Invertebrate Biology最新文献

The crab Trapezia bidentata is a conspicuous crustacean characterized as an obligate symbiont with branching corals, such as species of Pocillopora. These crustaceans have been identified as strict corallivores with a feeding dependency on the mucus excreted by adult colonies in the genus Pocillopora. However, like other crustaceans, individuals of T. bidentata have a nutritional plasticity that has not been described. We used an integrative approach, including traditional taxonomy and high-throughput sequencing of hypervariable region V9 of the 18S rRNA gene, to describe the mouthparts and the diet of individuals of Trapezia bidentata associated with adult colonies of Pocillopora verrucosa. The presence of setae on the ambulatory dactylus and maxillipeds, forming food brushes and combs, was evident. Sequencing and analyses of the intestinal content of the crustaceans found evidence of 18 phyla, mostly represented by Brachiopoda (28.1%), Arthropoda (31.7%), and Cnidaria (21.1%), but also small contributions (≤2%) of other animal groups such as Mollusca, Annelida, and Tunicata. In addition, a few traces (≤0.5%) of algae and fungi were identified. The feeding structures and intestinal content showed that individuals of T. bidentata are omnivorous and behave as suspension feeders and scrapers, obtaining nourishment from tissues transported in the water column and in the mucus and tissue of P. verrucosa. The results provide a clearer characterization of the role of T. bidentata, which is a crucial guard crustacean associated with P. verrucosa. We found both corallivorous and suspension-feeding habits, which demonstrates feeding plasticity, a positive characteristic for the survival of the species.

Populations of two cladoceran species, Alona quadrangularis and Scapholeberis mucronata, were collected from a pond in Puyallup, Washington, and reared under controlled laboratory conditions. Life tables were developed for each species under the same environmental conditions and feeding regimen to develop basic demographic data. We also compared the major demographic parameters of these two wild species with those of several cladoceran species that are commonly used in laboratory research, Daphnia pulex, D. magna, and Ceriodaphnia dubia. Compared to A. quadrangularis, S. mucronata had a much higher net reproductive rate (R₀), a longer generation time (T), but a similar intrinsic rate of increase (r_m), similar finite rate of increase, similar doubling time (DT), and a lower birth rate (b). Both wild species had lower R₀, shorter T, and higher b than in D. pulex, D. magna, and C. dubia. Results of this study showed that demographic rates differed between A. quadrangularis and S. mucronata, and differed from those reported for the other three laboratory species. These results suggest that data developed for commonly used cladoceran species in the laboratory should not be used to make generalizations about effects on wild species.

Reproduction, embryological development, and settlement of corals are critical for survival of coral reefs through larval propagation. Yet, for many species of corals, a basic understanding of the early life-history stages is lacking. In this study, we report our observations for ex situ reproduction in the massive reef-building coral Porites cf. P. lobata across 2 years. Spawning occurred in April and May, on the first day after the full moon with at least 2 h of darkness between sunset and moonrise, on a rising tide. Only a small proportion of corals observed had mature gametes or spawned (14–35%). Eggs were 185–311 μm in diameter, spherical, homogenous, and provisioned with 95–155 algal cells (family Symbiodiniaceae). Males spawned before females, and ex situ fertilization rates were high for the first 2 h after egg release. Larvae were elliptical, ~300 μm long, and symbiotic. Just 2 days after fertilization, many larvae swam near the bottom of culture dishes and were competent to settle. Settlers began calcification 2 days after metamorphosis, and tentacles were developed 10 days after attachment. Our observations contrast with previous studies by suggesting an abbreviated pelagic larval period in Porites cf. P. lobata, which could lead to the isolation of some populations. The high thermal tolerance and broad geographic range of Porites cf. P. lobata suggest that this species could locally adapt to a wide range of environmental conditions, especially if larvae are locally retained. The results of this study can inform future work on reproduction, larval biology, dispersal, and recruitment in Porites cf. P. lobata, which could have an ecological advantage over less resilient coral species under future climate change.

Holoplanktonic organisms are thought to have enormous populations sizes, expansive geographic ranges, and low species diversity. Previous work suggests that pelagic gastropods are no exception to this generalization. However, most of these data are derived from temperate species, whereas the bulk of pteropod diversity occurs in the tropics. Here, we present DNA barcode data for COI focused on the under-studied limacinoid, gymnosome, and pseudothecosome pteropods collected from the coastal waters of Panama. We applied four molecular species delimitation approaches to determine the number of operational taxonomic units (OTUs) identifiable from our sequences and all data available from Barcode of Life Database (BOLD) and GenBank and compared these to the Barcode Index Number generated by the BOLD. Assemble Species by Automatic Partitioning (ASAP), Poisson Tree Processes (PTP), Bayesian Poisson Tree Processes (bPTP), and Generalized Mixed Yule Coalescent (GMYC) methods generally gave congruent results and suggest that pteropod diversity in the tropics is significantly underrepresented both in DNA sequence databases and in the number of named OTUs. Of 42 specimens collected and sequenced, we recovered 16 OTUs, only one of which belonged to an OTU already represented in sequence databases. Neighbor-joining trees including the previously published sequences show that in all three groups morphospecies can include genetically divergent lineages. Many very divergent (>15% from nearest neighbor) taxa are also still represented by only a single sequence, suggesting that there is a large amount of cryptic or pseudo-cryptic diversity still to be described. To aid this future endeavor, we include some preliminary 16S data derived from new pteropod-specific primers.

Suspension-feeding bivalve molluscs are dominant benthic fauna in many near-shore environments, with phytoplankton often being their main prey type. Feeding, which involves hydrosol filtration and mucociliary processes to capture particles and process them for digestion, occurs at low Reynolds numbers. Changes in water temperature have been shown to affect feeding processes of bivalves as a result of altered physiological processes or temperature-dependent changes in kinematic viscosity of water. Most studies, however, have focused on feeding rates and have manipulated temperature under laboratory conditions. In this study, experiments were conducted using ambient seawater and acclimatized blue mussels, Mytilus edulis, to examine particle capture efficiency over a 1-year period. During this period, water temperature decreased from ~18°C to 5°C with a concomitant increase in viscosity of ~41%. The capture of a wide variety of bacteria and phytoeukaryotes (0.8–8 μm), as well as two sizes of polystyrene microspheres (1 and 6 μm), was quantified to calculate capture efficiency. Data demonstrate that temperature, and the concomitant change in water viscosity, had no significant effect on capture efficiency. Cyanobacteria were captured at significantly higher rates than other bacteria of similar size. These results suggest that the laterofrontal cirri of blue mussels act as paddles rather than sieves because capture efficiency was constant over a range of viscosities and Reynolds numbers. Additionally, the efficient capture of some bacteria and smaller phytoeukaryotes by the mussels suggests that these plankters could play a larger role in the diet of M. edulis than previously considered. The ecological impact of these findings, especially regarding differences in capture efficiency of different bacterial cells, warrants further study.

Although farmed shrimp contribute to global food security and foreign exchange, the development of genomic resources such as single nucleotide polymorphisms for these shrimp is at slow pace. Public genomic resources like Genbank and Ensembl do not host polymorphism data for shrimp. Therefore, through analysis of the short RNA-sequence reads generated on pooled-individual samples, using the latest bioinformatics tools, this study documents data of single nucleotide polymorphisms in two shrimp species, Penaeus vannamei and Penaeus indicus, and presents these data in a searchable user-friendly webtool, the dbVAST. The webtool also hosts the information about the possible effects that the variations could have on the functioning of the coded protein. This is the first open-access SNP database of shrimp intended to benefit researchers and academicians by showcasing variations in shrimp transcripts.

Native freshwater mussel (Unionidae) mortality events have been occurring with increased frequency in recent decades, with few investigations into potential etiological agents. In the western United States, no surveys have been published regarding the bacteria associated with unionid mussels. Herein, we examine locations of known mussel mortality events in the Chehalis River (Washington), in the Crooked River (Oregon), and Owyhee River (Oregon). Mussel populations considered healthy were sampled in the Skookumchuck River (Washington) for comparison. A variety of bacteria were isolated from these populations, and most notably, Acinetobacter spp. were identified from 82% of moribund individuals of Gonidea angulata in the Owyhee River. Future work evaluating whether Acinetobacter spp. are pathogenic to freshwater mussels could be valuable in unraveling the factors associated with these enigmatic mortality events.

Stable temperature, humidity, and oligotrophy may be essential in microhabitat selection, shaping niche overlap and species coexistence within cave ecosystems. To explore this hypothesis, we assessed the distribution and microhabitat preferences of four non-obligate cave-dwelling spiders: Loxosceles anomala, Scytodes itapevi, Philoponella vittata, and the exotic Oecobius navus. Using 1-m² quadrats, we surveyed spider distribution and abundance in a limestone cave, considering environmental conditions and prey availability during wet and dry periods. Significant differences were observed between moist and dry periods regarding light intensity, wind speed, air temperature and moisture, potential prey, and the abundance of L. anomala. The exotic spider O. navus was more specialist, preferred brighter habitats, and showed lower niche overlap. Conversely, the three native species displayed greater niche overlap and preferred darker and more humid environments. Spatial disparities, rather than temporal variation, in species distribution underscored the influence of cave habitat conditions on species segregation. Furthermore, our findings highlighted the limited ability of the non-native O. navus to occupy more illuminated cave areas, thereby potentially safeguarding these habitats against biological invasion by this species.

We studied the development of sporocysts of the trematode Leucochloridium paradoxum. For this purpose, their life cycle was traced experimentally. Eggs obtained from adult trematodes raised in chicks (Gallus gallus domesticus) were used to infect snails (Succinea putris, laboratory strain). Histological studies of sporocysts were conducted for 95 days after exposure. During this time, the embryos of sporocysts developed into a small stolon filled with numerous metacercarial embryos. We found that miracidia hatched in the stomach and in the proximal part of the snail's midgut. After the larvae migrated into the area of the hepatopancreas, their body was destroyed, and germinal cells were released. They cleaved to form the embryos of sporocysts, in which only metacercarial embryos developed. Our study showed that these trematodes lack the parasitic phase of the mother sporocyst and have only one generation of parthenitae, the daughter sporocysts.

Comma shrimp, or cumaceans, are diverse benthic crustaceans, yet they are one of the groups with the poorest fossil record, hindering our understanding of the evolution of the group in deep time. Here, we describe a new species of fossil comma shrimp, Makrokylindrus itoi sp. nov., from the Plio-Pleistocene of Japan. The singular fossil is exceptionally preserved, including details of the carapace, cuticle, and some appendages, and it represents the first known fossil of the family Diastylidae and only the fourth fossil crown group cumacean known to date. We suggest that the scarce and sparsely known fossil record of cumaceans likely reflects a lack of recognition due to their small size and unfamiliar anatomy, making fossil cumaceans easy to misidentify, be confused with crustacean larvae of unknown affinities, or be interpreted as fragments of other crustaceans (taxonomic bias), rather than a lack of fossilization potential (taphonomic bias).