Embryonic respiration in the dogfish(Scyliorhinus caniculaL.)

Abstract

Oxygen uptake by dogfish eggs showed an exponential increase with age, reaching a value of around 300 /i\ O 2 h" 1 at 15 °C in eggs about to hatch. Oxygen tensions within the egg-case were fairly steady (25-35 mmHg below ambient) in the case of early stage embryos, but later embryos featured much lower (50-80 mmHg below ambient) and variable oxygen tensions. Dogfish eggs were found to be capable of maintaining high oxygen uptake rates at low ambient oxygen tensions throughout development. They survived long periods of severe hypoxia and up to 12 h of anoxia. When embryos were subjected to anoxic conditions, all signs of external physical activity, including breathing, were abolished. After 8 h anoxia, an accumulation of 1-603 ±0-500 and 0084 +0-022 mg of lactate/g wet weight, for embryos and yolk respectively, was observed. No further accumulation was detected after 12 h anoxic exposure. The mean diffusion coefficient measured for oxygen diffusing through the wall of the egg-case was 2-95 x 10" 6 cm 2 s" 1 . No asymmetry of oxygen diffusion through the egg-case was detected. 250 J. M. DIEZ AND J. DAVENPORT MATERIALS AND METHODS Collection and maintenanceAdult dogfish were caught by trawling in Caernarvon Bay, North Wales. The fish were maintained in recirculated, filtered sea water at about 11 °C. Tanks were inspected for the presence of eggs every morning; eggs were collected and left hanging by the tendrils in separate tanks under the same conditions as the adults. Respirometry

Abiotic conditions in cephalopod (Sepia officinalis) eggs: embryonic development at low pH and high pCO2

“…As mentioned, no data on egg fluid pCO 2 and pH is available for other marine organisms; however, judging from the pO 2 versus pCO 2 ratios obtained in our study, in comparison to pO 2 values in-and around eggs or egg masses of other marine animal taxa, it seems likely that many embryos will also be surrounded by fluids of high pCO 2 and low pH: For example, Diez and Davenport (1987) showed that pO 2 values in shark eggs decrease from ca. 18 kPa in early embryos to ca.…”

The evolutionary puzzle of egg size, oxygenation and parental care in aquatic environments

“…embryonic stage) did not influence male ventilation rates or activity patterns. However, since embryonic metabolic demands tend to peak just before hatching [8,46,67,[83][84][85], it is possible that hypoxia impacts embryo survival only towards the end of the brooding period.…”

Growth and Metabolism in the Embryonic White‐Spotted Bamboo Shark,Chiloscyllium plagiosum: Comparison with Embryonic Birds and Reptiles

“…Overall, bamboo shark embryonic development was similar to that of other oviparous elasmobranchs in terms of gross embryo characteristics and respiratory behaviors (Luer and Gilbert 1985;Diez and Davenport 1987;Ballard et al 1993). The major difference between development of bamboo sharks and these other elasmobranchs is that bamboo sharks develop in less than half the time required for temperate species (127 vs. 1300 d, respectively).…”

“…Being nourished solely by a maternally supplied yolk, oviparous sharks develop in a fashion superficially similar to embryonic birds and reptiles. However, unlike birds and reptiles, which are amniotes and exchange gases through vascularized extraembryonic membranes, sharks are not amniotes and must, therefore, actively ventilate their egg case at all but the earliest stages of development (Diez and Davenport 1987;Ballard et al 1993;Thomason et al 1996b;Tullis and Peterson 1998;Leonard et al 1999), although additional flow may be generated by external water currents (Koob and Summers 1996). Recently, Leonard and coworkers (1999) demonstrated that ventilatory movements increased the standard metabolic rate of developing skates (Raja erinacea) by approximately 20%.…”

“…Significant costs associated with embryonic movement could also produce different metabolic patterns in developing oviparous sharks, as compared to birds and reptiles. Data from another elasmobranch, the lesser spotted dogfish (Scyliorhinus canicula), show that oxygen consumption increases exponentially with embryo age (Diez and Davenport 1987), as in altricial birds and snakes. However, the paucity of data on metabolism and growth of embryonic sharks makes it impossible to conclude if this pattern is common to all elasmobranchs.…”