BACKGROUND: Marine invertebrates are abundant and diverse on the continental shelf in Antarctica, but little is known about their parasitic counterparts. Endoparasites are especially understudied because they often possess highly modified body plans that pose problems for their identification. Asterophila, a genus of endoparasitic gastropod in the family Eulimidae, forms cysts in the arms and central discs of asteroid sea stars. There are currently four known species in this genus, one of which has been described from the Antarctic Peninsula (A. perknasteri). This study employs molecular and morphological data to investigate the diversity of Asterophila in Antarctica and explore cophylogenetic patterns between host and parasite.
RESULTS: A maximum-likelihood phylogeny of Asterophila and subsequent species-delimitation analysis uncovered nine well-supported putative species, eight of which are new to science. Most Asterophila species were found on a single host species, but four species were found on multiple hosts from one or two closely related genera, showing phylogenetic conservatism of host use. Both distance-based and event-based cophylogenetic analyses uncovered a strong signal of coevolution in this system, but most associations were explained by non-cospeciation events.
DISCUSSION: The prevalence of duplication and host-switching events in Asterophila and its asteroid hosts suggests that synchronous evolution may be rare even in obligate endoparasitic systems. The apparent restricted distribution of Asterophila from around the Scotia Arc may be an artefact of concentrated sampling in the area and a low obvious prevalence of infection. Given the richness of parasites on a global scale, their role in promoting host diversification, and the threat of their loss through coextinction, future work should continue to investigate parasite diversity and coevolution in vulnerable ecosystems.
Funding for this research comes from the Antarctic Circumnavigation
Expedition, The University of Western Australia, and the National Science
Foundation (USA) ANT-1043749. KKSL was supported by a University
Postgraduate Award for International Students (UPAIS) and an RTP
International Fees Offset scholarship (RTPFI) administered by The University
of Western Australia, as well as a postgraduate doctoral scholarship from the
Natural Sciences and Engineering Research Council of Canada (NSERC). These
funding bodies did not have a role in the design of the study, the collection,
analysis, and interpretation of data, or in writing the manuscript.
Availability of data and materials
The datasets used and/or analysed during the current study are available
from the corresponding author on reasonable request and GenBank
accessions appear in the manuscript.
- Antarctic Regions
- Biological Evolution
- Host Specificity
- Host-Parasite Interactions
- Larva/anatomy & histology
- Species Specificity