Aspects of the morphology of the juvenile life stages of Paradiplozoon ichthyoxanthon Avenant-Oldewage, 2013 (Monogenea: Diplozoidae)

Abstract

There are eight life stages in the life-cycle of Diplozoon paradoxum and limited knowledge of the life-cycle for other diplozoid genera exists. The aim of this study was to record the number of life-stages of Paradiplozoon ichthyoxanthon obtained from, Labeobarbus aeneus and Labeobarbus kimberlyensis, in the Vaal Dam from 2005 to 2007. Six larval life stages and one adult stage of P. ichtyoxanthon were identified from specimens collected in vitro and in situ. In vitro, eggs hatched after 21 days at 18°C. Eggs collected during winter were significantly larger than those laid during spring or summer. Paradiplozoon ichthyoxanthon oncomiracidia have peripheral eyes with pink pigmentation, a tubular anterior bladder-like structure, bicuspid basal pharynx valve and a branched digestive caecum and residual shell material or vitellaria in the caecum. Immature reproductive tissue connected to the ventral sucker and dorsal papillae were noted for the first time in diporpa. Large nervous ganglia and innervation of muscle were observed around the ventral sucker.

Hatchability and survival of oncomiracidia of Paradiplozoon ichthyoxanthon (Monogenea: Diplozoidae) exposed to aqueous aluminium

“…However, this appeared to change in eggs containing almost fully developed embryos exposed to 120 μg Al/l where the highest percentage of perished, unhatched larvae were present. This is further supported by the observation that embryos in 120 μg Al/l exposure had reached the final stages of development where eye-spots and cilia were clearly visible [ 26 ]. This could be linked to alterations in the permeability of the egg capsule over the developmental period of the oncomiracidia instead of the resistance of embryos decreasing, where it would then be expected that even at low concentrations the unhatched oncomiracidia would have perished before or shortly after hatching.…”

“…The time taken for hatching of eggs of P. ichthyoxanthon to commence was delayed in 120 μg Al/l exposure, while exposure to 30 μg Al/l and 60 μg Al/l appeared to accelerate hatching time of eggs. According to Avenant-Oldewage & Milne [ 26 ] eggs of P. ichthyoxanthon incubated at 18 °C took 21 days for hatching to commence. MacDonald & Jones [ 24 ] found that hatching of eggs of Diplozoon paradoxum occurred 5–6 days after laying at temperatures ranging from 8–27 °C, but indicated that hatching was related to photoperiod and not temperature.…”

“…Larval development was monitored throughout the duration of the exposure. Development of oncomiracidia of P. ichthyoxanthon was monitored following Avenant-Oldewage & Milne [ 26 ]. Eggs collected from tanks were identified at the oncocyte developmental stage, indicating an approximate age of about 3 days post laying [ 26 ].…”

“…Development of oncomiracidia of P. ichthyoxanthon was monitored following Avenant-Oldewage & Milne [ 26 ]. Eggs collected from tanks were identified at the oncocyte developmental stage, indicating an approximate age of about 3 days post laying [ 26 ]. In their study development of P. ichthyoxanthon began with the oncocyte (day 3), followed by the appearance of the oncoblast (day 5) as a darkened area in the centre of the egg.…”

A brief history of freshwater fish parasitology in southern Africa

“…;Marx and Avenant-Oldewage 1998; Marx 2000a, 2000b;Retief et al 2006;Crafford and Avenant-Oldewage 2009, 2010Watson et al 2012).The UJ group also conducted different studies on aspects of the biology of the interesting Siamese twin monogenean worms of the genus Paradiplozoon(Milne and Avenant- Oldewage 2006;Avenant-Oldewage et al 2012;Milne and Avenant-Oldewage 2012;Avenant-Oldewage and Milne 2014), as well as the description of Paradiplozoon vaalense(Dos Santos et al 2013).…”