Assessment of serpulid-hydroid association through the Jurassic: A case study from the Polish Basin

The coexistence of sessile, tube-dwelling polychaetes (serpulids) and hydroids, has been investigated. Serpulid tubes bearing traces after hydroids are derived from different stratigraphic intervals spanning the Middle and Upper Jurassic, the rocks of which represent the diverse paleoenvironments of the Polish Basin. Although fossil colonial hydroids classified under the species Protulophila gestroi are a commonly occurring symbiont of these polychaetes during the Late Cretaceous and Cenozoic, they seem to be significantly less frequent during the Jurassic and limited to specific paleoenvironments. The hydroids described here are represented by traces after a thin stolonal network with elongated polyp chambers that open to the outer polychaete tube’s surface with small, more or less subcircular apertures. Small chimney-like bulges around openings are an effect of the incorporation of the organism by in vivo embedment (bioclaustration) within the outer layers of the calcareous tube of the serpulid host. Considering the rich collection of well-preserved serpulid tubes (>3000 specimens), the frequency of bioclaustrated hydroids is very low, with an infestation percentage of only 0.6% (20 cases). It has been noticed that only specimens of the genus Propomatoceros from the Upper Bajocian, Lower Bathonian, Middle Bathonian, and Callovian have been found infested. However, the majority of bioclaustrated hydroids (17 cases) have been recorded in the Middle Bathonian serpulid species Propomatoceros lumbricalis coming from a single sampled site. Representatives of other genera are not affected, which is congruent with previous reports indicating that Protulophila gestroi was strongly selective in the choice of its host. A presumably commensal relationship is compared with the recent symbiosis between the hydroids of the genus Proboscidactyla and certain genera of sabellid polychaetes.

The Nymph Architect of the Cicada Guyalna chlorogena: Behaviours and Ecosystem

At the beginning of the last year of its larval life, the nymph of Guyalna chlorogena builds, from a vertical well, which is the result of a verticalization process from a deep horizontal gallery, a clay turret 20 to 40 cm high which appears as a regulating device of the physico-chemical conditions inside the burrow. The construction of the turret is remarkable for its finish. The nymph maintains, repairs and rebuilds it if necessary. It opens and closes it under certain circumstances. Before moulting, the nymph comes out at the top, opening it according to a set protocol and time schedule, using its chitins’ forelegs. The burrow is associated in a commensal relationship with arborescent Fabaceae species (of the Tachigali genus) through its nutrition mode, the suction of the elaborated sap in fine roots, close to the meristems.

Rediscovery of the horseshoe shrimp Lightiella serendipita Jones, 1961 (Cephalocarida: Hutchinsoniellidae) in San Francisco Bay, California, USA, with a key to the worldwide species of Cephalocarida

Lightiella serendipita Jones, 1961 was first discovered in San Francisco Bay, California in 1953, but it had not been observed since 1988. In 2017, a total of 13 adult L. serendipita specimens were found as part of a study in central San Francisco Bay, nearly doubling the total number of specimens ever collected. We measured vertical distribution of macroinvertebrates and environmental variables, including grain size and chemical composition of sediment samples, to evaluate potential features associated with the habitat of the species. Specimens were generally found in sediments with low organic matter (1.7–3%), high sulfate concentrations (594.6–647 ppm SO4), fine grain size (12.8–36.2% sand, 35.6–58% silt, 22.8–37.6% clay) and were mostly found in deep core sections (4–10 cm). Specimens were also consistently observed in cores containing tube-forming Polychaeta (i.e., Sabaco elongatus (Verrill, 1873) and Capitellidae), suggesting L. serendipita may have a commensal relationship with sedentary polychaetes, as do other cephalocaridans such as Lightiella incisaGooding, 1963. We provide a scanning electron micrograph of L. serendipita and the first complete key to the species in class Cephalocarida to help elucidate the taxonomy of this rare crustacean taxon. The perceived absence of L. serendipita in previous surveys of the Bay may be attributable to its rarity; however, additional research is needed to fully understand habitat requirements and population size of this unique endemic species.

Impact of habitat loss on the diversity and structure of ecological networks between oxyurid nematodes and spur-thighed tortoises (Testudo graeca L.)

Habitat loss and fragmentation are recognized as affecting the nature of biotic interactions, although we still know little about such changes for reptilian herbivores and their hindgut nematodes, in which endosymbiont interactions could range from mutualistic to commensal and parasitic. We investigated the potential cost and benefit of endosymbiont interactions between the spur-thighed tortoise (Testudo graeca L.) and adult oxyurid nematodes (Pharyngodonidae order Oxyurida) in scrublands of southern Spain. For this, we assessed the association between richness and abundance of oxyurid species with tortoises’ growth rates and body traits (weight and carapace length) across levels of habitat loss (low, intermediate and high). Furthermore, by using an intrapopulation ecological network approach, we evaluated the structure and diversity of tortoise–oxyurid interactions by focusing on oxyurid species infesting individual tortoises with different body traits and growth rates across habitats. Overall, tortoise body traits were not related to oxyurid infestation across habitats. Oxyurid richness and abundance however, showed contrasting relationships with growth rates across levels of habitat loss. At low habitat loss, oxyurid infestation was positively associated with growth rates (suggesting a mutualistic oxyurid–tortoise relationship), but the association became negative at high habitat loss (suggesting a parasitic relationship). Furthermore, no relationship was observed when habitat loss was intermediate (suggesting a commensal relationship). The network analysis showed that the oxyurid community was not randomly assembled but significantly nested, revealing a structured pattern for all levels of habitat loss. The diversity of interactions was lowest at low habitat loss. The intermediate level, however, showed the greatest specialization, which indicates that individuals were infested by fewer oxyurids in this landscape, whereas at high habitat loss individuals were the most generalized hosts. Related to the latter, connectance was greatest at high habitat loss, reflecting a more uniform spread of interactions among oxyurid species. At an individual level, heavier and larger tortoises tended to show a greater number of oxyurid species interactions. We conclude that there is an association between habitat loss and the tortoise–oxyurid interaction. Although we cannot infer causality in their association, we hypothesize that such oxyurids could have negative, neutral and positive consequences for tortoise growth rates. Ecological network analysis can help in the understanding of the nature of such changes in tortoise–oxyurid interactions by showing how generalized or specialized such interactions are under different environmental conditions and how vulnerable endosymbiont interactions might be to further habitat loss.

Gut Microbial Changes, Interactions, and Their Implications on Human Lifecycle: An Ageing Perspective

Gut microbiota is established during birth and evolves with age, mostly maintaining the commensal relationship with the host. A growing body of clinical evidence suggests an intricate relationship between the gut microbiota and the immune system. With ageing, the gut microbiota develops significant imbalances in the major phyla such as the anaerobic Firmicutes and Bacteroidetes as well as a diverse range of facultative organisms, resulting in impaired immune responses. Antimicrobial therapy is commonly used for the treatment of infections; however, this may also result in the loss of normal gut flora. Advanced age, antibiotic use, underlying diseases, infections, hormonal differences, circadian rhythm, and malnutrition, either alone or in combination, contribute to the problem. This nonbeneficial gastrointestinal modulation may be reversed by judicious and controlled use of antibiotics and the appropriate use of prebiotics and probiotics. In certain persistent, recurrent settings, the option of faecal microbiota transplantation can be explored. The aim of the current review is to focus on the establishment and alteration of gut microbiota, with ageing. The review also discusses the potential role of gut microbiota in regulating the immune system, together with its function in healthy and diseased state.