Invertebrate Biology最新文献

Hemocytes are circulating blood cells that play a crucial function in amphipods and other crustacean immune systems. The hemocytes of the marine tropical amphipod Parhyale hawaiensis have been used for the evaluation of DNA damage and micronuclei, but they have not been characterized in the scientific literature. The aim of this study was to describe the hemolymph cells of P. hawaiensis and study their phagocytotic activity. Basic dyes were used to differentiate the cell types and the presence of lipids. The total hemocyte counts (THCs) and the proportion and sizes of the hemocyte types were determined. Hemolymph was exposed to Escherichia coli for verification of the presence of phagocytosis. Three cell types, all containing lipids, were identified in P. hawaiensis: granulocytes (oval shape, 13.4 × 7.6 μm), semi-granulocytes (oval shape, 14.1 × 7.2 μm), and hyalinocytes (round shape, 9.6 × 7.2 μm). Those three cell types were found in different percentages in males (64.8%, 31.1%, and 4.2%) and females (70.1%, 28.2%, and 1.7%). THCs for males were 9007 ± 3800 cells per individual and 4695 ± 1892 cells per individual for females. The cells of E. coli were phagocytized by the hemocytes. Our findings increased the knowledge of hemocytes in P. hawaiensis and is a step forward in using hemocyte-based immune responses as an endpoint in ecotoxicology.

Ocean acidification (OA) is predicted to result in reduced survival, growth, reproduction, and overall biodiversity of marine invertebrates, and yet we lack information about the response to OA of some major groups of marine organisms. In particular, we know relatively little about how OA will impact temperate sponges, which will experience more extreme low pH conditions than tropical species. In this study, we quantified OA-induced changes in early life history patterns (larval mortality and condition, settlement rate, recruit survival, and size) in the non-calcifying breadcrumb sponge Halichondria panicea collected from a temperate intertidal site in the California Current Large Marine Ecosystem. Sponge larvae were exposed to OA conditions for 15 days, and early life history patterns were observed. Compared with baseline (“present”) conditions, larval mortality and settlement rates increased in the acidified treatment (“future”). This effect was restricted to larval stages; treatment had no effect on the growth and survival of recruits. This study is significant in that it shows that H. panicea may be particularly vulnerable to changes in ocean pH during the larval stage, which could ultimately reduce total sponge abundance by diminishing the number of larvae that survive to settlement.

Temperature is one of the environmental factors affecting the physiological activities of aquatic animals. This study explored the gene expression and regulation mechanism in the gill tissues of the scallop Mizuhopecten yessoensis under the stress of high temperature fluctuations. We designed a high temperature fluctuation experiment, in which the water temperature was raised from 20°C to 23°C and 26°C and then decreased from 26°C to 23°C and 20°C, with a rate of heating and cooling of 0.5°C/h. The experiment consisted of four cycles and lasted for 7.5 days. When the target temperature was reached and the next temperature increase or decrease began, the gills of scallops were collected to measure immune enzyme activities and for transcriptome analysis. Immunological results showed significant differences in enzyme activities of catalase, superoxide dismutase, total antioxidant capacity, and lysozyme in scallop gills at 20°C on the first day and 26°C on the fifth day. Therefore, we analyzed gene expression from gill samples from these two time points using transcriptomics. We referred to samples from these time points as the normal temperature group (NT) and high temperature group (HT). Transcriptome results indicated that 347 differentially expressed genes (DEGs) were found in HT versus NT. Through gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, we found that these DEGs were mainly involved in metabolic pathways and protein synthesis pathways and had significant effects on oxidative stress, apoptosis, body metabolism, and protein folding in M. yessoensis. We selected 62 DEGs related to heat shock, immunity, and metabolism, including 47 upregulated and 15 downregulated DEGs. In a subset of these genes, quantitative real-time PCR (qRT-PCR) analysis showed similar expression (R² = 0.81), thus validating the transcriptome data. Our results provide a theoretical basis for further analysis of the response mechanism in M. yessoensis to high temperature stress and for the development of molecular breeding technology for high temperature tolerance.

The leeches Whitmania pigra and Hirudo nipponia live in similar environments but have different feeding habits. At present, there are few studies of the foraging mechanism of leeches with different feeding habits. In this study, we first used maze tests to show that these two species of leeches could locate and distinguish their prey through chemosensory activity without mechanical stimulation. However, the two leech species have different foraging behaviors: Individuals of W. pigra move slowly and repeatedly adjust direction through probing and crawling to detect the location of prey (snails), whereas individuals of H. nipponia move quickly, and after determining the location of food (porcine blood), they quickly swim or crawl to the vicinity of their prey. Scanning electron microscopy (SEM) revealed that there are two types of sensory cilia and pore structures related to mucus secretion in the heads of both leeches. There are two differently sized types of chemoreceptors on the dorsal lip in W. pigra, which may have different functions during foraging, whereas in H. nipponia there is only one type of chemoreceptor, which is small. We detected the chemical components in the natural food of these two leech species by UHPLC–MS. There were 934 metabolites in the body fluid of snails and 751 metabolites in porcine serum; five metabolites unique to the body fluid of snails and to porcine serum were screened as candidate feeding attractants. Of these metabolites, betaine and arginine effectively attracted individuals of W. pigra and H. nipponia, respectively. In summary, leeches with different feeding habits use chemoreceptors to sense external chemical signals when foraging, and there are significant differences between species in foraging behavior, chemoreceptors, and attractants.

We found two functional populations of hemocytes in the hemolymph of the pulmonate snail Planorbarius corneus: hyalinocytes and granulocytes. The hyalinocytes were much more numerous than granulocytes. Each population was subdivided into subpopulations based on morphological and functional characteristics. The hyalinocyte population was represented by two subpopulations differing in size, granularity, and ability to form pseudopodia. In snails infected with the trematodes Plagiorchis sp., the cellular composition of the hemolymph changes, with hemocytes being mostly represented by granulocytes. This phenomenon is associated with the fact that granulocytes form a hemocytic paletot on the surface of sporocysts of Plagiorchis sp. It is suggested that pulmonate molluscs have one lineage of hemolymph cells. Hematopoietic stem cells can divide, ensuring multiplication of prohemocytes. The latter differentiate into hyalinocytes, which, in turn, differentiate into granulocytes.

Spiders are one of the most dominant predators in terrestrial ecosystems. Although cues triggering predatory behavior in web-building and wandering spiders are well investigated, studies concerning burrowing species, the most ancestral group of spiders, are relatively limited. To clarify critical cues affecting the predatory behavior in burrowing species, we conducted vibration-reducing experiments with the trapdoor spider Latouchia typica (Araneae: Halonoproctidae) and nymphs of the speckled cockroach, Nauphoeta cinerea (Blattodea: Blaberidae), as prey. Spiders achieved a high success rate of prey capture even when blinded (with paint on the eyes). However, the use of a rubber mat to reduce vibrations significantly decreased predation success rate. In addition, the presence or absence of the blindfold did not affect the predation rates under the reducing vibration condition. These results indicate that substrate vibrations emitted from prey are critically important to trigger the predatory behavior in L. typica, but visual and chemical stimuli are not used even in the case when vibration cues are unavailable. This is the first study to use vibration-reducing experiments to experimentally demonstrate the critical cues for predation in trapdoor spiders.

Environmental factors are constantly changing in the intertidal region. Consequently, the various benthic organisms that densely colonize this ocean area had to adapt to these constant changes. Reproductive strategy might be considered one of these adaptations. However, knowledge about this aspect of the biology of marine invertebrates is still contentious for some groups, especially with regard to sponges (Porifera). Here, we investigated the effects of different environmental factors on the timing and effort of sexual and asexual reproduction in Cinachyrella apion and Tethya maza, two oviparous demosponges in Salvador, Bahia, Brazil. We analyzed the influence of humidity, atmospheric temperature, seawater temperature, photoperiod, rainfall, height of low tides, and chlorophyll-a concentration on the density and size of oocytes and buds of these sponges. Both species reproduced aperiodically. Cinachyrella apion had a maximum 2.8 ± 4.04 oocytes/mm² and 0.73 ± 0.15 buds/mm², whereas T. maza had a maximum 6.0 ± 12.21 oocytes/mm² and 0.31 ± 0.13 buds/mm². The density of oocytes in C. apion was positively influenced by chlorophyll-a concentration, whereas that of T. maza was negatively modulated by relative humidity. We did not observe any relationship between the environmental factors and bud density in C. apion, but bud density variation in T. maza was positively related to chlorophyll-a concentration and to seawater temperature. It seems that individuals of both species alternated between the production of sexual and asexual propagules, suggesting a trade-off between reproductive modes. Therefore, asexual and sexual reproduction seems to impact population growth and reproduction of both species, likely contributing to the recruitment of new sponges. In tropical intertidal regions, multiple environmental factors seem to contribute more to determining the quantity of sexual and asexual reproductive elements rather than the species' reproductive period.

In insects, the detection of mechanical stimuli from body movements, airborne sound, substrate vibration, medium flow, or gravity by mechanosensory organs plays an important role. These mechanosenory organs can have complex morphologies with numerous sensilla, and the functional morphology with specific attachments of the sensory neurons to surrounding tissues and structures determines the stimulation. In stick insects, the subgenual organ complex in the tibia of all legs is an elaborate system of two chordotonal organs, which respond to substrate vibrations, and associated tibial campaniform sensilla, which respond to cuticular strain. One chordotonal organ, the distal organ, is characterized by a linear set of sensilla. This distal organ has not been studied for its physiological characteristics in detail, but the attachment or mechanical coupling is functionally important. Here we characterize two aspects of attachment or mechanical coupling of the distal organ: At the dorsal side, the organ is connected to the inner side of the dorsal cuticle by connective tissue, which is shown to also contain the axons of campaniform sensilla. At the proximal end, a fine membrane runs to the adjacent chordotonal organ, the subgenual organ. This membrane spans the tibia in transverse direction. It does not contain neuronal elements, but as a connection between the subgenual and the distal organ, it may influence the mechanosensory activity of these organs. Such a connection is not present in other insects such as locusts or cockroaches and could affect the sensory function in stick insects (e.g., in vibration detection by the subgenual organ) or even couple the two organs, resulting in similar mechanical responses.

As in lamellibranch bivalves, individuals of the common Atlantic slippersnail Crepidula fornicata beat cilia on their gill filaments to produce a suspension-feeding current. Having only one shell and no siphons with which to direct water flow, however, individuals of C. fornicata must adhere to a solid substrate to facilitate normal feeding. Thus, what hydrodynamic role does substrate attachment play in producing, regulating, and directing the suspension-feeding current for this species? Here, a combined particle image velocimetry and computational fluid dynamics study was conducted to address this question. Three findings were obtained: (1) Juveniles of C. fornicata (shell length 6.0–10.6 mm) whose foot was attached to a solid surface generated a strong, fan-like exhalant current and an almost equally strong, convergent inhalant current, both being spatially well extended; (2) juveniles of C. fornicata that were prevented from adhering to any surface also generated a strong, fan-like exhalant current but a much weaker and spatially limited inhalant current; and (3) whether or not they were attached to a solid surface, juveniles of C. fornicata had almost the same performance or system characteristics of the ciliary water pump, including the relationship between flow pressure rise Δp across the ciliary zone and volume flow rate Q, pump resistance Δp/Q, and pressure coefficient for laminar flow C_p,l. These results indicate that the primary hydrodynamic effect of substrate attachment in C. fornicata is to form a complete inhalant chamber with a narrowed opening, such that negative flow pressure develops in the inhalant chamber, and a strong, convergent, spatially well-extended inhalant current is generated to effectively bring in food particles from farther distances and to reduce refiltration of the outflowing water. Finally, ecological trade-offs are discussed regarding the two distinct shell configuration strategies: (1) that of the single-shelled C. fornicata, with only a naturally formed exhalant chamber and opening but not a morphologically defined inhalant chamber and opening, and (2) that of two-shelled bivalves, with naturally formed exhalant and inhalant chambers.

There is almost a century of difference among Indo-Malayan, Australasian, and Neotropical regions in establishment of non-native populations of the giant African snail (Lissachatina fulica). Using potential distribution models and environmental principal component analysis (PCA-env), we first tested whether an expansion of the realized climatic niche of L. fulica occurred. The models showed geographical differences between the native and non-native areas, especially in the Neotropical region, where the last introduction of mollusks occurred. Because PCA-env showed a 60% expansion and 40% overlap between the native and global areas, we next investigated whether the expansion of the realized climatic niche of L. fulica was influenced by its geographical spread. Precipitation had the highest contribution in most models, but temperature was the variable that best explained the projected spread from the current Neotropical distribution. The current Neotropical distribution was better explained when the climatic conditions of the Indo-Malayan and Australasian regions from which the species arrived in the Neotropics were included. PCA-env showed 74% expansion between the native and Indo-Malayan–Australasian areas and 97% expansion between the native and Neotropical areas. In conclusion, the spread between biogeographic regions and the existence of similar climatic conditions between the native and non-native distributions would produce the observed climatic niche of L. fulica.

El establecimiento de las poblaciones no nativas del caracol gigante africano (Lissachatina fulica) lleva casi un siglo de diferencia entre las regiones indo-malaya, australiana y neotropical. Utilizando modelos de distribución potencial y análisis de componentes principales (PCA-env), comprobamos primero si se produjo una expansión del nicho climático realizado de L. fulica. Los modelos mostraron diferencias geográficas entre las zonas nativas y no nativas, especialmente en la región neotropical, donde se produjo la última introducción de la especie. Dado que el PCA-env mostró una expansión del 60% y un solapamiento del 40% entre las áreas nativa y no nativa, investigamos si la expansión del nicho climático realizado de L. fulica está influida por su dispersión. La precipitación tuvo la mayor contribución en la mayoría de los modelos, pero la temperatura fue la variable que mejor explicó la expansión proyectada desde la distribución neotropical actual. La distribución neotropical actual se explicó mejor cuando se incluyeron las condiciones climáticas de las regiones indo-malaya y australiana; posible origen de las poblaciones del Neotrópico. El PCA-env mostró un 74% de expansión entre las áreas nativa y indo-malaya y un 97% de expansión entre las áreas nativa y la neotropical. En conclusión, la expansión entre regiones biogeográficas y la existencia de condiciones climáticas similares entre las distribuciones nativas y no