Pseudunela cornuta
Encyclopedia
Pseudunela cornuta is a species
of minute sea slug
, an acochlidian, a shell-less marine
and temporary brackish gastropod mollusk in the family Pseudunelidae.
A complex interactive 3D reconstruction
(a 3D visualization based on 420 paraffin
histological
sections) of the body of an individual of this species has been available since 2009.
of the genus Pseudunela
.
According to Challis, the holotype
of Pseudunela cornuta, 20 paratype
s and a slide with the radula
of a further paratype were deposited in the Natural History Museum, London; furthermore, 10 paratypes and a slide with another radula were deposited in the Museum of New Zealand Te Papa Tongarewa
, Wellington; the remaining paratypes and the sectioned material were stored in the private collection. Neusser et al. (2009) found no evidence that it ever arrived there. Obviously, no type material of Pseudunela cornuta was ever deposited in any public institution. Thus Neusser et al. (2009) designed section series ZSM N° 20071911 of newly found specimen from the same collecting site as part of the material that was used for the original description, as neotype because of the apparent non-existence of the original type material. The sections of neotype are deposited at the Zoologische Staatssammlung München
, Mollusca Section.
. The type locality (for the neotype) is the beach of Komimbo Bay, near Tambea Village, (coordinates
: 09°15.843'S, 159°40.097'E).
s are tapered and usually point forward like horns in crawling animals. Eyes are present, but not visible externally. The densely ciliated foot is as broad as the anterior head-foot complex and extends about one third of the visceral hump in the crawling animal. The free end of the foot is pointed.
The size of the worm-like body in living specimens is about 3 mm. The body colour is whitish and translucent. In the anterior part of the visceral hump, the heart bulb is visible externally on the right side of the body. A few elongate, subepidermal spicule
s of up to 40 μm in length can be found in the posterior part of the visceral hump.
Organ complexity as seen in Pseudunela cornuta (regarding excretory and reproductive features, at least) represents innovations that evolved in small, mesopsammic marine acochlidians.
of Pseudunela cornuta is euthyneurous and composed of the paired cerebral, rhinophoral, optic, pedal, pleural, buccal and gastro-oesophageal ganglia as well as three distinct ganglia on the visceral nerve cord, plus a presumed osphradial ganglion. All ganglia excluding the buccal and gastro-oesophageal ganglia are situated pre-pharyngeally. The central nervous system is epiathroid; the pleural ganglion is located closer to the cerebral ganglion than to the pedal one. All ganglia consist of an outer cortex
containing the nuclei
and an inner medulla
. The large cerebral ganglia are linked by a robust commissure
and lie dorsal to the pedal ganglia. Anteroventrally, the robust labiotentacular nerve
emerges innervating the labial tentacle. A rhinophoral ganglion is situated anterodorsally to each cerebral ganglion connected by a short, single cerebro-rhinophoral connective. The rhinophoral nerve arises from the rhinophoral ganglion extending to the rhinophore. A small, unpigmented eye is connected by the thin optic nerve to the rhinophoral nerve, slightly anterior to the rhinophoral ganglion. An optic ganglion is attached laterally to each cerebral ganglion and connected to the latter by a thin nerve. The optic ganglion is surrounded by an additional layer of connective tissue shared with the cerebral ganglion. Precerebral anterior accessory ganglia, as described for microhedylacean acochlidians and Tantulum elegans, are absent. A Hancock's organ
could not be detected.
The paired pedal ganglia lie posteroventrally to the cerebral ganglia, and are connected by a commissure which is slightly longer than the cerebral commissure. A statocyst
with a single otolith
is attached dorsally to each pedal ganglion. The static nerve could not be detected. Two pedal nerves emerge from each pedal ganglion, one in the anterior and another in the posterior part, both innervating the foot. The pleural ganglion is located posterior to the cerebral ganglion and connected to the latter and the pedal ganglion by short connectives forming the pre-pharyngeal nerve ring. The pleural ganglia are connected by very short connectives to the visceral nerve cord, so that the latter is located at the very beginning of the pharynx
. There are three distinct ganglia on the short visceral nerve cord: the left parietal ganglion, the fused subintestinal/visceral ganglion and the fused right parietal/supraintestinal ganglion. While the left pleuro-parietal, the parietal-subintestinal/visceral and the right pleuro-parietal/supraintestinal connectives are very short, the subintestinal/visceral-parietal/supraintestinal connective is long. An additional presumed osphradial ganglion is linked to the fused parietal/supraintestinal ganglion. Anteriorly, a nerve emerges and innervates the right body wall; no histologically differentiated osphradium
could be detected. The buccal ganglia are positioned posterior to the pharynx and are linked to each other by a short buccal commissure ventral to the oesophagus. The thin cerebro-buccal connective emerges anteriorly from each buccal ganglion and was not traceable along the entire length. A smaller gastro-oesophageal ganglion lies dorsally to each buccal ganglion and is connected to the latter by a short connective.
: The mouth opening lies ventrally between the labial tentacle
s. The paired anterior pedal glands
discharge ventral to the mouth opening to the exterior. The oral tube is long and not ciliated. Paired oral tube glands are flanking the oral tube and discharge in its anterior part. The muscular pharynx
is bulbous and narrows to the posterior; it contains the hook-shaped radula
. The upper ramus is longer than the lower one. The radula formula could not be examined. Jaws are absent. The long, ciliated oesophagus emerges posterodorsally from the pharynx and is flanked by longitudinal muscles. One pair of large salivary gland
s discharges into the oesophagus via narrow salivary gland ducts directly behind the pharynx.
The large, sac-like digestive gland
is placed at the left side of the visceral hump flanking the ovotestis
and extends almost up to the end of the visceral hump. The intestine is densely ciliated and short. The anus opens slightly anterior, but separate to the nephropore and ventrolaterally on the right side of the visceral hump.
and circulatory systems
are located at the right side of the body just at the beginning of the visceral hump.
The circulatory system shows a large two-chambered heart
consisting of an anterior ventricle
and a smaller, posterior atrium. The thin-walled pericardium
surrounding the heart could not be detected because of the very compressed tissue. The aorta
arises anteriorly from the ventricle and leads to the head, where the aorta bifurcates approximately at the level of the eyes ending in blood sinuses. The renopericardioduct is a well-developed and heavily ciliated funnel. The kidney
is a sinuously bent sac and extends over almost the half of the visceral hump. Internally it is divided into a narrow lumen
bordered by tissue
with small vacuole
s, and a wide lumen limited by highly vacuolated tissue. Both lumina join in the posterior part of the kidney. The renopericardial duct is connected to the narrow lumen in the anterior part of the kidney. The connection between the kidney and the nephroduct is narrow and ciliated. The nephroduct is long and looped with a dorsal branch extending backward and a ventral branch forward. The ventral branch is looped dorsally in its distal part. The nephropore opens just posterior, but separate to the anus and ventrolaterally on the right side of the visceral hump.
of Pseudunela cornuta is simultaneous hermaphroditic. The anterior genitalia show a special androdiaulic condition: the vas deferens
does not branch off in a proximal position as usual in androdiaulic nudibranch or acteonoidean species, but more distally, i.e. autosperm must pass through the nidamental gland
s. Nevertheless this reproductive system is not strictly monaulic, because the internal vas deferens (for autosperm) is separated from the distal portion of the oviduct.
The sac-like ovotestis
extends over the half of the right side of the visceral hump and is not separated into follicle
s; oocyte
s are located more in the exterior part of the gonad and the spermatocyte
s are positioned more in the centre. Sperm heads are short. Approximately 10 yolky oocytes were noted in the examined specimen. Anterior to the ovotestis there is a small receptaculum seminis containing sperm cells oriented with their heads to the wall, as well as a sac-like ampulla filled with unoriented autosperm. Three nidamental glands can be distinguished: the albumen, membrane and mucus gland from proximal to distal, respectively. The tube-like albumen gland is characterized by cells containing dark blue stained vesicles and long cilia. The membrane gland is tube-like with long cilia as well. In the proximal part, vesicles are stained purple, in the distal part, lilac. The mucus gland is sac-like with short cilia. It shows the same histological staining properties as the distal membrane gland. The distal part of the mucus gland extends to the right side of the body wall where the hermaphroditic duct divides into the vas deferens and the oviduct. The oviduct widens to a cavity. At the distal end of the cavity a long, narrowly coiled bursa stalk branches off leading to the large bursa copulatrix. No spermatocytes can be detected inside the bursa, but an indeterminable mucous mass that might contain degenerated sperm. The distal oviduct extends to the female gonopore opening ventrolaterally on the right side of the visceral hump to the exterior. The female gonopore is situated considerably anterior to the anus and the nephropore.
The internal, subepidermal vas deferens extends along the right body side to the right rhinophore connecting to the anterior male copulatory organs. The short posterior-leading vas deferens joins the large, tubular prostate gland. Anteriorly, the long and highly coiled, muscular ejaculatory duct arises from the prostate
. The ejaculatory duct
enters the muscular penis at its base and discharges at the top of the penis through a long hollow stylet
. The penial stylet is about 600 μm long and corkscrew-like coiled with one and a half spirals. This stylet can be partly retracted into the penial muscle that is able to evert to a certain extent. The blind ending glandular paraprostate is longer and thinner than the prostate, and in contrast to the latter, highly coiled. It is connected by the paraprostatic duct to the muscular basal finger, which is united to the penial muscle mass at its base. The paraprostatic duct enters the basal finger approximately in the middle of the muscle and opens terminally via a hollow curved stylet of about 110 μm length. The penis, the basal finger and parts of the ejaculatory and paraprostatic ducts are surrounded by a thin-walled penial sheath. The latter, together with the copulatory organs, probably can be protruded through the male gonopore
just at the base of the right rhinophore during the sperm transfer. However, sperm transfer has never been observed in living specimens.
species and belongs to meiofauna of marine sands.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of minute sea slug
Slug
Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...
, an acochlidian, a shell-less marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
and temporary brackish gastropod mollusk in the family Pseudunelidae.
A complex interactive 3D reconstruction
3D reconstruction
See Iterative reconstruction for 3D reconstruction in Medical imaging.In computer vision and computer graphics, 3D reconstruction is the process of capturing the shape and appearance of real objects....
(a 3D visualization based on 420 paraffin
Paraffin
In chemistry, paraffin is a term that can be used synonymously with "alkane", indicating hydrocarbons with the general formula CnH2n+2. Paraffin wax refers to a mixture of alkanes that falls within the 20 ≤ n ≤ 40 range; they are found in the solid state at room temperature and begin to enter the...
histological
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...
sections) of the body of an individual of this species has been available since 2009.
Taxonomy
Pseudunela cornuta is the type speciesType species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
of the genus Pseudunela
Pseudunela
Pseudunela is a genus of minute sea slugs, acochlidians, shell-less marine or temporary brackish or brackish gastropod mollusks in the clade Acochlidiacea.Pseudunela is the only genus in the family Pseudunelidae...
.
According to Challis, the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
of Pseudunela cornuta, 20 paratype
Paratype
Paratype is a technical term used in the scientific naming of species and other taxa of organisms. The exact meaning of the term paratype when it is used in zoology is not the same as the meaning when it is used in botany...
s and a slide with the radula
Radula
The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
of a further paratype were deposited in the Natural History Museum, London; furthermore, 10 paratypes and a slide with another radula were deposited in the Museum of New Zealand Te Papa Tongarewa
Museum of New Zealand Te Papa Tongarewa
The Museum of New Zealand Te Papa Tongarewa is the national museum and art gallery of New Zealand, located in Wellington. It is branded and commonly known as Te Papa and Our Place; "Te Papa Tongarewa" is broadly translatable as "the place of treasures of this land".The museum's principles...
, Wellington; the remaining paratypes and the sectioned material were stored in the private collection. Neusser et al. (2009) found no evidence that it ever arrived there. Obviously, no type material of Pseudunela cornuta was ever deposited in any public institution. Thus Neusser et al. (2009) designed section series ZSM N° 20071911 of newly found specimen from the same collecting site as part of the material that was used for the original description, as neotype because of the apparent non-existence of the original type material. The sections of neotype are deposited at the Zoologische Staatssammlung München
Zoologische Staatssammlung München
Zoologische Staatssammlung München or ZSM or The Bavarian State Collection of Zoology is a major German research institution for zoological systematics. With over 20 million zoological specimens it is one of the largest natural history collections in the world. The sections are Entomology,...
, Mollusca Section.
Distribution
Pseudunela cornuta is known from the Solomon IslandsSolomon Islands
Solomon Islands is a sovereign state in Oceania, east of Papua New Guinea, consisting of nearly one thousand islands. It covers a land mass of . The capital, Honiara, is located on the island of Guadalcanal...
. The type locality (for the neotype) is the beach of Komimbo Bay, near Tambea Village, (coordinates
Geographic coordinate system
A geographic coordinate system is a coordinate system that enables every location on the Earth to be specified by a set of numbers. The coordinates are often chosen such that one of the numbers represent vertical position, and two or three of the numbers represent horizontal position...
: 09°15.843'S, 159°40.097'E).
Description
Pseudunela cornuta shows an anterior head-foot complex and a posterior elongated visceral hump in which the animal can partly retract when disturbed. The paired labial tentacles are broad at the base, tapering to the end and usually held at 45°-90° to the longitudinal axis of the specimen. The paired rhinophoreRhinophore
A rhinophore is one of a pair of club-shaped structures which are the most prominent part of the external head anatomy of a group of sea slugs, marine gastropod opisthobranch mollusks in the order Nudibranchia, the nudibranchs, specifically the dorid nudibranchs.- Etymology :The name relates to the...
s are tapered and usually point forward like horns in crawling animals. Eyes are present, but not visible externally. The densely ciliated foot is as broad as the anterior head-foot complex and extends about one third of the visceral hump in the crawling animal. The free end of the foot is pointed.
The size of the worm-like body in living specimens is about 3 mm. The body colour is whitish and translucent. In the anterior part of the visceral hump, the heart bulb is visible externally on the right side of the body. A few elongate, subepidermal spicule
Spicule
Spicules are tiny spike-like structures of diverse origin and function found in many organisms, such as the copulatory spicules of certain nematodes or the grains on the skin of some frogs.In sponges, spicules perform a structural function....
s of up to 40 μm in length can be found in the posterior part of the visceral hump.
Organ complexity as seen in Pseudunela cornuta (regarding excretory and reproductive features, at least) represents innovations that evolved in small, mesopsammic marine acochlidians.
Central nervous system
The central nervous systemNervous system of gastropods
The nervous system of gastropods consists of a series of paired ganglia connected by major nerve cords, and a number of smaller branching peripheral nerves.The brain of a gastropod consists of three pairs of ganglia, all located close to the oesophagus...
of Pseudunela cornuta is euthyneurous and composed of the paired cerebral, rhinophoral, optic, pedal, pleural, buccal and gastro-oesophageal ganglia as well as three distinct ganglia on the visceral nerve cord, plus a presumed osphradial ganglion. All ganglia excluding the buccal and gastro-oesophageal ganglia are situated pre-pharyngeally. The central nervous system is epiathroid; the pleural ganglion is located closer to the cerebral ganglion than to the pedal one. All ganglia consist of an outer cortex
Cortex (anatomy)
In anatomy and zoology the cortex is the outermost layer of an organ. Organs with well-defined cortical layers include kidneys, adrenal glands, ovaries, the thymus, and portions of the brain, including the cerebral cortex, the most well-known of all cortices.The cerebellar cortex is the thin gray...
containing the nuclei
Nucleus (neuroanatomy)
In neuroanatomy, a nucleus is a brain structure consisting of a relatively compact cluster of neurons. It is one of the two most common forms of nerve cell organization, the other being layered structures such as the cerebral cortex or cerebellar cortex. In anatomical sections, a nucleus shows up...
and an inner medulla
Medulla
Medulla refers to the middle of something and derives from the Latin word for marrow. Its anatomical uses include:* Medulla oblongata, a part of the brain stem* Renal medulla, a part of the kidney* Adrenal medulla, a part of the adrenal gland...
. The large cerebral ganglia are linked by a robust commissure
Commissure
A commissure is the place where two things are joined. The term is used especially in the fields of anatomy and biology.In anatomy, commissure refers to a bundle of nerve fibers that cross the midline at their level of origin or entry .* The most common usage of the term refers to the brain's...
and lie dorsal to the pedal ganglia. Anteroventrally, the robust labiotentacular nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
emerges innervating the labial tentacle. A rhinophoral ganglion is situated anterodorsally to each cerebral ganglion connected by a short, single cerebro-rhinophoral connective. The rhinophoral nerve arises from the rhinophoral ganglion extending to the rhinophore. A small, unpigmented eye is connected by the thin optic nerve to the rhinophoral nerve, slightly anterior to the rhinophoral ganglion. An optic ganglion is attached laterally to each cerebral ganglion and connected to the latter by a thin nerve. The optic ganglion is surrounded by an additional layer of connective tissue shared with the cerebral ganglion. Precerebral anterior accessory ganglia, as described for microhedylacean acochlidians and Tantulum elegans, are absent. A Hancock's organ
Hancock's organ
Hancock's organ is a lateral sensory organ of gastropods, a sense organ found in some sea snails. This organ is found in most shelled opisthobranchs....
could not be detected.
The paired pedal ganglia lie posteroventrally to the cerebral ganglia, and are connected by a commissure which is slightly longer than the cerebral commissure. A statocyst
Statocyst
The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, echinoderms, cephalopods, and crustaceans. A similar structure is also found in Xenoturbella. The statocyst consists of a sac-like structure containing a mineralised mass and numerous...
with a single otolith
Otolith
An otolith, , also called statoconium or otoconium is a structure in the saccule or utricle of the inner ear, specifically in the vestibular labyrinth of vertebrates. The saccule and utricle, in turn, together make the otolith organs. They are sensitive to gravity and linear acceleration...
is attached dorsally to each pedal ganglion. The static nerve could not be detected. Two pedal nerves emerge from each pedal ganglion, one in the anterior and another in the posterior part, both innervating the foot. The pleural ganglion is located posterior to the cerebral ganglion and connected to the latter and the pedal ganglion by short connectives forming the pre-pharyngeal nerve ring. The pleural ganglia are connected by very short connectives to the visceral nerve cord, so that the latter is located at the very beginning of the pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
. There are three distinct ganglia on the short visceral nerve cord: the left parietal ganglion, the fused subintestinal/visceral ganglion and the fused right parietal/supraintestinal ganglion. While the left pleuro-parietal, the parietal-subintestinal/visceral and the right pleuro-parietal/supraintestinal connectives are very short, the subintestinal/visceral-parietal/supraintestinal connective is long. An additional presumed osphradial ganglion is linked to the fused parietal/supraintestinal ganglion. Anteriorly, a nerve emerges and innervates the right body wall; no histologically differentiated osphradium
Osphradium
The osphradium is the olfactory organ in certain molluscs, linked with the respiration organ.The main function of this is to test incoming water for silt and other possible food particles.It is used by all members of the Genus Conus....
could be detected. The buccal ganglia are positioned posterior to the pharynx and are linked to each other by a short buccal commissure ventral to the oesophagus. The thin cerebro-buccal connective emerges anteriorly from each buccal ganglion and was not traceable along the entire length. A smaller gastro-oesophageal ganglion lies dorsally to each buccal ganglion and is connected to the latter by a short connective.
Digestive system
Digestive systemDigestive system of gastropods
The digestive system of gastropods has evolved to suit almost every kind of diet and feeding behavior. Gastropods as the largest taxonomic class of the mollusca are very diverse indeed: the group includes carnivores, herbivores, scavengers, filter feeders, and even parasites.In particular, the...
: The mouth opening lies ventrally between the labial tentacle
Tentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...
s. The paired anterior pedal glands
Suprapedal gland
The suprapedal gland or mucous pedal gland is an anatomical feature found in some snails and slugs. It is a gland located inside the front end of the foot of gastropods.The term suprapedal means "above the foot"....
discharge ventral to the mouth opening to the exterior. The oral tube is long and not ciliated. Paired oral tube glands are flanking the oral tube and discharge in its anterior part. The muscular pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
is bulbous and narrows to the posterior; it contains the hook-shaped radula
Radula
The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
. The upper ramus is longer than the lower one. The radula formula could not be examined. Jaws are absent. The long, ciliated oesophagus emerges posterodorsally from the pharynx and is flanked by longitudinal muscles. One pair of large salivary gland
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...
s discharges into the oesophagus via narrow salivary gland ducts directly behind the pharynx.
The large, sac-like digestive gland
Hepatopancreas
The hepatopancreas, digestive gland or midgut gland is an organ of the digestive tract of arthropods, molluscs and fish. It provides the functions which in mammals are provided separately by the liver and pancreas, including the production of digestive enzymes, and absorption of digested...
is placed at the left side of the visceral hump flanking the ovotestis
Ovotestis
An ovotestis is a gonad with both testicular and ovarian aspects. In humans, ovotestes are an anatomical abnormality associated with gonadal dysgenesis.- In gastropods :...
and extends almost up to the end of the visceral hump. The intestine is densely ciliated and short. The anus opens slightly anterior, but separate to the nephropore and ventrolaterally on the right side of the visceral hump.
Excretory and circulatory systems
The excretoryExcretory system of gastropods
The excretory system of gastropods removes nitrogenous waste and maintains the internal water balance of these creatures, commonly referred to as snails and slugs...
and circulatory systems
Circulatory system of gastropods
As in other molluscs, the circulatory system of gastropods is open, with the fluid, or haemolymph, flowing through sinuses and bathing the tissues directly. The haemolymph typically contains haemocyanin, and is blue in colour.-Circulation:...
are located at the right side of the body just at the beginning of the visceral hump.
The circulatory system shows a large two-chambered heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
consisting of an anterior ventricle
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...
and a smaller, posterior atrium. The thin-walled pericardium
Pericardium
The pericardium is a double-walled sac that contains the heart and the roots of the great vessels.-Layers:...
surrounding the heart could not be detected because of the very compressed tissue. The aorta
Aorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...
arises anteriorly from the ventricle and leads to the head, where the aorta bifurcates approximately at the level of the eyes ending in blood sinuses. The renopericardioduct is a well-developed and heavily ciliated funnel. The kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
is a sinuously bent sac and extends over almost the half of the visceral hump. Internally it is divided into a narrow lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
bordered by tissue
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
with small vacuole
Vacuole
A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain...
s, and a wide lumen limited by highly vacuolated tissue. Both lumina join in the posterior part of the kidney. The renopericardial duct is connected to the narrow lumen in the anterior part of the kidney. The connection between the kidney and the nephroduct is narrow and ciliated. The nephroduct is long and looped with a dorsal branch extending backward and a ventral branch forward. The ventral branch is looped dorsally in its distal part. The nephropore opens just posterior, but separate to the anus and ventrolaterally on the right side of the visceral hump.
Reproductive system
The reproductive systemReproductive system of gastropods
The reproductive system of gastropods varies greatly from one group to another within this very large and diverse taxonomic class of animals...
of Pseudunela cornuta is simultaneous hermaphroditic. The anterior genitalia show a special androdiaulic condition: the vas deferens
Vas deferens
The vas deferens , also called ductus deferens, , is part of the male anatomy of many vertebrates; they transport sperm from the epididymis in anticipation of ejaculation....
does not branch off in a proximal position as usual in androdiaulic nudibranch or acteonoidean species, but more distally, i.e. autosperm must pass through the nidamental gland
Nidamental gland
The nidamental gland is an internal organ found in some elasmobranchs and certain molluscs, including cephalopods and gastropods....
s. Nevertheless this reproductive system is not strictly monaulic, because the internal vas deferens (for autosperm) is separated from the distal portion of the oviduct.
The sac-like ovotestis
Ovotestis
An ovotestis is a gonad with both testicular and ovarian aspects. In humans, ovotestes are an anatomical abnormality associated with gonadal dysgenesis.- In gastropods :...
extends over the half of the right side of the visceral hump and is not separated into follicle
Follicle
Follicle may refer to:*Follicle , a small spherical group of cells containing a cavity:** Dental follicle** Hair follicle** Lymph follicle** Ovarian follicle** Thyroid follicle*Follicle...
s; oocyte
Oocyte
An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...
s are located more in the exterior part of the gonad and the spermatocyte
Spermatocyte
A spermatocyte is a male gametocyte, derived from a spermatogonium, which is in the developmental stage of spermatogenesis during which meiosis occurs. It is located in the seminiferous tubules of the testis.-Spermatogenesis:...
s are positioned more in the centre. Sperm heads are short. Approximately 10 yolky oocytes were noted in the examined specimen. Anterior to the ovotestis there is a small receptaculum seminis containing sperm cells oriented with their heads to the wall, as well as a sac-like ampulla filled with unoriented autosperm. Three nidamental glands can be distinguished: the albumen, membrane and mucus gland from proximal to distal, respectively. The tube-like albumen gland is characterized by cells containing dark blue stained vesicles and long cilia. The membrane gland is tube-like with long cilia as well. In the proximal part, vesicles are stained purple, in the distal part, lilac. The mucus gland is sac-like with short cilia. It shows the same histological staining properties as the distal membrane gland. The distal part of the mucus gland extends to the right side of the body wall where the hermaphroditic duct divides into the vas deferens and the oviduct. The oviduct widens to a cavity. At the distal end of the cavity a long, narrowly coiled bursa stalk branches off leading to the large bursa copulatrix. No spermatocytes can be detected inside the bursa, but an indeterminable mucous mass that might contain degenerated sperm. The distal oviduct extends to the female gonopore opening ventrolaterally on the right side of the visceral hump to the exterior. The female gonopore is situated considerably anterior to the anus and the nephropore.
The internal, subepidermal vas deferens extends along the right body side to the right rhinophore connecting to the anterior male copulatory organs. The short posterior-leading vas deferens joins the large, tubular prostate gland. Anteriorly, the long and highly coiled, muscular ejaculatory duct arises from the prostate
Prostate
The prostate is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals....
. The ejaculatory duct
Ejaculatory duct
-Anatomy:The ejaculatory ducts are paired structures in male anatomy. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the urethra at the Colliculus seminalis...
enters the muscular penis at its base and discharges at the top of the penis through a long hollow stylet
Stylet
A stylet is a hard, sharp, anatomical structure found in some invertebrates.For example, the word stylet or stomatostyle, is used for the primitive piercing mouthparts of some nematodes and some nemerteans...
. The penial stylet is about 600 μm long and corkscrew-like coiled with one and a half spirals. This stylet can be partly retracted into the penial muscle that is able to evert to a certain extent. The blind ending glandular paraprostate is longer and thinner than the prostate, and in contrast to the latter, highly coiled. It is connected by the paraprostatic duct to the muscular basal finger, which is united to the penial muscle mass at its base. The paraprostatic duct enters the basal finger approximately in the middle of the muscle and opens terminally via a hollow curved stylet of about 110 μm length. The penis, the basal finger and parts of the ejaculatory and paraprostatic ducts are surrounded by a thin-walled penial sheath. The latter, together with the copulatory organs, probably can be protruded through the male gonopore
Gonopore
A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects have a single common gonopore, except mayflies, which have a pair of gonopores...
just at the base of the right rhinophore during the sperm transfer. However, sperm transfer has never been observed in living specimens.
Ecology
Pseudunela cornuta is mesopsammic, marine interstitialInterstitial
An interstitial space or interstice is an empty space or gap between spaces full of structure or matter.In particular, interstitial may refer to:-Physical sciences:...
species and belongs to meiofauna of marine sands.