Short-term patch dynamics of macroinvertebrate colonization on decaying reed detritus in a Mediterranean lagoon (Lake Alimini Grande,Apulia, SE Italy)

In aquatic ecosystems, the ecology of macrophytal detritus aggregations has been investigated over a range of temporal scales. Yet, no attempts have been made to minimize the temporal resolution of the analysis, thus neglecting the occurrence of short-term colonization and decay dynamics for these ephemeral patches of high biological activity. The present study was carried out at two sampling sites in Lake Alimini Grande, a brackish lagoon in South-East Italy. The abundance of macroinvertebrate taxa colonizing prepared packs of reed leaf detritus and the ash-free dry mass of the packs were monitored daily for 40 days. Spectral analysis was used to investigate the fine-scale temporal dynamics of invertebrates colonization and leaf pack mass variations. The macrobenthos found on leaf packs was dominated at both sites by few taxa (i.e., the vagile Lekanesphaera monodi, Microdeutopus gryllotalpa, Neanthes caudata and the sessile Balanus sp.), whose general colonization patterns were described by unimodal curves. At a daily temporal resolution Balanus sp. was characterized by random short-term density variations, while vagile taxa showed non-random, highly site- and species-specific fluctuations generally characterized by an oscillation period comprised between 2 and 3 days. In addition, leaf packs were characterized by non-random, short-term mass oscillations, coherent and in phase with L. monodi abundance fluctuations. Our results highlight the occurrence of short-term, non-random density variations of invertebrate colonizers on leaf detritus patches. In addition, they emphasize a previously unexplored, fine-scale linkage between abundance patterns of invertebrate consumers and short-term mass variations of decaying detritus.     

Inter-individual and within-brood variability in the fatty acid profiles of Norway lobster, <Emphasis Type="Italic">Nephrops norvegicus</Emphasis> (L.) embryos

The present study investigated the existence of inter-individual and within-brood variability in the fatty acid (FA) profile of developing embryos of Nephrops norvegicus. In all surveyed females (n = 5), the quantitatively most important FAs were as follows: 22:6n-3 (20.8 ± 3.9% average of total FA ± standard error), 18:1n-9 (19.5 ± 2.0%), 16:0 (15.2 ± 3.4%), 20:5n-3 (10.2 ± 1.4%), 16:1n-7 (8.9 ± 1.6%), and 18:1n-7 (5.7 ± 1.3%). Differences in FA profiles of embryos in the same clutch were assessed using brooding chamber side (left and right) and pleopod (1st and 2nd, 3rd and 4th, and 5th) as predictive factors. There were no significant differences in the FA composition of embryos sampled from both sides of the brooding chamber in 4 of the 5 surveyed females. However, all females exhibited significant differences in the FA profiles of embryos sampled from different pleopods. Both saturated FA (SFA) and highly unsaturated FA (HUFA) present in developing embryos exhibited marked differences along the breeding chamber. Overall, FA reserves appeared to vary significantly within broods, which can ultimately be reflected on early larval survival. A potential cause for the within-brood variation recorded in the FA profile of developing embryos include (1) differential female investment during ovarian maturation, mainly due to variation in food quality/availability; (2) differential lipid catabolism during the incubation period of developing embryos, as a consequence of embryos position within the female’s brooding chamber; or (3) differential female investment during ovarian maturation amplified by differential lipid catabolism during the incubation period.     

Co-evolution-driven cuticular hydrocarbon variation between the slave-making ant Rossomyrmex minuchae and its host Proformica longiseta (Hymenoptera: Formicidae)

Summary. Proformica longiseta exists as two populations in the Sierra Nevada Mountains in Spain, only one of which is parasitized by the slave-maker ant Rossomyrmex minuchae. To investigate the possible effect of co-evolutionary pressures on cuticular hydrocarbon (CHC) profiles (the presumed nestmate recognition cues), we performed a comparative analysis of the CHC of R. minuchae and P. longiseta colonies from both the allopatric and sympatric populations; the latter includes samples of enslaved as well as free-living workers. Discriminant analyses based on these chemical profiles showed two clear profile groups: the first comprised R. minuchae and both enslaved and free-living P. longiseta from the sympatric population; and the second the allopatric P. longiseta workers. As expected, the profiles of the two sympatric P. longiseta groups (enslaved and free-living) were distinct; but, interestingly, those of the enslaved P. longiseta and its parasite R. minuchae were also distinguishable. This indicates that despite their cohabitation each species maintains its own chemical identity. Profile similarity between the sympatric free-living P. longiseta and its parasite may explain the lower than expected aggression observed during raids. We further speculate that in view of the differences between the sympatric and allopatric population of P. longiseta, co-evolutionary pressures have driven changes in the profile of the former to better match that of its parasite R. minuchae. Such an adjustment may have enabled nests of the sympatric P. longiseta to endure multiple raids by the parasite (due to the reduced aggression) and thus to continue to reproduce despite the damage inflicted by the raids.     

Effects of the antimicrobial agent sulfamethazine on metolachlor persistence and sorption in soil

Recent monitoring investigations have shown that antimicrobial agents used in veterinary medicine can cause non-point source contamination of soils through manure spreading. In the present study, the effect of the antimicrobial agent sulfamethazine (sulfadimidine) on degradation and sorption of the herbicide metolachlor in a sandy loam soil was studied. In soil samples treated with sulfamethazine at two concentrations (15 and 150 microg kg(-1) soil), metolachlor persistence was not different than of that observed in untreated samples. These results were supported by the absence of effects of both sulfamethazine concentration levels on the size of the culturable soil bacteria population. Equilibrating soil samples with metolachlor solutions containing equivalent sulfamethazine concentrations did not lead to any significant effects on metolachlor sorption, suggesting that, under the conditions of the present experiment, sulfamethazine did not affect metolachlor bioavailability in soil. This laboratory investigation showed that concentrations of sulfamethazine in the microg kg(-1) range did not cause significant effects on metolachlor degradation and sorption thus not affecting the main processes ruling its environmental fate in soil.     

Parental diets determine the embryonic fatty acid profile of the tropical nudibranch Aeolidiella stephanieae: the effect of eating bleached anemones

Aeolidiella stephanieae is a stenophagous tropical nudibranch that feeds exclusively on glass anemones of the genus Aiptasia. These sea anemones usually harbour endosymbiotic photosynthetic dinoflagellates that contribute to the nutrition of their host by providing photosynthetates, such as fatty acids (FA). The present work determined the effect of parental diets on the FA profile of A. stephanieae embryos by feeding breeding pairs of this nudibranch with either symbiotic or aposymbiotic A. pallida. Contrasting FA profiles, namely in the levels of palmitic acid (16:0) and docosahexaenoic acid (DHA, 22:6n-3), were recorded for both parental diets and egg masses produced by nudibranchs eating either symbiotic or aposymbiotic A. pallida. Noteworthy effects of parental dietary FAs on egg masses were also observed, particularly for DHA, which is mainly synthetized by the endosymbionts of A. pallida. Additionally, the present study also highlights how bleaching events may promote cascading effects on the nutrition of marine species with a stenophagous diet, such as A. stephanieae.