Cooks’ cave millipede  (Pseudotremia cookorum)

This species has not yet been classified by the IUCN Red List (3); however it is classified as Critically Imperiled (G1) by NatureServe (4).

Cooks’ cave millipede is named in honour of William and Gayle Cook, the owners of Little Mouth Cave, where this species was discovered during surveys between 1995 and 1998 (1) (5). Possessing the typical millipede form, the body of Cooks’ cave millipede is composed of numerous hard, ring-like segments. Each segment bears two pairs of legs, with the exception of the first and last segments, which are legless, and the second, third and fourth segments, which only possess a single pair (6). Like many subterranean animals (7), the body of Cooks’ cave millipede appears to be unpigmented, although when magnified, its segments possess a light greyish-purple sheen, with a white glossy area in-between (1). The eyes of Cooks’ cave millipede are composed of 15 to 17 simple, light-detecting lenses called ocelli. These are grouped into five or six irregular rows, forming a darkened, roughly triangular region on each side of the head, just above the antennae (1) (6).

Cooks’ cave millipede is only found in southern Indiana, U.S.A., where it is restricted to a small number of caves, which lie in the south-western region of the Mitchell Plain in Harrison County (1).

A cave-dwelling species, Cooks’ cave millipede may be found on bare flowstone or on mudbanks bordering subterranean streams (1).

As a recent discovery, relatively little is currently known about the biology of Cooks’ cave millipede. Nevertheless, like most millipedes, this species probably feeds on detritus, which is likely to have been deposited by underground streams or by rainwater that has drained from the surface. Living in the darkness, Cooks’ cave millipede has little use for vision, and instead relies on its antennae, which not only help this species to feel objects, but also detect chemical signals in its environment (8).

Millipede reproduction involves the male transferring sperm to the female using specially modified legs called gonopods, after which, the female lays numerous eggs. The eggs hatch into a legless, pupoid stage, which then moults into a more developed form called the first “stadium” which has legs, but no ocelli. With each subsequent moult, the young millipede grows larger, gaining additional segments, legs and ocelli (8).

While there are no known threats to Cooks’ cave millipede at present, it has a highly restricted range and its overall population is likely to be relatively small (4). Consequently, a small-scale adverse event could potentially lead to this species’ extinction.

The discovery of this rare species was made possible by a three year survey, initiated by The Nature Conservancy in Indiana, of all wildlife found within caves in the Blue River basin of southern Indiana (5). The Nature Conservancy of Indiana is now working to ensure that the important sites within this region are properly managed to preserve the unique wildlife that they support (5) (9).

To learn more about conservation efforts in southern Indiana visit:

• The Nature Conservancy in Indiana:
  www.nature.org/wherewework/northamerica/states/indiana