Assisted Reproductive Technologies in a New World Primate, the Common Marmoset Monkey (Callithrix jacchus)
The marmoset monkey (Callithrix jacchus) is a small New World primate that is used for biomedical research. It has a 28-day ovarian cycle, produces two or more embryos per cycle, and is easily kept and bred in captivity. Its cycle can be synchronized using prostaglandin F2α, which resets the cycle to the beginning of the follicular phase,2 so that a number of individuals can be cycling synchronously. This affords the opportunity to perform embryo collections and transfers from a number of individuals on the same day. These characteristics make the marmoset a very favorable model for reproductive research.
Until recently, collection of embryos and gametes from marmoset monkeys has required laparotomy, an invasive procedure that can only be performed once in any animal used for research purposes. Additionally, collection of sperm has involved anesthesia of males for electroejaculation, or involvement of a female to wash ejaculated sperm from the vagina. Here we report the development of non- or minimally invasive assisted reproductive technologies for marmosets.
Non-surgical collection and transfer of embryos have been reported previously.1,3 Briefly, females are lightly anesthetized and placed in a restraining device that secures them in dorsal recumbency. Vaginal dilation is achieved by introduction of a glass speculum, and the cervix is visualized using illumination provided by an otoscope. A 19-ga cannula and stylet are placed at the cervical os and gently guided into the uterus by transabdominal palpation. For embryo collection, the contents of the uterus are flushed with 3–5 ml of phosphate-buffered saline, or, for embryo transfer, approximately 2 µl of collection medium containing one or two embryos is deposited in the uterine lumen.
Laparoscopic collection of marmoset oocytes has been developed. Traditional laparoscopes are large and awkward to use in an animal as small as a marmoset monkey. The procedure reported here uses an otoscope for the laparoscopic procedure. The otoscope is introduced through an incision in the abdominal wall, and the reproductive tract can be viewed directly through the plastic otoscope head. The device for follicular aspiration consists of a 20-ga needle attached to a short length of tubing and uses a 10-ml syringe to afford controlled, gentle suction of the follicular contents into a 5-ml tube. Using this technique, 158 follicles have been aspirated, and 81 (51%) oocytes have been collected.
Sperm collection from marmosets is performed using a Ferticare™ vibrator (ILTS Inc.). A small piece of silicon tubing is inserted into the vibrator and used as an artificial vagina. Once males are habituated to the procedure, ejaculates can be reliably collected in an average of 9 seconds. These non- or minimally invasive procedures decrease the stress involved for each procedure and increase the efficient use of marmosets for reproductive research. Additionally, these procedures may be effective in assisted reproduction programs for endangered marmosets and tamarins.
1. Marshall, V.S., J.K. Kalishman, and J.A. Thomson. 1997. Nonsurgical embryo transfer in the common marmoset monkey. Am. J. Primatol. 26: 241–247.
2. Summers, P.M., C.J. Wennink, and J.K. Hodges. 1985. Cloprostenol-induced luteolysis in the marmoset monkey (Callithrix jacchus). J. Reprod. Fertil. 73: 133–138.
3. Thomson, J.A., J. Kalishman, and J.P. Hearn. 1994. Non-surgical uterine stage preimplantation embryo collection from the common marmoset. J. Med. Primatol. 23: 333–336.