New records of isopods ( Crustacea : Peracarida : Isopoda ) from the Mesoamerican Reef at Puerto Morelos , Quintana Roo , Mexico

New distribution records are presented for 19 species of isopods that are recorded for the Mexican Caribbean coast for the first time. The sampling program was conducted in three sites and at three different depths in each site within the Arrecife de Puerto Morelos Nature Reserve. The new records belong to 10 families and 15 genera in the suborders Asellota, Cymothoida and Sphaeromatidea. With the new records included herein isopods could be the most diverse group of peracarid crustaceans found in the Puerto Morelos Reef.


INTRODUCTION
The Mesoamerican Reef, in the western Caribbean, has been recognized for its socioeconomic importance and as a productive system that supports a great diversity of species (Briones and Machain 2005).As part of a larger project designed to compare reef sections with high use and of high conservation value in the Puerto Morelos area in the Mexican state of Quintana Roo, a sampling program of cryptofauna was undertaken from January 2013 to January 2014.Three sites were selected (conserved, in recovery, and degraded) considering the assessments made by the local environmental authority, and the cryptofauna associated with coral rubble was collected at three depths and identified.
We take the Mexican Caribbean to be the area between Cape Catoche, the northeast tip of the Yucatan Peninsula, to Xcalak, Quintana Roo, at the border with Belize, a coastline of approximately 418 km.In general, the diversity of marine isopods from the Mexican Caribbean is poorly known.While few studies have dealt with isopods from this area, there are numerous records for the group from the Greater Caribbean where more than 300 species have been recorded (Kensley and Schotte 1994).The most extensive work on crustaceans is that of Markham et al. (1990) who reported a total of 309 species, 41 of which were isopods, including 21 new records, from the Mexican Caribbean coast from Cancun to Chetumal.Barriga and Briones (1992) reported eight species of Excorallana from the Gulf and the Caribbean coasts of Mexico.From the Puerto Morelos reef lagoon, Quintana Roo, van Tussenbroek and Brearley (1998) reported the isopod Limnoria simulata Menzies, 1957 (Limnoriidae) burrowing in the turtle grass Thalassia testudinum Banks ex König forming canal systems, using the burrows for reproduction.Campos-Vázquez (2000) collected crustaceans associated with macroalgae in Bajo Pepito, Isla Mujeres, Mexican Caribbean and found Isopoda to be the most abundant group and eight species were identified.Van Tussenbroek et al. (2012) investigated meso-faunal invertebrates visiting male and female flowers of the seagrass Thalassia testudinum at night in the Puerto Morelos reef lagoon, on 76 flowers they found 57 species of crustaceans, eight of them isopods, including two new records.
The main goal of the larger study, from which this particular report is derived, was to compare the diversity and abundance of cryptofauna with the degree of conservation of each site.As the identification of the cryptofauna progressed, many new distributional records of species were obtained.In this report we present 19 new records of isopods for the Mexican Caribbean coast.Photographs of each of the 19 species are also presented because for most of them just the drawings of the original description are available.

MATERIALS AND METHODS
The study was conducted in the Puerto Morelos Reef National Park (PNAPM), Quintana Roo, Mexico, which is a section of the Mesoamerican Reef (Figure 1).Three sites were selected: 1) Bonanza (20°57ʹ58ʺ N, 086°48ʹ27ʺ W), in recovery, located in the northern section of the SCUBA equipment, 3 kg of coral rubble were sampled at each site at three depths: shallow, 2-3 m; medium, 6-7 m; and deep, 10-12 m.Samplings were conducted in March, May, August, and November 2013, and January 2014, under SAGARPA (Agriculture, Natural Resources and Fisheries Secretariat) collecting permit DGOPA.00008.080113.0006granted to F. Alvarez.
Samples were sorted in the laboratory.All organisms marine park, now closed to recreational activities after being heavily impacted; 2) Puerto Morelos (20°52ʹ50ʺ N, 086°51ʹ02ʺ W), conserved, in the central portion of the marine park, is in good condition although it is adjacent to the town of Puerto Morelos; and 3) Jardines (20°50ʹ20ʺ N, 086°52ʹ41ʺ W), degraded, it lies the southern section of the park in front of large resorts and golf courses with a heavy sediment load (Figure 1).Using were extracted from the coral matrix, the remaining washings sieved through a 0.5 mm mesh, and preserved in 70% ethanol.The identification keys used were Menzies and Glynn (1968), Kensley (1984a), Kensley and Schotte (1989), and Müller (1989, 1992, 1993).The list of species follows the taxonomic arrangement by Ahyong et al. (2011).Specimens were sexed and their total length measured in millimeters.Specimens of less than 2 mm in total length were photographed in an Axio Zoom V16 Zeiss microscope, and larger specimens in a Z16 APO-A Leica microscope.All specimens are deposited in the National Crustacean Collection (CNCR) of the Institute of Biology, National Autonomous University of Mexico (UNAM).
Remarks: Twenty-four individuals have been identified; 14 of them came from the May sampling at Bonanza.The two examined specimens agree well with the original description, although one (Figure 2a) presents slight variations: a more elongated habitus and a subacute pleotelson.Gnathostenetroides includes two species: G. pugio and G. laodicense Amar, 1957 from the Mediterranean Sea (Fresi et al. 1980).
Remarks: The species was previously known only from Belize, so the present record increases its distribution 470 km to the north.The main characteristic that identifies this species is the presence, in live or freshly captured organisms, of two pigmented bands one on the head and one on pereonite IV.
Remarks: The specimens agree with the diagnosis.Kensley (1994: 325) reported some differences in relation to the color pattern of two male syntypes from Bermuda: "faintly reticulate over entire body, strong dark brown pigment on most of cephalon and pereionite 4".The specimens from the PNAPM have a brown pigmentation over the full body.Pigment patterns presumably have some camouflage function in reef rubble habitats (Kensley et al. 1997).
Remarks: Apparently few specimens (6) of this species have been collected.This species could be confused with one of three West Indian species that form a complex, particularly if mature males are not available and the shape of the carpus and propodus of pereopod I is not examined carefully.These species are H. stebbingi Richardson, 1902 from Bermuda;H. occidentale Hansen, 1904 from St. Thomas, West Indies;and H. antillense Hansen, 1904 from the West Indies.In the male of H. spathulicarpus the carpus of pereiopod I is apically rounded (Kensley 1984a); in the specimen from the PNAPM the carpus is more oval shaped than that of the original description.
Remarks: This species was previously classified as Apanthura magnifica due to a considerable confusion regarding the status of the genera Apanthura and Amakusanthura (Poore and Lew Ton 1988).The main features that distinguish these genera, in the case of females, are for Apanthura: pleonites 1-5 dorsally indistinguishable, except in some males; and for Amakusanthura: pleonites, except 4-5, distinguished by dorsal grooves, rarely 1-5 indistinguishable (Poore and Lew Ton 1988).
Remarks: Amakusanthura signata can be easily distinguished from all the other species of this genus by the presence of chromatophores on the cephalon, pereonites and pleon.A. signata and A. magnifica have been previously recorded in the Gulf of Mexico (Kensley and Schotte 1989).There are other three species in the Caribbean Sea (Müller 1992).
Remarks: The present record extends the distribution of the species to the northwestern Caribbean.This species was originally described in the genus Venezanthura Kensley (1978), restricted to the southern Caribbean (Kensley and Schotte 1989).The other species of Cortezura is the type species of the genus, C. penascoensis Schultz, 1977, from the Gulf of California in Sinaloa, Mexico.
Remarks: Mesanthura bivittata is the fourth species of the genus recorded for the Mexican Caribbean.All species of the genus have different color patterns, usually species-specific, pigment is persistent in alcohol preserved organisms (Kensley and Schotte 1989).The specimen collected shows the characteristic two dark dorsal bands on each segment.
Remarks: The specimen reported here represents the first record of the species from Mexico, since the description made by Kensley (1984a).There are eight species in the world, from the Mediterranean Sea, Indian Ocean, Florida Middle Grounds and Gulf of Aden (Kensley and Schotte 2000).The other known western Atlantic representative is P. tanaiformis Hooker, 1985, which was reported from Quintana Roo by Markham et al. (1990).
Remarks: A single specimen of the species was found during the study, expanding the distribution of the species 480 km to the north from Carrie Bow Cay, Belize.The genus contains 30 species, two of them from the Caribbean Sea, E. petrensis and E. teri (Kensley and Schotte 1989).
Remarks: Calyptolana hancocki is an easily recognizable species due to the elliptical shape of the habitus; the endopod of pleopod I is longer and broader than the exopod.It is moderately abundant in the study area, 12 females have been found.
Remarks: The morphology of our specimen fits well the original description, the chromatophores and the shape of the pleotelson and uropods are similar to those of the specimens from Belize (Kensley 1984a).
Remarks: This new record extends the range of G. beethoveni towards the northern Caribbean Sea.The species has been reported to depths of 95 m (Kensley and Schotte 1989).The species can be easily distinguished by the presence of 4 projections in the frontal border of the head.All current descriptions of gnathiid isopods are based on the morphology of free-living adult males; but their juvenile stages called "praniza larvae" a protelian ectoparasite that feed on fish host blood, limph or mucus, can be abundant in some areas and cannot be identified (Farquharson et al. 2012).Müller, 1988 (Figure 3f) Material examined: Male, 2.7 mm; Puerto Morelos (medium); 6 May 2013; CNCR 30559.

Gnathia vellosa
Distribution: Colombia, Isla de Morro Grande, Santa Marta, 25-30 m (Müller, 1988;Kensley and Schotte 1994).Remarks: The present record increases the geographic distribution toward the northern Caribbean Sea.This species is related to Gnathia virginalis in having three projections at the anteromedial border of the cephalon, which along with the two free anterior pereonites have a granular surface.The two species can be distinguished as follows: in G. vellosa pereonites 5-6 are much narrower than the cephalon in dorsal view and the distal end of the mandible bears an acute larger tooth, in G. virginalis pereonites 5-6 are as wide as the cephalon and all teeth on mandible are of approximately the same size.Monod, 1926 (Figure 3g)
Remarks: As stated above, G. virginalis seems to be closely related to G. vellosa, additional differences are: G. virginalis has a body size larger than G. vellosa whose mandibular carina is distally notched, and rounded in G. virginalis (Kensley and Schotte 1989).
Remarks: The genus Exosphaeroma Stebbing, 1900, contains five Caribbean species.Our specimen agrees with the description in having the posterior margin of the pleotelson faintly trilobed, and three low rounded tubercles anteriorly.Our record is the first for the Caribbean Sea since the original description from a single specimen, which has since been lost, so the true generic placement of this species is thus undetermined and full description awaits the finding of more material (Kensley and Schotte 1989).

Remarks:
The new records included in this study extend the range of G. barbarae to the western Caribbean Sea.This species appears to be common, 82 specimens have identified in our samples.The characters that identify the species are pleonite 5 with three dorsal tubercles, exopod of male uropod tubular and longer than pleon.Males with a frontal lamina expanded into ventrally directed beak-like process (Menzies and Glynn 1968;Kensley and Schotte 1989).

DISCUSSION
The existing records of isopods for the Mexican Caribbean coast combined account for 51 species (Markham et al. 1990;Barriga and Briones 1992;Campos-Vázquez 2000;van Tussenbroek and Brearley 1998;van Tussenbroek et al. 2012), but with our new records, the total number rises to 70 species.This number is likely to increase in the near future as the results of several ongoing investigations become available.
Geographically, the southern section of the Mexican Caribbean coast has been only superficially studied and will probably yield records of many more species when sampled thoroughly.Few records of isopods are available for the coast of the Sian Ka'an Nature Reserve, which occupies the central portion of the Quintana Roo coast, and from the southern portion of the state from Majahual to Xcalak.These two areas of central and southern Quintana Roo, where relatively undisturbed sections of the Mesoamerican Reef are found, should be surveyed to complete the inventory coastal peracarid species.
Most of the available records of isopods in the region are from the intertidal zone, and few samples come from deeper zones.This study shows that the coral rubble that collects at depths ranging from 2 to 12 m along the Mesoamerican Reef is a species-rich substrate that needs to be studied further.Some groups of isopods could be specially adapted to this type of substrate.Kensley (1984b), while studying the isopod species composition from coral rubble at Carrie Bow Cay, Belize, noted that anthuridean diversity was high.He considered that the slender and cylindrical body of anthurids is especially well suited to inhabit the interstices of this substrate.In this study, seven species of anthurids were recorded supporting Kensley's observations.Kensley's monograph and book on Caribbean isopods (Kensley 1984a;Kensley and Schotte 1989) remain the two most important accounts of this fauna for the region.As is the case with many other invertebrate groups, isopods are highly diverse and needs to be included in biotic surveys and could provide indicator species for monitoring ecosystem health.

Figure 1 .
Figure 1.Map of the Puerto Morelos Reef National Park, Quintana Roo, Mexico, showing the collecting sites for this study: Bonanza, Puerto Morelos and Jardines.MPA stands for "Marine Protected Area".