Question

The larva of Wuchereria exhibits

• A. Exra intestinal migration
• B. Ex-flagellation
• C. Nocturnal periodicity
• D. Anisogamy

Hint:

Remember specific adaptations of parasites for transmission. \textit{Wuchereria bancrofti} microfilariae exhibit nocturnal periodicity to coincide with the biting habits of their mosquito vectors.

Answer 1

The Correct Option is C

Step 1: Identify the organism and its life cycle.
\textit{Wuchereria} is a genus of filarial nematodes that cause lymphatic filariasis (elephantiasis) in humans. The life cycle involves two hosts: humans (definitive host) and mosquitoes (intermediate host). The infective larval stage (microfilariae) circulate in the human blood. Step 2: Analyze the given options in the context of \textit{Wuchereria larvae (microfilariae).} \begin{itemize} \item (1) Exra intestinal migration (Extra-intestinal migration): While filarial larvae do migrate within the host's body (e.g., from blood to lymphatic vessels in humans, or within the mosquito vector), "extra-intestinal migration" is a very general term. More specific behaviors characterize \textit{Wuchereria} larvae. This is not the most defining characteristic presented as an option. \item This option is not the most accurate or specific answer. \item (2) Ex-flagellation: Ex-flagellation is a process specific to the male gametocyte of \textit{Plasmodium} (malaria parasite), where flagella-like structures (microgametes) emerge from the gametocyte to fertilize female gametes. This process is completely unrelated to \textit{Wuchereria} larvae. \item This option is incorrect. \item (3) Nocturnal periodicity: The microfilariae (larvae) of \textit{Wuchereria bancrofti} (the most common species causing lymphatic filariasis) exhibit a characteristic nocturnal periodicity. This means they are predominantly found in the peripheral blood circulation during the night (typically between 10 PM and 4 AM), and their numbers significantly decrease in the peripheral blood during the day, as they retreat to deeper vessels (like pulmonary capillaries). This synchronized appearance in peripheral blood during the hours when their mosquito vectors (e.g., \textit{Culex} mosquitoes) are most active facilitates transmission. \item This option is correct. \item (4) Anisogamy: Anisogamy refers to sexual reproduction involving the fusion of two gametes of unequal size or form (e.g., large ovum and small sperm). This describes the fusion of gametes during sexual reproduction in \textit{Wuchereria} (which occurs in the mosquito gut to form larvae), but it does not describe a characteristic \textit{exhibited by the larva itself} as part of its behavior or morphology. The question asks what the larva exhibits. \item This option is incorrect as it describes a process leading to larval formation, not a characteristic of the larva's behavior. \end{itemize} Step 3: Conclude the correct option.
The most distinct and well-known characteristic exhibited by the larvae (microfilariae) of \textit{Wuchereria} is their nocturnal periodicity. The final answer is $\boxed{\text{Nocturnal periodicity}}$.