Long-term population trend of the epibiont barnacle Xenobalanus globicipitis in the western Mediterranean: is there a role for viral outbreaks in its cetacean hosts?
-
1
University of Valencia, Cavanilles Institute of Biodiversity and Evolutionary Biology, Spain
Xenobalanus globicipitis is an obligate symbiotic barnacle that has been reported on at least 34 cetacean species worldwide, particularly on dolphins from tropical and temperate waters. As with other filtering cirripeds, the life cycle of X. globicipitis include naupliar and cyprid stages, the latter being specialized to detect the cetacean host and to attach on the trailing edge of fins, which provides suitable water flow conditions for both settlement and nutrient filtration of the adult stage (Carrillo et al. 2015).
In the western Mediterranean, X. globicipitis has been found in several cetacean species, including the most common one, the striped dolphin, Stenella coeruleoalba (Aznar et al. 2005). This dolphin species suffered two mortality outbreaks in 1990 and 2007 caused by the Cetacean Morbillivirus (Raga et al. 2008). Based on stranding records, the first outbreak was considered to be particularly severe, although no precise death toll was estimated. An interesting question is the extent to which a sudden, presumably significant removal of hosts could have affected the long-term population dynamics of X. globicipitis.
We addressed this issue based on prevalence data of X. globicipitis from 404 cetaceans of 8 species that were stranded along the coast of eastern Spain in the last 35 years. We firstly built a descriptive flow-chart model to assess the relative role of striped dolphins in the transmission of X. globicipitis (see Aznar et al. 2001). To do this, we obtained data on lineal density (ind./km) of cetacean species in the study area based on 9 seasonal aerial surveys conducted from summer 2000 to winter 2002. We also assessed the suitability of each host species by comparing frequency of occurrence, mean population size per dolphin, body size (based on shell diameter), and percentage of gravid individuals using 1323 specimens of X. globicipitis collected from 54 individuals of 5 cetacean species. Temporal trends for prevalence of X. globicipitis were explored with generalized additive models for location, scale and shape (GAMLSS) (Rigby and Stasinopoulos 2005) in two host groups, i.e., ‘striped dolphins’ and ‘other cetaceans’.
Excluding the years of epizootics (1990 and 2007), we found a significant difference of prevalence of X. globicipitis among cetacean species. However, a post hoc comparison indicated that only bottlenose dolphins, Tursiops truncatus, had a significantly lower prevalence (14.6%) than other cetaceans (range of prevalence: 39.9-62.5%). The number of barnacles per host, shell size and percentage of gravid individuals did not significantly differ among host species. Also, out of the total number of cetaceans detected per km surveyed, over 88% (range: 81-95%, n= 9 surveys) were striped dolphins. The flow chart based on these data indicated that over 85% of the X. globicipitis population ‘flows’ through striped dolphins. Therefore, rapid changes in the population of this host could influence the population dynamics of X. globicipitis.
The temporal trend of the prevalence of X. globicipitis from 1981 to 2015 was similar in both striped dolphins and the other cetacean species pooled, and it was unaffected by including or excluding 1990 and 2007 (the ‘epizootic’ years). There was a significant increase of prevalence in the period 1990-1995, followed by a decrease that lasted until 2005. Then, prevalence experienced a more modest rise (2006-2009) and fell again (2010-2015). This cyclic pattern is compatible with corresponding changes in the striped dolphin population. Evidence suggests that mortality outbreaks were linked to high density of striped dolphins in the western Mediterranean (Raga et al. 2008), but population rapidly recovered from the epizootics (Gómez de Segura et al. 2006). Accordingly, X. globicipitis could experience temporally coupled increases and decreases of prevalence according to cetacean availability.
Acknowledgements
This study was supported by projects CGL/2012/39545 (Ministry of Economy and Competitiveness, Spain), and PROMETEO II/2015/018 (Generalitat Valenciana, Spain).
References
Aznar FJ, Balbuena J, Fernández M, Raga, JA. (2001). Establishing the relative importance of sympatric definitive hosts in the transmission of the sealworm, Pseudoterranova decipiens: a host community approach. NAMMCO Scientific Publications, vol. 3, pp. 161–171.
Aznar FJ, Perdiguero D, Pérez-Del-Olmo A, Repullés A, Agustí C, Raga J.A. (2005). Changes in epizoite infections during cetacean die-offs: the mass mortality of Mediterranean striped dolphins, Stenella coeruleoalba, revisited. Diseases of Aquatic Organisms, 67: 239-247.
Carrillo JM, Overstreet RM, Raga JA, Aznar FJ. (2015). Living on the edge: settlement patterns by the Symbiotic Barnacle Xenobalanus globicipitis on small cetaceans. PLoS One 17;10(6): e0127367.
Gómez de Segura A, Crespo EA, Pedraza SN, Hammond PS, Raga JA (2006). Abundance of small cetaceans in the waters of the central Spanish Mediterranean. Marine Biology, 150: 149-160.
Raga JA, Banyard A, Domingo M, Corteyn M, Van Bressem MF, Fernández M, Aznar FJ, Barrett T. (2008). Dolphin Morbillivirus epizootic resurgence, Mediterranean Sea. Emerging Infectious Diseases 14: 471–473.
Rigby RA, and Stasinopoulos DM. (2005). Generalized additive models for location, scale and shape. Journal of the Royal Statistical Society: Series C (Applied Statistics) 54: 507–554.
Keywords:
Epibionts,
Xenobalanus globicipitis,
Long-term study,
Morbillivirus,
mortality outbreak,
Barnacles,
Population trends
Conference:
IMMR | International Meeting on Marine Research 2016, Peniche, Portugal, 14 Jul - 15 Jul, 2016.
Presentation Type:
Poster presentation
Topic:
Biodiversity, Conservation and Coastal Management
Citation:
Aznar
FJ,
Fernández Martínez
M,
Raga Esteve
J and
Balbuena Díaz-Pinés
J
(2016). Long-term population trend of the epibiont barnacle Xenobalanus globicipitis in the western Mediterranean: is there a role for viral outbreaks in its cetacean hosts?.
Front. Mar. Sci.
Conference Abstract:
IMMR | International Meeting on Marine Research 2016.
doi: 10.3389/conf.FMARS.2016.04.00086
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
11 May 2016;
Published Online:
13 Jul 2016.
*
Correspondence:
Dr. Francisco J Aznar, University of Valencia, Cavanilles Institute of Biodiversity and Evolutionary Biology, Paterna, Valencia, 46980, Spain, francisco.aznar@uv.es