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E-mail: whamlett@nd.edu
RESEARCH INTERESTS:
1. Comparative Structure and Function of the Oviducal Gland in Chondrichthyes
We are studying the structure and function of the oviducal glands from chondrichthyes. Species currently under study include Raja erinacea, Raja eglanteria and the holocephalan elephantfish of Australia, Callorhynchus milii (oviparous and lays an egg case), Squalus acanthias, Pristiophorus nudipinnis, Pristiophorus cirratus (aplacental viviparous and forms a temporary candle case that dissolves in the uterus), Rhizoprionodon terraenovae and Mustelus canis (placental viviparous and forms a permanent egg membrane that is incorporated into the placenta), Carcharias taurus (aplacental, oophagous and intrauterine cannibal) and the stingrays Dasyatis americana and Urolophus jamaicensis (aplacental viviparous and does not form an egg covering as such). We are interested in sperm viability, storage and nutrition in the female reproductive tract and the simultaneous function of egg covering production.
2. Evolution of Viviparity and Regulation of Placentation in Sharks
There are three principal modes of fetal/embryonic nutrition in vertebrates, viz. 1) vitellogenesis, or the hepatic preformation of energy-rich precursors stored in oocytes prior to ovulation; 2) histotroph, nutrient substances supplied to the embryo in viviparous animals by secretory activity of the uterus; and 3) placenta, the direct provision of nutrients by a maternal-fetal vascular connection. The first method is the most widely distributed in vertebrates, and can be found in live-bearing as well as egg-laying species. During the course of evolution, a progressive shift from vitellogenesis to placentation can be seen in those groups in which viviparity has evolved. This shift in the mode of provision of energy stores has been accompanied by egg yolk reduction as placentation has developed and become more complex. In eutherian mammals, yolk has been eliminated and the developing young are dependent primarily upon placental transfer. During the interval after fertilization and before the establishment of the placenta, a period of embryonic dependency upon uterine secretions (histotroph) exists. During this period, uterine cells secrete complex nutritive substances for fetal consumption. Although the processes of vitellogenesis, histotroph production and placentation are interrelated, studies of these processes have only been carried out in a few species. Light microscopic, ultrastructural analyses, lectin histochemistry and cytokine assays are being carried out on the ovary, uterus, placenta and umbilical cord during gestation in an effort to document the tissue response to endocrine stimulation. In collaboration with Dr. Carolyn Jones, University of Manchester, United Kingdom we are investigating the glycosylation expression of the placenta and uterus in Mustelus canis using lectin histochemistry. Other work with Dr. Luana Paulesu, University of Siena, Italy focuses on the identification of interlukins and their receptors in the uteroplacental complex of M. canis.
3. Aplacental Viviparity in Stingrays
Stingrays are aplacental anamniotes that develop without a placental connection. Embryos are initially nourished by yolk sac contents. As the yolk is depleted, the yolk sac diminishes and is incorporated into the embryo's abdominal wall. Concurrent with ovarian development the uterine mucosa develops specializations that provide nutrients for further fetal development. The uterus develops vascularized appendages termed trophonemata that completely cover the interior surface of the uterus. Trophonemata are spatulate extensions that function in providing oxygen, removing wastes and supplying nutrient materials. After the initial yolk reliant period, the developing young rely on uterine secretions termed histotroph or "uterine milk." Preliminary studies utilizing gel electrophoresis indicate that histotroph is rich in both lipid and protein. The embryos/fetuses ingest this material which generally accounts for a 3,000 to 5,000% weight increase during development. The degree to which histotroph contributes to fetal development is unparalleled amongst the vertebrates. Early functional differentiation of the fetal alimentary tract allows for digestion and assimilation of histotroph. Electron microscopic, histochemical and biochemical analysis of histotroph secretion is currently being pursued in collaboration with Dr. Edward McKee, Department of Biochemistry, Indiana University School of Medicine.
4. Reproductive Biology of the Elephant Fish, Callorhynchus milii, in South Australia
We are conducting the first comprehensive study of the reproductive biology in any chimaeroid fish by investigating the normal developmental biology of the male and female elephant fish, Callorhynchus milii. We are especially interested in spermatozeugmata formation in the male and sperm storage in the oviducal gland of the female. This work is being carried out in collaboration with Terry Walker, Marine & Freshwater Resources Institute, Queenscliff, Victoria, Australia.
BOOKS AND DEDICATED JOURNALS:
• Hamlett, W.C. (Editor). 1987. Elasmobranchs as Models in Human Biology, Arch. Biol. (Bruxelles) 98: 1-162.
• Hamlett, W. C. and B. Tota (Co-Editors). 1989. Evolutionary and Contemporary Biology of Elasmobranchs, J. Exp. Zool., Suppl. 2, Alan R. Liss, Inc., New York, 198 pages.
• Hamlett, W. C. (Editor) 1992. Reproductive Biology of South American Vertebrates, Springer-Verlag, New York, 328 pages.
• Hamlett, W. C. and John Rasweiler, IV (Co-Editors). 1993. Comparative Gestation and Placentation in Vertebrates, Part I. Chondrichthyes, Osteichthyes, Amphibia, Reptilia and Marsupilia. J. Exp. Zool., Vol. 266, no. 5, Alan R. Liss, Inc., New York, 138 pages.
• Hamlett, W. C. and John Rasweiler, IV (Co-Editors). 1993. Comparative Gestation and Placentation in Vertebrates, Part II. Monotremata and Eutheria. J. Exp. Zool., Vol. 266, no. 5, Alan R. Liss, Inc., New York, 181 pages.
• Hamlett, W.C. and Ramon Munoz Chapuli (Co-Editors). 1994. Comparative Cardiovascular Biology of Lower Vertebrates. J. Exp. Zool., Vol. 275, nos. 2-3, Alan R. Liss, Inc., New York, 251 pages.
• Hamlett, W.C. (Editor). 1997. From field to laboratory: Elasmobranchs as Contemporary Biological Models. Proc. 5thIndo-Pacific Fish Conf., Noumea.
• Hamlett, W.C. and D.P. Knight. (Co-editors). 1998. Comparative Biology and Morphology of the Oviduct and Uterus in Non-mammalian Vertebrates. J. Exp. Zool., Vol.282, nos. 4-5, Alan R. Liss, Inc., New York, 229 pages.
• Hamlett, W. C. (Editor). 1999. Sharks, Skates, and Rays: The Biology of Elasmobranch Fishes, Johns Hopkins University Press.
• Hamlett, W.C. (Editor). 2001. Comparative Biology of Sperm Storage in Vertebrates. J. Exp. Zool. (in press).
• Hamlett, W. C. (Editor). 1999. Sharks, Skates and Rays: Biology of Elasmobranch Fishes, Johns Hopkins University Press, 544 pages.
• Hamlett, W. C. (Editor). 2002. Comparative Biology of Sperm Storage in Vertebrates. J. Exp. Zool. 292: 109-216.
• Hamlett, W. C. (Editor). 2005. Reproductive Biology and Phylogeny of Chondrichthyes: Sharks, batoids and chimaeras. Science Publishers, Enfield, NH, USA, 562 pages.
RECENT PUBLICATIONS:
• Hamlett, W. C. 2001. Reproduction in fish. In: Encyclopedia of Life Sciences, Macmillan Reference Limited, London (electronic publication).
• Sever, D. M. and W. C. Hamlett. 2002. Female sperm storage in reptiles. J. Exp. Zool. 292: 187-199.
• Sever, D. M., W. C. Hamlett, R. Slabach, B. Stephenson and P. A. Verrell. 2002. Internal fertilization in the Anura with special reference to mating and female sperm storage in Ascaphus truei. In: B. Jamieson, ed., Reproductive Biology and Phylogeny of the Anura.
• Cateni, C., L. Paulesu, E. Bigliardi, and W. C. Hamlett. 2003. The interlukin 1 (IL-1) system in the uteroplacental complex of a cartilaginous fish, the smoothhound shark, Mustelus canis. Reproductive Biology and Endocrinology 2003, 25 ( peer reviewed electronic journal, http://www.rbej.com/content/1/1/25).
• Smith, R. M., T.I. Walker and W.C. Hamlett. 2004. Microscopic organization of the oviducal gland of the holocephalan elephant fish, Callorhynchus milii. Mar. Freshwater Res. 55: 155-164.
• Jones, C. J. P. and W. C. Hamlett. 2004. Structure and glycosylation of the term yolk sac placenta and uterine attachment site in the viviparous shark Mustelus canis. Placenta 25 (10): 820-828.
• Hamlett, W.C., C. J. P. Jones, C. Cateni, F. C. Vandy and L. Paulesu. 2004. Mustelus canis, the smooth dogfish shark as a model for immunoprivileged sites in yolk sac placentation and sperm storage. In L. Paulesu (ed.), Signal Molecules in Animal and Human Reproduction, pp. 1-21, Research Signpost, Kerala, India.
• Jones, C. J. P., T. I. Walker, J. Bell, M. Reardon, C. E. Ambrosio, A. Almeida and W. C. Hamlett. 2005. Male genital ducts and copulatory appendages in Chondrichthyans. In: W. C. Hamlett (ed.), Reproductive Biology and Phylogeny of Chondrichthyes: sharks, batoids and chimaeras. Science Publishers, Inc., Enfield, NH, USA., pp. 361-393.
• Hamlett, W. C., G. Kormanik, M. Storrie, B. Stevens and T. I. Walker. 2005. Chondrichthyan parity, lecithotrophy and matrotrophy. In: W. C. Hamlett (ed.), Reproductive Biology and Phylogeny of Chondrichthyes: sharks, batoids and chimaeras. Science Publishers, Inc., Enfield, NH, USA., pp. 395-434.
• Hamlett, W. C. C. J. P. Jones and L. R. Paulesu. 2005. Placentatrophy in sharks. In: W. C. Hamlett (ed.), Reproductive Biology and Phylogeny of Chondrichthyes: sharks, batoids and chimaeras. Science Publishers, Inc., Enfield, NH, USA., pp. 463-502.
• Hamlett, W. C., D. P. Knight, F. Peirera, J. Steele and D. Sever. 2005. Structure and diversity of the oviducal gland in Chondrichthyes. In: W. C. Hamlett (ed.), Reproductive Biology and Phylogeny of Chondrichthyes: sharks, batoids and chimaeras. Science Publishers, Inc., Enfield, NH, USA., pp. 301-336.
• Hamlett, W. C. 2005. Yolk sac and uterine specializations for gestation in chondrichthyans with emphasis on uterolactation in stingrays and placentation in sharks. In: Viviparous Fishes, Harry J. Grier and Mari Carmen Uribe (editors), New Life Publications, Homestead, Florida, pp. 255-270.
• Hamlett, W. C. 2005. Morphogenesis of the selachian placenta. In: M. Giuntina (ed). Morphodynamics of Cells, Tissues and Reproduction. A Malgighi Book in Memory of Prof. Pietro M. Motta. Italian Journal of Anatomy and Embryology, 110 (Suppl.), n.2: 175-181.
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