Assessment of the effects of plerocercoid larvae of Ligula intestinalis (Cestoda) on Engraulicypris sardella (Cyprinidae) from northern Lake Nyasa/Malawi/Niasa

Abstract

Engraulicypris sardella (Günter, 1868) is a cyprinid fish exploited in the waters of Lake Nyasa that has been found to be infested by Ligula intestinalis (Linnaeus, 1758). Although L. intestinalis has been the subject of a number of studies, there is no information on the effects of this parasite on E. sardella. This study was therefore aimed at assessing the prevalence and intensity of the parasite L. intestinalis, condition of the fish and impact on fecundity of E. sardella. Data recorded for each individual fish included: total length, weight, sex and maturity stage, number of parasites, gonad assessment and egg count. Number, length and total weight of L. intestinalis found per fish host were recorded. The average infestation rate from the two landing sites (Matema and Kafyofyo) was 32.5%. Kafyofyo had the highest infestation rate (50%) and Matema (15%); on average, each infested fish had 1.7 parasites. The majority of infested fish carried one parasite (57%) with 23.1% having two parasites, 13.8% three parasites, 1.5% four parasites and 4.6% five parasites. There was significant difference between the weight of fish with parasites and those without parasites (P < 0.05). Mean length and weight of parasites was 73.6 mm and 0.25 g, respectively. There was also a significant difference between the weight of gonads of infested and non-infested fish (P < 0.05). The average weight of gonads from infested fish was 0.28 g, while that of non-infected fish was 0.32 g. Gonads of all infected fish were atrophied. Number of eggs (fecundity) decreased significantly with parasite infestation. Condition factors of both infected and uninfected fish did not show any significant difference (Mann-Whitney U-test P > 0.01). Therefore, it was concluded that L. intestinalis parasites affect fecundity and consequently inhibit the reproductive capacity of this cyprinid fish population.

Dynamics and effects of Ligula intestinalis (L.) infection in the native fish Barbus callensis Valenciennes, 1842 in Algeria

“…At low prevalence and infection rates, it is unclear whether this parasitic castration has any tangible ecological effects. Moreover, condition factor was not influenced by infection (Msafiri et al 2014), confirming that Ligula at low infection rates is relatively harmless (Ergonul and Altindag 2005). This also suggests that the loss of weight of the gonad is almost exactly compensated by abundance of perivisceral fat in the fish (Trubiroha et al 2010).…”

Life history shifts in an exploited African fish following invasion by a castrating parasite

“…In Lake Nyasa this cestode has been increasingly reported since it was first noted by Mwambungu et al (1996).E. sardella appears to be the only species used as intermediate fish host (Msafiri et al , 2014;Rusuwa et al , 2014;Gabagambi and Skorping, 2018;Gabagambi et al , 2019) Figure S1). L. intestinalis is known to induce castration in several intermediate hosts (Wyatt and Kennedy, 1988;Kennedy et al , 2001;Loot et al , 2002;Cowx et al , 2008;Hoole et al , 2010) and has therefore been suggested to cause population crashes of its host (Burrough et al , 1979;Kennedy et al , 2001).…”

“…In infected fish the parasite is found filling the body cavity (Hooleet al , 2010). Higher infection rates are observed in larger and older E. sardella than in juvenile individuals (Msafiri et al , 2014;Rusuwa et al , 2014), which can partly be explained by diet shifts from phytoplankton to zooplankton as E. sardellareaches maturity.…”

Increased reproductive investment in an exploited African cyprinid fish following invasion by a castrating parasite in Lake Nyasa, Tanzania

“…Higher infection rates are observed in larger and olderE. sardella than in juvenile individuals (Msafiri et al, 2014;Rusuwa et al, 2014), which can be explained by diet shifts from phytoplankton to zooplankton as E. sardella reach maturity.…”

“…Ligula intestinalis (L. 1758) is a common and widespread cestode, that use cyprinid fish as intermediate hosts (Dubinina, 1980). In Lake Nyasa this cestode has been increasingly reported since it was first noted by Mwambungu et al (1996), where it infects the endemic pelagic fish Engraulicypris sardella ( Figure 1) (Gabagambi et al, 2019;Gabagambi and Skorping, 2018;Msafiri et al, 2014;Rusuwa et al, 2014). L. intestinalis is known to induce castration in several intermediate hosts (Cowx et al, 2008;Hoole et al, 2010;Kennedy et al, 2001;Loot et al, 2002;Wyatt and Kennedy, 1988) and has therefore been suggested to cause population crashes of its host (Burrough et al, 1979;Kennedy et al, 2001).…”