Variation in Nymphon brevirostre (Hodge), and the status of N. rubrum (Hodge) (Arthropoda: Pycnogonida)

A series of morphometric analyses conducted on specimens of Nymphon brevirostre Hodge and Nymphon rubrum Hodge from British waters has shown that the characteristics variously used in the past to distinguish these two species are invalid. In this material these characteristics range from the extreme of the typical N. brevirostre form to that of the typical N. rubrum form, with most of the specimens exhibiting an intermediate morphology. Multivariate analyses showed no significant splitting of the material into two groups which might correlate to Hodge's two species. Protonymphon larvae from males of both typical extreme forms were morphologically identical. It is concluded that N. rubrum is a junior synonym of N. brevirostre, a variable species whose morphology tends towards the rubrum form as the animal grows.     

Salinity and temperature tolerance by Nymphon gracile (Leach) and Achelia echinata (Hodge) (Pycnogonida)

The tolerance of two species of pycnogonid, Achelia echinata (Hodge) and Nymphon gracile (Leach) to a range of salinities, temperatures and relative humidities has been examined. In most instances N. gracile is more resistant than A. echinata and indeed is found higher in the littoral zone during the warmer months and thus likely to be subjected to greater environmental fluctuation.     

Larvae of three sea spider species of the genus <Emphasis Type="Italic">Nymphon</Emphasis> (Arthropoda: Pycnogonida) from the White Sea

Larvae of three Nymphon species are described. For Nymphon brevirostre Hodge, 1863 and Nymphon micronyx Sars, 1888 protonymphon larvae are examined, larvae of N. micronyx have been studied for the first time. The fine external morphology of larvae is studied in detail using SEM methods; the internal structure of N. brevirostre protonymphon is additionally described. SEM data on external morphology and fine surface structures are given for several postembryonic stages of Nymphon grossipes Fabricius, 1780. Different types of postembryonic development are revealed in examined Nymphon species. N. brevirostre and N. micronyx have a “typical protonymphon” developmental pathway. A special developmental pathway named “lecithotrophic protonymphon” is suggested for N. grossipes and other Nymphonidae having large yolky eggs.     

Morphological variation in British Atherinids, and the status of Atherina presbyter Guvier (Pisces: Atherinidae)

A series of morphometric and meristic analyses conducted on specimens of sand smelt, Atherina , from populations around the British Isles, and including classic A. boyeri and A. presbyter forms, has shown that the characteristics variously used in the past to distinguish these two species are invalid. Multivariate analyses showed no significant splitting of the material into two groups which might correlate to these two species; classic A. boyeri and the very large Atlantic coast A. presbyter individuals represent the tails of a continuum of form. From these and published data, it is concluded that the A. boyeri morphology varies under the influence of conditions of temperature and salinity during embryo development, and the isolation of populations maintains comparative morphological distinctions resulting from local selection and random genetic drift.     

Postembryonic development of Nymphon unguiculatum Hodgson 1915 (Pycnogonida, Nymphonidae) from the South Shetland Islands (Antarctica)

Male specimens of the sea spider species Nymphon unguiculatum, carrying eggs, larvae and postlarvae in various stages of development, were collected off the South Shetland Island at water depths between 112 and 472 m in austral summer 2006/2007. Here, we describe the external morphology of four postembryonic stages (protonymphon, instar 1, instar 2, and instar 3) carried by these specimens. We found that (1) protonymphon larvae hatch from the eggs; (2) larvae and postlarval stages have yolk reserves and are characterized by a relatively large size (average body lengths of 0.46, 0.55, 0.65 and 0.73 mm in the successive stages); (3) postlarvae remain on the ovigerous legs of males during several moults; (4) a spinning apparatus is present; (5) the development of walking legs is sequential. The larval and postlarval development of N. unguiculatum is compared with that known from other pycnogonid species.     

Experiments on food preference and chemical sense in Pycnogonida

Food choice experiments were carried out with three species of pycnogonids: Nymphon rubrum, N. gracile , and Endeis spinosa.
Running sea-water that had circulated over different possible food-sources (hydroids, actiniarians, octocorals, synascidians) was offered to the pycnogonids at one side of a basin, pure sea-water or sea-water that had flowed over a different source of food at the other.
The experiments, though few in number, seemed to indicate that:
(1) Pycnogonids are capable of detecting the presence or absence of various coelenterate species.
(2) They are able to discriminate between different food-sources, i.e. the nature of the chemical substances produced by the food determines the degree of attraction.
(3) The preferential sequence for the three pycnogonids tested is: Nymphon rubrum prefers Dynamena over Tubularia and Laomedea ; these are preferred over Actinia and Metridium ; there is no attraction to Alcyonium. Nymphon gracile prefers Laomedea over Dynamena. Endeis spinosa prefers Laomedea over Dynamena ; these are preferred over Actinia ; there is no attraction to Morchellium.
(4) Experimental amputation of appendages indicates a high probability that the chemo-receptors of the pycnogonids are not located on the chelifores, palps, or ovigers. They may be located (a) all over the body, possibly in innervated epidermal bristles; and/or (b) in the distal part of the proboscis, bearing sensory setae; and/or (c) on the walking legs.     

The deep-water pycnogonids (Arthropoda: Pycnogonida) of the northeastern Atlantic Ocean

Over 2000 specimens of pycnogonid from deep-sea collections made in the northeastern Atlantic Ocean by IOS and SMBA between 1971 and 1994 have been analysed. Thirty-five species were identified, two being new to science, viz Nymphon akanthochoeros and an unnamed Anoplodactylus species. The deep-sea Pycnogonida of the northeastern Atlantic are reviewed using these data and records from the literature. Keys are presented for the six families represented by more than one species. The pycnogonid fauna of this area is characterized particularly by Paranymphon spinosum and Colossendeis clavata , with other dominant species including Colossendeis species, notably C. macenima , and Nymphon laterospinum, Anoplodactylus typhlops and A. arnaudae. Of the 54 species recorded below 200 m in the northeastern Atlantic, available evidence suggests that nine are 'endemic'. Relative distributions of the other species are discussed. A distinct change in the pycnogonid fauna with depth was found at around 1400 m. There is latitudinal separation of species groupings, shown most conspicuously by the shallower water species.     

Synopsis of a new collection of sea spiders (Arthropoda: Pycnogonida) from the Ross Sea,Antarctica

The biodiversity research expedition TAN0204 with RS Tangaroa to the Ross Sea in 2004 yielded a new collection of 2,687 specimens of pycnogonids. As much as 25 different species encompassing 14 genera and eight families were identified and their records are discussed herein. The collection is archived in the Marine Invertebrate Collection of the New Zealand National Institute of Water and Atmospheric Research (NIWA). The majority (69%) of specimens are from the Nymphon australe group (Nymphonidae), although species richness and abundance varied among the stations sampled. The collection includes several specimens from polymerous taxa; Pentanymphon antarcticum (Nymphonidae), Decolopoda australis (Colossendeidae) and Pentapycnon bouvieri (Pycnogonidae). All species were classified based on morphological characters, and DNA sequences (from the 18S, 12S, 16S and COI regions) for 21 of the representative morphotypes are given. The DNA sequences confirmed the species-level distinctiveness of these morphotypes. No species new to science were identified, although further detailed morphometric and/or molecular analyses may reveal cryptic or sibling species, especially in species such as the highly abundant Nymphon australe group. An erratum to this article can be found at     

Structure of the body cavity of the sea spider <Emphasis Type="Italic">Nymphon brevirostre</Emphasis> Hodge, 1863 (Arthropoda: Pycnogonida)

The microscopic anatomy and ultrastructure of the body cavity and adjacent organs in the sea spider Nymphon brevirostre Hodge, 1863 (Pycnogonida, Nymphonidae) were examined by transmission electron microscopy. The longitudinal septa subdividing the body cavity are described: (1) Dohrn’s horizontal septum, (2) lateral heart walls, and (3) paired ventral septa consisting of separate cellular bands. The body cavity is a hemocoel, it has no epithelial lining and is only bordered by a basal lamina. The epidermis, heart, and Dohrn’s septum are not separated from each other by basal laminae and may have a common origin. The cellular bands forming the longitudinal ventral septa are not covered with the basal lamina and presumably derive from cells belonging to the hemocoel. The roles of the morphological structures studied for the circulation of hemolymph are discussed. The gonad lies inside Dohrn’s septum, it is covered with its own basal lamina and surrounded by numerous lacunae of the hemocoel entering the septum. The gonad wall is formed with a single layer of epithelium. The same epithelial cells form the gonad stroma. The gonad cavity is not lined with the basal lamina; muscle cells are present in the gonad wall epithelium, thus rendering the lumen similar to a coelomic cavity. Freely circulating cells of two types are found in the hemocoel: small amebocytes containing electronic-dense granules that are similar to granulocytes of other arthropods, as well as hemocytes with large vacuoles of varying structure that are comparable with plasmatocytes; however some of these may be activated granulocytes.     

Feeding of Achelia echinata Hodge (Pycnogonida) on marine algae

Field observations of Achelia echinata Hodge in Southampton Water suggested that it may be feeding on Griffithsia and Enteromorpha, although this pycnogonid was not known to be algivorous. This possibility was experimentally tested by maintaining the pycnogonid on ¹⁴C-labelled weeds, whence they were found to take up activity in proportion to the concentration of ¹⁴C in the weed. The experimental design precluded sea water, bacteria or any passive uptake as a source of the ¹⁴C in the pycnogonids, and comparisons between Enteromorpha and Griffithsia eliminated epiphytes as the source. It is concluded that Achelia echinata actively feeds on these two species of seaweed, possibly more readily on Enteromorpha. The feeding behaviour and its significance are discussed.     

Hox genes in sea spiders (Pycnogonida) and the homology of arthropod head segments

The pycnogonids (or sea spiders) are an enigmatic group of arthropods, classified in recent phylogenies as a sister-group of either euchelicerates (horseshoe crabs and arachnids), or all other extant arthropods. Because of their bizarre morpho-anatomy, homologies with other arthropod taxa have been difficult to assess. We review the main morphology-based hypotheses of correspondence between anterior segments of pycnogonids, arachnids and mandibulates. In an attempt to provide new relevant data to these controversial issues, we performed a PCR survey of Hox genes in two pycnogonid species, Endeis spinosa and Nymphon gracile, from which we could recover nine and six Hox genes, respectively. Phylogenetic analyses allowed to identify their orthology relationships. The Deformed gene from E. spinosa and the abdominal-A gene from N. gracile exhibit unusual sequence divergence in their homeodomains, which, in the latter case, may be correlated with the extreme reduction of the posterior region in pycnogonids. Expression patterns of two Hox genes (labial and Deformed) in the E. spinosa protonymphon larva are discussed. The anterior boundaries of their expression domains favour homology between sea spider chelifores, euchelicerates chelicerae and mandibulate (first) antennae, in contradistinction with previously proposed alternative schemes such as the protocerebral identity of sea spider chelifores or the absence of a deutocerebrum in chelicerates. In addition, while anatomical and embryological evidences suggest the possibility that the ovigers of sea spiders could be a duplicated pair of pedipalps, the Hox data support them as modified anterior walking legs, consistent with the classical views.Supplementary material is available for this article at and is accessible for authorized users.Guest editors Jean Deutsch and Gerhard Scholtz     

Isoenzymes and Taxonomy in Scandinavian Hydroids (Cnidaria, Campanulariidae)

Acid phosphatases, esterases and leucine aminopeptidases were studied in Campanularia integra, Clytia hemisphaerica (the johnstoni form), Laomedea ftexuosa, Gonothyraea loveni, Obelia geniculata, O. longissima and O. dichotoma , using polyacrylamide gel electrophoresis. Species-specific patterns were obtained, notably regarding acid phosphatase, despite strong individual variation. The electrophoretic results combined with differences in morphology and cnidom indicate that O. longissima and O. dichotoma are separate species. The acid phosphatase patterns of the two species and of O. geniculata showed basic similarities, supporting their assignment to a common genus. The profound differences in the acid phosphatase patterns of C. integra and L. flexuosa , may in conjunction with morphological distinction justify their assignment to separate genera. C. integra also included specimens of caliculata morphology: however, these did not deviate in their band patterns. Electrophoretograms of the typical O. dichotoma resembled those of the dubia and plicata forms. Moreover, O. gelatinosa with free Obelia medusae (sensu Hincks 1868) is suggested to be conspecific with O. longissima . The present study indicates that electrophoretic analyses, particularly of acid phosphatases presenting highly reproducible patterns, is a valuable complement to morphological characters when studying the taxonomy in hydroids.     

THE TYPE SPECIES OF CERAMIUM (RHODOPHYTA), CERAMIUM VIRGATUM ROTH: TYPIFICATION AND PHYLOGENY

The type species of Ceramium is Ceramium virgatum Roth (1797, Cat. Bot I: 148, pl. VIII, fig. 1). This has been treated as a probable synonym of Ceramium nodulosum (Lightfoot) Ducluzeau, one of the species formerly confused under the illegitimate name Ceramium rubrum (Hudson) C. Agardh. However, in 1996 Silva showed that C. nodulosum (Lightfoot) Ducluzeau is a later homonym of C. nodulosum de Candolle 1805, and advocated conserving C. rubrum with a neotype. As an alternative to this, we investigated whether the name C. virgatum might be available for this species. The lectotype of C. virgatum is Roth's illustration of a much-branched, fully corticate, Ceramium specimen from Eckwarden, North Sea, which could represent any member of the ' C. rubrum' group. We obtained material resembling Roth's, from the North Sea island of Helgoland, as a potential epitype. Its rbc L sequence was aligned with sequences of all C. rubrum -like species in the British Isles, i.e. C. secundatum , C. botryocarpum , C. pallidum and ' C. nodulosum '. The Helgoland material was clearly conspecific with ' C. nodulosum ' from Ireland (0.08% divergence). We therefore suggest that the name C. virgatum Roth should be employed for this species. Phylogenetic analyses of these sequences aligned with various representatives of the tribe Ceramieae, placed the North Atlantic C. rubrum -like species in two well-supported clades. In one of these, C. virgatum is basal to C. secundatum and C. botryocarpum. The other clade consists of C. pallidum and a partly ecorticate species resembling C. diaphanum.     

Description and relationships of Chaetopterus pugaporcinus, an unusual pelagic polychaete (Annelida, Chaetopteridae)

An extraordinary new species, Chaetopterus pugaporcinus, is described from eight specimens collected from deep mesopelagic waters off Monterey Bay, California, by remotely operated vehicles. All specimens exhibit a consistent combination of both adult and larval characteristics, leaving in question the maturity of the specimens. All specimens lack ciliated larval bands and the stout, modified chaetae (cutting spines) typically found in segment A4 of chaetopterids. If the specimens described here are larvae, they are remarkable for their size, which ranged from 10 to 21 mm total length, nearly twice the length of the largest polychaete larvae previously reported and 5 to 10 times larger than known chaetopterid larvae. Then too, their lack of segment addition prior to settlement would be atypical. If adult, they are particularly unusual in their habitat choice and body form. Morphology of the uncini and comparison to larval morphology indicated a close relationship to either Chaetopterus or Mesochaetopterus. However, the lack of cutting spines and typical adult morphology made it impossible to determine to what genus this species should be allied. Thus, we carried out the first molecular phylogenetic analysis of the Chaetopteridae in order to appropriately place and name the new species. Three partial genes were sequenced for 21 annelid species. The sequencing also provides the first molecular evidence that Chaetopterus variopedatus sensu Hartman (1959) is not a single cosmopolitan species. The question of C. pugaporcinus being a delayed larva or a genuine holopelagic chaetopterid is discussed.     

Molecules,morphology, missing data and the phylogenetic position of a recently extinct madtom catfish (Actinopterygii: Ictaluridae)

Taxa missing large amounts of data pose challenges that may hinder the recovery of a well‐resolved, accurate phylogeny and leave questions surrounding their phylogenetic position. Systematists commonly have to contend with one or two species in a group for which there is little or no material available suitable for recovering molecular data. It is unclear whether these taxa can be better placed using analyses based on morphological data only, or should be included in broader analyses based on both morphological and molecular data. The extinct madtom catfish Noturus trautmani is known from few specimens for which molecular data are unavailable. We included this taxon in parsimony and Bayesian analyses of relationships of madtom catfishes based on a combination of morphological and molecular data. Results indicate that using a combination of morphological and molecular data does a better job at providing a phylogenetic placement for N. trautmani than morphology alone, even though it is missing all of its molecular characters. We provide a novel hypothesis of relationships among Noturus species and recommendations for classification within the group. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 60–75.     

Analysis of the clinal variation pattern inSilene latifolia (Caryophyllaceae) pollen morphology

Reticulate and microechinate pollen forms withinSilene latifolia (S. alba, S. pratensis) were first described from N. America, where the species is an introduced weed. A previous study showed that the two forms also exist in Europe and intergrade along a zone roughly congruent with intergradation zones in seed morphology and flavone glycosylation genotypes. The present survey of pollen from herbarium specimens is more extensive and covers localities from nearly the whole of the species' native Eurasian and North African range. The first axis of a detrended correspondence analysis (DCA) of qualitative characterstate data for 11 pollen morphological characters shows a gradient between the two extreme exine types, reticulate and microechinate. When mapped, the co-ordinates of pollen samples on this axis indicate a broad zone of intergradation which coincides approximately with the somewhat sharper transition between low- and high-tubercle seeds in C. and N. Europe, but becomes diffuse in Italy and the Mediterranean region and diverges from the seed transition zone in SW. Asia and the Middle East. The biological significance of the pollen morphs is unknown; the variation pattern in pollen morphology, unlike that in seeds, is not consistently correlated with macroclimate.     

Nectary structure and nectar secretion in Maxillaria coccinea (Jacq.) L.O. Williams ex Hodge (Orchidaceae)

BACKGROUND AND AIMS: It had previously been assumed that Maxillaria spp. produce no nectar. However, nectar has recently been observed in Maxillaria coccinea (Jacq.) L.O. Williams ex Hodge amongst other species. Furthermore, it is speculated that M. coccinea may be pollinated by hummingbirds. The aim of this paper is to investigate these claims further. METHODS: Light microscopy, histochemistry, scanning and transmission electron microscopy. KEY RESULTS: This is the first detailed account of nectar secretion in Maxillaria Ruiz & Pav. A 'faucet and sink' arrangement occurs in M. coccinea. Here, the nectary is represented by a small protuberance upon the ventral surface of the column and nectar collects in a semi-saccate reservoir formed by the fusion of the labellum and the base of the column-foot. The nectary comprises a single-layered epidermis and three or four layers of small subepidermal cells. Beneath these occur several layers of larger parenchyma cells. Epidermal cells lack ectodesmata and have a thin, permeable, reticulate cuticle with associated swellings that coincide with the middle lamella between adjoining epidermal cells. Nectar is thought to pass both along the apoplast and symplast and eventually through the stretched and distended cuticle. The secretory cells are collenchymatous, nucleated and have numerous pits with plasmodesmata, mitochondria, rough ER and plastids with many plastoglobuli but few lamellae. Subsecretory cells have fewer plastids than secretory cells. Nectary cells also contain large intravacuolar protein bodies. The floral morphology of M. coccinea is considered in relation to ornithophily and its nectary compared with a similar protuberance found in the entomophilous species M. parviflora (Poepp. & Endl.) Garay. CONCLUSIONS: Flowers of M. coccinea produce copious amounts of nectar and, despite the absence of field data, their morphology and the exact configuration of their parts argue strongly in favour of ornithophily.