New records of marine planktonic invertebrates from the Caribbean coast of Costa Rica

The coral reef at Cahuita National Park in the Caribbean coast of Costa Rica represents very diverse marine ecosystem. Most of this diversity knowledge has been the result of benthic surveys, while very little is known from pelagic studies. A zooplankton survey sampling was conducted monthly from September 2010 to August 2011, finding new records of marine invertebrates: 32 for the Caribbean coast of Costa Rica, seven for Costa Rican water and 16 for the Caribbean coast of Central America. These reports include the hoplitomella larva of the sponge Thoosa sp., larval stages of three lophophorates, seven families, five genera and six species of polychaetes, a juvenile of the lancet Branchiostoma (Phylum Chordata, Subphylum Cephalochordata) and four pelagic chordates. Analyzing the zooplankton of Cahuita, is an essential approach to studying not only the diversity, but also enhances the possibility of better understanding the ecological goods and services that the coral reef can provide. Rev. Biol. Trop. 66(Suppl. 1): S66-S82. Epub 2018 April 01.

Coral reefs are the most diverse marine ecosystems, with an estimate of as many as 9 million species worldwide (Plaisance, Caley, Brainard, & Knowlton, 2011;Fisher et al., 2015).The Caribbean region is not the exception, with over 12 000 species in all marine realms (Miloslavich et al., 2010).Most of the reported diversity lies on the benthic fauna, like so many marine habitats (Angel, 1993).But a significant portion is also on the pelagic realm, which harbors a vast diversity of fish and zooplankton (Suárez-Morales & Rivera, 1998).Coral reef zooplankton includes holoplanktonic (e.g.microcrustaceans, appendicularians, chaetognats), meroplanktonic (e.g.marine invertebrate larvae and ichthyoplankton) or epibenthic forms (e.g.microcrustaceans) (Emery, 1968;Glynn, 1973).The species records for these components of zooplankton are being understood in combination with DNA barcoding and phylogeographic studies to better assessed the dynamics of the planktonic communities (Bucklin et al., 2010).
In the Caribbean coast of Costa Rica, most of the coral reef studies have focused on benthic fauna and reef fishes (Cortés & Jiménez, 2003;Fonseca & Gamboa, 2003).These studies had emphasized the fringing reef at Cahuita National Park as having relatively low diversity, due to siltation and anthropogenic impacts on the coral reef (Cortés & Risk, 1985;Cortés, Jiménez, Fonseca, & Alvarado, 2010).Morales-Ramírez & Murillo (1996) suggested that this degradation also affects the meroplankton, presumably reducing the spawning events, feeding or swimming behavior of larvae.Meroplanktonic forms are of interest, because they could contribute to the benthic diversity, connectivity and dispersal of coral reef organisms (Heidelberg, Sebens, & Purcell, 2004).Here, we present new records of marine invertebrates represented by meroplankic and holoplanktonic organisms, collected from the coral reef of Cahuita National Park, Caribbean coast of Costa Rica.We present these new records across a variety of invertebrate clades, to highlight the diversity of groups that have been underrepresented or unnoticed by performing benthic surveys.

MATERIAL AND METHODS
From September 2010 to August 2011, two 5 min horizontal tows were done at six stations in Cahuita's coral reef (either between 6:00-10:00 or 12:00-17:00) (Fig. 1, Table 1).Once a month, two samples of zooplankton were collected using a WP net 0.47 m in diameter and a 200 µm mesh, attached with a calibrated flow meter and a buoy to maintain the net at approximately 1 m depth.Samples were fixed with a 4 % v/v formaldehyde in seawater, and transferred to 70 % ethanol for preservation.Subsamples of 2 ml were sorted and quantified until reaching a minimum of 400 zooplankters.Specimens were separated by group; unknown meroplanktonic and holoplanktonic specimens were sorted from the sample for taxonomic analysis.Here we report the new records for the Caribbean coast of Costa Rica.Annelids were deposited in the Museo de Zoología, Universidad de Costa Rica (MZ-UCR).

RESULTS
We report in this study the occurrence of the larval forms of 13 invertebrate taxa, including an hoplitomella larvae of the boring sponge Thoosa, "lophophorates" larval stages: an actinotroch of phoronids, ciphonaute of bryozoans and lobate of brachiopods.We also report seven families (six as larval stages and the remaining as adults or epitokes), five genera and six species of polychaetes as new records for the Caribbean coast of Costa Rica.Of those polychaete families found, only adult stages of Amphinomidae, Sabellidae, Spionidae and Syllidae were reported previously for this location (Dean 2009(Dean , 2012(Dean , 2017) ) (Table 2).Unidentified larvae of echinoids and ophiurids, as well as unidentified larvae of mollusks Remarks: Larval specimens have strongyles-like plates, characteristic of the hoplitomella larvae of the astrophoridean sponge Thoosa (Maldonado & Berquist, 2002;Bautista-Guerrero, Carballo, & Maldonado, 2010).These larva lack cilia and have the characteristic spicules discostrongyles, and radiating styles.Thoosa sponges are viviparous, and use the radiating styles to get free from the parental tissue to the water column, where the styles get a buoyancy function (Bautista-Guerrero et al., 2010).

May
Jun.
Remarks: Cyphonautes larvae belonging to the gymnolaemate bryozoans were found in all the stations in most of the months sampled.These larvae have a lateral compressed triangular body bearing an apical sense organ with few cilia and a ciliated corona on the opposite side (Temkin & Zimmer, 2002).Ávila-de Tábares et al. ( 2007) also reported cyphonautes larvae for the Colombian Caribbean.
Seven species have been reported for the Caribbean (Salazar-Vallejo, 1996).Magelona pettiboneae Jones, 1963 and Magelona riojai Jones, 1963 reported from Belize, are the nearest species to Costa Rica (Dean, 2009).
Remarks: This family has a truncate anterior end, with a head consisting of keel between two nuchal slits (Salazar-Vallejo & Díaz-Díaz, 2009).18 genera and 24 species are reported for the Caribbean (Salazar-Vallejo, 1996).Adults of Clymenella sp. and Isocirrus longiceps (Moore, 1923) have been found in the Gulf of Nicoya, Pacific coast of Costa Rica (Dean, 2009).
Remarks: Adult with a median antenna in the prostomium, without eyes.Branchiae starts at the 4 th setiger.Winged capillary chaetae on the anterior, and without wings on the posterior.Neurochaetae with wide hooks, curved spiniform (Solís-Weiss, 1996).This species had been recorded for deep benthic waters from Venezuela (Bone & Chollett, 2005).
Remarks: Trochophores and metatrochophores are frequently found in zooplankton surveys, because a planktotrophic or lecithotrophic larvae are present in most of the reproductive strategies of Spionidae (Wilson, 1991).Most of the nectochaetes have two pair of short or long palps and two or three pair of eyes (Plate & Husemann 1994).Scolelepis (Scolelepis) squamata (O.F. Müller, 1806) was recorded for Cahuita, and it is the only spionid for the Caribbean coast of Costa Rica (Dean, 2009) Remarks: Palps not so well developed.Head appendages not articulated.Ventral cirri absent (Góngora-Garza, 2009).Autolytoids are rare in the plankton, most in the form of stolons.The collected specimen belongs to a male stolon or "polybostrichus", with a bifid antennae on the front of the head and three posterior horns (Franke, 1999).Allen (1957) found both male and female stolons at La Parguera, Puerto Rico.There are three genera and 11 spp. of this subfamily in the Greater Caribbean (Góngora-Garza, 2009).
Remarks: Eversible pharynx, armed without a complete trepan or a median dorsal tooth.Eight species are recorded for the Greater Caribbean (Góngora-Garza, 2009;Dean, 2012).Odontosyllis luminosa San Martín, 1990 and Odontosyllis twincayensis Russell, 1989 from Belize, are the closest to the Caribbean coast of Costa Rica (Dean, 2009).
Remarks: Thoracid uncini with long shaft, abdominal unicni with short shaft (Harris et al. 2009).Two genera and five species have been reported for the Caribbean region (Solís-Weiss, Londoño-Mesa, & Hernández-Alcántara, 2009).Rouse & Pleijel (2001) and Garrafoni & Lana (2008)  Remarks: The presence of a gonad on each lateral site of the body confirms that the specimens belong to Branchiostoma (Poss & Boschung, 1996).However, the lack of well-defined myotomes or segments of the dorsal storage chamber, reflects their juvenile stage, which inhibits the clarification to a species level.
Remarks: Specimens presented a compact trunk and muscular tail.Postcardial caecum joins the genital wall of the esophagus (Esnal, 1999).The most abundant appendicularian in the Caribbean (Castellanos, Suárez-Morales, & Morales-Ramírez, 2009).As well as the Fritillaria species, they are found throughout the Greater Caribbean and the South Atlantic (Esnal, 1999), but this is the first report for the Caribbean of Central America, after the genus Oikopleura was reported in the San Blas Archipielago in Panama (D'Croz, Robertson, & Martínez, 1999) Remarks: With a barrel form, Thaliacea is characterized by an alternation of asexual (oozooids) and sexual (blastozooids) generations (Esnal, 1996).Oozooids have nine muscular bands and blastozooids have eight, in the doliolids (Esnal & Daponte, 1999).In Cahuita, both generations of Doliolum nationalis were found.Specimens have a gill-septum that extended from the muscular band II to the muscular band V and VI (Bone, 1998).

DISCUSSION
The Caribbean coast of Costa Rica does not have as many species as other countries in the Caribbean and Western Atlantic (Cortés & Wehrtmann, 2005).However, it is considered the most diverse country of the region, in terms of the numbers of species related to the coastline length (Wehrtmann, Cortés, & Echeverría-Sáenz, 2009).
An example of this diversity is shown here with new records of a variety of developmental stages of important biogenic architects of the coral reef (Cocito, Ferdeghini, & Sgorbini, 2001), such as sponges, polychaetes and "lophophorates".In addition, unidentified larvae of echinoderms and mollusks were a large year-around component of Cahuita's zooplankton (Morales-Ramírez & Murillo, 1996).Apart from the meroplantonick forms, 13 new records of copepods (Morales-Ramírez, Suárez-Morales, Corrales-Ugalde, & Esquivel-Garrote, 2014), and the description of two new species of monstrilloid copepods: Monstrillopsis cahuitae Suárez-Morales & Carrillo, 2013and Cymbasoma alvaroi Suárez-Morales & Carrillo, 2013, were previously reported (Suárez-Morales, Carrillo-Baltodano, & Morales-Ramírez, 2013).Moreover, although highly abundant, only two records at the specific level of pelagic chordates were reported for the Caribbean of Costa Rica (Castellanos et al., 2009) until the present study.Reported here are four species of tunicates and one species of cephalochordates, which is likely an underestimate of their diversity and more species could be found in oceanic waters of the region.
Considering polychaetes, Miloslavich et al. (2010;Table S5) showed Costa Rica as having the lowest richness on the South-Western Caribbean ecoregion (the other four are: Western Caribbean, Southern Caribbean, Greater Antilles and Eastern Caribbean), the ecoregion with the lowest polychaete richness.This trend was also seen by Dean (2009Dean ( , 2012Dean ( , 2017) ) who argued that this discrepancy is due to the low sampling effort especially along the Caribbean coasts of Nicaragua and Costa Rica.
In the present study, we increase the knowledge concerning polychaete identification, but five specimens where only identified to the family level due to the lack of keys or diagnostic characters for the larval stages.Previously, 75 species across 22 families were reported from the Caribbean of Costa Rican (Dean, 2009(Dean, , 2012(Dean, , 2017)).Glycera oxycephala Ehlers, 1887, however, was reported for Moín, and have not been reported for Cahuita (Böggemann, 2002).The new records found in the present study raises the diversity of polychaetes up to 29 families, 74 genera and 81 species for the Caribbean of Costa Rica.These figures remain an underestimate, and a more careful revision of deposit material and adult surveys will reveal a larger amount of new reports (Bogantes-Aguilar, 2014).
The polychaetes reported here, either to family, generic or specific level have been reported for the Caribbean coasts of Mexico (Salazar-Vallejo, 1996), Belize (Young & Young, 1982), Panama (Fauchald, 1977), Venezuela (Liñero-Arana & Díaz-Díaz, 2011) and other countries of the region (Dean, 2012).This is expected, since the Caribbean region is connected by major currents, from southeast to northwest, in the Greater and Lesser Antilles, and to the opposite direction in the southern Central American coast (Centurioni & Niiler, 2003).This means that many coral reef invertebrates and fishes with a planktonic larva, could be distributed and shared throughout the region (Warner & Goodbody, 2005;Salas, Molina-Ureña, Walter, & Health, 2010), emphasizing the need for more studies of meroplankton and their role in population recruitment in the Caribbean of Central America.
Morales-Ramírez & Murillo (1996) mentioned that Cahuita might have low meroplankton diversity due to the degradation of the coral reef at Cahuita (Cortés et al., 2010).In addition, warmer waters during the 1982-1983 El Niño event (Cortés, Murillo, Guzmán, & Acuña, 1984) could have caused a mismatch between the availability of phytoplankton (González et al., 2000) and the right time for spawning of many sessile invertebrates (Przeslawski, Ahyong, Byrne, Wörheides, & Hutchings, 2008).Nevertheless, with the findings of the current study, including all the larval forms of echinoderms, the three larvae of lophoporates clades, and many polychaetes forms, we showed that Cahuita's coral reef may hold more diversity than previously thought.Even with a great diversity of marine invertebrate larvae, recruitment studies are still lacking to understand the population dynamics of the reef (Alvarado, Cortés, & Salas, 2004).
The present study fills a gap in the knowledge of planktonic communities of the Caribbean coast of Costa Rica (Cortés & Wehrtmann, 2005).Using the same methodology as Morales-Ramírez & Murillo (1996) with the inclusion of two more stations (Carrillo-Baltodano & Morales-Ramírez, 2016) had allowed the evaluation of the zooplankton in terms of abundance, biomass and diversity after 25 years.Many of the reports shown here, were present only at one station in a single month, while other were present yearround.The spatio-temporal dynamics of their presence correlate with abiotic variables during the year sampled (Carrillo-Baltodano & Morales-Ramírez, 2016).Looking into the zooplankton is an essential approach to studying not only the diversity, but also the trophic, biogeochemical and ecosystemic dynamics of the coral reef.The relevance of species or groups diversity exceeds the value of the taxonomic inventory, because it enhances the possibility of better understanding the ecological goods and services (e.g.tourism, fisheries) that it can provide, leading us to an improvement in its management and conservation (Mumby et al., 2008;Miloslavich et al., 2010).

ACKNOWLEDGMENTS
We thank Marco Corrales for the identification of the chordates.All sample collections were carried out with the permission from La Amistad-Caribe Conservation Area and Cahuita National Park administration.Funding was provided by the Vicerrectoría de Investigación, Universidad de Costa Rica (J.C. grant number 808-B2-044).

TABLE 2
New records of marine invertebrate fauna from the coral reef of Cahuita National Park.NR: new record; X: previously recorded; CR: Costa Rican waters; CarCR: Caribbean of Costa Rica; CarCA: Caribbean coast of Central America.

TABLE 2 (
Continued) mentions that only Liothyrella moseleyi (Davidson, 1878) member of the Class Rhynchonellata has been found offshore of Martinique, which makes the specimen of this study the first record of lingulate brachiopods for the Caribbean coast of Central America.
considered it a pelagic species.
consider Trichobranchidae as a subfamily of Terebellidae. .