The ultrastructure of the spermatozoon ofParadynomene tuberculata Sakai, 1963 (Crustacea,Brachyura, Dynomenidae): Synapomorphies with dromiid sperm

The dynomenid spermatozoon, exemplified here byParadynomene tuberculata, resembles the spermatozoa of the Dromiidae, Homolidae and lyreidine raninoids and differs markedly from those of other crabs (the heterotreme, thoracotremes, raninines and raninoidines) in the depressed, discoidal form of the acrosome and the capitate form of the perforatorium. Four or five apparent dynomenid—dromiid sperm synapomorphies are recognizable. (1) Dynomenids (P. tuberculata) and dromiids differ from homolids and lyreidines in the greater depression of the acrosome (ratio of length to width=0.3); (2) the capitate head of the perforatorium is bilaterally prolonged inP. tuberculata as in dromiids though symmetrical in homolids; (3) dynomenid and dromiid sperm lack the—albeit variably developed—posterior median process of the nucleus seen in homolids, anomurans, raninoids and lower heterotremes; (4)P. tuberculata, like dromiids and less distinctly homolids, has an apical protuberance of subopercular material through the opercular perforation, unknown in other crabs, being distinct from the apical button of thoracotreme sperm; (5) a less certain synapomorphy is the anterolateral electron-pale peripheral zone of the acrosome. These synapomorphies endorse a sister-group relationship of dynomenids and dromiids,P. tuberculata sperm differs notably from the sperm of dromiids in the more complex zonation of the acrosome. The perforatorium lacks the radial rays (“spiked wheel”) of homolid sperm and does not show the “amoeboid” form seen in lyreidines. Absence of internal corrugations of the perforatorial chamber is a major difference from all examined raninids. Centrioles are only very tentatively identifiable. Nuclear arms are absent in glutaraldehyde fixed spermatozoa ofP. tuberculata and have not been observed in the dromiidPetalomera lateralis but are present as three small radial vertices in the dromiidDromidiopsis edwardsi and in homolids.P. tuberculata resemblesPetalomera lateralis in the large size of the sperm nucleus relative to the acrosome compared withD. edwardsi and homolids.     

Relationship of Homolidae and Dromiidae: Evidence from Spermatozoal Ultrastructure (Crustacea,Decapoda)

Abstract The homolid spermatozoon, as exemplified by Homolasp., Paromolasp. and Paromola petterdi, differs markedly from spermatozoa of crabs of the Heterotremata–Thoracotremata assemblage but agrees with the sperm of dromiids, in the strongly anteroposteriorly depressed acrosome (apomorphy?) and the capitate form of the perforatorium (a major synapomorphy seen nowhere else in the Crustacea). These similarities support inclusion of the Dromiidae and Homolidae in a single grouping, the Podotremata. The homolid perforatorium differs from that of dromiids in the autapomorphic spiked–wheel form of the anterior expansion. Homolid spermatozoa show nuclear arms symplesiomorphic of all investigated crabs (small or questionably sometimes absent in Dromiidae), and corresponding loss of purely microtubular arms seen in other reptants. Homolid sperm agree with those of dromiids (synapomorphy?), raninids, higher heterotremes and thoracotremes (homoplasies?) but differ from lower heterotremes, in lacking microtubules in the nuclear arms. A posterior median process of the nucleus in homolids, not seen in dromiids, is shared with anomurans and lower heterotremes. No features in the ultrastructure of homolid or dromiid sperm have been detected which associate them exclusively with either the Raninidae or the heterotreme and thoracotreme Brachyura.     

An Ultrastructural Study of Spermatozoa of the Majidae with Particular Reference to the Aberrant Spermatozoon of Macropodia longirostris (Crustacea,Decapoda, Brachyura)

A total of 17 species, in 14 genera of majids have been examined for sperm ultrastructure. The present account describes the sperm of six of these species, in two subfamilies: Pisinae—Sphenocarcinus orbiculatus and Sphenocarcinus stuckiae and Inachinae—Cyrtomaia furici, Grypacheus hyalinus, Platymaia rebierei and Macropodia longirostris. M. longirostris has the only eubrachyuran sperm in which the acrosome is known to depart radically from a subspheroidal form. The acrosome is semilunar in shape and is bordered by a very thin layer of cytoplasm and an unusually uniform, narrow band of chromatin. The apical surface of the acrosome is almost flat, though slightly concave, whereas the posterior surface forms a hemisphere, and is almost completely occupied by the thin, centrally perforate, electron dense operculum. The bulk of the acrosome consists of a homogeneous, moderately electron dense outer acrosome zone. This surrounds a small inner acrosome zone internal to which is an ellipsoidal, pale perforatorium capped by a central acrosome zone. Majid sperm are distinguished by a flattened and/or centrally depressed operculum; a further characteristic is that the pointed perforatorium is relatively short and frequently does not reach the operculum. They vary inter alia with regard to presence or absence of a posterior median process and, apparently, of centrioles and of microtubules in the nuclear arms, and in the number of these arms. Perforation of the operculum, seen in the Pisinae, is not constant in the Inachinae. Spermatozoal ultrastructure offers no certain support for a close relationship of majids with parthenopids or hymenosomatids.     

Ultrastructural comparison of the spermatozoa of Ranina ranina (Oxystomata) and of other crabs exemplified by Portunus pelagicus (Brachygnatha) (Crustacea,Brachyura)

Summary Features shared between the sperm of Ranina ranina and of the so-called higher Brachyura (the Oxyrhyncha — Cancridea — Brachygnatha assemblage, OCB) include: (1) the large subspheroidal acrosome (a synapomorphy of the Raninoidea + the OCB contrasting with the disc-shaped Dromioidea acrosome); (2) enclosure of the acrosome by a thin layer of cytoplasm which is in turn cupped by the nucleus; (3) extension of the nucleus as lateral arms and as a posterior median process (this process is absent in the more advanced families, including portunids); (4) extension of the cytoplasm into the basal region of each nuclear arm; and (5) topographical equivalence and presumed homology of components of the acrosome, viz. the electron dense capsule; inner and outer dense zones surrounding the longitudinal axis; peripheral vesicular contents; a perforate or, in Portunus, an imperforate, apical operculum; subopercular- or subcap-zone; and a basally open subacrosomal chamber enclosing perforatorial material. Significant differences of the Ranina sperm from those of the OCB, including Portunus, are: (1) anterior termination of the subacrosomal space at the equator of the acrosome and its conical form (plesiomorphy?), in the latter assemblage reaching the operculum; (2) differentiation within the subacrosomal material of a coiled, filiform putative perforatorium (plesiomorphy or apomorphic homoplasy with Anaspidacea?) whereas the entire subacrosomal contents in the OCB form a stout perforatorial rod; (3) subdivision from the acrosome vesicle in Ranina of a posterior acrosomal chamber with differentiation of the walls of this, lining the subacrosomal chamber, as longitudinal corrugations (Raninoidea autapomorphies); and (4) plesiomorphic persistence of numerous well developed, simple mitochondria in contrast to their degeneration, with greater development of a myelin-like lamellar complex, in the OCB. Spermatologically, the Raninoidea thus appear to be the plesiomorphic adelphotaxon of the Oxyrhyncha — Cancridea — Brachygnatha assemblage.Abbreviations a acrosome - ar acrosomal rays - asr anterior subacrosomal region - c centriole - ca capsule - cab central acrosomal body - ce cytoplasmic extension into arm - co corrugations - DNA DNA of arm - dt degenerating microtubules - ine disrupted inner nuclear envelope - iz inner dense zone - I part of lamellar complex - la lateral arm - m mitochondrion - npm combined nuclear and plasma membranes - o operculum - oz outer dense zone - p perforatorium - pv peripheral contents of acrosome vesicle - pcv posterior chamber of acrosome vesicle - pmp posterior median process - pp putative perforatorium - psr posterior subacrosomal region - sz subopercular zone - tr thickened ring     

Spermiogenesis and sperm structure in the crabUca tangeri (Crustacea,Brachyura), with special reference to the acrosome differentiation

Summary Early spermatids of the crabUca tangeri consists of the nucleus of granular chromatin and the cytoplasm, which contains a proacrosomal vesicle in close association with membrane lamellae. In the mid spermatids an invagination of the acrosomal vesicle membrane gives rise to the formation of the perforatorium, a spindle-shaped tubule which encloses tubular membranous structures. The pair of centrioles located at the base of the acrosome is not directly involved in perforatorial differentiation. The acrosomal vesicle shows a heterogeneous content composed of the operculum, the thickened ring, and three layers of different materials concentrically arranged around the perforatorium. During the late spermatid stage the nuclear profile differentiates numerous slender arms and the chromatin arranges into fibers. Membranous tubules from the cytoplasm become incorporated into the tubular structures of the perforatorium. The mature spermatozoon has the typical structure of the branchyuran sperm, with a complex acrosome, cupped by the nucleus, and a thin cytoplasmic band intervening between the former main elements. The centrioles are degenerate. The nuclear arms are unusually numerous (more than 20) and lack microtubules or microtubular derivatives.     

Ultrastructure of the spermatozoa ofCorystes cassivelaunus (Corystidae),Platepistoma nanum (Cancridae) andCancer pagurus (Cancridae) supports recognition of the Corystoidea (Crustacea, Brachyura, Heterotremata)

A combination of characters, not individually unique, possessed by the corystid,Corystes cassivelaunus, and the two cancrids,Platepistoma nanum andCancer pagurus, defines a corystoid-type of spermatozoon: the basally bulbous, anteriorly narrowing perforatorium, the extent of this almost to the plasma membrane through a widely perforate operculum, and the simple inner acrosome zone, lacking an acrosome ray zone. The sperm of the two cancrids are closely similar, that of the corystid differing, for instance, in the less pointed, and less tapered, form of the perforatorium. This relative uniformity of spermatozoal ultrastructure in the cancrid+corystid assemblage so far investigated supports inclusion of the two families in the superfamily Corystoidea by Guinot (1978). The combination of perforation of the operculum and absence of an acrosome ray zone (at least in a clearly recognizable form) are features of the Potamidae which possibly indicate that the latter family, modified for a freshwater existence, is related to the cancrid+corystid assemblage. Some elongation of the centrioles, apparent at least inCorystes, may be a further link with potamids in which they are greatly elongated. The coenospermial spermatophores of cancridoids are a notable difference from the cleistospermia of potamids; but the latter is probably an apomorphic modification for fertilization biology.     

北草蜥精子的超微结构--兼评不同类群蜥蜴精子形态的差异

应用透射电镜对北草蜥精子的超微结构研究结果表明,北草蜥精子头部顶体囊始终呈圆形,由皮质和髓质组成;顶体囊单侧脊的皮质与髓质问具电子透亮区;穿孔器1个,无穿孔器基板;具顶体下腔;细胞核长形,核内小管缺,核前电子透亮区缺,核肩圆。尾部颈段具片层结构。中段短,多层膜结构缺;纵切面上具2层线粒体;横切面上每圈线粒体6个;2组致密体,具连续的环状结构;线粒体与环状结构的排列模式：rs1／mi1、rs2／mi2;纤维鞘伸人中段,具终环。主段前面部分具薄的细胞质颗粒区;纤维3和8至主段前端消失;轴丝呈“9＋2”型。蜥蜴科内不同种类的线粒体数目不同,但都具有2组致密体。不同类群蜥蜴的顶体囊、顶体下腔、核前电子透亮区、穿孔器基板、核肩,以及线粒体与致密体的数目和排列方式等精子超微结构特征都为研究蜥蜴的系统发生提供了辅助信息。     

Sperm ultrastructure of the spider crab Maja brachydactyla (Decapoda: Brachyura)

This study describes the morphology of the sperm cell of Maja brachydactyla, with emphasis on localizing actin and tubulin. The spermatozoon of M. brachydactyla is similar in appearance and organization to other brachyuran spermatozoa. The spermatozoon is a globular cell composed of a central acrosome, which is surrounded by a thin layer of cytoplasm and a cup‐shaped nucleus with four radiating lateral arms. The acrosome is a subspheroidal vesicle composed of three concentric zones surrounded by a capsule. The acrosome is apically covered by an operculum. The perforatorium penetrates the center of the acrosome and has granular material partially composed of actin. The cytoplasm contains one centriole in the subacrosomal region. A cytoplasmic ring encircles the acrosome in the subapical region of the cell and contains the structures‐organelles complex (SO‐complex), which is composed of a membrane system, mitochondria with few cristae, and microtubules. In the nucleus, slightly condensed chromatin extends along the lateral arms, in which no microtubules have been observed. Chromatin fibers aggregate in certain areas and are often associated with the SO‐complex. During the acrosomal reaction, the acrosome could provide support for the penetration of the sperm nucleus, the SO‐complex could serve as an anchor point for chromatin, and the lateral arms could play an important role triggering the acrosomal reaction, while slightly decondensed chromatin may be necessary for the deformation of the nucleus. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.     

Fine structure of acrosome biogenesis and of mature sperm in the bivalve molluscs<Emphasis Type="Italic"> Glycymeris</Emphasis> sp. (Pteriomorphia) and<Emphasis Type="Italic"> Eurhomalea rufa</Emphasis> (Heterodonta)

Proacrosomal vesicles form during the pachytene stage, being synthetized by the Golgi complex in Glycymeris sp., and by both the Golgi and the rough endoplasmic reticulum in Eurhomalea rufa. During early spermiogenesis, a single acrosomal vesicle forms and its apex becomes linked to the plasma membrane while it migrates. In Glycymeris sp., the acrosomal vesicle then turns cap-shaped (1.8 μm) and acquires a complex substructure. In E. rufa, proacrosomal vesicles differentiate their contents while still at the premeiotic stage; as the acrosomal vesicle matures and its contents further differentiate, it elongates and becomes longer than the nucleus (3.2 μm), while the subacrosomal space develops a perforatorium. Before condensation, chromatin turns fibrillar in Glycymeris sp., whereas it acquires a cordonal pattern in E. rufa. Accordingly, the sperm nucleus of Glycymeris sp. is conical and elongated (8.3 μm), and that of E. rufa is short and ovoid (1.1 μm). In the midpiece (Glycymeris sp.: 1.1 μm; E. rufa: 0.8 μm), both species have four mitochondria encircling two linked orthogonal (Glycymeris sp.) or orthogonal and tilted (30–40°; E. rufa) centrioles. In comparison with other Arcoida species, sperm of Glycymeris sp. appear distinct due to the presence of an elongated nucleus, a highly differentiated acrosome, and four instead of five mitochondria. The same occurs with E. rufa regarding other Veneracea species, with the acrosome of the mature sperm strongly resembling that of the recent Mytilinae. Electronic Publication     

Morphology of the spermatozoa of the Microhylidae (Anura, Amphibia)

Microhylid spermatozoa show the autapomorphic condition of possessing a thin post-mitochondrial cytoplasmic collar. Their spermatozoa are apomorphic in several respects. They have lost the distinct nuclear shoulder, endonuclear canal and axial perforatorium observed in urodeles, caecilians and primitive frogs, possess a conical perforatorium and apomorphically lack any fibres associated with the axoneme. The spermatozoa of Cophixalus , however, differ in several respects from those of the other microhylids examined. Cophixalus spermatozoa are longer in almost all measurements, the acrosome vesicle is cylindrical and does not completely cover the putative perforatorium, the perforatorium is asymmetrical and composed of fine fibres, the nucleus is strongly attenuated and narrower, and the mitochondria are elongate. The absence of fibres associated with the axoneme is an apomorphic condition shared with the Ranidae, Rhacophoridae and Pipidae.     

Platyamoeba stenopodia. n. g., n. sp., a Freshwater Amoeba*

SYNOPSIS. Platyamoeba stenopodia n. g., n. sp., isolated from a lake in Alabama, is an amoeba with flattened form, usually more than 2.5 × as long as broad, the anterior half hyaline and the posterior half granular, with a single vesiculate nucleus at the posterior edge of the hyaline region. It forms a transitory floating stage with slender, hyaline pseudopods. Its cyst is spherical, uninucleate, with a smooth inner wall and a thinner, closely applied outer wall, which is often slightly wrinkled. Length of locomotive amoeba 15–36 μ diameter of cyst 7–11.5 μ Reproduction by binary fission with mesomitotic nuclear division, the nuclear membrane disappearing in prophase. The genus Platyamoeba is erected for amoebae including this organism; the type species is P. placida.     

Scanning electron microscopy of post-ejaculatory spermiogenesis in the tick Ornithodoros moubata

The final stages of spermiogenesis in ticks occur in the female genital tract. Scanning electron microscopy was used to follow the morphologic changes that occur in the sperm during this post-ejaculatory spermiogenesis in the African soft tick, Ornithodoros moubata, and to determine a time sequence for its occurrence in vivo. Characteristic features of the maturing and mature cell described include (1) differentiation and detachment of the operculum, (2) changes in cell shape corresponding to different developmental stages, (3) passive migration of the nucleus and acrosome from an anterior to a posterior position, and (4) eversion of that portion of the acrosomal canal containing the nucleus and acrosome. A possible fate for the remainder of the acrosomal canal is suggested by extrusion and detachment of spherical structures, the ‘posterior bubbles’, from the posterior end of the mature supermatozoon. A mechanism for cellular elongation resulting from contractions of the outer sheath is proposed.     

A dendrobranchiate, Peisos petrunkevitchi (Decapoda, Sergestidae), with reptant-like sperm: a spermiocladistic assessment

The spermatozoon of Peisos petrunkevitchi differs significantly from those of any of the investigated dendrobranchiates in the anterior fusiform acrosome, lacking a spike, and embedded in (instead of capping) the nuclear region. In contrast, the position of the acrosome and the internal arrangement of its contents, as well as the apomorphic presence of a pair of centrioles (absent in all known dendrobranchiate spermatozoa) at the base of the acrosomal perforatorium, indicate a close affinity between this sperm plan and that found in reptants, especially anomurans and brachyurans. Based on the present and previous observations on decapod spermatozoal ultrastructure, we review the phylogeny of dendrobranchiate spermatozoa in the perspective of most recent phylogenetic analyses of malacostracan crustaceans.     

Ultrastructure and relationships of spermatozoa of the freshwater crabs Potamon fluviatile and Potamon ibericum (Crustacea, Brachyura, Potamidae)

The spermatozoa of Potamon fluviatile and P. ibericum are virtually indistinguishable and do not support separate subgeneric rank ( Potamon and Pontipotamon , respectively). Synapomorphic with the spermatozoa of the South African freshwater crab Potamonautes perlatus Sidneyi are the elongation of the two centrioles and disposition of the centrioles almost parallel to each other, unknown elsewhere in the Brachyura, and reduction of the thickened ring (homoplasic with grapsids and gecarcinids). Other, probably synapomorphic, similarities of Potamon and Potamonautes include the wide inner acrosome zone, absence of a definite acrosome ray zone (homoplasic in other families) and the cleistospermial spermatophores. Further similarities, of questionable polarity, are the simple, not multilaminar, nuclear membrane and the tendency of the nuclear arms to wrap around the nucleus. Differences of Potamon from Potamonautes , which possibly support their present generic separation and give weak support to their former separate familial placement in the Potamidae and Potamonautidae respectively, are perforation of the operculum and the weak, rather than strong, development of a periopercular rim. Absence in Potamon and Potamonautes of an accessory opercular ring and a xanthid ring separates them from xanthids. No close affinities with other heterotreme families are seen but their assignment to the Helerotremata is not in doubt. Their spermatozoa lack two of the distinctive features of thoracotreme spermatozoa (apical button on the operculum and concentric lamellation of the outer acrosome zone). No clear correlates of spermatozoon structure with a freshwater existence are recognizable but reduction of the thickened ring possibly relates to peculiarities of the acrosome reaction. However, the production of spermatophores with single spermatozoa (cleistospermia) is possibly a device to prevent polyspermy and wastage of the small number of lecithotrophic eggs produced in potamids.     

Comparative ultrastructure of the spermatozoa of three crayfish species: Austropotamobius torrentium,Pacifastacus leniusculus,and Astacus astacus (Decapoda: Astacidae)

This study reports about the spermatozoal ultrastructure of three species of astacid crayfish, i.e., the stone crayfish Austropotamobius torrentium, signal crayfish Pacifastacus leniusculus, and noble crayfish Astacus astacus. The acrosome is a cup shaped and electron‐dense structure at the anterior of the spermatozoon and comprises three layers of differing electron densities filled with parallel filaments that extend from the base to the apical zone. The acrosome was significantly longer in A. astacus than in P. leniusculus and the shortest acrosome belongs to A. torrentium. The width of the acrosome was significantly narrower in A. torrentium than in P. leniusculus and the widest acrosome belongs to A. astacus. The L:W ratio was significantly greater in A. torrentium than in P. leniusculus and the lowest ratio belongs to A. astacus. Radial arms are visible on each side of the acrosome or nucleus in sagittal view and wrap around the spermatozoon. Each radial arm comprises a parallel bundle of microtubules arranged along the long axis within a sheath. The nucleus, with decondensed material, is located in the posterior of the cell. All parts of the spermatozoon are tightly enclosed within an extracellular capsule. Despite a well‐conserved general structure and similarity of pattern among these spermatozoa, differences in the dimensions of the acrosome within the studied species may be useful to help distinguish the different crayfish species. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.     

中国石龙子成熟精子的超微结构

利用透射电镜观察中国石龙子附睾成熟精子的超微结构。顶体囊前部扁平、由皮质和髓质组成 ,穿孔器中度倾斜、顶端尖 ,穿孔器基板塞子状 ,细胞核长形 ,核内小管缺 ,核前电子透亮区小 ,核肩圆 ,核陷窝锥形。颈段具片层结构 ,近端中心粒和远端中心粒的长轴呈直角 ,9束外周致密纤维与远端中心粒相应的 9束三联微管相联 ,向后与轴丝相应的 9束双联微管相联 ,中央纤维与 2个中央单微管相联。中段短 ,多层膜结构缺 ,含有线状嵴的柱状线粒体 ,不规则卵状致密体组成不连续的环状结构 ,纤维鞘伸入中段 ,具终环。线粒体与环状结构的模式为 :rs1 /mi1 ,rs2 /mi2 ,rs3/mi3,rs4 /mi4。主段前面部分具薄的细胞质颗粒区。纤维 3和 8至主段前端消失。轴丝呈“9 2”型。中国石龙子精子超微结构具有塞子状的穿孔器基板、致密体形成不连续的环状结构和纤维鞘始于ms2等特征与巨石龙子群和蜓蜥 -胎生群不同。没有发现石龙子科精子的独征     

Descriptions of Eumonhystera borealis n. sp., Sphaerolaimus occidentalis n. sp., and a Redescription of S. gracilis de Man 1876 (Nemata) from Bothnian Bay,Baltic Sea

The free-living nematodes Eumonhystera borealis n. sp., Sphaerolaimus occidentalis n. sp., and S. gracilis de Man 1876 from Bothnian Bay in the northern Baltic Sea are described and illustrated. Eumonhystera borealis n. sp. differs from other species by its small body size (314-393 μm), narrow body (a = 37-49), and large anterior amphids. In Sphaerolaimus occidentalis n. sp. the amphids are posterior to the buccal cavity, and it differs from other similar species by having two sclerotized rings in the posterior part of the buccal cavity. An intersex is reported for S. gracilis. Sphaerolaimus gracilis is cannibalistic or a predator of other species, with a preference for E. borealis n. sp. Sphaerolaimus occidentalis n. sp. coexists with S. gracilis at depths of 80 m but not at 12 m.     

Coulonia parva n. sp., a new species of Astropectinidae (Asteroidea; Echinodermata) from the Santonian (Upper Cretaceous) of Sierra de Montsech (southern Pyrenees, Spain)

A new astropectinid sea star,Coulonia parva n. sp., is described from the Santonian of the Sierra de Montsech, northern Spain. The single specimen shows part of a rather weathered ventral side. It is characterized by comparatively long arms (R/r approx. 3/1), with one row of actinals reaching far into the arms; inferomarginals on the interbrachial arc have deep fasciolar grooves that are less developed on the arms; there are no larger spines on adambulacrals and probably also on inferomarginals. Based on presence of deep marginal fascioles,C. parva n. sp. is inferred to have shared the capability for self-burial with the relatedC. platyspina Hess &Blake.      

Dicrocoeliidae (Trematoda: Digenea) of Australian mammals with description of Dicrocoelium antechini n. sp., Athesmioides aiolos n. g., n. sp. and Platynosomum burrman n. sp.

Dicrocoelium antechini n. sp. is described from the bile ducts of Antechinus swainsonii and A. stuartii (Marsupialia: Dasyuridae) from New South Wales. The species differs from all others in the genus in that the caecal bifurcation is well posterior to the ventral sucker and testes. Athesmioides aiolos n. g., n. sp. is described from Rattus fuscipes and R. lutreolus from New South Wales and from R. norvegicus, R. lutreolus and Pseudomys higginsi from Tasmania (all Rodentia: Muridae). The genus Athesmioides is characterised by the presence of unilateral vitelline follicles and an undivided caecum. Platynosomum burrman n. sp. is described from Isoodon macrourus (Marsupialia: Peramelidae) from the Northern Territory. It differs from other species in a combination of characters regarding the shape of the forebody, the arrangement of the gonads, the disposition of the uterus and the size of the eggs. The taxonomic status of Platynosomum australiense (Sandars, 1958), Brachylecithum insulare Angel & Pearson, 1977 and Brachylecithum hydromyos Angel & Pearson, 1977 are summarised. Records are presented of undescribed dicrocoeliids from the marsupials Petaurus breviceps, Planigale maculata and Dasyurus hallucatus and the murids Rattus fuscipes and Melomys sp.