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Recent research has indicated through chemical tagging of some species of decapod crustacean that the mesocardiac, zygocardiac, and pterocardiac ossicles of the gastric mill are retained through molting and contain apparent growth increments potentially indicative of age. Though other recent studies have suggested that in some decapod species, these ossicles are either lost in the stomach exuvia at molting, or are partially resorbed prior to molting. This study investigated the fate of the gastric mill ossicles of Nephrops norvegicus throughout the molt cycle, in order to ascertain their utility for age determination. Wild-caught individuals were immersed in a calcein solution to stain the ossicles, reared in an aquaculture facility, and sacrificed at different stages of the molt cycle. In all individuals sacrificed less than 24 h after molting, the mesocardiac, zygocardiac, and pterocardiac ossicles of the gastric mill were found loose within the stomach of the individual, no longer attached to the stomach wall, among the disintegrated gastroliths. New ossicles are subsequently calcified postmolt to support the gastric mill and stomach wall. The same phenomenon of ossicle loss was also observed in two Austropotamobius pallipes individuals sacrificed 1 h postmolt. In some N. norvegicus individuals sacrificed at varying periods of time postmolt, the calcein stain was reincorporated into the newly calcified ossicles. It is suggested that this is because once the calcifying gastric mill is strong enough to cope with food, the old ossicles and gastroliths are digested, and their calcium, to which the calcein is bound, is resorbed. The results of this study indicate that the growth increments previously observed within the gastric mill ossicles of N. norvegicus are unlikely to be of annual periodicity, but are a result of the postmolt calcification process. It therefore seems unlikely that N. norvegicus can be directly aged using the gastric mill ossicles. This may be the case for a number of decapod crustacean species. [ABSTRACT FROM AUTHOR]

Abstract: The present study was carried out to validate the daily deposition and age estimation by using beak rostrum sagittal sections increments of cultivated Octopus maya (Voss and Solís, 1966). This study validates for first time the periodicity of beak increments by using animals of known age. We analyzed the rostrum sagittal sections (RSS) of upper and lower beaks in 40 juveniles of O. maya divided into four age groups (63, 87, 105 and 122 days) with 10 individuals per group. The animals were fed with a soft diet allowing obtaining age estimations not affected by the beak erosion. At the same time 50 animals were sampled every 20 days until 120 days old to obtain an age-body wet weight (BW) curve which could be compared with the age-BW curve obtained using age estimations from beaks. Co-variance analysis showed no statistical differences between both curves. The number of increments present in the beaks corresponded with the number of days from hatchling. Therefore, it was possible to validate that a growth increment corresponds to a day of life in O. maya, confirming that, up to 122 days old, the beaks counts can be used to determine the age of O. maya. [Copyright &y& Elsevier]

Abstract: Topographical relationships between the mineral and organic components are important to understand the process involved in biomineralisation. We examined nanostructural features of cod (Gadus morhua) otoliths using atomic force microscope (AFM). Acicular aragonitic fibres that form primary increments observed in scanning electron or light microscopy were composed of lamellae, themselves being composite arrangements of round granules (diameter<50nm) surrounded by an organic (?) cortex. The lamellae presented a banding pattern, which might correspond to a growth period of about 15min. Cod otolith granules were similar in size, shape and arrangement to that previously reported for another fish species. The existence of smallest otolith organization units is suggested since granules are themselves composite. Finally, the intra-daily growth rhythm makes it possible to consider very high-resolution biological and environmental reconstructions in the future. [Copyright &y& Elsevier]

The observed variances in monthly weight and length gains of 96 Peruvian infants were compared with predicted variances obtained by applying the reference curve-fitting methods to the same Peruvian data. Predicted variance estimates were significantly less (P < 0.0001) than the observed variances from 2 to 12 mo of age. The extent of underestimation in total variance that occurred when 1-mo growth-increment reference data were generated by curve-fitting and interpolation was approximated. This underestimation, caused by not taking into account infants' random deviations from their own growth trajectories, ranged from 59% to 94% and resulted in misclassification of ≈24-67% of infants as abnormal gainers (below the 5th percentile or above the 95th percentile with respect to existing reference data) in the intervals evaluated. [ABSTRACT FROM AUTHOR]