During the early ontogeny of fish larvae, the accurate development of the visual system plays a key role, because it is involved in locating food, orientation, selection of favorable habitat, and evasion of predators. The structure of the eye of the fish is typical of vertebrates, with some modifications related to the aquatic environment. In the present work, we describe the development of the larval eye of Engraulis anchoita for the first time. Larvae were collected at the Permanent Station of Environmental Studies (EPEA) in coastal waters of the Southwestern Atlantic Ocean during research cruises in 2015 and 2016. We describe the histology of the retina layers, determine the beginning of the functionality of the eye, and discuss a possible synchronization with the development of the digestive tract. This study provides information about the biology of E. anchoita, the most abundant fish species in the southwestern Atlantic Ocean. Also, recent studies have shown responses of the retina and other tissues to the increase in environmental acidity. Therefore, results of this study are also discussed with respect to the possible effect of acidification on the larvae of this species. The continuity of the time series developed at the EPEA will allow monitoring the effect of long‐term environmental and biological variables on the early ontogeny of anchovy in the context of climate change. The high commercial fishing potential of E. anchoita due to its high abundance, as well as its essential role in the trophic web of other commercially valuable fishing resources of Argentina, reinforce the need to continue deepening knowledge about this species. Research highlights: Eyes of Engraulis anchoita larvae are functional from early larval stages. At hatching, the retina is formed by only few layers from which the other layers differentiates during ontogeny. Focal distance increases with larval growth.

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The enzyme L-asparaginase (L-asparagine amidohydrolase, EC 3.5.1.1) has been thoroughly researched by many researchers worldwide because of its immensely useful medical applications. It can catalyze the hydrolysis of L-asparagine to L-aspartic acid and ammonia that is effective for the cure of leukemia, especially for puerile acute lymphocytic leukemia [ALL] and lymphosarcomas. The tumor cells rely on an exogenous supply of Asn for their proliferation, and this enzyme causes selective death of asparagine-dependent tumor cells by depriving them of asparagine. L-Asparaginase is an intracellular enzyme, which is commonly obtained from microorganisms. The L-asparaginases of Erwinia and Escherichia coli have been reported for many years as effective drugs in the treatment of acute lymphoblastic leukemia. E. coli was shown to produce two distinct asparaginases which differ in several properties. The enzyme with the greater affinity, asparaginase II, appears to be located in the periplasmic space between the bacterial plasma membrane and the cell envelope. The present paper discusses the studies carried out for the optimal production of the enzyme from E. coli ATCC 11303. The nutritional requirements and culture conditions affecting biosynthesis of L-asparaginase II of E. coli ATCC 11303 were studied.