A new locality is reported for the Iranian subterranean fishes Garra typhlops and Garra lorestanensis (and probably Eidinemacheilus smithi), near the village Tuveh in the Dez River drainage. The site is 31 km straight‐line distance away from the only other known locality where these species have been observed previously. The finding suggests the presence of a sizeable subterranean aquifer system in the Tigris drainage extending for between 31 and 162 km.

The size frequency distribution for age structure, lengthweight (LWR) and length-length (LLR) relationships of six populations of Platycephalus indicus along the Persian Gulf coastal waters in Iran are reported. A total of 180 P. indicus specimens were studied from six localities including Charak, Bandar-Abbas, Shif, Motaf, Khur-Musa and Bahrekan. The maximum standard length recorded for the studied populations ranged between 300 to 510 mm and the b values of the length-weight relationships ranged between 3.0 and 3.2. The obtained results indicated isometric growth patterns for all these populations with the exception of the Bahrekan population which showed a positive allometric growth pattern. The LLR between the total and standard lengths in these populations were found to be highly significant. The results would be useful for further studies on population assessment and sustainable conservation of the fish along the Persian Gulf coastal waters.

Background. Five species of Ponticola have hitherto been recognized among freshwater gobies in the Ponto-Caspian basin. In 2014 a number of specimens representing this genus were collected in northern Iran. The detailed morphological and karyological study of those gobies collected revealed signifi cant differences between them and their known congeners. The aim of this study was to describe these fi sh as a new species from the Caspian Sea basin. Materials and methods. The fi sh specimens were collected in August 2014 at two localities of the Sefi d-Rud River drainage, and in the Gisum River, Guilan Province, northern Iran. In total, 18 specimens were used for karyological study following a previously described method. Both karyotyped and intact specimens were then morphologically investigated using characters developed for study on gobiids, and particular for freshwater Caucasian gobies. The comparative materials were specimens from museum collections, as well as published descriptions, illustrations, and measurements of other species. Results. Ponticola iranicus sp. nov. differs from its congeners in a set of the following features: D 1 VI, D 2 I/(14½) 15½-17½, A I/10½-13½; nape scaled completely, scales cycloid; cycloid scales covering upper part of opercle; lateral line system with posterior sub-orbital row d 2 continuous; predorsal area uniform, dark grey; fi rst dorsal fi n with oblique black stripe between fi rst two or three rays; short dark grey strip on upper part of pectoral fi n base; karyotype consisting of 46 acrocentric chromosomes. Conclusion. All known Ponto-Caspian gobies demonstrate mosaic pattern of morphological and karyological features that presumes their polyphyletic origins. Further phylogenetic studies by molecular genetic methods are necessary for identifi cation of their marine ancestors and clarifying of common trends in the evolution of the Ponto-Caspian goby group.

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The application of nanoparticles in various industries has grown significantly in recent years. The aims of this study were evaluation effects of silver nanoparticles (AgNPs) on survival rate and tissues (Gills) of Guppy (Poecilia reticulate) as a model of the freshwater organism. For this purpose, 90 mature fish were exposed to a different level of AgNPs for 96 hr. Data analyzed showed there was a significant correlation between fish mortality rate and AgNPs concentrations. Histological assays showed some typical tissue damages such as hyperplasia, hypertrophy, hyperemia, hemorrhage, and necrosis. Moreover, fish exposed to a lethal concentration of AgNPs showed some clinical signs, such as increasing operculum movement, swimming near the water surface, anxiety, and death with open mouth. The results of the present study showed that AgNPs can have toxicity effects on Guppy, also to sub-lethal concentrations, leading to several tissue damages and reduced survival rate of fish.