Histomorphological Damage in the Small Intestine of Wami Tilapia (Oreochromis urolepis) (Norman, 1922) Exposed to Microplastics Remain Long after Depuration

Abstract

The histopathological effects of microplastics (MPs) in the gastrointestinal tracts of fish following long-term exposure and depuration are relatively understudied. This study investigated histomorphological damage in the small intestine of Oreochromis urolepis larvae following 65 d exposure to 38–45 μm of polyethylene microspheres (PE MPs) and after a recovery period of 60 d. Larval fish were assigned to each treatment group (control, 1, 10 and 100 PE MPs), where ingestion and degenerative changes in the small intestine were examined using a routine hematoxylin and eosin staining technique. The results highlighted significant PE MPs ingestion and retention proportional to exposure dose (χ2 = 49.54; df = 2). Villi height and width and epithelial cell height were significantly affected and differed between treatment groups. Indices of damage to the small intestine organ (χ2 = 47.37; df = 2; p < 0.05) and reaction patterns of villi, epithelial, goblet and cryptic glandular cells, leucocytic infiltration and blood congestion revealed significant occurrence of alteration as PE MPs exposure dose increased. After the recovery period, no PE MPs were observed, and villi height, width and epithelial cells showed recovery with no significant difference between treatment groups. Organ indices declined (χ2 = 12; df = 2; p < 0.05) but remained significantly different between treatment groups, largely due to leucocytic infiltration (χ2 = 9.08; df = 2; p < 0.05). The study demonstrated that microplastics induced small intestinal wall degeneration, but recovery in young fish occurred slowly. The damage likely compromised its digestive function, which may affect growth and reproduction. This requires further research.

Impaired Growth Performance of Wami Tilapia Juveniles (Oreochromis urolepis) (Norman, 1922) Due to Microplastic Induced Degeneration of the Small Intestine

“…The PE MPs with a density of 1.00 g/cc (product ID of UVPMS-BG) and size range 38-45 µm were purchased from Cospheric LLC, Santa Barbara, CA 93160, USA, order # 117,025, and were similar to those used by Mbugani et al [13]. Tween 80 surfactants (product number: P8074) were supplied by Sigma-Aldrich (Sigma-Aldrich, 3050 Spruce Street, Saint Louis, MO 63103, USA).…”

“…Such ubiquity reduces food accessibility and [6] and jeopardizes fish welfare [7]. Various Microplastics 2022, 1 335 studies reveal that the ingestion of MPs by fish [8] causes not only false satiation but also histopathological impairment with subsequent effects on physiological status [9][10][11][12][13].…”

“…The effects of MPs in fish guts are relatively well studied. Physical damage in gastrointestinal tracts have been widely reported on various fish species [13,28,29]. O. niloticus exposed to a various dose of MPs for 15 d revealed proportional degeneration of a number of intestinal cells [28].…”

“…Our previous study investigated the ingestion of fluorescent green polyethylene microsphere (denoted as 'PE MPs') by Wami Tilapia (Oreochromis urolepis) (Norman, 1922) and their histomorphological impact after exposure and depuration phases [13]. We found that small intestine histological tissues were damaged, and the effect persisted even after the depuration period.…”

“…Following our previous research [13], the present study aimed to investigate the association between MPs-induced degeneration of small intestine with growth impairment of Oreochromis urolepis [31]. Fish were chronically exposed (65 days) to concentrations of 1, 10, and 100 PE MPs/mL and whilst the highest concentration exceeds environmental relevance, such high doses are commonly employed within experimental studies to determine the potential effects and mechanisms of MP exposure to aquatic biota [32][33][34].…”