Cytomorphological alterations of the thymus, spleen, head‐kidney, and liver in cardinal fish (Apogonidae, Teleostei) as bioindicators of stress

Abstract

Morphological and cytological alterations at the light microscope (LM) and transmission electron microscope (TEM) levels were observed in the thymus, spleen, head-kidney, and liver of cardinal fishes (Apogonidae, Teleostei) from the Gulf of Aqaba, Red Sea, sampled from a strongly polluted site at the northern end of the gulf, and compared to similar samples from a clean, reference site. At the polluted site, the most prominent change was the formation of numerous deposits of cells rich in phagosomes with lipofucin, melanin granules, and phagocytosed debris, including a high increase in number and dimensions of Hassall's corpuscles and melano-macrophage centers. The number of Hassall's corpuscles was 20 (+/-8.0)/mm(2) and of melano-macrophage centers 18 (+/-4.0)/mm(2) at the polluted site, and 7.0 (+/-4.0)/m(2) vs. 5.0 (+/-2.0)/mm(2) respectively at the reference site. In numerous instances the head kidney's melano-macrophage centers in fishes from the polluted site were encapsulated by reticulocytes, a phenomenon recognized as a marker of neoplasmosis and possible malignancy. In the spleens of fishes from the polluted site, numerous deposits of cell debris, peroxisomes, and enlarged lysosomes were also observed. The livers (hepatopancreas) of fishes from polluted waters demonstrated very strong hyperlipogeny. Many of their hepatocytes were laden with lipid vesicles, fragmented endoplasmic reticulula, and aberrant mitochondria. Although the observed alterations in the glands and liver do not indicate any immediate threat to the life of the fish, they can become crucial with respect to energy turnover and fecundity trajectories. This study strongly suggests the use of cytological alterations in vital organs, such as were observed, as pathological biomarkers to environmental stress.

Biomarker responses and disease susceptibility in juvenile rainbow trout Oncorhynchus mykiss fed a high molecular weight PAH mixture

“…The head kidney is considered to be the primary immune organ in teleosts [45]. Oxidative stress and to some degree AHR activation, measured indirectly by EROD induction and CYP1A staining in this organ, may have contributed to decreased animal fitness observed as an increase in disease susceptibility in the present study.…”

Functional dissimilarity of melanomacrophage centres in the liver and spleen from females of the teleost fish Prochilodus argenteus

“…The variations in number, morphology, distribution of pigment-containing granules, elementary composition and NAG activity described here provide evidence for the dissimilarity between the metabolic functions of MMCs in the liver and spleen. Previous studies (Wolke 1992;Agius and Roberts 2003;Fournie et al 2001;Fishelson 2006) have suggested that MMC can increase in number and size under stress conditions but the possible relationship between liver and spleen MMCs has been little discussed.…”

“…Agius (1985) has characterized MMCs as an integral part of the fish reticuloendothelial system. These functional characteristics of MMCs have led many authors to suggest the use of the MMC number and size as biomarkers in environmental impact assessments (see Herraez and Zapata 1986;Wolke 1992;Fishelson 2006;Fournie et al 2001). Despite the importance of MMCs as a biological marker, their roles in the different organs are poorly described in the literature (Stentiford et al 2003;Rabitto et al 2005).…”

“…MMCs are found in various phyletic groups such as reptiles (Rund et al 1998), amphibians (Loumbourdis and Vogiatzis 2002) and fishes (Wolke 1992;Fournie et al 2001;Fishelson 2006), and in organs such as the kidney, spleen, thymus and liver (Bruslè and Anadon 1996;Blazer 2002;Agius and Roberts 2003;Fishelson 2006). Diverse functions have been attributed to teleost MMCs, including the capture and storage of cations and the phagocytosis of cellular debris (Wolke 1992;Leknes 2001;Agius and Roberts 2003).…”

“…As different biological responses have been associated with each intracellular granule type, the findings of previous studies focusing on MMC granules might lead to a better understanding of MMC functionality (Wolke 1992;Blazer 2002;Agius and Roberts 2003;Rabitto et al 2005;Fishelson 2006). Valuable insights might also be obtained from studies that highlight the presence of intracellular granules reflecting various metabolic cellular activities such as protein synthesis, calcium storage, iron turnover and detoxification processes (George 1982;Taylor and Simkiss 1989;Corrêa Jr et al 2003, 2009.…”