A healthy skeleton is fundamental for the well-being and performance of a fish. It not only provides support and structure but also impacts its overall well-being and performance. Unfortunately, skeletal deformities are a persistent problem in aquaculture, particularly in farmed salmonids, affecting both fish welfare and industry outcomes. While much research has focused on vertebral deformities, another area of concern has received less attention: deformities of thin bones such as ribs and intermuscular bones (IB).
A team of scientists from the University of Tasmania (Australia), Ghent University (Belgium), Massey University (New Zealand), the Cawthron Institute (New Zealand), and The New Zealand King Salmon Company Limited published a scientific review in the journal Reviews in Aquaculture on intramuscular spines in teleosts. They highlighted points of controversy within this field of research and identified significant knowledge gaps regarding the development and function of salmonid IB.
The Challenge of Intramuscular Spines
IB, also known as spines, are tiny needle-shaped bones embedded in the muscular flesh of salmon, carp, and other “basal teleost” fish species (a group encompassing many commercially important fish). In these farmed fish, IB pose several challenges:
- Processing difficulties: Removing the spines is a laborious and time-consuming process during fish processing, increasing production costs.
- Reduced economic value: The presence of spines can decrease the market value of fish fillets.
- Potential health risk for consumers: If accidentally ingested, the spines can cause choking or discomfort.
Development and Function of Intermuscular Bones
Despite their economic and welfare implications, our understanding of IB development and function in teleosts primarily comes from studies focused on morphology (physical structure). While recent research has delved into the molecular mechanisms of IB development in carp (driven by efforts to breed boneless fish), knowledge about salmonid IB remains limited.
The study delves into the world of intermuscular bones (IB), also known as spines or fish bones, found in teleost fish (bony fish). These are the main findings:
- IB are tiny bones embedded in the muscles of fish and play a role in transmitting muscular force. They form from ossified tendons (turned into bones) that connect muscles to the spine.
- Terminology for IB has been inconsistent, with terms like “false ribs,” “ligaments,” and “spicules” used in the past. The study advocates for the use of “intermuscular bones” as the most accurate term.
- There are three main types of IB: epineurals (attached to neural arches), epicentrals (attached to the horizontal septum), and epipleurals (attached to hemal arches or ribs). Some fish may have additional types.
- The presence and complexity of IB have evolved significantly over time. Primitive fish likely only had simple epineurals, while more advanced fish show a trend of increasing and then decreasing the number and complexity of IB.
- The morphology and number of IB may be related to fish behavior and environment. For example, carnivorous fish with rapid bursts of speed might have more IB to enhance muscular force.
Knowledge Gap on Intermuscular Bones
The study outlines the knowledge gap:
- Function of IB: Currently, no research is available on the precise role that IB play in salmonids.
- Development of IB in salmonids: Specific research on how IB develop in salmon is scarce.
- Standardized terminology: The lack of consistent terminology across studies hinders comparison of findings and collaboration across disciplines.
Addressing these knowledge gaps is crucial. Future research on teleost IB can benefit from:
- Standardization of terminology: This will improve communication and collaboration among researchers.
- Investigation of IB function in salmonids: Understanding the purpose of IB in salmon can help determine their impact on fish health and performance.
- Study of IB development in salmonids: Research on how IB form in salmon can inform breeding programs aimed at reducing or eliminating spines.
Conclusion
This scientific review emphasizes the significant knowledge gap surrounding the development and function of spines in salmon. Closing this gap is crucial for ensuring the future of sustainable aquaculture production while prioritizing the health and welfare of farmed salmon.
On the other hand, it is important to highlight that in species like cachama (Colossoma macropomum), a phenotype of fish lacking intramuscular spines has been reported.
Contact
Brianne A. Lyall
Cawthron Institute
98 Halifax Street East, Nelson 7010, New Zealand.
Email: brianne.lyall@utas.edu.au
Reference (open access)
Lyall, B. A., Witten, P. E., Carter, C. G., Perrott, M. R., Symonds, J. E., Walker, S. P., Waddington, Z., & Amoroso, G. The problems with pin bones: Intermuscular bone development and function in salmonids and their implications for aquaculture. Reviews in Aquaculture. https://doi.org/10.1111/raq.12942
