Читать книгу Honey Bee Medicine for the Veterinary Practitioner - Группа авторов - Страница 65

The digestive system of the honey bee begins with the mouth, including the proboscis. The esophagus is long, passing through the head and thorax before it empties into the crop, or “honey stomach,” in the cranial portion of the abdomen. The abdomen of the bee visibly expands (see Figure 8.7) when the insect ingests fluids (water, nectar, or honey) and the crop fills (Snodgrass et al. 2015).

The crop is used for carrying resources to and from the hive. The proventricular valve between the crop and the next portion of the digestive tract, the ventriculus, prevents contents of the crop from passing further along the tract where it would otherwise be digested. The ventriculus or midgut is where digestion occurs. Distal to the midgut is the intestine, which has a short, narrow section and a wider, expandable portion, the rectum (Snodgrass et al. 2015). Normally, bees will not defecate in the hive, so an expandable rectum allows retention of fecal waste until the bee is able to fly from the hive; in winter, it may be several months before the bee leaves the hive. This nice‐weather release of feces occurs in what beekeepers call “cleansing flights” (Figure 3.13).

In insects, nitrogenous waste excretion is managed by the Malpighian tubules – a series of long, meandering tubes that collect waste products from the hemolymph to be excreted with digestive waste via the rectum. Malpighian tubules are broadly equivalent in function to the vertebrate kidney.

Figure 3.13 Digestive system.

Source: Illustration by Patrick D. Wilson.

The function of the vertebrate liver is provided in insects by the “fat bodies.” Fat bodies are small organs that lie on the dorsal and ventral aspects of the abdomen and play a critical role in the synthesis of hemolymph proteins and the synthesis and storage of lipids. The fat bodies are critical for the survival and successful overwintering of honey bees. It was recently reported that the Varroa mite, which can so devastate hives, feeds not on hemolymph but on the fat bodies of infested bees (Ramsey et al. 2019).