Physiological strategies contributing to the coexistence of two predatory species of stoneflies: Dinocras cephalotes and Perla bipunctata.

Our study focuses on the oxidative state of two aquatic insects of the order Plecoptera belonging to the family Perlidae, namely Dinocras cephalotes (Curtis, 1827) and Perla bipunctata Pictet, 1833. These species are widely distributed throughout the Western Palearctic region and coexist in the stream where individuals for this study come from. We highlight the physiological strategies of these two different predator species of stoneflies, showing a higher accumulation of lipid reserves in P. bipunctata, higher glucose levels in the body tissues of D. cephalotes and a higher capacity of the antioxidant enzymes in P. bipunctata, what provides it a protection against oxidation of lipids, which are greater in this species. This leads to a similar oxidative state in both species. Based on these results is discussed how two close related species developing a very similar ecological role in the same habitat can achieve a similar fitness with differences in their physiological strategies.

Relationship between brain and liver oxidative state and maximum lifespan potential of different fish species.

The aim of the present study is to determine whether a relationship exists between the maximum lifespan potential (MLSP) of different fish species (Squalius pyrenaicus, Cyprinus carpio, Carassius auratus, Luciobarbus sclateri and Oncorhynchus mykiss) and the oxidative state of brain and liver. For this purpose, the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase, glutathione peroxidase (GPX), glutathione reductase (GR), glutathione S-transferase (GST) and DT-diaphorase (NAD(P)H:quinone oxidoreductase1) were measured together with the lipid peroxidation degree (malondialdehyde, MDA) in liver and brain tissues of the collected species. Only the brain tissue manifested a higher activity of the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and glutathione S-transferase in addition to a negative correlation between the values of MDA and MLSP among the different fish species. Hypotheses are proposed from the analysis of the obtained results that open new areas of research and converge on the importance of the theory of free radicals in the processes that condition the maximum life expectancy of an animal species.

Digestive enzyme activity and trophic behavior in two predator aquatic insects (Plecoptera, Perlidae): a comparative study.

Plecoptera (Perlidae) are among the major macroinvertebrate predators in stream ecosystems and one of the insect families with lower tolerance to environmental alterations, being usually employed as bioindicators of high water ecological quality. The differences in the trophic roles of the coexisting species have been exclusively studied from their gut contents, while no data are available on the comparative digestive capacity. In the present paper, we make a comparative study of the activity of several digestive enzymes, namely proteases (at different pH), amylase, lipase, trypsin and chymotrypsin, in two species of stoneflies, Perla bipunctata and Dinocras cephalotes, which cohabit in the same stream. The study of digestive enzyme activity together with the analysis of gut contents can contribute to a better understanding of the ecology of these aquatic insects and their role in freshwater food webs. Thus, our results show that the two studied predator species inhabiting in the same stream present specializations on their feeding behaviors, facilitating their coexistence, and also differences in their capacity of use the resources. One of the main findings of this study is that D. cephalotes is able to assimilate a wider trophic resource spectrum and this could be one of the reasons why this species has a wider global distribution in all its geographical range.

Do artificial structures cause shifts in epifaunal communities and trophic guilds across different spatial scales?

In the current frame of proliferation of artificial structures in the sea, the ecological effects of artificial substrates on marine environments and their associate biota become a topic of great scientific and conservationist interest. This study was focused on the amphipod communities from western Mediterranean Sea and tested, using the same secondary substrate, Ellisolandia elongata, if the community and trophic structure differ between artificial (two concrete-based: cubes and tetrapods, and one natural rock-based: rip-raps) and natural substrates. Results usually showed lower taxa number and diversity in artificial substrates, as well as differences in composition and trophic structure of the amphipod community. However, patterns were not consistent for all localities, evidencing the importance of local scale. Other potential factors, besides the substrate type, should be considered to understand particularities of each locality in management and conservation strategies.

The drumming of Isoperla pallida Aubert and Guadalgenus franzi (Aubert) (Plecoptera, Perlodidae), and review and evolutionary considerations of Southern Iberian Peninsula Perlodidae.

The drumming calls of two perlodid species from Southern Spain (Sierra Morena, Jaén) are analyzed and described. Nineteen calls from one male of Guadalgenus franzi were recorded, showing a simple call pattern composed of two beats with an average duration between them of 184.32 msec (range: 165-227). This is the simplest call pattern yet discovered in the Plecoptera. The female of this species also presented a simple call consisting of only one beat. The male of Isoperla pallida showed an ancestral call pattern, more simple than the other Iberian Isoperla species (I. grammatica, I. nevada or I. curtata, all of them with multiphasic drumming calls or I. bipartita with a notably different model consisting of rubbing). Calls from six different males (the female did not drum) consisted of an average of 65.94 beats (range: 25-83) with a duration average of 1462.69 msec (range: 548-1835), regularly repeated with intervals with a duration average of 22.27 msec (range: 17-30). With this study, the vibrational calls of all the Perlodid species from the Southern Iberian Peninsula, except Perlodes microcephalus and Besdolus bicolor, are known. Moreover, it presents the first record and description of the call of the monospecific genus Guadalgenus. An evolutionary approach to the vibrational communication diversification in the perlodids of the Southern Iberian Peninsula is presented, showing a complexity graduation from the more simple drumming calls (shown by Hemimelaena flaviventris and G. franzi) to the rubbing call of I. bipartita and intermediate drumming calls of other Isoperla species, consistent with the drumming evolution paradigm of Stewart (2001).

Comparative spermatology in Plecoptera (Insecta). II. An ultrastructural investigation on four species of Systellognatha.

Sperm structure of four Systellognatha species, Dinocras cephalotes (Curtis, 1827) and Perla grandis (Rambur, 1841), family Perlidae, Siphonoperla torrentium (Pictet, 1841), family Chloroperlidae, and Isoperla grammatica (Poda, 1761), family Perlodidae, was investigated by light microscopy, scanning and transmission electron microscopy, and immunofluorescence microscopy. The spermatozoa of all the species are filiform and flagellate; they have an elongated compact nucleus, topped by either a bi-layered or three-layered acrosomal complex, and a '9+9+2' axoneme flanked by two mitochondrial derivatives. However, some variations have been observed, particularly regarding the morphology of the acrosomal complex, the shape of the nucleus, two more or less evident accessory bodies flanking the axoneme and the degree of crystallisation of the mitochondrial derivatives. Our results support the suggestion that Systellognatha is a monophyletic group, showing a single sperm pattern. Chloroperlidae and Perlodidae retain the plesiomorphic condition of some sperm characters while Perlidae show some autoapomorphies. A phylogenetic affinity between Plecoptera and the other orders of Polyneoptera has been confirmed.