Biotremology in arthropods.

Effective communication is essential in animal life to allow fundamental behavioral processes and survival. Communicating by surface-borne vibrations is likely the most ancient mode of getting and exchanging information in both invertebrates and vertebrates. In this review, we concentrate on the use of vibrational communication in arthropods as a form of intraspecific and interspecific signaling, with a focus on the newest discoveries from our research group in terrestrial isopods (Crustacea: Isopoda: Oniscidea), a taxon never investigated before in this context. After getting little attention in the past, biotremology is now an emerging field of study in animal communication, and it is receiving increased interest from the scientific community dealing with these behavioral processes. In what follows, we illustrate the general principles and mechanisms on which biotremology is based, using definitions, examples, and insights from the literature in arthropods. Vibrational communication in arthropods has mainly been studied in insects and arachnids. For these taxa, much evidence of its use as a source of information from the surrounding environment exists, as well as its involvement in many behavioral roles, such as courtship and mating, conspecific recognition, competition, foraging, parental care, and danger perception. Recently, and for the first time, communication through surface-borne waves has been studied in terrestrial isopods, using a common Mediterranean species of the Armadillidae family as a pilot species, Armadillo officinalis Duméril, 1816. Mainly, for this species, we describe typical behavioral processes, such as turn alternation, aggregation, and stridulation, where vibrational communication appears to be involved.

Are terrestrial isopods able to use stridulation and vibrational communication as forms of intra and interspecific signaling and defense strategies as insects do? A preliminary study in Armadillo officinalis.

The capability of producing sounds and vibrations is well known in insects and is thought to be a form of intra- and interspecific communication. Sounds and vibrations are used and modulated for several aims such as interacting with conspecifics, getting information from the environment, and defending against predators. This phenomenon is less known but also present in other arthropods, including a few roller-type terrestrial isopods. In this study, we used a Y-shape test apparatus to investigate the behavior of adult individuals of Armadillo officinalis Duméril, 1816 (Crustacea: Isopoda: Oniscidea) when exposed to two particular vibrational stimuli, namely species-specific stridulations and non-specific substrate-borne vibrations. Our results showed that adults of A. officinalis significantly react to the presence of both types of vibrational stimuli, by moving away from the vibrational source as if they experienced these vibrations as a sign of danger or disturbance. A. officinalis can produce stridulations only when it rolls into a ball during the so-called conglobation, a possible defense mechanism against predators. Stridulation might thus be a secondary form of defense used during conglobation to deter a predator following contact with it and might be experienced as an alert by conspecifics nearby. The high sensitivity to non-specific substrate-borne vibrations might provide A. officinalis with the possibility to anticipate dangers and adverse conditions, giving it a better chance of survival.

Terrestrial isopods of the family Eubelidae Budde-Lund, 1899 from Iran, with description of a new species (Isopoda, Oniscidea).

In the present work, terrestrial isopods of the family Eubelidae are investigated in Iran. The genera Periscyphis and Somalodillo are reported for the first time. More localities are presented for Koweitoniscustamei (Omer-Cooper, 1923) while K.shafieii Kashani, sp. n. is described and figured. A map indicating the sampling localities for the species is presented.

Presence of a stridulatory apparatus in the manca stages of isopods (Crustacea, Isopoda, Oniscidea).

Armadilloofficinalis Duméril, 1816 (Armadillidae) is a widespread terrestrial isopod species in the Mediterranean basin and on the western coasts of the Black Sea. The species is adapted to live in xeric environments and has mainly nocturnal habits. This species is capable of producing stridulations, which is nowadays recognized as a synapomorphy of the genus. In both sexes, these vibrations are produced by a line of scales on the propodus of pereopod 4 and 5. The main goals of this study are: to describe the manca stages of Armadilloofficinalis; to detect the presence of the stridulatory apparatus in the manca stages; to evaluate the differences of such apparatus in the various manca stages. The manca stages (I, II, III) of Armadilloofficinalis are described for the first time showing: i, the shortest duration (known in literature) of the manca stage I (approximately 30 minutes); ii, the presence of a rudimental stridulatory organ that may be of great importance in terms of evolutionary aspects and adaptation to terrestrial life. Notes on the reproductive biology are also reported. Furthermore, some considerations on future perspectives for A.officinalis as a model species in biotremology are also discussed.

Aggregative behavior and intraspecific communication mediated by substrate-borne vibrations in terrestrial arthropods: An exploratory study in two species of woodlice.

Gregarious behavior and aggregative phenomena among conspecifics in woodlice are thought to be a form of evolutionary adaptation to the terrestrial environment which has given these animals multiple advantages, e.g., against desiccation and predation. The reasons behind these phenomena, however, have not fully been clarified yet. This exploratory study has the aim to assess displacement and aggregation state relatively to the presence of substrate-borne vibrations in two different species of terrestrial isopods. To this goal, a circular arena was used to collect data from adult individuals of Armadillo officinalis, a stridulating species, and Armadillidium vulgare, a non-stridulating species, both exposed and non-exposed to micro-vibrations. Our results showed that exposed individuals of A. officinalis significantly react to micro-vibrations positioning themselves preferentially far from the vibrational source compared to non-exposed individuals of the same species. Furthermore, both the number of aggregates and of isolated subjects significantly increase in the presence of substrate-borne vibrations than in the absence of micro-vibrations. No statistically significant association with substrate-borne vibrations was found for A. vulgare for both placement and number of aggregates and of isolated subjects. Unlike A. vulgare, A. officinalis appears very sensitive to micro-vibrations which seem to represent a source of disturbance or potential danger. Substrate-borne vibrations seem to affect the capability of this species to aggregate leading to a greater number of aggregates and isolated subjects as if animals were a bit disoriented. This behavior might be related to a possible capability of this species to use micro-vibrations for inter- and intraspecific communication.

Changes in turn alternation pattern in response to substrate-borne vibrations in terrestrial isopods.

The present study focuses on the relationship existing between the phenomenon of turn alternation and substrate-borne vibrations in woodlice. Armadillo officinalis was utilized as a behavioral model in comparison to Armadillidium vulgare so as to assess its capability of perceiving external vibrations too. A T-maze with multiple exits was used to collect information on the pattern of turn alternation in i) adult individuals of A. officinalis exposed, and ii) not exposed to micro-vibrations, and iii) adult individuals of A. vulgare exposed to micro-vibrations. Turn alternation was assessed as the number of times that an animal turned on the opposite side in the T-maze. Our results showed a statistically significant association between turn alternation pattern and both exposure to micro-vibrations and species of the animals. According to our best-fitting model, A. officinalis not exposed and A. vulgare exposed to substrate-borne vibrations have 97% and 98% lower odds, respectively of being in a higher category of turn alternations compared to a lower category than exposed individuals of A. officinalis. A. officinalis seems to be very reactive to substrate-borne vibrations, unlike A. vulgare. This different reactivity might be related to a more complex defense mechanism developed as an evolutionary adaptation to the xeric environment, and/or to a means of communication mediated by substrate-borne vibrations, like in insects.

A fast GNU method to draw accurate scientific illustrations for taxonomy.

Nowadays only digital figures are accepted by the most important journals of taxonomy. These may be produced by scanning conventional drawings, made with high precision technical ink-pens, which normally use capillary cartridge and various line widths. Digital drawing techniques that use vector graphics, have already been described in literature to support scientists in drawing figures and plates for scientific illustrations; these techniques use many different software and hardware devices. The present work gives step-by-step instructions on how to make accurate line drawings with a new procedure that uses bitmap graphics with the GNU Image Manipulation Program (GIMP). This method is noteworthy: it is very accurate, producing detailed lines at the highest resolution; the raster lines appear as realistic ink-made drawings; it is faster than the traditional way of making illustrations; everyone can use this simple technique; this method is completely free as it does not use expensive and licensed software and it can be used with different operating systems. The method has been developed drawing figures of terrestrial isopods and some examples are here given.

Iridovirus infection in terrestrial isopods from Sicily (Italy).

During our researches on systematics and ecology of terrestrial isopods, carried out in western Sicily, some specimens showing a blue-purple coloration were collected; they belonged to four species: Armadillidium decorum Brandt, 1833, Trichoniscus panormidensis Montesanto et al., 2011, Philoscia affinis Verhoeff, 1908, Porcellio siculoccidentalis Viglianisi et al., 1992. We hypothesized that such coloration could be due, as reported in literature, to characteristic paracrystalline arrays of virions inside the tissues of blue colored specimens. Ultrastructural observations by transmission electron microscopy, on tissues of A. decorum, showed the presence of electron-dense viral particles, with a diameter of nearly 0.12µm. Dual-axis tomography, performed on specimens of A. decorum, evidenced an icosahedral structure of viral particles matching with that of Isopod Iridescent Virus (IIV). Molecular analysis, on 254bp portion of the major capsid protein (MCP) gene, allowed to place the virus into IIV-31 group, already known for other oniscidean species. The symptoms of infected individuals and the course of the disease were followed in laboratory, indicating similarities with other studies on Isopod Iridoviruses. Moreover, some notes on reproduction of infected ovigerous females are reported. Our data support unequivocal and direct evidences for the first case of IIV infection in terrestrial isopods reported in Italy.

The postmarsupial development of Porcellio siculoccidentalis, with some data on reproductive biology (Crustacea, Isopoda, Oniscidea).

In the broader context of research on the Sicilian Porcellio imbutus-complex, the postmarsupial development of Porcellio siculoccidentalis Viglianisi, Lombardo & Caruso, 1992 was studied in detail. This research was conducted in the laboratory under controlled conditions, allowing us to follow the stages of development, from the formation of the marsupium in ovigerous females until the larval stages and development of the seventh pair of legs. The timing of developmental stages and the morphological modifications of appendages in the postmarsupial manca stages (M I-M III) are described. The manca stage M I had a duration of about one hour. Ovigerous females were collected and reared separately, and the number of parturial molts in the absence of males was counted. The results showed a maximum of four successive parturial molts. Fecundity and fertility were evaluated as the number of eggs and embryos, respectively, inside the marsupium of the ovigerous females. Both parameters were positively correlated with the size of the females. The maximum numbers of eggs and embryos in the marsupium were 113 and 141, respectively. Data describing the total number of postmarsupial mancas released per month indicated that the highest release occurred in April.

The diversity of terrestrial isopods in the natural reserve "Saline di Trapani e Paceco" (Crustacea, Isopoda, Oniscidea) in northwestern Sicily.

Ecosystems comprising coastal lakes and ponds are important areas for preserving biodiversity. The natural reserve "Saline di Trapani e Paceco" is an interesting natural area in Sicily, formed by the remaining strips of land among salt pans near the coastline. From January 2008 to January 2010, pitfall trapping was conducted in five sampling sites inside the study area. The community of terrestrial isopods was assessed using the main diversity indices. Twenty-four species were collected, only one of them endemic to western Sicily: Porcellio siculoccidentalis Viglianisi, Lombardo & Caruso, 1992. Two species are new to Sicily: Armadilloniscus candidus Budde-Lund, 1885 and Armadilloniscus ellipticus (Harger, 1878). This is high species richness for a single reserve in Sicily. The extended sampling period also allowed us to study species phenology. Most of the species exhibited higher activity in spring than in autumn while some species also exhibited lower activity in the summer. The species richness revealed that the study area is in an acceptable conservation status; Shannon and Pielou indices also confirmed a more or less even distribution of individuals belonging to different species.