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The spatial distribution, density and reproductive ecology of Ainigmaptilon antarcticum was studied using samples (colonies) collected during the EASIZ (Ecology of the Antarctic Sea Ice Zone) cruises I, II, and III, (1996, 1998, and 2000). Samples were taken using Agassiz and bottom trawls between 150 and 600 m depth in conjunction with a Remotely Operated Vehicle (ROV, video recording transects). A. antarcticum showed a very patchy distribution with a mean density of 12 per 100 m 2 (SD ± 23) in the study area. This gorgonian species is gonochoric with a sex ratio of 1:1. Two size classes of oocytes in different developmental stages were observed in summer (January to March) and autumn (April to May), ranging from 25 to 700 µm in summer, and from 20 to 900 µm in autumn. Differences in developmental stages among different zones of the colony were observed. The apical and medial part showed the highest fecundity. The distribution of gonad size differed between summer and autumn. The relative frequency of the largest oocyte size class decreased in the autumn samples. No larvae were found. The results are discussed in the context of the relationship between reproductive strategies of marine invertebrates and environmental factors. KEY WORDS: Antarctic octocorals · Reproductive patterns · DistributionResale or republication not permitted without written consent of the publisher

Despite significant advances in invertebrate phylogenomics over the past decade, the higher-level phylogeny of Pycnogonida (sea spiders) remains elusive. Due to the inaccessibility of some small-bodied lineages, few phylogenetic studies have sampled all sea spider families. Previous efforts based on a handful of genes have yielded unstable tree topologies. Here, we inferred the relationships of 89 sea spider species using targeted capture of the mitochondrial genome, 56 conserved exons, 101 ultraconserved elements, and three nuclear ribosomal genes. We inferred molecular divergence times by integrating morphological data for fossil species to calibrate 15 nodes in the arthropod tree of life. This integration of data classes resolved the basal topology of sea spiders with high support. The enigmatic family Austrodecidae was resolved as the sister group to the remaining Pycnogonida and the small-bodied family Rhynchothoracidae as the sister group of the robust-bodied family Pycnogonidae. Molecular divergence time estimation recovered a basal divergence of crown group sea spiders in the Ordovician. Comparison of diversification dynamics with other marine invertebrate taxa that originated in the Paleozoic suggests that sea spiders and some crustacean groups exhibit resilience to mass extinction episodes, relative to mollusk and echinoderm lineages.

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The amphipod population associated with Bugula nerilina (L.), a very common bryozoan species in Algeciras Bay (Strait of Gibraltar), was studied on a spatio-temporal scale, in order to define its role as a bioindicator. Samples were collected in December, March, June and September along a transect running from the external to the internal sampling stations.Fifty-three species belonging to 22 families were identified; the most abundant species were Jmsa marrnorata HOLMES, Ischyrocerus inexpectatus (RUFFO) and Phtisica marina SLABBER.The spatial evolution of the amphipod community reflected the physico-chemical conditions of Algeciras Bay, yielding a clear gradient from the outer to the inner stations. The stations located at the mouth of the bay, characterised by high hydrodynamism and low sedimentation, had a higher diversity and species richness than the inner stations with low water movement and higher sedimentation. Eight species preferred for the outer stations, while another nine species were typical of the inner harbours.The most notable aspect of the seasonal evolution was the increased dominance of the tube-builder and deposit-suspension feeder Jassa marmorota.Structural and ordination analyses corroborate the outer-inner gradient in the bay and illustrate the importance of hydrodynamic forces and sedimentation in the amphipod community.

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