Psolus griffithsi – Griffiths’ sea cucumber

Psolus griffithsi – Griffiths’ sea cucumber ©FAO/M. Lipperi

Griffiths’ sea cucumber is a small beige-grey sea cucumber with a dorsal surface covered with imbricating scales.

The discovery

In January 2007, a Dr. Fridtjof Nansen transboundary fisheries survey was conducted off the west coast of South Africa to map the distribution and estimate the abundance of two commercially important hake species. As part of the survey, two PhD students from the University of Cape Town collected benthic species from the trawl samples as a pilot study on this fauna. The specimens were stored at the University for further study. A few years later, Professor Charles Griffiths and Dr Louise Lange, aware that their colleague Dr Ahmed Thandar was an expert on the sea cucumber fauna of southern Africa, informed him of the presence of several specimens in the University’s collection. Further investigation led to the discovery of two new species, Pseudostichopus langeae and Psolus griffithsi, from the deep waters of South Africa.

Features and characteristics

Griffiths’ sea cucumber is a small species, about 25 mm long, with a broad front and narrower back. Its top surface is slightly arched, and is covered with slightly overlapping scales (about ten from mouth to anus) which are larger in the centre and smaller on the sides. The mouth is located slightly above and faces forward, surrounded by five large, grainy oral valves. Tiny pod-like structures are visible between the valves. The anus is on the top, raised, and surrounded by five similar valves, with some podia nearby. The underside is flat with two rows of tube feet along the sole, the outer row being tiny and the inner row larger with suckers. The colour is a uniform beige-grey.

Sea cucumbers, like Psolus species, live on the ocean floor where they play an important role in cleaning up by feeding on detritus and organic material, contributing to the health of marine ecosystems. They possess tiny suction-cup-like feet (podia) to move along the ocean floor and help them stay anchored to the substrate.

Many sea cucumbers, and likely those in the Psolus genus, have a unique defence strategy. When threatened, they can expel their internal organs to confuse predators, a process called evisceration. They can later regenerate these organs. Most sea cucumbers reproduce sexually. They are typically dioecious, meaning they have separate sexes (male and female). During the breeding season they release their eggs and sperm into the water and the fertilization happens externally: the sperm meets the eggs in the open water. Other sea cucumbers can also reproduce asexually through fragmentation. This means that if a sea cucumber loses part of its body (such as through evisceration), it may regenerate a new individual from the severed part.

Several sea cucumber species hold significant commercial value. They are considered a delicacy in many cultures, particularly in Asia, where they are considered a luxury food item and are believed to have health benefits, including promoting vitality and improving circulation. Some species are studied for their potential use in marine biotechnology. Due to their commercial value, growing attention is being paid to sustainable harvesting practices to ensure that sea cucumber populations remain healthy and are not overexploited.

An identification guide of commercially important sea cucumbers of the world was released by FAO in 2023.

Geographical distribution

Psolus griffithsi is only known from one specimen collected at a depth of 407 m off the west coast of South Africa (34°37.9’ south, 18°18.7’ east)