Cephalic Appendages Research Articles

Evolution of cephalic feeding structures and the phylogeny of Arthropoda

Focusing on structural and functional changes during the evolution of Arthropoda, we based our approach on evidence provided by two major Cambrian lagerstätten yielding exceptional preservation: the Lower Cambrian Chengjiang lagerstätte, Yunnan Province, China, and the Lower to Upper Cambrian ‘Orsten’-type lagerstätten with their 3D-preserved fossils. We established a model of major steps in the evolution of the arthropod feeding system, with emphasis on the head region. Using fossils, we identify two major gaps in our knowledge about this evolutionary process to be filled in the future. One of them is how development progressed from the stem arthropod level toward that of Arthropoda s. str. The latter stage is known now from three Chengjiang taxa, which possess, besides other features, a head composed of only two segments, i.e. those bearing the compound eyes and the limb-shaped antennulae. The post-antennular trunk limbs are very simple and lack any feeding structures, spines or setae. With this, only the antennula could have been involved in food gathering. Another uncertainty concerns the transition from the Arthropoda s. str. level to that of the Euarthropoda. Euarthropoda embraces all those well-sclerotized arthropods with extant descendants, and its ground pattern includes a larger head tagma with four appendage-bearing segments and post-antennular limbs made of a rigid, but flat gnathobasic basipod carrying two rami. At this stage, feeding had become more elaborate than before, yet all post-antennular appendages remained serially designed. Crustacea changed their feeding system initially by modifying the anterior three cephalic appendages, and the mouth area and by developing a specific setation on various body parts. Subsequently, more appendages became involved within certain in-group taxa. Our model elucidates that changes of the functional system occurred at the macroscopic and the microscopic level. Although many allied features, such as the gut system or the appendage morphology, remained remarkably conservative over longer periods, feeding was most likely a significant driving force for evolutionary changes in the morphology of arthropods, particularly of the head region.

Centropages behaviour: Swimming and vertical migration

The evolutionary success of any species living in a variable environment depends on its capacity to enhance the probability of finding food and mates, and escaping predators. In the case of copepods of the genus Centropages, as in all planktonic copepods, their swimming behaviour is closely tied to these vital aspects, and shows a high degree of plasticity and adaptive capacity. Swimming mechanisms of Centropages change radically during development, mainly in the transition between naupliar stages to the 1st copepodite; nauplii do not produce feeding currents, whereas copepodites do. Adults and late developmental stages of C. typicus, C. hamatus and C. velificatus spend most of the time in slow swimming and resting breaks, with occasional and brief fast swimming (escape reactions) and grooming events. Slow swimming is closely related to the creation of feeding currents, and results from the beating of the cephalic appendages in a “fling and clap” manner. The proportion of time allocated to the different swimming activities depends on sensory cues like type and concentration of food, presence of potential mates, light intensity, hydrodynamic flow, etc. The responses of Centropages to changes in flow velocity fluctuations (small-scale turbulence) are similar to the escape responses (fast swimming) triggered by the presence of potential predators. Centropages generally have standard nocturnal vertical migration patterns involving considerable vertical displacements. This behaviour is closely related to the narrow spectral sensitivity and the low intensity threshold of the genus, and has important consequences for the active vertical transport of matter and energy. The variety of responses of Centropages to environmental changes, and in general all the aspects related to its swimming behaviour seem to be controlled by the trade-off between energetic gains (food intake), losses (swimming energy expenditure), and predation risk. Behavioural plasticity and adaptation appear to be the most relevant characteristics for the success of the genus in a wide range of marine environments.

Morphology of Megalopa and First Crab of Cyrtograpsus Angulatus, with Comments on the Presence of an Anomalous First Crab Stage in Brachyuran Crabs

Abstract Megalopal and first crab stage morphology of Cyrtograpsus angulatus Dana was studied in specimens from Mar Chiquita Lagoon, Argentina and an identification key for the megalopae of the four southwestern Atlantic varunid crabs is proposed. Some anomalous first crabs were observed that differed in the carapace shape and in the orientation of the ocular peduncle. These crabs survived in laboratory cultures, molting to the following stage with normal aspect. An anomalous Chasmagnathus granulatus first crab was also found in the field. We speculate that these odd crabs appeared after a complete, but defective, ecdysis. Since the ultimate body structures to be separated from the exuvia are probably the cephalic appendages and the eyes, their survival in the field would be difficult since vision may help them to detect predators.

Juvenile morphology of the xanthid crab Leptodius exaratus (H. Milne-Edwards, 1834) (Decapoda: Brachyura), with notes on the appearance of sexual dimorphism

Summary The morphometrical and meristic features of the carapace, cephalic appendages (antenna, antennule), mouthparts (maxillule, maxilla, first-third maxillipeds), sternum, pereiopods, abdomen, and pleopods of juveniles and the onset of morphological sexual dimorphism were described for the xanthid crab Leptodius exaratus (H. Milne Edwards, 1834), based on laboratory-reared and wild adult specimens collected from Tateyama Bay, Japan. First instar juveniles shared some of the features of adults (e.g. gross appearance of the carapace and cheliped propodus proportions), but differed from adults on almost all other morphological parameter examined. Morphological development was still not complete at the ninth instar; extrapolation from the rate of morphological changes between instars 1–9 suggests that L. exaratus requires about 13 ecdyses to transform into adults, including development of reproductive structures. Differences in the number and morphology of pleopods and abdomen width allowed early distinction of the sexes. Thus, males formed gonopods in the first abdominal somite and lost the paired vestigial pleopods in somites 3–5 from the fourth instar; females retained the pleopods in somites 2–5, but these became biramous and had increased setation. The abdomen grew wider in females than in males from the fifth instar. Several morphological features of juveniles have phylogenetic and taxonomic implications: carapace motifs clearly place L. exaratus in the superfamily Xanthoidea, whereas the patterns of setation in the scaphognathite and first maxilliped epipod allow separation of this (xanthid) species from crabs of other Xanthoidean families.

(736): Continuous regional anesthesia of maxillary nerve: Anatomical base of a new lateral approach to pterygopalatine fossa

Craniofacial surgery pain treatment is one of the important and not yet resolved issues. Some studies demonstrated the interest of regional anaesthesia and analgesia. The aim of our study was to assess the feasibility of maxillary nerve block with the help of a catheter placed in the pterygopalatine fossa by a supra-zygomatic approach. Anthropomorphic measurements between foramen rotundum and selected bone landmarks (temporal margin of the zygomatic bone and infratemporal crest of the great wing of the sphenoid bone) were performed on 21 dry skulls (42 sides). The angle between distances from temporal margin of the zygomatic bone to the infratemporal crest and to the foramen rotundum was calculated for each side of dry skulls. Eight micro-anatomical dissections (four cephalic extremities) were performed with supra-zygomatic or trans-zygomatic approaches to the pterygopalatine fossa with the aim to explore anatomic relationship between maxillary nerve, sphenopalatine artery and venous plexus. In two specimens before dissection the insertion of the needle with a catheter to the pterygopalatin fossa by suprazygomatic approach with calculated angle of 7,6° ± 6,5 (mean± SD) in an inferior and posterior direction was performed with the progression up to 18,9 mm± 0,4 between the infratemporal crest and the final position of the needle. Five ml of the radio-opaque solution was injected via catheter and CT scan revealed solution in the pterygopalatine fossa, immersing maxillary nerve. In this described position the needle is far from the vascular structures and in a perpendicular direction with the inferior orbital fissure. Our technique of pterygopalatine fossa catheterize for maxillary nerve block is an easy and safe procedure. It seems that supra-zygomatic approach has no risk of complications such intra cranial penetration or orbital penetration. Randomised study should confirm the benefice of the supra-zygomatic approach in term of anaesthesia and analgesia.

An aglaspidid arthropod from the Upper Ordovician of Morocco with remarks on the affinities and limitations of Aglaspidida

ABSTRACTA new aglaspidid arthropod, Chlupacaris dubia gen. et sp. nov., is described from the Pusgillian (lower Ashgill, Upper Ordovician) Upper Tiouririne Formation near Erfoud, southeastern Morocco. Although disarticulated, careful documenting of the tergites allows a reconstruction of the exoskeleton to be made. Although somewhat trilobite-like in appearance, the lack of facial sutures, a well-defined axis with articulating half-rings and a pygidium clearly prove Chlupacaris gen. nov. is not a trilobite. An interesting feature is the presence of a hypostome in this non-trilobite arthropod. In contrast to other aglaspidids usually considered to be carnivorous, a filter-feeding mode of life is proposed for Chlupacaris gen. nov., based on the strongly vaulted cephalon, subvertical orientation of the hypostome and less strongly vaulted trunk. Chlupacaris gen. nov. is probably most closely related to the atypical aglaspidid Tremaglaspis unite from the Tremadoc (Lower Ordovician) of the U.K., but it can also be tentatively linked to the problematic Lower Cambrian arthropods Kodymirus vagans and Kockurus grandis from the Czech Republic. The relevance and validity of previous definitions and of possibly significant characters used for identifying aglaspidids are evaluated, and as a result, a new combination of characters diagnosing Aglaspidida is proposed. Contrary to previous reports, it is suggested that aglaspidids are probably more closely related to trilobites than they are to chelicerates. This notion may be supported by the shared possession of a mineralised cuticle, a possibly similar number of cephalic appendages, and the presence of a hypostome in some forms, although this last character may alternatively be homoplastic.

Descriptions of the preimaginal stages of Lancetes marginatus (Steinheil) and L. biremis Říha (Coleoptera: Dytiscidae), and comparative notes with other Lancetes larvae

All the preimaginal stages of Lancetes marginatus (Steinheil) and third instar larva of L. biremis Říha are described and figured for the first time. Detailed analyses of the morphometry, chaetotaxy and porotaxy are provided, and comparisons with the immatures of other species of the genus are included. The larvae described have multifragmented urogomphi, the only larval synapomorphy that defines the genus Lancetes Sharp. Third instars also present a secondary subdivision in some of the cephalic appendages, which is a synapomorphy of Lancetes plus Dytiscinae. First instar larva of L. marginatus is distinguished from the remaining known first instars of Lancetes by the absence of primary pores FRe and MXa, and the presence of one additional minute seta on the dorsal surface of antennomere 4 and one additional pore on the urogomphus. The third instar of L. marginatus is unique by the absence of secondary dorsal setae on the femur. The pupa of L. marginatus differs from that of L. angusticollis by the presence of fewer setae on the head, pronotum and abdominal terga V to VIII.

Place du lambeau nasogénien dans les reconstructions du plancher buccal

Subject. – Oral cavity cancers represent 30% of the cephalic extremity tumors. Their resection requires in the majority of the cases a reconstruction by soft tissue. The reconstruction must be simple by bringing some reliable, hairless, thin, resistant tissue to radiation therapy, with a limited morbidity and an acceptable scar ransom. Purpose. – The purpose of our study is to define the place and the limits of nasolabial flap in the reconstruction of the anterior floor of the mouth after tumoral resection compared to the other surgical and microsurgical techniques. Material and method. – We retrospectively studied patients with oral cancerous lesions of the anterior floor of the mouth reconstructed by nasolabial flap between 1997 and 2002. The patients benefited from a surgical resection of the tumor by respecting the safety margins, with an immediate reconstruction allowing the restoring of the oral functions. We tried to describe the limits of this flap and discussed its modalities of vascularization. Results. – Fifty-three flap procedures were performed on 47 patients; forty-one have received a unilateral and 6 a bilateral nasolabial flap. The majority of tumors were squamous cell carcinomas (50 cases). The average age of patients were 64.8 years (45–78 years) with 40 men (75%) and 13 women (25%). A radical neck lymph nodes dissection with facial artery ligation was realized for 21 patients (15 ipsilateral and 3 bilateral) without affecting the outcome. As complications, we noted one complete necrosis and two partial necrosis of the flap, two postoperative wound complications with dehiscence as well as a massive local recurrence of initial tumor in one patient. Conclusion. – The nasolabial flap represents a simple functional and morphological option to other pedicled or microsurgically anastomosed flaps for the reconstruction of intermediate-sized mouth floor defects.

Distribuição dos diagnósticos de lesões pré-neoplásicas e neoplásicas de pele no Hospital Universitário Evangélico de Curitiba

FUNDAMENTOS: O câncer de pele é mais comum nas populações de pele branca. Quanto aos tumores de pele, o CBC é o mais freqüente. Das lesões pré-cancerosas, a que ocorre com mais freqüência é a ceratose actínica, que se torna maligna em percentual variável de 20 a 25% dos casos. OBJETIVO: Analisar a ocorrência e os locais do corpo mais acometidos por lesões cancerosas de pele e também pela ceratose actínica. MÉTODOS: Estudo retrospectivo que analisou, em 2002, biópsias de pele de 491 pacientes com diagnóstico de ceratose actínica, CBC, CEC ou melanoma, resultando em 531 diagnósticos registrados pelo Serviço de Anatomia Patológica de um hospital universitário de Curitiba. RESULTADOS: Em amostra de 270 (54,99%) mulheres e 221 (45,01%) homens, o CBC (58,46% - 114/195) e o melanoma (61,5% - 16/26), assim como a ceratose actínica (60,79% - 107/176), acometeram mais o sexo feminino. O CEC prevaleceu no sexo masculino (64,39% - 61/94). Dos 531 diagnósticos, 62,90% (334) apontaram tumores malignos de pele, sendo o CBC o mais encontrado (39,74% - 211), e correspondendo 37,10% (197) à ceratose actínica. Quanto à localização das lesões, houve maior acometimento na extremidade cefálica, que atingiu 50,47% (268) dos casos. Em relação ao melanoma, três localizações foram mais prevalentes (dorso, região malar e pé), cada uma com 11,50% (3/26). CONCLUSÕES: O CBC foi o tumor mais encontrado nos laudos analisados. O sexo feminino foi o mais acometido. Houve maior prevalência nas sexta e sétima décadas. A extremidade cefálica foi a localização mais comum das lesões estudadas, com exceção do melanoma, que ocorreu mais no dorso, região malar e pé

Relation of behavior of copepod juveniles to potential predation by omnivorous copepods: an empirical-modeling study

An empirical-modeling study was carried out to examine the motion behavior of cope- pod nauplii in relation to their potential predation by omnivorous copepods. First, video observations were taken on the encounters of Centropages velificatus, Paracalanus aculeatus, Paracalanus quasi- modo and Temora stylifera nauplii with free-swimming adult females of C. velificatus. By examining each female's behavior, the observed encounters were arranged into 3 categories: (1) quasi-steady, (2) unsteady, and (3) unsteady with body rotation. We found that a wide spectrum of motion behaviors contributes to the generation of hydrodynamic signals. A hydrodynamic model was developed to analyze 4 encounters under the quasi-steady category. The model takes into account the effects of the finite-sized body morphology and the no-slip boundary condition imposed at the surface of the nauplius. Therefore, the model is able to calculate the tip-base velocity differences, as well as the tip-base shear rates over the length of the setae of the A1 (first antennae) of the nauplii, resulting from the flow disturbances generated by a steadily approaching C. velificatus female. When the tip-base shear rates around its A1 setae reached the range of 3.0 to 4.8 s -1 , a C. velificatus nauplius, moving only occasionally, detected the approaching female copepod. By contrast, a P. quasimodo nauplius and a T. stylifera nauplius, both moving continuously by beating their cephalic appendages, did not detect the female, even when the tip-base shear rates reached the range of 5.2 to 6.2 s -1 for the former and 8.4 to 11.4 s -1 for the latter. The modeling results also reveal the cause of the difference in the sensitivity to hydrodynamic signals. Nauplii moving only occasionally have a much weaker noise field (originating from the naupliar self-generated flow) around their A1 setae than those moving their cephalic appendages continuously to achieve a smooth and continuous motion pattern, and therefore are better suited to perceiving nearby predators. This model provides a mechanistic under- standing as to why continuously moving nauplii are preyed upon at a higher rate than those moving intermittently.

The phylogeny of arachnomorph arthropods and the origin of the Chelicerata

ABSTRACTA new hypothesis of the relationships between arachnomorph arthropods, and the origin of chelicerates, is presented based on a cladistic analysis of 34 taxa and 54 characters. The present study provides a detailed discussion of primary hypotheses of homology and includes a more complete range of terminal taxa than previous analyses. The analysis provides the first convincing synapomorphies for the Arachnomorpha, and suggests that the marrellomorphs are not arachnomorphs. The assignment of Cambrian ‘great appendage’ (or megacheiran) arthropods to the Arachnomorpha is confirmed, and potential synapomorphies uniting them with chelicerates are discussed and tested. Principal amongst these are the loss of the first cephalic appendages (the antennae), loss of the exopods of the second cephalic appendages and modification of the endopods of these appendages into spinose grasping organs. The Arachnomorpha consists of two major clades: (1) a ‘chelicerate-allied’ clade, including chelicerates, megacheirans, Emeraldella, Sidneyia, cheloniellids and aglaspidids, in which chelicerates and a paraphyletic group of megacherian arthropods form the sister group to the remaining taxa; and; (2) a ‘trilobite-allied’ clade, including trilobites, xandarellids, helmetiids, tegopeltids and naraoiids, the relationships of which are more fully resolved than in previous studies.

The Larva of Matus leechi Young (Coleoptera: Adephaga: Dytiscidae): Implications for the Larval Ground Plan of the Genus Matus Aubé

Description of the second instar of Matus leechi Young (Coleoptera: Adephaga: Dytiscidae) is presented including a chaetotaxic and porotaxic analysis of the cephalic capsule, head appendages, legs, last abdominal segment and urogomphi. Larvae of M. leechi are distinguished from those of other species of the genus Matus Aubé by (1) the non-pseudochelate pro- and mesothoracic tibiae, (2) the presence of spatulate lamellae clypeales, (3) the absence of secondary setae on the cephalic appendages, and (4) the very elongated urogomphi. It is postulated that the pseudochelate legs found in other species of Matus evolved within the genus Matus.

Role of olfactory appendages in chemically mediated orientation of blue crabs

Benthic crustaceans such as the blue crab Callinectes sapidus use various sensory appendages to navigate chemical plumes. We characterized the role of different sensory structures in blue crabs during olfactory search by deafferenting (i.e. removing or rendering inactive) particular sensor populations and by quantifying odor-plume structure and flow dynamics. Our results indicate that blue crabs use both cephalic and thoracic appendages for olfactory-mediated orientation. Cephalic chemosensor deafferentation decreased search success, reduced walking speed and increased the duration of stationary periods. All these deficiencies are manifestations of the inability of crabs to sustain upstream progress. Crabs subjected to deafferentation of thoracic sensilla failed to correctly track the narrowing plume and showed an increased frequency of large course-corrections. Whereas cephalic sensors clearly function in motivating upstream movement during the search process, thoracic receptors aid in source localization. The differing functional roles of these 2 sets of appendages may be associated with different signal characteristics impinging on their chemosensor populations. Intermittent but intense signals received by the cephalic appendages may enable the crabs to identify attractive odors and sustain searching. Chemical signals impinging on legs are more homogeneous and may allow the crabs to acquire better information on the spatial patterns of chemical signal structure that are important for navigation. The simultaneous use of chemical signals at differing heights in the plume suggest that the 3D structure of these plumes is important for foraging success, and that different populations of neural receptors may be tuned to operate optimally in particular signal environments.

The first zoeal stage of the genus Cronius (Brachyura, Portunidae) from the Brazilian coast, hatched in a laboratory

This study describes the first zoeal stage of Cronius ruber and Cronius tumidulus. The zoeae can be distinguished using the setation of the cephalic appendages and the lateral process on the abdominal somite.

Larval morphology of genusLancetes(Coleoptera: Adephaga: Dytiscidae): the hypothesis of sister-group relationship with the subfamily Dytiscinae revisited

AbstractDescriptions of the larvae ofLancetes angusticollis(Curtis),L.lanceolatus(Clark),L.subseriatusZimmermann,L.flavoscutatusEnderlein,L.delkeskampiRíha, andL.nigriceps(Erichson) are provided. Characters from larval morphology are analyzed to infer the phylogenetic relationships of the genusLancetesSharp with other genera of Dytiscidae. A parsimony analysis based on 51 informative larval characteristics was conducted with the program NONA. The most parsimonious tree supports a sister-group relationship between the genusLancetesand members of the subfamily Dytiscinae. The only unambiguous synapomorphy in support of this hypothesis is the secondary subdivision of some cephalic appendages. Other putative synapomorphies are the proximal articulation of the primary seta CO7 both on meso- and meta-coxa and the presence of additional primary setae on the ventral margin of the tibiae. Based on several character states including the presence of multifragmented urogomphi, the genusLancetesis monophyletic.

Chemoreception and the deformationof the active space in freely swimming copepods: a numerical study

A three-dimensional alga-tracking, chemical advection–diffusion model was used to calculate the deformation of the active space surrounding an alga entrained within the flow field around a freely swimming copepod. From the model, the advance warning time resulting from the copepod's chemo-reception of the entrained alga was quantified, and copepod chemoreception capability compared for several different swimming behaviors: hovering in the water, swimming slowly (swimming upward, swimming backward and swimming forward), swimming fast (swimming upward, swimming backward and swimming forward) and sinking (with the anterior pointing upward or downward). The results show that when it hovers or swims slowly, a copepod can use chemoreception to remotely detect individual algae entrained by the flow field around itself. In contrast, a fast-swimming copepod is not able to rely on chemoreception to remotely detect individual algae. The possibility of a free-sinking copepod using chemoreception to detect algal particles is also indicated. It is shown that advection by the fluid motion dominates over diffusion in transporting the chemical signals inside the active space to the location of a copepod's chemoreceptors. The feeding current structure for a hovering copepod is described. It is suggested that the feeding current structure and re-routing or re-orienting response by a copepod in response to its antennule or other cephalic appendage inputs allow the copepod to capture the food particles that would otherwise pass outside its capture area and increase the amount of food captured.

The flow field around a freely swimming copepod in steady motion. Part I: Theoretical analysis

The three-dimensional flow field around a free-swimming copepod in steady motion was studied theoretically. This study was based on coupling the Navier-Stokes equations with the dynamic equations for an idealized body of a copepod. To allow analytical solutions to the flow field, three simplifications were made: (a) to simulate the effect of the beating movement of the cephalic appendages, a force-field was added to the Navier-Stokes equations, (b) to linearize the problem, Stokes flow was used, and (c) to simplify the morphologies of the copepods, a spherical body shape was assumed. Analytical solutions were derived for five steady motions: (1) hovering, (2) sinking, (3) upwards swimming, (4) backwards swimming and (5) forwards swimming. The results show that the geometry of the flow field around a freely swimming copepod varies significantly with the different swimming behaviours. When a copepod hovers in the water, or swims very slowly, it generates a wide, cone-shaped flow field. In contrast, when a copepod sinks, or swims fast, the flow geometry is not cone-shaped, but cylindrical, narrow and long. These results are consistent with published observations on live copepods. It is shown that the differences in the flow geometry with the different swimming behaviours are due to the relative importance between the two factors in generating the flow field: the copepod's swimming motion and the requirement to counterbalance the copepod's excess weight. The results also highlight the importance of considering freely swimming copepods as self-propelled rather than as towed bodies. Self-propelled' means a freely swimming copepod must gain thrust from the surrounding water in order to counterbalance the dragforce by water and its excess weight. Regardless of swimming behaviours and velocities, the far-field velocity field decays to that of the velocity field generated by a point force of magnitude equal to the copepod's excess weight in an infinite domain. On the other hand, using the towed body model yields a flow field with much different far- and nearfield flow characteristics. Hence, the towed body model is inherently unable to reproduce fundamental characteristics of the flow field around a freely swimming copepod.

The flow field around a freely swimming copepod in steady motion. Part II: Numerical simulation

Three-dimensional, numerical simulations of the flow field around a freely swimming model-copepod were performed using a finite-volume code. The model copepod had a realistic body shape represented by a curvilinear body-fitted coordinate system. The beating movement of the cephalic appendages was replaced by a distributed force field acting on the water ventrally adjacent to the copepod's body. In the simulations, we took into account that freely swimming copepods are self-propelled bodies through properly coupling the Navier-Stokes equations with the dynamic equation for the copepod's body. Flow fields were calculated for five steady motions: (1) hovering, (2) sinking, (3) upwards swimming, (4) backwards swimming and (5) forwards swimming The numerical results confirm the conclusions drawn from the theoretical analysis using Stokes flow models by Jiang et al. [in a companion paper (fiang et al., 2002a)] for a spherical copepod shape and show that the geometry of the flow field around a freely swimming copepod varies significantly with the different swimming behaviours. When a copepod hovers in the water, or swims very slowly, it generates a cone-shaped and wide flow field. In contrast, when a copepod sinks, or swims fast, the flow geometry is not cone-shaped, but cylindrical, narrow and long. The relationships between copepods'swimming behaviour and body orientation, hydrodynamic conspicuousness, energetics as well as feeding efficiency were discussed, based on the simulation data. It is shown that the behaviour of hovering or swimming slowly is more energetically efficient in terms of relative capture volume per energy expended than the behaviour of swimming fast, i.e. for a same amount of energy expended a hovering or slow-swimming copepod is able to scan more water than a fast-swimming one. The numerical results also suggest that the flow field generated by a fast-swimming copepod enables the copepod to use mechanoreception to perceive the food/prey and therefore increases the food concentration in the swept volume and that the flow field around a free-sinking copepod favours the copepod's mechanoreception while minimizing the energy expense, so that the energy budget can still be maintained for both cases.

The African Carnoyidae (Nematoda: Rhigonematida). 4. Abirovulva insolita gen. n., sp. n., parasite of Coromus thomsoni (Polydesmida: Oxydesmidae) from Ivory Coast

AbstractAbirovulva gen. n. is proposed for nematode denizens of the gut of various African polydesmid diplopods (Coromus thomsoni , Oxydesmus mimodesmus parabellus , O. sicarius , O. platycercus concolor , Plagiodesmus brunneus , P. variabilis and Prepodesmus ornatus). The new genus is usually accompanied by species of Afrocarnoya (also apparently restricted to polydesmid diplopods) and Rhigonema and is likely to be distributed throughout the Central to West African region. Abirovulva gen. n. is unique amongst African Carnoyidae because of a combination of characters, including the very posteriorly located vulva, the unusual form of the female genital system, presence of a ventral sucker in the male, the shape of the spicules and gubernaculum and the distribution of the male copulatory papillae. Abirovulva insolita gen. n., sp. n. is proposed as the type species and is characterised by: the strongly inflated intestine just posterior to the basal bulb in both sexes, the extremely posterior vulva, both female genital tracts running anteriorly in parallel, presence of a much expanded vagina uterina acting as an egg receptacle, long and robust female tail spike; presence of a ventral sucker in the male, form of the male spicules and gubernaculum, disposition of the 15 copulatory papillae, cuticular callosities on the cloacal lips, well developed, smooth, cephalic cap in the male and the truncate male cephalic extremity. No other genus of African Carnoyidae is known to have such a posterior vulva, ventral sucker in the male or spicules and gubernaculum of such unusual form. Relationships to other genera in the Ransomnematoidea and factors that may influence niche partitioning within the host gut are discussed.

Larval morphology of the tribe Matini (Coleoptera: Dytiscidae, Colymbetinae): descriptions ofBatrachomatus daemeli,Matus bicarinatus, andAllomatus nannupand phylogenetic relationships

AbstractDescriptions are presented of larval instars of three species of the colymbetine tribe Matini Zimmermann (Coleoptera: Dytiscidae),Batrachomatus daemeli(Sharp),Matus bicarinatus(Say), andAllomatus nannupWatts, including a chaetotaxic and porotaxic analysis of the cephalic capsule, head appendages, legs, last abdominal segment, and urogomphi. A parsimony analysis based on 32 informative larval characteristics was conducted with the computer program NONA. Members of the Matini are postulated to share a monophyletic origin based on (i) seta TR2 articulated anteroventroproximally on the trochanter; (ii) seta TR5 elongate on the metatrochanter; (iii) seta TA1 elongate and inserted proximally on the tarsus; (iv) antenomere III with a hole-like ventroapical spinula; (v) prementum with the primary setae LA2, LA3, LA4, LA5, and LA8 spine-like and elongate; (vi) presence of secondary setae on the cephalic appendages; and (vii) presence of additional primary setae on the last abdominal segment. A clade Matini + Colymbetini is postulated based on (i) metafemoral seta FE5; (ii) metafemoral seta FE6; (iii) seta TI6 on tibia, all elongate and hair-like; (iv) one-segmented urogomphus; (v) presence of an occipital suture in first instar; (vi) galea elongate; (vii) presence of natatory setae on legs; and (viii) presence of secondary setae on the urogomphus.