Roaches are a common household pest that can be found all over the world. Despite their prevalence, there is still much we don’t know about their biology and anatomy. One common question is: do roaches have hearts? The quick answer is yes, roaches do have hearts.
Roach Anatomy
Cockroaches belong to the insect order Blattodea. Like all insects, they have an exoskeleton, three body segments (head, thorax, and abdomen), three pairs of legs, compound eyes, and antennae. Their bodies are flattened which allows them to hide in tight spaces.
On the inside, cockroaches have many of the same internal organs as other insects:
- Digestive system – to extract nutrients from food
- Respiratory system – to deliver oxygen throughout the body
- Circulatory system – to circulate blood and nutrients
- Excretory system – to eliminate waste
- Nervous system – to control actions and behaviors
- Reproductive system – to produce eggs
The circulatory system is where we find the heart. Let’s take a closer look at how roach circulation works.
The Roach Heart
The roach heart is a long tube located at the top of the abdomen. Unlike vertebrate hearts that regularly expand and contract to pump blood, the roach heart simply pulses or throbs. Despite this difference, it serves essentially the same role in circulating blood (hemolymph in insects) throughout the body.
Specifically, the cockroach heart has three main sections:
- Inflow chamber – collects hemolymph from the insect’s head and thorax.
- Muscular central chamber – pulses to push hemolymph into the abdomen.
- Outflow chambers – distributes hemolymph to the rest of the body.
Valves throughout the heart and ostia (pores) along the sides control the directional flow. The pulsing occurs at a rate between 20 and 40 beats per minute.
Hemolymph moves through an open circulatory system, flowing freely into spaces called hemocoels rather than confined vessels. The hemolymph delivers nutrients and oxygen while collecting carbon dioxide and waste. Like blood, hemolymph also contains immune cells to fight infection.
Roach Heart Function
The main functions of the roach heart are:
- Circulate hemolymph – Keeps fluids moving to transport nutrients, gases, wastes, and immune cells throughout the body.
- Establish rhythm – Sets a regular pulse that drives locomotion and breathing patterns.
- Distribute hormones – Carries hormones secreted by neurosecretory cells to target tissues.
Roaches have an open circulatory system that is lower in pressure than closed circulatory systems with major arteries and veins. But the cockroach heart still generates enough force to reach all tissues via diffusion from hemocoels.
The heart rate can speed up to spread oxygen faster during activity and stress. Some neurohormones have been identified that regulate heart rate, allowing roaches to adapt to changing conditions. For example, the peptide CCAP speeds up heart contractions.
Comparisons with Vertebrate Hearts
Roach hearts share a few key features with vertebrate hearts:
- A central pumping region
- Valves to control unidirectional flow
- An inflow and outflow region
- Hormonal control mechanisms
However, there are also some important differences between insect and vertebrate cardiovascular systems:
| Roach Heart | Vertebrate Heart |
|---|---|
| Long tube heart | Chunky, multi-chambered heart |
| Lower blood pressure | Higher blood pressure |
| Open circulatory system | Closed circulatory system |
| Pulse or throb | Regular contract and expand |
| Fewer valves | More valves |
| Fewer hormones | More hormones |
These differences reflect the smaller, simpler circulatory needs of insects versus vertebrates. But the basic pump action to move fluids within a contained system is functionally the same.
Heart Development and Evolution
Early in embryonic development, cockroach heart cells differentiate from a group of dorsal mesoderm cells. Heart precursor cells become organized into a tube and begin pulsating by the end of embryogenesis.
Researchers have identified some of the genes and signaling pathways involved in insect heart development, such as:
- wingless (wg) – segment polarity gene
- decapentaplegic (dpp) – codes for TGF-beta proteins
- dorsal – in the Toll signaling pathway
The cockroach heart likely evolved from a simple contractile vessel in ancient insects. Adaptations for a true pumping heart likely arose in the Devonian period, over 350 million years ago. Heart structures have diversified along with insects, but core genetic pathways are conserved.
Advanced insect groups like Hymenoptera and Diptera have developed more complex circulation with accessory pulsatile organs to boost hemolymph flow. This may correlate with nutrient demands of flight and higher activity levels.
Roach Heart Regeneration
A remarkable feature of the cockroach heart is its regenerative capacity. If the heart is cut or damaged, heart cells can dedifferentiate, migrate to the wound, and proliferate. These progenitor cells redifferentiate into heart cells and restore normal structure and function.
This regeneration happens quickly, within 7-10 days. Roaches have provided an important model for studying cardiac cell dedifferentiation and redifferentiation pathways.
Understanding the molecular mechanisms behind roach heart regeneration may someday provide insight for human cardiac regeneration therapies. This could offer new hope for heart disease treatment.
Conclusion
Despite their humble reputation, roaches have a surprisingly sophisticated internal anatomy. A specialized heart organ pumps fluid through an open circulatory system to deliver nutrients and oxygen. Roach hearts share several key features with vertebrate hearts but are optimized for simple diffusion-based distribution.
Ongoing study of the roach cardiovascular system provides useful models for cardiac development, function, and regeneration. So next time you see one of these scurrying insects, remember they have a pulsing heart hidden within that helps power their daily survival!