Antibiotics accelerate growth at the expense of immunity

Antibiotics have long been used in the raising of animals for agricultural, industrial or laboratory use. The use of subtherapeutic doses in diets of terrestrial and aquatic animals to promote growth is common and highly debated. Despite their vast application in animal husbandry, knowledge about the mechanisms behind growth promotion is minimal, particularly at the molecular level. Evidence from evolutionary research shows that immunocompetence is resource-limited, and hence expected to trade off with other resource-demanding processes, such as growth. Here, we ask if accelerated growth caused by antibiotics can be explained by genome-wide trade-offs between growth and costly immunocompetence. We explored this idea by injecting broad-spectrum antibiotics into wood tiger moth ( Arctia plantaginis ) larvae during development. We follow several life-history traits and analyse gene expression (RNA-seq) and bacterial (r16S) profiles. Moths treated with antibiotics show a substantial depletion of bacterial taxa, faster growth rate, a significant downregulation of genes involved in immunity and significant upregulation of growth-related genes. These results suggest that the presence of antibiotics may aid in up-keeping the immune system. Hence, by reducing the resource load of this costly process, bodily resources may be reallocated to other key processes such as growth.

Predator-Induced Plasticity on Warning Signal and Larval Life-History Traits of the Aposematic Wood Tiger Moth, Arctia plantaginis

Predator-induced plasticity in life-history and antipredator traits during the larval period has been extensively studied in organisms with complex life-histories. However, it is unclear whether different levels of predation could induce warning signals in aposematic organisms. Here, we investigated whether predator-simulated handling affects warning coloration and life-history traits in the aposematic wood tiger moth larva, Arctia plantaginis. As juveniles, a larger orange patch on an otherwise black body signifies a more efficient warning signal against predators but this comes at the costs of conspicuousness and thermoregulation. Given this, one would expect that an increase in predation risk would induce flexible expression of the orange patch. Prior research in this system points to plastic effects being important as a response to environmental changes for life history traits, but we had yet to assess whether this was the case for predation risk, a key driver of this species evolution. Using a full-sib rearing design, in which individuals were reared in the presence and absence of a non-lethal simulated bird attack, we evaluated flexible responses of warning signal size (number of orange segments), growth, molting events, and development time in wood tiger moths. All measured traits except development time showed a significant response to predation. Larvae from the predation treatment developed a more melanized warning signal (smaller orange patch), reached a smaller body size, and molted more often. Our results suggest plasticity is indeed important in aposematic organisms, but in this case may be complicated by the trade-off between costly pigmentation and other life-history traits.

Malagasy Polka Dot Moths (Noctuoidea: Erebidae: Arctiinae: Syntomini) of Ambohitantely—endemism in the most important relict of Central Plateau rainforest in Madagascar

Malagasy Syntomini (Polka Dot Moths) are one of the largest endemic lineages of Lepidoptera on the island, belonging to the Tiger Moth subfamily (Arctiinae). This diverse radiation comprises nearly 100 valid described species that share a single ancestor. Despite a monograph in 1964 by Paul Griveaud, systematics of the group greatly needs modern revision, and their distribution on the island is still poorly known. This contribution concerns the diversity of Syntomini of the Réserve Spéciale d’Ambohitantely, which protects the largest remaining, but already highly fragmented, vestige of Central Plateau rainforest in Madagascar. Here we provide an annotated checklist of the eight species occurring in the Reserve. Two species are recorded from the forest for the first time, while five endemics are until now known only from Ambohitantely. We also describe for the first time the female of Thyrosticta vestigii Griveaud, 1964 and of Maculonaclia tampoketsya Griveaud, 1969, as well as a yellow morphotype of Thyrosticta dilata Griveaud, 1964, and we redescribe and illustrate the genitalia of the remaining species. The significance of such colour pattern variation in aposematic moths and the role of this Reserve as a local centre of diversity of Malagasy Syntomini together with its importance in the protection of the biodiversity of Madagascar are discussed.

Male of Spilarctia mikeli Bolotov, Kondakov & Spitsyn, 2018, an endemic species from Flores Island, Lesser Sunda Archipelago (Lepidoptera: Erebidae: Arctiinae)

The Lepidoptera fauna of the island of Flores (Lesser Sunda Archipelago, Indonesia) shares a large proportion of endemic species, which may reach 80–100% in several groups (Zolotuhin & Witt 2005; Nässig et al. 2009; Zolotuhin 2009; Nässig & Bouyer 2010; Yakovlev 2015; Spitsyn & Potapov 2020; Spitsyn & Bolotov 2020). A plethora of new species was described from this island during the last 15 years, e.g. the tiger moth Spilarctia mikeli Bolotov, Kondakov & Spitsyn, 2018 (Zolotuhin & Witt 2005; Yakovlev 2006; Spitsyn & Bolotov 2020a, b, c). This species was described based on a single female specimen collected in West Flores (Bolotov et al. 2018). In the present paper, we describe the male of Spilarctia mikeli for the first time, and illustrate variability of marking patterns of both the male and the female of this species.

Life history of the rare boreal tiger moth Arctia menetriesii (Eversmann, 1846) (Lepidoptera, Erebidae, Arctiinae) in the Russian Far East

A thorough description and detailed photographs of all developmental stages of one of the rarest Palaearctic moths, Menetries’ tiger moth Arctia menetriesii (Eversmann, 1846) (Lepidoptera, Erebidae, Arctiinae), are presented. Eggs were obtained from a female collected in the Bureinsky Nature Reserve, Khabarovsk Krai, Russia. Data relating to specimens from this region significantly supplements previously published data, which was derived exclusively from more westerly parts of the species’ range. Larvae were reared mainly on dandelion (Taraxacum campylodes G.E.Haglund) in laboratory conditions. Some larvae were fed on Aconitum consanguineum Vorosch. leaves and larch (Larix gmelinii (Rupr.) Kuzen.) needles during certain periods of their lives. It is hypothesized that toxic compounds found in these plants resulted in high mortality rates among larvae prior to pupation. Metamorphosis anomalies in the form of larva-pupa intermediates and various morphological defects of pupae are documented for A. menetriesii for the first time. The assumptions of some researchers about the important role of Larix and Aconitum in larval development are questioned.

New occurrences, morphology, and imaginal phenology of the rarest Arctic tiger moth Arctia tundrana (Erebidae: Arctiinae)

This study (1) displays markings pattern of male and female specimens of Arctia tundrana from various parts of its broad range; (2) illustrates a paratype male specimen of this species with its genitalia and aedeagus; (3) presents a few additional occurrences of A. tundrana supplementing the data set published in our earlier paper (Bolotov et al. 2015); (4) provides an updated map of the species’ occurrences; and (5) discusses its imaginal phenology based on long-term occurrence data.