The AEP strain of Hydra vulgaris is used to generate embryos for production of transgenic Hydra (Wittlieb et al., 2006). AEP produces both sperm and eggs, and does so regularly if it is fed on an appropriate schedule. Most of the time a given sexual polyp contains only testes or eggs, although occasionally a polyp is seen which contains both testes and an egg. About half of the embryos from an AEP self-cross hatch, and do so in 2-4 weeks. The details of how the AEP strain was generated are not completely clear. Everyone agrees that the founders for this strain were a male strain called CA7, collected from Boulder Creek, south of Susanville, California in July, 1988 by Drs. Lynne Littlefield and Carolyn Teragawa and a female strain, called PA1, collected from a pond on the Haverford College campus by Carolyn Teragawa. Boulder Creek drains into the north side of Antelope Lake. Haverford College is in Haverford, Pennsylvania, which is near Philadelphia. There is a single large pond on the campus called the Duck Pond. This is the pond from which PA1 was collected. Lynne and Carolyn were both postdocs in Hans Bode’s lab at UC Irvine at the time the CA7 and PA1 strains were brought into the laboratory. All those involved agree that the initial step in generating the AEP strain was a cross between CA7 and PA1. This cross gave rise to multiple lines designated with letters A, B, C, D, E, etc. In their paper on Hydra embryogenesis (Martin et al., 1997), Vicki Martin et al. mention a male E2 line and a female A5 line, which were derived from crossing CA7 and PA1. Pat Bode recalls that crosses among the letter-designated lines (A, B, C, D, E, etc.) were carried out. It is presumed that an AE line was generated by crossing of an A line and an E line. Which A line and which E line were used in this cross is no longer known. The logical final step in the generation of AEP would have been a cross between the presumed AE line and a P line. So AE could have been backcrossed to PA1 to generate AEP. In an e-mail she sent me in 2005, Vicki Martin said she thought that a line called PA2 was generated from a cross between CA7 and PA1 and that a cross between a PA2 male and a PA2 female gave rise to AEP. This seems unlikely for two reasons. First, Pat Bode is certain about the production of the A, B, C, D, E, etc. lines from a CA7/PA1 cross and she is certain that crosses using those lines were then carried out. Second, Pat’s recollection makes sense in terms of the AEP designation. It seems unlikely that AEP would be chosen as the name if the cross was done as Vicki thinks, and Vicki says she doesn’t remember why the line was called AEP. However, Technau et al. (Technau et al., 2003) report crossing AEP females to PA2 males, indicating that a male line called PA2 existed at one point. The story is further complicated by notes I received from Carolyn Teragawa that list five lines (PA1, PA2, PA3, PA4, and PA5; all male) that she established from animals collected from the Haverford Dock Pond on June 9, 1988. If this male PA1 line is the same as the female PA1 line described above that was used in the initial cross with CA7 to generate AEP, it would have had to have produced females at some point after it was collected. Daniel Martínez obtained a PA2 line from Vicki Martin, which he believes Vicki got from the Bode lab. Daniel amplified the rDNA ITS from this line for phylogenetic analysis, but it has not been used in any published trees. Unless additional documentation is found regarding how the crosses beyond the initial CA7/PA1 cross were carried out, it won’t be possible to determine the complete pedigree of AEP.

REFERENCES

Martin, V.J., Littlefield, C.L., Archer, W.E., and Bode, H.R. (1997). Embryogenesis in hydra. Biol. Bull. 192, 345-363.

Technau, U., Miller, M.A., Bridge, D., and Steele, R.E. (2003). Arrested apoptosis of nurse cells during Hydra oogenesis and embryogenesis. Dev Biol 260, 191-206.

Wittlieb, J., Khalturin, K., Lohmann, J.U., Anton-Erxleben, F., and Bosch, T.C.G. (2006). Transgenic Hydraallow in vivo tracking of individual stem cells during morphogenesis. Proc. Natl. Acad. Sci. U. S. A. 103, 6208-6211.