Post natal lecithotroph: A new age class in the ontogeny of reptiles

Lecithotrophic (yolk based) nutrition is a well-documented condition for th e embryos of oviparous reptiles. However, the continuation of this nutritio nal state following hatching. here formally defined as postnatal lecithotro phy, has rarely been considered in reptile life history studies or in repti le nutritional strategies. Approximately 50% of the caloric value of yolk l ipids may be conserved as a post hatching reserve for both growth and mobil ity in neonate North American tortoises. A preliminary experiment was desig ned to study if the metabolic dependence oil residual yolk may be quantifie d and the duration of that dependence delimited, Baseline data from tortois e egg yolk established the lipid components available in the yolk prior to hatching. Analysis of blood plasma identified those lipid components presen t in adult tortoises, and finally circulating blood from neonate tortoises was drawn at intervals to monitor ill(, extent to which lipid components ab undant in yolk continue to be utilized. Neonate tortoises subsisting oil re sidual yolk had significantly, higher plasma lipids than neonate tortoises that had been fed, All of the lipid fractions including total lipid, triacy l glycerol, phospholipid, cholesterol and cholesterol esters were significa ntly higher in fasted than in fed tortoises. Also there were significant di fferences in some of the individual fatty acids between fed and fasted neon ates. Prior observations and inferences suggest that this nutritional stage may c ontinue through the first six months following hatching. It may also be att enuated by a secondary conversion of yolk invested energy into fat. Field o bservations indicate that lack of rainfall and associated deficits in avail able forage may make newly emergent neonates in the western and central Moj ave Desert almost entirely dependent on such reserves for their first half year of life. Post natal lecithotroph tortoises may be able to emerge into a dr, September Mojave Desert landscape, disperse rapidly to first shelter, inoculate themselves with fermenting anaerobes through coprophagy, grow, b in-row, and hibernate without ever feeding on any conventional nutritional forage.