Excretory Canal Research Articles

The C. elegans nck-1 gene encodes two isoforms and is required for neuronal guidance

The NCK adaptor proteins are composed entirely of SH3 and SH2 domains and serve as protein interaction bridges for several receptors during signal transduction events. Here we report the molecular and genetic analysis of the Caenorhabditis elegans nck-1 gene. C. elegans nck-1 encodes two isoforms: NCK-1A and a shorter isoform that lacks the first SH3 domain, NCK-1B. C. elegans nck-1 mutants exhibit defects in axon guidance and neuronal cell position, as well as defects in the excretory canal cell, gonad, and male mating. NCK-1 is broadly expressed in neurons and epithelial cells with NCK-1B being the most abundant isoform. NCK-1A and NCK-1B share a similar expression pattern in parts of the nervous system, but also have independent expression patterns in other tissues. Interestingly, NCK-1B is localized to the nuclei of many cells. Genetic rescue experiments show that NCK-1 functions cell autonomously and, in general, either NCK-1A or NCK-1B is sufficient to function in axon guidance. However, there appears to be specific roles for each isoform, for example NCK-1B is required for HSN cell migration while NCK-1A is required for efficient male mating. Genetic epistasis experiments show that NCK-1 functions redundantly with the LAR Receptor Tyrosine Phosphatase, PTP-3, and the Netrin receptor UNC-40.

The Cooperation of FGF Receptor and Klotho Is Involved in Excretory Canal Development and Regulation of Metabolic Homeostasis in Caenorhabditis elegans

FGFs have traditionally been associated with cell proliferation, morphogenesis, and development; yet, a subfamily of FGFs (FGF19, -21, and -23) functions as hormones to regulate glucose, lipid, phosphate, and vitamin D metabolism with impact on energy balance and aging. In mammals, Klotho and beta-Klotho are type 1 transmembrane proteins that function as obligatory co-factors for endocrine FGFs to bind to their cognate FGF receptors (FGFRs). Mutations in Klotho/beta-Klotho or fgf19, -21, or -23 are associated with a number of human diseases, including autosomal dominant hypophosphatemic rickets, premature aging disorders, and diabetes. The Caenorhabditis elegans genome contains two paralogues of Klotho/beta-Klotho, klo-1, and klo-2. klo-1 is expressed in the C. elegans excretory canal, which is structurally and functionally paralogous to the vertebrate kidney. KLO-1 associates with EGL-15/FGFR, suggesting a role for KLO-1 in the fluid homeostasis phenotype described previously for egl-15/fgfr mutants. Altered levels of EGL-15/FGFR signaling lead to defects in excretory canal development and function in C. elegans. These results suggest an evolutionarily conserved function for the FGFR-Klotho complex in the development of excretory organs such as the mammalian kidney and the worm excretory canal. These results also suggest an evolutionarily conserved function for the FGFR-Klotho axis in metabolic regulation.

Ultrastructure of excretory system in Bothrioplana semperi (Platyhelminthes, Turbellaria)

The ultrastructure of flame bulbs and epithelium of excretory canals in Bothrioplana semperi (Turbellaria, Seriata) have been studied. The flame bulbs consist of two cells, the terminal cell and the proximal canal cell. The weir is formed by two rows of longitudinal ribs. The ribs of the internal row originate from the flame cell, external ribs are formed by the proximal canal cell. Each external rib has a remarkable bundle of microfilaments, originating in the cytoplasm of the first canal cell distally to the bases of external ribs. Membrane of internal ribs is marked by small electrondense granules, separate or fused to an electron-dense layer, continuous to dense “membrane,” connecting both external and internal ribs. Sparse internal leptotrichs originate from the bottom of the flame bulb cavity. External leptotrichs are lacking. Septate junction is present only in proximal canal cell at the level of tips of cilia. The apical surface of the canal cell bears rare short microvilli. The basal membrane of canal cells forms long invaginations that may reach nearly the apical membrane. The epithelium of excretory canals lacks the cilia. The ultrastructure of flame bulbs and epithelium of the excretory canals in B. semperi shares representatives of suborder Proseriata (Seriata). The contradiction exists in interpretation of the structure of flame bulbs in Proseriata. Ehlers and Sopott-Ehlers assumed that the external ribs are derivatives of the proximal canal cell and internal ones are outgrowths of the terminal cell, while Rohde has found conversely: the external ribs are outgrowths of the terminal cell, the internal ones are outgrowths of the proximal canal cell. However, the illustrations provided by Rohde do not enable to ascertain what cells the internal and external ribs derive from, while illustrations provided by Ehlers justify his interpretation. The order of weir formation in B. semperi confirms the viewpoint of Ehlers. The implication of ultrastructure of flame bulbs in Proseriata, especially of the order of flame bulb formation, in the Platyhelminthes phylogeny has been discussed.

Characterization of the octamer, a cis-regulatory element that modulates excretory cell gene-expression in Caenorhabditis elegans.

BackgroundWe have previously demonstrated that the POU transcription factor CEH-6 is required for driving aqp-8 expression in the C. elegans excretory (canal) cell, an osmotic regulatory organ that is functionally analogous to the kidney. This transcriptional regulation occurs through a CEH-6 binding to a cis-regulatory element called the octamer (ATTTGCAT), which is located in the aqp-8 promoter.ResultsHere, we further characterize octamer driven transcription in C. elegans. First, we analyzed the positional requirements of the octamer. To do so, we assayed the effects on excretory cell expression by placing the octamer within the well-characterized promoter of vit-2. Second, using phylogenetic footprinting between three Caenorhabditis species, we identified a set of 165 genes that contain conserved upstream octamers in their promoters. Third, we used promoter::GFP fusions to examine the expression patterns of 107 of the 165 genes. This analysis demonstrated that conservation of octamers in promoters increases the likelihood that the gene is expressed in the excretory cell. Furthermore, we found that the sequences flanking the octamers may have functional importance. Finally, we altered the octamer using site-directed mutagenesis. Thus, we demonstrated that some nucleotide substitutions within the octamer do not affect the expression pattern of nearby genes, but change their overall expression was changed. Therefore, we have expanded the core octamer to include flanking regions and variants of the motif.ConclusionsTaken together, we have demonstrated that octamer-containing regions are associated with excretory cell expression of several genes that have putative roles in osmoregulation. Moreover, our analysis of the octamer sequence and its sequence variants could aid in the identification of additional genes that are expressed in the excretory cell and that may also be regulated by CEH-6.

The Caenorhabditis elegans HNF4α Homolog, NHR-31, Mediates Excretory Tube Growth and Function through Coordinate Regulation of the Vacuolar ATPase

Nuclear receptors of the Hepatocyte Nuclear Factor-4 (HNF4) subtype have been linked to a host of developmental and metabolic functions in animals ranging from worms to humans; however, the full spectrum of physiological activities carried out by this nuclear receptor subfamily is far from established. We have found that the Caenorhabditis elegans nuclear receptor NHR-31, a homolog of mammalian HNF4 receptors, is required for controlling the growth and function of the nematode excretory cell, a multi-branched tubular cell that acts as the C. elegans renal system. Larval specific RNAi knockdown of nhr-31 led to significant structural abnormalities along the length of the excretory cell canal, including numerous regions of uncontrolled growth at sites near to and distant from the cell nucleus. nhr-31 RNAi animals were sensitive to acute challenge with ionic stress, implying that the osmoregulatory function of the excretory cell was also compromised. Gene expression profiling revealed a surprisingly specific role for nhr-31 in the control of multiple genes that encode subunits of the vacuolar ATPase (vATPase). RNAi of these vATPase genes resulted in excretory cell defects similar to those observed in nhr-31 RNAi animals, demonstrating that the influence of nhr-31 on excretory cell growth is mediated, at least in part, through coordinate regulation of the vATPase. Sequence analysis revealed a stunning enrichment of HNF4α type binding sites in the promoters of both C. elegans and mouse vATPase genes, arguing that coordinate regulation of the vATPase by HNF4 receptors is likely to be conserved in mammals. Our study establishes a new pathway for regulation of excretory cell growth and reveals a novel role for HNF4-type nuclear receptors in the development and function of a renal system.

Mammalian Navigators are microtubule plus‐end tracking proteins that can reorganize the cytoskeleton to induce neurite‐like extensions

Mammalian microtubule plus-end tracking proteins (+TIPs) specifically associate with the ends of growing microtubules. +TIPs are involved in many cellular processes, including mitosis, cell migration and neurite extension. Navigators are mammalian homologues of the C. elegans unc-53 protein, an ATPase that has been linked to the migration and outgrowth of muscles, axons and excretory canals. Here we show that all three mammalian Navigators are +TIPs, consistent with a previous study on Navigator 1 (NAV1) (Martinez-Lopez et al., Mol Cell Neurosci 2005;28:599-612). Overexpression of GFP-tagged Navigators causes displacement of CAP_GLY-motif containing +TIPs, such as CLIP-170, from microtubule ends, suggesting that the Navigator-binding sites on microtubule ends overlap with those of the CAP_GLY-motif proteins. In interphase cells, mammalian Navigators also prominently localize to centrosomes, a localization that does not depend on an intact microtubule network. Fluorescence recovery after photobleaching (FRAP) experiments indicate that NAV1 associates with intracellular structures other than microtubules or centrosomes. Expression of GFP-tagged Navigators induces the formation of neurite-like extensions in non-neuronal cells, showing that Navigators can dominantly alter cytoskeletal behavior. For NAV1 this function depends on its ATPase activity; it is not achieved by a classical type of MT bundling and stabilization. Combined our data suggest that Navigators are +TIPs that can reorganize the cytoskeleton to guide cell shape changes. Our data are consistent with a role for Navigators in neurite outgrowth.

Chloride intracellular channel 4 is involved in endothelial proliferation and morphogenesis in vitro

New capillaries are formed through angiogenesis and an integral step in this process is endothelial tubulogenesis. The molecular mechanisms driving tube formation during angiogenesis are not yet delineated. Recently, the chloride intracellular channel 4 (CLIC4)-orthologue EXC-4 was found to be necessary for proper development and maintenance of the Caenorhabditis elegans excretory canal, implicating CLIC4 as a regulator of tubulogenesis. Here, we studied the role of CLIC4 in angiogenesis and endothelial tubulogenesis. We report the effects of inhibiting or inducing CLIC4 expression on distinct aspects of endothelial cell behavior in vitro. Our experiments utilized RNA interference to establish cultured human endothelial cell lines with significant reduction of CLIC4 expression, and a CLIC4-expressing lentiviral plasmid was used to establish CLIC4 overexpression in endothelial cells. We observed no effect on cell migration and a modest effect on cell survival. Reduced CLIC4 expression decreased cell proliferation, capillary network formation, capillary-like sprouting, and lumen formation. This suggests that normal endogenous CLIC4 expression is required for angiogenesis and tubulogenesis. Accordingly, increased CLIC4 expression promoted proliferation, network formation, capillary-like sprouting, and lumen formation. We conclude that CLIC4 functions to promote endothelial cell proliferation and to regulate endothelial morphogenesis, and is thus involved in multiple steps of in vitro angiogenesis.

The Caenorhabditis elegans AMP-activated Protein Kinase AAK-2 Is Phosphorylated by LKB1 and Is Required for Resistance to Oxidative Stress and for Normal Motility and Foraging Behavior

AAK-2 is one of two alpha isoforms of the AMP-activated protein kinase in Caenorhabditis elegans and is involved in life span maintenance, stress responses, and germ cell cycle arrest upon dauer entry. We found that AAK-2 was phosphorylated at threonine 243 in response to paraquat treatment and that this phosphorylation depends on PAR-4, the C. elegans LKB1 homologue. Both aak-2 mutation and par-4 knockdown increased the sensitivity of C. elegans worms to paraquat, and the double deficiency did not further increase sensitivity, indicating that aak-2 and par-4 act in a linear pathway. Both mutations also slowed body bending during locomotion and failed to reduce head oscillation in response to anterior touch. Consistent with this abnormal motility and behavioral response, expression of the AAK-2::green fluorescent protein fusion protein was observed in the ventral cord, some neurons, body wall muscle, pharynx, vulva, somatic gonad, and excretory cell. Our study suggests that AMPK can influence the behavior of C. elegans worms in addition to its well known function in metabolic control.

CRIP homologues maintain apical cytoskeleton to regulate tubule size in C. elegans

Maintenance of the shape and diameter of biological tubules is a critical task in the development and physiology of all metazoan organisms. We have cloned the exc-9 gene of Caenorhabditiselegans, which regulates the diameter of the single-cell excretory canal tubules. exc-9 encodes a homologue of the highly expressed mammalian intestinal LIM-domain protein CRIP, whose function has not previously been determined. A second well-conserved CRIP homologue functions in multiple valves of C. elegans. EXC-9 shows genetic interactions with other EXC proteins, including the EXC-5 guanine exchange factor that regulates CDC-42 activity. EXC-9 and its nematode homologue act in polarized epithelial cells that must maintain great flexibility at their apical surface; our results suggest that CRIPs function to maintain cytoskeletal flexibility at the apical surface.

Caenorhabditis elegans WNK–STE20 pathway regulates tube formation by modulating ClC channel activity

WNK kinases are a small group of unique serine/threonine protein kinases that are conserved among multicellular organisms. Mutations in WNK1-4 cause pseudohypoaldosteronism type II-a form of hypertension. WNKs have been linked to the STE20 kinases and ion carriers, but the underlying molecular mechanisms by which WNKs regulate cellular processes in whole animals are unknown. The Caenorhabditis elegans WNK-like kinase WNK-1 interacts with and phosphorylates germinal centre kinase (GCK)-3--a STE20-like kinase--which is known to inactivate CLH-3, a CIC chloride channel. The wnk-1 or gck-3 deletion mutation causes an Exc phenotype, a defect in the tubular extension of excretory canals. Expression of the activated form of GCK-3 or the clh-3 deletion mutation can partly suppress wnk-1 or gck-3 defects, respectively. These results indicate that WNK-1 controls the tubular formation of excretory canals by activating GCK-3, resulting in downregulation of CIC channel activity.

Caenorhabditis elegans Glutamate Transporters Influence Synaptic Function and Behavior at Sites Distant from the Synapse

To ensure precise neurotransmission and prevent neurotoxic accumulation, l-glutamate (Glu), the major excitatory neurotransmitter in the brain, is cleared from the synapse by glutamate transporters (GluTs). The molecular components of Glu synapses are highly conserved between Caenorhabditis elegans and mammals, yet the absence of synaptic insulation in C. elegans raises fundamental questions about Glu clearance strategies in the nematode nervous system. To gain insight into how Glu clearance is accomplished and how GluTs impact neurotransmission, we probed expression and function of all 6 GluTs found in the C. elegans genome. Disruption of each GluT impacts multiple Glu-dependent behaviors, with GluT combinations commonly increasing the severity of behavioral deficits. Interestingly, the sole GluT that we find expressed in neurons is localized predominantly in presynaptic neurons, in contrast to the postsynaptic concentration of neuronal GluTs typical in mammals. Moreover, 3 of the 6 GluT genes appear strongly expressed on the capillary excretory canal cell, where they affect Glu-dependent behaviors from positions distal to glutamatergic circuits. Indeed, our focused study of GLT-3, one of the distally expressed GluTs, shows that despite this distance, GLT-3 function can balance the activity mediated by synaptic release and synaptic receptors. The effects of distal GluTs on glutamatergic circuits support that Glu diffusion outside the vicinity of the synapse is a critical factor in C. elegans neurotransmission. Together with the presynaptic localization of neuronal GluTs, these observations suggest an unusual strategy for Glu clearance in C. elegans.

A NEW SPECIES OF OOCHORISTICA (EUCESTODA: CYCLOPHYLLIDEA) PARASITE OF CTENOSAURA OAXACANA (REPTILIA: IGUANIDAE) FROM MEXICO

Oochoristica whitfieldi n. sp., parasitizing the intestine of the Oaxacan black iguana Ctenosaura oaxacana (Kohler and Hasbun, 2001), in Ruinas de Guiengola, Oaxaca state, Mexico, is described. The new species can be distinguished from all 4 congenera infecting Iguanidae in the neotropical realm in possessing a lower mean number of testes (122 in O. acapulcoensis Brooks, Pérez-Ponce de León, and García-Prieto, 1999; 62 in O. guanacastensis Brooks, Pérez-Ponce de León, and García-Prieto, 1999, and 95 in O. leonregagnonae Arizmendi-Espinosa, García-Prieto, and Guillén-Hernández, 2005, vs. 35 in O. whitfieldi), and a wider scolex (0.450-0.600, 0.475-0.537, 0.5-0.8, vs. 0.25-0.26, respectively). Oochoristica iguanae Bursey and Goldberg, 1996 differs from the new Mexican species in having a longer strobila (60-110 mm vs. 14.4-33.7 mm, respectively), fewer ovarian sublobes (6 vs. 11-17), and a cirrus pouch that hardly reaches excretory canals (whereas in O. whitfieldi the cirrus pouch widely overpasses these canals).

Genes Required for Osmoregulation and Apical Secretion in Caenorhabditis elegans

Few studies have investigated whether or not there is an interdependence between osmoregulation and vesicular trafficking. We previously showed that in Caenorhabditis elegans che-14 mutations affect osmoregulation, cuticle secretion, and sensory organ development. We report the identification of seven lethal mutations displaying che-14-like phenotypes, which define four new genes, rdy-1-rdy-4 (rod-like larval lethality and dye-filling defective). rdy-1, rdy-2, and rdy-4 mutations affect excretory canal function and cuticle formation. Moreover, rdy-1 and rdy-2 mutations reduce the amount of matrix material normally secreted by sheath cells in the amphid channel. In contrast, rdy-3 mutants have short cystic excretory canals, suggesting that it acts in a different process. rdy-1 encodes the vacuolar H+-ATPase a-subunit VHA-5, whereas rdy-2 encodes a new tetraspan protein. We suggest that RDY-1/VHA-5 acts upstream of RDY-2 and CHE-14 in some tissues, since it is required for their delivery to the epidermal, but not the amphid sheath, apical plasma membrane. Hence, the RDY-1/VHA-5 trafficking function appears essential in some cells and its proton pump function essential in others. Finally, we show that RDY-1/VHA-5 distribution changes prior to molting in parallel with that of actin microfilaments and propose a model for molting whereby actin provides a spatial cue for secretion.

Critical roles for excretory-secretory cysteine proteases during tissue invasion of Paragonimus westermani newly excysted metacercariae

Paragonimus westermani is a trematode parasite, which causes pulmonary and/or extrapulmonary granulomatous disease in humans. Successful invasion of the host tissue is critical for the survival of this tissue-invasive parasite. The enzymatic hydrolysis of host proteins is clearly a prerequisite of this process. In this study, we have investigated the functional roles of the excretory-secretory cysteine proteases of P. westermani newly excysted metacercariae (PwNEM) in tissue invasion. The 27 and 28 kDa enzymes (PwMc27 and PwMc28) purified from PwNEM excretory-secretory products (ESP), preferentially degraded fibrillar proteins, but not globular proteins. PwMc28 significantly facilitated the invasion of PwNEM into mouse peritoneum, whereas a diffusible cysteine protease inhibitor, trans-epoxysuccinyl-L-leuciloamido-(4-guanidino) butane (E-64) inhibited this process dose-dependently. Two distinct isoforms of PwMc28 (PwMc28a and PwMc28b), which exhibited two amino acid differences in their mature domains, were identified by tandem mass spectrometry and sequence analysis. Both enzymes were localized at the tegument on the anterior border and on the oral sucker, which suggests excretion-secretion via exocytosis or via the excretory canal network. The mRNA transcripts of PwMc28a and b were expressed abundantly during the active invasion/migration through the host's tissues, suggesting their relevant function to tissue invasion/migration in the definitive host.

A NEW SPECIES OF OOCHORISTICA (EUCESTODA: CYCLOPHYLLIDEA) PARASITE OF CTENOSAURA PECTINATA (REPTILIA: IGUANIDAE) FROM OAXACA, MEXICO

During January 2002, 3 specimens of an undescribed species of Oochoristica Lühe, 1898, were collected in Ctenosaura pectinata (Wiegmann, 1834) from Santa Mará Mixtequilla, Oaxaca, Mexico. Oochoristica leonregagnonae n. sp. differs from 71 of 82 species of the genus by its large number of testes (78-112 [95] vs. less than 65 per proglottid, respectively). In addition, the numerous ovarian lobes (31-79 [51]) possessed by the new species distinguish it from the other 10, with a maximum of 20 ovarian lobes. The new species differs from Oochoristica acapulcoensis Brooks, Pérez-Ponce de León and García-Prieto, 1999, which also infects C. pectinata in Mexico, by the presence of numerous staining granules throughout the parenchyma of the scolex in the latter species; likewise, testes in O. acapulcoensis reach and even overpass the excretory canals, whereas in the new species they are limited to the central region between these tubules.

Caenorhabditis elegans as a Model to Study Renal Development and Disease

The nematode Caenorhabditis elegans has no kidney per se, yet "the worm" has proved to be an excellent model to study renal-related issues, including tubulogenesis of the excretory canal, membrane transport and ion channel function, and human genetic diseases including autosomal dominant polycystic kidney disease (ADPKD). The goal of this review is to explain how C. elegans has provided insight into cilia development, cilia function, and human cystic kidney diseases.

A preliminary Histochimecal study on proteins, lipids, and oxygen-deficient ribosomal DNA in Khawia grypi

In this research, a histochemical study was undertaken on a caryophyllidian , Khawia grypi, recently described from Barbus grypus .The materials detected were: protein using mercuric bromophenol blue, lipids using Sudan black B , deoxyribonucleic acid using Feulgen reaction, (t is recovered from the results that protein and lipids are present in large quantities in the tegument , muscle bundles, mesenchyma and excretory canals while DNA was present in these organism in reasonable quantities, however, it was more abundant in the mesenchyma. The reproductive organs have reacted in different levels after applying the three techniques , protein and lipids were abundant or moderate in these organs, while in cirrus pouch lipid was scarce. The gonad high content of the protein indicates the high physiological activities of these organs such as gametogenesis, supply the nutrients and metabolites transport.

Ultrastructure of the body wall of infective larvae of Cystidicoloides ephemeridarum (Nematoda, Cystidicolidae) from mayflies

Scanning and transmission electron microscopic examinations of tissue-dwelling third-stage larvae of the nematode Cystidicoloides ephemeridarum from the intermediate host (Ephemera danica) were carried out with respect to the morphological changes in the body wall associated with the transfer from the intermediate to the definitive host. The ultrastructure of the cephalic end and zonation of the somatic cuticle of infective larvae basically correspond with those of adults. The somatic cuticle is composed of a fuzzy epicuticle, an outer and inner cortical zone, a median zone and a basal zone consisting of three subzones. Globular bodies are absent from the median zone of the infective larvae. The lateral hypodermal cords of the infective larvae are cellular, consisting of a median cell enclosed by two sublateral cells. The excretory canal is present within each of the lateral cord in both the infective and adult stages. Walls of the excretory canals contain Golgi-derived vesicles which communicate with the lumen of the canal. Large deposits of glycogen, suggesting anaerobic respiration, are present in the hypodermal cords and noncontractile parts of the muscle cells of the third-stage larvae within the intermediate host.

A C. elegans CLIC-like protein required for intracellular tube formation and maintenance.

The Caenorhabditis elegans excretory canal is composed of a single elongated and branched cell that is tunneled by an inner lumen of apical character. Loss of the exc-4 gene causes a cystic enlargement of this intracellular tube. exc-4 encodes a member of the chloride intracellular channel (CLIC) family of proteins. EXC-4 protein localizes to various tubular membranes in distinct cell types, including the lumenal membrane of the excretory tubes. A conserved 55-amino acid domain enables EXC-4 translocation from the cytosol to the lumenal membrane. The tubular architecture of this membrane requires EXC-4 for both its formation and maintenance.

A new species of Mathevotaenia (Cestoda: Anoplocephalidae) and other tapeworms from marsupials in Argentina.

Cestodes are reported from Didelphis albiventris Lund, 1840 and Micoureus cinereus Temminck, 1824 (Marsupialia: Didelphidae) in Argentina. These include a new species of Mathevotaenia Akhumyan, 1946 (Cestoda: Anoplocephalata) as well as M. bivittata (Janicki, 1904) and an unknown hymenolepidid cestode. Mathevotaenia argentinensis n. sp. is characterized by a relatively narrow strobila, 18-37 mm in total length and 1.0-1.5 mm in maximum width, 135-163 craspedote proglottids, 19-27 testes, and a muscular genital atrium. This species differs from M. didelphidis (Rudolphi, 1819) in the disposition of the genital ducts between the excretory canals and in the entrance of the vagina into the genital atrium posterior to the cirrus pouch; from M. paraguayae Schmidt and Martin, 1978 in the disposition of the genital ducts, absence of a seminal receptacle, and presence of an armed cirrus; and from M. boliviana Sawada and Harada, 1986 and M. pennsylvanica Chandler and Melvin, 1951 in the presence of an armed cirrus. Linstowiines appear to be the dominant cestodes in New World marsupials, with M. bivittata representing the most prevalent and widely distributed species. The hymenolepidid is the first record of this family in Neotropical marsupials.