Shell Morphology Research Articles

Differentiation of Bulinussenegalensis and Bulinusforskalii Snails in West Africa Using Morphometric Analysis

PurposeAccurate identification of medically important intermediate host and vector species is crucial for understanding disease transmission and control. Identifying Bulinus snails which act as intermediate host species for the transmission of schistosomiasis is typically undertaken using conchological and genital morphology as well as molecular methods.MethodsHere, a landmark-based morphometric analysis of shell morphology was undertaken to determine its utility to distinguish the closely related and morphologically similar sister species Bulinus senegalensis and Bulinus forskalii. The method was developed to increase the accuracy of conchological morphology methods to identify Bulinus species in the field. Both species are found in West Africa, but only B. senegalensis is implicated in the transmission of urogenital schistosomiasis.ResultsWe found when scaled down to the same length, 3-whorl and 4-whorl (juvenile) B. senegalensis shells had a longer spire, narrower body whorl and shorter aperture than B. forskalii. In contrast, 5-whorl (adult) B. senegalensis had a shorter spire, but still had a shorter aperture and narrower body whorl than B. forskalii. Canonical Variate Analysis (CVA) showed minimal overlap between B. senegalensis and B. forskalii for 3-whorl and 4-whorl shells, with a clear separation for 5-whorl shells. Overall, B. senegalensis had a consistently shorter aperture size and narrower body whorl than B. forskalii for all development stages. Spire length was variable depending on the stage of development, with 3-whorl and 4-whorl shells having the opposite trends of adult shells.ConclusionsOur study demonstrates the applicability of landmark-based morphometrics in distinguishing the medically important, Bulinus senegalensis from its morphologically similar sister species, Bulinus forskalii. We recommend using measurements based on spire length, penultimate whorl length, body whorl width and aperture size to differentiate B. senegalensis and B. forskalii, when used with the appropriate information for each shell’s development stage.

Shell shape does not accurately predict self-righting ability in hatchling freshwater turtles

Flat hydrodynamic shells likely represent an evolutionary trade-off between adaptation to an aquatic lifestyle and the instability of more rounded shells, thought beneficial for self-righting. Trade-offs often result in compromises, this is particularly true when freshwater turtles, with flatter shells, must self-right to avoid the negative effects of inverting. These turtles, theoretically, invest more biomechanical effort to achieve successful and timely self-righting when compared to turtles with rounded carapaces. This increase in effort places these hatchlings in a precarious position; prone to inversion and predation and with shells seemingly maladapted to the act of self-righting. Here, we examine hatchling self-righting performance in three morphologically distinct freshwater turtle species (Apalone spinifera, Chelydra serpentina and Trachemys scripta scripta) that inhabit similar environmental niches. We demonstrate that these hatchlings were capable of rapid self-righting and used considerably less biomechanical effort relative to adult turtles. Despite differences in shell morphology the energetic efficiency of self-righting remained remarkably low and uniform between the three species. Our results confound theoretical predictions of self-righting ability based on shell shape metrics and indicate that other morphological characteristics like neck or tail morphology and shell material properties must be considered to better understand the biomechanical nuances of Testudine self-righting.

Geometric morphometric methods for identification of oyster species based on morphology.

Both genetic and environmental factors affect the morphology of oysters. Molecular identification is currently the primary means of species identification, but it is inconvenient and costly. In this research, we evaluated the effectiveness of geometric morphometric (GM) techniques in distinguishing between two oyster species, Crassostreagigas and C.ariakensis. We used traditional morphometric and GM methods, including principal component analysis (PCA), thin-plate spline analysis (TPS) and canonical variable analysis (CVA), to identify specific features that distinguish the two species. We found that differences in shape can be visualised using GM methods. The Procrustes analysis revealed significant differences in shell morphology between C.gigas and C.ariakensis. The shells of C.ariakensis are more prominent at the widest point and are more scattered and have a greater variety of shapes. The shells of C.gigas are more oval in shape. PCA results indicated that PC1 explained 45.22%, PC2 explained 22.09% and PC3 explained 10.98% of the variation between the two species, which suggests that the main morphological differences are concentrated in these three principal components. Combining the TPS analysis function plots showed that the shell shape of C.ariakensis is mainly elongated and spindle-shaped, whereas the shell shape of C.gigas is more oval. The CVA results showed that the classification rate for the two species reached 100% which means that C.ariakensis and C.gigas have distinct differences in shell morphology and can be completely separated, based on morphological characteristics. Through these methods, a more comprehensive understanding of the morphological characteristics of different oyster populations can be obtained, providing a reference for oyster classification and identification.

Assessment of the genetic diversity of lymnaeid (Gastropoda: Pulmonata) snails and their infection status with trematode cercariae in different regions of Thailand

Lymnaeid snails are some of the most widespread snails and are the first intermediate host of trematode parasites that affect human and livestock health. A full understanding of the genetic relationship of hosts and parasites is of paramount importance for effective parasite management. The present study assessed the prevalence of trematode larvae in lymnaeid snails and examined the genetic diversity of these snails collected across Thailand. We collected 672 lymnaeid snails from 39 locations in 22 provinces of six regions in Thailand. Subsequently, cercarial infection in the snails was observed by using the shedding method. Lymnaeid snails released 5 types of trematode cercariae, namely, xiphidiocercariae, echinostome cercariae I, echinostome cercariae II, furcocercous cercariae, and strigea cercariae. The phylogenetic analysis based on ITS2 and 28S rDNA sequences revealed 5 cercaria types assigned to four trematode families, of which two belong to the group of human intestinal flukes. Combination of shell morphology and sequence analysis of the mitochondrial COI and 16S rDNA genes, the lymnaeid snails were classified into two species, Radix rubiginosa and Orientogalba viridis. Moreover, the combined dataset of mtDNA genes (COI + 16S rDNA) from R. rubiginosa and O. viridis revealed 32 and 15 different haplotypes, respectively, of which only a few haplotypes were infected with cercariae. The genetic diversity and genetic structure revealed that R. rubiginosa and O. viridis experienced a bottleneck phenomenon, and showed limited gene flow between populations. Population demographic history analyses revealed that R. rubiginosa and O. viridis experienced population reductions followed by recent population expansion. These findings may improve our understanding of parasite–lymnaeid evolutionary relationships, as well as the underlying molecular genetic basis, which is information that can be used for further effective control of the spread of trematode disease.

Insights into structural defect formation in individual InP/ZnSe/ZnS quantum dots under UV oxidation

InP/ZnSe/ZnS quantum dots (QDs) stand as promising candidates for advancing QD-organic light-emitting diodes (QLED), but low emission efficiency due to their susceptibility to oxidation impedes applications. Structural defects play important roles in the emission efficiency degradation of QDs, but the formation mechanism of defects in oxidized QDs has been less investigated. Here, we investigated the impact of diverse structural defects formation on individual QDs and propagation during UV-facilitated oxidation using high-resolution (scanning) transmission electron microscopy. UV-facilitated oxidation of the QDs alters shell morphology by the formation of surface oxides, leaving ZnSe surfaces poorly passivated. Further oxidation leads to the formation of structural defects, such as dislocations, and induces strain at the oxide-QD interfaces, facilitating In diffusion from the QD core. These changes in the QD structures result in emission quenching. This study provides insight into the formation of structural defects through photo-oxidation, and their effects on emission properties of QDs.

Two new species and a new record of stygobitic freshwater snails (Gastropoda, Cochliopidae) from Candela, Coahuila, northern Mexico.

We describe two new species and a new record of stygobitic gastropods from small groundwater-fed springs in Candela, Coahuila, northern Mexico. Phreatomascogos garciasaucedoi n. sp. is described based on shell morphology and is the second species of this formerly monotypic genus. According to the current classification, we have transferred this genus to Cochliopidea. Phreatodrobia candelensis n. sp. is described, and represents the first record of the genus in Mexico extending its known range more than one hundred kilometers to the south. Also found with the new stygosnails was Coahuilix hubbsi Taylor, 1966, which was previously known only as an endemic species from the neighboring Cuatro Cinegas valley. The reported new subterranean snails are restricted in their distributions to two small water sources only a few meters long which flow directly into a touristic zone with swimming pools and other recreation areas. Using NatureServe Ranking, both new species were assigned as critically imperiled. The very limited distribution and negative anthropogenic impacts within the sites should draw special conservation attention for the reported stygobionts.

Release the confetti! A new genus and species of Indo-West Pacific bubble snails (Cephalaspidea: Haminoeidae)

ABSTRACT The bubble snail family Haminoeidae has traditionally been the richest in genera within Cephalaspidea; however, most of these genera were erected based on only the characteristics of the shell or external morphology. The family was recently revised through a combined analysis of DNA, internal anatomy, and external body and shell morphology, leading to major taxonomic rearrangements and a drastic reduction in the number of genera. However, these analyses also show that there may still be undefined genera and certainly several undescribed species waiting to be discovered. In this work, a new genus and species is described in light of recent revisions within Haminoeidae and the phylogenetic hypothesis generated by Oskars and colleagues. Due to its colourful external anatomy, the new species was initially assumed to belong to Lamprohaminoea, but the specimens failed to produce DNA sequences that could confirm this hypothesis. During further anatomical study of species of Lamprohaminoea and further examination of these specimens, it became clear that the morpho-anatomical features of Confettiella malaquiasi gen. n. and sp. n. distinguish it from this genus and all other genera and species of the Haminoeidae. To illustrate this, shells, external features of the animals, and anatomical characters of the jaws, radula, gizzard plates, and female and male reproductive system were studied by optical and scanning electron microscopy, and these studies are reported here. http://www.zoobank.org/urn:lsid:zoobank.org:pub:E4AE4023-F7FF-4A6B-9B93-9E5A370067C7 http://www.zoobank.org/urn:lsid:zoobank.org:pub:9B0BDC04-6622-47CE-B81C-C1CE2C17B8E

An X-Ray Synchrotron Shell and a Pulsar: The Peculiar Supernova Remnant G32.4+0.1

We present a deep Chandra observation of the shell supernova remnant (SNR) G32.4+0.1, whose featureless X-ray spectrum has led to its classification as an X-ray synchrotron-dominated SNR. We find a partial shell morphology whose outline is quite circular, with a radius of about 11 pc at an assumed distance of 11 kpc. Thermal and power-law spectral models for three relatively bright regions provided equally good fits, but the absence of spectral lines required ionization timescales from thermal fits that are inconsistent with the mean densities derived from emission measures. We thus confirm the nonthermal, i.e., synchrotron, origin of X-rays from G32.4+0.1. Shock velocities needed to accelerate electrons to the required TeV energies are ≳1000 km s−1, giving a remnant age ≲ 5000–9000 yr. There is no obvious X-ray counterpart to the radio pulsar PSR J1850−0026, but its position adjoins a region of X-ray emission whose spectrum is somewhat harder than that of other regions of the shell, and which may be a pulsar-wind nebula (PWN), though its spectrum is steeper than almost all known X-ray PWNe. The distance of the pulsar from the center of symmetry of the shell disfavors a birth in a supernova event at that location only a few thousand years before; either the pulsar (and putative PWN) are not associated with the shell SNR, requiring a coincidence of both position and (roughly) absorbing column density, or the SNR is much older, making the origin of nonthermal emission problematic.

Copper Stress Causes Shell Morphology Changes in Early Juvenile Anodonta woodiana Based on Geometric-Morphometric Analysis.

In this study, the morphological characteristics of early juvenile shells of Anodonta woodiana, which were exposed to different concentrations of aqueous copper, were analyzed using 10 landmarks to determine morphological changes in the shells. Morphological changes mainly occurred at the top of the shell and front and back ends of the central axis. Stepwise discriminant analysis proved shape differences among experimental and control groups. The results of this study demonstrate for the first time that environmentally relevant copper concentrations cause stress-related morphological changes in A. woodiana in the vulnerable early juvenile stage.

Can the native crab Thalamita danae be an effective biological control agent of the invasive mussel Xenostrobus securis in Hong Kong?

AbstractLocal predators are often considered effective and environmentally-friendly control agents to limit invasive species. Such biological control, however, depends on both the predator prey preferences and performances, which are in turn affected by variations in the physical environment. This study investigated the predation of the swimming crab Thalamita danae on the invasive mussel Xenostrobus securis under different salinity and thermal conditions. Xenostrobus securis, which is native to Australia, has spread to Hong Kong since the last decade, causing adverse ecological and economic impacts. Laboratory experiments evaluated the prey preferences and feeding behaviours of the crab on both the native mussel Brachidontes variabilis and the invasive X. securis under different typical salinities (15, 25, and 35‰) and temperatures (22 and 28 °C). The crab did not show clear preference toward either the invasive or the native mussels. Although the shell morphology of the invasive mussels lowered handling time as compared to the native mussels, the crab consumption rate was similar between the mussel species. The survival and predation rate of the crab were, however, substantially reduced under low salinities (< 15‰) where X. securis could be found. Thalamita danae, therefore, is a potential predator of X. securis, but such predation is only possible under normal, oceanic conditions. In hyposaline, estuarine/ freshwater environments where X. securis can survive, however, T. danae performs poorly and, as a result, such physical conditions may represent a predator refuge for the mussels to invade local ecosystems.

Alvania pluricosticillata Chirli & Forli, 2021 junior synonym of Crisilla gagliniae (Amati, 1985)

Based on similarity in shell morphology, it is proposed that Alvania pluricosticillata Chirli & Forli, 2021 (fossil, recently described from the Plio-Pleistocene of Tuscany and Calabria) and Crisilla gagliniae (Amati, 1985) (extant, originally described from eastern Sicily) actually represent a single species. By priority, Crisilla gagliniae is the name to use for this species.

New records of Provanna (Gastropoda, Provannidae) from the Costa Rica Margin and an identification key for the genus.

Consistent species identification is foundational to biological research and requires coordination among a diversity of researchers and institutions. However, such consistency may be hindered for rare organisms where specimens, identification resources, and taxonomic experts are few. This is often the case for deep-sea taxonomic groups. For example, the deep-sea gastropod genus Provanna Dall, 1918 is common at chemosynthetic sites throughout the world's oceans, yet no formal guide to these species has yet been produced. Recent exploration has recovered new specimens of Provanna from hydrocarbon seeps off the Pacific Costa Rica Margin. The current work assesses the species identity of these specimens using shell morphology, radular morphology, and genetic barcoding (mitochondrial CO1 and nuclear H3). Records of occurrence for P.laevis Warén & Ponder, 1991, P.ios Warén & Bouchet, 1986, and P.pacifica Warén & Bouchet, 1986 are herein presented from the Costa Rica Margin. A critical taxonomic review of the 29 extant species within this genus was conducted and their genetic, morphological, and biogeographical distinction assessed. In this review, genetic and morphological support was found for nearly all current species delineations except for P.glabraOkutani et al., 1992, syn. nov. and P.laevis, syn. nov., which are herein synonymized to P.laevis, and for P.ios, syn. nov. and P.goniata Warén & Bouchet, 1986, syn. nov., which are synonymized to P.ios. Finally, the first species identification key for the extant species in this genus is presented. This work clarifies the taxonomy and systematics of this deep-sea gastropod genus and contributes a novel polytomous key for use in future research.

Morphometric variations of two patellid limpets between artificial breakwaters and natural reefs

Artificial shorelines often differ from natural reefs in shape, composition, and habitat complexity. They promote higher accumulation of pollutants and increased physiological stress, which lead to changes in species distributions and ecosystem functioning. This can promote trophic shifts and reduced genetic diversity of gastropod populations inhabiting artificial shorelines and might promote morphological changes, which may influence behaviour, vulnerability to predation, feeding efficiency, sex ratios, reproductive development, and overall fitness. This study explores inter- and intraspecific shell morphometric variations in Patella rustica and P. caerulea between breakwaters (ripraps) and natural reefs in three sites of Ceuta (North Africa, Spain), including a physicochemical assessment of the studied locations: shore orientation, inclination and wave exposure, and substratum nature, heterogeneity and roughness. Limpets on artificial substrata had a slightly smaller extra-visceral cavity and flattened shell profile, which suggests that the desiccation and temperature stress driven by the lithological composition and roughness of the studied substrata might have influenced the registered shell shape variation. However, the high morphometric variation registered for both species across sites and substrata suggests that limpets' morphology might be responding to a complex interaction of environmental and ecological factors rather than solely rock type. The findings of this study highlight the complex interplay between rock type and local environmental conditions in shaping patellid limpets’ shell morphology and provide insights into the adaptive mechanisms that drive shell shape variation in limpet populations in the face of coastal sprawl and anthropogenic global change.

It's time to consider the Arcellinida shell as a weapon

The shells of testate amoebae are morphologically diverse and persistent in the environment. Accordingly, the examination of the morphology and composition of shells became a standard tool in ecological, palaeoecological, and evolutionary studies. However, so far the function of the shell remains poorly understood and, although based on limited evidence, the shell was considered as a defense mechanism. Based on recent evidence, we propose that the shell of arcellinid testate amoebae is a crucial component facilitating the amoebae’s attack of large prey. Accordingly, the shell is not purely protective, but must be considered also as a weapon. This change in perspective opens up numerous new avenues in protistology and will lead to a substantial change in ecological, palaeoecological, and evolutionary research.

Unveiling the 3D structure of nova shells with MUSE: The case of RR Pic

Context. Nova eruptions occur in cataclysmic variables when enough material has been accreted onto the surface of the white dwarf primary. As a consequence, the material that has been accumulated until then is expelled into the interstellar medium, forming an expanding nova shell around the system. Understanding the physical process that shapes the morphology of nova shells is essential to fully comprehend how the ejection mechanism operates during nova eruptions. Because of its closeness and age, the nova shell around the classical nova RR Pic (Nova Pic 1925) is an ideal target for studying the evolving morphology of nova shells. Aims. The use of integral field spectroscopy (IFS) is a technique that has received little attention in the study of nova shells, despite the advantages in using it when studying the morphology and kinematics of nova shells. In this work, we present an IFS study of the RR Pic nova shell, with a particular emphasis on the extraction of the 3D morphology of the shell. Methods. The nova shell was observed by the Multi-Unit Spectroscopic Explorer (MUSE) instrument placed at the ESO-VLT. By measuring the extension of the nova shell in these new observations, and comparing it against previous measurements, we were able to determine the expansion history of the ejected material. We used this information, together with the distance to the system based on Gaia EDR3 parallaxes, and the systemic velocity of the system reported in the literature to obtain the physical 3D view of the shell. Results. The MUSE datacube confirms the presence of the nova shell in Hα, Hβ and [OIII], and very faintly in [NII]. A comparison with previous observations suggests that the shell continues in its free-expansion phase but with the different parts of the shell apparently expanding at different rates. The data analysis corroborates the previous vision that the shell is composed of an equatorial ring and polar filaments traced by Hα. At the same time, the new data also reveal that [OIII] is confined in gaps located in the tropical regions of the shell where no Hydrogen is observed. The flux measurements indicate that ~99% of the shell flux is confined to the equatorial ring, while the polar filaments show a flux asymmetry between the NE and SW filaments, with the latter being ~2.5 times brighter. We have estimated the mass of the shell to be ~5 × 10−5 M⊙. From the analysis of the 3D-extracted data, we determine that the ring structure extends ~8000 au from the central binary, and has a position angle of ~155 deg and an inclination of ~74 deg. The analysis of the equatorial ring reveals it is composed of a main ring and several small clouds, extending up to a height of ~4000 au above and below the main plane of the equatorial ring. The radial profile of the whole ring structure is reminiscent of a bow shock. Conclusions. Our data have proven the capabilities of observing nova shells using IFS, and how the nova shell around RR Pic is an interesting object of study. Further and continuous observations of the shell across the electromagnetic spectrum are required to confirm the results and ideas presented in this work.

Https://www.micropress.org/microaccess/micropaleontology/issue-404/article-2385

Ostracod crustaceans are among the most abundant microfossils in the geological record, thanks to their strongly calcified shell. Most of the fossils belong to the suborder Cytherocopina, which also has a rich diversity of living species. Unfortunately, many of the living representatives are known only by their shell morphology. Soft body always provides valuable insights into the phylogeny, and sometimes conflicts with currently accepted systematics of this group. We provide a complete description of Coquimba ishizakii Yajima 1978, collected from Jeju Island, South Korea. This is the first report on soft body morphology for the entire genus Coquimba Ohmert 1968, and the first record of this genus from Korea. Its soft body morphology is similar to other representatives of the family Hemicytheridae, where Coquimba currently belongs. After reviewing all records of C. ishizakii, we propose that several of them belong to different species, such as all those from Taiwan (modern and fossil). We also provide 18S rRNA and 28S rRNA sequences for this species, the latter being reported for the first time for the entire family Hemicytheridae.

Unusual Shell Morphologies of Responsive Amino Core‐Shell Microgels Induced by pH During Shell Synthesis

Unusual Shell Morphologies of Responsive Amino Core‐Shell Microgels Induced by pH During Shell Synthesis

Деякі пізньокрейдові аглютиновані види форамініфер Північної окраїни Донбасу

The article describes four species of agglutinated foraminifers belonging to three genera (Verneuilina, Orbignyna, and Spiroplectammina) three superfamilies (Verneuilinoidea, Ataxophragmoidea, and Spiroplectamminoidea) and two orders (Ataxophragmiida and Ammodiscida, suborder Textulariina). Benthic species of foraminifers play an important role in the stratigraphic subdivision of the Upper Cretaceous deposits of the Northern outskirts of Donbas and correlation with adjacent territories, as they make up the most part of the assemblage in the samples. For this region, the foraminifera species Verneuilina muensteri Reuss, 1854, Orbignyna variabilis (d’Orbigny, 1840), Orbignyna pinguis Woloschyna, 1961, and Spiroplectammina baudouiniana (d’Orbigny, 1840) were monographically described for the first time. For each species of foraminifers, a detailed description of shell morphology is given. According to the biozonal scale of the Upper Cretaceous deposits of the East European Platform, Verneuilina muensteri is one of the characteristic species of the Upper Turonian Gavelinella moniliformis s. l. foraminifer zone, the species Orbignyna variabilis is typical for the Upper Santonian Gavelinella stelligera zone, and the species Orbignyna pinguis is characteristic of the Upper Campanian Globorotalites emdyensis zone. The species Spiroplectammina baudouiniana is also described. The stratigraphic and lateral distribution of each species of agglutinated foraminifers is indicated, and the deposits and sections of the Northern outskirts of Donbas in which they occurred are indicated. A schematic map of the region is presented, showing the studied sections in which shells of these species were found. These species are found in the rocks of the Shyroka, Yelanchyk, Kryva Luka, Sydorove, Konoplyanivka, and Kamianyi Brid formations of the Northern outskirts of Donbas, which are represented by chalk, marls, and calcareous sandstones. The work presents images of foraminifer species taken with a scanning electron microscope JSM-6490LV (JEOL Ltd., Japan). The article deepens our knowledge of some agglutinated foraminifers from the Upper Cretaceous deposits of the Northern outskirts of Donbas, which are characteristic species of the zone, contributing to further solving the issues of stratigraphy and correlation of these deposits.

DNA barcoding indicates multiple invasions of the freshwater snail Melanoides tuberculata sensu lato in Florida.

Melanoides tuberculata sensu lato (Thiaridae) are polymorphic female-clonal snails of Asian and African origins that have invaded freshwaters worldwide, including those in Florida. Although the snails have been documented in Florida for at least 70 years, no studies have investigated whether the observed distribution is due to a single introduction or multiple independent invasions. Here, cytochrome oxidase I was used to measure genetic diversity within and among sites in Florida and compare genetic diversity between Florida and other regions of the world. We also examined the relationship between shell morphology and haplotype diversity to determine if shell morphs can serve as a proxy for haplotypes. In total, we recovered 8 haplotypes randomly distributed across populations in Florida. Phylogenetic reconstruction supported the hypothesis of multiple invasions by diverse representatives of the M. tuberculata species complex. In contrast, shell morphology was not found to be a useful phylogeographic character, with divergent haplotypes represented by similar shell forms. These results suggest that the observed invasion patterns in Florida are best explained by serial introductions, and that shell morphology cannot be used to predict haplotypes or reconstruct invasion history of Melanoides tuberculata s.l. and that extensive taxonomic revisions are needed to investigate invasion dynamics.

Comparative diversity in glochidia of Australasian freshwater mussels

Most freshwater mussels have larvae (glochidia in Unionidae, Margaritiferidae and Hyriidae) that are parasitic on fishes. This study describes and compares the diversity of glochidia among 17 species of Australasian Hyriidae. Here, scanning electron microscopy was used to illustrate shell morphology, while patterns of diversity in size, shape and morphological characteristics were analysed quantitatively and qualitatively with Principal Component, Linear Discriminant, and Multiple Correspondence Analyses to separate species with varying degrees of discrimination. Results showed shell lengths ranged from 50 to 390 μm. Shape varied, from sub-oval to sub-triangular, bilaterally symmetrical to scalene, and hook morphology varied from unicuspid, bicuspid, tricuspid or complex with varying length and structure. Unique observations of this study include the consistent variation in glochidial release mechanisms among Australian subfamilies and New Zealand genera. Hyridellini species and Echyridella aucklandica (Gray and Dieffenbach, 1843) are released either freely or as “mesoconglutinates” (presumed brood lures), whereas Velesunioninae and Echyridella menziesii (Gray and Dieffenbach, 1843) release glochidia in “amorphous mucous conglutinates”. Hyridellini predominantly occur within perennially flowing rivers of coastal south-eastern Australia with generally low turbidity, whereas the Velesunioninae occur more typically in slower flowing, intermittent waters, many prone to extended periods of high turbidity. Thus, where Hyridellini occur, mesoconglutinates as visual brood lures may be a more efficient mechanism for infesting host fishes than the passive infestation strategy typical of velesunionine species frequenting more turbid waters. Finally, this study presents systematic descriptions of glochidia and a provisional key for identification of Australasian hyriid glochidia, making an important contribution to the current understanding of taxonomy and life history traits, both critical for hyriid conservation.