Authors' Contribution GA conceived and designed the study and wrote the manuscript. AM did experimental work. AG analysed the data. SF and LD edited the manuscript. SSAA assisted in brooder collection.

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The morphology and histomorphology of the tongue and the histochemistry of the lingual glands of eight specimens from four species of Ligurian Sea odontocetes (Stenella coeruleoalba, Tursiops truncatus, Grampus griseus, and Ziphius cavirostris) were studied. The shape of tongues and the appearance of their dorsal surfaces differed between species. The lingual glands differed in size, distribution, and histochemistry by species. In S. coeruleoalba and G. griseus, a strong alcianophilic mucous material was detected in the lingual glands, while neutral and acidic mucous substances were observed in the most proximal secretory acini. In G. griseus, small simple alveolar apocrine glands were also found, and the duct of the serous lingual glands in Z. cavirostris is of apocrine type. Numerous mechanoreceptors were observed. Only the tongue of the young specimens showed marginal papillae: their histomorphological composition is consistent with the hypothesis that they create a tight seal between the tongue and the roof of the cavity in order to create suction. This comparative study suggests that differences in tongue morphology and in the morphology and histochemistry of lingual glands might be related to feeding habits.

Assessment of optimum salinity level (10‰, 15‰, 20‰, 25‰ and 30‰) for growth performance, food conversion, body composition and survival rate of Nile tilapia, Oreochromis niloticus (mean body weight 4.5±0.5 g) were investigated. Fingerlings were randomly distributed into the glass tanks (60 x 30 x 45 cm each). Ten fish per tank were stocked with two replications. Fish were fed with commercial floating pellet (35% protein) with 3% of total biomass day-1 for 50 days. Results showed that the growth increment reared on 10‰-20‰ salinity were significantly highest in term of weight gain, WG % of initial weight, daily weight gain, specific growth rate, condition factor and survival rate than those reared on 25‰ and 30‰. Feed conversion ratio was found similar in all levels which is not significantly different (P> 0.05). Whole body composition i.e. protein (53.16%-53.26%), moisture (71.16%-71.26%), lipids (2.49%-2.52%), ash (4.16%-4.18%) contents of fish whole body were not significantly (P>0.05) different at varying salinity levels. Mean values of water quality were found acceptable for tilapia i.e. temperature 28.42±0.08°C, dissolved oxygen 7.48±0.06 mg/L, pH 7.64±0.04 and ammonia 0.022±0.004 mg/L. Relationship between log body weight and log total length of the the fish shows that Nile tilapia fingerlings reared from 10‰-20‰ was significantly (P <0.05) higher than 25% and 30% salinity levels. Present study suggests that Nile tilapia can be reared up to 20% salinity to get good growth and higher survival rate.

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Authors' Contribution GA conceived the idea, designed the study and wrote the manuscript. AM did the experimental work. AG prepared the blood slides. SF analysed the data and LG edited the manuscript.

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