Fernando Pardos

Phylogeny of Kinorhyncha Based on Morphology and Two Molecular Loci

The phylogeny of Kinorhyncha was analyzed using morphology and the molecular loci 18S rRNA and 28S rRNA. The different datasets were analyzed separately and in combination, using maximum likelihood and Bayesian Inference. Bayesian inference of molecular sequence data in combination with morphology supported the division of Kinorhyncha into two major clades: Cyclorhagida comb. nov. and Allomalorhagida nom. nov. The latter clade represents a new kinorhynch class, and accommodates Dracoderes, Franciscideres, a yet undescribed genus which is closely related with Franciscideres, and the traditional homalorhagid genera. Homalorhagid monophyly was not supported by any analyses with molecular sequence data included. Analysis of the combined molecular and morphological data furthermore supported a cyclorhagid clade which included all traditional cyclorhagid taxa, except Dracoderes that no longer should be considered a cyclorhagid genus. Accordingly, Cyclorhagida is divided into three main lineages: Echinoderidae, Campyloderidae, and a large clade, ‘Kentrorhagata’, which except for species of Campyloderes, includes all species with a midterminal spine present in adult individuals. Maximum likelihood analysis of the combined datasets produced a rather unresolved tree that was not regarded in the following discussion. Results of the analyses with only molecular sequence data included were incongruent at different points. However, common for all analyses was the support of several major clades, i.e., Campyloderidae, Kentrorhagata, Echinoderidae, Dracoderidae, Pycnophyidae, and a clade with Paracentrophyes + New Genus and Franciscideres (in those analyses where the latter was included). All molecular analyses including 18S rRNA sequence data furthermore supported monophyly of Allomalorhagida. Cyclorhagid monophyly was only supported in analyses of combined 18S rRNA and 28S rRNA (both ML and BI), and only in a restricted dataset where taxa with incomplete information from 28S rRNA had been omitted. Analysis of the morphological data produced results that were similar with those from the combined molecular and morphological analysis. E.g., the morphological data also supported exclusion of Dracoderes from Cyclorhagida. The main differences between the morphological analysis and analyses based on the combined datasets include: 1) Homalorhagida appears as monophyletic in the morphological tree only, 2) the morphological analyses position Franciscideres and the new genus within Cyclorhagida near Zelinkaderidae and Cateriidae, whereas analyses including molecular data place the two genera inside Allomalorhagida, and 3) species of Campyloderes appear in a basal trichotomy within Kentrorhagata in the morphological tree, whereas analysis of the combined datasets places species of Campyloderes as a sister clade to Echinoderidae and Kentrorhagata.

New Data on the Genus Paracentrophyes (Homalorhagida, Kinorhyncha), with the Description of a New Species from the West Pacific~!2010-01-06~!2010-04-21~!2010-05-18~!

The kinorhynch genus Paracentrophyes currently consists of two species only: P. quadridentatus (Zelinka, 1928) from the Mediterranean Sea and P. praedictus Higgins, 1983 from Belize in the Caribbean. Both species have until now been recorded from their type localities only. In the present contribution a new species of Paracentrophyes, P. anurus sp. nov., is described from the Korea Strait. The species can be recognized by details in the mouth cone morphology, absence of perispinal setae in segment 10, and absence of a midterminal process in both sexes. Female specimens are furthermore characterized by the presence of an extraordinary long middorsal spine on segment 10, whereas males possess a midterminal type 3 sensory spot. Besides the recording of the new species, the occurrence of P. cf. quadridentatus is reported from two localities in the Atlantic Ocean (Faeroe Islands and Spain). The recorded specimens are described in detail, based on combined examinations with LM and SEM, and diagnostic traits for all three species of Paracentrophyes are discussed in light of the newly acquired information. Furthermore, an emended terminology for positions of cuticular trunk structures is proposed.

On the genus Dracoderes Higgins & Shirayama, 1990 (Kinorhyncha: Cyclorhagida) with a redescription of its type species, D. abei, and a description of a new species from Spain

Abstract The type species of Dracoderes, D. abei, is redescribed based on specimens from several localities in Japan and Korea, and a new species of the genus, Dracoderes gallaicus sp. nov., is described from the coast of Spain in Western Europe. The new species is distinguished by the presence of lateral accessory spines on segment 5. In addition, preliminary diagnostic notes on a yet undescribed species from the Okinawa Region, Dracoderes sp. 1, are provided. Based on new information from D. abei and D. gallaicus sp. nov., an emended genus diagnosis for Dracoderes is proposed. The study includes the first scanning electron microscopical data for species of Dracoderes, and presents for the first time detailed information about head morphology and scalid arrangement, new data about the arrangement of the neck placids, and demonstrates the presence of feebly visible nephridial pores. The new information may be of phylogenetic significance, and is expected to contribute important data for future phylogenetic analyses of the kinorhynch interrelationships.

ULTRASTRUCTURAL OBSERVATIONS ON THE PHORONID NERVOUS SYSTEM

Standard transmission electron microscopy (TEM) techniques have been applied to three species of phoronids to describe cytological features of their nervous systems. Four types of neurons have been distinguished by morphological and ultrastructural criteria, mainly involving their kinds of vesicles. Glial cells with characteristic polymorphic dense granules are abundant in the plexus, with possible roles in neuronal nourishment, mechanical support, and neurosecretion. Synaptic contacts and neuromuscular junctions across the connective tissue are described. The different structural features of the trunk giant axons in the three species mainly concern the enveloping sheath, and are described and discussed. Data on the innervation of internal organs, such as gut and nephridia, are also given. A detailed description of the structure, arrangement, and relationships of tentacular sensory cells, probably mechanoreceptors, is included, with a tentative hypothesis concerning the functions of these cells.

Morphology disentangles the systematics of a ubiquitous but elusive meiofaunal group (Kinorhyncha: Pycnophyidae)

Kinorhyncha is a group of benthic, microscopic animals distributed worldwide in marine sediments. The phylum is divided into two classes, Cyclorhagida and Allomalorhagida, congruent with the two major clades recovered in recent phylogenetic analyses. Allomalorhagida accommodates more than one‐third of the described species, most of them assigned to the family Pycnophyidae. All previous phylogenetic analyses of the phylum recovered the two genera within Pycnophyidae, Pycnophyes and Kinorhynchus, as paraphyletic and polyphyletic. A major problem in these studies was the lack of molecular data of most pycnophyids, due to the limited and highly localized distribution of most species, often in the Arctic and the deep‐sea. We here overcame the problem by adding a morphological partition with data for 79 Pycnophyidae species, 15 of them also represented by molecular data. Model‐based analyses yielded seven clades, which each was supported by several morphological apomorphies. Accordingly, Kinorhynchus is synonymized with Pycnophyes and six new genera are described for the remaining recovered clades: Leiocanthus gen. nov., Cristaphyes gen. nov., Higginsium gen. nov., Krakenella gen. nov., Setaphyes gen. nov. and Fujuriphyes gen. nov.

Pycnophyes dolichurus sp. nov. and P. aulacodes sp. nov. (Kinorhyncha, Homalorhagida, Pycnophyidae), two new kinorhynchs from Spain with a reevaluation of homalorhagid taxonomic characters

Two new species of the kinorhynch genus Pycnophyes are described from the Atlantic Ocean, Northwest Spain, and the Mediterranean Sea, East of Spain, using differential interference contrast microscopy and scanning electron microscopy (SEM): Pycnophyes dolichurus sp. nov. and P. aulacodes sp. nov. Taxonomic characters from cuticular structures in homalorhagids are discussed and reevaluated. The longitudinal positions of cuticular structures along the trunk are furthermore defined, and the positional terminology is standardized. The distribution of the genus Pycnophyes in European waters is revised, revealing a poor knowledge of kinorhynch biogeography, probably due to incomplete sampling.

Cuticular structures and epidermal glands of Echinoderes cantabricus and E. hispanicus (Kinorhyncha, Cyclorhagida) with special reference to their taxonomic value

The body wall of two species of kinorhynchs, Echinoderes cantabricus and E. hispanicus, was examined with transmission and scanning electron microscopy, to determine accurately the nature, arrangement, and consistency of characters used for taxonomic purposes. Structural details of cuticular hairs, pectinate fringes, spines, tubules, and different cuticular scars are described and discussed. Two kinds of epidermal glands, types 1 and 2, are characterized according to the nature of their secretory products, their exact location and distribution in the trunk segments, and their possible value as taxonomic characters. The generally assumed function of tubules for the release of secretory product is analyzed and finally rejected in light of the different distribution of tubules and glands along the trunk and because of the absence of a clear anatomic relation between both structures. The cuticular features studied can be useful for taxonomic purposes because of their consistency, but some of them are difficult to access and evaluate and therefore must be used with caution. J. Morphol. 246:161–178, 2000.

Comparative morphology of serotonergic‐like immunoreactive elements in the central nervous system of kinorhynchs (kinorhyncha, cyclorhagida)

Cycloneuralian taxa exhibit similar organ system architectures, providing informative characters of metazoan evolution, yet very few modern comparative descriptions of cellular and molecular homologies within and among those taxa are available. We immunolabeled and characterized elements of the serotonergic nervous system in the kinorhynchs Echinoderes spinifurca, Antygomonas paulae, and Zelinkaderes brightae using confocal laser scanning microscopy. Fluorescent markers targeting DNA were combined with observations of auto‐fluorescent structures to guide interpretations of the internal and external anatomy in each species. Results show a common pattern of the central nervous system with a circumenteric brain divided into ring‐shaped anterior and posterior neuronal somata and a central neuropil connected to a multi‐stringed, longitudinal ventral nerve cord. Structural similarities and differences in the nervous systems of these species were observed and described, stressing the incomplete ring nature of the anterior region of the kinorhynch brain, the functional relationship between the brain and the movable introvert, and the number and arrangement of nerve strings and somata of the ventral nerve cord. The ventral cord ends in two ventrolateral cell bodies in E. spinifurca, and forms a terminal loop associated with a midterminal spine in A. paulae and Z. brightae. The possible functional and phylogenetic significance of these features and arrangements are discussed. J. Morphol., 2013.

Ultrastructure of the midgut and hindgut of Derocheilocaris remanei (Crustacea, Mystacocarida)

ABSTRACT

Ultrastructure of the labrum and foregut of Derocheilocaris remanei (Crustacea, Mystacocarida)

The cuticle‐lined foregut of Derocheilocaris remanei consists of the mouth with its associated labrum, and an undifferentiated esophagus. It is separated from the midgut by an esophageal valve. The labrum is a conspicuous structure moved by five pairs of muscles (four dorsoventral and one longitudinal). Four pairs of subcuticular glands open to its inner face forming two longitudinal, lateral rows of cuticular pores. Each secretory unit is composed of a glandular component (with one or two secretory cells), a neck cell, and a duct cell. In addition, a single gland cell opens mesially into the buccal cavity.