Ooperipatellus nickmayeri

Ooperipatellus nickmayeri
Scientific classification
Kingdom:	Animalia
Phylum:	Onychophora
Family:	Peripatopsidae
Genus:	Ooperipatellus
Species:	O. nickmayeri
Binomial name
Ooperipatellus nickmayeri Oliveira & Mayer, 2017

Ooperipatellus nickmayeri is a species of oviparous velvet worm in the family Peripatopsidae. This species is larger than any other in the genus Ooperipatellus . With a body size exceeding 60 mm in females and 30 mm in males, these velvet worms can be more than twice as long as other species of this genus. ^[1]

Discovery

This species was first described by the biologists Ivo de Sena Oliveira and Georg Mayer in 2017 based on ten specimens, including a male holotype, three female paratypes, and six other specimens (five females and one male). These specimens were collected from rotting logs and leaf litter in a small fragment of forest at an elevation of 545 meters near the Lyell Highway between Tarraleah and Wayatinah in the Central Highlands region of Tasmania. The authors of the original description named this species for the six-year old son (Nick Mayer) of one of the authors, who suggested a stop along the road during which the authors discovered this species in 2013. ^[1] The holotype is deposited in the Queen Victoria Museum and Art Gallery in Launceston, Tasmania. ^[2]

Description

These velvet worms have 14 pairs of legs in both sexes, with the last pair reduced in size but used for walking. Each foot features three complete spinous pads, with the first and third pads smaller than the second. Most legs also feature a fourth fragmented pad. The nephridial tubercle on the fourth and fifth leg pairs is located in the third pad, dividing the pad into two unequal parts. Each foot features paired claws and three distal foot papillae (one anterior, one medial, and one posterior). The males of this species feature crural tubercles on leg pairs 6 through 13. These tubercles are smooth at the base, with no scales, but feature cone-shaped tips with tiny scales. ^[1]

These velvet worms vary in color from blue to predominantly orange-brown, with a light blue ventral surface. Each antenna features 30 to 32 rings, with tan or orange bands on every fourth ring starting with the 15th most distal ring and ending with ring 27 or 31. The slime papillae are also tan or orange. A furrow runs down the middle of the back. The dorsal integument features dermal papillae arranged into 12 complete plicae (transverse ridges) per segment. The gonopore in the male is cruciform, with the transverse slit longer than the longitudinal slit. The ovipositor in the females is large and conspicuous, with a genital opening in the form of a longitudinal slit at the distal end. The anus is located at the terminal end of the body in both sexes. The males of this species feature a pair of anal gland openings in front of the anus. The spinous pads, the crural tubercles and the genital pad in males, and the ovipositor in females are all whitish or light orange. ^[1]

Notwithstanding the large body size, which distinguishes this species from others in the same genus, this species exhibits many of the traits that characterize this genus. These features include oviparous reproduction, 14 leg pairs in each sex, females with a well-developed ovipositor, males with a cruciform gonopore, and the absence of any modified head papillae or head organ. Phylogenetic analysis based on molecular data confirms the placement of this species in the genus Ooperipatellus. ^[1]

This species also exhibits a set of features aside from its large size that distinguish these velvet worms from other species in this genus. These features include a distinctive color pattern, including the sequence of bands on the antennae, the number of plicae per segment, and the form and number of the crural tubercles in males. Furthermore, karyological analysis reveals a distinct karyotype for this species, with a heteromorphic pair of sex chromosomes (XY) and the greatest number of chromosomes (2n = 50 XY) reported to date for a species in the family Peripatopsidae. ^[1]

Phylogeny

In 2017, a phylogenetic analysis based on molecular data placed O. nickmayeri in a clade with an undescribed Tasmanian species (Ooperipatellus sp. 5), indicating that O.nickmayeri is more closely related to this Tasmanian species than to two other Tasmanian species ( O. cryptus and O. decoratus ) and the mainland Australian species O. insignis, three species that together form a separate clade in the same genus. ^[1] In 2025, the specimen providing the molecular data for Ooperipatellus sp. 5 was identified as a specimen of O. spenceri, ^[3] suggesting that O. nickmayeri and O. spenceri are closely related. The type localities of O. spenceri and O. nickmayeri are more than 88 km apart, and the molecular evidence separates these two velvet worms on relatively long branches in a phylogenetic tree, suggesting that these two close relatives are distinct species. ^[1]

Distinguishing these two close relatives based on morphology requires more information from a comprehensive revision of O. spenceri. These species might be distinguished based on the spinous pads on the feet, for example, which are whitish or pale orange in the species O. nickmayeri. ^[1] In the species O. spenceri, these pads are mostly brownish yellow, but the distal pad and the distal and lateral edges of the middle pad are blue. ^[4] Furthermore, the slime papillae are orange or tan in O. nickmayeri but white in O. spenceri. ^{[1] [4]} Little is known, however, about intraspecific variation in these color patterns in O. spenceri. ^[1]

References

1. Oliveira, Ivo de Sena; Mayer, Georg (2017-06-01). "A new giant egg-laying onychophoran (Peripatopsidae) reveals evolutionary and biogeographical aspects of Australian velvet worms" . Organisms Diversity & Evolution. 17 (2): 375–391. Bibcode:2017ODivE..17..375O. doi:10.1007/s13127-016-0321-3. ISSN   1618-1077. S2CID   10859202.
2. Oliveira, Ivo de Sena (2023-11-16). "An updated world checklist of velvet worms (Onychophora) with notes on nomenclature and status of names". ZooKeys (1184): 133–260. Bibcode:2023ZooK.1184..133O. doi: 10.3897/zookeys.1184.107286 . ISSN   1313-2970. PMC   10680090 . PMID   38023768.
3. Museum of Comparative Zoology, Harvard University. "MCZbase MCZ:IZ:131364 specimen record | MCZbase". mczbase.mcz.harvard.edu. Retrieved 2025-08-02.
4. Baehr, Martin (1977). "Über einige Onychophoren aus Australien und Tasmanien mit Beschreibung einer neuen Art und Anmerkung zur Stellung von Ooperipatus paradoxus Bouvier, 1915". Zoologische Jahrbucher. Abteilung fur Systematik, Geographie und Biologie der Tiere (in German). 104: 9–19.