It has been two decades since 1993 when research on the biology of rotifer aging was last reviewed by Enesco. Much has transpired during this time as rotifer biologists have adapted to the "omics" revolution and incorporated these techniques into the experimental analysis of rotifers. Rotifers are amenable to many of these approaches and getting adequate quantities of DNA, RNA, and protein from rotifers is not difficult. Analysis of rotifer genomes, transcriptomes, and proteomes is rapidly yielding candidate genes that likely regulate a variety of features of rotifer biology. Parallel developments in aging biology have recognized the limitations of standard animal models like worms and flies and that comparative aging research has essentially ignored a large fraction of animal phylogeny in the lophotrochozoans. As experimentally tractable members of this group, rotifers have attracted interest as models of aging. In this paper, I review advances over the past 20 years in the biology of aging in rotifers, with emphasis on the unique contributions of rotifer models for understanding aging. The majority of experimental work has manipulated rotifer diet and followed changes in survival and reproductive dynamics like mean lifespan, maximum lifespan, reproductive lifespan, and mortality rate doubling time. The main dietary manipulation has been some form of caloric restriction, withholding food for some period or feeding continuously at low levels. There have been comparative studies of several rotifer species, with some species responding to caloric restriction with life extension, but others not, at least under the tested food regimens. Other aspects of diet are less explored, like nutritional properties of different algae species and their capacity to extend rotifer lifespan. Several descriptive studies have reported many genes involved in rotifer aging by comparing gene expression in young and old individuals. Classes of genes up or down-regulated during aging have become prime targets for rotifer aging investigations. Alterations of gene expression by exposure to specific inhibitors or RNAi knockdown will probably yield valuable insights into the cellular mechanisms of rotifer life extension. I highlight major experimental contributions in each of these areas and indicate opportunities where I believe additional investigation is likely to be profitable.

Here we report one of the first investigations of evolvability of lifespan and reproduction in metazoans, examining both extrinsic and intrinsic factors. We tested effects on senescence of an environmental variable (simulated lake hydroperiod, the length of time an aquatic habitat is inundated), female reproductive physiology (asexual females that reproduce by ameiosis, versus sexual females reproducing by meiosis), and time in a benign culture environment (minimal, if any, external mortality factors). To do this we established chemostat cultures of the rotifer s.s., and maintained the cultures for 385 d. Hydroperiod alone or in interaction with the effects of time in the benign environment (season) or reproductive physiology had no significant effect on the net reproductive rate, generation time, or rate of aging. Yet combining animals from both ephemeral and permanent hydroperiods revealed a 26% increase in asexual female lifespan across seasons (23% decrease in the rate of aging) and a 56% increase in asexual fecundity, suggesting that maintenance in benign laboratory conditions leads to slower aging. The relative stasis of traits for sexual females implies an impact of reproductive physiology on evolvability. In addition we found a positive correlation between fecundity and lifespan, suggesting an absence of trade-offs in life history traits in the benign laboratory environment.

Klie, one of few non-marine species of the family Leptocytheridae (Ostracoda), is redescribed from specimens recently collected from the long-lived Lake Ohrid on the Albanian-Macedonian border. Detailed morphologies of valves and limbs of this species were compared with those of other Ohrid-Prespa leptocytherids, of some recent marine representatives of the genera Sars and Ruggieri from the Mediterranean, Irish and Baltic seas as well as with that of fossil non-marine species from the Miocene palaeo-Lake Pannon belonging to the genera Devoto and Stancheva. Comparison with other species of Leptocytheridae inhabiting fresh to brackish waters of the Black-Azov, Caspian and Aral seas were also carried out using descriptions provided in the literature. Based on the comparative morphological studies it is shown that and other Ohrid leptocytherids have a number of characters distinguishing them from other members of the genus but demonstrating a relationship with species of the genus . The most reliable of these characters are: a) anterior valve vestibulum from where mostly uni-ramified pore canals start, b) the entomodont hinge type with a strong anterior anti-slip tooth, a smooth posterior anti-slip bar on the left valve, and c) the hemipenis with underdeveloped lateral lobe and reduced clasping organ. From this strong evidence, the Ohrid leptocytherid species are allocated to the genus . Finally, a biogeographic scenario on the origin of the Ohrid leptocytherids is proposed which matches the "Lake Pannon derivate hypothesis". Close relationship of the Ohrid species with the non-marine leptocytherid taxa from the Neogene lakes of Central and Eastern Europe and with extant taxa from the Black and Caspian seas may indicate that the Ohrid derived from Lake Pannon species which were able to colonise lakes in Southern Europe through a stepping-stone process and subsequently to adapt to freshwater environment.

The distribution of Trichoptera of the Hozgarganta River (Los Alcornocales Natural Park, SW Spain) in relation with environmental factors was examined. Three groups of species were recognised according to the altitudinal gradient. In the headwaters the caddisflies and predominated; in the constrained section of the tributaries and sp. prevailed; finally, in the main channel and were the most important species. A direct ordination analysis (CCA) was used to describe assemblage changes among sites and corroborated that conductivity and temperature were the variables that best explained Trichoptera distribution. The temporal analysis showed changes in the Trichoptera diversity and richness in permanent stretches, as well as variations in the structure of the communities according to the season. We identified autumn-winter species ( and ) and summer ones ( sp, and ). In the basin we distinguished permanent, intermittent and ephemeral reaches with similar caddisfly richness and diversity, however the species composition associated with each one was different. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).