Babysitter hosts: an efficient transmission mechanism of invasive fish parasites
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1
Tel Aviv University, Israel
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2
University of Haifa, Israel
The Levant Basin is in many ways the world’s most invaded marine ecosystem owing to the existence of the man-made Suez Canal. To date, more than 450 alien multicellular species of Indo-Pacific origin have been recorded in the Levant. This number, however, is likely an underestimate, particularly as far as smaller sized taxa are concerned, and is expected to grow considerably following the recent expansion of the Suez Canal, which took place on August 2015. Bony fishes are amongst the major taxa introduced to the Levant, comprising ~25% of the records. Many of these have established large populations and now comprise more than 50% of the fish biomass in the shallow continental shelf off the Israeli coastline. While the invasion of fishes has hitherto received a great deal of attention, their accompanying parasites have drawn relatively little interest. In our research we examined the presence of gill parasites (Monogenea) on native and alien fishes along the Israeli coastline. One such alien fish species, the narrow barred Spanish mackerel Scomberomorus commerson who has been known in the Mediterranean Sea for 80 years and has since built up large populations along the Levantine coastline, was found to carry remarkably heavy infections of monogeneans. This fast swimming epipelagic species inhabits coastal waters and feeds primarily on small schooling fish such as sardines and anchovies (Clupeiformes). The gills of S. commerson supported numerous co-invasive, relatively large monogeneans (Monogenea: Gastrocotylinea), reaching prevalence levels of 100% with a mean intensity of 80 worms per host. Four different gastrocotylinean species were identified on S. commerson. Using an integrated molecular and morphological approach, we identified these four species high frequencies also on the gills of clupeiform species, but only at post larval stages. We suggest that these parasitic post larvae do not complete their growth cycle on the gills of clupeids and are found there only at this premature stage. Considering the fact that the Clupeiformes are the major prey species of S. commerson, it is suggested that they may function as ‘temporary’ or ‘babysitter’ hosts of gastrocotylinean species until they reach their definite predator fish host. To further evaluate this hypothesis, the reproduction potential of two of these gastrocotylineans was experimentally estimated, both with living worms, and by inspection of egg numbers in the oviduct of mounted specimens. Live worms held in vitro produced ~15 eggs in a 36 hour period, while in mounted worms only a single egg was normally present in the oviduct. This indicates a low reproductive potential (K-selection strategy) of these parasites. At the same time, the intense infections of adult worms found on the gills of their definite host S. commerson underpin the hypothesis of a unique life cycle of these monogeneans. In this ‘alternative’ life cycle, a substantial portion of the larvae manages to survive on the gills of a “babysitter” host until an individual of S. commerson becomes available. We suggest that such a strategy facilitates the observed successful co-invasion of these parasites with these two very different fish hosts.
Keywords:
Bio-invasion,
Co-invasion,
Parasitology,
Life-cycle,
Molecular diagnosis,
Integrative taxonomy
Conference:
XVI European Congress of Ichthyology, Lausanne, Switzerland, 2 Sep - 6 Sep, 2019.
Presentation Type:
Oral
Topic:
ECOLOGY AND LIFE CYCLES
Citation:
Rothman
SB,
Diamant
A and
Goren
M
(2019). Babysitter hosts: an efficient transmission mechanism of invasive fish parasites.
Front. Mar. Sci.
Conference Abstract:
XVI European Congress of Ichthyology.
doi: 10.3389/conf.fmars.2019.07.00006
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Received:
30 May 2019;
Published Online:
14 Aug 2019.
*
Correspondence:
Dr. Shevy B Rothman, Tel Aviv University, Tel Aviv, Israel, rshevy@gmail.com