Aline Ferreira de Quadros

An assemblage of terrestrial isopods (Crustacea) in southern Brazil and its contribution to leaf litter processing

We present an assemblage of terrestrial isopods in Parque Estadual de Itapua, southern Brazil, and estimate the contribution of two species to the leaf litter processing. After one year of sampling, we obtained 3748 individuals of six species and four eco-morphologic groups (in order of abundance): Balloniscus glaber Araujo & Zardo, 1995, Atlantoscia floridana (van Name, 1940), Pseudodiploexochus tabularis (Giambiagi de Calabrese, 1939), Trichorhina sp., Alboscia itapuensis Araujo & Quadros, 2005 and Novamundoniscus gracilis Lopes & Araujo, 2003. Total monthly density corresponded to 368 individuals per square meter. The species A. itapuensis and N. gracilis represented less than 1% of total individuals. All the others showed aggregated distribution. Atlantoscia floridana and B. glaber had the highest proportion of individuals occurring together (88%) and a significant species association. Their monthly biomass averaged 4.92 kg ha-1 for B. glaber and 0.97 kg ha-1 for A. floridana. Consumption rates, obtained in the lab (in mg mg-1 day-1) were 0.34 ± 0.04 and 0.70 ± 0.18 for B. glaber and A. floridana, respectively and assimilation efficiency was about 30%. We estimated that both species together could process 860 kg leaves ha-1 year-1.

Terrestrial isopod diversity in the subtropical Neotropics: Itapuã State Park, southern Brazil

We analysed species abundance and composition during one year of sampling at Itapua State Park, a conservation unit in the State of Rio Grande do Sul, southern Brazil. Samples were collected monthly from May 2003 to April 2004 along a 4 km forest trail divided in three transects along the slopes of a small hill. Terrestrial isopods were hand searched by three people for 40 minutes at two sampling sites along each transect, summing 240 minutes of sampling effort per transect per month. Six species distributed in six families were found. The collector curve stabilised when half the samples were taken, demonstrating sampling sufficiency: analytical estimates did not predict more species to be found in the trail. Atlantoscia floridana (van Name, 1940) was dominant in all transects. Abundance varied along the year with a summer and a winter peak, but peaks were not consistent among transects. The first part of the trail, used for ecotourism, was less diverse, had less species (4 as compared to 6 in the other transects), and was thus also less similar in composition.

Postmarsupial development of Atlantoscia floridana (van Name, 1940) (Crustacea, Isopoda, Oniscidea): sexual differentiation and size at onset of sexual maturity

Summary The postmarsupial development of Atlantoscia floridana (van Name, 1940) was studied, with emphasis on the sexual differentiation and maturity. Samples were obtained in the Reserva Biológica do Lami, Porto Alegre, RS, Brazil, during 2000 and 2002. Collected animals were reared in the laboratory under temperatures of about 20±1°C and observed daily. Animals preserved in 70% ethanol were used to analyze sexual maturity. Growth was monitored as each animal moulted for evidence of sexual differentiation. The development of the male genitalia and the female genital pore was described across the different juvenile stages. Female sexual maturity was estimated to occur at a minimum size of 1.04 mm cephalothorax width. Male sexual maturity was estimated from the morphometric relationship between cephalothorax width and length of the genital papilla and indicated the puberal moult to occur at a minimum size of 0.77 mm cephalothorax width. Identification of the size at which sexual maturity occurs allows recognizing the postmarsupial juvenile stages of both males and females: JUI to JU III for males and JU I to JU VI for females. Males reach sexual maturity in approximately 1.5 months after leaving the marsupium, and females in about 3 months.

First report of pigmentation dystrophy in terrestrial isopods, Atlantoscia floridana (van Name) (Isopoda, Oniscidea), induced by larval acanthocephalans

The observation of pigmentation alteration in isopod crustaceans induced by acanthocephalans, known as pigmentation dystrophy, has been documented in North America in species of the aquatic genera Asellus Geoffroy, 1764, Lirceus Rafinesque-Schmaltz, 1820, and Caecidotea Packard, 1871, and in Europe, in Asellus. Recently, three depigmented specimens of Atlantoscia floridana (van Name, 1940), a terrestrial isopod, occurring from >Florida, USA to northern Argentina were found showing pigmentation dystrophy and harboring larval acanthocephalans. Photographic documentation of live and preserved, infected isopods is presented. Morphometric data and photomicrographs of the male, unencysted cystacanth specimen which allowed its placement in the genus Centrorhynchus Luhe, 1911 are presented. This is the first record of the phenomenon of pigmentation dystrophy in terrestrial isopod crustaceans, the first record of A. floridana infected by an acanthocephalan and the first record of a species of Centrorhynchus in a terrestrial isopod.

Growth curve of Balloniscus glaber Araujo & Zardo (Crustacea, Isopoda, Oniscidea) from Parque Estadual de Itapuã, Rio Grande do Sul, Brazil

Based on field data, this study presents the growth curve of Balloniscus glaber Araujo & Zardo, 1995, a terrestrial isopod species found in Parque Estadual de Itapua (PEI), Rio Grande do Sul, Brazil. Specimens were monthly sampled, from May 2004 to April 2005, at PEI. Captured individuals were sexed, their cephalothorax width was measured, and the growth curve was described according to von Bertalanffys model. Male and female growth curves are described by the equations: Wt = 2.256[1-e-0.00394(t+91.128)] and Wt = 2.588[1-e-0.00301(t+101)], respectively. Curves show differential growth between males and females, with females reaching higher W¥, and a slower growth rate than males. Based on theses curves, life span was estimated.

Marsupial extension in terrestrial isopods (Crustacea, Isopoda, Oniscidea)

In Oniscidea, the marsupium is a ventral pouch where the offspring develop independently of an external water source. The marsupium is formed by five pairs of overlapping oostegites that develop in the females during their reproductive period. In this study, ovigerous females of 35 species were dissected, their oostegites were extracted, and the intra-marsupial offspring were counted. Two marsupium forms were recognized: distended, in which the oostegites protrude distally in relation to the sternites; and non-distended, in which the oostegites are parallel to the sixth and seventh sternites. Armadillidium nasatum, A. vulgare, Pudeoniscus birabeni, Circoniscus gaigei and Cubaris murina, conglobating species with a non-distended marsupium, and Neotroponiscus daguerri and N. carolii, non-conglobating species with a distended marsupium, have a concavity on the ventral floor of the 6th and 7th pereionites, here called the marsupial extension. This is the first record of a marsupial extension which extends beyond the area formed by the oostegites in Oniscidea.

Neotropical woodlice (isopoda) colonizing leaf-litter of pioneer plants in a coal residue disposal environment

The irregular disposal of coal combustion residues has adverse impacts on terrestrial ecosystems. Pioneer plants and soil invertebrates play an important role in the recovery of these areas. The goal of this study was to investigate the colonization patterns of terrestrial isopods (Oniscidea) in leaf litter of three spontaneous pioneer plants (grass - Poaceae, shrub – Euphorbiaceae, tree Anarcadiaceae) at sites used for fly ash or boiler slag disposal. The experiment consisted of eight blocks (four per disposal site) of 12 litter bags each (four per plant species) that were randomly removed after 6, 35, 70 or 140 days of field exposure. Three isopod species were found in the litter bags: Atlantoscia floridana (van Name, 1940) (Philosciidae; n = 116), Benthana taeniata Araujo & Buckup, 1994 (Philosciidae; n = 817) and Balloniscus sellowii (Brandt, 1833) (Balloniscidae; n = 48). The isopods colonized the three leaf-litter species equally during the exposure period. However, the pattern of leaf-litter colonization by these species suggests a conflict of objectives between high quality food and shelter availability. The occurrence of A. floridana and the abundance and fecundity of B. taeniata were influenced by the residue type, indicating that the isopods have different degrees of tolerance to the characteristics of the studied sites. Considering that terrestrial isopods are abundant detritivores and stimulate the humus-forming processes, it is suggested that they could have an indirect influence on the soil restoration of this area.