Macroscopic characteristics facilitate identification of common Antarctic glass sponges (Porifera, Hexactinellida, Rossellidae)

Abstract

Glass sponges (Porifera, Hexactinellida) are conspicuous habitat-forming members of many Antarctic shelf communities. Despite their ecological importance, in-situ species identification remains problematic as it is traditionally based on microscopic analysis of spicules. External morphological features, in contrast, have largely been disregarded, so that different species have been mislabeled or lumped together when their identification was based on image material. In this paper, we provide a straight-forward guideline for in-situ identification of the most common rossellid sponges of the Antarctic shelf based on macroscopic characteristics. To determine diagnostic macroscopic characteristics of Anoxycalyx (Scolymastra) joubini and eight Rossella species, we combined examination of trawl-collected specimens, previous species descriptions and in-situ image material from the eastern Weddell Sea. Our study revealed that the smooth-walled species A. joubini, R. nuda and R. vanhoeffeni, previously often mixed up, can be distinguished by the form of their basal spicule tuft, their surface structure and their overall body form. The previously synonymized species R. racovitzae and R. podagrosa can be distinguished by their markedly different habitus. Based on our results, the so-called 'R. racovitzae budding type' in fact refers to R. podagrosa which occurs regularly in the eastern Weddell Sea. The species R. villosa, R. levis, R. fibulata and R. antarctica can be distinguished by the appearance of their conules, protruding spicules and overall body form. We conclude that macroscopic characteristics are helpful means for identification of Antarctic rossellid sponge species. This approach enables species-specific quantitative studies of Antarctic glass sponge grounds based on increasingly used non-invasive imaging technology.

Parental care and reproductive strategies in notothenioid fishes

“…Most data have been collected in the field using remotely operated vehicles (ROV), in situ observations for coastal and intertidal species or from experiments in aquaria, which documented two main pre‐spawning behaviours: nest building or eggs laying in sponges. Among the Nototheniidae, most species lay eggs inside the spongocoel of large hexactinellid glass sponges (e.g., Rosella nuda ), which are conspicuous in providing habitat structure in many Antarctic shelf communities (e.g., Federwisch et al., 2020). Single batches of 500–600 translucent white eggs 2.0 mm in diameter were found in the spongocoel of R. nuda and identified as those of painted notothen ( Nototheniops larseni , Nototheniidae; Konecki & Targett, 1989).…”

First observations of Weddell seals foraging in sponges in Erebus Bay, Antarctica

“…J. Rotella and R. Garrott (see further information under "Funding" below). The sponges investigated by the seals were identified from the videos based on their visible morphological characteristics as described by Federwisch et al (2020).…”