Population structure and microscale morphological differentiation in a freshwater snail from the Chilean Altiplano.

BACKGROUND: The diversity and population genetic structure of many species have been shaped by historical and contemporary climatic changes. For the species of the South American Altiplano, the historical climatic changes are mainly related to the wet events of great magnitude and regional influence that occurred during the Pleistocene climatic oscillations (PCOs). In contrast, contemporary climate changes are associated with events of lesser magnitude and local influence related to intensifications of the South American Summer Monsoon (SASM). Although multiple studies have analyzed the effect of PCOs on the genetic patterns of highland aquatic species, little is known about the impact of contemporary climate changes in recent evolutionary history. Therefore, in this study, we investigated the change in population structure and connectivity using nuclear and mitochondrial markers throughout the distribution range of Heleobia ascotanensis, a freshwater Cochliopidae endemic to the Ascotán Saltpan. In addition, using geometric morphometric analyses, we evaluated the concomitance of genetic divergence and morphological differentiation. RESULTS: The mitochondrial sequence analysis results revealed the presence of highly divergent co-distributed and geographically nested haplotypes. This pattern reflects an extension in the distribution of groups that previously would have differentiated allopatrically. These changes in distribution would have covered the entire saltpan and would be associated with the large-scale wet events of the PCOs. On the other hand, the microsatellite results defined five spatially isolated populations, separated primarily by geographic barriers. Contemporary gene flow analyses suggest that post-PCO, climatic events that would have connected all populations did not occur. The morphometric analyses results indicate that there is significant morphological differentiation in the populations that are more isolated and that present the greatest genetic divergence. CONCLUSIONS: The contemporary population structure and morphological variation of H. ascotanensis mainly reflect the post-PCO climatic influence. Although both markers exhibit high genetic structuring, the microsatellite and morphology results show the preponderant influence of fragmentation in recent evolutionary history. The contemporary genetic pattern shows that in species that have limited dispersal capabilities, genetic discontinuities can appear rapidly, erasing signs of historical connectivity.

Shape, Microstructure, and Chemical Composition of Pearls from the Freshwater Clam Diplodon chilensis Native to South America.

The capability to produce pearls is widespread in the phylum Mollusca, including bivalves of the superfamily Unionoidea. Here, we identified and characterized natural pearls formed by Diplodon chilensis, a freshwater clam native to southern South America, using samples obtained from two lakes located in the Chilean Patagonia. Pearls were studied using light and scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Naturally formed pearls were found in both male and female D. chilensis specimens. Pearls are produced in different shapes, including spherical, ellipsoidal, buttoned, and bumpy, ranging in size from 200 µm to 1.9 mm. The internal microstructure is composed of irregular polygonal tablets, about 0.40 to 0.55 µm in thickness. EDX analysis showed that pearls are composed of calcium carbonate. FTIR and Raman spectra recorded several peaks attributable to the aragonite in pearls of this species, as has been shown in other mollusks. In addition to these results, pearls of different colors are illustrated.

Genetic Diversity, Morphometric Characterization, and Conservation Reassessment of the Critically Endangered Freshwater Snail, Heleobia atacamensis, in the Atacama Saltpan, Northern Chile.

Evaporitic ecosystems of the Atacama Desert contain a rich endemic fauna, including mollusk species. A recent study performed in the freshwater snail Heleobia atacamensis, endemic to the Atacama Saltpan, revealed a strong interdependence of genetic patterns with climatic fluctuations and landscape physiography. The species is currently listed as Critically Endangered at regional scale and as Data Deficient on the International Union for Conservation of Nature (IUCN) Red List. Here, we studied genetic diversity and demographic history of several populations of the species occurring on a connectivity gradient, including snails from new peripherical localities (Peine and Tilomonte), which were compared with topotype specimens. In addition, we reassessed the conservation status using the IUCN Red List categories and criteria considering species-specific idiosyncrasy. Phylogenetic and phylogeographical analyses indicated that snails from Peine and Tilomonte belong to H. atacamensis. We discovered significant differentiation in shell morphology, which was generally greater in geographically isolated populations. We also inferred six genetic clusters and a demographic expansion congruent with the wet periods that occurred at the end of the Pleistocene. Considering the highest risk category obtained, H. atacamensis was reassessed as Endangered at regional scale. Future conservation plans should consider the genetic assemblages as conservation units.

Distribution, conservation status and proposed measures for preservation of Radiodiscus microgastropods in Chile.

The genus Radiodiscus includes minute terrestrial snails occurring throughout the American continent. We assessed the conservation status of eight poorly known Chilean Radiodiscus species using the International Union for Conservation of Nature (IUCN) and NatureServe categories and criteria. Under the IUCN guidelines the species were assessed using the Criterion B of geographic range, which considers the extent of occurrence (EOO) and area of occupancy (AOO) as subcriteria. For NatureServe we used these two parameters plus the number of occurrences, ecological viability, and threats. Considering species rarity and possible sampling bias, we also used ecological niche modeling to determine climate and environmental tolerances and predict potential species distributions analyzing bioclimatic and geographical layers. Radiodiscus australis, R. coarctatus and R. quillajicola were listed as Critically Endangered by IUCN and NatureServe standards; R. coppingeri, R. flammulatus, R. magellanicus and R. villarricensis as Endangered by both methods; while R. riochicoensis as Endangered by IUCN standards and Vulnerable by NatureServe standards. Niche modeling results indicated that Radiodiscus species respond to different environmental conditions and that the predicted distribution areas contain suitable habitats beyond the current ranges, which may be helpful for future management plans. Nature-based sport tourism, forestry activities, urbanization, roads, pollution, mining, forest fires, livestock, volcanism, tsunamis, soil erosion and introduced species are among the major threats affecting these snails. Based on the low number of occurrences and the threats identified, the most at-risk species are R. coarctatus and R. quillajicola (one record), R. australis (two records) and R. villarricensis (three records); the latter two lacking occurrences within protected areas. Compiling our findings, we propose a list of actions to preserve Chilean Radiodiscus species.

Reproductive aspects of the poorly known and critically endangered freshwater snail Heleobia atacamensis (Gastropoda: Truncatelloidea).

Knowing the reproductive biology of threatened species is essential for conservation and to establish proper management plans. Heleobia atacamensis, a freshwater snail only known from two locations in the Atacama Saltpan, northern Chile, is currently classified as Data Deficient on the IUCN Red List and Critically Endangered by the Ministerio del Medio Ambiente of Chile. Based on size-frequency distribution, multivariate analysis of shell measurements, and microdissections, we studied the reproductive strategy, recruitment period, sex ratio and sexual dimorphism in this species. Heleobia atacamensis is an oviparous species, with direct development (non-planktotrophic). Females lay capsules of a single egg from which a juvenile resembling a miniature adult hatches after intracapsular metamorphosis is completed. The development type was confirmed by the observation of a paucispiral protoconch (= protoconch I) using scanning electron microscopy. Recruitment was observed across the four seasons of the year, with an increment at the end of austral summer. Results also showed that sex ratio was 1:1, whereas sexual dimorphism was not detected using univariate and multivariate analysis of the shell. The reproductive data provided in this study are a starting point for future management plans.

Phylogeography and molecular species delimitation reveal cryptic diversity in Potamolithus (Caenogastropoda: Tateidae) of the southwest basin of the Andes.

The species of the genus Potamolithus inhabiting the southwestern basin of the Andes are difficult to distinguish due to small size and similar shell morphology. Only Potamolithus australis and Potamolithus santiagensis have been traditionally recognized in this region, but the occurrence of several morphologically similar undescribed populations could increase the regional richness. Here we delimit described and potentially undescribed cryptic species of the genus using partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene. Network analysis and diversity indices inferred six highly differentiated haplogroups, many of them sympatric and widespread in the study area. Phylogeographic analyses suggest a scenario of recent diversification and the occurrence of multiple refuges during the successive Pleistocene glaciations. Phylogenetic analysis also recovered six major clades that showed no relationship with physiography. Species delimitation analyses consistently recognized three or four candidate species apart from P. australis and P. santiagensis. Divergence times indicate that speciation of Chilean Potamolithus began at the end of the Pliocene, probably driven by climatic rather than geographic events. Considering the high inter- and intra-basin genetic diversity, conservation efforts should be focused on protecting sympatric taxa in the basins with the highest species richness.

Morphological and molecular identification of the invasive freshwater snail Physa acuta (Gastropoda: Physidae) into Llanquihue Lake, Chilean Patagonia.

The sewage snail Physa acuta, native to North America, is an effective invasive species around the world. In Chile, it was first reported in 2014 in the north central area of the country. So far, the species has not been recorded in southern Chile. Sampling performed in 2015 in three localities from Llanquihue Lake, Chilean Patagonia, only provided native freshwater snails. However, new collections performed in February 2018 in the same three sites were successful for physid specimens suggesting a biological invasion entailing a large southward range expansion of these snails. Here we performed morphological, microstructural and phylogenetic analyses to investigate whether the new samples belong to Physa acuta. The shell morphology, male copulatory complex and radula microstructure of the new material agree with those of the sewage snail. The molecular phylogenetic analyses using the cytochrome c oxidase subunit 1 (COI) gene confirmed morphological identification. We suggest to take prompt measures to prevent the expansion of Physa acuta in Llanquihue Lake or nearby aquatic ecosystems.

A new species of Psectrascelis (Coleoptera: Tenebrionidae: Pimeliinae) from the coastal dunes of the Atacama Desert, Chile.

Psectrascelis is one of the most specious genus of darkling beetles of South America, comprising 82 species that inhabit arid and semiarid environments. The species are distributed mainly in Argentina and Chile. In general, the taxonomy of several species in this group has been difficult to approach. An example is Psectrascelis pilosa Solier and Psectrascelis conjugens Fairmaire, species morphologically similar which presents a rather poor original description and mislabelled. These species are distributed sympatrically in coastal terraces at the northern side of Huasco river, northern Chile. We collected several specimens of Psectrascelis on the southern side of Huasco river which are morphologically similar to P. pilosa. Morphological and genetic analysis support the description of the species Psectrascelis ammophila sp. nov., which is more closely related to Psectrascelis elongata and Psectrascelis pilipes specularis than other morphologically similar species (Psectrascelis pilosa and Psectrascelis conjugens). The importance of the Huasco river as barrier and the evolutionary convergence is discussed to explain the crypsis and the phylogenetic pattern found.

Morphological and molecular analysis of cryptic native and invasive freshwater snails in Chile.

Species delimitation in minute freshwater snails is often difficult to perform using solely shell morphology. The problem intensifies when invasive species spread within the distribution range of morphologically similar native species. In Chile, the Truncatelloidean snails are represented by the native genera Heleobia and Potamolithus plus the invasive mudsnail Potamopyrgus antipodarum, which can easily be confused. Using an integrative approach, we performed molecular phylogenetic analysis and studied reproductive and morphological features to identify superficially similar forms inhabiting the central area of the country. Truncatelloidean snails were identified in 40 of 51 localities sampled, 10 containing Potamopyrgus antipodarum, 23 Heleobia and 7 Potamolithus. Based on these results and previously published data, the known distribution of the mudsnail in Chile encompasses 6 hydrological basins, including 18 freshwater ecosystems. The finding of the mudsnails in several type localities of native species/subspecies of "Heleobia" that were not find in situ suggests species replacement or significant extinction of native fauna, a hypothesis supported by the restudy of type material that shows that endemic forms belong to the genus Potamolithus. This study shows the usefulness of integrative taxonomy not only resolving complex taxa with cryptic morphology but also measuring the extent of an ongoing invasion.

Influenced but not determined by historical events: genetic, demographic and morphological differentiation in Heleobia ascotanensis from the Chilean Altiplano.

In the present study, we focus on the phylogeographic pattern, demographic history and morphological differentiation of Heleobia ascotanensis, a freshwater gastropod restricted to the Ascotán saltpan in the Chilean Altiplano. The current distribution of the species is limited to twelve isolated or partially isolated springs that were affected by transitions between humid and arid periods during last glaciations. The genetic analysis of 322 specimens showed that H. ascotanensis is subdivided into three genetically divergent populations, with low and moderate degrees of historical gene flow among them and incipient morphological differentiation as a consequence of genetic and geographical isolation. Molecular analyses revealed different demographic histories among populations which seem to respond independently to climatic events, probably due to an environmental imposition and idiosyncratic strategies developed to cope with water availability. The results of this study and co-distributed taxa support the hypothesis that contemporary and historical events have influenced microevolutionary differentiation of these snails, although there is a need to complement further information to predict genetic or morphological divergence at microgeographic scale.

No more machismo in Callyntra (Coleoptera: Tenebrionidae): Callyntra femina, a new species discovered based on female genitalia and genetic evidence.

Callyntra is a genus of tenebrionid beetles endemic to the Southern Cone region of South America, with 23 species occurring in Chile and one shared with Argentina. The recent descriptions of new species were commonly based on the male genitalia structure, underestimating the utility of the female genitalia for this purpose. Analysis of the ovipositor structure of a series of females assigned to Callyntra carbonaria from the Bío-Bío and Araucanía in Southern Chile, have resulted in the discovery of a new species, Callyntra femina sp. nov., which was corroborated through molecular analysis using COI and 16S gene fragments. The phylogenetic analysis recovered C. femina as sister to a clade composed of C. rossi, C. carbonaria and C. riverai, being genetically more similar to C. rossi.

A new species of Heleobia (Caenogastropoda: Cochliopidae) from the Chilean Altiplano.

Cochliopidae Tryon, 1866 is a diverse family of caenogastropods that lives in a wide variety of aquatic habitats primarily in the New World (Hershler &Thompson 1992). In Chile, the species of the group have been traditionally assigned to the genus Littoridina Souleyet, 1852 using conchological characters (Biese 1944, 1947; Stuardo, 1961; Valdovinos 2006) but according to anatomical studies and phylogenetic analysis the majority of them have been reassigned to the genus Heleobia Stimpson, 1865 (Hershler & Thompson 1992; Collado et al. 2011a; Kroll et al. 2012; Collado et al. 2013; Collado et al. 2016). Here we formally describe a new species of the genus Heleobia from Spring 1 in the Carcote saltpan, Chilean Altiplano, based on molecular and morphological characters. Snails from this locality were previously shown to be distinct based on DNA sequences (Collado et al. 2013; Collado et al. 2016).

A new freshwater snail (Caenogastropoda: Cochliopidae) from the Atacama Desert, northern Chile.

In the family Cochliopidae, Heleobia Stimpson, 1865 is the most speciose genus in South America, with about 90 species (Hershler & Thompson 1992; Cazzaniga 2011). A recent molecular and morphological analysis performed in northern Chile (Atacama Desert) showed that the previously undescribed springsnails from Aguada de Chorrillos belong to Heleobia (Collado et al. 2013). In this study I formally describe this new species. Although this paper does not treat morphology in detail, the anatomical characters, in combination with the previously published molecular data provides a strong basis for recognizing this population as a distinct species.

Epipodium morphology of Prisogaster niger (Mollusca: Vetigastropoda): revealing potential autapomorphies of diagnostic value for the prisogasterinae / Morfología del epipodio de Prisogaster niger (mollusca: vetigastropoda): revelando autapomorfías potenciales de valor diagnóstico para prisogasterinae

In this work the epipodium morphology of the marine snail Prisogaster niger is described. In this gastropods the epipodium includes a complex of structures among which the neck lobes, epipodial ridge, epipodial tentacles and epipodial papillae constitute the most remarkable characters. Although these features are commonly found among trochoidean taxa, the observation of the epipodium, compared with the literature, revealed potential autapomorphic characters of diagnostic value for the genus and the subfamily Prisogasterinae, like epipodial lamellae and epipodial tuft.

En este trabajo se describe la morfología del epipodio del caracol marino Prisogaster niger. En esta especie el epipodio está conformado por un complejo de estructuras entre las cuales los lóbulos del cuello, rebordes epipodiales, tentáculos epipodiales y papilas epipodiales constituyen conspicuos caracteres. El estudio de la morfología del epipodio reveló potenciales autapomorfías de valor diagnóstico para la subfamilia Prisogasterinae.

Anatomía microscópica del sistema reproductor en dos especies simpátricas del género fissurella bruguiére, 1789 (mollusca: vetigastropoda) / Microscopic anatomy of the reproductive system in two sympatric species of Fissurella Bruguiére, 1789 (Mollusca: Vetigastropoda

This study describes the microscopic anatomy of the reproductive systems of the keyhole limpets Fissurella latimarginata and Fissurella cumingi to test the existence of a possible isolating reproductive mechanism of morphophysiological type between species, and consequently to determine if the findings provide a valid taxonomic characteristic to distinguish these sympatric species. The results show that in both species the reproductive system is intimately associated with the excretory system. The gonad has a septa organization, and is connected with the distal portion of the right kidney by means of a renopericardial duct which functions as a genital duct. The gametes are evacuated to the mantle cavity through the right kidney opening. Besides transport of the gametes, the genital duct, which connects with the pericardium through the nephrostome, bears a gland attached to its inner wall both in males and females. No marked anatomical differences were noted between the reproductive systems of the two limpets which would allow their unequivocal taxonomic differentiation at the species level.

Este trabajo describe la anatomía microscópica del sistema reproductivo en las lapas Fissurella latimarginata y Fissurella cumingi, para examinar la posible existencia de un mecanismo de aislamiento reproductivo del tipo morfofisiológico y consecuentemente, determinar si el sistema reproductivo presenta algún carácter taxonómico válido que permita distinguir estas especies simpátricas. Los resultados muestran que en ambas especies y sexos el sistema reproductivo se relaciona con el sistema excretor. La gónada, de organización en septos, comunica con la porción distal del riñon derecho distal por medio del canal renopericárdico que funciona como conducto genital. Los gametos son evacuados a la cavidad del manto a través de la apertura renal derecha. Además de transportar los gametos, el conducto genital, que comunica con el pericardio a través del nefrostoma, presenta una glándula adosada a la pared interna en los machos y en las hembras. No se detectaron diferencias anatómicas marcadas del sistema reproductivo que permitan diferenciar las especies inequívocamente por lo que este sistema tiene bajo valor taxonómico a nivel específico.