Morphological variation in the cosmopolitan fish parasite Neobenedenia girellae (Capsalidae: Monogenea)

Brazenor, Alexander K., Saunders, Richard J., Miller, Terrance L., and Hutson, Kate S. (2018) Morphological variation in the cosmopolitan fish parasite Neobenedenia girellae (Capsalidae: Monogenea). International Journal for Parasitology, 48 (2). pp. 125-134.

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Intra-species morphological variation presents a considerable problem for species identification and can result in taxonomic confusion. This is particularly pertinent for species of Neobenedenia which are harmful agents in captive fish populations and have historically been identified almost entirely based on morphological characters. This study aimed to understand how the morphology of Neobenedenia girellae varies with host fish species and the environment. Standard morphological features of genetically indistinct parasites from various host fish species were measured under controlled temperatures and salinities. An initial field-based investigation found that parasite morphology significantly differed between genetically indistinct parasites infecting various host fish species. The majority of the morphological variation observed (60%) was attributed to features that assist in parasite attachment to the host (i.e. the posterior and anterior attachment organs and their accessory hooks) which are important characters in monogenean taxonomy. We then experimentally examined the effects of the interaction between host fish species and environmental factors (temperature and salinity) on the morphology of isogenic parasites derived from a single, isolated hermaphroditic N. girellae infecting barramundi, Lates calcarifer. Experimental infection of L. calcarifer and cobia, Rachycentron canadum, under controlled laboratory conditions did not confer host-mediated phenotypic plasticity in N. girellae, suggesting that measured morphological differences could be adaptive and only occur over multiple parasite generations. Subsequent experimental infection of a single host species, L. calcarifer, at various temperatures (22, 30 and 32 °C) and salinities (35 and 40‰) showed that in the cooler environments (22 °C) N. girellae body proportions were significantly smaller compared with warmer temperatures (30 and 32 °C; P < 0.0001), whereas salinity had no effect. This is evidence that temperature can drive phenotypic plasticity in key taxonomic characters of N. girellae under certain environmental conditions.

Item ID: 51901
Item Type: Article (Research - C1)
ISSN: 1879-0135
Keywords: aquaculture; cryptic species; natural selection; phenotypic plasticity; Platyhelminthes; skin fluke; Monogenea; Neobenedenia
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A version of this publication was included as Chapter 3 of the following PhD thesis: Brazenor, Alexander Karlis (2017) The biology of the cosmopolitan fish parasite Neobenedenia girellae. PhD thesis, James Cook University, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Date Deposited: 02 Feb 2018 00:20
FoR Codes: 30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3005 Fisheries sciences > 300503 Fish pests and diseases @ 50%
31 BIOLOGICAL SCIENCES > 3109 Zoology > 310911 Animal structure and function @ 30%
31 BIOLOGICAL SCIENCES > 3109 Zoology > 310903 Animal developmental and reproductive biology @ 20%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8301 Fisheries - Aquaculture > 830102 Aquaculture Fin Fish (excl. Tuna) @ 100%
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