From here you can download images for research purposes. Please click a stage on the left and then select an embryo to get more information.

All embryos were measured, photographed, and drawn, and then their relative stage of development was determined. After this, embryos were sectioned into slices of 6 microns (0.006 mm) using a microtome. Each section was mounted on microscope slide, and stained using standard histological stains (pigments). Then all sections were digitized using an Olympus BX40 microscope and an Olympus CC-12 digital camera. These images were saved as TIFF files and then converted to JPG images for more convenient use on the web. Some of the smaller embryos consist of only a few hundreds of sections, but the larger ones consist of thousands of images. All sections are available on our website, even though some are preserved less then perfectly.

Since we do not know the exact age (in days) of an embryo, we followed the common practice in embryology to divide the entire developmental history of an embryo/fetus into stages. Stage 1 is the earliest stage (soon after fertilization), and higher stages reflect older and larger embryos. At the last stage the fetus is basically a miniature of the newborn dolphin. Stages are differentiated based on external and internal features of the embryo. We use the stages as the organizational principle behind the DLDD.

Generally, developmental stages in mammals are compared to the stages of human development, so called Carnegie Stages. The Carnegie Stages are described in detail by O'Rahilly and Muller (1987) and additional information is presented by Butler and Juurlink (1987). An excellent website describing human and comparative mammalian development as well as the staging process was compiled by Dr. Mark Hill (http://anatomy.med.unsw.edu.au/cbl/embryo/OtherEmb/Cstages.htm). We used the Carnegie system as the staging system for our dolphin embryos. The best overview of development in Stenella attenuata was published by Šterba et al., (2000). However, these authors, did not use the Carnegie system in their work.

Below is a table of embryos available in our collection, staged using the Carnegie system:

Stage Main Characteristic Embryo TL CRL Carnegie 9 neural folds fusing LACM 94633 5.8   Carnegie 10 neural folds fusing LACM 94730   3.9 Carnegie 11 two branchial arches LACM 94741   4.1 LACM 94674   4.7 Carnegie 12 otic pit, fore/hindlimbbuds LACM 94789   3.3 LACM 94767   5.5 Carnegie 13 lens placode, C-shape LACM 94733   5.4 LACM 94657   6 LACM 94815   6.2 LACM 94628   6.7 LACM 94735   6.5 LACM 94619   8.6 Carnegie 14 handplate formed LACM 94617   7.8 LACM 94701   8.5 LACM 94594   8

Stage Main Characteristic Embryo TL CRL Carnegie 15 handplate formed LACM 94706   8 LACM 94746   9.6 LACM 94613   8.8 Carnegie 16 eye pigmented LACM 94651   11 LACM 94770   12.6 LACM 94784   15.8 Carnegie 17 digital rays LACM 94715   17.9 LACM 94670   17.5 LACM 94650   23.5 Carnegie 18 eyelids forming LACM 94634   21.9 Carnegie 19 LACM 94817 62   Fetus LACM 94683 86   LACM 94679 97   LACM 94671 95   LACM 94646 114   LACM 94592 160

Reference:
Butler, H., and B. H. J. Juurlink, 1987. An atlas for staging mammalian and chick embryos. CRC Press Inc.
O'Rahilly, R., and F. Muller, 1987. Developmental stages in human embryos. Carnegie Institution of Washington, Publication 637.
Šterba, O., M. Klima, B. Schildger. 2000. Embryology of dolphins: stageing and ageing of embryos and fetuses of some cetaceans. Advances in Anatomy, Embryology, and Cell Biology 157:1-133.