Revista Chilena de Historia Natural 84 (3): 379-390, 2011
RESEARCH ARTICLE
Near-shore distribution of phyllosomas of the two only lobster species (Decapoda:
Achelata) present in Robinson Crusoe Island and endemic to the Juan Fernández archipelago
Two lobster species coexist in the southeast Pacific Juan Fernández
archipelago, Jasus frontalis (Milne-Edwards, 1837) and Acantharctus delfini (Bouvier, 1909).
Like most lobster species they undergo a prolonged larval period, which is particularly long for J. frontalis
(> 16 months). Though typical of Palinurids, this long larval duration is usually not thought to be conducive to
local recruitment. While it is known that settlement is confined to the three islands of the archipelago (Robinson Crusoe,
Alejandro Selkirk and Santa Clara) and Desventuradas Islands (aprox. 800 km to the north), it remains poorly understood
how local larval supply allows such distribution pattern. The goal of this study is twofold. Firstly, we aimed to characterize
the distribution and abundance of the larvae of these two species around Robinson Crusoe Island using plankton tows and
systematic hydrographic records between October 2008 to March of 2011, thus providing the first systematic and prolonged
coupled biophysical observations in the nearshore of the archipelago. We hypothesize that spatial and temporal larval
distribution patterns are associated to their retention around the archipelago, thus contributing to our knowledge of the
physical and biological processes maintaining their extreme isolation. Secondly, using molecular genetics, we confirm a
simple taxonomic criteria to distinguish the larvae of the two species, thus aiding future studies of larval dynamics.
Throughout phyllosomas of A. delfini were more abundant than that of J. frontalis. Both species
were more abundant on the northern shores of Robinson Crusoe Island and generally associated with warmer and saltier
waters and mostly present in the samples collected during spring and summer months. Phyllosomas of both species were
more abundant during night-time tows in the upper layer of the water column surveyed suggesting a diurnal vertical
migration behavior which, for coastal dwelling meroplanktonic species, can be related to a nearshore larval retention
mechanism. These preliminary results represent a pioneering effort to understand the mechanisms driving the endemism
and extreme isolation of the two study species.
Key words:
endemism,
lobsters, oceanic island, phyllosoma
