Thursday, 24 September 2009

Porcine Intersex

I've blogged about Equine Intersex before. Intersex conditions are found in all mammals though - reptiles and birds too for that matter. Amphibians. Fish. In some species, those which are dichogamous, they get a natural and complete sex-change.

Here's one genetic Intersex condition I wasn't aware of though:
Investigations into the relative abundance of Intersexual pigs (Sus sp.) in the Republic of Vanuatu.
The existence and great abundance of a unique form of pig intersexuality was verified on the northernmost islands of Vanuatu.

Morphological examinations were conducted on 54 pigs from the islands of Malo, Ambae, and Aore. Through blood analysis, estradiol and testosterone levels were derived. Subsequent comparisons of the estradiol/testosterone ratio yielded results consistent with "maleness". Fifty-one dental and mandibular measurements of the Vanuatu Sus. sp. specimens plotted within the feral swine target group.

Behaviorally, the Vanuatu intersex pig exhibits periods of aggressiveness that generally coincide with a sow in heat. When encountered in the "bush", the naravé (local name for the intersexual pig) is a stronger and more aggressive adversary than the "normal" native wild pig. Six gross dissections yielded totally male internal sex organs. Four separate graduations or phases of the intersexual condition are described according to their external genitalia. The phases of intersexuality appeared to be an inherited trait. Certain sows (called falé-ravé) are known intersex producers and 20% of their offspring will be intersexual.

A similar account is given by the Sakau people, but their interesting classification of the Naravé separates them into 7 groups according to their external genitalia. They are as follows(4):

1. Ndré-rasa - The "feminine" intersex - The external appearance is essentially that of the female, except for the presence, in adults, of tusks. The testes are situated within the abdomen. 2. Ndré-runedh - "sprouting coconut" intersex - Small projection by the vulva, with testicles sometimes descended into scrotum. 3. Ndré-narsogh - "sewn up" intersex - occasionally the urinary projection is situated in the scrotal region but the urinary external orifice is occluded. Soon after birth locals would make a small incision to allow normal urination. 4. Ndré-ghara - "fruit bat" intersex - the urinary projection is long and situated at the back of the testicles resembling the genitalia of the local bat. 5. Ndré-nau - "rat" intersex - Genitalia resemble those of the rat. 6. Ndré-ghor-ghor - "hidden" intersex - The urinary projection is smaller like that of the Ndré-nau, but it is not visible when viewed from behind. 7. Ndré-selet - "worm" intersex - There is a further enlargement of the corpus cavernosum moving the projection yet further on the abdomen with a resultant "worm-like" extrusion from the end.

These, as with the Authors classifications, commonly overlapped each other and at times were difficult to categorize. There does, however, seem to be a genetic influence involved in the inheritance of these conditions as certain families of animals in specific localities show there is clearly an inherited tendency to certain phases of this abnormality.
As with Intersex conditions generally, there are huge gaps in our knowledge here. It would seem that this is an ideal area to experiment in, a relatively small genetic pool, ethical considerations only appropriate to highly intelligent animals rather than people.... I hope the Southwest Pacific Research Foundation gets additional funding to follow this up.

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