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Photo: UHH/CeNak, Martin Schwentner

Crustacea

Systematics, evolution, ecology, biogeography of Peracarida (Crustacea, Malacostraca) and Polychaeta of the deep sea

The deep sea appears to us as a uniform, coherent habitat. But is this habitat also so uniform for the organisms living there? To what extent do mountains, deep-sea trenches or other structures represent obstacles? The deep sea is the lightless area of our oceans from about 200 m depth. The deep sea can be divided into three areas: Bathyal, Abyssal and Hadal. The bathyal extends over a depth of about 200-3,000 m and describes the area of the sloping continental slope. The bathyal merges into the abyssal (approx. 3,000-6,000 m), which is generally described as a largely homogeneous habitat with soft substrate. The hadal (ca. 6,000-12,000 m) refers to deep-sea trenches that break up the abyssal.

Since the abyssal is generally perceived as a coherent ecosystem, we are particularly interested in the (dispersal) boundaries in this ecosystem. In order to investigate these boundaries, we look at different animal groups. The polychaetes (bristle worms), for example, are found in all marine habitats. From shallow water to the deep sea, they exhibit a great diversity of lifestyles, reproductive mechanisms and developmental stages. This diversity makes polychaetes a very interesting group for studies regarding dispersal (biogeography) and diversity (biodiversity). Another part of the research focuses on peracarid crustaceans. The best-known representatives of this superorder are, for example, the isopods (isopods) and amphipods (amphipods). In contrast to many other crustaceans and polychaetes, this group does not have a swimming larval stage and the young are released into the environment almost fully developed by the mother. Thus, crustaceans of this group have the same ability or inability to disperse throughout their lives. Especially isopods have developed a variety of forms and survival strategies to adapt to their habitat. There are purely burrowing representatives that live in the sediment, but there are also families that have adapted to swimming locomotion.

In the abyssal deep sea, clear barriers appear in the form of land masses, deep-sea mountains, deep-sea trenches or deep-sea mountains. The Vema-TRANSIT expedition gave us the opportunity to study one of the largest barriers in the Atlantic abyssal deep sea: the Mid-Atlantic Ridge. During the Vema-TRANSIT expedition (December 2014 to January 2015), one of the largest fracture zones ("Vema-Fracture Zone") of the Mid-Atlantic Ridge was investigated. This involved sampling the abyssal deep-sea plains (approx. 4000-5000m depth) to the west and east of the fracture zone, as well as in the fracture zone itself, using special towed equipment. The collected animals should provide insights into the biodiversity of this area, as well as information about a potential barrier effect of the Mid-Atlantic Ridge. Furthermore, samples were taken from the hadal (>8000m depth) Puerto Rico Trench to investigate a potential isolation due to the large depth differences.



Polynoid (Polychaeta) from the Hadal. Photo: UHH/CeNak, Martin Schwentner


An important prerequisite in determining the biodiversity and biogeography of organisms in the deep sea is the identification of species (taxonomy). On the basis of many morphological characteristics, such as head shape, body shape and appendages play a decisive role. Among the polychaetes and peracarids of the Vema Transit expedition, mostly unknown species were found. A purely taxonomic determination of species from the deep sea is usually very difficult, as the animals are often damaged and or incomplete due to sampling. In addition, molecular genetic studies are carried out to differentiate species. Here, a much higher number of species was found than was assumed on the basis of pure taxonomy. Furthermore, the genetic data also provide information on the relationships and distribution of the animals.

Haploytic network of Laonice sp. (Polychaeta) shows that identical haploytic pens occur both west (red tones) and east (blue tones) of the Mid-Atlantic Ridge. This indicates that the Mid-Atlantic Ridge is not a dispersal barrier.

The studies on the polychaetes of the "Vema Fracture Zone" are not yet complete, but it has been established on the basis of selected groups that there is a clear exchange of species between the eastern and western parts of the Atlantic, which makes the barrier effect of the Mid-Atlantic Ridge on these groups unlikely. This is only partly true for isopods, we could prove that swimming species are not affected but the majority of non-swimming isopods were only found east or west of the Mid-Atlantic Ridge. A planktonic larval stage, but also the ability to swim seem to favour dispersal in the abyssal deep sea regardless of physical barriers. Conversely, we conclude that the abyssal deep sea is by no means a barrier-free habitat for purely benthic organisms.

The projects on diversity, taxonomy and phylogeography of the deep sea take place in very close cooperation with Prof. Angelika Brandt (Senckenberg Research Institute and Natural History Museum Frankfurt) and the staff of the German Centre for Marine Biology (DZMB).

Selected publications:

  • Guggolz, T., Lins, L., Meißner, K., & Brandt, A. (in press). Biodiversity and distribution of polynoid and spionid polychaetes (Annelida) in the Vema Fracture Zone, tropical North Atlantic. Deep Sea Research Part II: Topical Studies in Oceanography.

  • Bober, S., Brix, S., Riehl, T., Schwentner, M. and Brandt, A. (under Review): Does the Mid-Atlantic Ridge affect the distribution of abyssal benthic crustaceans across the Atlantic Ocean? Deep Sea Research Part II: Topical Studies in Oceanography

Lectures and posters:

  • Bober, S., Riehl, T., Brix, S., Frutos,I.,Malyutina, M. and Brandt, A. (2015): Does the Mid Atlantic Ridge affect the distribution of benthic crustaceans across the Atlantic Ocean? A morphological and genetical approach on Macrostylidae (Crustacea, Isopoda).. 14th Deep-Sea Biology Symposium. Aveiro, Portugal, Vortrag.

  • Bober, S., Riehl, T., Brix, S., Frutos,I.,Malyutina, M. and Brandt, A. (2016): Does the Mid Atlantic Ridge affect the distribution of benthic crustaceans across the Atlantic Ocean. GfBS Annual meeting 2016 München, Vortrag.

  • Guggolz, T. & Brandt, A. (2015): Hadal Polychaeta (Annelida) of the Puerto Rico Trench. 14th Deep-Sea Biology Symposium. Aveiro, Portugal, Vortrag.

  • Guggolz, T., Lins, L., Meißner, K. & Brandt, A. (2016): The Vema Fracture Zone – A bridge through the Middle Atlantic Ridge? 12th International Polychaete Conference. Wales, Cardiff, Vortrag.