Peripatopsis sedgwicki

Peripatopsis sedgwicki is a species of velvet worm in the Peripatopsidae family. Also known as the Tsitsikamma velvet worm, this species has a narrow geographic distribution in South Africa but is especially abundant in the indigenous forest of the Tsitsikamma mountains. Recent phylogenetic analysis suggests that Peripatopsis sedgwicki is a species complex that contains three clades, each with a distinct geographic distribution, including at least one clade that may represent a novel species.

Discovery
This species was first described under the name Peripatus dewaali by the Dutch zoologist Max Weber in 1898 based on specimens he collected near the town on Knysna in the Western Cape province of South Africa. In 1899, the South African zoologist William F. Purcell provided a more detailed description of this species based on a male and eleven females that he found in 1896 in rotten wood in the forest and under heaps of weeds on farms near the town of Knysna. He named this species Peripatopsis sedgwicki for the British zoologist Adam Sedgwick. Although Peripatopsis sedgwicki is a junior synonym of Peripatus dewaali, authorities favor the name Peripatopsis sedgwicki based on its long usage, deeming Peripatus dewaali to be a nomen oblitum and designating Peripatopsis sedgwicki a nomen protectum.

Description
This species varies from blue-tan green to bright orange and brown violet. Although Purcell described Peripatopsis sedgwicki with 20 leg pairs, which was long considered characteristic of this species, a more recent study finds that this species has either 19 or 20 leg pairs in most populations, while a discrete population in the Fort Fordyce Nature Reserve in the Eastern Cape province has either 22 or 23 leg pairs. The last leg pair (the genital pair) in this species features a claw (like those on the pregenital pairs) and is well developed compared to those in some other species in the genus Peripatopsis. The last leg pair, however, is smaller than the preceding leg pair and reduced more in the male than in the female. This species is relatively large: Females range in size from 12 mm to 68 mm in length, whereas males range from 10 mm to 46 mm in length.

Reproduction and life cycle
Like other velvet worms in this genus, this species exhibits matrotrophic viviparity, that is, mothers in this genus retain eggs in their uteri and supply nourishment to their embryos, but without any placenta. Females of this species produce eggs with almost no yolk, and embryos develop large "trophic organs" or "trophic vesicles" that may function as means to absorb nourishment from the mother. The female of this species gives birth to her first batch of young when she is about two years old. About a month before the birth of each batch, the next batch of eggs are fertilized. The young reach their maximum size when they are about three years old. These velvet worms have a life span of about six to seven years.

Phylogenetic analysis
A phylogenetic study of this species published in 2017 analyzed a sample of 65 specimens collected from eleven localities. The analysis indicates that P. sedgwicki contains three allopatric clades: One clade is narrowly confined to an area in the Western Cape province near the type locality Knysna (found at three localities: Homtini, Diepwalle, and Garden of Eden), a second clade is distributed more broadly, found in several locations in the Eastern Cape province (Khoisan Village, Essenbos, Ladyslipper, Port Elizabeth, Zuurberg, and Rivendell Farm) and one location in the Western Cape province (Natures Valley) near the border between the two provinces, and a third clade is limited to the Fort Fordyce Nature Reserve in the interior of the Eastern Cape province. The Western Cape and Eastern Cape clades each have 19 or 20 leg pairs, but the Fort Fordyce clade has 22 or 23 leg pairs. The results suggest that at least the Fort Fordyce clade is probably a separate species, but further analyses are necessary for a taxonomic description.