Investigation of ultrastructure and texture changes of fillets of rainbow trout grown under different aquaculture systems.

In this study, the physical structure of fillets of rainbow trout (Oncorhynchus mykiss) grown under different aquaculture conditions was compared. For this purpose, scanning electron microscopy (SEM) analysis, texture profile (hardness, springiness, cohesiveness, gumminess, chewiness), and color measurements (L, a, b, chroma, hue and whiteness) of the fillets of trout taken from two different aquaculture environments were examined. When the texture profile of fillets taken from both environments was compared, it was determined that the hardness (40.30-69.80 N), gumminess (26.85-41.89 N) and chewiness (25.37-36.82 N) values of the fish samples taken from the extensive culture were higher than the samples taken from the recirculated system. The difference between other values was not found to be significant. In parallel with the hardness results, when the SEM images were examined, it was determined that the fillets of the fish taken from the extensive system had a thicker fibril ultrastructure than those from the RAS. The variable environmental parameters and aquaculture duration were observed to have an effect on muscle development, and that especially the long breeding period in the extensive system has a positive effect on the meat structure of the fish. Cultivation in different environments was not determined to have a significant effect on the color values of either the skin or fillet samples. As trout is the leading fish in freshwater production, it is very important for aquaculture to determine the physical changes in the flesh structure of trout according to the growing conditions.

Effects of two host-associated probiotics Bacillus mojavensis B191 and Bacillus subtilis MRS11 on growth performance, intestinal morphology, expression of immune-related genes and disease resistance of Nile tilapia (Oreochromis niloticus) against Streptococcusiniae.

The intensification and diversification of production systems have increased the incidence of diseases, which are usually treated with antibiotics. However, its use should be restricted due to the increasing prevalence of antibiotic-resistant bacteria. Probiotics represent therefore an alternative environmentally friendly strategy for improving growth and disease resistance in aquaculture. Considering that host-derived probiotics may offer greater advantages than those from other environments in terms of safety and efficacy, two potential host-associated probiotic strains (Bacillus mojavensis B191 and Bacillus subtilis MRS11) were used in the present study, which were previously isolated from intestinal mucus of Nile tilapia (Oreochromis niloticus). This study was conducted to assess the effects of dietary administration of two Bacillus strains on growth performance, intestinal morphology, immunity, and disease resistance of Nile tilapia. A total of 375 fish were randomly divided into five groups in triplicate. Nile tilapia were fed a basal diet (control group) or a basal diet supplemented with Bacillus mojavensis B191 (BM) or Bacillus subtilis MRS11 (BS) spores at different concentrations of 1 × 106 (BM6 and BS6, respectively) and 1 × 108 (BM8 and BS8, respectively) CFU/g of feed for 60 days. Moreover, the survival rate of tilapia upon challenge with Streptococcus iniae was determined following the feeding trial. After the feeding trial, the growth performances were significantly improved in all probiotic-fed groups, with the BS8 group being the highest. Light and electron microscopy observations revealed elevated goblet cells, intestinal villus length (except BM8), microvilli length, microvilli density, and perimeter ratio increase in the intestine of all probiotic-fed groups compared with the control group. Regarding the expression analysis, HSP70 gene was only up-regulated in the BM8 group and a general trend of up-regulation of some immune-related cytokines (TGF-ß, IL-10, TNF-α and IL-1ß) was observed in all probiotic-fed groups. Likewise, the best protection against Streptococcus iniae was observed in the BS8 group, followed by BS6, BM6 and BM8 groups. Altogether, dietary probiotic supplementation with BS8 and BM6 may improve growth performance, intestinal morphology, immunity, and disease resistance in Nile tilapia.

Lernanthropid copepods parasitic on marine fishes in Turkish waters, including two new records.

A review of Lernanthropidae (Copepoda: Siphonostomatoida) recorded on marine fish species in the Mediterranean and Turkish seas is presented together with the first records of two species of the genus Lernanthropus de Blainville, 1822 that are new to the Turkish coasts. The newly recorded parasites are: Lernanthropus gisleri van Beneden, 1852 from the gill filaments of Umbrina cirrosa (Linnaeus, 1758) and Lernanthropus callionymicola El-Rashidy & Boxshall, 2012 from the gill filaments of the Red Sea immigrant dragonet Callionymus filamentosus Valenciennes, 1837. General morphology, measurements and key diagnostic characters of both species are presented, based on light and scanning electron microscopy. In addition, some contradictions are noted in previous descriptions of L. gisleri and some newly observed structural details of L. callionymicola are also presented.

The discovery of male Caligus brevicaudatus Scott, 1901 (Copepoda: Caligidae) parasitic on tub gurnard, Chelidonichthys lucerna (Linnaeus) from the eastern Mediterranean.

Caligus brevicaudatus Scott, 1901, a common but poorly known species of parasitic copepod, is redescribed from newly collected specimens of both sexes. The new material was collected from the body surface of tub gurnards, Chelidonichthys lucerna (Linnaeus), caught in eastern Mediterranean waters off the Turkish coast. Inadequately described female structures from earlier descriptions are redescribed and illustrated in detail and the male of C. brevicaudatus is described for the first time. The new material of C. brevicaudatus is compared with material collected by A. Scott and stored in the collections of the Natural History Museum, London. In addition, a voucher specimen of Caligus uranoscopi Vaissière, 1955, stored in the collections of the Muséum National d'Histoire Naturelle in Paris is re-examined. Caligus uranoscopi is recognised as a junior subjective synonym of C. brevicaudatus since it does not differ in any substantive characters.

The discovery of the male of Caligus ligusticus Brian, 1906 (Copepoda: Caligidae) parasitic on the sand steenbras Lithognathus mormyrus (L.) in the eastern Mediterranean.

Caligus ligusticus Brian, 1906 (Copepoda: Caligidae), a species of parasitic copepod originally based on females collected from off Genova, Italy, is redescribed based on newly collected specimens of both sexes. The new material was collected from the inner opercular surface of the sand steenbras Lithognathus mormyrus (Linnaeus) caught in eastern Mediterranean waters off the Turkish coast. Inadequately described female structures from earlier descriptions are re-described and illustrated in detail and the male of C. ligusticus is described for the first time. Key diagnostic characters of C. ligusticus are highlighted by scanning electron microscopy observations. A comparative study of the newly collected specimens of C. ligusticus and material collected by A. Brian and stored in the collections of the Muséum National d'Histoire Naturelle in Paris, is also presented.

Caligus solea n. sp. (Copepoda: Caligidae) parasitic on the common sole Solea solea (Linnaeus) from the north-eastern Mediterranean off the Turkish coast.

A new species of caligid copepod, Caligus solea n. sp., is described from the common sole Solea solea (Linnaeus) caught off the north-eastern Mediterranean coast of Turkey. Both sexes of the parasite were collected from all over the upper body surface of its host. The new species belongs to the macarovi-group of species as established by Boxshall & Gurney (Bull Br Mus (Nat Hist) (Zool), 39:161-178, 1980), with which it shares the following four characters: (i) leg 4 with two-segmented exopod, distal segment carrying three apical spines but no lateral spine; (ii) distal exopodal segment of leg 1 with three plumose setae posteriorly plus four distal margin elements, spine 1 naked, spines 2 and 3 with accessory process and spine 4 about twice length of the others; (iii) females with one-segmented abdomen while males with two-segmented abdomen; (iv) male maxilliped with myxal process opposing the tip of the subchela. However, the new species differs from its congeners within the macarovi-group in the number of sensillae on each papilla on and around the postantennal process, and also in the absence of serrations along the distal margin of the maxilla. This is the twenty-eighth species of Caligus to be reported from the Mediterranean Sea.

Parasitic copepods of the common sole, Solea solea (L.), from the Eastern Mediterranean coast of Turkey.

There is increasing interest in the common sole, Solea solea (Linnaeus), as an alternative fish species in aquaculture in the Mediterranean region, and parasitic copepods are a potential hazard for farmed finfish. This paper provides taxonomic information on two species of sea lice (family Caligidae) collected from S. solea in eastern Mediterranean waters off the Turkish coast. Caligus brevicaudatus A. Scott, 1901 and Caligus apodus (Brian, 1924) were both found and this is the first report of C. brevicaudatus in Turkish waters. The discovery of C. apodus on S. solea is a new host record. Key diagnostic characters of both species are reported, supported by light and scanning electron microscopy observations. During a 12-month survey a prevalence of 28% was recorded for C. brevicaudatus, whereas for C. apodus peak prevalence was much lower (3%).

The discovery of Caligus temnodontis Brian, 1924 (Copepoda: Caligidae) from the bluefish Pomatomus saltatrix (Linnaeus) in the eastern Mediterranean Sea.

The temnodontis variety of Caligus mauritanicus Brian, 1924 described by Brian (1924) is a valid species known only from a single host species, Pomatomus saltatrix (Linnaeus). New material of this species has been examined from the same host fish caught from Abuqir Bay, Alexandria (Egypt), from Iskenderun Bay (Turkey) and from off the coast of South Africa. Using this material, C. temnodontis Brian, 1924 is redescribed and compared with related species. It is most closely related to the Indo-Pacific species C. pagrosomi Yamaguti, 1939.