Ecology and behaviour of the ‘road tarantulas’ Eupalaestrus weijenberghi and Acanthoscurria suina (Araneae,Theraphosidae) from Uruguay

Spatial distribution, burrow morphology, phenology, defensive displays and predation of two theraphosid spiders living in meadows were studied in Uruguay. Exhaustive field studies complemented with laboratory observations were carried out. Eupalaestrus weijenberghi occurred throughout the country while Acanthoscurria suina occurred only in the southern half. Both species seemed to be the most abundant theraphosid spiders in Uruguay as they live in the dominant landscape of the country. Burrows from both species showed a similar morphological pattern but a terminal narrow tube was found only in E. weijenberghi. We observed that A. suina always co‐occurred with E. weijenberghi but this species frequently occurred in the absence of the former. When co‐occurring A. suina showed an aggregated distribution while E. weijenberghi was randomly distributed. A restricted reproductive period was found for both species, mainly between March and April, evidenced by the massive presence of walking adult males and then confirmed by pit‐fall traps. Moulting, oviposition and longevity were also studied. Conspicuous species‐specific defensive behaviours were displayed by the tarantulas in all cases, when collected. These tarantulas showed spatial co‐occurrence and temporal coexistence with the beetle Diloboderus abderus, an important pest of grasslands. Tarantula predation on adult beetles was confirmed, these spiders being one of the few beetle predators. Their maximal efficiency in beetle predation could reach 65?000 prey captured per hectare by month. These polyphagous tarantulas seem to be potential agents for the biological control of beetle pests.     

Another migid in the wall: natural history of the endemic and rare spider Calathotarsus simoni (Mygalomorphae: Migidae) from a hill slope in central Argentina

A population of Calathotarsus simoni Schiapelli and Gerschman (1975) was discovered on a hillside in the Ventania system, Argentina. Our objectives were to quantify burrow density, record burrow morphology and door characteristics and describe the micro-habitat. We counted 57 burrows and report a density of 0.01 burrows/m². Aggregation indices suggest that burrows are aggregated under some area plots but more evenly distributed on others. The trapdoor is thick and rigid with bevelled edges connected to the entrance rim by a narrow articulated hinge. Two egg sacs from females were obtained and data on eggs and spiderlings are presented. We registered six burrows of an undetermined species of Actinopus. While a few specimens of Actinopus sp. were found inhabiting this hillside, the highest proportion of burrows belonged to C. simoni. Spider diversity on the hillside shows the predominance of Linyphiidae, Nemesiidae and Gnaphosidae. One juvenile of C. simoni was captured using pitfall traps.     

Temporal changes in burrow structure of the thalassinidean ghost shrimps Trypaea australiensis and Biffarius arenosus

The thalassinidean ghost shrimps Trypaea australiensis and Biffarius arenosus are dominant burrowing macroinvertebrates of soft‐sediment habitats in Western Port, Victoria, Australia. Burrow structure has been described for both species but little is known about how the burrows change over time. This study used resin casting to investigate temporal variation by making burrow casts each month over a 12‐month period. It was found that the overall burrow morphology of both T. australiensis and B. arenosus was consistent over time, but in the warmer months (summer and spring), both species constructed burrows that were deeper and of greater volume than burrows constructed in winter and autumn. Possible reasons for this variation are discussed.     

Factors influencing anuran distribution in coastal dune wetlands in southern Brazil

We investigated the potential role of hydroperiod and habitat structural complexity as explanatory factors defining richness, abundance and spatial and temporal distribution of anurans in wetlands of coastal dunes. This survey was performed in 15 wetlands along the Atlantic coastal zone of southern Brazil. We identified 10 anuran species (nine in the adult and eight in the tadpole stage) distributed in seven genera from five families. The adult richness and abundance varied among the hydroperiod classes, but without temporal variations. Both tadpole richness and abundance varied temporally and both were influenced by hydroperiod. Adult anuran composition was associated with dry months and wetland area, whereas tadpole composition was associated with emergent and floating macrophytes, wetland area and vegetation cover. This study identified the importance of habitat structural complexity and hydroperiod in spatial–temporal distribution models of anurans.     

Two new amphipod crustaceans of the genus Bahadzia from ‘blue holes’ in the Bahamas and some remarks on the origin of the insular stygofaunas of the Atlantic

Bahadzia setimana sp. nov. from South Andros, and B. obliqua sp. nov. from Cat Island, both in the Bahamas, are described. The recently described genus Bahadzia now contains five closely related taxa, each apparently confined to a single island or isolated group of islands, in a restricted area of the West Indies, ranging from Haiti in the south to the northern Bahamas.

The present discoveries show not only that low-salinity groundwaters of the West Indies have a marked degree of insular endemism, but that the high-salinity anchihaline habitats possess endemics in certain groups as well.

Current models which seek to explain the evolution of stygobionts on Atlantic Islands are reviewed critically and the most likely synthesis is provided.     

The affinities of European sand gobies (Teleostei: Gobiidae)

The European ‘sand-goby’ genera, comprising the Atlantic-Mediterranean Pomatoschistus and Gobiusculus, Ponto-Caspian Knipowitschia and West Balkanian Economidichthys, are diagnosed, with special reference to patterns of infraorbital neuromast organs (sensory papillae). A survey of selected meristic features indicates synapomorphies in increased number of abdominal and caudal vertebrae, and additional interneural spaces between first and second dorsal fin pterygiophores. Absence of a crest-like postmaxillary process on the premaxilla was found to be another derived feature after a survey of this bone throughout the Gobioidei. Affinity with other Atlantic-Mediterranean genera (Deltentosteus, Buenia, Lebetus and, probably, Speleogobius) is established from both morphological and isozyme criteria. Using head lateral-line and meristic characters, as well as occurrence of the premaxilla crest, a search for a sister group has led to the Indo-Pacific Nesogobius, a genus endemic to southern Australian seas, and probable wider relationship to North-western Pacific endemic gobiids.     

Notes on astogeny of some Petraliellidae (Bryozoa) from Australia

Members of the bryozoan family Petraliellidae share the capacity to develop basal rhizoids, which anchor the unilaminar, semi-repent parts of the colonies above the substratum, and enable them to overgrow other, competing sessile forms. Little is known of the larval behaviour and settlement, or the early astogeny of species. Ancestrulate colonies of the Australian Tertiary lunulitiform species Smittia biincisa are referred to the genus Riscodopa, and together with Riscodopa paucipora sp. nov. are described and compared with the Recent species R. cotyla and R. parva from New Zealand, and with R. hyalina sp. nov. from New South Wales, Australia. All the Recent species are known to develop basal rhizoids, and an early astogeny similar to that of many other small, rooted bryozoans, comprising the post-metamorphosis development of a binary complex, including rhizoid and feeding elements, is inferred for Riscodopa. Observations on living Hippopetraliella magna from Queensland suggest that both the ancestrular morphology and early astogeny show a capacity for semi-repent growth, even though they do not include rhizoid development. Larvae metamorphose without direct attachment, and the ancestrula develops elongated, partially calcified supporting processes, which raise the early stages of growth above the substratum. A similar kind of ancestrula has been found in preserved specimens of Mucropetraliella ellerii.