Obrana doktorskog rada : Martina Krbavčić Jambrošić, mag. biol. mol.

Fiziološka obilježja tkiva petrovog uha Haliotis tuberculata (Linnaeus, 1758) iz sjevernog Jadrana / Physiological characteristics of green ormer Haliotis tuberculata (Linnaeus, 1758) tissues from the Northern Adriatic

17.10.2024. u 11:00 sati : Velika vijećnica Sveučilišta u Zagrebu Agronomskog fakulteta

Mentori doktorskog rada:

• Prof. dr. sc. Tea Tomljanović, Sveučilište u Zagrebu Agronomski fakultet, Hrvatska
• Dr. sc. Natalija Topić Popović, Institut Ruđer Bošković (IRB), Zavod za kemiju materijala, Laboratorij za biotehnologiju u akvakulturi, Hrvatska

Povjerenstvo za obranu doktorskog rada:

• Izv. prof. dr. sc. Daniel Matulić, Sveučilište u Zagrebu Agronomski fakultet, Hrvatska
• Prof. dr. sc. Ana Gavrilović, Sveučilište u Zagrebu Agronomski fakultet, Hrvatska
• Dr. sc. Ivančica Strunjak-Perović, Zavod za kemiju materijala, Laboratorij za biotehnologiju u akvakulturi, Hrvatska

Prošireni sažetak doktorskog rada:
Petrovo uho (Haliotis tuberculata) je morski puž koji primarno naseljava sjeveroistočnu atlantsku obalu, no nalazi ga se i u Mediteranu, a posebice u sjevernom Jadranu gdje se lovi u komercijalne svrhe. Radi očuvanja petrovog uha na lokalitetu sjeverozapadne Istre te mogućeg razvoja kontroliranog uzgoja, važno je poznavati homeostazu njegovog tkiva te promjene u fiziološkim obilježjima tkiva kao biološkog odgovora na promjene temperature mora. Istraživanje utjecaja sezonskih promjena temperature mora na homeostazu petrovog uha u sjevernom Jadranu ukazuje na značajne promjene u biokemijskim pokazateljima, histološko-morfološkoj građi tkiva, peroksidaciji lipida i antioksidativnom kapacitetu. Petrovo uho pokazuje samoregulirajuće procese za održavanje stabilnosti u različitim sezonskim uvjetima. Najviša masa mekog tkiva i ljušture zabilježena je u proljeće, dok je masa probavne žlijezde i mišića bila najviša zimi, zbog veće dostupnosti hrane u jesensko-zimskom periodu. Sezonske promjene također su utjecale na reproduktivni ciklus, s aktivnim stadijima u proljeće i ljeto te fazama gametogene zrelosti i djelomičnog mrijesta u jesen. Osnovni kemijski sastav tkiva varirao je po sezonama, bez značajnih razlika između spolova. Koncentracija biokemijskih parametara poput glukoze (GLU), kolesterola (CHOL), triglicerida (TRIG) te elektrolita (Mg, Ca) mijenjala se kroz godišnja doba. Antioksidativna aktivnost tkiva također je varirala, s najvišim vrijednostima za SOD ljeti, a za LDH i TAS u proljeće. Lipidna peroksidacija (TBARS) bila je najviša ljeti, posebno kod ženki. Sastav masnih kiselina pokazao je sezonske i spolne razlike, s višim udjelom određenih kiselina C15:0 (PDA), C17:0 (HA), C18:0 (SA), C18:2c (LA), C20:4n6 (AA), C20:5n3 (EPA) i C22:5n3 (DPA) kod mužjaka nego kod ženki tijekom toplijeg dijela godine, dok su preostale bile više kod ženki. Veća akumulacija lipida tijekom ljeta može sugerirati da petrovo uho nelipidne prehrambene komponente pretvara u lipide, posebno u zasićene masne kiseline. Ovo je istraživanje pokazalo da petrovo uho vjerojatno ne sintetizira dokozaheksaenoičnu kiselinu (DHA). Analize elemenata u tragovima i makroelemenata pokazale su veće koncentracije Ba, Co, Ni, Mn, Pb, Sb i Se zimi, dok je As bio najviši ljeti. Petrovo uho je organizam od interesa za proučavanje zagađenja okoliša onečišćujućim elementima zbog svog visokog potencijala bioakumulacije elemenata iz okoliša.

Ključne riječi: petrovo uho, tkiva, biokemijski pokazatelji, temperaturni stres, masnokiselinska svojstva, kemijski sastav tkiva i ljuštura, sezonalnost.

Abstract of the doctoral thesis:
Green ormer (Haliotis tuberculata) is a marine gastropod that primarily inhabits the eastern Atlantic coast, but also inhabits the Mediterranean, and especially the northern Adriatic. It is collected for commercial purposes, but it is not farmed in Croatia. Knowledge of the physiological status of green ormer through the analysis of biochemical parameters, lipids and tissues, as well as the histological status in the seasons, is important for the conservation of ormers in the area of northwestern Istria and its potential cultivation.

The samples of the green ormer were collected in the northern Adriatic Sea, off the coast of western Istria, Croatia, following institutional, national, and international laws and guidelines. They were collected in the coastal area of western Istria, in fishing zone A4, at a depth of up to 7 meters. Sampling took place seasonally over the course of a year, with a total of 135 specimens collected. Professional divers collected the samples from known abundant sites near the coast, in the intertidal rocky zone. The green ormer were randomly collected at night when they are most active. Onshore, the specimens were sorted, labeled, weighed, and checked for damage. They were transported on ice to the laboratory, where they were immediately stored in a cold chamber at -86°C for chemical and biochemical analyses, or in a buffered solution of 4% formalin for histological analyses. After being transported to the laboratory, ormers were measured and carefully dissected. The determination of the biometric indicators of the ormers was carried out by measuring the length and mass of the soft tissues and the shell. Due to the small size of the specimens, their individual tissues were not separated for analysis, so the results pertain to the entire soft tissue.

The hydrographic parameters of the sea were measured once a month through all the seasons. These parameters included sea temperature, salinity and dissolved oxygen, which are crucial for understanding changes in the green ormers environment.

The research in this study encompasses the basic chemical and fatty acid composition of the total tissue of the green ormer including tissue concentrations of magnesium (Mg), calcium (Ca), glucose (GLU), triglycerides (TRIG), and cholesterol (CHOL), as well as the activities of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx), total antioxidant status (TAS), and lipid peroxidation (MDA/TBARS). The fatty acids were analyzed and classified according to their saturation level as saturated (SFA), monounsaturated (MUFA), polyunsaturated (PUFA), omega-3, and omega-6 fatty acids. The histological structures of the green ormer were also studied to better understand their reproductive cycle, and concentrations of trace elements in the tissues and shells of the green ormer were determined throughout the seasons of the year.

The research results indicate the impact of seasonal sea temperature changes on the homeostasis of the green ormer and shows significant variations in biochemical indicators, histological-morphological tissue structure, lipid peroxidation, and antioxidant capacity indicating that ormers exhibits self-regulatory processes to maintain stability under different seasonal conditions.

The moisture content in the green ormer tissues was highest during the summer months, correlating with lower values for other parameters. Conversely, the highest levels of raw fats were observed in autumn and winter, while raw proteins and ash peaked in spring, indicating distinct metabolic shifts throughout the year. The decline in fat and protein content during summer, particularly in the reproductive season, suggests a potential allocation of resources towards reproduction.

The highest soft tissue and shell mass was recorded in spring, while the mass of digestive glands and muscles peaked in winter due to increased food availability from autumn to winter. Seasonal changes also affected the reproductive cycle, with active stages in spring and summer and gametogenic maturity and partial spawning in autumn. The basic chemical composition of tissues varied seasonally, with no significant differences between sexes.

Biochemical analyses revealed seasonal variations in metabolites, lipids, electrolytes, and antioxidant activities. Electrolyte concentrations peaked in autumn, while other parameters reached their highest values in the summer. Antioxidant activities showed seasonal fluctuations, with superoxide dismutase (SOD) exhibiting higher levels in summer and lactate dehydrogenase (LDH) and total antioxidant status (TAS) peaking in spring. Lipid peroxidation (TBARS) levels were highest during autumn in males and summer in females, possibly linked to reproductive stress.

Fatty acid composition of the tissues showed seasonal and gender differences, with some fatty acids showing higher concentrations in males during warmer months and other fatty acids showing higher concentrations in females. This adaptation is likely related to membrane fluidity adjustments in response to temperature changes.

Furthermore, concentrations of trace elements and macroelements varied seasonally, with higher levels of Ba, Co, Ni, Mn, Pb, Sb, and Se in winter, while As peaked in summer. Due to its high bioaccumulation potential, the European green ormer is valuable for studying environmental contamination.

The study provides valuable insights into the seasonal dynamics and physiological adaptations of the green ormer in the northern Adriatic Sea, essential for their management and potential aquaculture applications. The results show significant seasonal variation in physiological and biochemical parameters and emphasize the importance of further research for understanding the ecology of the species and improving its conservation efforts.

Keywords: green ormer, tissues, biochemical indicators, temperature stress, fatty acid properties, chemical composition of tissues and shells, seasonality.