Synchronization of occurrence of the ovarian philometrid, Philometra carolinensis, with the spawning season of its fish host, the spotted seatrout, Cynoscion nebulosus

Abstract

The philometrid Philometra carolinensis inhabits the ovaries of the spotted seatrout, Cynoscion nebulosus. A 2-year study in estuaries of South Carolina showed that each year adult female worms were present only during the spawning season of the host and that only sexually mature fish were infected. Overall prevalence was 13.1%. Young-of-the-year fish were uninfected and mature 1-year-old fish were less frequently infected than older fish. Abundance of the philometrid was significantly different in age-1 and -2 spotted seatrout. Prevalence, mean abundance, and intensity peaked during the first 2 months of the host's 4-month spawning season, which then declined abruptly. Occurrence of the philometrid in the fish host was unaffected by water temperature, salinity, and dissolved oxygen. Histological studies revealed that the worms were hematophagous. Worms induced disruption of the ovarian lamellar walls resulting in the interruption of development and the loss of host eggs into the ovarian lumen prior to their maturation. The data show that development of this parasite is linked to the host's reproductive status and suggest that paratenesis plays an important role in the maintenance of the parasite's life cycle.

Philometra chilensis (Nematoda, Philometridae) affects the fecundity of the red cusk-eel, Genypterus chilensis (Guichenot) (Pisces, Ophidiidae) in Chile

“…Few works regarding philometrids include information about quantitative aspects *Corresponding author: rositachavez@gmail.com Philometra chilensis affects the fecundity of red cusk-eel in Chile 237 of the infection. The highest previously reported intensity of infection was 49 worms in one fish, when the mean intensity was 5.5 (Perez et al 2009). …”

“…Genypterus chilensis is a partial spawner, and gonad maturity begins in winter, with a spawning period from August to November and a secondary spawning at the beginning of autumn (April) (Chong and Gonzalez 2009). The absence of specimens of P. chilensis in fish collected during September, which coincides with the main spawning period, can be explained by the type of reproduction (partial spawning), as was suggested by Perez et al (2009). Because of repetitive spawning, worms can be expelled from the gonads into the water column together with the host's eggs.…”

“…The negative impact of gonadinfecting philometrid nematodes on the reproductive success of their hosts has been suggested by Moravec and SalgadoMaldonado (2007), Moravec et al ( , 2008 and Perez et al (2009), among others. Oliva et al (1992) found no evidence of histological damage in the gonads of Paralabrax humeralis infected by Philometra sp., although a moderate leukocytic infiltration was detected.…”

“…They indicated that fish that had grown larger than their size at first maturity are likely to be infected, but immature fish and hermaphrodites are not susceptible to infection. Perez et al (2009) suggested synchrony between parasite maturity and reproductive status of the host fish. According to Chong and Gonzalez (2009), the size at first maturity (size when 50% of specimens are mature) for G. chilensis is 72.4 cm total body length, but the smallest mature fish was 55 cm in length.…”

Gonad-infecting philometrid Philometra philippinensis sp. nov. (Nematoda, Philometridae) from the bigeye barracuda Sphyraena forsteri Cuvier (Sphyraenidae) off Mariveles, Bataan Province, Philippine archipelago

“…Despite this, they seem to have a moderate to severe effect on fish reproduction (Sakaguchi et al 1987;Kåll et al 2004;Clarke et al 2006;Moravec 2006;Deepthi et al 2007;Moravec and Salgado-Maldonado 2007;Quiazon et al 2008b;Perez et al 2009;Radhakrishnan et al 2010;Séguin et al 2011). The ability to accurately identify these parasites is important for developing a full understanding of their biological and infection dynamics, and can also aid development of easy diagnosis, treatment, and control measures.…”