Internal anatomy: The circulatory system

In the honey bee, as in all insects, the haemolymph fills the entire internal cavity protected by the cuticle. This cavity is called the haemocoel. There is no network of veins and arteries: the organs are bathed in the haemolymph, which supplies the organism with the necessary components. It is referred to as an extracellular fluid. A long tubular vessel, the heart, pumps the haemolymph and ensures the circulation of the fluid throughout the organism.

Internal anatomy of the honey bee – The circulatory system

In honey bees, the circulatory system is of the open type. Hemolymph, an extracellular body fluid, fills the entire internal cavity protected by the cuticle, known as the hemocoel. There is no network of veins and arteries; instead, organs are directly bathed in hemolymph, which transports nutrients, hormones, metabolic waste and biochemical signals.

Hemolymph contains various cell types called hemocytes. Their number increases during metamorphosis, and they play an important role in immune defense. The composition of hemolymph changes with the bee’s developmental stage and physiological condition.

Functionally, the hemocoel is divided into three main sinuses: the dorsal (pericardial) sinus, the lateral (perivisceral) sinus, and the ventral (perineural) sinus. These compartments are separated by two longitudinal muscular diaphragms, dorsal and ventral. Rhythmic movements of these diaphragms help circulate hemolymph throughout the body.

The heart is the central circulatory organ. It is a long, contractile dorsal tube that collects hemolymph from the pericardial sinus and pumps it toward the head. Lateral openings called ostia, equipped with valve-like structures, allow hemolymph to enter the heart and prevent backflow. The heart is anchored to the abdominal wall by ligaments known as “heart wings.”

In the thorax, the heart continues as the aorta, a non-contractile tubular vessel. Its initial tortuous section functions as a heat exchanger, enabling regulation of hemolymph temperature. This adaptation allows bees to fly at ambient temperatures ranging approximately from 10 °C to 46 °C. The aorta releases hemolymph directly into the head hemocoel, from where it flows back toward the thorax and abdomen.

Additional pulsatile organs in the legs and wings assist local circulation. They are essential for supplying peripheral nerves, sensory receptors and for maintaining thermoregulation.

In summary, the honey bee circulatory system is a highly efficient open system, integrating transport, immune function and temperature control.
 

Source: Abeille & Cie; 2017, No. 173; Technical factsheet; http://www.cari.be

See also:

• Internal Anatomy: General Overview
• Internal Anatomy: The Digestive System
• A Highly Social Immunity
• Vitellogenin and the Keys to the Colony
• Biology and Physiology of the Bee