Mutualistic association of rotifer Philodina roseola with the branchiuran fish ectoparasite Argulus bengalensis at its embryonic stage

An insight into the interaction between Argulus siamensis and Labeo rohita offers future therapeutic strategy to combat argulosis

Aquaculture and fisheries are salient flourishing sectors in the world but their sustainability is often afflicted by several pathogenic diseases. Among all the pathogenic diseases of fish, parasitic diseases are found to be a major cause of concern. Argulosis is one of the dominant parasitic problems encountered in Indian aquaculture practices. Argulus siamensis is the most prevalent argulid species harming the Indian major carp species including Labeo rohita. The major carps respond to parasitic infestation by elevating various immune relevant genes. The therapeutic chemicals, synthetic drugs and other plant extracts have made a progress in the fight against argulosis. However, there is no effective vaccine and drugs are available for this disease. Thus, designing efficient, cost-effective and eco-friendly control and treatment strategies for argulosis is presently needed. Keeping the aforementioned facts in mind, the current review elaborated the immunological interaction between A. siamensis and L. rohita, available combat tactics, highlighted the already identified vaccine candidates to design effective control measures and illustrated the use of omics technology in future to combat argulosis.

Antiparasitic potentiality of ethanol and methanol extracts of Azadirachta indica leaf for eggs and copepodid stage of Argulus japonicus: in vitro study

In the present study, eggs and copepodid stages of Argulus japonicus were treated with ethanol and methanol extract of Azadirachta indica (neem) leaf and its antiparasitic efficacy (AE %) was determined. The experiments were performed in triplicate along with the positive (2% DMSO) and negative (without DMSO and extract) control groups. The reduced cumulative hatching percentage of eggs by 13% (in ethanolic) and 17% (in methanolic) extract of neem leaf at 1.5 g L^-1 was obtained during 15-day exposure compared to the control group showing 70-85% eggs hatching. The AE of 100% for ethanolic and 91.66% for methanolic extract against the copepodid stage was found at 1.25 and 1.5 g L^-1 respectively in 6 h. The histological analysis of the eggs showed the undifferentiated decaying mass of cells with extensively damaged eggs when treated with ethanolic extract of neem leaf. Further, severe degeneration in the branchial region, digestive tract and eye cells was observed in the copepodids treated with ethanol extract than the methanol extract. The terpenoids a potential antiparasitic compound of ethanolic extract produced more AE than the methanolic extract. Thus, the ethanolic extract of neem leaf can be potentially utilized as a natural parasiticide to disrupt the egg and other life phases of A. japonicus.

Rotifers weaken the efficiency of the cyanobacterium defence against ciliate grazers

Cyanobacteria can protect themselves through limited dispersion and by increasing the compactness of the mucilage-covered cyanobacterial mat as well as by producing sheaths covering their trichomes. These features have been used in research to measure their degree of inducible defence. The influence of the presence of the rotifers Lecane inermis on the effectiveness of Phormidium sp. (Ph2) cyanobacterium defence was investigated. Experiments were conducted on the ciliates Pseudomicrothorax dubius and Furgasonia blochmanni, specialised in the ingestion of filamentous cyanobacteria. The most compact were cyanobacterial mats that were subjected exclusively to ciliates and the most dispersed were mats in the presence of rotifers alone. The presence of rotifers feeding on cyanobacterial mucilage led to the decreased effectiveness of the defence in two ways, by increasing the dispersion of cyanobacterial trichomes, thus loosening the cyanobacterial mat, and through the ingestion of the exopolysaccharide material covering the trichomes. As a result, in the presence of rotifers and the high density of ciliates, almost all the trichomes were removed. Moreover, in comparison with other treatments, a higher number of ciliates and rotifers remained active until the end of the experiments. This is the first report to show how rotifers can weaken the defence of cyanobacteria.

Life Cycle and Life History Strategies of Parasitic Crustacea

Different parasitic life strategies are described including four new life cycles: complex rebrooding, micro-male, mesoparasite and prey-predator transfer. Four new life cycle behaviours are named: nursery hiding, mid-moult stage, positive precursor (intraspecific antagonism) and negative precursor (ambush strategy). Further strategies discussed are opossum attack, double parasitism (doubling of the normal reproductive set), duplex arrangement (separated male-female pairs), simple rebrooding, and describing how displaced parasites and superinfections may partly elucidate life cycles. Proportional stunting masks life history effects of parasitism; cuckoo copepods are true parasites and not just associates; burrowing barnacles (acrothoracicans) are not parasites. Further findings based on life cycle information: branchiurans and pentastomes are possibly not related; firefly seed shrimp are not parasites; copepod pre-adult life cycle stages are common in the western pacific but rare in Caribbean; harpacticoids on vertebrates are not parasites; cuckoo copepods are true parasites; explained the importance of pennellid intermediate hosts. Crustacean parasite life cycles are largely unknown (1% of species). Most crustacean life cycles represent minor modifications from the ancestral free-living mode. Crustacean parasites have less complex and less modified life cycles than other major parasite groups. This limits their exploitation of, and effectiveness, in parasitism. However, these life cycles will be an advantage in Global Change. Most metazoan parasites will be eliminated while crustaceans (and nematodes) will inherit the new world of parasites.