A Temperature-Dependent Index of Mitotic Interval (τ₀) for Chromosome Manipulation in Paddlefish and Shovelnose Sturgeon

Abstract

A temperature-dependent measure of the mitotic interval (TO) can help standardi/e chromosome manipulation in tish eggs. A tau unit (TO) is the duration in minutes of one mitotic cycle during synchronous embryonic cleavage. It is measured over a range of temperatures, and the resulting relationship of TO to temperature can be used to anticipiate developmental events that are affected by temperature. Optimum induction of chromosome manipulation requires development of a specific treatment of egg shocking for each species. Timing of shock is a critical variable, but pretreatment incubation temperature affects the rate of development and thus the optimum absolute time for shocking. Mitotic intervals (TO) are reliable indicators of developmental rates over normal temperatures for egg incubation, and thus can be used to estimate optimal times for chromosome manipulation. Mitotic intervals for paddletish Polyodon spathula and shovelnose sturgeon Scaphirhynchus platorynchus were estimated by averaging the duration of the second and third embryonic divisions (twocell to four-cell and four-cell to eight-cell stages). Mitotic intervals (TO) for paddletish ranged from 74 ± 2.8 min (mean ± SD) at 16 C to 52 ± 1.4 min at 20°C; T O for shovelnose sturgeon was 66 ± 2.5 min and 45 ± 1.1 min at these temperatures.

Duration of synchronous egg cleavage cycles at different temperatures in Siberian sturgeon (Acipenser baerii)

“…At similar temperatures and within the species-specific optimal range of this parameter, the duration in minutes of the mitotic interval of Siberian sturgeon eggs is similar to those reported in Scaphirhynchus platorynchus, A. gueldenstaedtii and A. stellatus (Rubinstein et al 1997;Shelton et al 1997), but higher in comparison with some teleost species such as cyprinids or clupeids. The above-mentioned differences in the rate of development are related to egg size and the meroblastic and incomplete cleavage of teleost eggs, whose developmental rates are generally higher than those of vertebrates with holoblastic (complete cleavage) eggs, such as chondrosteans, lampreys and amphibians (Saat and Veersalu 1996a).…”

Temperature-dependent Index of Mitotic Interval (τ0) for Chromosome Manipulation in Korean Rose Bitterling Rhodeus uyekii

“…The Dettlaff unit is the duration in minutes of one mitotic cycle during early synchronous embryonic cleavage, or the interval between two consecutive cell divisions (Saat and Veersalu, 1996a;Shelton et al, 1997). When measured over a range of temperatures, the relationship of τ 0 to temperature as determined by regression analysis can be used to predict developmental events that are influenced by temperature within a single species and between species with similar spawning biology (Dettlaff, 1986).…”

“…When measured over a range of temperatures, the relationship of τ 0 to temperature as determined by regression analysis can be used to predict developmental events that are influenced by temperature within a single species and between species with similar spawning biology (Dettlaff, 1986). To date, mitotic intervals (τ 0 ) have been used to estimate the optimal times for chromosome manipulation in a variety of species such as the paddlefish Polyodon spathula, shovelnose sturgeon Scaphirhynchus platorynchus, common carp Cyprinus carpio, tench Tinca tinca, Black plaice Pleuronectes obscures, and black crappie Pomoxis nigromaculatus (Flajšhans et al, 1993;Shelton and Rothbard, 1993;Mims et al, 1997;Shelton et al, 1997;Gomelsky et al, 2000;Park and Im, 2010). We determined egg development by artificial fertilization as a part of pattern industrialization and also assessed temperature-related τ 0 and cleavage rates to establish the most efficient procedures for chromosome manipulation in Korean rose bitterling.…”

Chromosome preparation in fish: effects of fish species and larval age

“…In turn, mitotic rate is a factor influenced by species and environmental parameters (Shelton et al 1997). By comparing metaphase chromosome numbers and mitotic rates in different life stages of Cynoglossus semilaevis, Shao et al (2010) found a higher mitotic rate in the larvae compared to the juveniles and adults.…”