Gut Cavity Research Articles

Pre-mandibular pharyngeal pouches in early non-teleost fish embryos.

The vertebrate pharynx is a key embryonic structure with crucial importance for the metameric organization of the head and face. The pharynx is primarily built upon progressive formation of paired pharyngeal pouches that typically develop in post-oral (mandibular, hyoid and branchial) domains. However, in the early embryos of non-teleost fishes, we have previously identified pharyngeal pouch-like outpocketings also in the pre-oral domain of the cranial endoderm. This pre-oral gut (POG) forms by early pouching of the primitive gut cavity, followed by the sequential formation of typical (post-oral) pharyngeal pouches. Here, we tested the pharyngeal nature of the POG by analysing expression patterns of selected core pharyngeal regulatory network genes in bichir and sturgeon embryos. Our comparison revealed generally shared expression patterns, including Shh, Pax9, Tbx1, Eya1, Six1, Ripply3 or Fgf8, between early POG and post-oral pharyngeal pouches. POG thus shares pharyngeal pouch-like morphogenesis and a gene expression profile with pharyngeal pouches and can be regarded as a pre-mandibular pharyngeal pouch. We further suggest that pre-mandibular pharyngeal pouches represent a plesiomorphic vertebrate trait inherited from our ancestor's pharyngeal metameric organization, which is incorporated in the early formation of the pre-chordal plate of vertebrate embryos.

Surrealistic Cestodes

Photo 1. Larval tapeworms (cestodes) in the gut cavity of an oyster toadfish. Photo credit: Christopher Moore. This photograph illustrates the article “Parasites indicate trophic complexity and faunal succession in restored oyster reefs over a 22-year period” by Christopher S. Moore, Christopher J. Baillie, Emily A. Edmonds, Rachel K. Gittman, and April M. H. Blakeslee published in Ecological Applications. https://doi.org/10.1002/eap.2825

Characterization of the bacterial microbiota in different gut and oral compartments of splendid japalure (Japalura sensu lato)

BackgroundGut and oral microbes form complex communities and play key roles in co-evolution with their hosts. However, little is understood about the bacterial community in lizards.ResultsIn this study, we investigated the gut and oral bacterial communities in Japalura sensu lato from Sichuan Province, China, using 16S rRNA gene sequencing. Results showed that Bacteroidota (36.5%) and Firmicutes (32.8%) were the main phyla in the gut, while Proteobacteria, Bacteroidota, Firmicutes, and Actinobacteriota were the dominant phyla in the oral cavity. 16 S rRNA sequencing analysis of fecal samples showed that: (1) Bacteroidota was the most abundant in Japalura sensu lato, which was different from the bacterial community of insectivorous animals; (2) Bacteroidota, Firmicutes, Actinobacteriota, Fusobacteriota, and Cyanobacteria were the most abundant phylum in Japalura sensu lato. (3) Proteobacteria was the dominant phylum in Japalura sensu lato and other domestic insectivorous lizards (Shinisaurus crocodilurus, Phrynocephalus vlangalii, and Takydromus septentrionalis); (4) Comparing with the bacterial community of Shinisaurus crocodilurus, Phrynocephalus vlangalii, Takydromus septentrionalis, Liolaemus parvus, L. ruibali, and Phymaturus williamsi, Desulfobacterota was uniquely present in the gut of Japalura sensu lato. 16 S rRNA sequencing of oral samples showed that Chloroflexi and Deinococcota phyla were enriched in the oral cavity, which may have a significant influence on living in extreme environments.ConclusionsThus, based on 16 S rRNA sequencing analysis of the community composition of the gut and oral microbiomes, this study firstly represents a foundation for understanding the gut and oral microbial ecology of Japalura sensu lato, and constitutes a detail account of the diversity of the microbiota inhabiting the gut and oral cavity of Japalura sensu lato. Further researches will continue to reveal how gut and oral microbial communities may be impacting the ecology and evolution of lizards.

Initial experience: ex-vivo perfused pig kidney to study urinary oxalate excretion.

Existing animal models of renal oxalate excretion utilize either gut or peritoneal cavity for oxalate absorption. Ex vivo renal perfusion is an established tool for graft preservation. We sought to repurpose this concept to study the early pathogenesis of urinary lithiasis. Juvenile female Yorkshire porcine kidneys were removed laparoscopically and placed on an ex vivo cardiopulmonary bypass circuit utilizing whole-blood based perfusate. Pre-defined goals were identified for each attempt (n = 5) with plans to increase physiologic model complexity. Tissue perfusion and oxygenation were monitored by serial perfusate iSTAT testing. Once steady urine production was achieved, aqueous oxalate was injected into the perfusate. Renal outcomes were assessed by histology and blood/urinary assays. After demonstrating proof-of-concept in early trials, normothermic (37°C) ex vivo whole-blood perfusion with Steen Solution™ was performed exceeding three hours at physiologic mean arterial pressures. Circuit parameters remained in the physiologic range for electrolytes, temperature, mean arterial pressure, lactate, and pH. Urine was produced in three experiments. Urinary filtrate demonstrated consistently higher urine creatinine compared to perfusate, and arterial perfusate oxalate boluses lead to urinary oxalate spikes followed by continuous oxalate clearance. Histopathologic analysis with H&E and Pizzolato's method staining demonstrated formation of calcium oxalate crystals. In light of these promising metabolite clearances, ex vivo porcine renal perfusion appears to be a feasible alternative to study oxalate excretion. Longer validation studies are necessary to establish this technique as a model for kidney stone pathogenesis.

JNK Mediates Differentiation, Cell Polarity and Apoptosis During Amphioxus Development by Regulating Actin Cytoskeleton Dynamics and ERK Signalling.

c-Jun N-terminal kinase (JNK) is a multi-functional protein involved in a diverse array of context-dependent processes, including apoptosis, cell cycle regulation, adhesion, and differentiation. It is integral to several signalling cascades, notably downstream of non-canonical Wnt and mitogen activated protein kinase (MAPK) signalling pathways. As such, it is a key regulator of cellular behaviour and patterning during embryonic development across the animal kingdom. The cephalochordate amphioxus is an invertebrate chordate model system straddling the invertebrate to vertebrate transition and is thus ideally suited for comparative studies of morphogenesis. However, next to nothing is known about JNK signalling or cellular processes in this lineage. Pharmacological inhibition of JNK signalling using SP600125 during embryonic development arrests gastrula invagination and causes convergence extension-like defects in axial elongation, particularly of the notochord. Pharynx formation and anterior oral mesoderm derivatives like the preoral pit are also affected. This is accompanied by tissue-specific transcriptional changes, including reduced expression of six3/6 and wnt2 in the notochord, and ectopic wnt11 in neurulating embryos treated at late gastrula stages. Cellular delamination results in accumulation of cells in the gut cavity and a dorsal fin-like protrusion, followed by secondary Caspase-3-mediated apoptosis of polarity-deficient cells, a phenotype only partly rescued by co-culture with the pan-Caspase inhibitor Z-VAD-fmk. Ectopic activation of extracellular signal regulated kinase (ERK) signalling in the neighbours of extruded notochord and neural cells, possibly due to altered adhesive and tensile properties, as well as defects in cellular migration, may explain some phenotypes caused by JNK inhibition. Overall, this study supports conserved functions of JNK signalling in mediating the complex balance between cell survival, apoptosis, differentiation, and cell fate specification during cephalochordate morphogenesis.

Reduced Genome of the Gut Symbiotic Bacterium "Candidatus Benitsuchiphilus tojoi" Provides Insight Into Its Possible Roles in Ecology and Adaptation of the Host Insect.

Diverse animals, including insects, harbor microbial symbionts within their gut, body cavity, or cells. The subsocial parastrachiid stinkbug Parastrachia japonensis is well-known for its peculiar ecological and behavioral traits, including its prolonged non-feeding diapause period and maternal care of eggs/nymphs in an underground nest. P. japonensis harbors a specific bacterial symbiont within the gut cavity extracellularly, which is vertically inherited through maternal excretion of symbiont-containing white mucus. Thus far, biological roles of the symbiont in the host lifecycle has been little understood. Here we sequenced the genome of the uncultivable gut symbiont “Candidatus Benitsuchiphilus tojoi.” The symbiont has an 804 kb circular chromosome encoding 606 proteins and a 14.5 kb plasmid encoding 13 proteins. Phylogenetic analysis indicated that the bacterium is closely related to other obligate insect symbionts belonging to the Gammaproteobacteria, including Buchnera of aphids and Blochmannia of ants, and the most closely related to Ishikawaella, an extracellular gut symbiont of plataspid stinkbugs. These data suggested that the symbiont genome has evolved like highly reduced gamma-proteobacterial symbiont genomes reported from a variety of insects. The presence of genes involved in biosynthesis pathways for amino acids, vitamins, and cofactors in the genome implicated the symbiont as a nutritional mutualist, supplementing essential nutrients to the host. Interestingly, the symbiont’s plasmid encoded genes for thiamine and carotenoid synthesis pathways, suggesting the possibility of additional functions of the symbiont for protecting the host against oxidative stress and DNA damage. Finally, possible involvement of the symbiont in uric acid metabolism during diapause is discussed.

Current Understanding of the Gut Microflora in Subjects with Nutrition-Associated Metabolic Disorder Such as Obesity and/or Diabetes: Is There Any Relevance with Oral Microflora?

Purpose of review: The oral cavity is one of the main gateways to the whole body and leads to the gastrointestinal tract. Both oral cavity and gastrointestinal tract have complex ecosystems of microorganisms called microbiota. Recent studies have showed that altered local microbiome in human, such as gut microflora, is associated with various systemic diseases. This review focuses on the association between the microbiota at local sites, such as gut and oral cavity, and the systemic diseases, especially nutrition-associated metabolic disorder, such as obesity and/or diabetes. Recent findings: The gut microbiota has a potential for regulation in host immune system and metabolisms, such as energy, glucose and lipid, and is therefore an additional contributing environmental factor to the pathophysiology of obesity and diabetes as well as gut infectious inflammatory diseases. In addition, oral microorganisms play important roles as reservoirs for exacerbation of gut diseases and altered oral microbial profiles causing periodontal diseases, one of common oral infectious diseases, has been also associated with several systemic diseases including diabetes. Summary: It is necessary to consider that impaired oral microbiota, called oral dysbiosis, may affect the metabolic disorders leading to obesity and diabetes in addition to the gut inflammatory diseases via alteration of gut microflora. The relevance of oral microflora to gut dysbiosis leading to nutrition-associated metabolic disorder should be addressed as future investigations.

Ingested microscopic plastics translocate from the gut cavity of juveniles of the ascidian Ciona intestinalis

Small plastic particles, named microplastics, are abundant in the marine environment and can be ingested by marine organisms. Species with different feeding strategies can be differently affected by the presence of microplastics. Moreover, the impact of these particles can depend on their size. In this study, we analyzed the effects of 1 µm polystyrene particles on larval and juvenile development in the ascidian Ciona intestinalis. As previously reported for 10 µm beads, smaller particles caused a delay in the growth of juveniles, even if this delay was registered only at the highest concentration tested. Instead, larval development was not affected by the presence of microplastics. Histological analysis of juveniles revealed that 1 µm particles, after ingestion, can translocate from the gut to the hemocoelic cavity in just 8 days. As a defense mechanism, plastic spheres can also be phagocytized from specific circulating cells with phagocytic activity. Microplastics confirmed their potential as a threat to marine wildlife, interfering with food uptake and growth.

Hubungan Pemberian Mp-Asi Pada Bayi Usia 0-6 Bulan Dengan Terjadinya Diare Di Desa Pacet Kecamatan Pacet Kabupaten Mojokerto

Complementary feeding (MP-ASI) was food and beverage contain of nutrients, which gave to infants or children age 6-24 months in order to meet the nutritional needs in addition to breast milk. The incidence of diarrhea in infants can be caused due to errors in feeding, where the baby has been feed than breast milk before the age of 6 months. This study aimed to analyze the relationship between the give complementary feeding in baby age 0-6 months with incidence diarrhea at the Pacet Village, Pacet District, Mojokerto. The research of the population has been taken from all baby 0-6 months at the Pacet Village, Pacet District, Mojokerto. And got the sample from 42 respondents with techniq of gotten the sample was Total Sampling. That was calling a retrospective research. Meanwhile processing data analysis was using coding, scoring, tabulating, and cross tabulation. Based on the result, it was showing that A Corellation of Giving Complementary Feeds (MP- ASI) to baby 0-6 months with incidence diarrhea in Pacet Village Pacet District Mojokerto. Feeding companion early breastfeeding can cause interference with absorption in the intestine due to the baby's digestive system is less than 6 months old and has not been perfect. Malabsorption that occurs will cause osmotic pressure in intestinal cavity increases resulting in a shift of water and electrolytes into gut cavity would which result diarrhea.;Keywords: breast milk, baby 0-6 months, the incidence of diarrhea

Trophic transference of microplastics under a low exposure scenario: Insights on the likelihood of particle cascading along marine food-webs

Microplastics are emergent pollutants in marine environments, whose risks along food-web still need to be understood. Within this knowledge gap, MPs transference and persistence along trophic levels are key processes. We assessed the potential occurrence of these processes considering a less extreme scenario of exposure than used previously, with microplastics present only in the hemolymph of prey (the mussel Perna perna) and absent in the gut cavity. Predators were the crab Callinectes ornatus and the puffer fish Spheoeroides greeleyi. Transference of microplastics occurred from prey to predators but without evidences of particle persistence in their tissues after 10days of exposure. This suggests a reduced likelihood of trophic cascading of particles and, consequently, a reduced risk of direct impacts of microplastics on higher trophic levels. However, the contact with microplastics along food-webs is still concerning, modulated by the concentration of particles in prey and predators' depuration capacity and rate.

Life cycle of the taiga tick Ixodes persulcatus (Acari: Ixodidae) in the North-West of Russia.

The life cycle of Ixodes persulcatus lasts 3years in the conditions of the Leningrad province (North-West Russia), the development of each phase taking a year. The normal age of the taiga tick is 3years. The calendar age of larvae and nymphs reaches 11-12months under favorable abiotic and biotic factors, while the calendar age of adults does not exceed 11months. At the preimaginal phases of development the ticks that breed in August can feed before or after winter. However, their metamorphosis begins and reaches completion within the same timeframes (from late June to early August) and lasts for about 30-50 (60) days. The survival rate of hungry and engorged larvae and nymphs after wintering is quite high (88.6-100%). We explain the low activity of larvae and nymphs in late summer and autumn by incomplete development. Morphogenetic diapause of engorged larvae and nymphs interrupts digestion but not metamorphosis which starts only in late June and July after the complete absorption of blood from the gut cavity.

Herbivory-induced glucose transporter gene expression in the brown planthopper, Nilaparvata lugens

Nilaparvata lugens, the brown planthopper (BPH) feeds on rice phloem sap, containing high amounts of sucrose as a carbon source. Nutrients such as sugars in the digestive tract are incorporated into the body cavity via transporters with substrate selectivity. Eighteen sugar transporter genes of BPH (Nlst) were reported and three transporters have been functionally characterized. However, individual characteristics of NlST members associated with sugar transport remain poorly understood. Comparative gene expression analyses using oligo-microarray and quantitative RT-PCR revealed that the sugar transporter gene Nlst16 was markedly up-regulated during BPH feeding. Expression of Nlst16 was induced 2 h after BPH feeding on rice plants. Nlst16, mainly expressed in the midgut, appears to be involved in carbohydrate incorporation from the gut cavity into the hemolymph. Nlst1 (NlHT1), the most highly expressed sugar transporter gene in the midgut was not up-regulated during BPH feeding. The biochemical function of NlST16 was shown as facilitative glucose transport along gradients. Glucose uptake activity by NlST16 was higher than that of NlST1 in the Xenopus oocyte expression system. At least two NlST members are responsible for glucose uptake in the BPH midgut, suggesting that the midgut of BPH is equipped with various types of transporters having diversified manner for sugar uptake.

Microplastic ingestion by scleractinian corals

We report for the first time the ingestion of microplastics by scleractinian corals, and the presence of microplastics in coral reef waters adjacent to inshore reefs on Australia’s Great Barrier Reef (GRE, 18°31′S 146°23′E). Analysis of samples from sub-surface plankton tows conducted in close proximity to inshore reefs on the central GBR revealed microplastics, similar to those used in marine paints and fishing floats, were present in low concentrations at all water sampling locations. Experimental feeding trials revealed that corals mistake microplastics for prey and can consume up to ~50 μg plastic cm−2 h−1, rates similar to their consumption of plankton and Artemia nauplii in experimental feeding assays. Ingested microplastics were found wrapped in mesenterial tissue within the coral gut cavity, suggesting that ingestion of high concentrations of microplastic debris could potentially impair the health of corals.

Acquisition and Transmission Efficiency of the HLB Bacterium, ‘Candidatus Liberibacter asiaticus’ by the Striped Mealybug, Ferrisia virgata

‘Candidatus Liberibacter asiaticus’ (Las) is the prevalent species of three different Liberibacter associated with citrus huanglongbing (HLB). Two psyllid species, Diaphorina citri and Trioza erytreae, are currently known to transmit Liberibacter bacteria. In this study, we tested the acquisition and transmission efficiency of Las by striped mealybugs (Ferrisia virgata) (Pseudococcidae; Hemiptera), another phloem-sap feeding insect with a broad host range of 264 species in 68 plant families. In our previous report, 63.0 % of striped mealybugs collected from the Las-infected periwinkle plants in USHRL greenhouse tested positive for Las using the HLBasp primers and probe, and the Las populations were estimated at 3.11 x 103 to 2.32 x 105 cells per mealybug. This was confirmed using conventional PCR with six primer sets targeting different Las loci and by the 100% identity of all seven PCR amplicons to the known Las sequences. However, attempts to transmit the disease in periwinkle and citrus using Las-infected mealybugs were not successful. To reveal the reason why Las-infected mealybugs were not able to transmit the disease, we used a leaf-disc bioassay in conjunction with typing of Las populations. Positive Las results were found in 100% of the mealybugs after feeding for 1-2 weeks on infected leaf discs that were obtained from infected periwinkle and citrus leaves. In addition, Las bacteria were detected in mealybug gut, salivary glands and body cavity, with the titer in the gut and body being higher than that in the salivary glands. It is of interest to note that mealybugs grown on infected leaf-discs for 1 week and then transferred to non-infected leaf-discs did not test positive for Las. However, mealybugs grown on infected leaf-discs for 2 weeks and then transferred to non-infected leaf-discs for 2 more weeks remained positive for Las. These results indicate that striped mealybugs share similarities and differences in comparison with the Asian citrus psyllids in terms of acquisition and/or transmission of the Las bacterium.

High inorganic phosphate concentration in coral mucus and its utilization by heterotrophic bacteria in a Malaysian coral reef

AbstractInorganic nutrient contents of mucus released by Acropora corals and its utilization by heterotrophic bacteria at several different hour intervals in the coral mucus were investigated at a coral reef in Malaysia. The dissolved inorganic phosphate (DIP) concentration was 135‐fold higher than in the ambient seawater, probably due to inorganic P release from the coral gut cavity. We experimentally confirmed that heterotrophic bacteria rapidly (within 8 h) consumed ca. 80% of the initial concentration of DIP derived from coral mucus. High DIP concentration in coral mucus may enhance heterotrophic bacterial production and associated carbon flow in the microbial loop of reef ecosystems.

Discrimination between weaned and unweaned Atlantic cod (Gadus morhua) in capture-based aquaculture (CBA) by X-ray imaging and radio-frequency metal detector.

The aim of this study was to investigate the feasibility of two detection methods for use in discrimination and sorting of adult Atlantic cod (about 2 kg) in the small scale capture-based aquaculture (CBA). Presently, there is no established method for discrimination of weaned and unweaned cod in CBA. Generally, 60–70% of the wild-caught cod in the CBA are weaned into commercial dry feed. To increase profitability for the fish farmers, unweaned cod must be separated from the stock, meaning the fish must be sorted into two groups – unweaned and weaned from moist feed. The challenges with handling of large numbers of fish in cages, defined the limits of the applied technology. As a result, a working model was established, focusing on implementing different marking materials added to the fish feed, and different technology for detecting the feed presence in the fish gut. X-ray imaging in two modes (planar and dual energy band) and sensitive radio-frequency metal detection were the detection methods that were chosen for the investigations. Both methods were tested in laboratory conditions using dead fish with marked feed inserted into the gut cavity. In particular, the sensitive radio-frequency metal detection method with carbonyl powder showed very promising results in detection of marked feed. Results show also that Dual energy band X-ray imaging may have potential for prediction of fat content in the feed. Based on the investigations it can be concluded that both X-ray imaging and sensitive radio-frequency metal detector technology have the potential for detecting cod having consumed marked feed. These are all technologies that may be adapted to large scale handling of fish from fish cages. Thus, it may be possible to discriminate between unweaned and weaned cod in a large scale grading situation. Based on the results of this study, a suggestion for evaluation of concept for in-situ sorting system is presented.

Short-term survival of discarded pearl perch (Glaucosoma scapulare Ramsay, 1881) caught by hook-and-line in Queensland, Australia

Post-release survival of line-caught pearl perch (Glaucosoma scapulare) was assessed via field experiments where fish were angled using methods similar to those used by commercial, recreational and charter fishers. One hundred and eighty-three individuals were caught during four experiments, of which >91% survived up to three days post-capture. Hook location was found to be the best predictor of survival, with the survival of throat- or stomach-hooked pearl perch significantly (P<0.05) lower than those hooked in either the mouth or lip. Post-release survival was similar for both legal (≥35cm) and sub-legal (<35cm) pearl perch, while those individuals showing no signs of barotrauma were more likely to survive in the short term. Examination of the swim bladders in the laboratory, combined with observations in the field, revealed that swim bladders rupture during ascent from depth allowing swim bladder gases to escape into the gut cavity. As angled fish approach the surface, the alimentary tract ruptures near the anus allowing swim bladder gases to escape the gut cavity. As a result, very few pearl perch exhibit barotrauma symptoms and no barotrauma mitigation strategies were recommended. The results of this study show that pearl perch are relatively resilient to catch-and-release suggesting that post-release mortality would not contribute significantly to total fishing mortality. We recommend the use of circle hooks, fished actively on tight lines, combined with minimal handling in order to maximise the post-release survival of pearl perch.

An Unusual Feature of Malaria: Exflagellated Microgametes of Malarial Parasites in Human Peripheral Blood

Exflagellation of the malaria parasite microgametocyte usually occurs in the gut cavity of Anopheles mosquitoes following an infective blood meal. Exflagellation is a very rare event in human blood. Due to its rarity, the appearance of this structure in a peripheral blood smear will easily create a diagnostic dilemma. We report a case of malaria with exflagellated microgametes in human blood that was initially mistaken for a double infection of Plasmodium and another blood flagellate. The patient was a 29-year-old Parkistani man presenting with fluctuating fever accompanied by chills and fatigue for 4 days. Initial peripheral blood smear examination showed a number of Plasmodium ring forms, trophozoites, and gametocytes. Additionally, several filamentous structures resembling blood flagellates were seen. With these features, an initial diagnostic impression of combined infection of malaria and blood flagellate was made. Later, we determined that these structures resembling blood flagellates were exflagellated microgametes of malarial parasite. Therefore, the knowledge that exflagellation may appear in human blood with Plasmodium species infection and being more familiar with differentiation of the morphologic features of other species infection can prevent further possible misinterpretation. (Korean J Clin Microbiol 2012;15:151-153)

Multi-component complement system of Cnidaria: C3, Bf, and MASP genes expressed in the endodermal tissues of a sea anemone, Nematostella vectensis

The origin of the complement system, one of the major systems of mammalian innate immunity, is more ancient than that of the adaptive immune system, as shown by the identification of the gene for the complement component 3 (C3) in a basic metazoa, cnidarian coral. Only a few reports on the other complement genes of non-chordates have been published, and the composition of the ancient complement system has not been clarified. We performed comprehensive cloning of the complement genes with characteristic domain structures using a Cnidarian, the sea anemone, Nematostella vectensis. Partial sequences of the two C3, two factor B ( Bf), and one mannan-binding protein-associated serine protease ( MASP) genes were identified in the draft genome data, and the complete coding sequences of these genes were elucidated by RT-PCR and 5′- and 3′-RACE. In contrast, no C6 and factor I family genes were identified. These cnidarian components shared the unique domain structures and most of the functionally critical amino acid residues with their mammalian counterparts, suggesting the conservation of their basic biochemical functions throughout metazoan evolution. In situ hybridization analysis indicated that all five genes are expressed in the tentacles, pharynx, and mesentery in an endoderm-specific manner. These results suggest that the multi-component complement system comprising at least C3, Bf, and MASP was established in a common ancestor of Cnidaria and Bilateria more than 600 million years ago to protect the coelenteron, the primitive gut cavity with putative circulatory functions.

Histological examination of the chaetognathan morphological structure in the region of a supposed trunk-tail septum

A histological examination was conducted based on sections done in series in transverse and longitudinal directions of Aidanosagitta macilenta (Sagittidae, Chaetognatha) in a region which includes the anterior parts of the testes and the posterior part of the ovaries. We found that, in mature individuals (the 4th stage of maturation), the anterior parts of the testes are located in front of the posterior part of the ovaries. The anterior parts of the testes have a ventral position adjoining the ventral muscular bands. The ovaries are located more dorsally than the testes at the level of lateral fi elds. A transverse trunk-tail septum between testes and ovaries was not revealed. These data support an idea that a structure which was earlier treated as a tail-trunk septum is actually the anterior edges of the testes. Both longitudinal coelomic cavities continue into the tail region without any transverse septa. The paired tail cavities as can be seen from their composition and functions represent the testes consisting of a peripheral compact portion with undifferentiated germ cells and a space where the maturation of cells occurs. The tail is distinguished anatomically as a post-anal portion of the body but it is not a true segment as it is not separated from a trunk part of the body by the trunk-tail septum. The body of Chaetognatha consists of two true parts (segments). A mesenterial septum divides the body longitudinally-symmetrically from a trunk-head septum down only to the caudal end of the gut. In the tail region there is a medial septum formed by the medial walls of testes. Gonads in both females and males do not have any duct connecting them with a gut cavity. The ovaries and the testes are covered by a coelomic lining and a duct between the ovaries and the testes is absent.