Ovoviviparity and viviparity in the Diptera

R. Meier et al., Ovoviviparity and viviparity in the Diptera, BIOL REV, 74(3), 1999, pp. 199-258
Citations number
Categorie Soggetti
Biology,"Experimental Biology
Journal title
ISSN journal
1464-7931 → ACNP
Year of publication
199 - 258
SICI code
The taxonomic distribution and evolution of viviparity in Diptera is critic ally reviewed. The phenomenon ranges from ovoviviparity (eggs deposited at an advanced stage of embryonic development; larva emerges immediately after deposition), through viviparity (larva hatches inside female before deposi tion) to pupiparity (offspring deposited as pupa). Some Diptera are known t o be facultatively viviparous, which is hypothesized to be a step towards t he evolution of obligate viviparity. Obligate viviparity is found to compri se unilarviparity (single large larva in maternal uterus) which evolved man y times independently, the rare oligolarviparity (more than one but not mor e than 12 larvae) and multilarviparity (large numbers of developing eggs or larvae in uterus) which is typical for the two largest clades of viviparou s Diptera. Unilarviparity is either lecithotrophic (developing larva nouris hed by yolk of egg) or pseudo-placental (larva nourished by glandular secre tions of mother). Viviparity has clearly evolved on many separate occasions in Diptera. It is recorded in 22 families, and this review identifies at l east 61 independent origins of viviparity. Six families appear to have vivi parity in their ground-plan. Some families have a single evolution of vivip arity, others multiple evolutions. Guimaraes' model for the evolution of vi viparity in Diptera is tested against phylogenetic information and the adap tive significance of viviparity is reviewed in detail. Possible correlation s with life-history parameters (coprophily, parasitism, breeding in ephemer al plant parts, malacophagy and adult feeding habits - especially haematoph agy) are analysed critically, as are potential advantages (shorter larval l ife, less investment in yolk by mother, protection of vulnerable stages, be tter access to breeding substrates, predation on competitors). Morphologica l constraints, adaptations and exaptations are reviewed, including the prov ision of an incubation space for the egg(s), the positioning of the egg(s) in the uterus, and maternal glands. The main morphological adaptations incl ude greater egg size, reduction of egg respiratory filaments, thinning of c horion, modified larval respiratory system and mouthparts, and instar skipp ing. Female morphology and behaviour is particularly strongly modified for viviparity. The terminalia are shortened, the vagina is more muscular and t racheated, and the ovaries of unilarviparous species have a reduced number of ovarioles with alternate ovulation. Many of the final conclusions are te ntative, and a plea is made for more detailed morphological and experimenta l study of many of the viviparous species. Viviparity in Diptera provides a fascinating example of multiple parallel evolution, and a fertile field fo r future research.