## 3 Results and Discussion
### Different Shapes of Microl plastics Found in Mussel Digestive Glands  
The majority of MP particles found in the mussel tissue at all sampled locations were in the form of fragments, followed by spheres, lines, and film, with statistical differences found at all sampling locations (Table 1, Figure 7). The MPs in the line shape were found in a low number in the mussels sampled at St. Catherine, Seca, and Strunjan locations (0-1 MPs/digestive gland). In the mussels sampled at the ACI marina Rovinj, spheres and fragments (16.55 \(\pm\) 14.69 MPs/digestive gland and 14.05 \(\pm\) 11.19 MPs/digestive gland, respectively) were predominantly found, and were observed in much larger quantities compared to all other investigated sites (\(p\) < 0.01). Films were the most rarely found shape of MPs and were especially low in abundance in the mussel tissues from St. Catherine Island, Seca, and Strunjan (0-1 MPs/digestive gland) but were found in a higher number in the mussels from the ACI marina Rovinj (2.00 \(\pm\) 2.15 MPs/digestive gland). Like in our study, fragments were frequently identified as the most prevalent shape of MPs in mussels in many studies. In the study by [PERSON] and [PERSON] [83], the morphology of MPs was ordered as follows: fragments (67.6%) > fibers (28.4%) > films (4.05%). Also, in the study by [PERSON] et al., fragments were noted to be the most abundant shape of MPs found in the green-lipped mussel _P. perma_ from New Zealand [98]. In another study, the majority of ingested MPs in the mussels _M. galloprovincialis_ from the Ionian Sea were fragments (77.8%), followed by fibers (22.2%) [52]. On the contrary, [PERSON] et al. have noted filaments to be the most frequent MPs present in paracultured and natural mussels (_M. galloprovincialis_) from different Italian stocks [102]. In our study, one fiber was determined as a contaminant present in the mussel digestive gland cryosections, and this shape accounted for the less frequent type of material observed in cryosections. Fibers have been the most often found MPs in many studies until now [36; 37; 54; 60; 84], and we suppose this could be because of the cryosections analysis. In Qingdao, China, microfibers were also the most found form among all types of MPs discovered in locally cultured bivalve species (scallop _Chlamys fareri_, mussel _Mytilus galloprovincialis_, oyster _Crassostrea gigas_, and clam _Ruditapes philippinarum_) [88]. Furthermore, [PERSON] et al. have also found fibers, followed by fragments, to be the most common MPs found in the mussel _M. edulis_[32]. In research conducted in laboratory conditions with blue mussels (_M. edulis_), it was demonstrated that mussels take up MP fibers in a quantifiable and predictable manner, and most of the fiber ended up in the mussel digestive gland, with less in the gills [34]. The results from a study conducted by [PERSON] et al. have confirmed that fibers were the predominant type of MPs observed in the mussel _P. viridis_ from Kasimedu, Chennai, India, followed by spheres, flakes, sheets, and fragments [67]. Furthermore, in a study conducted by [PERSON] et al., the MPs found in mussels bought at the Turkish market in five different cities were identified as fibers (62.7%) and fragments (37.3%) [94]. Fragments or fibers were also mainly recorded as the dominant shape of MPs found in the edible green-lipped mussel _P. viridis_ by using an automated mapping technique of Raman microspectroscopy [97]. According to [PERSON] et al., the higher prevalence of fibers in mussel bodies compared to other morphological types could be attributed to the slower egestion rate of fibers that may lead to a prolonged accumulation of fibers in the mussel's digestive gland [51]. Additionally, fluctuations in local oceanographic conditions can hasten the gradual breakdown of plastic objects into smaller fragments and spheres [103].