Snježana Kužir

The Development of the Digestive Tract in Larval European Catfish (Silurus glanis L.)

The European catfish, Silurus glanis L., has become an important aqua cultural fish in Croatia, and it is cultivated extensively in ponds in polyculture with carps. The development of the digestive tract in S. glanis was studied with the aim of improving intensive fish production. Research was carried out on S. glanis larval stadium from 1‐ to 19‐day post‐hatching (DPH). The main histological methods used were: haematoxylin and eosin staining, periodic acid Schiff staining (PAS), Alcian blue (AB) and toluidin blue staining (TB). A yolk sac was present during the first 5 days (1–5‐DPH). During the initial 3‐DPH period, there was no trace PAS and AB activity in the digestive tract. Differentiation of the digestive tract began at 3‐ to 5‐DPH. The oesophagus was positive for AB at 5‐DPH, PAS and TB after 7‐DPH. Differentiation of enterocytes began at 5‐DPG and the intestines were complete at 11‐DPH. Development of liver and pancreas was also studied. The analysis of data obtained in this study suggests that after 5‐DPH catfish larvae have morphologically completed digestive tracts.

Metacercariae of Centrocestus formosanus in goldfish (Carassius auratus L.) imported into Croatia

SummaryThe presence of metacercariae of Centrocestus formosanus was detected on the gills of goldfish (Carassius auratus L.) imported from Singapore and obtained from two pet shops. This is the first report of the parasite in Croatia. The histopathological changes observed lead to the conclusion that the infection could be one of the reasons for the death of goldfish.

Osteological Development of the Garfish (Belone belone) Larvae

Garfish, Belone belone (Linnaeus, 1761) is an elongate, slander fish inhabiting the Eastern Atlantic and Mediterranean Sea. These fish from the Belonidae (Actinopterygii) family have important commercial value for Croatian fisheries. Samples for research were collected from experimental hatching in the Novigrad Sea. Preparation techniques included fixation in buffered formalin, trypsin clearing and staining with alcian blue and alizarin red. As little is known of garfish osteology and bone morphology, the main goal of this study was to describe ossification process in garfish fry. At hatching, no skeletal structure is present. Newly‐hatched larvae also had no osteological elements. Ossification started at 7 day post‐hatching (DPH) [total length (TL) 18 mm] with head bones and vertebral neural arch. Head skeleton continued to develop mostly over the period from 7 to 10 DPH. At 21 DPH (TL 49 mm), ossification process seemed to be finished, but it was not possible to distinguish borders of all bones. The primary interest of our research was to understand the growth dynamics as well as transformation of supporting body elements from cartilage to bone. At the end, developmental characteristics and functional aspects of this formation in different fish species are discussed.

Spontaneous multicentric myxoma of the dermal nerve sheaths in farmed European eels Anguilla anguilla

This report describes a peripheral nerve sheath tumour in 8 European eels Anguilla anguilla L. from a fish farm located in Croatia. The newborn tissue appeared as smooth and soft skin nodules without pronounced colour change. Nodules were dome-shaped with a pale crater and were present on different body areas. In general, nodules were located as series of differently sized protrusions extending along the lateral line on both sides of the fish, as well as sensory canals on the head. Cut sections showed a homogeneous, pale white-grey texture. Histologically, the pathological tissue was located in the dermis, occasionally intruding into the hypodermis, and pushing as a space-occupying mass against the underlying muscle tissue without any evident boundaries. The pressure also caused changes in the overlying epidermis, such as atrophy, spongiosis and erosion. In some areas, the epidermis was 1 cell thick and club and goblet cells had completely disappeared. Ultimately, these changes resulted in shallow ulceration. Tumour tissue was characterized by a scant population of spindle or stellate cells, with oval, hyperchromatic nuclei and pale cytoplasm embedded in a copious myxoid matrix. Cells were arranged in fascicles and whorls, extending in a poorly defined manner among the dermal collagen bundles. Occasionally, adipose cells were also detected, mainly in the central portion of the bulges. Myxoid areas appeared rich in metachromatic and alcianophilic mucous ground substance. Reticular fibres and collagenous connective tissue were scarce. Immunohistochemistry (IHC) using antibodies against S-100 and glial fibrillary acidic protein caused a slight positive reaction in neoplastic dendritic cells. High magnification showed the immunostaining to be cytoplasmic in all tumour cells. IHC with anti-calretinin antibody gave only negative results. Macroscopic, histological, histochemical and immunohistochemical findings were consistent with a diagnosis of multicentric myxoma of the dermal nerve sheaths, a tumour not yet reported in fish.

Morphological and histochemical study of intestine in wild and reared European eel (Anguilla anguilla L.).

Diet-related differences between the ratio of intestine length to body size and the enzymatic activity in the intestinal tract of wild and reared European eel (Anguilla anguilla L.) were studied. Compared with reared eel, wild eel showed significantly shorter relative intestine length. For the purpose of histochemical examination, different parts (anterior, middle and posterior) of intestine proper were used. Activities of non-specific esterase, alkaline and acid phosphatase, and aminopeptidase were examined in each segment. All enzymes were present in the intestines of both wild and reared European eel. Fish from both groups showed similar enzyme distribution within the enterocytes, but distribution and intensity of enzyme activity along the intestine vary depending on the group. Generally, reared European eel showed highest enzymatic activity and wider distribution of enzymes throughout all parts of the intestine. These results suggest that different diets could be one of the reasons for observed changes.

Histochemical Analyses of Digestive Enzymes in the Intestine of Adult Large‐Scaled Gurnard (Lepidotrigla Cavillone, Lacepède, 1801)

With 9 figures and 2 tables

Histological investigations of Eimeria infection in large-scaled gurnards, Lepidotrigla cavillone (Lacepède, 1801) from the Novigrad Sea, Croatia

The presence of an Eimeria sp. was found in adult large-scaled gurnards Lepidotrigla cavillone (Lacepède, 1801) from the Novigrad Sea, in Croatia. The detection of Eimeria sp. in the pyloric caeca and intestines of the large-scaled gurnards is also the first report of the parasite in this fish species. The analysis of histopathological changes in the digestive tract led to the conclusion that the parasite could be a serious pathogen in heavily infected large-scaled gurnards.

Variations in Pectoral Girdle Muscles in Dogs

Muscle variations take the form of additional muscle bundle or belly, unusual muscle origin or termination, as well as complete muscle absence. Knowledge of such variations not only has clinical importance for guiding surgery, but also can help reveal phylogenetic relationships. To improve our understanding of muscle variations in dogs, 57 medium‐sized, cross‐breed male and female adult animals were dissected as part of a gross anatomy course between 2005 and 2011. Variations in pectoral girdle muscles were observed in 7 (12.3%) dogs and took the form of an additional muscle bundle in the brachiocephalicus muscle (n = 2), in the omotransversarius muscle (n = 2), in the cervical part of the rhomboideus muscle (n = 2) and in the cervical part of the serratus ventralis muscle (n = 1). Muscle variation was bilateral in only one dog; it involved the omotransversarius muscle. The variations did not seem to be sex dependent. Such variations can appear regularly in dogs and should be taken into consideration during anatomical dissection.

The morphological characteristics of the passive flexor mechanism of birds with different digit layout

Birds possess a mechanism which allows passive flexion of the digits of the hind limbs which consists of two components: “automatic digital flexor mechanism” (ADFM) and “digital tendon-locking mechanism” (DTLM). The aim of this paper was to establish the existence and specificities of those components in examples of birds with anisodactyl (domestic chickens) and zygodactyl (parrots) digit layout using standard anatomical dissection and histological methods. Spatial distribution of the parrots’ muscles with a central role in DTLM (M. flexor digitorum longus and m. flexor hallucis longus) was the same as the chickens’. The plantar position of the fourth digit, which makes the difference between the anisodactyl and the zygodactyl digit layouts, did not cause changes in the position and function of this flexor muscles. The domestic chickens’ tendon sheath ridges, as well as the tendon tubercles of the flexor muscles were less developed while the parrots’ tubercles and ridges were clearly defined and the differences in their morphology were visible. There were no chondrogenic elements or they were barely noticeable in the parrots’ tendons. A potential cause of these distinctions could be the difference in the load which the tendons endure due to the different biomechanical composition. The parrots primarily inhabit trees where they move agilely around by grasping the branches. The Galliformes have a much larger body mass which is a consequence of their life on the ground, so the flexor muscle tendons suffer a greater load than the parrots and the cartilage tissue embedded in the tendon itself could act to distribute the weight of the body borne by the foot and the tendon.

Whale Poaching Detection Based on Microscopic Characteristics of Bottlenose Dolphins’ (Tursiops truncatus) Bone Fragments

Although many countries prohibit whaling, it remains a significant cause of whale population decline. The meal of whales, likely killed during illegal whaling or caught accidentally, can ap-pear in a fish meal as a contaminant detectable by microscopic examination of bone fragments. In order to provide a rigorous basis for such a detection, microscopic characterization of bone fragments of 10 female and 10 male, less than a year to 21 years old bottlenose dolphins (Tur-siops truncatus), a widespread cetacean species herein used as a whale model, was performed and compared to the reference bone fragments of fish, ruminant, poultry and pig. The processing of bones mimicked that used in the production of meat and bone meals, while their description was based on qualitative characteristics, i.e. the shape of a bone fragment ; the shape, density and distribution of osteocyte lacunae, and the distribution and density of canaliculae. Bottlenose dol-phin bone fragments are smoothly contoured ; their elliptical osteocyte lacunae are clearly visible, while the canaliculae radiate from the lacunae in all directions. The comparison of these qualita-tive bone characteristics with that of other vertebrata under study revealed that bottlenose dol-phin bone fragments can definitely be differentiated from that of fish, may be differentiated from that of poultry and pig, but cannot be differentiated from that of ruminants. Measurements of the osteocyte lacunae showed the lacunar length to be strongly associated with animal’s age and lacunar shape, while their width was strongly associated with animal’s gender lacunar shape. The results indicate the possibility of detecting a whale meal admixture in a fish meal using light microscopy, which should be followed by PCR to enable the identification of the admixture source.