Circulation is required for egg production in the insect,Rhodnius prolixus

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Abstract
Egg production in the blood-feeding insect, Rhodnius prolixus, was inhibited by transecting the dorsal vessel (DV) in abdominal segment III immediately after feeding, or ligaturing the DV in the same location, 3 to 6 days post-emergence. Juvenile hormone (JH), applied topically to operated animals after feeding, removed this inhibition indicating that a functioning DV is required to maintain the appropriate levels of JH in the abdomen. Reduced JH levels in the abdomen may result from failure to transport JH from the corpus allatum (CA) in the head to the abdomen, or from a reduction in activity of the CA. The present study examined the flow of material from the head to the abdomen in DV-severed animals, and found that: 1) methyl-blue injected into the head of DV-severed animals accumulated in nephrocytes in the abdomen 1 to 2 h after injection; 2) radiolabelled 14C inulin injected into the head of DV-severed animals diffused to the abdomen within 90 min. of injection; 3) egg toying, which depends on the action of myotropin on the ovaries, was not inhibited if the DV were severed prior to the expected onset of egg laying, suggesting that a hormone (i.e., myotropin) could diffuse from the head to the abdomen in operated animals. Thus, material can diffuse from the head to the abdomen in DV-severed animals indicating that circulation may be needed to maintain activity of the CA.