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Charles Kramer


Dr. Kramer is most interested in the investigation of the neuroendocrine control of reproduction in teleost fishes with a particular emphasis upon the hypothalamo-pituitary-gonad axis. His earlier work focused on the genetic control of size polymorphism and time of sexual maturation in the pygmy swordtail, Xiphophorus pygmaeus. He was able to show that a sex linked gene controlled the differentiation of both somatrotrops and gonadotrops in the pituitary gland which accounted for differences in growth rate and age of maturity among the different morphs of Xiphophorus.
Professor Kramer’s later work focused on the neuroendocrine control of female to male sex reversal in the protogynous marine fish, Thalassoma bifasciatum.. In this species, sex change is initiated by social cues.He has shown that the social stimulus triggers an internal signal that is responsible for the transformation. Dr. Kramer has traced the signal to the level of the hypothalamus. Undoubtedly, the initial site of action probably lies at a level above the hypothalamus. Professor Kramer has carried out additional studies on sperm storage in the live bearing poeciliid Poecilia reticulata (guppy) as a representative of the Family Poeciliidae.

Dr. Kramer’s most recent work has focused on the putative role of the rodlet cell as an immune effector cell in both saltwater and freshwater species.


PhD, New York University

MS, New York University

BS, Richmond College

Scholarship and Publications

Qama, E., J. Blaize, W. J. L’Amoreaux and C.R. Kramer     (2009). Rodlet cell distribution and activity in the gills of laboratory-maintained and wild-caught Fundulus  heteroclitus. In Vivo,  31: 16-23.

Kramer,C.R., A.J. Kramer and A. Konovalov (2005). Rodlet cell distribution in the gall bladder epithelium of  Fundulus heteroclitus . J. Fish Biology, 67: 555-560.

Kramer, C.R. and H. Potter (2003). Rodlet cells in the posterior intestine of embryos and neonates of two poeciliid species. J. Fish Biology, 62:1211-1216.

Kramer, C.R. and H. Potter (2002).  Ultrastructural observations on rodlet-cell development in the head kidney of the southern platyfish, Xiphophorus maculates (Teleostei: Poeciliidae). Canadian Journal of Zoology, 80:1422-1436.

Koulish, S., C.R. Kramer and H.J. Grier (2002). Organization of the male gonad in a protogynous fish, Thalassoma bifasciatum (Teleostei: Labridae).  J. Morphology, 254: 292-311.

Potter, H. and C.R. Kramer (2000). Ultrastructural  observations on sperm storage in the ovary of the platyfish, Xiphophorus maculatus (Teleostei: Poeciliidae): The role of the duct epithelium. J. Morphology, 245:110-129.

Kramer, C.R. and M.A. Imbriano (1997). Neuropeptide Y (NPY) induces gonad reversal in the protogynous bluehead wrasse, Thalassoma bifasciatum. J. Exp. Zool., 279: 133-144.


Contact Information

Office: Building 6S Room 143
Fax: 718.982.3852