extremity. Propodus 0.6 times as long as basis, with two dorso-subdistal setae and one ventro-subdistal slender spine. Dactylus naked, 1.3 times longer than unguis, together with unguis 0.5 times as long as propodus.
Pereopod 4 (Fig. 2G) basis 3.8 times longer than broad. Ischium with two ventral setae. Merus with oblique articulation with carpus, 2.5 times longer than broad, with two small ventrodistal spines. Carpus as long as merus, with two setae and three spines on distal extremity. Propodus 0.9 times as long as carpus, but narrower, with three dorso-subdistal setae and two ventro-subdistal spines. Dactylus naked, 3.2 times longer than unguis, together with unguis 0.7 times as long as propodus.
Adult male. Syntype USNM 35963, 2.3 mm (Figs. 4A and 4B,6H). Body about five times longer than broad. Carapace subrectangular, 1.2 times longer than broad, as long as the pereonites 1-3 together and 1.2 times longer than pleon; ocular lobes well defined, eyes pigmented. Pereon 2.2 times longer than carapace and 2.5 times longer than broad; all pereonites respectively, 3.4, 2.8, 3.4, 2.0, 2.0 and 2.3 times broader than long. Pleon slightly shorter than pereonites 1-3 together. Pleotelson 0.3 times as long as pleon, with four dorsolateral setae; posterior apex similar to female. Antennule (Fig. 4D) 0.6 times as long as body. Article-1 0.7 times as long as carapace and 4.4 times longer than broad, with two distal setae and one subproximal sensory seta. Article-2 0.4 times as long as article-1, 2.1 times longer than broad, with one proximal seta. Article-3 0.3 times as long as article-1, 1.7 times longer than broad, with one distal seta. Flagellum 1.7 times longer than peduncle article-1, with eight articles; each flagellar articles with three or four aesthetascs; last article minute, with three distal setae.
Antenna ( Fig. 4E) with article-1 1.3 times longer than broad, naked. Article-2 1.1 times longer than broad, with two distal spines and one seta. Article-3 0.7 times as long as broad, with one dorsodistal spine. Article-4 3.6 times longer than broad, with three dorsodistal setae. Article-5 0.8 times as long as article-4, 4.8 times longer than broad, with two dorsodistal setae. Article-6 small, with four distal setae.
Mouthparts reduced (Fig. 4F). Maxilliped rudimentary; maxillule palp with one seta. Cheliped (Figs. 4G and 4H) stout, 0.7 times as long as body. Basis twice as long as broad, with one small dorso-subdistal seta. Merus wider distally, with three ventral setae. Carpus about four times longer than broad, with three ventral setae and three dorsal setae. Propodus with dorsal seta near dactylus articulation, comb-row with 18 ventral setae. Fixed finger cutting edge with two processes separated by a pronounced curvature, proximal process longer and pointed, distal process shorter and apically crenulate; with six setae, three ventral. Dactylus cutting edge with one proximoventral seta and eight spinules.
Pereopod 1 (Fig. 5C) basis about five times longer than broad, with one dorsoproximal seta. Ischium with ventral seta. Merus as long as carpus, twice as long as broad, with one ventrodistal seta. Carpus about twice as long as broad, with five distal setae on distal extremity. Propodus 0.9 times as long as merus and carpus together, 4.6 times longer than broad, with three dorso-subdistal setae and one ventro-subdistal slender spine. Dactylus similar to female, but together with unguis 0.7 times as long as propodus.
Pereopod 2 (Fig. 5D) basis 3.5 times longer than broad, with one dorsoproximal seta. Ischium with ventral seta. Merus as long as carpus, 2.2 times longer than broad, with one slender spine and one seta on ventral side. Carpus 2.1 times longer than broad, with two setae and two spines on distal extremity. Propodus 1.7 times longer than carpus, 4.3 times longer than broad, with two dorso-subdistal setae and one ventro-subdistal slender spine. Dactylus naked, 0.4 times as long as carpus, 1.7 times longer than dactylus, together with unguis 0.5 times as long as propodus.
Pereopod 5 (Fig. 6B) similar to pereopod 4, but basis with one middorsal seta. Carpus with one seta and three stout spines on distal extremity. Propodus five times longer than broad, with four dorsodistal setae and two ventro-subdistal spines.
Habitat. Shallow-water, in eelgrass and algae.
Remarks. Comparing Chondrochelia algicola with other members of the genus Chondrochelia, we observed morphological similarities to Chondrochelia savignyi as redescribed by Bamber (2010) from Madeira, Portugal. In males of both species, the body is about five times longer than broad, the carapace is subrectangular, the chelipeds are small and slender, the pereopod 1 propodus has four distal setae, the uropod exopod is uniarticulate, and the endopod has six articles. However, they differ because C. algicola has an antennule 0.6 times as long as the body, while in C. savignyi it is shorter, 0.4 times as long; in C. algicola the chelipeds are 0.7 times as long as body, but 0.5 times in C. savignyi; C. algicola has five distal setae on the pereopod 1 carpus, while C. savignyi has only two; C. algicola has one ventro-subdistal slender spine on the pereopod 2 propodus, but it is absent in C. savignyi; C. algicola has two dorsodistal setae on the propodus of pereopod 4, whereas C. savignyi has four setae. Regarding females, C. algicola has an oval carapace, while in C. savignyi it is subrectangular; in C. algicola the spine of antenna article-3 is 0.5 times as long as anntenal article-4, whereas in C. savignyi such spine is 0.3 times as long; C. algicola has the left mandible with a stout and smooth lacinia mobilis, while in C. savignyi it is distally crenulate; C. algicola has two distal setae and three flat spines on the maxillipedal endite, whereas C. savignyi has a single distal seta and three spatulate spines; C. algicola has two setae and three distal spines on the pereopod 4 carpus, while C. savignyi has only one seta and four spines; lastly, C. algicola has a pappose seta on the pereopod 5 propodus, which is lacking in C. savignyi. Diagnosis. Female. Mouthparts. Left mandible with weakly bifid pars incisiva, lacinia mobilis with four outer denticles and inner setules; maxilliped left basis with six plumose setae, right basis with five plumose setae. Chelipeds. Fixed finger cutting edge with three setulate processes; dactylus cutting edge crenulate proximally and with four distal processes. Pereopods. Pereopod 1 carpus with six distal plumose setae. Pereopod 2 carpus with three setae and two spines on distal extremity. Pereopod 4 propodus with five plumose setae and one pappose seta on distal extremity. Pereopod 6 propodus with 10 dorso-subdistal plumose setae. Male. Carapace round. Antennules. Flagellum as long as peduncle article-1; with 10 articles. Chelipeds. Fixed finger cutting edge with two processes, proximal broad and pointed, distal narrow and blunt. Pereopods. Pereopod 1 carpus with six distal plumose setae. Pereopod 2 merus with one dorso-subdistal plumose seta, with one setulate spine and one plumose seta on ventral side. Pereopod 4 propodus with three dorso-subdistal plumose setae. Pereopod 6 propodus with eight dorso-subdistal plumose setae. Both sexes. Uropods with exopod biarticulate and endopod with five articles. Etymology. The name of the species refers to the geographic region where specimens were collected.

Chondrochelia
Description. Non-ovigerous female. Holotype ECOSUR 235, 4.6 mm (Figs. 7A, 9F). Body seven times longer than broad. Carapace oval, 1.3 times longer than broad, 0.9 times as long as pereonites 1-3 together. Ocular lobes well defined, eyes pigmented. Pereon 2.4 times longer than carapace and 3.9 times longer than broad; all pereonites respectively, 2.7, 2.0, 1.5, 1.2, 1.5 and 2.0 times broader than long. Pleon 0.7 times as long as pereonites 1-3 together. Pleotelson 0.3 times as long as pleon, posterior apex with four simple setae and two sensory setae. Antennule ( Fig. 7B) with three long peduncular and one short flagellar articles. Article-1 3.7 times longer than broad, with two mesial setae, one distal simple seta, and two sensory setae (one subproximal and other mesial). Article-2 0.3 times as long as article-1, 1.8 times longer than broad, with two simple setae and one sensory distal seta. Article-3 0.3 times as long as article-1, 2.7 times longer than broad, with two distal simple setae and one aesthetasc. Article (= flagellum) small, with three distal simple setae. Antenna ( Fig. 7C) with six articles. Article-1 longer than broad, with one distal simple seta. Article-2 0.8 times as long as broad, narrow distally, with two stout distal spines. Article-3 about as long as broad, with one stout distal spine. Article-4 3.6 times longer than broad, with two mesial, two distal sensory setae, and three simple setae distally. Article-5 0.4 times as long as article-4, 2.6 times longer than broad, with two simple distal setae. Article-6 small, with six simple setae. Maxilliped (Figs. 8B and 8C). Left basis with six plumose setae, and right basis with five plumose setae on distal extremity. Palp article-1, about as long as endite, naked; article-2 with one dorsal plumose seta and four ventrodistal plumose setae, mesial margin finely setulate; article-3 largest, with 10 plumose setae ventrally; article-4 with one mesial plumose seta, seven ventrodistal plumose setae, two plumose setae distally, and scales. Endites with one plumose seta and three flat spines (two longer and one short, relatively round) on distal extremity.
Cheliped (Figs. 8D and 8E) basis 1.4 times longer than broad, with one small dorso-subdistal simple seta. Merus with three simple ventral setae. Carpus, 1.8 times longer than broad, with two small dorsoproximal spines, one short dorsodistal seta and three ventrodistal setae. Propodus with one dorsal simple seta near dactylus articulation, comb-row with four ventral setulate spines and scales. Fixed finger cutting edge with three setulate processes; with 11 simple setae, six ventral. Dactylus with ventroproximal simple seta, cutting edge crenulate proximally and with four broad distal processes. Pereopod 1 (Fig. 8F) basis 4.3 times longer than broad, with one plumose seta and one sensory seta subproximally. Ischium with ventral plumose seta. Merus with oblique articulation with carpus, 2.7 times longer than broad, with one dorso-subdistal plumose seta and two ventrodistal plumose setae. Carpus 1.6 times longer than broad, with six plumose setae on distal extremity. Propodus 0.7 times as long as merus and carpus together, 4.8 times longer than broad, with three dorso-subdistal plumose setae and one ventro-subdistal plumose seta. Dactylus about as long as carpus, with dorsoproximal plumose seta; together with unguis as long as propodus. Pereopod 2 (Fig. 8G) basis twice as long as broad, with one proximal plumose seta and two proximal sensory setae. Ischium with two ventral plumose setae. Merus 1.8 times longer than broad, with two plumose setae and one setulate spine on distal extremity. Carpus 0.7 times as long as merus, with three plumose setae, and two small setulate spines and scales on distal extremity. Propodus about 0.6 times as long as basis, with four distal plumose setae, one subdistal setulate spine and scales. Dactylus with scales, 1.1 times longer than unguis, together with unguis approximately 0.5 times as long as propodus.
Pleopod 1 (Fig. 9D). Peduncle with one dorso-subdistal circumplumose seta. Endopod with one middorsal circumplumose seta, one proximoventral circumplumose seta, and 19 ventral plumose setae. Exopod with proximoventral circumplumose seta and 29 ventral plumose setae. Uropod (Fig. 9E). Exopod 0.8 times as long as endopod article-1; biarticulate, article-1 small and with one distal simple seta with terminal pore, article-2 with two apical simple setae with terminal pore. Endopod with five articles; articles 1 and 2 broader than other articles; articles 1 and 3 with two simple setae with terminal pore; article-2 with two simple setae with terminal pore and one sensory seta; article-4 with two sensory setae and two simple setae with terminal pore; article-5 with two sensory setae and five simple setae with terminal pore.
Antennule (Figs. 10B and 10C) 0.4 times as long as body. Article-1 0.7 times as long as carapace, five times longer than broad, with one subproximal sensory seta, two simple setae and four sensory setae on subdistal extremity. Article-2 0.4 times as long as article-1, 2.5 times longer than broad, with two simple setae and two sensory setae on subdistal extremity. Article-3 0.2 times as long as article-1, 1.7 times longer than broad, with two simple distal setae. Flagellum as long as peduncle article-1, with ten articles; each flagellar article with at least five aesthetascs; last article minute, with six distal simple setae.
Antenna (Figs. 10D and 10E) article-1 twice as broad as long, with one subproximal simple seta. Article-2 about 0.7 times as long as broad, with two stout distal spines. Article-3 as long as broad, with one distal stout spine. Article-4 4.3 times longer than broad, with one mesial sensory seta and one mesial simple seta, three distal simple setae, and two distal sensory setae. Article-5 longer than article-4, 6.2 times longer than broad, with three distal simple setae, one of them small. Article-6 small, with six distal simple setae.
Mouthparts reduced. Maxilliped rudimentary (not illustrated). Cheliped (Figs. 10F and 10G) stout, 0.7 times as long as body. Basis 1.6 times longer than broad, with one dorsodistal simple seta. Merus wider distally, with three ventral setae. Carpus about three times longer than broad, with three ventral setae and four dorsal setae. Propodus with dorsal seta near dactylus articulation, comb-row with 18 ventral setulate spines. Fixed finger cutting edge with two processes separated by a pronounced curvature, proximal broad with pointed tip, distal narrow with blunt tip, with nine simple setae, three dorsal. Dactylus cutting edge with one proximodorsal simple seta and 10 spinules.
Pereopod 2 (Fig. 11B) basis 3.7 times longer than broad, with one dorsoproximal plumose seta and one dorsoproximal sensory seta. Ischium with two ventral plumose setae. Merus as long as carpus, 2.1 times longer than broad, with one dorso-subdistal plumose seta, and one setulate spine and one plumose seta on ventral side, with scales. Carpus 2.1 times longer than broad, with three plumose setae and two stout setulate spines on distal extremity, with scales. Propodus four times longer than broad, with three dorso-subdistal plumose setae, one ventro-subdistal spine and scales. Dactylus with scales, 0.3 times as long as carpus, 2.1 times longer than unguis, together with unguis 0.4 times as long as propodus.
Additionally, the SEM analysis allowed us to observe in the detail the ornamentation of antennules and antennae (Fig. 13A), maxillipeds (Fig. 13B), setae on the pereopods (Figs. 13C, 13F), the processes on the cutting edge of the cheliped fixed finger and dactylus (Figs. 13D and 13E, 13H-13J), as well as the shape of uropods in mancae (Fig. 13G).
Remarks. Chondrochelia caribensis sp. nov. resembles Chondrochelia africana (Larsen & Froufe, 2013) from Guinea Bissau, West Africa, as the males and females of both species have a pereopod 6 propodus with at least seven setae, two of them longer than the others, and the uropod endopod has five articles, the exopod two articles. Also, adult females of both species have stout spines on antenna articles 2 and 3, the pereopod 1 merus has two ventrodistal setae, the pereopod 1 carpus has six distal setae, and the pereopod 1 propodus has four distal setae. However, they differ because females of C. caribensis sp. nov. has fine setae on the inner margin of the pars incisiva of the left mandible, while in C. africana the inner margin lacks these; C. caribensis sp. nov. has up to six distal plumose setae on the maxilliped basis, whereas C. africana has only three; in C. caribensis sp. nov. the cheliped dactylus cutting edge is crenulate proximally and with four distal processes, while in C. africana the cutting edge is smooth. Also, in C. caribensis sp. nov. the uropod exopod is up to 0.8 times as long as endopod article-1, whereas in C. africana the exopod is more than 0.8 times as long. Regarding males, both species are similar in having eight articles in the flagellum of the antennule, two processes on the fixed finger of dactylus separated by a pronounced curvature, and the merus of pereopod 1 with one dorso-subdistal seta and one small subventral seta. However, they differ because in C. caribensis sp. nov. the antennule article-1 is up to five times longer than broad, while in C. africana it is more than five times longer than broad; in C. caribensis sp. nov. the proximal process is larger than the distal process on fixed finger of cheliped, whereas in C. africana the proximal process is smaller; in C. caribensis sp. nov. uropod exopod is 0.7 times as long as endopod article-1, while in C. africana the exopod is 1.7 times longer.
Females of C. caribensis sp. nov. and C. dubia differ as in C. dubia the antennule peduncle article-3 has a length-width ratio of 4.2, while in C. caribensis sp. nov. it is stouter, 2.7; in C. dubia the length-width ratio of the antenna articles 4 and 5 are 5.0 and 4.5, compared to 3.6 and 2.6 in C. caribensis sp. nov. Also, in C. dubia the uropod is almost 0.16 times as long as the body, whereas in C. caribensis sp. nov. it is less than 0.16 times; C. dubia has an uniarticulated uropod exopod, while in C. caribensis sp. nov. it is biarticulate. Other differences are shown in Table 2.
Description. Non-ovigerous female. Holotype ECOSUR 238, 3.0 mm (Fig. 14A). Body 6.4 times longer than broad. Carapace oval, 1.3 times longer than broad, 0.7 times as long as pereonites 1-3 together. Ocular lobes well defined, eyes pigmented. Pereon three times longer than carapace and 3.8 times longer than broad; all pereonites respectively, 2.3, 1.5, 1.5, 1.2, 1.5 and 2.3 times broader than long. Pleon 0.6 times as long as pereonites 1-3 together. Pleotelson about 0.3 times as long as pleon, posterior apex slightly projected, with four distal setae. Antennule ( Fig. 14B) with three long peduncular and one short flagellar articles. Article-1 about three times longer than broad, with two mesial setae, two subdistal simple setae, five sensory setae and scales. Article-2 about 0.3 times as long as peduncle article-1, 1.4 times longer than broad, with two distal simple setae and scales. Article-3 about 0.3 times as long as peduncle article-1, 2.5 times longer than broad, with two simple setae and one aesthetasc. Article-4 (= flagellum) small, with three simple setae.
Antenna (Fig. 14C) with six articles. Article-1 1.3 times longer than broad, narrow distally, naked. Article-2 1.3 times longer than broad, narrow proximally, with two slender distal spines. Article-3 longer than broad, with one slender distal spine. Article-4 3.4 times longer than broad, with three distal simple setae, one mesial and three distal sensory setae. Article-5 0.4 times as long as article-4, 2.3 times longer than broad, with two distal simple setae. Article-6 small, with three simple setae.
Cheliped (Figs. 15A and 15B) basis 1.2 times longer than broad, with one small dorsodistal simple seta. Merus with three ventral setae. Carpus about twice as long as broad, with two dorsal-subproximal spinules and two dorso-subdistal setae, with three ventrodistal setae. Propodus with one dorsal seta near dactylus articulation, comb-row with five ventral setulate spines and scales. Fixed finger cutting edge with three processes, the first process prominent; with seven setae, three dorsal. Dactylus cutting edge with one ventroproximal seta, and three subproximal spinules.
Pereopod 1 (Fig. 15C) basis 3.7 times longer than broad, with one dorsoproximal plumose seta and one dorsoproximal sensory seta. Ischium with two ventral plumose setae. Merus with oblique articulation with carpus, 2.4 times longer than broad, with ventrodistal plumose seta. Carpus 0.7 times as long as merus, 1.7 times longer than broad, with six distal plumose setae. Propodus 0.6 times as long as merus and carpus together, 3.6 times longer than broad, with three dorso-subdistal plumose setae and one ventro-subdistal plumose seta. Dactylus with one dorsoproximal plumose seta and scales, about as long as carpus, 1.4 times longer than unguis, together with unguis as long as propodus.
Pereopod 2 (Fig. 15D) smaller than pereopod 1, basis 2.8 times longer than broad, with one dorsoproximal plumose seta and one dorsoproximal sensory seta. Ischium with one ventral plumose seta. Merus short, 1.7 times longer than broad, with one small ventrodistal setulate spine and one ventrodistal plumose seta. Carpus 0.8 times as long as merus, with three plumose setae and two small setulate spines on distal extremity. Propodus 0.5 times as long as basis, with three dorso-subdistal plumose setae and one small ventro-subdistal setulate spine. Dactylus with scales, 1.8 times longer than unguis, together with unguis 0.6 times as long as propodus.
Pereopod 4 (Fig. 15F) basis 1.9 times longer than broad, naked. Ischium with two ventral plumose setae. Merus with oblique articulation with carpus, 2.3 times longer than broad, with two small ventrodistal spines. Carpus 0.7 times as long as merus, with two plumose setae and three setulate spines on distal extremity. Propodus 0.5 times as long as merus and carpus together, with three dorsodistal plumose setae and two ventrodistal setulate spines. Dactylus with scales, 2.2 times longer than unguis, together with unguis 0.5 times as long as propodus.
Pleopods similar to other members of genus Chondrochelia (not illustrated). Pleopod 1 peduncle with one ventrodistal circumplumose seta. Endopod with one middorsal circumplumose seta, one proximoventral circumplumose seta and 13 ventral plumose setae. Exopod with one proximoventral circumplumose seta and 23 ventral plumose setae. Uropod (Fig. 15I) peduncle naked. Exopod 0.9 times as long as endopod article-1; biarticulate, article-1 small and with one subdistal simple seta with terminal pore, article-2 with two apical simple setae with terminal pore. Endopod with five articles; article-1 broader than other articles; articles 1 and 2 with two distal simple setae; article-3 shorter than other articles, with one sensory seta; articles 4 and 5 subequal; article-4 with one simple seta with terminal pore and one sensory seta; article-5 with five simple setae with terminal pore and one sensory seta.
Antennule (Fig. 16B) 0.4 times as long as body. Article-1 0.5 times as long as carapace, 4.1 times longer than broad, with two small subproximal sensory setae and two distal simple setae. Article-2 about 0.5 times as long as peduncle article-1, 2.4 times longer than broad, with two distal simple setae and three sensory setae. Article-3 0.3 times as long as peduncle article-1, 1.7 times longer than broad, with two small distal simple setae and one sensory seta. Flagellum 1.5 times longer than peduncle article-1, with nine articles; each flagellar article with at least four aesthetascs; last article minute, with four distal simple setae.
Antenna (Fig. 16C) article-1 as long as broad, naked. Article-2 about 0.6 times as long as broad, with two slender distal spines. Article-3 0.7 times as long as broad, with one distal slender spine. Article-4 3.4 times longer than broad, with three distal simple setae, one mesial sensory seta, and one distal sensory seta. Article-5 six times longer than broad, with two distal simple setae. Article-6 small, with five distal simple setae.
Mouthparts reduced. Maxilliped rudimentary (not illustrated). Cheliped (Figs. 16D and 16E) stout, 0.6 times as long as body. Basis 1.3 times longer than broad, with one dorso-subdistal seta. Merus wider distally, with three ventral simple setae. Carpus three times longer than broad, with three ventral simple setae, three dorso-subproximal simple setae, and one dorso-subdistal simple seta. Propodus with one simple seta near dactylus articulation, comb-row with 11 ventral setulate spines. Fixed finger cutting edge with two processes separated by a weak curvature; proximal process shorter and pointed; distal process longer, tubular and blunt; with seven simple setae, three dorsal. Dactylus cutting edge with one ventroproximal seta and nine spinules.
Pereopod 1 (Fig. 16F) basis 4.1 times longer than broad, with one dorsoproximal plumose seta. Ischium with one ventral plumose seta. Merus as long as carpus, with one ventrodistal plumose seta. Carpus 2.5 times longer than broad, with four plumose setae on distal extremity. Propodus 0.5 times as long as merus and carpus together, 3.3 times longer than broad, with five dorsodistal plumose setae and one ventro-subdistal slender spine. Dactylus with one subproximal plumose seta and scales, 2.3 times longer than unguis, together with unguis 0.8 times as long as propodus.
Pereopod 2 (Fig. 17A) basis four times longer than broad, with one dorso-subproximal seta and two dorso-subproximal sensory setae. Ischium with one ventral plumose seta. Merus as long as carpus, with one plumose seta and one setulate spine on ventrodistal margin. Carpus twice as long as broad, with three plumose setae and two setulate spines on distal extremity. Propodus about four times longer than broad, with two dorso-subdistal plumose setae and two ventro-subdistal setulate spines, with scales. Dactylus with one mesial plumose seta and scales, 0.5 times as long as carpus, 3.2 times longer than unguis, together with unguis 0.6 times as long as propodus.
Pleopods similar to other members of genus Chondrochelia (not illustrated). Peduncle with one ventrodistal circumplumose seta. Endopod with one middorsal circumplumose seta, one proximoventral circumplumose seta and 14 ventral plumose setae. Exopod with one proximoventral circumplumose seta and 23 ventral plumose setae. Uropod (Fig. 17F) peduncle with six dorso-subdistal setae. Exopod 1.2 times longer than endopod article-1; biarticulate, article-1 shorter than article-2, article-1 with one distal simple seta with terminal pore, article-2 with two simple setae with terminal pore. Endopod with five articles; article-1 broader than the following articles, with two simple setae with terminal pore; article-2 with three simple setae with terminal pore and one sensory seta; article-3 shorter than other articles, with three simple setae with terminal pore; article-4 longer than other articles, with two simple setae with terminal pore; article-5 more slender than other articles, with five simple setae with terminal pore.
The SEM analysis allowed us to observe that females have simple setae and setules on the antennules (Fig. 18A), numerous scales on the base of the maxilliped (Fig. 18B), the detail of process on the cutting edge of the cheliped (Fig. 18C), the plumose setae, scales, setulate spines and pappose seta on the carpus and propodus of the pereopods (Figs. 18D-18F). In males, both processes on the cutting edge of the fixed finger of cheliped have striated surfaces (Figs. 19A and 19B); also, the spines on the propodus of pereopods 2-6 are ornamented with several small protuberances (Figs. 19C and 19D Remarks. Chondrochelia winfieldi sp. nov. resembles C. algicola (Harger, 1878) from Massachusetts, USA, because the adult females of both species have an oval carapace, the pars incisiva of the right mandible is crenulate and with bifurcated apex, and by having the maxilliped endites with two long and one short, flattened setae. However, they have evident differences with females of C. winfieldi sp. nov. having the left mandible with a four denticled pars incisiva and pointed lacinia mobilis, while in C. algicola these are five denticled and stout respectively; C. winfieldi sp. nov. has three processes on the cheliped fixed finger cutting edge, whereas C. algicola has five; C. winfieldi sp. nov. has three spinules on the cutting edge of the cheliped dactylus, while in C. algicola it is smooth; C. winfieldi sp. nov. has six distal setae on the pereopod 1 carpus, but four in C. algicola; C. winfieldi sp. nov. has a biarticulate uropod exopod, uniarticulate in C. algicola; C. winfieldi sp. nov. has a uropod endopod with five articles, but six in C. algicola.
The males of both species have large eyes, the carapace is as long as broad, and it is as long as pereonites 1-3, antenna article-1 is naked; the cheliped fixed finger cutting edge has a proximal process and a mesial process, and they have two simple setae on the pereopod 3 propodus. They can be distinguished because in C. winfieldi sp. nov. the antennule length is less than 0.5 times the body length, whereas in C. algicola is more than 0.5 times; in C. winfieldi sp. nov. the proximal process on the cutting edge is shorter, while in C. algicola is longer; in C. winfieldi sp. nov. the distal process on cutting edge is longer, tubular and blunt, whereas in C. algicola it is shorter and apically crenulate. Furthermore, C. winfieldi sp. nov. has two ventro-subdistal setulate spines on the pereopod 2 propodus, while C. algicola has one ventro-subdistal slender spine; in C. winfieldi sp.
Remarks. According to , the males of Chondrochelia ortizi are characterized by having a subrectangular carapace, an antennule flagellum with eight articles, cheliped fixed finger cutting edge with two small and unequal mesial processes, cheliped dactylus cutting edge with six spinules, pereopod 1 carpus with six distal setae, and pereopod 6 propodus with five distal setae. Whereas the females have the antennule article-1 3.6 times longer than broad, the left mandible lacinia mobilis with fine inner setules, and the cheliped dactylus cutting edge with three proximal spinules and seven processes. In both sexes, the uropod endopod has five articles.
This species was only known from the Gulf of Guanahacabibes and Isla de la Juventud, Cuba. However, from the morphological and molecular analysis, we were able to confirm that this species is also distributed in waters of the Gulf of Mexico, specifically at Champotón, Campeche, Mexico.
Distribution. Gulf of Mexico (Champotón, Campeche, Mexico) and Cuba (Gulf of Guanahacabibes and Isla de la Juventud).

Molecular analysis
The molecular analyses based on the COI gene supported the morphological differences found between the species in this study (Fig. 22). Chondrochelia caribensis sp. nov. has a 23% genetic divergence (K2P) from C. winfieldi sp. nov., and both new species are close related to C. ortizi and C. mexicana, with genetic divergences ranging from 27.7% to 24.2%. Compared to C. dubia, the species name previously given to the specimens of both new species, C. caribensis sp. nov. and C. winfieldi sp. nov. have a 34.7% and 34.4% genetic divergence, respectively. These genetic divergences clearly exceed the lowest values (4.9%) of interspecific divergence found in crustaceans (Costa et al., 2007;Montiel-Martínez et al., 2008). Unfortunately, the only available sequence identified as C. dubia was obtained from a specimen collected distant from its type locality, so it is quite possible that it does not belong to C. dubia. However, the result obtained highlights the existence of pseudo-cryptic species under the name C. dubia in the Caribbean and Gulf of Mexico region. To reinforce our hypothesis, the redescription of C. dubia based on morphological and molecular data of topotypical specimens is essential; unfortunately, we could not Figure 22 Maximum likelihood tree of COI sequences. Using Hasegawa-Kishino-Yano with a discrete Gamma distribution with five rate categories and by assuming that a certain fraction of sites is evolutionarily invariable (HKY+G+I).
Full-size  DOI: 10.7717/peerj.12773/ fig-22 obtain these. Our results, both morphological and molecular, nevertheless establish that C. dubia is not distributed in the Mexican Caribbean and the Gulf of Mexico, as had previously been proposed. Also, we found that the species C. ortizi, previously only found in Cuba, is also present in the Gulf of Mexico.

DISCUSSION
Analysis of material from the United States, Cuba and Mexico, has resulted in six species of the genus Chondrochelia being recorded, two of them described in this paper. In the last decade, the traditional taxonomic descriptions have been strengthened by using molecular markers, especially COI. For tanaidaceans, the use of integrative taxonomy using morphological and molecular data has been crucial to clarify problems related to cryptic or pseudo-cryptic species, polymorphism and ontogeny, and to establish general patterns of distribution. These demonstrate that the wide distributions of some species are questionable and deserve to be corroborated. This approach has also shown that there is an underestimation in the species diversity.
Here, we show a clear example of this issue; after the reexamination of specimens of "Leptochelia dubia" using a morphological and molecular information, we found two new species for science, Chondrochelia caribensis sp. nov. and Chondrochelia winfieldi sp. nov. that represent the first Chondrochelia species described for the Mexican Caribbean and Gulf of Mexico, respectively. Also, we were able to establish an increase in the distribution range for Chondrochelia mexicana and Chondrochelia ortizi.
The use of SEM revealed that the species have a more complex morphology and ornamentation than previously described for the genus; even in mancae. According to Zimmer, Araujo & Bond-Buckup, 2009 this taxonomic tool is important because contributes significantly to the morphological comparison at the levels of species, genera and families.

CONCLUSIONS
Chondrochelia from America included four species, with C. dubia thought to have a wide distribution. Here, we described two new species using morphological and molecular data, and another poorly characterized species was redescribed; also, the distribution of two species was expanded within their geographic regions where they were previously described. In contrast, the supposed distribution of C. dubia in the Mexican Caribbean and the Gulf of Mexico is rejected. Using morphological and molecular data offers a good strategy for the study of the biological diversity of small crustaceans since it allows reliable species discrimination and strengthens the taxonomic identification that in these groups is usually quite complex due to their size, crypticity and biology. It is important to continue advancing the knowledge of tanaidaceans, especially in regions with high biological diversity such as the Mexican Caribbean. Determining the current taxonomic status of the species will make it possible to deepen in the ecological knowledge of the group and thus establish lines of research that reinforce the conservation and management strategies of marine and coastal natural resources.