Morphology and ultrastructure of the adult ovarian cycle in Mithracidae (Crustacea,Decapoda, Brachyura,Majoidea)

The ultrastructure of the ovary during development and yolk production is poorly known in Brachyura and Majoidea in particular. Here, we describe the histology, histochemistry and ultrastructure of the adult ovarian cycle in four Mithracidae species from three different genera: Mithrax hispidus, Mithrax tortugae, Mithraculus forceps and Omalacantha bicornuta. All species showed a similar pattern of ovarian development and vitellogenesis. Macroscopically, we detected three stages of ovarian development: rudimentary (RUD), developing (DE) and mature (MAT); however, in histological and ultrastructural analyses, we identified four stages of development. The oocytes of the RUD stage, during endogenous vitellogenesis, have basophilic cytoplasm filled with dilated rough endoplasmic reticulum. The reticulum lumen showed many granular to electron-dense materials among the different stages of development. The Golgi complexes were only observed in the RUD stage and are responsible for releasing vesicles that merge to the endogenous or immature yolk vesicles. At the early DE stage, the oolemma showed many coated and endocytic vesicles at the cortex. The endocytic vesicles merge with the endogenous yolk to form the exogenous or mature yolk vesicles, always surrounded by a membrane, characterizing exogenous vitellogenesis. The exogenous yolk vesicles comprise glycoproteins, showing only neutral polysaccharides. At the late DE stage, endocytosis still occurs, but the amount of endogenous yolk decreases while the exogenous yolk increases. The late DE stage is characterized by the beginning of chorion production among the microvilli. The MAT stage is similar to the late DE, but the endogenous yolk is restricted to a few cytoplasmic areas, the ooplasma is filled with exogenous yolk, and the oolemma has very few coated vesicles. In the MAT stage, the chorion is fully formed and shows two electron-dense layers. The ovarian development of the species studied has many similarities with the very little known Majoidea in terms of the composition, arrangement and increment of the yolk vesicles during oocyte maturation. The main differences are in the vitellogenesis process, where immature yolk formation occurs without the direct participation of the mitochondria but with the participation of the rough endoplasmic reticulum in the endogenous phase.     

Larval development of Japanese 'conchostracans': part 2, larval development of Caenestheriella gifuensis (Crustacea, Branchiopoda, Spinicaudata, Cyzicidae), with notes on homologies and evolution of certain naupliar appendages within the Branchiopoda

As part of a larger project examining and comparing the ontogeny of all major taxa of the Branchiopoda in a phylogenetic context, the larval development of Caenestheriella gifuensis (Ishikawa, 1895), a Japanese spinicaudatan ‘conchostracan’, is described by scanning electron microscopy. Seven different larval stages are recognised, in most cases based on significant morphological differences. They range in length from about 200 to 850 μm. Nauplius 1 has a plumb and lecithotrophic appearance with a rounded hind body and a labrum with an incipient medial spine. Limb segmentation is mostly unclear but the second antennae have more putative segments delineated than are expressed in the later stages. Feeding structures such as the mandibular coxal process and antennal coxal spine are only weakly developed. Nauplius 2 is very different from nauplius 1 and has three large spines on the labral margin and two long caudal spines. Feeding structures such as the mandibular coxal process and various spines and setae are developed, but whether feeding begins at this stage was not determined. The mandible has developed an ‘extra’ seta on endopod segment 1, absent in Nauplius 1. The segmentation of the second antenna has changed significantly due to fusions of various early segments. Nauplius 3 is like nauplius 2 in morphological detail, but larger and more elongate. Nauplius 4 has developed a pair of small anlagen of the carapace and rudiments of the first five pairs of trunk limbs, and the coxal spine of the antenna has become distally bifid. Nauplius 5 has a larger carapace anlage, externally visible enditic portions of the elongate trunk limbs, and a pair of primordial dorsal telson setae. Nauplius 6 has a larger and partly free carapace and better-developed, partly free trunk limbs with incipient enditic, endopodal, and exopodal setation. A pair of caudal spines, dorsal to the large caudal spines, has appeared. Nauplius 7 is quite similar to nauplius 6 but is larger and has slightly longer caudal and labral spines; also, the setation of the most anterior trunks limbs is better developed. The larval development is largely similar to that of other spinicaudatans. The larval mandible, which is evolutionarily conservative within the Branchiopoda, reveals a setation pattern similar to that of the Anostraca and Notostraca (two setae on mandibular endopod segment 1). Most other spinicaudatans and all examined laevicaudatans share another setal pattern (one seta on mandibular endopod segment 1), which could indicate a close relationship among these taxa. The second antenna undergoes a special development, which provides an insight into the evolution of this limb within the Branchiopoda. In nauplius 1 the basipod, endopod, and exopod are all superficially divided into a relatively high number of segments. In later nauplii some of these have fused, forming fewer but larger segments. We suggest that this ontogeny reflects the evolution of antennae in the conchostracans. Various aspects of the morphology of the antennae are discussed as possible synapormorphies for either the Diplostraca or subgroups of the Conchostraca.     

On the larval development of<Emphasis Type="Italic"> Eubranchipus grubii</Emphasis> (Crustacea,Branchiopoda, Anostraca), with notes on the basal phylogeny of the Branchiopoda

Selected larval stages of Eubranchipus grubii (Anostraca) from Danish temporary waters are examined by scanning electron microscopy in a phylogenetic context. The study focuses on limb development and body segmentation. It is shown that the large, proximal endite of the trunk limbs in the adult Anostraca is actually a fusion product of two smaller endites which make their appearance in the early larval development. This gives a total of six endites along the inner margin of the trunk limbs. An unsegmented endopod follows more distally. A small additional, seventh endite makes a short appearance in late larvae, but has disappeared in the adults. The naupliar feeding apparatus is of the same type as found in other branchiopods, and has previously been suggested as an autapomorphy for the Branchiopoda. The similarities between the naupliar feeding apparatus of E. grubii and other branchiopods include the presence of a long protopod with a characteristic morphology of the coxal and basipodal masticatory spines/setae, and a three-segmented mandibular palp (basipod and two endopod segments) with a largely similar setation in all taxa. The mode of trunk limb development is also the same as seen in most other recent branchiopods. The phylogenetic significance for the basal phylogeny of the Branchiopoda of these and other morphological features is discussed in relation to the phylogenetic position of two branchiopod fossils, Lepidocaris rhyniensis and Rehbachiella kinnekullensis. While R. kinnekullensis has previously been suggested to be a stem lineage branchiopod, the position of L. rhyniensis is more uncertain. Three different possible phylogenetic positions of L. rhyniensis are discussed: (a) L. rhyniensis as a stem lineage anostracan, (b) L. rhyniensis as a stem lineage branchiopod or (c) L. rhyniensis as a stem lineage phyllopod. It seems most plausible to consider L. rhyniensis a stem lineage anostracan.     

山羊蠕形螨扫描电镜观察

本文通过扫描电镜对寄生虫山羊体的山羊蠕形螨生活史各期颚体,足体和末体的超微结构观察,发现以下超微结构;一个圆锥状须乳突位于雌螨触须第２节背面;叶状背阳茎侧突和腹阳茎侧突竖立于阳茎同一基部,未受精雌螨船形阴门的一对瓣汇成纵线,雌螨交配后阴门半开,产卵后全部敞开,同时描述该螨的背基刺,锥状突,口下板,螯肢,基内叶,口孔,须爪和肛道等的超微结构,文中还讨论了锥状突,口下板,螯肢,基内叶,须爪和须乳突的功     

Ryocalanus spinifrons,a new species of Ryocalanidae (Copepoda: Calanoida), from the southwestern part of Sagami Bay,Japan

A new Ryocalanoid copepod, Ryocalanus spinifrons, collected by the MTD net system at a depth of 1400 m from the southwestern part of Sagami Bay, Japan, is described. The new species is morphologically very close to R. infelix Tanaka, 1956 (female unknown) from the Izu region of Sagami Bay. It is distinguished from other species by the presence of 12 long spinules on the ventral inner side of the fifth pedigerous somite, nine setae on the coxal epipodite of the maxillule and nine large robust spinules on the coxal segment of the fourth leg. The row of five robust spines on the paragnath distinguishes R. spinifrons.     

The effect of salinity and temperature on the larval development of Mithrax caribbaeus Rathbun, 1920 (Brachyura: Majidae) reared in the laboratory

Larvae of Mithrax caribbaeus were reared in the laboratoryin a factorial experiment employing three temperatures (22,25 and 28°C) and three salinities (32, 35 and 38). Survivaland duration of larval stages were recorded. Ovigerous femalesof M.caribbaeus were collected from the south-eastern coastof Margarita Island, Venezuela, and maintained in individualaquaria until hatching. Eggs from three of the females hatchedin the laboratory. Larvae from each hatching were subdividedinto groups of 10 and reared in plastic bowls containing 200ml filtered and UV-irradiated sea water at different temperature–salinitycombinations. Larvae were transferred daily to clean bowls withnewly hatched Artemia nauplii, and the number of molts and mortalitywithin each bowl was recorded. Complete larval development ofM.caribbaeus occurred under all experimental conditions. Salinityhad the greatest effect on percentage survival of each larvalstage and complete development up to the first crab stage. Thefirst zoeal stage exhibited the highest survival rate. Maximumsurvival for this stage occurred at 25°C, 32–35. Survivalin the second zoeal stage and the megalopa was affected onlyby salinity. Effects of temperature and salinity on survivaldecreased with advance in development. The duration of the twozoeal stages, the megalopa, and development to the first crabstage showed a gradual reduction with increasing temperature.Salinity showed an effect on the duration of zoeal stages butnot on the megalopal stage. Development from hatching to thefirst crab stage required 8–18 days, depending on thetemperature–salinity combination, and was inversely relatedto temperature, averaging 14.3 days at 22°C, 11.8 days at25°C and 9.2 days at 28°C.     

Taxonomic significance of spine morphology in the echinoid genera Diadema and Echinothrix

Abstract. The spine morphology of all established species of Diadema and Echinothrix, including 2 color morphs of E. calamaris, were examined externally and internally via transverse sectioning to identify diagnostic species features and to assess the morphological relationship between species. Forty‐nine different morphological characters were measured and analysed using ordination by multi‐dimensional scaling (MDS) and cluster analysis. Specimens of Diadema paucispinum and D. setosum had very distinct spine structures. In D. paucispinum, the spines were more robust than those of other species of Diadema. This was evident in the spine's internal structure, with large, closely packed solid wedges, a small axial cavity, and rings of trabeculae throughout the spine's length. The spines in D. setosum were distinctive because of their length in relation to test size and the reduced flaring of their verticillations. The spines of other members of this genus were very similar to each other. Without careful sectioning, the spines from specimens of D. antillarum, D. ascensionis, D. mexicanum and D. savignyi were difficult to differentiate. The internal structures of spines for each species did, however, possess a combination of features that differentiated the species. Such features included the shape, orientation, and number of solid wedges, the presence or absence of spokes and rings of trabeculae between the solid wedges, and the presence or absence of tissue within the axial cavity. Individuals of Diadema palmeri also had spines morphologically similar to other species, however, the red pigmentation of these spines (in life and when preserved) made them easily distinguishable. The spine structures of the 2 species of Echinothrix were starkly different, while the white and brown color morphs of E. calamaris had morphologically distinctive ambulacral and interambulacral spines. The blunt, open‐tipped interambulacral spines, with reticular tissue present in the axial cavity of the white color morph, were easily distinguished from the pointed, closed‐tipped spines, with a hollow axial cavity found in the brown color morph. Such differences indicate that the brown color morph is either a subspecies or a separate species. Taken together the data show that each species has significant morphological differences in the structure of the spines. It is evident from our data that spine morphology is a useful tool to differentiate these commonly confused species.     

Allelic diversity at the Mhc-DQA locus in cotton rats (Sigmodon hispidus) and a comparison of DQA sequences within the family Muridae (Mammalia: Rodentia)

 The cotton rat (Sigmodon hispidus) is a common murid rodent of the southern United States, Mexico, and Central America. Using single-stranded conformation polymorphism analysis and DNA sequencing techniques, 11 DQA exon 2 alleles were detected among 180 S. hispidus from Caddo County, Oklahoma, USA. The alleles represent a single locus exhibiting a high level of polymorphism. Nucleotide and amino acid distance values among DQA alleles of S. hispidus were higher than those within Mus musculus and species of Rattus. Although the distribution of polymorphic amino acid residues among alleles of S. hispidus was similiar to that of Mus and Rattus, some residues of the α-helix region were more variable in S. hispidus. Comparisons of nonsynonymous and synonymous substitutions indicated a trend toward higher numbers of nonsynonymous substitutions; however, this difference was not significant statistically among S. hispidus alleles. To examine evolution of DQA alleleswithin Muridae, we performed a phylogenetic analysis that included DQA alleles from S. hispidus, Peromyscus leucopus, M. musculus, R. norvegicus, and six Australian species of Rattus. Results depicted monophyly for each genus, and this concordance between species and gene trees represents a lack of evidence for trans-species persistence of alleles among these genera. Received: 22 October 1998 / Revised: 17 March 1999     

Lack of taxonomic information from parietal spine size invalidates subspecies in the Atlantic hookear sculpin Artediellus atlanticus

An analysis of 107 individuals of Atlantic hookear sculpin Artediellus atlanticus from the Barents Sea–Svalbard region and from north‐east Greenland shows that the state of the parietal spines, although not randomly distributed geographically, occurs sympatrically. They do not diagnostically describe populations. They are therefore inept for subspecies delimitation into Artediellus atlanticus atlanticus, Artediellus atlanticus corniger and Artediellus atlanticus europaeus. Sympatric occurrence of parietal spine states called for a molecular approach to look for differences at a species level. Sequencing the mitochondrial genes, cytochrome oxidase c subunit I (coI) and cytochrome b (cytb), shows no difference between individuals with different parietal spine size. Thus, there is no evidence of the spine states representing species‐level variation. The study shows that parietal spine size has no taxonomic information for this species. The patterns of variation in parietal spine size differ to some degree between the sexes.     

Speciation in sympatric species of land snails from the genus Trochulus (Gastropoda,Hygromiidae)

The identification and designation of land snail species in the genus Trochulus on the basis of shell characteristics are problematic because of their great phenotypic plasticity. Some genetic analyses have proved inconclusive, with much variation within populations and apparent gene flow among them. We examined this issue by morphometric and molecular approaches on the morphologically similar species T. coelomphala, T. hispidus and T. striolatus, co‐occurring in the Alpenvorland of Germany. While these species differed in shell and reproductive system morphology, there were forms that turned out intermediate in shell characters between T. coelomphala and T. hispidus but had genital morphology similar to T. coelomphala. Phylogenetic analysis, however, showed that these forms clustered neither with T. coelomphala nor T. hispidus but are sister to T. striolatus from the same region, which suggests that they evolved by way of sympatric speciation. Further, these analyses suggest that T. coelomphala diverged within T. hispidus; a crossing experiment indicated that they were interfertile. Expanding the study to include all available Trochulus sequences enabled us to infer evolutionary relationships between them and showed that T. hispidus is polyphyletic. Some Trochulus samples of one nominal species were grouped within others. The combination of phenotypic plasticity and possible mitochondrial DNA introgression illustrates the complex nature of evolutionary processes and the need for caution in the application of traditional taxonomic practice.     

Genetic population structure and morphological characters of Japanese psychrolutids of genus <Emphasis Type="Italic">Malacocottus</Emphasis> (Scorpaeniformes: Psychrolutidae)

The genetic population structure and the diagnostic characters of Malacocottus gibber from the Japan Sea and Malacocottus zonurus from the Okhotsk Sea and the northwestern Pacific were compared. Analysis of the nucleotide sequences of the mitochondrial control region revealed no genetic differences between the populations of M. gibber and M. zonurus, even though most individuals of both the species were found to be morphologically distinct. Most of the Malacocottus gibber specimens had the typical morphological characters of this species, namely the absence of an accessory spine on the preopercle of both sides and the absence of modified body scales above the lateral line. All the specimens of M. zonurus had accessory spines on both sides, and most of them had modified body scales. The results of this study suggest that M. gibber should be treated as a subspecies or a synonym of M. zonurus. The nested clade analysis and the analysis of molecular variance (AMOVA) showed that the Japanese Malacocottus fishes are genetically homogenous over their geographical range. The mismatch distribution of the Japanese Malacocottus fishes indicated that a sudden population expansion had occurred recently. The contrast in phylogeographic structures between the Malacocottus fish and the zoarcid Bothrocara hollandi—the most dominant deep-sea demersal fish in the Japan Sea—might be attributed to the differences in the depths of the habitats and larval ecology between these two fishes.     

<Emphasis Type="Italic">Sebastapistes taeniophrys</Emphasis> (Fowler 1943): a valid scorpionfish (Scorpaenidae) from the Philippines

The poorly known scorpionfish, Scorpaena taeniophrys, originally described from two specimens from the Philippines, is redescribed as a valid species of Sebastapistes. Sebastapistes taeniophrys differs from all other congeners in having a combination of 15 pectoral-fin rays, 31–33 scale rows in longitudinal series, 11–14 pored lateral-line scales, 3 predorsal scale rows, 12 gill rakers, 3 suborbital spines, absence of coronal spines, lower opercular spine with a median ridge and not covered with scales, ctenoid body scales, several dark transverse bands on ventral surface of mandible, a distinct elongate black blotch distally between the second or third and seventh dorsal-fin spines, and no black blotch on the nape.     

Prey preference and feeding capacity of the larvae ofAblattaria arenaria [Coleoptera: Silphidae], a snail predator

The larval stages ofAblattaria arenaria were provided with 4 different snail species:Monacha syriaca (Ehrenberg),Xeropicta derbentina (Krynicki),Candidula sp., andZebrina eburnea (Pfeiffer) to determine if the prey species affected developmental time and food preference of larvae. Functional response of each larval stage ofA. arenaria was also tested for increasing density ofX. derbentina, the most common prey species found in association withA. arenaria locally. The developmental time of each larval stage did not show any statistical difference when fed with different snail species. The total developmental time from egg hatch to adult emergence was 19.0, 19.1, 18.0 and 21.4 days for prey speciesM. syriaca, X. derbentina, Candidula sp., andZ. eburnea, respectively. When prey was offered to larvae either as a single species or as combination of several species,M. syriaca was the most preferred. The prey least consumed wasCandula sp. when prey was given separately, andZ. eburnea was least preferred when other prey species were present in the arena. The 3^rd larval stage did not eat anyZ. eburnea if other prey species were present. The amount of prey consumed by the 1^st larval stage did not show any statistical differences with increasing density ofX. derbentina. But the response of 2^nd and 3^rd larval stages was very similar to each other although the amount of prey they consumed was very different. They both showed a rapid increase in consumption rate at early densities, then a negatively but slowly accelerated rise to plateaus at higher densities, a type-2 functional response curve. All larval stages were very sensitive to starvation. Mortality started after the 2^nd day, and all individuals of all larval stages were dead by the 5^th day.      

Morphological features of the larvae of spider crab <Emphasis Type="Italic">Pugettia quadridens</Emphasis> (Decapoda: Majidae) from the Northwestern Sea of Japan

The entire cycle of larval development of the spider crab Pugettia quadridens (de Haan, 1850) (Decapoda: Majidae), widespread in Peter the Great Bay (Sea of Japan) is studied under the laboratory conditions. The development cycle of this species comprises prezoea, zoea I, zoea II, and megalopa. At a temperature of 18–20° C larval development took from 11 to 15 days. Zoea II is described in detail for the first time. Many morphological characters are found distinguishing zoea and megalopa of P. Quadridens in Russian waters from the larvae of this species in Japanese and Korean waters. Some characters of larvae are similar in P. Quadridens and the related species of the genus Pugettia. The larvae of P. Quadridens occur in the plankton of Vostok Bay from late June to late October with a density up to 5 ind/m³ at a surface water temperature of 13–21°C. They are easily distinguished from the other brachyuran larvae of this region by the absence of lateral spines on the carapace.Original Russian Text Copyright © 2004 by Biologiya Morya, Kornienko, Korn.     

Spine number on the pecten and comb of fourth instar larvae of Aedes aegypti L. differences between two populations

Counts on four rows of spines, the two combs and the two pectens, in fourth instar larvae of the mosquito Aedes aegypti, have revealed consistent differences between two laboratory strains.Values of pecten spine number were normally distributed whereas the distribution of comb spines was bimodal. The sexes were identical in spine number. Left/right correlation (repeatability) was low for both sets of spines (comb, 0.13–0.22; pecten 0.37–0.45), implying a high stochastic component to variance within a single row. In one of two strains, a significant correlation was found between pecten and comb spine number Estimates of heritability for average pecten spine number (0.27–0.41) were obtained from selection data.Evidence is presented for stabilising selection for pecten spine number at the fourth larval instar under unfavourable rearing conditions. The intensity of selection has been estimated as 0.09–0.18.     

A new species of the sclerorhynchid sawfish Borodinopristis from the Campanian (Upper Cretaceous) of North Carolina,USA

Elasmobranch fossils recovered from Campanian marine exposures at Elizabethtown, Bladen County, NC, include species from at least seven genera of sharks and four genera of batoids. Of particular interest is the recovery of multiple isolated rostral spines from a new sclerorhynchid sawfish, Borodinopristis shannoni, sp. nov. Species of Borodinopristis are known from oral teeth and/or rostral spines (‘rostral teeth’ for some authors). In species known from the latter, the spines differ from those of other sclerorhynchids by the presence of one or more ‘collared’ barbs on the posterior margin of the crown. Unlike the previously described B. schwimmeri, the rostral spines of the new species have well-developed hooked barbs with collars (curved, connected crests) extending asymmetrically onto the dorsal and ventral surfaces of the spine, as well as small, rudimentary barbs. Also unlike B. schwimmeri, the anterior margin of the spine is strongly convex and there is no enamelled collar at the base of the crown. The new species also occurs in the Upper Cretaceous of the Gulf Coastal Plain.     

Phylogenetic Relationships Among Ten Sole Species (Soleidae,Pleuronectiformes) from the Gulf of Cádiz (Spain) Based on Mitochondrial DNA Sequences

The entire sequence of the mitochondrial cytochrome b gene and 2 partial sequences of the ribosomal RNA12S and 16S genes have been used to study the molecular phylogeny in 10 species of soles belonging to the genera Solea, Monochirus, Microchirus, Dicologlossa, and Synaptura from the Atlantic waters of the Gulf of Cádiz (Spain). The results obtained by means of different phylogenetic analyses (maximum likelihood, maximum parsimony, and neighbor-joining) were quite similar, supporting the monophyly of the Solea species. Nevertheless, they favor the differentiation of Dicologlossa cuneata and Dicologlossa hexophthalma in 2 distinct genera, since the most closely related species to the last one is Microchirus azevia. The fact that M. azevia is also more closely linked to Monochirus hispidus than to its congeneric Microchirus boscanion argues in favor of a taxonomic reorganization of these genera.