Ontogeny and functional histochemistry of the digestive and visual systems and other organs during the larval development of the thick-lipped grey mullet, &lt;em&gt;Chelon labrosus&lt;/em&gt;

Carmen Sarasquete,Juan B Ortiz-Delgado,Gonzalo Martínez-Rodríguez,Manuel Yúfera,Verónica De Las Heras,J Antonio Martos-Sitcha

doi:10.3989/scimar.04091.27b

Abstract

The main ontogenetic and functional changes of the digestive and visual systems of Chelon labrosus during the first three months from fertilization until 99 days post-hatch (dph) are described. An extended slow growth pattern (3.93%) during the first three weeks of larval life was discernible. A long transitional period of mixed endo-exogenous feeding was noticeable until 13 dph. The majority of organ systems and structures (eye, digestive system, liver, pancreas, thyroid and others) were developed and functional before first feeding (mouth opening at 4 dph). First differentiation of gastric glands was detected at 16 dph, with the appearance of a noticeable pyloric muscular portion or typical gizzard and first developed pyloric caeca from 23 dph. The presence of pinocytotic supranuclear vesicles (5 dph) was still visible in the posterior intestine until the third month of life. The eyes exhibited early differentiation and functionality (pigmentation, first cone-type photoreceptors) during the lecithotrophic phase (2 dph), and development of all typical retinal layers containing different retinal cell types was progressively discernible from 16 dph onwards. From this time, rod photoreceptor precursor cells were incorporated into the basal region of the outer nuclear layer, and increases of two types of photoreceptors (cones and rods) were detected from 23 dph.

Highlights

The thick-lipped grey mullet, Chelon labrosus (Mugilidae) is a euryhaline teleost common in estuaries, coastal lagoons, intertidal marshes and earth ponds in the northeastern Atlantic and Mediterranean coasts
Artemia sp. nauplii (0.3-0.5 prey mL–1; Ben Khemis et al, 2006) were supplied from 6 dph, which was gradually replaced with enriched meta-nauplii between 13 and 25 dph (1 prey mL–1) and 0.1, 0.2 and 0.5 mm commercial diets ad libitum (Skretting, Burgos, Spain) which were the only food offered to larvae from 25 dph onwards
The embryo developed as a blastodisc at the animal pole, and the periphery of the blastodisc overgrew the yolk enclosing it to form the gastrula at 5 hours post fertilization

Summary

Introduction

The thick-lipped grey mullet, Chelon labrosus (Mugilidae) is a euryhaline teleost common in estuaries, coastal lagoons, intertidal marshes and earth ponds in the northeastern Atlantic and Mediterranean coasts. This species, together with other mullets, is currently of local importance in extensive aquaculture in some of these habitats (Drake et al 1984, Arias and Drake 1990, Yúfera and Arias 2010). Chelon labrosus is an interesting species to diversify aquaculture, and the success of sustainable productions of the Mugilidae could be a result of their reproductive strategies, food preferences and feeding behaviours (Albertini-Berhaut 1973, Bruslé 1981a,b, Drake et al 1984, Crosetti and Cataudella 1995, Ben Khemis et al 2006, 2013)

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