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Correct identification of species is fundamentally important, but field identification can be misleading in many taxa, requiring genetic comparisons to confirm identity of specimens. Recent genetic studies revealed that the giant clam Tridacna noae (Roding, 1798), previously confused morphologically with Tridacna maxima (Roding, 1798), is widespread in the Indo-West Pacific, including a subtidal site at Ningaloo Reef, Western Australia. We examined molecular and morphological variation of Tridacna from four intertidal populations at Ningaloo Reef to determine their identity and to test whether morphology is useful for distinguishing the two species in this region. DNA sequences of clams identified all individuals as T. noae, indicating that T. maxima is rare, if it occurs at all, at Ningaloo Reef. Morphological traits that distinguish the two species in the Western Pacific are highly variable at Ningaloo, indicating the need for local genetic corroboration for correct identification.

Imposex is a reproductive abnormality in which female snails begin to transform to males, but do not become functional. It was caused by tributyltin (TBT) used as an antifoulant in boat paints. Imposex was first recorded marine snails (Conus) (Mollusca: Caenogastropoda) at Rottnest Island, Western Australia, in January 1991, where 88% of individuals at the west end were affected. Most were at moderate Stages 3 and 4 on a scale of 0 (no affect) to 6 (death). TBT was banned on boats25m long in late 1991 in WA. In 1996, imposex had declined to 69% of females with Stages 3 and 4 still the most common. By 2007 only 35% of females exhibited imposex; Stage 3 was the highest level recorded. TBT was below detection limits. TBT was banned on vessels25m in September 2013. In February 2017 only 4% of Conus had imposex, at Stage 1.

Despite the many functions that mobile invertebrates serve in marine ecosystems, these assemblages remain relatively understudied. This study utilized artificial settling surfaces to determine how mobile invertebrate assemblages vary along a latitudinal gradient encompassing ~ 1100 km of the Western Australian (WA) coast. We examined the structure of both ‘whole assemblages’ at a coarse taxonomic level and a subset of the assemblage (crabs) at the species level, across six locations and over two sampling periods. Assemblage structure differed significantly between locations and a moderately strong correlation with latitude was detected. More evident, was distinct partitioning between assemblages at ‘warm-water’ locations (23–24.5°S) and ‘temperate’ locations (28–33°S). This division in assemblage structure was consistent between sampling periods and taxonomic resolutions and corresponds to shifts in dominant biogenic habitat along the coast (coral vs. macrophyte). The abundances of some of the dominant crab species suggested discrete, unimodal distribution relationships with latitude/temperature, a pattern observed previously for macroalgae and fish in WA. The regional-scale patterns of mobile invertebrate assemblage structure presented here will contribute to forming a benchmark against which to detect future ecological change.

Effective management of rocky intertidal reefs requires an understanding of spatial variation in species composition and abundance, and the identification of high biodiversity areas. This study identified patterns of invertebrate biodiversity on intertidal reefs of differing underlying structure within Ngari Capes Marine Park, south-west Western Australia. Intertidal reef surveys were conducted at 12 limestone and 9 granite sites throughout the park. Geology was a significant indicator of variation in percentage cover of substrate and invertebrate composition, which covaried with rugosity and complexity. Limestone reefs were characterised by a combination of high and low branching algae and a sand–turf matrix, whereas granite reefs consisted of bare rock. A total of 15772 individual invertebrates representing 10 phyla, 16 classes, 60 families and 121 species was recorded. A high abundance of dove (Family Columbellidae) and jewel top snails (Family Trochidae) characterised limestone reefs, whereas an assortment of limpets and chitons characterised granite reefs. Granite reefs contained more species (92v. 63) and a higher mean (±s.d.) number of individuals (119±58v. 42±79m–2) than did limestone reefs. These findings emphasise the effect of underlying geology on the distribution of intertidal invertebrates and the need for management programs to accommodate different habitat types to effectively conserve biodiversity.

Numerous anthropogenic activities can significantly reduce the amount of light reach- ing seagrass habitats. Typically these result in morphological and physiological changes to the plant and associated algal epiphytes. However, the flow-on effects to seagrass-dependent fauna induced by these disturbances has yet to be examined. This study investigated the effects of different light reduction intensity (high: ~92% reduction; moderate: ~84% reduction), duration (3, 6 and 9 mo) and timing (post-winter and post-summer) on the density and biomass of macroinvertebrate epifauna within an Amphibolis griffithii seagrass ecosystem (Western Australia). There were generally lower epifauna densities and biomass within shaded seagrass plots. When moderate intensity shading was imposed at the end of winter, total density in unshaded controls was 31% lower at 3 mo, and 78% lower at 9 mo. When high intensity shading was imposed, total density was 38% lower than in con- trols at 3 mo, and 89% lower by 9 mo. Although densities varied, similar magnitudes of decline occurred in post-summer shaded treatments. Taxa-specific responses were variable in terms of time, rapidity and magnitude of response. Amphipod, isopod and gastropod densities generally declined in response to shading. Bivalve densities declined with shading post-summer, but not post-winter. Ostracod densities had an inconsistent response to moderate shading. Changes in epifaunal density were largely associated with declines in algal biomass, leaf variables and stem biomass, indicating food and habitat limitations. It is likely that the significant declines in epifauna observed in this experiment would have flow-on consequences to higher trophic levels.

In south-western Australia, the isopod Limnoria agrostisa commonly burrows into leaf clusters and immature shoots of Amphibolis griffithii. The isopod also burrows into the sheath and rhizomes of Posidonia species. In A. griffithii, the isopod consumes new tissue within the sheath, damaging or destroying the meristem. This results in malformation of new leaves or destruction of whole leaf clusters with the potential to reduce the photosynthetic area of a shoot. The isopod has been found in all but one meadow of A. griffithii examined over 1,000 km of the Western Australian coastline. It was present throughout the year and showed little variation in abundance. Young were produced year round, but were more abundant in the summer months. Females, 3.5 mm in length or larger, produced 2–5 young that were brooded within the leaf cluster or base of an immature shoot. Within a meadow, 40–70% of shoots and 10–20% of leaf clusters were damaged by isopods. Seasonal trends were not consistent, but damage appeared to be higher in summer when isopod abundance was higher. Approximately 40% of clusters were destroyed by isopod damage. Isopods attack shoots of all ages, but damage was often located on apical clusters. There was no evidence that isopod damage initiated branching or leaf cluster formation. Estimations of clusters damaged or destroyed may be conservative, as only those clusters remaining on a shoot could be counted, and cluster loss could not be quantified. Examination of defoliated stems on upright shoots and horizontal rhizomes indicated that many were destroyed by isopods. The effect of L. agrostisa although substantial appears to be a feature of healthy seagrasses throughout southern Australia.

Fertilised eggs, stage one and stage two juveniles of the smooth marron, Cherax cainii, are attached to the pleopods of the gravid female via specialised structures. The eggs are fixed to the maternal pleopods by egg stalks, whereas stage one and stage two juveniles remain attached by recurved spines on the dactyls of their fourth and fifth pereopods. Crayfish of the third juvenile stage are independent of the mother and receive no maternal care; their dactyl spines are straight and cannot grasp the mother's pleopods; the female displays agonistic behaviour toward her young commencing with stage III instars. We suggest that eggs and the first two juvenile stages attached to the mother would experience reduced levels of predation and be secured against strong river flow. We conclude by reviewing, briefly, the potential fitness costs and benefits of maternal care, to the mother and young of freshwater crayfish, from a life-history perspective.

Potential food sources and dominant invertebrates and fishes were collected for the examination of variability in 13 C/ 12 C and 15 N/ 14 N to determine the sources of carbon available to consumers within a Western Australian Posidonia sinuosa -dominated seagrass bed. Autotrophs showed a wide distribution of δ 13 C values, with P. sinuosa at −11.3 ± 0.8‰ and macroalgae ranging from −16.6 to −31.7‰. This variation allowed us to successfully identify macroalgae as the main contributor of carbon to the trophic structure, although no distinction could be made between epiphytic macroalgae on seagrass, or allochthonous macroalgal sources. The range in δ 15 N ratios among potential food items at the trophic base was too small to make it useful as tracer of nitrogen flow pathways, but it consistently increased from macrophytes and detritus (4.1–6.8‰), to invertebrates (5.7–7.4‰) located near the middle of the food web, to fishes (8.3–11.9‰), with piscivorous species such as Leviprora inops generally having a higher 15 N. δ 13 C of seston (−12.8‰) and sedimentary organic matter (−8.7‰) indicate that seagrass material is the main contributor to these two carbon pools, and that very little of it contributes to animal biomass.

In the last decade, an increasing number of mesofaunal crustaceans and polychaetes have been reported to bore into seagrass tissues. Crustacean borers have been found in seagrasses from different oceans (Indo-West Pacific, Mediterranean, and Caribbean), but until present, boring polychaetes had only been registered in the Mediterranean. Here, a new record of polychaete borers within sheaths of the seagrass Thalassia testudinum (Banks ex Konig) off the Mexican Caribbean coast (Puerto Morelos) is reported. The polychaetes were found in sheaths of plants collected at two stations in a shallow meadow (3–4 m depth), and except for slight morphological differences, were similar to Lysidice ninetta Audouin and Milne Edwards, Lysidice collaris Grube, and Nematonereis unicornis Grube; taxa previously recorded in sheaths of the Mediterranean seagrass Posidonia oceanica (L.) Delile. A synthesis of present knowledge of fauna burrowing into seagrass tissues, suggests the existence of specific associations between particular seagrasses and specialized members of crustaceans (orders Isopoda and Tanaidacea) or polychaetes (family: Eunicidae). The boring crustaceans can be classified as mesoherbivores because they consume the living tissues they burrow into. Each species bores into specific tissues which are either leaf blades, leaf sheaths, rhizomes or seeds. The polychaetes, in contrast, bore into the dead sheath tissues which remain attached to the vertical rhizomes after abscission of the green blades, and can thus considered to be detritivores.

Isopods of the genus Lynseia have been found burrowing (leaf mining) in meadow forming seagrasses (Posidonia) from Western Australia. These small (1.5–1.8 mm) isopods burrow beneath the epidermis consuming the mesophyll, forming a linear mine of similar width to the isopod along the leaf lamina. At Rottnest Island in January 1991, 75% of Posidonia australis Hook. f. and 66% of Posidonia sinuosa Cambridge and Kuo leaves were burrowed by isopods. Isopods were found in leaves of all sizes, but number of burrows, number of isopods and the length of burrows increased in older leaves. In P. australis, there were 3.15 ± 0.1 burrows and 2.6 ± 0.1 isopods per burrowed leaf, in P. sinuosa there were 2.9 ± 0.1 burrows and 2.48 ± 0.2 isopods per burrowed leaf. Isopods were mobile, vacating older burrows and forming new ones. Male and female isopods were found in pairs within burrows and young isopods were then brooded within the burrows, forming new branches from the parent burrow. Within monospecific stands of P. australis and P. sinuosa there were 2950 and 2280 isopods m−2 respectively. Mean length of individual burrows was 22 mm in P. australis and 28 mm in P. sinuosa. Total burrow length per leaf (mean ± SE) was 69.6 ± 3.6 mm in P. australis and 81.7 ± 4.7 mm in P. sinuosa. The consumption of leaf tissues and the resulting lines of weakness along burrow lines may have negative effects on the seagrass. Burrows facilitate entry of water, bacteria and fungi to the blade, leading to localised tissue death. Epiphytes may proliferate along burrow lines, owing to surface roughness or solute loss associated with the burrow. Burrows also split and increase fragmentation of leaves in storm events. Loss of photosynthetic area due to epiphytic growth and fragmentation of the leaves may reduce the growth of Posidonia. These potential effects of lynseid seagrass leaf miners may be important if the seagrass meadow was already under stress.

Understanding variability of recruitment and mortality is essential for attempts to conserve populations or assessing changes resulting from perceived disturbances. In the absence of long-term studies, we examined population density and size-frequency distributions of the small giant clam, Tridacna maxima, at 20 sites in Ningaloo Marine Park, Western Australia, where the clams are abundant on discontinuous, intertidal rocky platforms attached to the shoreline. Density ranged over two orders of magnitude (0.04–8.27 m–2), and size ranged from 1.5 to 31.0 cm. The shapes of the size-frequency distributions varied substantially, indicating variability in recruitment and mortality, including failures of cohorts to recruit and catastrophic events of mortality. Consistency of recruitment, as indexed by the coefficient of variation of the size-frequency distribution, was greater towards the north of the Park, on intertidal platforms with greater complexity across their widths, and with smoother surfaces in the part of the platform occupied by the clams. The average turnover time was estimated at 5.4 years, giving a median age of 13 years. However, variation among sites was large, highlighting the importance of variability of the dynamics of local populations and the need for long-term studies to understand any particular population.

Isopods (Limnoria simulata, Limnoriidae, Flabellifera) burrowing in the turtle grass Thalassia testudinum (Banks ex König) are reported from Puerto Morelos reef lagoon, Mexican Caribbean. Isopods (maximum length 2.0–4 mm) burrowed in sheaths of outer foliar leaves of shoots; they bored through the middle leaf tissue and epidermis of the inner face of the sheath, forming canal systems ~20–50 mm long. Traces of isopod burrowing showed as linear arrays of holes in seagrass blades, which could be observed in the field. Isopods used the burrows for reproduction, and on many occasions two adults were found together in one canal system. Frequency of infestation in T. testudinum varied throughout the reef lagoon and was highest in a shallow protected coastal zone, where ~50% of the shoots had isopod burrows in their sheaths. Infestation was lower (20–30% shoots with damaged sheaths) in mid-lagoon beds, and minimal in wave-exposed back-reef areas. The distribution of infested shoots was patchy. Where the degree of infestation was high, T. testudinum shoots showed reduced blade growth. Resumen. Se registra la presencia de isópodos (Limnoria simulata; Flabellifera : Limnoriidae) que excavan el pasto marino Thalassia testudinum (Banks ex König) en la laguna arrecifal de Puerto Morelos, en el Caribe mexicano. Los isópodos de Puerto Morelos (longitud máxima: 2.0–4.0 mm) excavan las vainas de las hojas exteriores de los grupos foliares (haces), a través del tejido medular y la epidermis del lado interior de la vaina, formando sistemas de canales de 20 a 50 mm de longitud. En el campo, los rastros de las excavaciones aparecen como arreglos lineales de agujeros en las láminas del pasto. Los isópodos utilizan las excavaciones para reproducirse, y en varias ocasiones se encontraron dos adultos juntos en un sistema de canales. La frecuencia de infestación en T. testudinum varió dependiendo del lugar en la laguna, siendo mayor en una zona costera protegida, donde 50% de los haces contenían isópodos. Los valores intermedios de infestación (20–30% de los haces) se encontraron en la zona media de la laguna, mientras que la infestación fue mínima en áreas cercanas al arrecife coralino, expuestas al oleaje. La distribución de los haces infestados de isópodos fue desigual, y en parches con altos niveles de infestación T. testudinum mostró un crecimiento reducido.

A new bivalve species, Tellina (Tellinides) cockburnensis, is described from inshore localities in Western Australia between Warnbro Sound and Bernier Island. Fossil records are from Quaternary deposits between Kalbarri and Albany.