Wednesday, January 19, 2022

[Invertebrate • 2021] Aridulodrilus molesworthae • A New Genus and Species of Earthworm (Oligochaeta: Megascolecidae) from Semi-arid Australia

 Aridulodrilus molesworthae 
 Dyne, 2021

A new genus and species of terrestrial oligochaete, Aridulodrilus molesworthae (Megascolecidae) is described from a new species found in a semi-arid habitat in New South Wales, Australia. The location of this species provides additional evidence that localized landscape and pedologic factors have allowed isolated populations of native earthworms to persist in areas where low rainfall averages were previously thought to preclude their occurrence. The genus has a combination of morphological features that distinguish it from all other Australian genera. While it shares some features with genera in Western Australia, the wide geographic gap (some 2300 km) appears to preclude any close phylogenetic affinity with these taxa.

Live extended specimen of Aridulodrilus molesworthae gen. et sp. nov.

Male field of holotype of  Aridulodrilus molesworthae gen. et sp. nov. 


Megascolecidae Rosa, 1891

Aridulodrilus gen. nov.

Diagnosis. Large worms (over 250 mm in length). Setae more than 15 per segment throughout. Dorsal pores present. Male pores from racemose prostates paired on XVIII. Firm oesophageal gizzard in V; calciferous glands and oesophageal caeca absent; intestinal gizzards and typhlosole lacking. Nephridia meronephric, avesiculate, and astomate, tufted anteriorly. Caudal modifications of the excretory system (e.g., ureters) absent. Spermathecae three pairs, spermathecal diverticula clavate and single; several internal chambers (i.e., multiloculate but not sessile). Penial and genital setae absent. 

Etymology: From the Latin aridulo-drilus—semi-desert worm.

 Distribution. Western New South Wales, Australia (restricted). 

Remarks. The closest generic relative appears to be Austrohoplochaetella Jamieson, 1971, differentiated by the lack, in Aridulodrilus gen. nov., of any caudal excretory system elaboration (such as megameronephridia, nephrostomes, bladders or ureters). Also Aridulodrilus gen. nov. lacks an intestinal typhlosole.

 Aridulodrilus molesworthae sp. nov.

Etymology: The species is named for the manager of the property on which the species was detected—Ms Rosalind Molesworth.

Habitat of Aridulodrilus molesworthae gen. et sp. nov. 

Geoffrey R. Dyne. 2021. A New Genus and Species of Earthworm (Oligochaeta: Megascolecidae) from Semi-arid Australia. Records of the Australian Museum. 73(4);123–129. DOI: 10.3853/j.2201-4349.73.2021.1769