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Animals
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Morphological and Physiological Research on Fish: Second Edition
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Morphological and Physiological Research on Fish: Second Edition

A special issue of Animals (ISSN 2076-2615). This special issue belongs to the section "Aquatic Animals".

Deadline for manuscript submissions: 15 March 2026 | Viewed by 4192

Special Issue Editors

Dr. Elena De Felice

E-Mail Website
Guest Editor
School of Biosciences and Veterinary Medicine, University of Camerino, 62032 Camerino, MC, Italy
Interests: molecular biology; immunohistochemistry; food intake; regulation of food intake; gut–brain axis; aging; animal models
Special Issues, Collections and Topics in MDPI journals
Prof. Paola Scocco

E-Mail Website
Guest Editor
School of Biosciences and Veterinary Medicine, University of Camerino (MC), 62032 Camerino, Italy
Interests: histochemistry; morphometry; animal welfare; food intake; digestive apparatus; reproductive apparatus; mammary gland; ruminants; environmental sustainability
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue is dedicated to the application of morphological and physiological studies carried out on fish.

Fish represent the largest and most diverse group of vertebrates, and these animals are used in both research and industry. On the one hand, aquaculture is one of the world's most efficient and sustainable methods to produce high-quality protein. On the other hand, in the last decades, fish have emerged as an interesting model system in biomedical research due to their close similarities with mammals in terms of various basic mechanisms. Morphological studies provide a context for comprehending the spatial organization and relationship between physiological and biochemical data and the molecular machinery that is explained through molecular techniques directed at the genome, transcriptome, and proteome. For this reason, new morphological and physiological studies of fish could broaden our knowledge pertaining to these animals, with remarkable and interesting applicability both in basic and applied research.

Considering the success of our previous Special Issue, we are pleased to launch "Morphological and Physiological Research on Fish: Second Edition". This Special Issue will attempt to provide information regarding the relevance of morphological studies and their relationships with functions in fish.

In this Special Issue, original manuscripts, review articles, and short communications, alongside research with the potential for application are particularly welcome.

You are cordially invited to contribute to this theme or related research topics in order to improve the existing anatomical and physiological knowledge of fish.

Dr. Elena De Felice
Prof. Dr. Paola Scocco
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Animals is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • fish
  • anatomy
  • basic research
  • physiology
  • aquaculture

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Related Special Issue

Published Papers (5 papers)

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Research

22 pages, 5213 KB  
Article
DHEA and Cortisol in Rainbow Trout (Oncorhynchus mykiss): Effect of Sex, Sexual Maturity, and Acute Stress Exposure
by Andrea Meloni, Martina Bortoletti, Elena Negrato, Elisa Fonsatti, Giuseppe Radaelli and Daniela Bertotto
Animals 2025, 15(18), 2710; https://doi.org/10.3390/ani15182710 - 16 Sep 2025
Viewed by 418
Abstract
Glucocorticoids like cortisol are widely used to assess stress in fish, but their interpretation can be limited. Incorporating dehydroepiandrosterone (DHEA), a hormone with anti-glucocorticoid and neuroprotective effects, may provide a broader understanding of hypothalamic–pituitary–inter-renal (HPI) axis activity. As DHEA data in fish remain [...] Read more.
Glucocorticoids like cortisol are widely used to assess stress in fish, but their interpretation can be limited. Incorporating dehydroepiandrosterone (DHEA), a hormone with anti-glucocorticoid and neuroprotective effects, may provide a broader understanding of hypothalamic–pituitary–inter-renal (HPI) axis activity. As DHEA data in fish remain scarce, this study examined its role in rainbow trout (Oncorhynchus mykiss) subjected to acute stress (30 min confinement), considering sex and sexual maturity. Cortisol and DHEA were quantified by optimized radioimmunoassay (RIA) in serum, muscle, fin, and scales, and gonadal histology was performed to confirm reproductive status. Both hormones were successfully measured in all matrices, with serum DHEA levels notably higher than those reported to date in fish. As expected, serum cortisol increased markedly after stress and correlated with levels in muscle and fin but not in scales, which appears to reflect chronic rather than acute exposure. In contrast, serum DHEA showed no stress-induced changes and only minor sex- and maturity-related differences, although alternative matrices displayed variable patterns, particularly in muscle and fin. The cortisol/DHEA ratio in serum mirrored cortisol dynamics, suggesting limited utility for acute stress assessment, while tissue-specific DHEA variation may integrate longer-term influences. Further research is needed to clarify the role of DHEA under chronic stress and its potential origins in inter-renal tissue, gonads, or the brain. Full article
(This article belongs to the Special Issue Morphological and Physiological Research on Fish: Second Edition)
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18 pages, 8098 KB  
Article
Impact of Amirthalingamia macracantha Larvae on Nile Tilapia (Oreochromis niloticus): A Morpho-Histopathological Perspective
by Ebtsam Sayed Hassan Abdallah, Mahmoud Mostafa Mahmoud, Hanan Hassan Abdel-Hafeez, Marco Albano, Gioele Capillo, Asmaa Mohamed Metwally, Sultan Mohammed Areshi, Dalal Alardan and Yosra M. I. El Sherry
Animals 2025, 15(16), 2334; https://doi.org/10.3390/ani15162334 - 9 Aug 2025
Viewed by 470
Abstract
Amirthalingamia macracantha (Joyeux and Baer, 1935) larvae, a member of the Gryporhynchidae family (Cestoda: Cyclophyllidea), are commonly found in a variety of African fish species, including Nile tilapia (Oreochromis niloticus, Linnaeus, 1758). Nonetheless, little is known regarding their existence in [...] Read more.
Amirthalingamia macracantha (Joyeux and Baer, 1935) larvae, a member of the Gryporhynchidae family (Cestoda: Cyclophyllidea), are commonly found in a variety of African fish species, including Nile tilapia (Oreochromis niloticus, Linnaeus, 1758). Nonetheless, little is known regarding their existence in native Egyptian fish species. Two hundred O. niloticus were examined in the current investigation, using standard parasitological techniques to detect the presence of these larvae in different fish organs. According to this study’s findings, A. macracantha larvae were found in 35% of the microscopically examined samples as red nodules, attaching to the serosa of both the anterior and posterior sections of the intestine and stomach, respectively. The mean abundance of the infection was 3.5 ± 0.05 (CI 95% 3.4–3.5), and its mean intensity was 10 ± 1.7 (CI 95% 8.2–11.7). The existence of two rows of twenty rostellar hooks of varying lengths is the main characteristic of the parasite. The upper row consisted of four large hooks and six smaller ones, while the lower row contained smaller hooks of consistent length. According to histopathological analysis, the larvae with a hook-and-spiny rostellum were affixed to the stomach serosa of O. niloticus. Additionally, there was a notable presence of degranulated mast cells and lymphocytes of varying sizes within the stomach’s lamina propria, submucosa, and blood vessels, as well as a loss of gastric epithelium, fibrosis, and enlargement of submucosal lymph vessels. This study offers a succinct description of this larval stage, representing the first reported occurrence of its presence in Egyptian O. niloticus. Full article
(This article belongs to the Special Issue Morphological and Physiological Research on Fish: Second Edition)
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16 pages, 3350 KB  
Article
Morphological and Histological Analysis of the Gastrointestinal Systems in Triplophysa strauchii and Triplophysa tenuis: Insights into Digestive Adaptations
by Zhengwei Wang, Lirong Zhang, Jie Wei, Huimin Hao, Syeda Maira Hamid, Shixin Gao, Wenjun Li and Zhulan Nie
Animals 2025, 15(8), 1095; https://doi.org/10.3390/ani15081095 - 10 Apr 2025
Cited by 1 | Viewed by 983
Abstract
Fish are vital for material cycling and energy flow in aquatic ecosystems. The genus Triplophysa, with over 100 known species, is significant in the Central Asian highlands’ freshwater ecosystems. T. strauchii and T. tenuis, as representatives, occupy distinct ecological niches and [...] Read more.
Fish are vital for material cycling and energy flow in aquatic ecosystems. The genus Triplophysa, with over 100 known species, is significant in the Central Asian highlands’ freshwater ecosystems. T. strauchii and T. tenuis, as representatives, occupy distinct ecological niches and face challenges from climate change and human activities. There is a lack of research on Triplophysa fishes’ digestive systems, especially comparative studies, so this research aims to fill this gap. In September 2024, 40 samples of T. strauchii were collected from Sayram Lake and 40 samples of T. tenuis were collected from the Muzat River in Xinjiang. After acclimation, morphological observations (measuring fish and digestive tract parameters) and histological analyses (paraffin sectioning, HE staining, and microscopy) were carried out. The data were sorted in Excel and analyzed with an independent samples t-test in SPSS 27.0. Morphologically, T. strauchii has an obtuse snout, terminal mouth, specific upper lip papillae, and an S-shaped intestine about (1.45 ± 0.11) times its body length, while T. tenuis has an arc-shaped subterminal mouth, fringed papillae, and a spiral-shaped intestine around (0.82 ± 0.09) times its body length. Both possess a digestive tract, glands, and a hepatopancreas attached to the mesentery. Histologically, a large number of club cells were found in the oropharyngeal cavities of both species; their secretions have an adhesive effect on food, aiding food selection. Their digestive systems vary in structure and cell composition: the oropharyngeal cavity has three layers; the esophagus has four layers with more goblet cells in T. strauchii; the stomach has three regions without goblet cells and a thicker muscular layer in T. strauchii; the intestinal wall has four layers with different villi and goblet cell distributions; the hepatopancreas has lobules; and T. strauchii has a typical portal area. In conclusion, this study systematically compared the gastrointestinal systems of T. strauchii and T. tenuis for the first time, revealing significant structural differences related to their niches and feeding patterns as adaptations to specific environments. It fills the research gap, provides a basis for exploring fish ecological adaptation and environmental impacts on digestion, offers new ideas for Triplophysa protection strategies, and guides fish evolutionary biology research and Triplophysa resource protection and utilization. Full article
(This article belongs to the Special Issue Morphological and Physiological Research on Fish: Second Edition)
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21 pages, 5664 KB  
Article
Morphology, Age, and Growth of Triplophysa strauchii in Sayram Lake, Xinjiang, China
by Zhengwei Wang, Huimin Hao, Jie Wei, Hao Wu, Syeda Maira Hamid, Ruixian Lv, Huale Lu and Zhulan Nie
Animals 2025, 15(7), 1039; https://doi.org/10.3390/ani15071039 - 3 Apr 2025
Cited by 3 | Viewed by 779
Abstract
This study focused on T. strauchii in Sayram Lake, Xinjiang. In August 2023, a total of 768 samples were collected to investigate its morphological, age, and growth characteristics. T. strauchii has an elongated body with a slightly raised area behind the head. Its [...] Read more.
This study focused on T. strauchii in Sayram Lake, Xinjiang. In August 2023, a total of 768 samples were collected to investigate its morphological, age, and growth characteristics. T. strauchii has an elongated body with a slightly raised area behind the head. Its head is flat, the body is slender, the back contour is arc-shaped, the trunk is thick and round, and the tail is short. Principal component analysis (PCA) showed that the cumulative contribution rate of the first three principal components was 53.80%, which reflects the morphological characteristics of the species. Moreover, gender characteristics are not prominently manifested in external morphology. Discriminant analysis showed an accuracy rate of 51.80%, indicating that the accuracy of gender discrimination relying solely on external morphology is limited. The species’ age distribution ranges between 1 and 7 years old, with the dominant age around 3 years old, and age structure showing a unimodal distribution. The relationship between body length and body weight is W = 7.432 × 10−6L3.037(R2 = 0.995, n = 768). The exponent 3.037 indicates a growth pattern with priority given to body mass growth because it is greater than 3. The von Bertalanffy growth equation was selected to describe the growth of T. strauchii. The body length growth equation is Lt =139.346 [1 − e−0.267(t+1.639)], and the body mass growth equation is Wt = 27.79 [1 − e−0.267(t+1.639)]3.073. The inflection point age (ti) is 2.563, the growth coefficient (k) is 0.267, and the growth characteristic index(φ) is 3.715. The growth rate decreases with age, and the growth inflection point ages of males and females differ. The research findings provide basic data for population assessment, resource protection, and rational fishing in fishery resource management. This highlights the ecological adaptability of T. strauchii and emphasizes the importance of comprehensively considering multiple factors in fishery management. Full article
(This article belongs to the Special Issue Morphological and Physiological Research on Fish: Second Edition)
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24 pages, 2168 KB  
Article
Variability in Morphological Traits and Nutritional Profiles of Adult Eriocheir sinensis in Different Aquacultural Regions
by Wenrong Feng, Qinghong He, Jianlin Li, Jun Zhou, Guoan Hua, Yuanfeng Xu, Gang Jiang and Yongkai Tang
Animals 2025, 15(2), 243; https://doi.org/10.3390/ani15020243 - 16 Jan 2025
Cited by 4 | Viewed by 939
Abstract
Eriocheir sinensis is a species of significant economic importance in China’s aquaculture industry. In order to investigate the variations in morphologic and nutritional profiles of farmed crabs across diverse farming regions, E. sinensis were collected from six aquafarms located in the primary cultivation [...] Read more.
Eriocheir sinensis is a species of significant economic importance in China’s aquaculture industry. In order to investigate the variations in morphologic and nutritional profiles of farmed crabs across diverse farming regions, E. sinensis were collected from six aquafarms located in the primary cultivation areas in China. The findings revealed significant variations in specific morphological indices, but these are insufficient for clear regional distinction using PCA. Essential amino acid (EAA) levels varied by tissue and gender, with ovaries from the YY (Yongyan in Anhui province) group showing the highest levels, while the hepatopancreas in females from the JX (Jianxian in Jiangxi province) group had the lowest. The analysis of fatty acid contents revealed that muscles were rich in PUFAs, whereas MUFAs were dominant in the hepatopancreas and gonads. The fatty acid levels were significantly higher in ovaries than in testes, notably in the HZ (Huzhou in Zhejiang province), EZ (Ezhou in Hubei province), YY, and JX groups. Furthermore, the PCA based on proximate composition, amino acids, and fatty acids revealed distinct categorizations of E. sinensis from various regions. In conclusion, these findings highlight significant regional variations in the morphology and nutritional composition of farmed E. sinensis, suggesting the need for tailored aquaculture practices to optimize quality and output. Full article
(This article belongs to the Special Issue Morphological and Physiological Research on Fish: Second Edition)
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