Annika Putz

Sex role preferences, gender conflict and sperm trading in simultaneous hermaphrodites: a new framework

A key issue in the study of the behaviour of copulating simultaneous hermaphrodites concerns the decision about which sexual role to adopt in a mating encounter. If two mates share a preference to adopt the same sexual role, mating interests are inherently incompatible. We review previous models that have explored the origin of, and resolutions to, such gender conflicts: (1) sex allocation models; (2) risk-averse models; (3) costly male function models; and (4) game-theoretical models. None of these satisfactorily accounts for the diversity found in hermaphrodite mating systems, either because the assumptions of the model reflect lifetime decisions rather than single mating decisions, or because only a narrow set of environmental conditions is considered. Furthermore, some often cited predictions such as a preference for copulating in the female role or a prevalence of conditional sperm exchange (‘sperm trading’) face limited empirical support. To reconcile and extend these previous ideas, we propose the gender ratio hypothesis as a more general model framework. Here, sex role preferences derive from the potential fitness gain per mating event. Preferences can thus vary considerably within and between individuals, but are predicted to be usually male biased. By combining sex role preference with mating rate, our hypothesis can explain the existence of a wide range of hermaphrodite mating systems, including unconditional reciprocity in systems where sperm trading has been predicted but not found.

Bioactive natural products from marine sponges and fungal endophytes

This review highlights recent findings of our group on bioactive marine natural products isolated from marine sponges and marine derived fungi. The activated chemical defence of the Mediterranean sponge Aplysina aerophoba is introduced as an example of a dynamic response of marine sponges to wounding. Following tissue disrupture preformed brominated isoxazoline alkaloids are enzymatically cleaved and thereby give rise to aeroplysinin-1 which is believed to protect sponges from invasion of pathogenic bacteria. A preliminary characterization of the membrane bound enzyme(s) involved in the cleavage reaction is presented. Bromotyrosine derived, oxime group bearing peptides, the so called bastadins, obtained from the sponge Ianthella basta and some of their synthetic derivatives were shown to exhibit pronounced antifouling activity against larvae of the barnacle Balanus improvisus. The antifouling activity could be traced to the oxime group as an important pharmacophore that was also found to be present in other sponge derived natural products exhibiting antifouling activity. Marine derived fungi that reside within invertebrates such as sponges or inside Mangrove plants are emerging as a new source of bioactive metabolites as demonstrated for Aspergillus ustus and Alternaria sp. that were isolated from the sponge Suberites domuncula or from the Mangrove plant Sonneratia alba, respectively. The former fungus yielded new moderately cytotoxic sesquiterpenoids of the drimane type whereas the latter was found to produce polyketides such as alternariol that exhibited strong and selective inhibitory activity against several protein kinases, for instance Aurora A and B which are targets for anticancer chemotherapy.

Hermaphrodite sex role preferences : the role of partner body size, mating history and female fitness in the sea slug Chelidonura sandrana

Costs and benefits associated with matings and the effects of mating frequency on fitness commonly differ between the sexes. As a result, outcrossing simultaneous hermaphrodites may prefer to copulate in the more rewarding sex role, generating conflicts over sperm donation and sperm receipt between mates. Because recent sex role preference models remain controversial, we contrast here some of their assumptions and predictions in the sea slug Chelidonura sandrana. For this hermaphrodite with sperm storage and internal fertilisation, risk-averse models assume that fitness pay-offs are constantly higher in the female than in the male function in any single mating. Moreover, excluding mutual partner assessment, these models predict male mating behaviour to be independent of receiver traits. The competing gender ratio hypothesis assumes that relative fitness pay-offs, and thus the preferred mating roles, vary and may reverse between matings and predicts that ejaculation strategies co-vary with receiver quality. We found that field mating rates of C. sandrana substantially exceeded what is required to maintain female fertility and fecundity, indicating large variation in direct female benefits between matings. We further demonstrate that male copulation duration adaptively increased with partner body size (i.e. fecundity) but decreased with recent partner promiscuity. These findings are compatible with the gender ratio hypothesis but contradict risk-averse models.

Depth-Related Alkaloid Variation in Mediterranean Aplysina Sponges

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.

Hexa-, hepta- and nonaprenylhydroquinones isolated from marine sponges Sarcotragus muscarum and Ircinia fasciculata inhibit NF-k B signalling in H4IIE cells

Objectives Marine organisms have proven to be a rich source of potent pharmacologically active compounds. Three polyprenyl‐1,4‐hydroquinone derivates (hexaprenyl‐1,4‐hydroquinone, heptaprenyl‐1,4‐hydroquinone and nonaprenyl‐1,4‐hydroquinone) were isolated from the Zoobenthos‐inhabiting sponges Sarcotragus muscarum and Ircinia fasciculata from the Eastern Mediterranean Sea (phylum: Porifera; class: Demospongiae).

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

In the Mediterranean Sea, two species of the genus Aplysina Nardo, 1834 (Demospongiae, Verongida, Aplysinidae) co-occur, both described by Schmidt in 1862. The first one was named Aplysina aerophoba (formerly Verongia aerophoba) due to the change of its bright yellow pigment uranidine to dark blue when exposed to air. The second one was named Aplysina cavernicola (formerly Verongia cavernicola) due to its preferred shaded habitats, e.g., caves. The definition for species differentiation was mainly based on ecological and morphological characteristics. However, as both species display a high degree of phenotypic variability, distinction solely based on morphological attributes is not suitable in all cases. In addition, differences can be found in the species-specific microbial composition of symbionts and metabolite pattern. For the first time, we report an investigation on both Aplysina species along one single transect on an underwater slope in the Adriatic Sea, and the successful species distinction using solely the different biochemical composition of metabolites.