Citation: | Matthew B Toomey, Kevin J McGraw. 2016: The effects of sun exposure on carotenoid accumulation and oxidative stress in the retina of the House Finch (Haemorhous mexicanus). Avian Research, 7(1): 5. DOI: 10.1186/s40657-016-0041-6 |
Diet-derived carotenoid pigments are concentrated in the retinas of birds and serve a variety of functions, including photoprotection. In domesticated bird species (e.g., chickens and quail), retinal carotenoid pigmentation has been shown to respond to large manipulations in light exposure and provide protection against photodamage. However, it is not known if or how wild birds respond to ecologically relevant variation in sun exposure.
We manipulated the duration of natural sunlight exposure and dietary carotenoid levels in wild-caught captive House Finches (Haemorhous mexicanus), then measured carotenoid accumulation and oxidative stress in the retina.
We found no significant effects of sun exposure on retinal levels of carotenoids or lipid peroxidation, in replicate experiments, in winter (Jan–Mar) and spring/summer (May–June). Dietary carotenoid supplementation in the spring/summer experiment led to significantly higher retinal carotenoid levels, but did not affect lipid peroxidation. Carotenoid levels differed significantly between the winter and spring/summer experiments, with higher retinal and lower plasma carotenoid levels in birds from the later experiment.
Our results suggest that variation in the duration of exposure to direct sunlight have limited influence on intraspecific variation in retinal carotenoid accumulation, but that accumulation may track other seasonal–environmental cues and physiological processes.
The Russet Sparrow is a rather common and widespread species of the Oriental Region. Three subspecies are generally recognized, including Passer rutilans rutilans (Temminck and Laugier de Chartrouse, 1836), which breeds in China east of Tibet, Japan and adjacent parts of East Asia, Passer rutilans cinnamomeus (Gould, 1836), which inhabits the Himalayas and adjacent mountain ranges, and Passer rutilans intensior Rothschild, 1922, which lives in Southeast Asia (Moreau and Greenway, 1962; Clement et al., 1993; Dickinson, 2003; Summers-Smith, 2009).
Temminck's rutilans and Gould's cinnamomeus were long considered similar, but separate species until Hartert (1904:161–162) lumped them into a single species. Hartert (1904) incorrectly dated Temminck's and Gould's papers to 1829 and 1835, respectively, and accordingly called the species rutilans, which name he believed to have six years precedence over cinnamomeus. Recent advances in bibliographic research indicate that cinnamomeus has precedence.
Temminck published the name rutilans in the binomen Fringilla rutilans in the text accompanying plate 588 of his and Laugier's Planches coloriées. This plate appeared in the 99th livraison. Hartert (1904:161) said that the plate appeared in 1829 without explanation. Crotch (1869:500), Sherborn (1898:488), Stresemann (1922:54–55) and Zimmer (1926:627) believed that livraison 99 appeared in 1835 (closer date unknown), but Dickinson (2001) documented that this livraison was published only in 1836. A closer date being unknown, the work is deemed as having been published on 31 December 1836 (Dickinson, 2001: 47; ICZN 1999, Art. 21.3).
Gould published the name cinnamomeus in the binomen Pyrgita cinnamomea in a report on the meeting of the Zoological Society of London held on 8 December 1835. This report appeared in the 36th issue of the Society's Proceedings and was included in the volume for 1835. It has long been established that this issue appeared on 8 April 1836 (Sclater, 1893; Duncan, 1937; Dickinson, 2005; Peterson, 2011).
All other synonyms were published much later and do not compete with Temminck's rutilans and Gould's cinnamomeus for priority (Hartert, 1904: 161–162; Moreau and Greenway, 1962: 13–14). The earliest name for the Southeast Asian subspecies is Passer rutilans intensior Rothschild (1922:11).
These data allow to conclude that Gould's cinnamomeus was published on 8 April 1836, while Temminck's rutilans appeared on an unknown date within 1836, i.e., unless shown otherwise, on 31 December 1836 in the sense of the International Code of Zoological Nomenclature (ICZN, 1999, Art. 21.3 and 21.7). Hence, cinnamomeus has priority over rutilans.
The Russet Sparrow thus should bear the name Passer cinnamomeus (Gould, 1836). Its three generally recognized subspecies should be called Passer cinnamomeus rutilans (Temminck, 1836), P. cinnamomeus intensior Rothschild, 1922, and P. cinnamomeus cinnamomeus (Gould, 1836).
I thank two anonymous referees for helpful comments on the manuscript. This paper was supported in part by grants from the Ministry of Culture of the Czech Republic (MK DE06P04OMG008 and MK 00002327201).
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