Despite the lack of an obvious copulatory organ, the reproduction of Latimeria is of the type called "ovoviviparous", which means that it has internal fertilisation, and the fetuses are retained within the mother until they have grown large enough (36-38 cm) to fend for themselves. The eggs are enormous (9 cm in diameter and over 325 g in weight), and the huge yolk supplies all of the nutrients necessary for the growth of the embryo. In 1975, a large female coelacanth in the American Museum of Natural History was found to contain 5 young in individual compartments of the oviduct (uterus). They ranged in length from 301 to 327 mm and had well-developed teeth, fins and scales. Each fetus had a large, flaccid yolk sac attached to its chest. Dr Peter Forey of The Natural History Museum in London recently dissected one of these fetuses and found a 2 mm wide duct that leads directly from the yolk sac into the anterior part of the intestine. This yolk duct serves to move yolk from the yolk sac into the intestine where it is digested by the fetus. The same type of yolk transport into the gut via the yolk duct occurs in pups of ovoviviparous sharks. In some recent publications (Balon et al., 1988; Wourms et al., 1988; Bruton, 1989; Balon, 1991; Wourms et al., 1991) it was suggested (or even stated as a fact) that the reproduction of Latimeria involves "oophagy" or "embryonic cannibalism" (i.e., that the unborn pups feed on eggs or other siblings while in the uterus). According to Heemstra and Compagno (1989), there was no evidence to support this "oophagy" hypothesis, and Dr Forey's examination of a pup (from the original litter of 5 in the American Museum) found that its intestine was full of yolk (which is what one would expect with a direct connection between yolk sac and intestine) and contained "no trace of muscle fibres or anything else that might suggest that it had eaten a sib". Despite the misgivings of Heemstra and Compagno (1989), Wourms et al. (1991) again suggested that "Oophagy, the ingestion of supernumerary eggs by developing young, may well be the major source of supplemental nutrients for coelacanth pups." Speculating from a female that contained 19 ovulated eggs, they calculated that "19 embryos would occupy 7.0 meters of uterine space in a 2.0 meter fish" [the implication being that this is physically impossible]. They then concluded that "At the very most, such a fish could accommodate seven or eight developing embryos, and 11 or 12 eggs would then be superfluous-eggs ... [which] serve as nutrients for the embryos that survive to term". Then, in August 1991 a large pregnant female coelacanth, 179 cm long and weighing 98 kg, was caught by a trawler off Pebane on the northern coast of Mozambique (Bruton et al., 1992). This specimen was given to the natural history museum in Maputo, where it was dissected by the Director, Dr Augusto Cabral, who found that it contained 26 near-term pups, 31-36 cm in length. Thanks to the discovery and preservation of this Mozambique female, we now know that it is indeed possible for a coelacanth to have at least 26 pups in a litter, and the "superfluous-eggs" hypothesis of "oophagy" for the coelacanth is itself superfluous. Two pups from the Mozambique specimen were dissected by Heemstra and Greenwood (1992) and found to contain an internal yolk sac, which is the remnant of the large external yolk sac seen on the younger pups from the American Museum specimen. In the later stages of development, as the yolk supply dwindles, the external yolk sac apparently shrinks and is withdrawn into the body cavity. Some of the Mozambique pups had a small external yolk sac, and in others there was only a flat scar along the ventral midline to show where the yolk sac had been. In view of the large size (31-36 cm) and advanced development of the pups from the Mozambique female, the size at birth for Latimeria is probably about 35-38 cm (Ref. 38228). Juveniles are born after 13 months (Refs. 26162, 38222) or 3 years (Ref. 30865) of gestation period. Thus, females may give birth only every second or every third year.
- Balon, E.K. 1990 Epigenesis of an epigeneticist: the development of some alternative concepts on the early ontogeny and evolution of fishes. Guelph Ichthyol. Rev. 1:1-48. (Ref. 7471)
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