Yongsan Zeng

Two new species of Schistonchus (Nematoda: Aphelenchoididae) associated with Ficus hispida in China

Two new nematode species of the genus Schistonchus were recovered from syconia from a single Ficus hispida caprifig tree in Guangzhou, China. They are described herein as Schistonchus guangzhouensis n. sp. and S. centerae n. sp. Schistonchus guangzhouensis n. sp. is characterised by possessing the longest postuterine sac (PUS) of all currently described females in the genus (84-148 μm or >3.5 vulval body diam. (VBD) long), excretory pore situated near the level of the metacorpus, two pairs of subventral papillae on the male tail, and unique recurved and mitten-shaped spicules. Schistonchus centerae n. sp. is characterised by a unique fusiform tail tip and short PUS (8-20 μm or <1.0 VBD long) in reproductive females, excretory pore located near the head, spicules with an indistinct rostrum, male tail with three pairs of papillae, and broadly truncate tail tip. Both new species were easily differentiated from each other and other members of the genus for which sequences of the D2/D3 expansion segments of the large subunit rRNA gene (LSU) and partial small subunit rRNA gene (SSU) were available. Phylogenetic analysis also supported a monophyletic Schistonchus within a well-supported clade of Aphelenchoididae (sensu Hunt, 1993) and shared a most recent common ancestor with Aphelenchoides and Laimaphelenchus.

A review of the taxonomy, phylogeny, distribution and co-evolution of SchistonchusCobb, 1927 with proposal of Ficophagusn. gen. and Martinineman. gen. (Nematoda: Aphelenchoididae)

The purposes of this paper are to clarify the taxonomic status of the fig-pollinating wasp associate Schistonchus sensu lato(Nematoda: Aphelenchoididae) and to suggest directions for future research on the systematics, life history and ecology of the group. Molecular phylogenetic analyses suggest that Schistonchus s.l.is polyphyletic, and the composition of the three major clades is outlined, together with information on nematode morphology, plant host species, associated pollinating wasp species, and distribution. Biological information and collection data is presented for Schistonchus s.l.from Ficussycones (Moracea) in Africa, Australia, Asia and Central America, and its putative phylogeny is discussed based on molecular and morphological evidence. Both wasps and figs are millions of years old and have worldwide distribution in tropical areas, i.e., opportunities for Schistonchus s.l.-like nematodes to have evolved could have occurred more than once. In addition, figs and their pollinating wasps have variable life histories, which could have provided opportunities for Schistonchus s.l.to also develop different life histories. However, these histories occur inside fig sycones and in association with wasps, which has apparently led to evolutionary convergence and extreme morphological conservatism. Diagnostic characters and their states, derived from examination of described species and morphospecies of Schistonchus s.l.and informed by molecular phylogenetic inferences, are discussed and illustrated. Schistonchus sensu strictois redefined, and Ficophagusn. gen. and Martinineman. gen. are proposed. Schistonchus s.s.is morphologically characterised by having the excretory pore opening in the region of, or posterior to, the metacorpus; Ficophagusn. gen. by having the excretory pore opening very near the cephalic region; and Martinineman. gen. by having it opening at the anterior end of the metacorpus. Several species of Schistonchus s.s.have a labial disc, but there is no evidence of this in either Ficophagusn. gen. or Martinineman. gen.

Acrostichus rhynchophori n. sp. (Rhabditida: Diplogastridae): a phoretic associate of Rhynchophorus cruentatus Fabricius and R. palmarum L. (Coleoptera: Curculionidae) in the Americas.

Acrostichus dauer larvae (JIII) were recovered during dissections of the palmetto weevil, Rhynchophorus cruentatus, from southern Florida, and the palm weevil, R. palmarum, from Colombia, Costa Rica and Trinidad. Based upon morphological and molecular studies, the four isolates are conspecific and are described herein as A. rhynchophori n. sp. Acrostichus rhynchophori n. sp. is characterised by narrow, flap-like dorsal tooth, female gonads not reflexed to the level of the vulva, male spicule and gubernaculum morphology, i.e., spicule with small and indistinct manubrium embedded in lamina/calomus complex, strong expansion just posterior to manubrium and smoothly curved and smoothly tapered lamina/calomus complex, and gubernaculum with claw-like anterior end in lateral view and three distal branches in ventral view. The new species is distinguished from A. superbus by morphology of the spicule and gubernaculum. Type specimens of four other Acrostichus species, originally described from bark beetles from North America, i.e., A. concolor, A. gubernatus, A. ponderosus and A. taedus, were re-examined and photo-documented.

Schistonchus hirtus n. sp. (Nematoda: Aphelenchoididae), an associate of Ficus hirta in China

A nematode recovered from syconia of Ficus hirta from Guangzhou, P. R. China, during a survey of nematode biodiversity from 2007 to 2009, is described herein as Schistonchus hirtus n. sp. and is differentiated by a combination of morphological characters, including excretory pore (EP) located near the metacorpus, a short post-uterine sac (PUS) (0.5 vulval body diam. (VBD) long), rose thorn-shaped spicules, amoeboid sperm, absence of gubernaculum, three pairs of subventral papillae on the male tail, host-Ficus and host-wasp species and DNA sequence data. Morphologically, S. hirtus n. sp. is close to S. centerae, S. altermacrophylla, S. aureus, S. laevigatus and S. virens based upon the length of the PUS (about 0.5 VBD long). However, the relative position of the EP in S. hirtus n. sp. is very different from these species (near metacorpus vs near head). With regard to the EP character, S. hirtus n. sp. is very similar to S. macrophylla, S. guangzhouensis and S. caprifici where the EP is at metacorpus level. However, S. hirtus n. sp. differs from S. macrophylla and S. guangzhouensis by possessing a shorter PUS and smaller spicules, and differs from S. caprifici by a shorter female stylet and smaller spicules. Schistonchus hirtus n. sp. was easily differentiated from other sequenced species by the proportion of parsimony informative changes in the partial small subunit rRNA gene (SSU) and D2/D3 expansion segments of the large subunit rRNA gene (LSU). Phylogenetic analysis with SSU sequences suggests that S. hirtus n. sp. is in a highly supported monophyletic clade with Aphelenchoides and Laimaphelenchus and is polyphyletic to other sequenced Schistonchus species. With LSU sequence data, it forms a clade with S. caprifici and they appear polyphyletic relative to S. guangzhouensis, S. centerae, S. aureus, S. laevigatus and S. virens.

Acrostichus puri n. sp. (Nematoda: Diplogastridae), a phoretic associate of Augochlora pura mosieri Cockerell (Hymenoptera: Halictidae).

Acrostichus puri n. sp., isolated from the body of a sweat bee, Augochlora pura mosieri, is described and figured. The new species is morphologically, molecularly and biologically very similar to A. halicti, i.e., these two species share a very complicated gubernaculum structure, distally hooked spicules with a triangular flap-like rostrum, stomatal polymorphism and synchronised associations with halcitid bees. The new species can be distinguished from A. halicti by its spicule morphology, distinctive squared manubrium and sharply bent (= ca 90° or L-shaped) distal tip vs an indistinctive rounded manubrium and a strongly recurved (= ca 180° or U-shaped) distal tip; gubernaculum with narrower, longer, anterior part and more complex posterior part than A. halicti, and tail of both sexes, with a long and filiform spike on the male or female tail vs a short spike (male) or conical tail (female). These two species also differ from each other by significant molecular sequence differences in SSU (2.0%), D2/D3 LSU (4.5%) and mtCOI (9.2%), and are reproductively incompatible in mating tests.

Acrostichus megaloptae n. sp. (Nematoda: Diplogastridae), a phoretic associate of Megalopta spp. (Hymenoptera: Halictidae) in Central America

Adults of the dusk-flying and rotting wood-nesting bees Megalopta genalis and/or M. ecuadoria were collected at Barro Colorado Island, The Smithsonian Tropical Research Institute (BCI, STRI), Panama and La Selva, Costa Rica, and examined for nematodes. Nematodes were recovered as dauer juveniles from the Dufours gland of female bees and aedeagus of male bees. Adult nematodes isolated from M. genalis (BCI and La Selva) and M. ecuadoria (BCI) were successfully cultured and kept in the laboratory. All three populations were used for morphological observations and molecular analyses and were identified as a new species that is described herein as Acrostichus megaloptae n. sp. It is characterised by its stomatal morphology, possession of six triangular cuticle flaps covering stomatal opening, duplicated cheilo- and gymnostomatal walls, large dorsal tooth and sclerotised ventral stegostomatal ridges, female with vulval flap, male spicule and gubernaculum morphology, i.e. , relatively straight spicule with oval-shaped manubrium, rounded flap-like rostrum and separated and strongly ventrally curved spicule with bifurcate tip, gubernaculum L-shaped in lateral view and anchor-shaped in ventral view, and filiform tail of both sexes. Sequences from the three A. megaloptae n. sp. geographical/host isolates were not significantly different and molecular phylogenetic analysis and biological and morphological comparisons place the new species close to A. halicti from Halictus ligatus and A. puri from Augochlora pura from North America, although the new species is distinguished from A. halicti and A. puri based upon its stomatal morphology of males and females, male spicule and gubernaculum morphology and female vulval structure.

Ultrastructure and life history of Myolaimus byersi n. sp. (Myolaimina: Myolaimidae), a phoretic associate of the crane fly, Limonia schwarzi (Alexander) (Limoniidae), in Florida

Myolaimus byersi n. sp., a phoretic associate of the crane fly, Limonia (Rhipidia) schwarzi (Diptera: Limoniidae), was recovered from moist and decaying tissue from the crown shaft of a living spindle palm, Hyophorbe verschaffeltii, in southern Florida and is described herein. Dauers were carried in the abdominal folds of male and female L. schwarzi. Examination of the highly mobile crane fly larvae and pupae confirmed that the dauers were externally associated with the cuticle. Dauers from crane flies were culturable to adults on 1/20 strength TSB agar. The association appears to be relatively host specific. SEM studies, early embryonic development, dauers, molecular data and TEM ultrastructural comparisons of the stoma, sensory structures and sperm are used to discuss the relative placement of Myolaimus within the Nematoda. The stoma resembles diplogastrids in being strongly anisomorphic with an enlarged dorsal sector of the stegostom, yet also resembles rhabditids in having three triangular flaps in the metastegostom and matches cephalobs and panagrolaims in having a pharyngeal collar with two sets of three interradial muscles followed by two sets of six adradial muscles. The ultrastructure of the cheilostom epidermis shows a high degree of conservation with several Rhabditida. The sperm of M. byersi n. sp. is nearly identical to that of Caenorhabditis elegans. In early cell division, M. byersi n. sp. is closest to Parascaris equorum followed by C. elegans. Myolaimus apparently represents a divergent lineage that has followed a non-coalescing trajectory for a long time, allowing it to retain some highly conserved characters while also developing some surprisingly unique features, such as a baggy cuticle and males that lack a gubernaculum or spicules.

Ficotylus laselvae n. sp. (Tylenchomorpha: Anguinidae) associated with Ficus colubrinae in Costa Rica

Ficotylus laselvae n. sp. was recovered from under the bracts of figs (syconia) of Ficus colubrinae from La Selva, Costa Rica, during a survey of nematode rainforest biodiversity and is described herein. This is only the second report of an association between the nematode suborder Tylenchina and the sycones of figs. Previous reports of most nematode associates of the sycones of figs have been from the lumen and involved transmission by female fig wasp pollinators (Agaonidae) during pollination/oviposition (e.g., Schistonchus and Parasitodiplogaster spp.). The association between F. laselvae n. sp. and Ficus colubrinae may involve an invertebrate host, but none was recovered from dissections of the bracts during this study. It is also possible that this is a rainforest understory nematode that feeds ectoparasitically in protected areas on the aerial parts of F. colubrinae. Molecular analysis using near-full-length sequences of the small subunit (SSU) rRNA and D2-D3 expansion segments of the large subunit (LSU) rRNA genes of Ficotylus laselvae n. sp. suggests that it is a member of the suborder Tylenchina (infraorder: Tylenchomorpha; family: Anguinidae) and that the closest sequenced species is F. congestae from the lumen of sycones of Ficus congesta from Queensland, Australia. Although both nematode species are associated with figs, they are morphologically divergent, suggesting that the different micro-niches that they fill provide different selective pressures for evolution of differing morphological characters or they represent different life history morphotypes of a dicyclic genus.

Bradynema listronoti n. sp. (Nematoda: Allantonematidae), a parasite of the carrot weevil Listronotus oregonensis (Coleoptera: Curculionidae) in Quebec, Canada

Bradynema listronoti n. sp. was collected from the haemocoel of adults and the environment of the carrot weevil, Listronotus oregonensis in Quebec, Canada. It is the first species of Bradynema to be reported from weevils and is described and illustrated herein. Bradynema listronoti n. sp. appears to be closest to B. trixagi because of the shared characteristic of a peloderan bursa in males which is not present in the other seven described species in the genus. Bradynema listronoti n. sp. can be differentiated from all members of the genus by the possession of a degenerate, but sometimes visible, stylet remnant, non-degenerate pharynx in males and by the often dorsally-curved C-shaped body (ventral side is convex) of parasitic females. The vestigial stylet in all stages argues for placement of B. listronoti n. sp. within the genus Bradynema, but some characteristics, such as a non-degenerate pharynx in males, suggest placement in a new genus or affinities with other genera in the Allantonematidae, e.g., Allantonema. Molecular analysis of the near full length SSU, D2/D3 expansion segments of the large subunit (LSU) rDNA and partial mitochondrial DNA COI (mtCOI) suggest that this nematode is unique and D2/D3 analysis supports monophyly with B. rigidum, the only other member of the genus to be sequenced.

Morphological and molecular characteristics of Parasitodiplogaster religiosae n. sp. (Nematoda: Diplogastrina) associated with Ficus religiosa in China

A new nematode species of the genus Parasitodiplogaster was recovered from syconia of Ficus religiosa at the Guangxiao Temple, Guangzhou, China. It is described herein as P. religiosae n. sp. and is characterised by possessing the longest and thinnest spicule of all currently described males in the genus, an elongated laterally “ε-shaped” and ventrally rhomboid-like gubernaculum, a stoma without teeth, consisting of a ring-like cheilostom with indistinct anteriolateral projections, a tube-like gymnostom and a funnel-like stegostom, monodelphic with a mean vulval position of 66%. There are three pre-cloacal and six post-cloacal male genital papillae with the arrangement P1, P2, P3, (C, P4), P5, P6d, P7, P8, P9d, Ph. This new species was easily differentiated from other members of the genus by DNA sequences of partial small subunit rRNA gene (SSU) and the D2-D3 expansion segments of the large subunit rRNA gene (LSU). Phylogenetic analysis also corroborated its reasonable placement within a well-supported monophyletic clade with other Parasitodiplogaster species and within the australis-group that includes P. australis and P. salicifoliae that are all associates of fig wasp pollinators (Platyscapa sp.) of figs of the subsection Urostigma.