The genera Ceratomyxa Thélohan, 1892, Leptotheca Thélohan, 1895 and Sphaeromyxa Thélohan, 1892 (Myxosporea: Bivalvulida) in gadid fish of the Northeast Atlantic

The gall-bladders of four species of gadid fish from the North Sea and Norwegian waters were examined for myxosporeans. The host species were cod Gadus morhua L. (350 examined), haddock Melanogrammus aeglefinus (L.) (592 examined), saithe Pollachius virens (L.) (205 examined) and whiting Merlangius merlangus (L.) (368 examined). Four species of myxosporeans are redescribed from these fish. Ceratomyxa arcuata Thélohan, 1892 was the most common species and was found in whiting (42.8%) and cod (0.6%). Leptotheca informis Auerbach, 1910 was found only in whiting (6.5%). L. longipes Auerbach, 1910 was found only in haddock (6.2%). Sphaeromyxa hellandi Auerbach, 1909 was found in haddock (9.1%) and whiting (0.3%). None of the saithe examined, and no cod or haddock from Norwegian waters, was infected with these myxosporeans. All four species appear to have distributions limited to the Northeast Atlantic, with S. hellandi having a more northern distribution than the other three. The validity of reports of C. arcuata, L. informis and L. longipes from outside this area is discussed.     

Storage and reproductive strategy of the carpet-shell clam,Ruditapes decussatus in the Gulf of Gabès (Tunisia)

In this study, the variations of glycogen concentrations in Ruditapes decussatus from Sfax coasts (Tunisia) were described in relation to the reproductive cycle. Separate analyses were made of gonad, adductor muscle and ‘remainder’. The timing of gametogenic development and spawning was evaluated using qualitative histology associated with image analysis including (1) the estimation of the gonadal occupation index (GOI), (2) surface area occupied by reserve tissues and (3) variation in oocyte diameter. The reproductive cycle of R. decussatus exhibited partial asynchronization between sexes, the major difference being observed in the duration of the spawning period. Contrary to previous studies, we observed continuous partial spawning (e.g. 50% of ripe oocytes still subsisted at the partial spawning stage). During the gametogenic cycle, GOI varied significantly in males and in females. Most oocytes were ripe and ready to spawn when their diameter reached or exceeded 45?µm. The expansion of gonad was inversely proportional to the development of the foot tissue. Glycogen concentration showed significant temporal variations between tissues, indicating the clear differentiation in energy storage between the clam organs.     

Divisional morphogenesis in the marine ciliate, Hemigastrostyla enigmatica (Dragesco & Dragesco-Kernéis, 1986) and redefinition of the genus Hemigastrostyla Song & Wilbert, 1997 (Protozoa, Ciliophora)

Morphogenetic events during the division of the marine hypotrichous ciliate, Hemigastrostyla enigmatica (Dragesco & Dragesco-Kernéis, 1986) Song & Wilbert, 1997 are described. The morphogenesis is characterized by:(1) 5 frontoventral-transverse cirral anlagen develop into 8 frontal, 5 ventral and 5 transverse cirri after Oxytricha-pattern;(2) there may be 6 FVT-anlagen in some individuals giving rise to more cirri which, however, will be resorbed after division;(3) anlage of the right marginal row at least in the opisthe occurs de novo right to the parental structures instead of within them;(4) according to the origin, the two extra ventral cirri right to transverse ones are not ventral or transverse cirri, which are from the retained old structure;(5) dorsal kineties originate from one group of DK-anlagen in both dividers with, very uniquely, an additional fragmentation of DK1, and(6) oral primordia will be formed in both dividing parts, from which the newly-built membranelles in the proter replace the posterior part of the parental AZM with a particular 'piecing together mode.Some features during the morphogenesis (e.g. variable number of cirral anlagen, presence of primary primordia, the mode of rebuilding of the proter's adoral zone of membranelles, origin of dorsal kineties and caudal cirri etc.) indicate that the genus Hemigastrostyla might present a intermediate form between oxytrichids and other related higher taxa. Based on our new observations, an improved diagnosis for genus Hemigastrostyla is given: marine or brackish water Oxytrichidae with slightly to conspicuously cephalized body shape; mostly 8–10 frontal, 5 ventral, 5 transverse and two to several extra ventral cirri to the right of the transverse ones, which are from the retained parental structure; caudal cirri present.     

Respiratory metabolism of the soft tick,Ornithodoros turicata (Dugès)

The rate of oxygen consumption was investigated in fed larval, nymphal and adult Ornithodoros turicata ticks and in starved nymphal and adult ticks. Oxygen consumption rate of fed adult ticks increased with increasing temperature. The metabolic rate of adult ticks was affected by starvation whereby starved adult ticks showed a significantly lower oxygen consumption than their fed counterparts. The oxygen consumption rate of fed female ticks was significantly higher than that of fed males but, there was no significant difference between the oxygen consumption rates of starved female versus starved male ticks. Oxygen consumption of fed larvae was significantly greater than those of fed first through third instar nymphs. Fed and starved nymphal ticks as well as fed adult ticks ventilated continuously. In contrast, starved adults ventilated discontinuously. The ability to reduce metabolic rate, plus the capability to ventilate discontinuously allow O. turicata adults to cope with prolonged starvation.     

Feeding kinematics and morphology of the alligator gar (Atractosteus spatula,Lacépède, 1803)

Living gars are a small clade of seven species that occupy an important position on the actinopterygian phylogenetic tree as members of Holostei, sister-group to teleosts, and exhibit many plesiomorphic traits used to interpret and reconstruct early osteichthyan feeding mechanisms. Previous studies of gar feeding kinematics have focused on the ram-based, lateral-snapping mode of prey capture found in the narrow-snouted Lepisosteus genus, whereas this study focuses on a member of the broad-snouted Atractosteus sister-genus, the alligator gar (Atractosteus spatula, Lacépède, 1803). High-speed videography reveals that the feeding system of alligator gars is capable of rapid expansion from anterior to posterior, timed in a way to generate suction, counteract the effects of a bow-wave during ram-feeding, and direct a unidirectional flow of water through the feeding system. Reconstructed contrast-enhanced μCT-based cranial anatomy and three-dimensional modeling of linkage mechanics show that a lateral-sliding palatoquadrate, flexible intrasuspensorial joint, pivoting interhyal, and retractable pectoral girdle increase the range of motion and expansive capabilities of the alligator gar feeding mechanism. Reconstructions of muscular anatomy, inferences from in vivo kinematics, and in situ manipulations show that input from the hyoid constrictors and hypaxials play an important role in decoupling and modulating the dual roles of the sternohyoideus during feeding: hyoid retraction (jaw opening) and hyoid rotation (pharyngeal expansion). The alligator gar possesses an intricate feeding mechanism, capable of precise control with plesiomorphic muscles that represent one of the many ways the ancestral osteichthyan feeding mechanism has been modified for prey capture.     

Predators and planariid competitors of the triclad Phagocata vitta (Dugés)

When Phagocata vitta, Crenobia alpina and Polycelis felina were exposed separately to each of seventeen potential invertebrate predators in the laboratory, only two stonefly species, Dinocras cephalotes and Perlodes microcephala, fed on the three triclad species, whilst the trichopteran Rhyacophila dorsalis ate the last two triclads. On exposing pairs of triclad species to D. cephalotes, significantly more P. felina than Ph. vitta were consumed, whereas similar numbers were eaten in each of the other two triclad combinations. Cannibalism and interspecific predation by triclad species were not observed. It is concluded that predation is unlikely to have a major influence in determining the observed distribution and abundance of triclad species in a Welsh study stream which harbours low numbers of effective predators.The de Wit model of competition was used to examine the competitive relationships between Ph. vitta, and C. alpina and P. felina, using chironomids or tubificid worms as food. In mixed cultures of Ph. vitta and P. felina fed on tubificids a stable equilibrium existed within the range of relative densities used in the experiments, whereas Ph. vitta was competitively superior to C. alpina in cultures fed on each of the food types, and to P. felina fed on chironomids. However, in theory, an equilibrium could occur when 10 or 6–7 times as many Ph. vitta as P. felina and C. alpina respectively are in the culture, when intraspecific rather than interspecific competition would become more important. Where the three triclad species coexist in the Welsh study stream, they are in similar numbers. This could imply that food is not limiting, with no consequent interspecific competition, or that the laboratory experiments were too simplistic to allow any interpretation of the field situation.     

The nassariids from the Gulf of Gabès revisited (Neogastropoda,Nassariidae)

Since the latter half of the nineteenth century, marine biologists have recognized that many molluscs living in the Gulf of Gabès, on the southern coast of Tunisia, exhibit a number of morphological characters that set them apart from the ‘typical form or variety’ that occurs in the rest of their Mediterranean distribution area. In the family Nassariidae, local forms (varieties or subspecies) were recognized as early as 1882, but none of these is currently recognized as having taxonomical significance. We have revisited the species-level systematics of the family using an integrative approach, based on morphological, geographic and molecular evidence (COI and 28S). Besides Tritia gibbosula (not sampled by us), we delimitated seven species, three with a broad range: Tritia neritea (probably introduced), T. mutabilis (but with considerable genetic structure between localities), and T. corniculum; and four not previously recognized as valid, and which may be considered Gulf of Gabès endemics: T. lanceolata, T. tenuicosta, T. pallaryana sp. nov. and T. djerbaensis sp. nov. Also, Tritia elongata is recognized as a valid species in the T. corniculum complex, with a distribution outside the Gulf of Gabès. It is remarkable that all have paucispiral protoconchs indicating non-planktotrophic larval development.

http://zoobank.org/urn:lsid:zoobank.org:pub:069F3B3B-66E8-4C07-A974-3023924426EB     

The Miocene mammal record of the Vallès-Penedès Basin (Catalonia)

The land mammal record of the Vallès-Penedès Basin (Catalonia, NE Spain) ranges from the early Miocene (Ramblian) to the late Miocene (Turolian), that is from about 20 to 7 Ma. Here we present an updated review of the mammal succession focusing on biochronology as well as on environmental and faunal changes. Based on faunal similarities with central Europe, we interpret this basin as a transitional zone between the forested environments of northern regions and the more arid landscapes of the inner Iberian Peninsula. The quality of the Vallès-Penedès record and its chronostratigraphic control is clearly better for the late Aragonian and the Vallesian (between 12.6–9.0 Ma), especially for small mammals. Therefore, we analyze small mammal diversity dynamics during this interval. Contrary to previous analyses, which found an abrupt extinction event coinciding with the early/late Vallesian boundary (the Vallesian Crisis), our results show that this pattern is due to uneven sampling. Instead, taxonomic richness slowly decreased since the late Vallesian as a result of a series of extinctions that mostly affected forest-dwelling taxa.     

Feeding Behavior, Habitat Use, and Abundance of the Angelfish Holacanthus passer (Pomacanthidae) in the Southern Sea of Cortés

Feeding behavior and habitat use of the king angelfish, Holacanthus passer, was studied in the southern Sea of Cortés, México. H. passer fed on benthic communities (algae and sessile invertebrates) and in the water column (mainly feces from the damselfish Chromis atrilobata). Although there were not significant differences in feeding rate between sexes, coprophagy was more common in males, while grazing was more common in females. Spatial distribution of size classes followed a pattern of decreasing size with increasing depth. Feeding rate was significantly different among habitats: small females had a higher feeding rate on the bottom, big females and small males had similar feeding rates from the bottom to 3m above the bottom, and big males had higher feeding rates from 5m above the bottom to the surface. Habitat was clearly partitioned, and there was significant habitat overlap only between big females and small males. The abundance of H. passer was partly explained (34% of the total variance) by the abundance of the damselfish C. atrilobata. There was a clear trophic association between C. atrilobata schools and H. passer feeding damselfish feces in the water column. The sex ratio male:female of H. passer populations was >1 at several sites, an unusual pattern for a protogynous fish. The sex ratio on the H. passer water column stock was also biased towards males at most sites. Although there is a positive relationship between C. atrilobata abundance and H. passer, there are factors other than damselfish abundance which cause this dominance of males.     

An improved description of Strombidium sulcatum Claparède & Lachmann, 1859 (Ciliophora) from slides of Fauré-Fremiet, and a designation of type material

Strombidium sulcatum, the type species of the genus, is examined using silver-stained material made by Fauré-Fremiet in the 1950s and 1960s. We found that the stained specimens possessed a prominent protuberance, as previously described; the number of anterior polykinetids (APk) differed between the accounts (15 this study, 12 previous reports); although previously illustrated, no contractile vacuole was observed; and the macronuclear shape, position, and size differed from those previously reported. Our work provides the first detailed re-analysis of the silver-stained material of S. sulcatum. We use data on S. sulcatum to distinguish it from a morphologically similar species, Strombidium inclinatum. Type material for S. sulcatum has been deposited in the Natural History Museum, London.     

Synopsis of the species of Ceratomyxa Thélohan, 1892 (Myxozoa: Myxosporea: Ceratomyxidae)

A synopsis of the species of Ceratomyxa Thélohan, 1892 (Myxozoa: Myxosporea: Ceratomyxidae), including a total of 147 species, is presented. For each species the relevant morphological and morphometric data are indicated, as well as the site of infection within the host and the original hosts and locality. A diagrammatic illustration of the spores is also provided.     

Sieve element characters and the systematic position ofAustrobaileya,Austrobaileyaceae—with comments to the distinction and definition of sieve cells and sieve-tube members

The ultrastructure of the sieve elements ofAustrobaileya is compared with that of angiosperm sieve tubes and gymnosperm sieve cells (mostly fromCycadales). Except for the size of the sieve poresAustrobaileya shares all ultrastructural characters (e.g., chromatolytic nuclear degeneration, presence of p-protein, formation of sieve pores from unbranched plasmodesmata) and other features (e.g., companion cells) with angiosperm sieve tubes. Gymnosperm sieve cells on the contrary are characterized by pycnotic nuclear degeneration, absence of p-protein, formation of sieve areas from branched plasmodesmata with median cavities. — The exact ordinal assignment ofAustrobaileya within the subclassMagnoliidae is still disputed, a placement close to eitherMyristicaceae andWinteraceae orMonimiaceae being possible as judged from both S-type sieve-element plastids and p-protein bodies. — On the basis of the ultrastructural results fromAustrobaileya it is proposed to reconsider concepts and terminology of sieve elements. i.e., to include features from sieve pore development, nuclei degeneration and presence of specific proteins into the definitions and to restrict the term sieve cell to gymnospermous sieve elements which differ much from those of other vascular plants.