ALBERT

Description: Recent episodes of mass mortalities in the Mediterranean Sea have been reported for the closely related marine sponges Ircinia fasciculata and I. variabilis, which live in sympatry. In this context, the assessment of the genetic diversity, bottlenecks and connectivity of these sponges has become urgent in order to evaluate the potential effects of mass mortalities on their latitudinal range. Our study aims to establish 1.) the genetic structure, connectivity, and signs of bottlenecks across the populations of I. fasciculata, and 2.) the hybridization levels between I. fasciculata and I. variabilis. To accomplish the first objective, 194 individuals of I. fasciculata from 12 locations across the Mediterranean were genotyped at 14 microsatellite loci. For the second objective, mitochondrial cytochrome c oxidase subunit I sequences of 16 individuals from both species were analyzed along with genotypes at 12 microsatellite loci of 40 individuals coexisting in 3 Mediterranean populations. We detected strong genetic structure along the Mediterranean for I. fasciculata, with high levels of inbreeding in all locations and bottleneck signs in most locations. Oceanographic barriers like the Almeria-Oran front, North-Balearic front, and the Ligurian-Thyrrenian barrier seem to be impeding gene flow for I. fasciculata, adding population divergence to the pattern of isolation by distance derived from the low dispersal abilities of sponge larvae. Hybridization between both species occurred in some populations, which might be increasing genetic diversity and somewhat palliating the genetic loss caused by population decimation in I. fasciculata

Description: We aimed to investigate the cellular and chemical response of the chemically defended sponge Aplysina aerophoba (Phylum Porifera: Class Demospongiae) to grazing by its specialist Tylodina perversa (Phylum Mollusca: Class Opistobranchia). Three treatments were applied: control, grazing, and mechanical damage. Samples were collected 3 hours, 1 day, 3 days, and 6 days after treatment. The behavior of sea slugs after directly contact with sponge specimen was recorded by using a GoPro Hero 4 camera with the program time lapse (1 picture every 5 sec) for 1.5 to 2 hours. Our results showed that spherulous cells were recruited to the wounded site in a time-dependent manner. MALDI-imaging MS showed that both brominated compounds (aerophobin-2 and aeroplysinin-1) localized usually at the sponge surface and accumulated at the damaged surface upon wounding. As spherulous cells are common in many members of the class Demospongiae, the recruitment of defensive cells may also occur in other sponges for protecting these filter-feeders. Our study contributes to understanding the evolutionary mechanisms in sponges for facing grazing and wounding.

Description: Individuals of the breadcrumb sponge Halichondria panicea were collected from the field to perform phagocytic experiments. Collection site: coast of Schilksee (54.424278 N, 10.175794 E; Kiel, Germany) on August 7th 2022 at 8 am. Sponges were collected by carefully detaching them from crevices at 1-3 m depth by snorkeling. Name of the laboratory: H. panicea individuals were transported to the KIMMOCC climate chamber facilities at GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany), where they were kept for two weeks under controlled temperature (room: 10°C; water: 17°C), and with water supplied from the Kiel Fjord. Culture conditions during the experiment: The phagocytic experiments started on Aug 15th 2022, and were performed in the aforementioned facilities of GEOMAR. All the experiments lasted for one week. The experiments consisted on incubating whole sponge individuals in natural seawater for 30 min with green microalgae (Nannochloropsis sp.; live culture purchased from BlueBio Tech (Germany)), live TAMRA-stained bacteria (isolate PP-XX7 ; 16S rRNA gene sequence similarity of 98.6 % with Vibrio sp. NBRC 101805 and 97.0% to Vibrio variabilis R-40492T),) or 1 µm fluorescent latex beads (Fluoresbrite YG microsphere, Cat. 17154-10, Polyscience). Water samples were taken at time intervals through the incubation period to estimate particle uptake (i.e., filtration) by the sponge using flow cytometry. Fluorescence-activated cell sorting (FACS) of sponge cells extracted from H. panciea tissue from the individuals used during the phagocytic experiment was used to quantify phagocytic activity (i.e., the population of sponge cells with internalized particles). Particle uptake of H. panicea individuals used during the phagocytic assays. Sponges were incubated for 30 min with three Nannochloropsis sp., TAMRA-stained bacteria (Vibrio sp.), or fluorescent latex beads (1 µm). Differenet algal concentration and chase periods were tested. Water samples for flow cytometry were taken at time intervals. Controls: seawater incubations. A linear or exponential model (seawater and sponge, respectively) was used to calculate the particle concentration at the start (C0) and at the end (C30) of the incubation. Particle uptake (C0-C30) was corrected based on the seawater control incubations. y = particle concentration; x = time; R2 = goodness of fit.

Description: Individuals of the breadcrumb sponge Halichondria panicea were collected from the field to perform phagocytic experiments. Collection site: coast of Schilksee (54.424278 N, 10.175794 E; Kiel, Germany) on August 7th 2022 at 8 am. Sponges were collected by carefully detaching them from crevices at 1-3 m depth by snorkeling. Name of the laboratory: H. panicea individuals were transported to the KIMMOCC climate chamber facilities at GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany), where they were kept for two weeks under controlled temperature (room: 10°C; water: 17°C), and with water supplied from the Kiel Fjord. Culture conditions during the experiment: The phagocytic experiments started on Aug 15th 2022, and were performed in the aforementioned facilities of GEOMAR. All the experiments lasted for one week. The experiments consisted on incubating whole sponge individuals in natural seawater for 30 min with green microalgae (Nannochloropsis sp.; live culture purchased from BlueBio Tech (Germany)), live TAMRA-stained bacteria (isolate PP-XX7 ; 16S rRNA gene sequence similarity of 98.6 % with Vibrio sp. NBRC 101805 and 97.0% to Vibrio variabilis R-40492T),) or 1 µm fluorescent latex beads (Fluoresbrite YG microsphere, Cat. 17154-10, Polyscience). Water samples were taken at time intervals through the incubation period to estimate particle uptake (i.e., filtration) by the sponge using flow cytometry. Fluorescence-activated cell sorting (FACS) of sponge cells extracted from H. panciea tissue from the individuals used during the phagocytic experiment was used to quantify phagocytic activity (i.e., the population of sponge cells with internalized particles). FACS quantification of phagocytic sponge cells of H. panicea individuals used during the phagocytic assays. Sponges were incubated for 30 min with three Nannochloropsis sp., TAMRA-stained bacteria (Vibrio sp.), or fluorescent latex beads (1 µm). Differenet algal concentration and chase periods were tested. The sponge (host) cell suspension from each individual was run in the FACS three times (i.e., 3 technical replicates). The average number of events of the replicates is presented. Controls: individuals incubated without particle to correct for natural fluorescence in sponge cells. Bulk sponge cells: total DAPI-stained cell fraction; Non-phagocytic cells: cells without incorporated particle; Phagocytic cells: cells with incorporated particle.

Description: Individuals of the breadcrumb sponge Halichondria panicea were collected from the field to perform phagocytic experiments. Collection site: coast of Schilksee (54.424278 N, 10.175794 E; Kiel, Germany) on August 7th 2022 at 8 am. Sponges were collected by carefully detaching them from crevices at 1-3 m depth by snorkeling. Name of the laboratory: H. panicea individuals were transported to the KIMMOCC climate chamber facilities at GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany), where they were kept for two weeks under controlled temperature (room: 10°C; water: 17°C), and with water supplied from the Kiel Fjord. Culture conditions during the experiment: The phagocytic experiments started on Aug 15th 2022, and were performed in the aforementioned facilities of GEOMAR. All the experiments lasted for one week. The experiments consisted on incubating whole sponge individuals in natural seawater for 30 min with green microalgae (Nannochloropsis sp.; live culture purchased from BlueBio Tech (Germany)), live TAMRA-stained bacteria (isolate PP-XX7 ; 16S rRNA gene sequence similarity of 98.6 % with Vibrio sp. NBRC 101805 and 97.0% to Vibrio variabilis R-40492T),) or 1 µm fluorescent latex beads (Fluoresbrite YG microsphere, Cat. 17154-10, Polyscience). Water samples were taken at time intervals through the incubation period to estimate particle uptake (i.e., filtration) by the sponge using flow cytometry. Fluorescence-activated cell sorting (FACS) of sponge cells extracted from H. panciea tissue from the individuals used during the phagocytic experiment was used to quantify phagocytic activity (i.e., the population of sponge cells with internalized particles).