Existing population studies of deep-sea amphipods have focused on species that inhabit deep-sea vent or trench environments but few cosmopolitan species have been studied. Here we provide new insight into the life history and population ecology of the pan-oceanic scavenging amphipod Paralicella caperesca and discuss the influence of nutrient-rich submarine canyon environments on the growth and reproduction of this species. Data were collected through the dissection and measurement of 2997 P. caperesca from 14 samples taken from abyssal plains, continental slopes and submarine canyons in the North-East Atlantic. Sexual dimorphism was less pronounced than observed for other scavenging amphipod species but females were significantly larger and had shorter antennae than males. The size of oostegites in female P. caperesca varied considerably within size classes, ovaries contained a relatively large number of oocytes, and no empty ovaries were observed. These factors, in combination with absence of mature females, suggest that P. caperesca practices semelparity, a reproductive strategy that complements the feeding strategy of this obligate necrophage. Five male and seven female size-grouped cohorts were identified for P. caperesca. Cohorts from deep-sea submarine canyon populations showed consistently larger mean total body lengths than non-canyon cohorts. Individuals from canyon samples also expressed sexual characteristics at smaller sizes than non-canyon individuals. We hypothesize that these trends are indicative of nutrient-mediated growth, maturation, and reproduction in P. caperesca. The species is able to grow and reproduce relatively quickly in response to increased nutrient input in canyon environments and therefore dominates scavenging amphipod assemblages.

The study presents Cladorhizidae collected during Ifremer cruises in the Atlantic Ocean from 1981 to 2004. Fifteen species are described from the genera Abyssocladia, Asbestopluma, Chondrocladia and Cladorhiza, with complete descriptions of five new species. While a couple of species were collected at 670–1010 m depth at the Rockall Bank, most species were collected at middle to lower bathyal and abyssal depths (~2000–5000 m), ranging from the northern Atlantic to the Mid-Atlantic Ridge and the coast of Africa at Gabon–Congo. A biogeographic analysis of currently known Arctic, Atlantic and some Antarctic species shows that the majority of included cladorhizids are described from the north-east Atlantic and Arctic Oceans while a lower number of species are known from other parts of the Atlantic Ocean. Large regions are poorly investigated, and previously undescribed species can be expected when sampling in these areas. A regional mostly endemic cladorhizid fauna is predicted for shelf and upper slope areas. Species in the lower bathyal and abyssal seem on the other hand to have a wider geographical distribution.

The poorly-known serpulid Nogrobs grimaldii was originally described based on specimens collected from off Azores at depths of 1846–1900 m. Its adults are characterized by thick pinnulated opercular peduncle and unusual free (unattached) quadrangular tube coiled into a flat spiral. Here we review and re-identify published material and report new records of this enigmatic deep-water serpulid.

Using a morphology-based approach, we explore the relationships between three poorly understood species of organic-walled Foraminifera. Thalmann and Bermudez (1954) described Chitinosiphon rufescens as the type species of a new monotypic genus which they compared to the tubular agglutinated foraminiferan Bathysiphon. Loeblich and Tappan (1964), however, considered C. rufescens to be identical to Reophax membranacea Brady 1879, type species of another organic-walled genus, Nodellum. Based on a re-examination of the type specimens of both species, new material of C. rufescens from the Lost City hydrothermal field, and new material of N. membranacea from the NE Atlantic and Pacific Oceans, we show that these two deep-sea species are distinguished by the following features. (1) Chitinosiphon rufescens lacks the distinct, regular constrictions that divide the tubular test of N. membranacea into a series of segments. (2) The proloculus is spindle-shaped in C. rufescens but sub-cylindrical in N. membranacea. (3) A distinctive, pocket-like invagination is developed at the base (proximal end) of the proloculus in N. membranacea but not in C. rufescens. However, a series of undescribed species which occur in deep-sea sediments blur the distinction between the two genera. We therefore adopt a conservative position and regard Chitinosiphon as a junior synonym of Nodellum. We also examined the holotype and new material of Nodellum moniliforme Resig, 1982, the type species of Resigella Loeblich and Tappan, 1984, in which the organic-walled test comprises a series of bulbous chambers. This species exhibits a basal invagination, identical to the feature present in Nodellum membranacea. These three remarkable species are united by the basically tubular test and the nature of the test wall which is largely organic, brownish in colour, and exhibits no internal structure when broken sections are examined by SEM. The surface of the organic test of Nodellum rufescens from Lost City is strewn with tiny (≤1 μm), needle-shaped mineral particles, visible only by SEM. More equidimensional, micron-sized particles are present in the other two species. We agree with Thalmann and Bermudez (1954) that N. rufescens is related to tubular agglutinated taxa such as Bathysiphon. Resigella may have similar affinities, although this needs to be tested using molecular approaches.