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Ascidian diversity of Costa Rica, including new records

for the North Pacific

Kaylen González-Sánchez

1,2

; https://orcid.org/0000-0002-7208-9302

Bryan Flores-Alvarado

1,2

; https://orcid.org/0000-0003-2826-8810

Paula Montiel-Barrantes

1,2

; https://orcid.org/0000-0002-5945-8396

Gonzalo Gómez-Arce

1,2

; https://orcid.org/0000-0002-5200-0390

Juan José Alvarado

1,2,3

; https://orcid.org/0000-0002-2620-9115

1. Centro de Investigación en Ciencias del Mar y Limología (CIMAR), Universidad de Costa Rica, 11501-2060, San

José, Costa Rica; kaygs95@gmail.com, bryfloalv@gmail.com, mapamoba22@gmail.com, gongomeza@gmail.com,

juanalva76@yahoo.com

2. Escuela de Biología, Universidad de Costa Rica, 11501-2060, San José, Costa Rica.

3. Museo de Zoología, Centro de Investigación en Biodiversidad y Ecología Tropical (CIBET), Universidad de Costa

Rica, 11501-2060, San José, Costa Rica.

Received 30-I-2021. Corrected 23-IV-2021. Accepted 19-VII-2021.

ABSTRACT

Introduction: The class Ascidiacea has about 3 000 species, which fulfill various roles in the ecosystem, for

example, they filter high amounts of particles, and are shelter and food for other animals. Furthermore, the group

has a high number of invasive species reported. In Costa Rica, ascidians have been barely studied.

Objective: In this study, we aim to describe the diversity of ascidians in Costa Rica from new samplings in Área

de Conservación Guanacaste, North Pacific, and by compiling previous reports for the entire country in order to

improve the group’s state of knowledge.

Methods: Samples were collected during two field trips between 2018 and 2019, at six sites within the Gulf

of Santa Elena and three sites near the Murcielago Islands area. The specimens were dissected and analyzed

in detail to determine the species. All the identifications were compared with the available information from

literature and from museum collections. Literature, collections databases of the National Museum of Natural

History, Smithsonian Institution and the new material collected were used to create an updated taxonomic list.

Results: A total of eight species were obtained from 70 specimens. Of these, five are new reports for the country,

which increase to 22 species the total number reported for Costa Rica. The most common species was Rhopalaea

birkelandi, whose presence was higher in Santa Elena Bay.

Conclusions: This study improved the knowledge of ascidian diversity in Costa Rica. Polyandrocarpa anguin-

ea, reported for the first time, is considered invasive in other areas, which suggests the necessity of a continuous

monitoring of its population. It is necessary to include more areas of the country since almost all the reported

species come from the North Pacific; the diversity of ascidians from other parts of the country, especially the

Caribbean, is still unknown.

Key words: Ascidiacea; distribution; systematics; taxonomy; new reports.

González-Sánchez, K., Flores-Alvarado, B., Montiel-Barrantes,

P., Gómez-Arce, G., & Alvarado, J. J. (2021). Ascidian

diversity of Costa Rica, including new records for the

North Pacific. Revista de Biología Tropical, 69(Suppl. 2),

S234-S245. https://doi.org/10.15517/rbt.v69iS2.48318

https://doi.org/10.15517/rbt.v69iS2.48318

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Ascidians are the most diverse class within

the subphylum Tunicata, with around 3000

described species (Shenkar & Swalla, 2011).

The ascidians are characterized for having an

external tunic made up mainly of cellulose

(Abbott, Newberry, & Morris, 1997). The cur-

rent classification for the class divides them

into three orders, which are determined by the

internal structure of the branchial sac: Aplou-

sobranchia, Stolidobranchia y Phlebobran-

chia (Lahille, 1886). These organisms exhibit

solitary individuals or colonial forms, with

zooids with different structural and functional

relationships inside a colony (Moreno-Dávila,

2013). Ascidians inhabit many marine envi-

ronments, from the intertidal zone to abyssal

depths (Shenkar & Swalla, 2011). They mostly

feed by filtering organic matter and plankton

(Petersen, 2007).

This group serves as a substrate and/or

refuge for smaller organisms, it is also part of

the diet of marine turtles, such as Eretmochelys

imbricata. Besides, they are successful com-

petitors for primary substrate (Carrión-Cortez,

Canales-Cerro, Arauz, & Riosmena-Rodríguez,

2013; Darwin & Klebba, 2007; Fletcher, For-

rest, & Bell, 2013; Marin & Anker, 2008).

Ascidians are among the taxa with the

highest number of introduced species reported

(Evans, Erwin, Shenkar, & López-Legentil,

2017), which are transported principally as

macrofouling attached to the ships hull’s and

their larvae through ballast water (Lambert,

2002). Ascidians are successfully facing rough

predatory and environmental conditions (Lam-

bert, 2002; Lambert, 2007). It is crucial to set a

baseline in order to keep track of invasive spe-

cies and their effects, hereby the importance of

taxonomic knowledge of the group.

Despite their ecological importance and

usefulness, and being reported as abundant in

the rocky bottom of the North Pacific of Costa

Rica; few studies have been carried about

their taxonomy and ecology (Cortés, 2009;

Nova-Bustos, Hernández-Zanuy, & Viquez-

Portuguez, 2010; Tokioka, 1971; Tokioka,

1972). The ascidians identification involves a

very detailed, time consuming and specialized

process; demanding high taxonomic experience

and motor skills for delicate dissections and

preservation (Stefaniak, Lambert, Gittenberger,

Zhang, & Whitlatch, 2009; Turon, Casso, Pas-

cual, & Viard, 2020); which could have led to

the limited knowledge in the region. This study

aims to describe the diversity of ascidians in

Costa Rica, based on new samplings in the

North Pacific, previous reports in the literature,

and museum databases available online, in

order to improve and update the knowledge on

species diversity.

MATERIALS AND METHODS

Sites: Sampling took place on two field

trips: from July 1

to August 3

2018, and

from July 15

to July 19

2019. The samples

were collected at nine sites distributed in the

Área de Conservación Guanacaste (ACG, Gua-

nacaste Conservation Area) in Costa Rica’s

North Pacific (Fig. 1). This area has a seasonal

upwelling that goes along December through

April-May, which brings up cooler waters rich

in nutrients, helping keep an average superfi-

cial seawater temperature around 22°C (Alfaro

et al. 2012; Jiménez, 2001).

Sampling: The sampling focused mainly

on solitary organisms since previous studies

in this area have focused on colonial species.

Samplings were carried out at depths between

1 and 13 m on rocky bottoms by roving with

SCUBA gear, a metal spatula and/or a knife

were used to carefully remove the specimens.

Sampling in Bahía Tomas was carried out on

an artificial substrate (fish breeding cages) at 1

m depth. A chisel and mallet were used to break

up the substrate for specimens embedded in the

rock to avoid sample damage.

Sample processing: The collected speci-

mens were kept and transported in seawater,

then anaesthetized by adding a mixture of 70

% alcohol and dissolved menthol crystals.

This process can take several hours depend-

ing on the different morphological structures

that characterize each one of the three ascidian

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orders; being Stolidobranchia the one that takes

more time due to the strong musculature,

according to our observations. During this

period, small amounts of 70 % alcohol were

added every hour to start the preservation pro-

cess, without morphological alterations caused

by alcohol fixation.

For the taxonomic identification, it was

necessary to carry out a process of external

and internal dissection of the organisms. This

process began by opening the tunic with a cut

from the atrial siphon to the oral one using dis-

section scissors, cutting carefully to avoid deep

cuts that might cause internal structure damage.

This was followed by a cut of the body wall in

the same direction as in the previous cut. To

visualize the internal structures, Harris’s hema-

toxylin or Bengal Rose were used as a stain.

To finish, the pharynx was removed, allowing

the structures found inside to be observed.

Monniot, Monniot and Laboute (1991) and

Rocha, Zanata and Moreno (2012) keys were

used for taxonomic identifications, as well as

the original descriptions of the species and

taxonomic reviews of each species. Specimens

were deposited at the Museum of Zoology of

the University of Costa Rica.

Taxonomic list: Research on literature and

collections databases of the National Muse-

um of Natural History (NMNH), Smithsonian

Institution (https://collections. nmnh.si.edu)

were performed. Based on this information,

and the new material collected for the present

study in the North Pacific, an updated list of

both solitary and colonial ascidians species

present in Costa Rica was developed.

RESULTS

A total of eight species (70 specimens) were

obtained from the sampling, corresponding to

Fig. 1. Collecting sites in the Área de Conservación Guanacaste, North Pacific of Costa Rica. N.P.: North Pacific, C.P.:

Central Pacific and, S.P.: South Pacific.

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five genera, four families and three orders with-

in the class Ascidiacea. The species richness

was higher in Santa Elena Gulf (8 species) and

lower in the Murcielago Islands (4 species).

The most frequent species in both areas was

Rhopalaea birkelandi Tokioka, 1971 (Table 1).

In our sampling, we found three of the

17 species previously reported, plus five new

reports for the North Pacific area, totalling 22

species in Costa Rica (Table 2). From ascidians

previously reported, 16 belong to the North

Pacific and one to Puntarenas (Central Pacific).

SYSTEMATICS

In this section, we made a brief descrip-

tion of the eight species collected through our

sampling in Área de Conservación Guanacaste.

We only considered the most particular char-

acteristics of the species or characteristics that

have slight variations, mainly structure counts.

These variations do not produce any changes

in the taxonomic identity of the species and

these are mentioned in order to broaden the

known range in terms of the number of struc-

tures. The characteristics not mentioned in the

description match with the original description

of each species.

Subphylum Tunicata Lamarck, 1816

Class Ascidiacea Blainville, 1824

Order Phlebobranchia Lahille, 1886

Family Ascidiidae Herdman, 1882

Genus Ascidia Linnaeus, 1767

Ascidia sideralis Bonnet & Rocha, 2013

Material Examined: 14 specimens

(MZUCR-ASC-0066, MZUCR-ASC-0071,

MZUCR-ASC-0079, MZUCR-ASC-0081,

MZUCR-ASC-0089, MZUCR-ASC-0093).

Description: The specimens present a

greyish tunic, whose coloration can vary to

reddish and blue tones; characterized by the

presence of white dots that become more

abundant near the siphons and conspicuous

musculature on the right side of the body. The

individuals examined match with the original

description by Bonnet, Rocha and Carman

(2013); however, they present two remarkable

differences. Individuals (two) with only four

oral siphon lobes were found, thus expanding

the range reported in the original description

(from seven to eight lobes). The same situation

occurs for the oral tentacles. Ranges from 76

to 92 tentacles were reported in the literature,

but we found individuals with numbers ranging

TABLE 1

Ascidian species (Subphylum Tunicata, Class Ascidiacea) found in different locations of Área de Conservación

Guanacaste, North Pacific Costa Rica.

Species

Murciélago Islands Santa Elena Gulf

PI CS BLV BR BV MÑ PT TB LC

Ascidia sideralis

X X X X X

Ascidia sidneyensis

X X

Pyura lygnosa

X X X X

Pyura carmanae

X X X X X

Pyura bradleyi

X X

Microsmus cf. exasperatus

X X

Poliandrocarpa anguinea

Rhopalaea birkelandi

X X X X X X

PI: Puerta de la Iglesia, CS: Colorada Sur, BLV: Bajo La Vita, BR: Bajo Rojo, BV: Bajo Viejón, MÑ: Muñecos, PT: Pitahaya,

TB: Tomas Bay, LC: Los Cabros.

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from 35 to 72. Individuals belonging to this

species are quite abundant in the North Pacific

area (Fig. 2A).

Substrate: Rocky bottom.

Distribution: Panama (Bonnet et al., 2013)

and Costa Rica (this study, North Pacific).

Ascidia sydneiensis Stimpson, 1855

Material Examined: six specimens

(MZUCR-ASC-0072, MZUCR-ASC-0076).

Description: Individuals with pale greyish

tunic and characterized for having a distinctive

musculature, on the margin of the right side of

the body, muscle fibers project from the margin

to the interior without reaching the center. The

characteristics of the examined specimens are

consistent with the original description (Stimp-

son, 1855) and reports from Panama (Bonnet

& Rocha, 2011; Bonnet et al., 2013) (Fig. 2B).

Substrate: Artificial substrate.

Distribution: Australia (Stimpson, 1855),

Brazil (Granthom-Costa et al., 2016), Cuba

and Puerto Rico (Van Name, 1921), Guade-

loupe and Martinique (Monniot, 1985), Costa

Rica (this study, North Pacific), Panama (Car-

man et al., 2011), Colombia (Sluiter, 1898),

Mozambique (Monniot & Monniot, 1976),

Zanzibar (Traustedt & Weltner, 1891), South

Africa (Millar, 1962), India (Swami & Chap-

gar, 2002; Ali et al., 2009), Guam (Lambert,

2002), Virgin Islands, Belize, Mexico, French

Polynesia, Hawaii, Japan, Phillipines and

Papua New Guinea (https://collections.nmnh.

si.edu/search/iz/).

Order Stolidobranchia Lahille, 1886

Family Pyuridae Hartmeyer, 1908

Genus Pyura Molina, 1782

Pyura lignosa Michaelsen, 1908

Material Examined: five specimens

(MZUCR-ASC-0070, MZUCR-ASC-0074,

MZUCR-ASC-0084).

Observations: A thick and robust tunic

characterizes the collected specimens. The

siphons are both in the apical position and have

a globose shape with a greenish tonality, unlike

their body, which is orange. In these individu-

als, the longitudinal vessels extend at the end

of the folds near the esophagus. The observed

characteristics of the specimens match the

description provided by Michaelsen (1908) and

the review by Monniot (1994) (Fig. 2C).

Substrate: Rocky bottom.

Distribution: Costa Rica (this study,

North Pacific), Central Pacific (Michaelsen,

1908), Panama-Pacific (Carman et al., 2011),

Mexico (Gulf of California) (Van Name, 1931),

Majuro, Japan, Philippines (Nishikawa, 1984).

Pyura carmanae Rocha, 2019

Material Examined: 17 specimens

(MZUCR-ASC-0083, MZUCR-ASC-0085,

MZUCR-ASC-0090, MZUCR-ASC-0091,

MZUCR-ASC-0094).

Observations: The characteristics of these

individuals match with those given in the origi-

nal description of the species (Rocha & Counts,

2019). Three specimens differ in the position

of the siphons, since they are widely separated

one from each other: the oral in apical position

and the exhalant in a lateral position. One of

these three specimens has gonads only on the

left side of the body wall, larger than in other

specimens, and completely covering the first

intestinal loop. These three individuals could be

a different species, but related to P. carmanae.

However, two of these specimens did not pres-

ent gonads, so we could not make a satisfactory

comparison between the internal structures of

these three with the rest of the examined speci-

mens. We consider the use of genetic tools to

test this hypothesis. (Fig. 2D, Fig. 2E).

Although it has already been pointed out

by Rocha and Counts (2019), it is important to

mention that Tokioka (1972) described organ-

isms belonging to the species P. carmanae as

Pyura vittata. In this updated list we discard the

presence of P. vittata as part of the Costa Rican

marine fauna studied so far.

Substrate: Rocky bottom.

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Distribution: Panama (Rocha & Counts,

2019), Costa Rica (this study, North Pacific).

Pyura bradleyi Van Name, 1931

Material Examined: three specimens

(MZUCR-ASC-0075, MZUCR-ASC-0078,

MZUCR-ASC-0092).

Observations: The individuals examined

had an opaque tunic covered by sand, which

matches with the reported by Van Name (1931)

in the original species description. Furthermore,

when observing the internal structures, a strong

red coloration can be seen on the siphons and

the whole mantle has a reddish color. Under its

branched tentacles, red dots can be observed,

which are also present under the branchial sac.

Similar to that observed by Van Name (1931),

its dorsal lamina is divided into barbs and there

are six folds on each side of the body. Regard-

ing the original description, these specimens

showed a remarkable difference in terms of the

number of gonadal sacs. The original descrip-

tion indicates that there are about 50 elongate-

oval sacs per gonad; our specimens showed up

to 106 on the left side and 99 on the right side,

increasing the range for this characteristic (Van

Name, 1931). (Fig. 2F).

Substrate: Rocky bottom and artificial

substrate.

Distribution: Peru (Van Name, 1931),

Ecuador (Van Name, 1931) and Costa Rica

(this study, North Pacific).

Genus Microcosmus Heller, 1877

Microcosmus cf. exasperatus Heller, 1878

Material examined: seven specimens

(MZUCR-ASC-0077, MZUCR-ASC-0082).

Observations: Large individuals, up to

4.5 cm in length, with a dark reddish tunic,

the mantle has a mixture of light orange and

yellow. In general, the characteristics of the

examined specimens match with the original

description of the species (Van Name, 1945).

Furthermore, they match with the diagnosis

reported by Rocha, Bonnet, Baptista and Bel-

tramin (2012). However, we have not been able

to properly find the velum of these individuals

in order to check the presence and shape of the

spines, and therefore, to confirm the specimens

identification (Fig. 2G). It is the first time

that M. cf. exasperatus has been reported in

Costa Rica.

Substrate: Rocky bottom and artificial

substrate.

Distribution: Bermuda, U.S. (Florida),

Cuba, Jamaica, Haiti, Puerto Rico, Saint Thom-

as, St. Lucia, Guadalupe, Martinica, Granada,

Belize, Panama, Colombia, Aruba, Curaçao,

Venezuela, Brazil (Ceará to Santa Catarina),

Senegal, Sierra Leone, Liberia, Ghana, South

Africa (Rocha, Zanata and Moreno, 2012),

Israel, India (Ratnasingham & Hebert, 2007),

Mediterranean Sea, Atlantic Ocean, Indo-

Pacific (Rocha, Bonnet, et al., 2012) and Costa

Rica (North Pacific).

Family Styelidae Sluiter, 1895

Genus Polyandrocarpa Michaelsen, 1904

Polyandrocarpa anguinea Sluiter, 1898

Material examined: one specimen

(MZUCR-ASC-0086).

Observations: Grayish and translucent

colonies with a cartilaginous tunic; zooids

more than 1 cm long. The zooids had approxi-

mately 25 smooth tentacles of two interspersed

sizes and four folds on both sides of the bran-

chial sac, which coincides with that described

by Rodríguez (1977) and Rocha and Faria

(2005) (Fig. 2H).

Substrate: Rocky bottom.

Distribution: South Africa, Brazil,

Mozambique in the Eastern Atlantic, Mauritius

in the Indian Ocean, and in the Tropical Pacific

Ocean (Monniot, 1987), Martinica (Monniot,

2018), Panama (Carman et al., 2011), United

States (Florida) (Ratnasingham & Hebert, 2007)

and Costa Rica (this study, North Pacific).

Order Aplousobranchia Lahille, 1886

Family Diazonidae Seeliger, 1906

Genus Rhopalaea Philippi, 1843

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Rhopalaea birkelandi Tokioka, 1971

Material examined: 17 specimens

(MZUCR-ASC-0067, MZUCR-ASC-0068,

MZUCR-ASC-0069, MZUCR-ASC-0073,

MZUCR-ASC-0080, MZUCR-ASC-0087,

MZUCR-ASC-0088).

Observations: In the examined specimens

we noticed two different colors for the tunic:

pink and blue. Tokioka (1971) describes this

specie as solitary, however, we observed that

the blue individuals were linked under the sub-

strate. As for the pink individuals, we observed

that they are much more abundant. All the

specimens were found mainly on porous rocks,

where their tunic extends through the crevices,

up to about 10 cm.

Rhopalaea birkelandi has two body parts

separated by a thin and fragile peduncle. This,

added to the insertion of the tunic in the rock,

can lead to the separation of both sections dur-

ing the extraction and dissection process. Com-

paring the original description of the species

with our specimens, we noted that the peduncle

is not mentioned. On the other hand, the origi-

nal illustrations coincide with the morphology

that we found in the specimens whose peduncle

was damaged and consequently, the abdomen

and thorax separated. Because of this, we

believe that Tokioka may not have had access

to specimens of R. birkelandi in good condition

and thus, the description may be incomplete.

(Fig. 2I, Fig. 2J, Fig. 2K).

Substrate: Rocky bottom.

TABLE 2

Complete list of ascidian species reported for Costa Rica.

Order/Family Species Reported by

Aplousobranchia

Diazonidae

Rhopalaea birkelandi (Tokioka, 1971)

Tokioka, 1971, 1972; Nova et al,. 2010;

NMNH; this study

Rhopalaea abdominalis (Sluiter, 1898)

NMNH

Didemnidae

Didemnum cf. perlucidum (Monniot, 1983)

Roth et al., 2017

Didemnum moseleyi (Herdman, 1886)

Tokioka, 1972; Nova et al., 2010

Didemnun candidum (Savigny, 1816)

Tokioka, 1972

Lissoclinum caulleryi (Ritter & Forsyth, 1917)

Tokioka, 1972; Nova et al., 2010

Lissoclinum fragile (Van Name, 1902)

Tokioka, 1972

Diplosoma listerianum (Milne- Edwards, 1841)

NMNH

Polycitoridae

Cystodytes dellechiajei (Della Valle, 1877)

NMNH

Polyclinidae

Aplidium constellatum* (Van Name, 1902)

Tokioka, 1972

Polyclinum laxum (Van Name, 1945)

Tokioka, 1972

Phlebobranchia

Ascidiidae

Ascidia ceratodes (Huntsman, 1912)

Tokioka, 1972; Nova et al., 2010

Ascidia sydneiensis (Stimpson, 1855)

This study

Ascidia sideralis (Rocha, 2011)

This study

Stolidobranchia

Pyuridae

Microcosmus cf. exasperatus (Heller, 1878)

This study

Pyura bradleyi (Van Name, 1931)

This study

Pyura carmanae (Rocha, 2019)

This study

Pyura lignosa (Michaelsen, 1908)

Tokioka, 1972; this study

Styelidae

Botryllocarpa viridis* (Pizon, 1908)

Tokioka, 1972

Eusynstyela tincta* (Van Name, 1902)

Tokioka, 1972; Nova et al., 2010; NMNH

Polyandrocarpa anguinea (Sluiter, 1898)

This study

Styela canopus* (Stimpson, 1852)

Tokioka, 1972

*Species name has been modified according to WoRMS database.

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Distribution: Costa Rica (North Pacific)

(Tokioka, 1971; Tokioka, 1972; Nova et al.,

2010; this study), Panama (Carman et al., 2011)

and Mexico (Baja California Sur) (Ratnasing-

ham & Hebert, 2007).

DISCUSSION

Considering that ascidians have been

barely studied in Costa Rica, this research

shows the necessity of new sampling efforts to

increase the known diversity. The present study

reports for the first time the presence of five

species in the Costa Rican Pacific and delivers

an updated list of the 22 species of ascidians

reported for Costa Rica.

The species richness and abundance in

Santa Elena Gulf was higher than in Mur-

cielago Islands. Both regions are under the

effects of the seasonal upwelling phenomenon,

G. Microcosmus cf. exasperatus; H. Polyandrocarpa anguinea zooid; I. Rhopalaea birkelandi, pink specimen without tunic;

J. Rhopalaea birkelandi blue zooid, on the left side the abdomen, on the right side the thorax; K. Colony of R. birkelandi

with four blue zooids. Scale = 1 cm.

Fig. 2. Specimens collected in Área

de Conservación Guanacaste, North

Pacific of Costa Rica. A. Ascidia

sideralis; B. Ascidia sydneiensis

without the tunic; C. Pyura lignosa, D.

Pyura carmanae; E. Pyura carmanae,

a specimen that represents the group

that differs in morphology regarding

the tunic, siphons, and does not have

developed gonads; F. Pyura bradleyi;

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which affects the entire North Pacific region

(Alfaro et al., 2012; Rodríguez, & Morales,

2012). On the other hand, Santa Elena Gulf is

an important artisanal fishing point, in contrast

to the Murcielago Islands, which are within

the protected Marine Sector of the Área de

Conservación Guanacaste. Other studies have

reported a greater abundance of ascidians in

areas around human activity, which generates

movement of organic particles that constitute

food for ascidians and facilitate their growth

(Naranjo, Carballo, & García-Gómez, 1996).

The anthropic influence in Santa Elena Gulf

could explain a higher ascidian diversity.

Rhopalaeae birkelandi is the most com-

mon and abundant species in our study, simi-

larly, it has been reported as abundant and

conspicuous in the rocky reefs of the Pacific

of Central America (Tokioka, 1972). Nova and

colleagues (2010) also found this species as

the most abundant, reporting densities of up

to 32 individuals per m

in Cuajiniquil Bay.

The presence of vanadocytes and the high

acidity (pH < 2) of their tunic, mainly near the

siphons, can reduce epibionts and predation,

being abundant in sites with a high predation

rate (Stoecker, 1980).

Before this study, there were 17 ascid-

ian species reported for Costa Rica; from

these, 13 are colonial. We found only three of

the previous ascidians reported (R. birkelandi,

Pyura lignosa and Poliandrocarpa anguinea)

but our study was focused on the diversity

of solitary ones. This approach allowed us to

report five species of solitary ascidians for the

first time. It is noteworthy that we did not find

Ascidia ceratodes, despite being solitary and

having been reported as common in the area

(Nova et al., 2010).

The marine regions of Costa Rica are con-

sidered rich in terms of species diversity (Weh-

rtmann, Cortés, & Echeverría, 2009). In the

case of ascidians, there are reports for only one

region of the country, the North Pacific (Cortés,

2009). Most of the studies took place in that

region of Costa Rica or referred to individuals

collected in that area. Differences in sampling

effort, and not a low ascidian diversity in other

regions, can explain this lack of data. Costa

Rica’s ascidian species inventory is undoubt-

edly underestimated. In a close by area of

the Caribbean, Northwestern Panama, Rocha

and colleagues (2005) reported a total of 58

ascidian species, from which 14 were new to

science. In fact, we have observed the presence

of colonial ascidians in regions such as Cahuita

and Punta Uva, on the South Caribbean of

Costa Rica, without having the opportunity to

study them until now.

Among the ascidians reported in Costa

Rica, we find P. anguinea, a species that has

been introduced to many countries around

the world (Evans et al., 2017). This species,

native of Mozambique (Sluiter, 1989), has been

found in Brazil (Rodríguez, 1977), Panama

(Carman et al., 2011), Mauritius (Monniot,

1987), Martinique (Monniot, 2018) and the

Atlantic Ocean in the United States (Vil-

lalobos, Lambert, Shenkar, & López-Legentil,

2017). Some introduced species could become

invasive (Blackburn et al., 2011), changing the

ecosystems by modifying ecological relations

and even harming the survival of native species

(Evans et al., 2017; Molnar, Gamboa, Revenga,

& Spalding, 2008). Taking into account the

ability of P. anguinea to become invasive, we

recommend monitoring the population of this

species in the country.

In conclusion, new samplings in the North

Pacific and the compilation of previous reports

from the literature allowed us to extend the

known diversity of ascidians in Costa Rica,

updating the knowledge about this group. We

report five species for the first time and provide

a list that includes until now, 22 species in total,

the majority found in the North Pacific region.

Different sampling efforts, but not presumably

low ascidian diversity in other regions, suggest

the necessity of samplings along with other

places in the Pacific and the Caribbean, which

for the latter there are no reports. Future inves-

tigations should include colonial ascidians, the

use of molecular tools, and ecological studies

that can clarify the importance of ascidians,

and also monitor the impact of exotic species

in the area.

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Ethical statement: authors declare that

they all agree with this publication and made

significant contributions; that there is no con-

flict of interest of any kind; and that we fol-

lowed all pertinent ethical and legal procedures

and requirements. All financial sources are

fully and clearly stated in the acknowledge-

ments section. A signed document has been

filed in the journal archives.

ACKNOWLEDGMENTS

This research was possible thanks to the

BioMar-ACG project funded by the Guana-

case Dry Forest Conservation Fund (GDFCF).

Logistic support was provided by CIMAR,

Universidad de Costa Rica (Project: Biodiver-

sidad marina del Área de Conservación Gua-

nacaste, Costa Rica: Proyecto BioMar-ACG:

808-B9-508). The authors would like to thank

Yelba Vega, Gilbert Ampié and Fabio Que-

sada for the help provided during the collection

and processing of samples. Special thanks to

Rosana Rocha for all the support and advise

throughout the process.

RESUMEN

Diversidad de ascidias de Costa Rica, incluyendo

nuevos reportes para el área del Pacífico Norte

Introducción: La clase Ascidiacea tiene alrededor de 3 000

especies, las cuales llevan a cabo varias funciones en el

ecosistema, por ejemplo: filtrar altas cantidades de partí-

culas y servir de refugio y alimento para otros animales.

Asimismo, para el grupo se han reportado un gran número

de especies invasoras. En Costa Rica las ascidias han sido

poco estudiadas.

Objetivo: En el presente estudio buscamos describir la

diversidad de ascidias en Costa Rica a partir de nuevos

muestreos en el Área de Conservación Guanacaste, Pací-

fico Norte y mediante la recolección de reportes previos

para el país para así aumentar el conocimiento del grupo.

Métodos: Las muestras fueron colectadas en dos giras

entre el 2018 y 2019, en seis sitios en el Golfo de Santa

Elena y tres sitios cerca de las Islas Murciélago. Los

especímenes fueron disectados y analizados en detalle

para su identificación. Todas las identificaciones fueron

comparadas con la información encontrada en la literatura

y en colecciones de museos. Literatura, bases de datos de

la colección del Museo Nacional de Historia Natural de la

Institución Smithsonian y el nuevo material colectado, fue-

ron utilizados para crear un listado taxonómico actualizado.

Resultados: Se obtuvo un total de ocho especies del mues-

treo. De estas, cinco son nuevos reportes, incrementando el

total de especies reportadas en Costa Rica a 22. La especie

más común fue Rhopalaea birkelandi, cuya presencia fue

mayor en Bahía Santa Elena.

Conclusiones: Este estudio mejoró el conocimiento sobre

la diversidad de ascidias en Costa Rica. Polyandrocarpa

anguinea, reportada por primera vez, es considerada una

especie invasora en otras áreas, lo que sugiere la necesidad

de monitorear su población de forma continua. Es necesa-

rio incluir más áreas del país en futuros estudios puesto que

casi todas las especies reportadas provienen del Pacífico

Norte; la diversidad de otras partes del país, especialmente

el Caribe permanece desconocida.

Palabras clave: Ascidiacea; distribución; sistemática;

taxonomía; nuevos reportes.

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