Terrestrial Isopoda ( Crustacea , Oniscidea ) from the coasts of Costa Rica , with descriptions of three new species

Seven species of terrestrial isopods are recorded from the coasts of the Pacific and Caribbean sides of Costa Rica. Three species (Buchnerillo neotropicalis, Hawaiioscia nicoyaensis and Trichorhina biocellata) are described as new and two species (Tylos niveus and Armadilloniscus cf. caraibicus) are newly recorded from the country. The poorly known species T. niveus is also illustrated. At present the total number of terrestrial isopod species recorded from Costa Rica is 30. Interestingly four typical littoral halophilic species (Ligia baudiniana, Tylos wegeneri, T. niveus and A. cf. caraibicus) are present on both the Pacific coast of Costa Rica and on the coasts of the lands encompassed by the Caribbean Sea. With the sole exception of A. cf. caraibicus, no morphological differences could be detected from the Pacific and Caribbean populations of those species. Rev. Biol. Trop. 66(Suppl. 1): S187-S210. Epub 2018 April 01.

Up to date, the diversity of Costa Rican terrestrial isopods is poorly known.Only 25 species in 16 genera and 10 families are presently recorded, numbers that are certainly very small for a tropical country like Costa Rica.Many records are very old, mainly dated in the first half of 1900 (Richardson, 1910(Richardson, , 1913;;Arcangeli, 1927Arcangeli, , 1930Arcangeli, , 1957;;Van Name, 1936), while only the families Philosciidae and Scleropactidae have been recently revised by Leistikow (1997aLeistikow ( , 1997bLeistikow ( , 1998Leistikow ( , 2000aLeistikow ( , b, 2001) ) and Schmidt (2007).However, all the records come from sporadic collections.Only few records are known for most of the forested areas and only two species (Ligia baudiniana Milne Edwards, 1840 and Tylos wegeneri Vandel, 1952) were reported from the coasts of the country.
This paper deals with recent collections of Oniscidea from both the Pacific and Caribbean coastal areas of Costa Rica, and includes the descriptions of three new species and two new records for the country.

MATERIALS AND METHODS
The specimens included in this paper have been collected in November 2015 on both sandy and rocky coasts of the Pacific side of Costa Rica.Also included are littoral terrestrial isopods deposited in the collection of the Museo de Zoología, Universidad de Costa Rica (MZUCR), San José.Specimens were collected by hand and stored in 75 % ethanol.The geographic co-ordinates of the locations were taken using WGS84 datum.Identifications are based on morphological characters.For each new species the material examined, description, etymology and remarks are given.For each species already recorded from Costa Rica the bibliographic references, material examined, distribution and remarks (when necessary) are included.Some poorly known species have been illustrated to facilitate future recognition.The taxa are illustrated with figures prepared with the aid of a camera lucida mounted on Wild M5 and M20 microscopes and digitally drawn using the method by Montesanto (2015Montesanto ( , 2016)).For some species pictures were taken with a Scanning Electron Microscope Hitachi S-3700N.
Distribution: Atlantic and Pacific shores of the Americas from Florida to Brazil and from California to Ecuador, including Galapagos Islands (Schmalfuss, 2003).
Remarks: At present, this is the only species of Ligia recorded from both coasts of Costa Rica.The species has been fully redescribed and illustrated by Leistikow (1997a).
Remarks: Tylos wegeneri was recorded from Puntarenas by Schultz (1983).This is the only record of this species for the Pacific coast, while the species seems to be widespread in the Caribbean Sea.However, no records from the Caribbean coast of Costa Rica are known.For a description and figures of this species see Vandel (1952) and Schultz (1970).Budde-Lund, 1885 Figs. 1, 2
Remarks: The main characters of this species are illustrated in Figs. 1 and 2 to confirm its identification and facilitate future recognition.For a complete list of synonyms of this species see Schmalfuss & Vergara (2000).This is the first record for the Pacific coast.
Additional material: 2 ♀♀ used for scanning microscope analysis, same data as holotype.
Etymology: The name of the species refers to the localities of collection of the species, the Neotropical Region.

Remarks:
The new species is included in Buchnerillo since it shows all the characters of the genus: small size; animal able to toll up into a perfect ball; endoantennal conglobation; dorsal surface tuberculated; cephalon with a wide frontal shield; pleonite 3 with epimera reduced; telson semicircular covering the uropods in dorsal view; antenna short and stout with a flagellum of three articles; male pleopod 2 with distal article flagelliform.Up to date, only two species of Buchnerillo are known: B. litoralis Verhoeff, 1942 andB. oceanicus Ferrara, 1974.The former is known from the shores of the Mediterranean Sea and Madeira (Schmalfuss, 2003); a record of a female specimen from Florida Keys (Paoletti & Stinner, 1989) is very doubtful and the identification needs confirmation.The latter is presently known from Somalia (Ferrara, 1974) and the Maldives (Taiti, 2014).Buchnerillo neotropicalis n. sp.differs from both species in the presence of a schisma on the pereonite 1 with inner lobe distinctly protruding backwards, whereas in B. litoralis and B. oceanicus a small rounded ventral lobe is present at the postero-lateral corners, not protruding backwards.It also differs from B. litoralis (see redescription in Vandel, 1960) in having the cephalon with frontal shield grooved, larger eyes (4 ommatidia instead of 1 -2), dorsal tubercles more prominent and male pleopod 1 endopod with distal part thicker and straight; from B. oceanicus in the frontal shield with lower margin sinuous on both sides instead of regularly curved.
The systematic position of genus Buchnerillo is still uncertain.It was included by Vandel (1960) in the section Synocheta and family Buddelundiellidae (now a subfamily of Trichoniscidae).Tabacaru (1993) recognized that the genus could not belong to the Synocheta and Schmalfuss (2003) included it into the higher Oniscidea (the Crinocheta) and hypothesised that the genus might belong to the family Detonidae, close to the genus Armadilloniscus.
According to the maxillular endite bearing only some apical setae without penicils, it might also be related to the family Olibrinidae.However, since no safe conclusion can be reached with morphological characters, we still maintain the genus as incertae sedis as proposed by Taiti & Ferrara (1991).A molecular analysis might be useful to clarify the family placement of Buchnerillo.Material examined: 1 ♀ (MZUF 9687), 1 ♀ used for scanning microscope analysis, Playa Pita, S of Tárcoles, Puntarenas, 9°44'32.9"N and 84°37'53.0"W, beach under logs, 27.XI.2015,leg.S. Taiti, J.A. Vargas & R. Vargas.
Remarks: The two female specimens here examined are morphologically very similar to Armadilloniscus caraibicus described by Paoletti & Stinner (1989) for the Caribbean coast of Venezuela.The main characters of the Costa Rican specimens are shown in Fig. 7.They show the same disposition of dorsal tubercles as those from Venezuela (see Figs. 10 and 11 in the original description by Paoletti &Stinner, 1989 andFigs. 32 and33 in Schmidt, 2002) but they are less developed.Since we have examined only 2 females, we only tentatively identify them as A. cf.caraibicus.
Etymology: The name of the species refers to the Gulf of Nicoya, where Playa Pita is located.
Remarks: The new species is included in the genus Hawaiioscia since all the most important characters (number and position of noduli laterales, maxillular teeth, penicil on maxillipedal endite, uropod and shape of male pleopod) correspond to the definition of that genus (see diagnosis in Taiti & Howarth 1997)      new species is readily distinguishable from the Hawaiian species by the pigmented body, the eye well developed and in having the molar penicil of the mandible semidichotomized, instead of simple.For this last character, the new species shows closest affinities with H. rapui from which it mainly differs in having larger eyes (19 -20 instead of 8 ommatidia) and in the shape of the male pleopods 1 and 2. Additional material examined: 1 ♂, 1 ♀, used for scanning microscope analysis, same data as holotype.
Etymology: Latin: bi = double + ocellatus = having eyes.The name refers to the eye consisting of two ocelli of the same size.
Remarks: The new species belongs to the tomentosa-group of Trichorhina characterized by the presence of two noduli laterales per side on the pereonite 7.This group includes with certainty T. tomentosa (Budde-Lund, 1893), T. heterophthalma Lemos de Castro, 1964, both widespread in the tropics, and T. guanophila Souza-Kury, 1993 from Brazil.The new species is readily distinguished from all these species by the eye consisting of two ommatidia of equal size (one in T. tomentosa, two unequal ommatidia in T. heterophthalma, and five in T. guanophila); from T. guanophila also in the male pleopod 1 exopod wider than long.Two more species of Trichorhina are recorded from Costa Rica by Arcangeli (1930): T. giannellii Arcangeli, 1929, known also from Cuba, and T. marianii Arcangeli, 1930.From their original descriptions no information is present on the number and position of the noduli laterales, so we do not know if they belong to the tomentosa-group.Trichorhina biocellata n. sp.differs from these two species in the eye with only two ommatidia (four or five in T. giannellii and 10 in T. marianii).

DISCUSSION
In the present study seven species of terrestrial isopods are recorded from sandy and rocky shores of both coasts of Costa Rica.Three species (Buchnerillo neotropicalis, Hawaiioscia nicoyaensis and Trichorhina biocellata) are described as new and two species (Tylos niveus and Armadilloniscus cf.caraibicus) represent new records for Costa Rica.The total number of Oniscidean species presently known from Costa Rica increases from 25 to 30 (Table 1).
Six species are strictly littoral, halophilic: L. baudiniana, T. wegeneri, T. niveus, B. neotropicalis n. sp., A. cf.caraibicus, and H. nicoyaensis n. sp.All these species, with the exception of H. nicoyaensis and B. neotropicalis, occur on both the Pacific and Caribbean coasts of Costa Rica or in other countries along the Atlantic coast of the Americas.No morphological differences could be detected from the Pacific and Caribbean populations of these species; only A. cf.caraibicus from Playa Pita on the Pacific coast showed small differences in the less developed dorsal ornamentation, even if of the same type, from the original specimens described from the Caribbean coast of Venezuela.It will be quite interesting to check both the Pacific and Caribbean populations of these five species with molecular markers to see if there is a criptic diversity between them, as revealed in other littoral isopods, e.g. in Excirolana braziliensis Richardson, 1912, Cirolanidae (Hurtado et al., 2016), considering that the isthmus of Panama was definitely closed 2.8 Ma (O'Dea et al., 2016).

ACKNOWLEDGEMENTS
We express our sincere thanks to Rita Vargas, Curator of Crustaceans (MZUCR), and to Jeffrey Sibaja for their invaluable help in collecting part of the material here treated.We also thank Rafael Loáiciga for technical assistance with the Scanning Electron Microscope housed at CIEMIC, UCR.S.T. wishes to thank the Centro de Investigación en Ciencias del Mar y Limnlogía (CIMAR) and the University of Costa Rica for their invitation to give a talk and do research in Costa Rica at the end of 2015.Field trips and SEM access were facilitated by projects UCR-VI-808-B3-113 The benthos of Punta Morales, and UCR-VI-808-B4-117 Ecology of beaches and rocky shores of Costa Rica, both with J. Sibaja as Principal Investigator.