Aspects of the Ecology of Proteocephalid Cestode Parasites of Hoplobatrachus tigerinus (Daudin, 1803) and Duttaphrynus melanostictus (Schneider, 1799) from YSR (Kadapa) District, Andhra Pradesh, India

The Indian bull frog, Hoplobatrachus tigerinus Daudin, 1803 and Asian common toad, Duttaphrynus melanostictus Schneider, 1799 are frequently found to be infected with the proteocephalid cestodes. The seasonal dynamics of the Proteocephalus sp. was studied in both amphibians during February, 2013 to January, 2015 from YSR (Kadapa) District, Andhra Pradesh. Of the total 300 H. tigerinus examined, only 18 frogs (6%) were infected with the cestode, Proteocephalus tigrinus and of the 46 D. melanostictus examined, only 15 frogs (32.6%) were found to be infected with Proteocephalus sp. Intensity of infection ranged from 1 to 11(n=31) in H. tigerinus and 1 to 2 (n= 19) in D. melanostictus. Monthly population dynamics of cestodesof H. tigerinus and D. melanostictus were analysed in terms of prevalence, mean intensity, mean abundance and index of infection. The effect of habitat predilection and the impact of season on the parasitic load were analysed. The impact of host size and sex on the intensity of infection was also studied. Short Research Article Hemalatha et al.; JALSI, 9(1): 1-11, 2016; Article no.JALSI.29053 2


INTRODUCTION
Parasitism is the one of the most common ecological relationships representing a complex web of interactions among hosts. Host represents a resource and a habitat where the parasite can survive. Amphibians serve as definitive, intermediate, or paratenic hosts for many macroparasites such as trematodes, cestodes, nematodes, acanthocephalans and leeches in aquatic and terrestrial food webs. Individual frogs and toads harbours a dozen of macroparasite species in thousands of number [1,2]. The class Cestoda is one of the major and widespread parasitic classes of the phylum Platyhelminthes infecting all classes of vertebrates around the world. The cestodes of the genus Proteocephalus are reported to occur in freshwater fishes, amphibians and reptiles. The work on proteocephalid cestodes was contributed from all over the world by  from various vertebrate hosts. Proteocephalid cestodes were the only cestode parasites obtained from two species of amphibians, Hoplobatrchus tigerinus and Duttaphrynus melanosticus during the present parasitological survey. In the present study, Proteocephalus tigrinus was reported from H. tigerinus where as D. melanostictus showed infection with Proteocephalus sp. whose species name is not identified in the present study. This study was mainly focused on the various aspects of ecology of the proteocephalid cestodes from these two hosts which will provide a comprehensive knowledge about their seasonal occurrence and community structure in these hosts.

Seasonal Dynamics
H. tigerinus showed highest prevalence of infection during rainy and lowest during winter for 2013-14 cycle whereas it was highest during winter and lowest during summer for 2014-15 cycle (Fig. 3a). These inconsistent results show that seasons doesn't show any impact on the rate of parasitization. However, D. melanostictus showed highest prevalence of infection during rainy and lowest during summer which might be due to the low metabolic activities of the host during the aestivation period during summer season (Fig.  3b). The term locality refers to a geographic milieu of the external environment from where the parasite is segregated. It refers to the geographic spot from where the individual population of community is attained. Locality serves as one of the vital ecological factors playing a momentous role in the occurrence of parasitic species [33][34][35][36][37][38][39][40][41][42][43][44][45]14,22,23].

Community Structure
Out of the four major sites taken under study, incidence of P. tigerinus infection was high for the H. tigerinus examined from Industrial estate (Site-1). Of the 195 hosts examined form site-1, only 14 hosts (7.17%) were parasitized (n=24), with mean intensity of 1.71 and the parasitic load was almost nil for D. melanostictus from this site. Site-2: Ramapuram village, Raychoti and Site-3: University campus area, Kadapa showed least parasitic incidence. However, site-4: Bouinpalli village, Kadapa showed highest parasitic incidence in D. melanostictus. Of the 13 hosts examined form site-4, 7(53.8%) were infected (n=10) with mean intensity 1.42 and the parasitic load was nil for H. tigerinus from this site ( Table-2). Only site-1 and site-4 seems to be the preferred habitats for Proteocephalus sp. infestation during the present survey. The above outcomes signify the preference of the habitat in the incidence of the Proteocephalus sp. in both the hosts.Hence, locality from where the host was collected plays an influential role in the occurrence of the parasite.  Group-III 7-9 cm 2

Effect of Host Size on the Cestode Parasitization
Length of the hosts is considered to be one of the key factors in parasite infra population variation [46,47,13].  (Table-3). Medium sized toads (Group-2) showed high parasitization compared to (Group-1 and Group-3) in D. melanostictus (Table-4). Younger amphibians are more susceptible to parasite infection than the older ones. The present study is in accordance with the views of [48,49] who reported that the penetration of parasite larvae is easier in younger ones than older ones.

Effect of Host Sex on the Cestode Parasitization
Prevalence of parasites with respect to host sex is unpredictable as few reports imply that males show more infection than females while some report that females are parasitized than males. Also some studies suggest that there is no influence of host sex on parasitization. The present study is in total agreement with the views of [50][51][52][53][54]

CONCLUSION
The present study showed a perceptible distinction in terms of seasonal occurrence and the parasitization of cestodes which might be due to the host biology and behavior, their feeding habits and habitat and immense diversity in the environmental conditions.