The Heterophil-to-Lymphocyte (H/L) Ratio Indicates Varying Physiological Characteristics in Nestlings Compared to Adults in a Long-Lived Seabird
The ratio of the innate heterophils to the acquired lymphocytes (the H/L-ratio) has been advocated as a good indicator of physiological stress. Little is known, however, about their development in wild birds. The present study investigates how leucocyte profiles develop in nestlings of a long-lived...
Saved in:
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-01-01
|
| Series: | Birds |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2673-6004/6/1/4 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | The ratio of the innate heterophils to the acquired lymphocytes (the H/L-ratio) has been advocated as a good indicator of physiological stress. Little is known, however, about their development in wild birds. The present study investigates how leucocyte profiles develop in nestlings of a long-lived seabird, the Black-legged Kittiwake (<i>Rissa tridactyla</i>). We counted blood leucocytes in nestlings of about 10 and 25 days of age (n = 23), and in breeding adults around the time of hatching (n = 40) and calculated the H/L-ratio for all three groups. We further investigated if any variation in the leucocyte counts could be explained by body condition or the stress-related hormone corticosterone. 10-day-old nestlings in better body condition showed greater investment in heterophils, which increased their H/L-ratio. The initial focus on innate immunity shifted towards acquired immunity by 25 days, aligning their H/L-ratio with that of adults. In adult Kittiwakes, however, better body condition correlated with lower H/L-ratio, the reverse of the pattern in young nestlings, and this variation was not linked to stress hormone (corticosterone) levels. Overall, our findings suggest that the H/L-ratio reflects the ontogeny of physiological traits and individual condition. As an indicator, values must be interpreted depending on age, in which its sensitivity may also vary. As such, the H/L-ratio may not always be a reliable indicator of physiological stress, in particular related to the release of glucocorticoid hormones. |
|---|---|
| ISSN: | 2673-6004 |