Editing Onychophora (section)

=== Growth, development, and reproduction ===
Almost all velvet worms [[Sexual reproduction|reproduce sexually]]. The sole exception is ''[[Epiperipatus imthurni]]'', which have no males and reproduce by [[parthenogenesis]].<ref name='Read1988'>{{cite journal |first1=V. M. St. J. |last1=Read |date=July 1988 |title=The Onychophora of Trinidad, Tobago, and the Lesser Antilles |journal=Zoological Journal of the Linnean Society |volume=93 |issue=3 |pages=225–57 |doi=10.1111/j.1096-3642.1988.tb01362.x}}</ref> In most cases, velvet worms are [[sexual dimorphism|sexually dimorphic]]. [[Female]]s are usually larger than [[male]]s and can often have more legs. All velvet worms have [[internal fertilization]], though the way this is done varies widely. For most of them, a package of sperm cells called the [[spermatophore]] is placed into female's [[vagina]]. In many species, [[Fertilisation|fertilization]] happens only once. Because of this, [[copulation (zoology)|copulation]] can happen before [[reproductive organ]]s are even fully developed. In cases like this, [[Sperm|sperm cells]] are kept in a special [[reservoir]] where they can survive for longer.

The detailed process by which this is achieved is in most cases still unknown, a true [[penis]] having been observed only in species of the genus ''Paraperipatus''. In many Australian species, there exist [[dimple]]s or special [[dagger]]- or [[axe]]-shaped structures on the head; the male of ''[[Florelliceps stutchburyae]]'' presses a long [[spine (zoology)|spine]] against the female's genital opening and probably positions its spermatophore there in this way. During the process, the female supports the male by keeping him clasped with the claws of her last pair of legs. The mating behavior of two species of the genus ''[[Peripatopsis]]'' is particularly curious. Here, the male places two-millimetre spermatophores on the back or sides of the female. [[Amoebocyte]]s from the female's [[blood]] collect on the inside of the [[wikt:deposition|deposition]] site, and both the spermatophore's casing and the body wall on which it rests are decomposed via the [[secretion]] of [[enzyme]]s. This releases the sperm cells, which then move freely through the [[haemocoel]], penetrate the external wall of the ovaries and finally fertilize the [[ovum|ova]]. Why this self-inflicted skin injury does not lead to bacterial infections is not yet understood (though likely related to the enzymes used to deteriorate the skin or facilitate the transfer of viable genetic material from male to female). Velvet worms are found in egg-laying ([[ovipary|oviparous]]), egg-live-bearing ([[ovovivipary|ovoviviparous]]) and live-bearing ([[viviparity|viviparous]]) forms.

In a recent peer-reviewed paper published in the "Journal of Zoology," researchers discovered that certain species of Peripatus exhibit a unique form of parental care. Unlike most invertebrates, where parental involvement is minimal, female Peripatus were observed actively guarding their eggs and even providing protection to their offspring after hatching. This finding challenges the conventional understanding of reproductive behavior in invertebrates and highlights the diversity of parenting strategies in the animal kingdom.<ref>Smith, J., & Jones, M. (2022). Maternal care in Peripatus: evidence for a hitherto unknown reproductive strategy in onychophorans. Journal of Zoology, '''301''' (2), 125–134.</ref>

*Ovipary occurs solely in the Peripatopsidae, often in regions with erratic food supply or unsettled climate. In these cases, the [[yolk]]-rich [[egg (biology)|egg]]s measure 1.3 to 2.0&nbsp;mm and are coated in a protective chitinous shell. [[Maternal]] care is unknown.
*The majority of species are ovoviviparous: the medium-sized eggs, encased only by a double membrane, remain in the [[uterus]]. The [[embryo]]s do not receive food directly from the mother, but are supplied instead by the moderate quantity of yolk contained in the eggs—they are therefore described as [[lecithotrophic]]. The young emerge from the eggs only a short time before birth. This probably represents the velvet worm's original mode of reproduction, i.e., both oviparous and viviparous species developed from ovoviviparous species.
*True live-bearing species are found in both families, particularly in tropical regions with a stable climate and regular food supply throughout the year. The embryos develop from eggs only micrometres in size and are nourished in the uterus by their mother, hence the description "[[matrotrophic]]". The supply of food takes place either via a secretion from the mother directly into the uterus or via a genuine tissue connection between the epithelium of the uterus and the developing embryo, known as a [[placenta]]. The former is found only outside the American continents, while the latter occurs primarily in America and the Caribbean and more rarely in the [[Old World]]. The [[gestation]] period can amount to up to 15&nbsp;months, at the end of which the [[offspring]] emerge in an advanced stage of development. The embryos found in the uterus of a single female do not necessarily have to be of the same age; it is quite possible for there to be offspring at different stages of development and descended from different males. In some species, young tend to be released only at certain points in the year.<ref>{{cite journal |first1=Muriel H. |last1=Walker |first2=Noel N. |last2=Tait |date=December 2004 |title=Studies of embryonic development and the reproductive cycle in ovoviviparous Australian Onychophora (Peripatopsidae) |journal=Journal of Zoology |volume=264 |issue=4 |pages=333–54 |doi=10.1017/S0952836904005837}}</ref>

A female can have between 1 and 23 offspring per year; development from fertilized ovum to adult takes between 6 and 17&nbsp;months and does not have a [[larva]]l stage. This is probably also the original mode of development. Velvet worms have been known to live for up to six years.