Anterior Cephalothorax Research Articles

A new species of Pterodrilus (Branchiobdellida: Clitellata) from the upper Yadkin-Pee Dee River Basin of North Carolina

ABSTRACT A new species of branchiobdellidan, Pterodrilus leiteri n. sp., is described from the anterior cephalothorax of the crayfish Cambarus longulus from north-western North Carolina, USA. Like its 10 congener species, P. leiteri n. sp. is diminutive, with a maximum body length < 1 mm. It can be distinguished from other members of Pterodrilus by the number and position of dorsal ridges and projections. Unique to this species are three pairs of twinned dorsal unbranched digitiform projections on segments 3, 4, and 5. Our discovery adds to our understanding of diversity within an unusual and poorly understood genus, Pterodrilus, and more generally, branchiobdellidan fauna in the southeastern USA.

De novo transcriptome assembly and functional annotation for Y-organs of the blue crab (Callinectes sapidus), and analysis of differentially expressed genes during pre-molt

Blue crabs (Callinectes sapidus) undergo incremental growth involving the shedding (molting) of the old exoskeleton, and subsequent expansion and re-calcification of the newly synthesized one. The cellular events that lead to molting are triggered by steroid hormones termed ecdysteroids released from Y-organs, paired endocrine glands located in the anterior cephalothorax. The regulatory pathways leading to increased synthesis and release of ecdysteroids are not fully understood, and no transcriptome has yet been published for blue crab Y-organs. Here we report de novo transcriptome assembly and annotation for adult blue crab Y-organs, and differential gene expression (DGE) analysis between Y-organs of intermolt and premolt crabs. After trimming and quality assessment, a total of 91,819,458 reads from four cDNA libraries were assembled using Trinity to form the reference transcriptome. Trinity produced a total of 171,530 contigs coding for 150,388 predicted genes with an average contig length of 613 and an N50 of 940. Of these, TransDecoder predicted 31,661 open reading frames (ORFs), and 10,210 produced non-redundant blastx results through Trinotate annotation. Genes involved in multiple cell signaling pathways, including Ca2+ signaling, cGMP signaling, cAMP signaling, and mTOR signaling were present in the annotated reference transcriptome. DGE analysis showed in premolt Y-organs up-regulated genes involved in energy production, cholesterol metabolism, and exocytosis. The results provide insights into the transcriptome of blue crab Y-organs during a natural (rather than experimentally induced) molting cycle, and constitute a step forward in understanding the cellular mechanisms that underlie stage-specific changes in the synthesis and secretion of ecdysteroids by Y-organs.

The female cephalothorax of Stylops ovinae Noskiewicz &amp; Poluszyński, 1928 (Strepsiptera: Stylopida)

External and internal features of the female cephalothorax of the strepsipteran species Stylops ovinae (Stylopidae) are described in detail. Many derived features are closely related with the obligatory endoparasitism. A conspicuous characteristic is the secondary tagmosis with an anterior cephalothorax and a large, sack-shaped posterior body region. The cephalothorax comprises the head, thorax and anterior half of abdominal segment I and protrudes from the host’s abdomen. It contains the mouth and birth opening, vestiges of cephalic appendages, and most internal organs including the large Nassonov’s glands. The posterior body part contains mainly the reproductive organs. The constriction of abdominal segment I probably prevents the exposed anterior body from slipping back into host’s body cavity. The narrow mouth opening is used for the uptake of the host’s hemolymph by the secondary larval stage and is maintained as a non-functional structure by the adult females. The tentorium is absent. The mandibles are immobilized in the adult female. They are used for penetrating the host’s body wall by the second larval instar. The brood canal formed by the larval and pupal exuvia is an autapomorphy of Stylopidia, the birth opening where the first instars are released from the female an autapomorphy of Stylopiformia, and the cephalothoracic invagination an autapomorphy of Stylops. A single pair of functional spiracles is laterally placed on abdominal segment I. An unusual circular hemolymph vessel is present in the pharyngeal region. The brain is shifted to the thorax. The suboesophageal complex and the thoracic and abdominal ganglia form a single ganglionic mass in the thoracic region. The musculature of the cephalothorax is extremely reduced. Nassonov’s glands, which produce sex pheromones, are the largest internal structures in the cephalothorax. Despite of the loss of the digestive function, the digestive tract is not degenerated including a foregut with well-developed muscles.

Comparative morphology of the hemolymph vascular system in krill (Euphausiacea; Crustacea)

The phylogenetic position of Euphausiacea within Malacostraca is still under debate. Either they are seen as sister group to a taxon comprising Pancarida and Peracarida or closer related to Decapoda. Both hypotheses can be supported by characters of the circulatory system. Therefore, a comparative re-evaluation of the circulatory system seems to be feasible. Here we present the first three-dimensional data of the circulatory system of three euphausiacean species based on semi-thin sections and micro computer tomography in combination with corrosion casting. We were also able to study for the first time representatives of Bentheuphausia amblyops, the suggested sister taxon to all other euphausiaceans. The main pumping structure in the open circulatory system of Euphausiacea is the globular heart in the rear thoracic segments. From the anterior and posterior end of the heart two unpaired and four pairs of arteries emanate. The unpaired anterior aorta runs below the carapace from the anterior part of the heart into the anterior cephalothorax, where it supplies the first antennae, the brain and the eyes. The paired posterior aortae run into the pleon supplying the pleopods, uropods and the telson. The four pairs of cardiac arteries supply appendages in the cephalic region and viscera in the trunk. The unpaired descending artery connects to the subneural vessel supplying the thoracopods. A myoarterial formation of the anterior aorta is described in Bentheuphausia amblyops. The observed pattern of a globular heart situated in the posterior cephalothorax and comprising a meshwork of musclular strands (also running through its lumen) is highly likely to be homologous in Euphausiacea and Decapoda. The data are compared with the scarce literature present to date.

The Hemolymph Vascular System in Tethysbaena Argentarii (Thermosbaenacea: Monodellidae) as Revealed by 3D Reconstructions of Semi-Thin Sections

Abstract This paper is part of a comparative survey on the evolutionary morphology of the circulatory system in Malacostraca. Tethysbaena agentarii is a representative of Thermosbaenacea, a group which exhibits a relict distribution in cave or groundwater habitats. The study presents the first three dimensional data concerning the circulatory organs and their spatial relationships to other major organ systems. T. argentarii has a short dumbbell-shaped heart which lies in the posterior cephalothorax and the first free thoracic segment. It is equipped with one pair of incurrent ostia. The only vessel to emanate from the heart is the anterior aorta, which runs into the anterior cephalothorax and supplies the central nervous system and both pairs of antennae. Comparative and functional aspects of the circulatory system are discussed. The features of this highly reduced vascular system point to a closer phylogenetic relationship between Thermosbaenacea, and Spelaeogriphacea and Mictocarididae (Mictacea).

Morphology of the haemolymph vascular system in Tanaidacea and Cumacea: – Implications for the relationships of “core group” Peracarida (Malacostraca; Crustacea)

Tanaidacea and Cumacea are crucial for understanding the phylogenetic relationships of “core group” peracarids. Here, the haemolymph vascular system in three tanaidacean and four cumacean species was studied on the basis of histological sections and 3D reconstruction. The circulatory organs in Tanaidacea include a tubular heart which extends through most of the thorax. It is extended into the cephalothorax by an anterior aorta. Haemolymph enters the heart through one to two pairs of incurrent ostia. Up to five pairs of cardiac arteries emanate from the heart to supply viscera in the body cavity. In the anterior cephalothorax, the aorta forms a pericerebral ring from which the arteries for the brain and the antennae branch off. In Cumacea, the heart is shorter but more voluminous. In all cumaceans studied, five pairs of cardiac arteries supply the thoracopods and the pleon. The single pair of ostia is situated in the centre of the heart. The anterior aorta runs into the anterior cephalothorax where it supplies the brain and antennae. This paper provides a general comparative discussion of all available data from the literature and the data provided herein. In certain details, the haemolymph vascular system of the Tanaidacea resembles that of Amphipoda, and some correspondences between Cumacea and Isopoda are pointed out. These findings might support a closer relationship between the latter two taxa while they show no support for an amphipod/isopod clade.

The circulatory system and its spatial relations to other major organ systems in Spelaeogriphacea and Mictacea (Malacostraca, Crustacea) - a three-dimensional analysis

Spelaeogriphacea and Mictacea are enigmatic taxa within malacostracan crustaceans that play a pivotal role in peracarid phylogeny. Anatomical data on both taxa that are suitable for use in cladistic analyses are still scarce. Here, we provide for the first time detailed three-dimensional information on the major organ systems of Spelaeogriphacea and Mictacea (the circulatory system, the digestive system, and the central nervous system) using semithin sections in combination with computer aided three-dimensional reconstruction techniques. The digestive system in both Spelaeogriphus lepidops and Mictocaris halope is made up of a short oesophagus leading to a voluminous stomach chamber. Posteriorly, a pylorus is attached to the stomach chamber. An antechamber of the midgut glands is situated at the transition into the midgut, from which up to four tubular midgut glands emanate. The midgut is a straight tube running through the body terminating in a short hindgut. The central nervous system in the cephalothorax is made up of a brain and a suboesophageal ganglion. Both species show some reduction of the protocerebrum caused by the lack of eyes. The circulatory system is made up of a tubular heart that is situated in the thorax. It is equipped with two pairs of incurrent ostia in S. lepidops and one pair in M. halope. The only artery leading off the heart is the anterior aorta, which runs into the cephalothorax. A dilation is formed between the brain and the anterior stomach wall, into which oesophageal dilator muscles are internalized. The function of this so-called ‘myoarterial formation a’ as an accessory pulsatile structure in the anterior cephalothorax of these animals is discussed. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 149, 629–642.

The transverse apodeme bridge from the cephalothorax of Amphipoda (Crustacea) and its significance for systematics

There is a striking anatomical diversity in an apodeme pair that protrudes into the cephalothorax of amphipod crustaceans between maxilla 1 and 2. In the hypothetical plesiomorphic state these apodemes are very short and separate and are coupled by a strand of connective tissue. In the eusirid-calliopiid group the apodemes meet and are wedged together by their dentate medial margins. Iphimediidae show a similar condition, but have a pair of frontal processes that are connected to the anterior cephalothorax wall. Within the Hyperiidea the orientation of the apodemes has changed from the transverse to the longitudinal direction. In the gammarid-melitid family group the apodemes are fused into a complete cuticular bridge. This character turned out to be the only synapomorphy for this taxon, and can be used to test the referral of certain genera to this family group. The functional morphology of these apodemes and their role as a site of insertion for the muscles of mouthparts and trunk muscles is briefly discussed.

Cardiovascular system of the blue crab Callinectes sapidus.

The circulatory system of adult blue crabs, Callinectes sapidus, was mapped by either injecting barium sulfate into intact animals followed by radiography or by resin corrosion casts (Batsons Monomer). Seven arteries arise from the heart. The anterior aorta exits from the anterior dorsal surface of the heart and gives rise to the optic arteries; these arteries supply hemolymph to the supraesophageal ganglion and eyestalks. The paired anterolateral arteries also exit from the anterior dorsal surface of the heart and supply hemolymph to the gonads, hepatopancreas, stomach, antennal gland, mandibular muscles, and the hypodermis of the anterior cephalothorax. The paired hepatic arteries exit the heart anteriorly and ventrally and branch profusely within the hepatopancreas. A smaller side branch, the pyloric hepatic artery, supplies hemolymph to the pyloric stomach and midgut. The smallest artery, the posterior aorta, branches off the posterior ventral surface of the heart; it joins with the inferior abdominal artery in the region of the second abdominal segment and these arteries supply hemolymph to the hindgut and abdomen. The largest artery is the sternal artery, which exits from the ventral surface of the heart; the ventral thoracic artery branches off the sternal artery and supplies hemolymph to the chelae, the mouthparts, and to each pereiopod. The present study shows that the circulatory system is highly developed, with arteries dividing into smaller capillary-like vessels that ramify profusely within individual organs. The return vessels, the sinuses, are discrete channels rather than random open spaces, as previously described. The present study refines and advances descriptions of the circulatory system and is discussed in relation to recent work on hemolymph flow in crustaceans.

The skeletomusculature of siphonostomatoid copepods, with an analysis of adaptive radiation in structure of the oral cone

The skeletomusculature of a primitive siphonostomatoid copepod, Hyalopontius typicus , is described and compared with that of a relatively advanced siphonostomatoid, Lepeophtheirus pectoralis , an ectoparasite of flatfishes. The comparison is used to assess how adaptation to parasitism has affected the morphology and musculature of the appendages. Anatomy has been related to presumed function wherever possible, and functional interpretations are presented for the feeding apparatus of both species and for a range of other siphonostomatoids. The longitudinal trunk muscles of Hyalopontius are arranged in paired dorsal and ventral bundles, as in free-living copepods, but are smaller and less powerful. A further reduction takes place in Lepohtirus , and is presumably correlated with a limited swimming ability. The tagmosis of Hyalopontius is typically podoplean, with the prosome-urosome junction between fourth and fifth pedigerous somites. Hyalopontius possesses a cephalothorax comprising the cephalosome plus the first pedigerous somite. The tagmosis of Lepeophtheirus is modified and the prosomeurosome junction is no longer functional. In adult females the fourth pedigerous somite forms a waist-like region separating anterior cephalothorax from posterior genital complex. The shield-like cephalothorax comprises the cephalosome plus the first three pedigerous somites. The fifth pedigerous, genital and probably the first abdominal somites are fused to form a genital complex. The eudactylinid genus Bariaka is identified as one of the only two siphonostomatoids that possess a free genital somite, not incorporating the first abdominal somite. The structure and musculature of the sternal furca of Lepeophtheirus is described. It is concluded that the furca is an elaboration of the median intersomitic sclerite lying between the maxillipedal and first pedigerous somites. The musculature of the sternal furca is derived from the ventral longitudinal trunk muscles. The musculature of the cephalosomic appendages of siphonostomatoids is reduced compared with that of free-living copepods. The mandibles and maxillules increasingly lose any adduction-abduction movements. In Hyalopontius some adduction of the mandible is possible and extrinsic adductor muscles originating on the anterior cephalic tendon are retained. These are absent from Lepeophtheirus . The maxillules have no ventral extrinsic muscles in Hyalopontius and few dorsal muscles. In Lepeophtheirus there are no maxillulary muscles. The antennae, maxillae and maxillipeds are all basically subchelate and their intrinsic muscles are arranged in antagonistic extensor and flexor groups. These commonly insert on an apophysis that extends proximally from the base of the subchela. A pattern of homologies for the segmental composition of the limbs of the siphonostomatoids is established, based on evidence from their musculature. The inner lobe of the maxillule is homologous with the praecoxal arthrite of other copepods, the outer lobe with the rest of the palp. The proximal segment of the maxilla is the syncoxa. The distal claw represents the basis and its proximal endite, and there is no vestige of the endopod in any siphonostomatoid. The subchela of the maxilliped is derived from the endopod and the endopodal segments are often fused to each other and to the distal claw. The oral cone in a range of siphonostomatoid families is described. Adapdve radiation in feeding mechanisms mainly involves modification of the oral cone and maxillules, rather than of the appendages used for attachm ent to the host. In Hyalopontius , Pontoeciella and Entomopsyllus the oral cone is specialized for fluid feeding. There are efficient seals both around the distal opening of the cone and along the labrum -labium boundary. Suction pressure is produced by labral muscles concentrated in the proximal part of the cone. In Lepeophtheirus the oral cone is specialized for surface grazing and it lacks efficient sealing mechanisms distally and along the labrum -labium boundary. Food material is transported up the oral cone by sequential contraction of labral muscles. In adult Lernaeocera the oral cone acts as an enlarged oral disc forming a feeding seal distally. Suction is generated by oesophageal peristalsis. The musculature of the swimming legs of Lepeophtheirus is described. Several remotor muscles insert on the ventral body wall remote from the basal foramina of the swimming legs. These muscles probably function as a dorsoventral tensors, and assist in creating suction beneath the disc of the cephalothorax. The posterior sinuses on the rear margin of the cephalothorax function as outlet valves during swimming. They are opened and closed by sinus muscles derived from modified promotor muscles of the second swimming legs.

The cardioregulatory system of crayfish: neuroanatomy and physiology.

1. The anatomical arrangement of the cardioregulatory nerves and their physiological activity during cardiac modulation were analysed in Procambarus clarkii. 2. The bilaterally arranged pairs of cardioinhibitors and cardioaccelerator axons, in nerves SN II and SN III respectively, were physiologically identified by correlating spikes in SN II and SN III with the same spikes in the dorsal nerve, which innervates the heart. 3. The cardioinhibitor neurone fired tonically in varied sporadic bursts. During periods of cardiac inhibition, however, this neurone discharged in a long chain of spikes at a characteristic frequency of 40-50Hz. 4. The cardioaccelerator neurone fired tonically at 2-3 Hz but on occasion its activity reached 12 Hz. 5. Three inhibitory cardiac reflexes were analysed. The sensory modalities for the reflexes included (a) stretch of the dorsal pericardial wall, (b) chemical stimulation of coxal hair sensilla with glucose and (c) tactile stimulation of hair sensilla in and below the gill chamber, on the antennae, the antennules and on the anterior cephalothorax. 6. The discharge of both cardioinhibitor neurones showed a weak temporal correlation suggesting a common presynaptic drive, while the pair of cardioaccelerators appeared to have a reciprocal relationship with the cardioinhibitors.

A new genus of gammarids (Amphipoda, Gammaridae) from the intertidal zone of the Japan Sea. (In Russian; English abstract). : Tzyetkova N.L., 1965. Zool. Zhurn., Akad. Nauk. SSSR, 44 (11): 1631–1636.

The phylogenetic position of Euphausiacea within Malacostraca is still under debate. Either they are seen as sister group to a taxon comprising Pancarida and Peracarida or closer related to Decapoda. Both hypotheses can be supported by characters of the circulatory system. Therefore, a comparative re-evaluation of the circulatory system seems to be feasible.Here we present the first three-dimensional data of the circulatory system of three euphausiacean species based on semi-thin sections and micro computer tomography in combination with corrosion casting. We were also able to study for the first time representatives of Bentheuphausia amblyops, the suggested sister taxon to all other euphausiaceans.The main pumping structure in the open circulatory system of Euphausiacea is the globular heart in the rear thoracic segments. From the anterior and posterior end of the heart two unpaired and four pairs of arteries emanate. The unpaired anterior aorta runs below the carapace from the anterior part of the heart into the anterior cephalothorax, where it supplies the first antennae, the brain and the eyes. The paired posterior aortae run into the pleon supplying the pleopods, uropods and the telson. The four pairs of cardiac arteries supply appendages in the cephalic region and viscera in the trunk. The unpaired descending artery connects to the subneural vessel supplying the thoracopods. A myoarterial formation of the anterior aorta is described in Bentheuphausia amblyops.The observed pattern of a globular heart situated in the posterior cephalothorax and comprising a meshwork of musclular strands (also running through its lumen) is highly likely to be homologous in Euphausiacea and Decapoda. The data are compared with the scarce literature present to date.