INTRODUCTION

Among Caribbean gastropods, heterobranchs

are an uncommon sight due to their low local

abundances. Except for some local population

pulses of aplysiids (sea hares), heterobranchs are

largely overlooked as a group (Diaz and Puyana

1994). Umbraculum (Mollusca: Gastropoda: Het-

erobranchia: Umbraculida: Umbraculidae) has a

cosmopolitan distribution in warm tropical and

temperate waters (Wägele et al. 2006a).

Umbraculum umbraculum has been given dif-

ferent names at various geographic regions

(Sankar et al. 2011). The species was recently

reported at the Bay of Biscay, eastern Atlantic

Ocean (Arias and Crocetta 2016). The local sea-

water temperature generally ranges from 12-13 °C

in winter (January-February) to 21-22 °C in sum-

mer (July-August). However, a generalized sea

surface warming (an upward trend of the sea sur-

face temperature series) and intensification in the

upwelling intensity during the summer months has

been registered off the Santander and Bilbao coast

during the last two decades (Bode et al. 2013).

This increase in temperature influences significant

changes in the local faunal composition (Bode et

al. 2013) and may be considered an indication of a

tropicalization of the area, a pattern that has also

been shown in coral replacement of kelps in south-

ern Japan (Vergés et al. 2014).

Morphologically, U. umbraculum is character-

ized by its long foot and a flat shell covering its

body (Mikkelsen 2002). It has a deep orange

color and a mantle covered with pustules. As

MARINE AND FISHERY SCIENCES 33 (1): 129-133 (2020). https://doi.org/10.47193/mafis.3312020061809

NOTE

SEA GRASSES, A NEW UNREPORTED HABITAT FOR THE HETEROBRANCH

MOLLUSK Umbraculum umbraculum IN THE CARIBBEAN REGION

ERIKA GARCÍA-BONILLA1, PAULA GONZÁLEZ1, LAURA PIRATEQUE1, JÜRGEN GUERRERO-KOMMRITZ2,

MÓNICA PUYANA3and ALBERTO ACOSTA1

1Grupo de Investigación Unidad de Ecología y Sistemática (UNESIS), Departamento de Biología,

Facultad de Ciencias, Pontificia Universidad Javeriana, Carrera 7 Nº 43-82, Bogotá, Colombia

e-mail: ejgb30@gmail.com

2Fundación Fundabas, Bogotá, Colombia

3Grupo de Investigación Bioprospección y Biotecnología,

Departamento de Ciencias Biológicas y Ambientales, Facultad de Ciencias Naturales e Ingeniería,

Universidad Jorge Tadeo Lozano, Carrera 4 Nº 22-61, Bogotá, Colombia

ABSTRACT. Herein, a new habitat for the heterobranch mollusk Umbraculum is described. One specimen was

found on a Thalassia testudinum bed at Taganga Bay at 3 m depth, a buffer area of the Tayrona National Park,

Colombian Caribbean. To the best of our knowledge, these mollusks have not been previously reported in this kind of

habitat. Seagrasses may provide protection and possibly serve as areas for its reproduction.

Key words: Heterobranch, habitat, Thalassia testudinum, Colombian Caribbean.

129

other members of the Order Umbraculida,

Umbraculum spp. are specialist predators on a

wide array of sponges (Willam 1984; Avila et al.

2018). Heterobranchs are well known for seques-

tering, transferring and even modifying metabo-

lites from their diet for defensive purposes

(Faulkner and Ghiselin 1983; Cimino et al. 2001).

These compounds may be released via mucus or

concentrated in the mantle dermal formations or

other glandular structures (Wägele et al. 2006a).

The only metabolites from U. umbraculum

known to date are two diacylglycerols and a fatty

acid ester probably produced by the sponge Geo-

dia cydonium in the Mediterranean where the

mollusk was collected (Cimino et al. 1988, 1989).

Until now, little is known about the ecology of

heterobranchs such as U. umbraculum, even

though its presence is recognized in the

Caribbean region. Information about habitat pref-

erences, food and reproduction patterns is scarce.

This note describes a recent finding of this mol-

lusk on a previously unreported habitat, which

may provide shelter during various stages of its

life cycle.

Habitat characteristics

A solitary specimen of the heterobranch mol-

lusk Umbraculum umbraculum was found on

March 1, 2018 at a Thalassia testudinum bed at

Taganga bay, a buffer area of the Tayrona Nation-

al Park, Colombian Caribbean (11° 16′ 16.1″ N-

74° 11′ 54.1″ W; Figure 1 A) at 3 m depth. The

area is affected by local coastal upwelling from

December to March. In these months, seawater

temperature may drop to 20-25 °C (Diaz-Pulido

and Garzon-Ferreira 2002; Bayraktarov et al.

2012). The seagrass bed where we found the

specimen was located on a muddy sand substrate

at the leeward side of the bay (Figure 1 B). We

carried out some preliminary evaluations to

assess the conservation state of this seagrass bed

in particular. In an area of 100 m2, we measured

parameters such as shoot density, growth rate and

overall biomass. We determined that this bed has

a rather low density (88 shoots m-2, each bearing

two to five short leaf blades, 15 cm long, growing

from a basal meristem). The calculated growth

rate was of 0.8 cm day-1, yielding an overall bio-

mass of 5.04 g m-2 and reaching a productivity of

0.15 g m2 day-1. These biological features, togeth-

er with rather intense tourist activity in the area,

and ecosystem risk analysis (Bland et al. 2016)

allow us to consider that this seagrass bed is in a

poor conservation state, and possibly in Critical

Risk of collapse according to IUCN categories.

Specific habitat preferences for U. umbracu-

lum have not been well documented to date. The

species has been only reported at shallow sandy

bottoms in Greece (Wägele et al. 2006b; Sankar

et al. 2011). In Colombia, a specimen (Catalog

number INV MOL-1595; MAKURIWA-Marine

Natural History Museum of INVEMAR;

http://siam.invemar.org.co/buscador) was collect-

ed on soft bottoms (70 m depth) at Cabo de la

Vela (Marcus and Marcus 1967) in the upwelling

area of the Guajira (12° 12′ 15.7″ N-72° 10′ 59.4″

W) and also seen at Tayrona National Park (Ardi-

la et al. 2007).

To the best of our knowledge, there are no pre-

vious reports of U. umbraculum thriving in Tha-

lassia testudinum beds. As with other hetero-

branchs, U. umbraculum might gain protection

from predation among the seagrass blades and

may also find suitable food sources, once, in our

field evaluations, we found several specimens of

Agelas spp. and other sponges. Additionally, the

animal observed was in reproductive mode since

upon collection it released copious amounts of

sperm (Figure 1 C and 1 D), which suggest that

U. umbraculum uses the upwelling season (Janu-

ary to March) to migrate to shallow water and

reproduce as others mollusks do at Taganga Bay

such as Octopus hummelincki (Adam, 1936) and

Aplysia dactylomela (Rang, 1828) (Jürgen Guer-

rero-Kommritz, Pers. Observ.).

Habitat and water quality in Taganga bay have

diminished over the last four decades. The bay is

130 MARINE AND FISHERY SCIENCES 33 (1): 129-133 (2020)

subject to high sedimentation rates coming direct-

ly from local sources (the Manzanares and Gaira

rivers as well as seasonal stream flows into Playa

Taganga) and indirectly through the Magdalena

river plume, particularly after heavy rains. The

fact of finding this specimen suggests two possi-

ble scenarios: the first one is that seagrasses may

be a suitable habitat for this species, where poten-

tial predators such as fishes and crabs are signifi-

cantly diminished due to overfishing. Alternative-

ly, the presence of this mollusk species might rep-

resent a threat for other animals such as sponges

upon which they prey upon. Overall, we believe

that the seagrass bed at Taganga bay may provide

food and shelter for many invertebrate species

and possibly vertebrates as well, from adjacent

rocky shores, reef formations and soft bottoms

(Pawlik 1998; Pawlik et al. 2018).

While brief, this report is of great interest to

gain some further insights on the distribution and

ecology of this uncommon mollusk. It also raises

new questions concerning its potential vertical

migration, as well as food and habitat prefer-

ences. Further research should provide more

insights on the life habits of U. umbraculum in

the Caribbean region.

131

GARCÍA-BONILLA ET AL.: NEW HABITAT FOR U. UMBRACULUM

Figure 1. A) Map of the seagrass bed where the specimen of Umbraculum umbraculum was found (red dot) at Taganga Bay,

Colombian Caribbean. B) Detail of the seagrass habitat, with profuse growth of sponges that could potentially be a food

source for this opisthobranch. Seagrasses could also be an important breeding habitat for this mollusk. C-D) Live spec-

imen of U. umbraculum collected; note the sperm released by the individual (arrow).

ACKNOWLEDGEMENTS

The authors acknowledge Erika Montoya at

INVEMAR for providing biological information

of U. umbraculum registered in Colombia.

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