Although they may be visually enticing, painted shells should be discouraged from use for both ethical and safety-related reasons.
Ethics of Painted Shells:
Wild hermit crabs are harvested in non-painted shells and so must be enticed into painted alternatives for market.
Most hermit crabs will not switch to a painted shell if they can help it, but crab processing plants have a simple, economical, and effective method of doing so.
First, the hermit crab’s shell is lodged into a vice. That vice is then tightened to break the crab’s shell. With its shell shattered, the hermit crab is helpless. It can now be dropped into a container of painted shells where it has no choice but to take one or risk injury to its fragile abdomen. Hermit crabs that do not take a shell may be pushed into one by hand.
Many question the morality of squeezing a live animal in a vice. There is significant risk of injury and crushed crabs are not uncommon. Additionally, there have been instances of hermit crabs being glued into their shells after being shoved inside while the paint was still wet.
Safety of Painted Shells:
Hermit crabs will modify their shells for comfort, an action that can result in chipping or even ingestion of the paint. Ergo, the safety of all compounds applied to their shells must be taken into consideration.
Most paints have two basic parts, the binder and the pigment. The binder may be made of oil, epoxy, acrylic, or another substance of synthetic or natural origin. Safety data is limited and will vary from substance to substance. However, most of the concern lays in the pigments.
Many pigments are made of heavy metals. Hermit crab health data is limited but heavy metal poisoning has many adverse effects on vertabrate immune, neurological, digestive, and reproductive systems. Common heavy metals used in paints include
• Lead: used to create reds, yellows, and whites
• Mercury: used to create reds
• Cadmium: used to create reds, oranges, yellows, and greens
• Cobalt: used to create yellows, blues, and violets
• Chromium: used to create yellows and greens
• Copper: used to create greens, blues, and purples
Heavy metals used in paints are heavily regulated and, in some cases, banned, as in the case of lead in the United States. However, actual regulations will vary by country and not every country regulates paint as heavily as others. Although seldom a concern for arts and crafts, anything our pets must live with daily should face closer scrutiny.
Figures:
All images are credited to Xenocrab (2020).
Figure 1. A painted Babylonia shell after one year of use. Note that the larger bare spots were picked off manually by the owner
Figure 2. Another painted Babylonia shell. Some of the paint was applied to the inside.
Figure 3. Hand added for scale.
Figure 4. A “natural” Turbo petholatus shell with a topcoat. Note the large globs of dried sealent.
Figure 5. A variety of painted shells.
Further Reading: