Depth-Related Alkaloid Variation in Mediterranean Aplysina Sponges

Abstract

Total amounts and patterns of bromoisoxazoline alkaloids of Aplysina sponges from Croatia (Mediterranean Sea) were analyzed along an underwater slope ranging from 1.8 to 38.5 m. Total amounts of alkaloids varied from sample to sample and showed no correlation with depth. In contrast, striking differences of alkaloid patterns were found between sponges from shallow sites (1.8 - 11.8 m) and those collected from deeper sites (11.8 - 38.5 m). Sponges from shallow depths consistently exhibited alkaloid patterns typical for Aplysina aerophoba with aerophobin-2 (2) and isofistularin-3 (3) as main constituents. Sponges from deeper sites (below 11.8 m) resembled Aplysina cavernicola with aerothionin (4) and aplysinamisin- 1 (1) as major compounds. The typical A. cavernicola pigment 3,4-dihydroxyquinoline- 2-carboxylic acid (6), however, could not be detected in A. aerophoba sponges but was replaced by the A. aerophoba pigment uranidine (5) which appeared to be present in all sponge samples analyzed. During transplantation experiments sponges from sites below 30 m featuring the A. cavernicola chemotype of bromoisoxazoline alkaloids were translocated to shallower habitats (10 m). The alkaloid patterns in transplanted sponges were found to be stable over a period of 12 months and unaffected by this change in depth. In a further experiment, clones of Aplysina sponges from shallow depths of 5 - 6 m resembling the A. aerophoba chemotype were either kept in situ under natural light conditions or artificially shaded by excluding photosynthetically active radiation (PAR). Neither 4 nor 1 were detected in artificially shaded sponges over an observation period of 12 months. In summary, two chemically distinct types of Aplysina sponges were discovered in this study that proved to be remarkably stable with regard to the bromoisoxazoline patterns and unaffected either by changing the light conditions or depth. It is not clear presently whether the Aplysina sponges collected from depths < 11.8 m represent a new chemotype of A. cavernicola lacking the pigment 6 or whether we have incidentally come across a so far undescribed species of the genus Aplysina.

Spatial Variability in Secondary Metabolites of the Indo-Pacific Sponge Stylissa massa

“…Only hymenidin concentration was higher in deeper samples compared to shallow water sponges. Several previous studies found that secondary metabolite production did not vary significantly with depth in sponges (Becerro and Paul, 2004;Abdo et al, 2007;Putz et al, 2009). A transplantation experiment along a depth gradient with the sponge Aplysina cavernicola also revealed no changes in the metabolite profile in transplanted sponges (Thoms et al, 2003).…”

Exploring the Links between Natural Products and Bacterial Assemblages in the SpongeAplysina aerophoba

“…Aplysina individuals sampled thousands of kilometers apart showed indistinguishable secondary metabolite profiles (28). At a small spatial scale, bromoisoxazoline patterns of two Aplysina species proved to be remarkably stable and unaffected either by changing the light conditions or depth (54). Similarly, the alkaloid content remained unchanged after cultivation of Aplysina specimens in starvation conditions and antibiotics exposure in aquaria (35).…”

Depth profile of Aplysina ssp.: morphological, histological and biochemical aspects and their role in species distinction

“…Insufficient photosynthetically active radiation (PAR) limited the growth of phototrophic organisms (e.g. symbiotic cyanobacteria, algae) below 20 m depth (see Putz et al 2008: erasement of PAR in 15 m: 89%).…”

“…Parazoanthus axinellae and green, brown as well as red algae were also abundant. Due to the lightexposed status of the steep face (see Putz et al 2008), photophilic organisms, e.g. Codium bursa, Dictyota dichomota and Peyssonnelia squamaria could be detected down to 20 m depth (Fig.…”