Discovering new species from South Africa’s oceans

By Jannes Landschoff*, PhD student, University of Cape Town Tweet

The research vessel Africana is gently tossed on the waves as its trawl net is slowly and cautiously hauled from the cool deep waters below.

The abundance of circling albatrosses and bobbing seals around the Department of Agriculture, Forestry and Fisheries’ (DAFF) research vessel signals a rich catch today.

Up until a few years ago there would only have been fishery biologists on board to capture important data for assessing the health of fish stocks, and on such occasions as today, to get particularly excited about the bizarre-looking deep-sea fish trawled from below 500 m.

However, since 2011, SAEON have been collaborating with DAFF on these trawl fisheries research surveys and have now established a protocol to include invertebrate monitoring as part of the survey. Since the South African fish fauna is now comparatively well-known, major biological discoveries nowadays mostly take the form of new species of benthic invertebrates (animals without backbones, like starfish and crabs, that live on the seafloor).

Monitoring benthic invertebrate communities

Over the past two decades it has become good practice in fishery science not only to monitor the sizes of fish stocks, but also to account for the health of ecosystems as a whole. This ecosystem approach to fisheries (EAF) includes monitoring benthic invertebrate communities (e.g. crabs, starfish, gastropods and corals), for which the South African shelf region is vastly under-sampled, particularly where sampling requires trawling deeper than 500 metres.

The poor knowledge about the marine offshore and deep-sea invertebrate fauna means that every specimen from the catch could be a significant new discovery to science!

From the invertebrate laboratory of the R/V Africana, PhD student Jannes Landschoff patiently observes as the net is chaotically emptied and a good metric ton of strange-looking animals spill out. On the deck, the crew and ‘fish team’ sort the fish by species and size, their hands working in synchrony and with a well-established conveyor belt-like routine.

During this process, it is important that all the fragile invertebrate specimens are quickly and cautiously placed into bins to avoid damage. Finding a new species is dependent on quickly spotting the unusual amidst the common animals.

A single intact specimen of a rare species can mean an exciting scientific discovery, but animals are often easily crushed on deck by the sheer mass of a trawl catch. Maintaining a clear head in the turmoil of 25 people sorting a ton of fish aboard a rolling ship, is vital.

All the invertebrate species are collected from deck, and transported to the laboratory, where they are identified, counted and weighed and the data captured into the DAFF and SAEON databases. Afterwards, the common species are released.

Since invertebrates don´t have a swim bladder, which expands and bursts from the huge pressure difference as they are brought to the surface from deep water, they stand a good chance of survival when handled with care and if set free timeously.

Documenting rare specimens

Rare specimens are kept and preserved for detailed examination back on land and are later accessioned at the Iziko South African Museum in Cape Town. One of the most important documentation methods is to take scientifically meaningful photographs of specimens.

Given that the often-diagnostic colour patterns fade rapidly in ethanol and most early researchers only received specimens preserved in ethanol or formalin, the historical descriptions of the majority of species do not include enough information about the colour of a live animal. Trying to capture this important information requires taking photographs onboard a moving vessel, not an easy feat! A number of adjustments and some specialist equipment are required for the task.

During the 2016 September/October South Coast Survey, a specifically designed spill-free photographic tank was constructed and taken on board for the first time. It allowed photography of several dozens of invertebrate species, which had never been photographed alive before.

Other species that later proved to be new to science, had never been recorded. Such resulting photos, and the newly acquired information, will be incorporated into the first published version of the Field Guide to the Offshore Marine Invertebrates of South Africa, which is currently in preparation.

Figure 1. The specially-designed six-walled, spill-free photographic tank in the invertebrate laboratory aboard the Africana during the Winter South Coast Cruise, 2016 (here with a relatively well-known, but unusually large Striated hermit crab Dardanus arrosor)

A good understanding of the offshore invertebrate fauna that can one day benefit broad management strategies starts with correct species’ identifications. Publication of the much-anticipated field guide will significantly support ecosystem monitoring activities.

Poorly sampled deep-sea environment

Opposed to general public perception that our oceans are widely explored, we in fact know astoundingly little about the offshore invertebrates in South Africa. Griffiths et al. (2010) reported that 99% of invertebrate samples were collected shallower than 1 000 metres, emphasising just how poorly sampled South Africa's deep-sea environment is.

South Africa remains a relatively remote and exotic location for taxonomic experts mostly working in ‘first world’ research institutions. The unique biogeography of the region and the fact that South Africa's offshore habitats have rarely been studied for marine invertebrates are some of the many reasons why our oceans require more foundational taxonomic research.

International taxonomic experts are generally excited about invertebrate specimens from South Africa, highlighting the need for further such research, which is not only exciting and full of new discoveries, but also critical to answer larger research questions, both on a local and a global scale.

Below are some of the exciting species found during the 2016 surveys that are brand new discoveries to science. Some of these species are currently being described by South African experts with international taxonomic collaborators, where necessary.

Starfish

A new species of starfish was sampled during the 2016 September South Coast demersal survey. The appealing species measures about 7 cm in diameter and is a member of the family Goniasteridae. It is similar to the species Sphaeriodiscus sp. and might have previously been mistaken for a juvenile Toraster tuberculatus, another common offshore South African starfish species.

Figure 2. New species of seastar from the family Goniasteridae, currently being taxonomically described by Dr Chris Mah at the Smithsonian Institution (Washington D.C., USA)

Hermit crabs

Two hermit crab species, one new to science and one new species record for the country (with a remarkable range extension), are among the new discoveries. Each species represents a new record for their genera in South Africa.

The first species, Paragiopagurus atkinsonae, belongs to the ‘deepwater hermit crab’ family Parapaguridae. Some members of this hermit crab family can be extremely abundant in the deep-sea and have unusual living ‘homes’.

Most hermit crabs depend upon empty gastropod shells to protect the soft and vulnerable abdomen. However, many parapagurids form a symbiosis with an anthozoan anemone that grows a ‘pseudo-shell’, also known as a carcinoecium. By overcoming the problem of constantly finding a new home that has to be exchanged as the hermit crab grows, parapagurids can form large population densities even in the absence of larger gastropod shells.

As scavengers, parapagurids clean up the sea floor by feeding on leftovers from predators or dead material, like fish that have died, and also hunt for smaller invertebrates on their own. They themselves are an important food source for many species of fish.

Until recently, only two parapagurid hermit crabs were recognised in the bycatch of the trawls, namely Sympagurus dimorphus and Parapagurus bouvieri. Paragiopagurus atkinsonae is a third species, not uncommonly found in the trawls. It is superficially similar to S. dimorphus, and thus far has only been found in a small area of the West Coast, in a depth range of 199-277 metres. 

The second species of hermit crab discovered during the September 2016 survey, Goreopagurus poorei, is a new record for South Africa. This deep-sea hermit crab species was previously only recorded from Tasmania, about 5 400 nautical miles away.

In the September/October 2016 DAFF demersal research survey it was found along the edge of the Agulhas Shelf. Members of the genus (until now not recorded from Africa at all!) can be identified by the grossly unequal chelipeds (Figure 3, right), with the right one being very elongate and having a markedly produced carpus (third segment).

Figure 3. Two hermit crab discoveries from offshore deep waters of South Africa. Left: The ‘deep-water hermit crab’ Paragiopagurus atkinsonae from the West Coast is similar to the very common Sympagurus dimorphus. Right: Goreopagurus poorei from the shelf region on the South Coast is a new and unexpected record for South Africa, occurring at depths usually >500 m.

Symbiotic sponge

A new species of sponge was found in shallower waters (about 50 metres) on the South Coast that can be assigned to the genus Suberites, family Suberitidae. This species forms a mutualistic symbiosis with the Blue-faced pagurid hermit crab, Pagurus liochele.

The sponge builds the home for the hermit crab by extending on the aperture of the gastropod shell. This construction is revealed in a micro-computed tomography scan (microCT) that was carried out at the CT Scanning Facility at Stellenbosch University. In return for providing the shell-extension for the crab, the hermit carries the sponge around and prevents it from being washed away in the current or buried in the sand.

Figure 4. Blue-faced hermit crab Pagurus liochele in a new species of Suberites sponge, with which it forms a facultative mutualistic symbiosis. Left: Colour in life. Right: Computer-animated MicroCT scan highlighting the internal structure of the coiled cavity occupied by the hermit.

Commensal bivalve

A new small species of bivalve from the family Galeomatidae was found between the spines of the abundant Purple heart urchin, Spatangus capensis. The bivalve species can be assigned to the genus Montacuta, which is well documented in the North Atlantic and often lives commensally between the spines of sea urchins.

The specimens from South Africa are different and new to science, and are currently being described by Dr Paul Valentich-Scott from the Santa Barbara Museum of Natural History, USA.

Figure 5. A new species of galeommatid bivalve living commensally between the spines of the Purple heart urchin, Spatangus capensis. The bivalves use their foot to hold on to the spines, where they find protection from potential predators.

* Jannes Landschoff is a PhD student at the University of Cape Town and a co-author on the Arthropoda section of the SAEON-led Field Guide to the Offshore Marine Invertebrates of South Africa. Under the supervision of Emer. Prof. Charles L. Griffiths, he is studying the biodiversity of hermit crabs in South Africa, but also has a wide interest in the general biology of marine invertebrates.

Reference

Griffiths CL., Robinson, TB., Lange L. and Mead A. 2010. Marine Biodiversity in South Africa: An Evaluation of Current States of Knowledge. PlosONE 5(8):e12008. doi:10.1371/journal.pone.0012008.