Stages of embryonic development in the Atlantic cod Gadus morhua

Abstract

The early development of the Atlantic cod, Gadus morhua was studied from fertilization until first-feeding. Multiple families were reared at 7 degrees C and a developmental staging series was prepared using morphological landmarks visible with the light microscope. Stages were named rather than numbered to allow for future additions and broadly grouped into larger time intervals called periods. The most useful staging features were found to be initially cell number, and later in development, somite number. The mean cell cycle time for the first six cleavages was 135 min and the linear regression equation for development of somites(s) over time (t) was s = 0.29t - 18.14. The segmentation period began at 220 h postfertilization (hpf), and unlike some other teleosts, the addition of new somites continued throughout the majority of embryonic development, until just prior to hatching. Hatching occurred at 256 hpf, after which individuals remained motionless at the water's surface, undergoing negative phototaxis only after the first day posthatch. The first-feeding stage was reached at the end of the third day posthatch, subsequent to development of a functional jaw and hindgut. This staging series provides an essential baseline reference for future experiments involving developing cod embryos and for the aquaculture industry.

Specific expression and regulation of glucose transporters in zebrafish ionocytes

“…When GLUT2 is taken as an example, the mRNA expression was particularly high in the hypothalamus and hindbrain of rainbow trout (O. mykiss), suggesting a role in the glucosensing pathway (34), while the expression in zebrafish brain was relatively low (compared to other tissues). In addition, the glut2 expression was low in muscles of Atlantic cod (G. morhua), supporting a minor role of Cori cycle in fish muscle energy metabolism (14). However, the conversion of lactate to glucose via the Cori cycle was up to 35% in the resting eels, indicating a substantial involvement of the Cori cycle in the eel muscles (6).…”

“…Immunoreactions with anti-mammalian GLUT1 antibodies were detected only in the brain and heart of Nile tilapia (Oreochromis nilotica) (48). Molecular cloning was used to identify orthologs of the mammalian and/or avian GLUT1-4 in fish species, including rainbow trout (Oncorhynchus mykiss) (22,23,30,32,38), sea bass (Dicentrarchus labrax) (39), common carp (Cyprinus carpio) (37), grass carp (Ctenopharyngodon idellus) (50), Atlantic cod (Gadus morhua) (14), coho salmon (Oncorhynchus kisutch) (3), and zebrafish (Danio rerio) (19). However, it is unclear whether other GLUT isoforms exist in fish, and little is known about the GLUTs and their functional roles in energy supply for osmoregulatory regulatory organs and ionocytes.…”

Sex dimorphic expression of five dmrt genes identified in the Atlantic cod genome. The fish-specific dmrt2b diverged from dmrt2a before the fish whole-genome duplication

“…Samplings of eggs and larvae comprised unfertilised eggs, newly fertilised eggs, late blastula stage (3days post fertilisation, dpf), 8 somite stage at late gastrulation (6dpf), 10-somite stage (7dpf), end of somitogenesis (14 dpf), hatching (21 dpf), feeding larvae of 5 mm body length (12 days post hatch, dph) and larvae of 10-15mm body length (35 dph). The embryonic stages were determined according to Hall et al (2004) and Gorodilov et al (2008). Larvae and adult fish were anaesthetised using metacaine (NMD, Oslo, Norway) prior to sampling, and the adult fish were killed by cranial concussion.…”

Untitled

“…Vis ion is fundamental for early develop ment, as it allo ws spatial orientation and swimming ability (Gisbert 1999;Petereit et al, 2008), as well as fo raging and predation avoidance (Evans & Browman 2004). In A. chalcoide, eye pig mentation occured on 2 DAH, prior to the mouth opening (3DAH) and exogenous feeding (6DAH), which might be attributed to the need to develop a function visual system before the first feeding (Hall et al, 2004). In many species such as Dover sole Solea solea (Boulhic and Gabaudan 1992), walleye Stizostedion vitreum (Marty et al, 1995), striped trumpeter Latris lineate (Trotter et al, 2001) and discus Symphysodon spp.…”