Sunday, 5 September 2021

Maratus nemo: A new species of wetland Peacock Spider from South Australia.

Peacock Spiders, Maratus spp., are a unique group of Jumping Spiders (Salticidae) from Australia, noted for the bright colours and elaborate mating displays of the males. This behaviour, combined with the development of relatively cheap digital cameras capable of recording the activities of small spiders, has made them stars on social media, which in turn has led to more study time being focused on the group by arachnologists; of the 91 currently recognised species in the genus, 76 have been described in the last decade. Males of the genus have a distinctive, and often brightly coloured, plate on their opisthosoma (rear body section), which can be erected during mating displays, as well as an elongated third pair of legs used for signalling. 

In a paper published in the journal Evolutionary Systematics on 25 March 2021, Joseph Schubert of Museums Victoria, and the Harry Butler Institute at Murdoch University, describes a new species of Peacock Spider from the wetlands of South Australia.

The new species is named Maratus nemo, in reference to the character Nemo in the Disney film Finding Nemo, the colouration of the males resembling that of this character. The species was first observed by Sheryl Holliday of Nature Glenelg Trust, who posted pictures of the Spiders on social media. The species was discovered living in the Mount Burr Swamp, about 9.5 km to the southeast of Mount McIntyre, and subsequently also found close to the Topperwein Native Forest Reserve, about 14 km to the east of Nangwarry.

The males of Maratus nemo resemble those of the 'Maratus personatus' species group, however, it is currently unclear if this is a true clade (group of organisms including all the descendants of a shared common ancestor), or an example of convergent evolution. Like these species, males of Maratus nemo lack distinctive colouration or flaps on the opisthosoma, but instead has a brightly coloured mask of scales surrounding the eyes, in the case of Maratus nemo these being bright orange with white markings. The remainder of the body is dark brown, and thickly covered with white hairs. Females are light brown in colour, with a lighter covering of off-white hairs. Males range from 4.10 to 4.25 mm in length, females are slightly larger at 5.12 mm.

Living male Maratus nemo. (A) Anterolateral view, (B) lateral view, (C) dorsal view, (D) anterior view, (E) anterolateral view, and (F) anterior view. Schubert (2021).

During courtship the male sits on a leaf, where he raises one of his third legs and waves it slowly. If a female approaches, he raises both third legs and waves them more vigorously, while at the same time bobbing his opisthosoma up and down, causing the leaf to vibrate and generating an audible noise. This courtship has only been observed in captivity, and may be more complex in the wild.

Living female Maratus nemo. (A) Dorsolateral view, (B) dorsal view, (C) anterolateral view, (D) lateral view, (E) posterolateral view, and (F) anterior view. Schubert (2021).

The species has only been found at two locations in South Australia to date. Both locations are ephemeral wetlands, an environment in which Peacock Spiders have not previously been recorded, with the Spiders being found on the leaves of marsh vegetation sitting in shallow water.

Habitat of Maratus nemo in the vicinity of Mount McIntyre, South Australia. (A) Ephemeral wetland complex habitat at Mount Burr Swamp. (B) Marshy vegetation from Mount Burr Swamp. (C) Maratus nemo nov. male in situ. (D) Maratus nemo female in situ. Sheryl Holliday in Schubert (2021).

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