The structure and function of the genitalia in the Libellulidae (Odonata)

An outline of the morphology of the secondary genitalia of libellulid dragonflies is given together with a more detailed treatment of the components of the fourth (distal) segment of the penis. The variations of penis structure in 70 species, representing ten of the 11 subfamilies, are surveyed and catalogued. There is remarkable diversity in the presence and form of penis structures, particularly those associated with the medial process, namely the flagelium, cornua and inner lobes. A comparable survey of females shows that they can be provisionally divided into ten types according to the number and size of their sperm-storage organs. Comparisons of penis structures with the sperm-storage organs of females suggests that in species whose females store large amounts of sperm, usually doing so in one or a pair of organs, males possess highly extensible, lobate and bristly penes, commonly equipped with cornua. By contrast, in those species in which the females store small volumes of sperm, usually doing so in three organs, the penes bear either flagella equipped with proximally directed spines or with large terminal barbs, or they have narrow, spiny inner-lobes which resemble flagella. Some functional interpretations are proposed in the light of sperm competition. The variability of genital structure can be interpreted adaptively and does not closely reflect phylogenetic relationships. Functionally convergent structures have evolved a number of times from different origins.     

The copulatory complex of Hemianax ephippiger (Burmeister) (Aeshnidae: Anisoptera)

Like other Anisoptera Hemianax ephippiger (Burmeister) bears two sets of copulatory apparatuses. The first set which is primary in nature is located on the ventral surface of the ninth abdominal segment and consists of the vestigial penis, the gonocoxites, the supra-anal appendages, the infra-anal appendage. The supra-anal appendages are well developed, lanceolate with serrate margin and spinous apices. They are dorso-ventrally flattened and furnished with long hairs and black teeth-like tubercles (T). The secondary copulatory complex is lodged inside the membranous fossa located on the ventral surface of second and third abdominal segments. It consists of anterior lamina, the posterior lamina, the supporting framework, the hamules, the penis sheath, the penis vesicle and the penis. The anterior lamina is deeply cleft at the posterior margin to accommodate the ovipositor of the female during copulation. Both the portions of the supporting framework are well developed. The anterior portion is somewhat rectangular while the posterior portion is nearly U-shaped. The anterior hamules are well developed with truncated and hooked portions, while the posterior hamules are very much reduced. The penis sheath is forcepate with well developed rectangular flap which hangs over the penis. The penis is stout, clearly demarcated into three segments, and bears a prominent groove on the mid-ventral line.     

Brain anatomy of the marine tardigrade actinarctus doryphorus (arthrotardigrada)

Knowledge of tardigrade brain structure is important for resolving the phylogenetic relationships of Tardigrada. Here, we present new insight into the morphology of the brain in a marine arthrotardigrade, Actinarctus doryphorus, based on transmission electron microscopy, supported by scanning electron microscopy, conventional light microscopy as well as confocal laser scanning microscopy. Arthrotardigrades contain a large number of plesiomorphic characters and likely represent ancestral tardigrades. They often have segmented body outlines and each trunk segment, with its paired set of legs, may have up to five sensory appendages. Noticeably, the head carries numerous cephalic appendages that are structurally equivalent to the sensory appendages of the trunk segments. Our data reveal that the brain of A. doryphorus is partitioned into three paired lobes, and that these lobes exhibit a more pronounced separation as compared to that of eutardigrades. The first brain lobe in A. doryphorus is located anteriodorsally, with the second lobe just below it in an anterioventral position. Both of these two paired lobes are located anterior to the buccal tube. The third pair of brain lobes are situated posterioventrally to the first two lobes, and flank the buccal tube. In addition, A. doryphorus possesses a subpharyngeal ganglion, which is connected with the first of the four ventral trunk ganglia. The first and second brain lobes in A. doryphorus innervate the clavae and cirri of the head. The innervations of these structures indicate a homology between, respectively, the clavae and cirri of A. doryphorus and the temporalia and papilla cephalica of eutardigrades. The third brain lobes innervate the buccal lamella and the stylets as described for eutardigrades. Collectively, these findings suggest that the head region of extant tardigrades is the result of cephalization of multiple segments. Our results on the brain anatomy of Actinarctus doryphorus support the monophyly of Panarthropoda. J. Morphol. 275:173–190, 2014. © 2013 Wiley Periodicals, Inc.     

The myth of intercalary segment in insect head

Embryonic development of the head of Oxyrhachis tarandus (Membracidae) has been investigated in detail to settle the controversy of head segmentation and to refute the occurrence of an intercalary segment. The head is formed from six distinct elements: the prostominal lobe, the paired cephalic lobes, the antennal segment and the three noncontroversial gnathal segments. The prostomial lobe, which possesses a neuromere and a pair of coelomic cavities, represents the first body segment, called the prostomial segment. The tritocerebral lobes of the brain and the stomatogastric nervous system, consisting of a frontal ganglion, clypeolabral nerves, and the recurrent nerve etc., develop from the neuromere of the prostomial lobe. The tritocerebrum thus belongs to the prostomial segment rather than to an imaginary intercalary segment and mainly represents the ganglionic center of the stomatogastric nervous system in the brain. Frons, clypeus, and labrum develop from the outer wall of the prostomial lobulate plate, whereas the epipharyngeal wall, including the cibarial pump, develops from its inner wall. The presence of three coelomic cavities and of three distinct neural masses in the cephalic lobes during the initial stages of development shows that they have developed by the fusion of three distinct segments during the long phylogenetic history of insects. The portion of the germ band presently considered as the intercalary segment is actually the sternal part of the antennal segment. The neural cells located in this region give rise to the deutocerebrum by shifting forward, around the stomodaeum, and always leaving a commissure behind. The intercalary segment is thus a complete illusion. The antennal segment is postoral in the beginning and bears a pair of coelomic cavities, but later on it shifts forward and its sternal part invaginates into the stomodaeum.     

The male germ unit of Rhododendron: quantitative cytology,three-dimensional reconstruction,isolation and detection using fluorescent probes

Summary The sperm cells of Rhododendron laetum and R. macgregoriae differentiate within the pollen tube about 24 h after germination in vitro. Threedimensional reconstruction shows that the sperm cells are paired together, and both have extensions that link with the tube nucleus, forming a male germ unit. Quantitative analysis shows that the sperm cells in each pair differ significantly in surface area, but not in cell volume nor in numbers of mitochondria or plastids. When isolated from pollen tubes by osmotic shock, the sperm cells became ellipsoidal and surrounded by their own plasma membrane, while a proportion remained in pairs linked by the inner tube plasma membrane. Both generative and sperm cells are visualized in pollen tube preparations by immunofluorescence with anti-tubulin and anti-actin monoclonal antibodies (MAbs) combined with H33258 fluorescence of the nuclei. Video-image processing shows the presence of an axial microtubule cage in the generative cells, and some microtubules are present in the cytoplasmic extensions that clasp the tube nucleus. Following sperm cell division, the extensive phragmoplast between the sperm nuclei is partitioned by the plasma membranes.     

First record of the mite genus Neharpyrhyncuhus (Acari: Harpirhynchidae) in the Russian fauna

The mites of genus Neharpyrhynchus Fain, 1972 (Acari: Harpirhynchidae) are recorded from Rissia for first time. Two species, N. hippolae sp. n. from Hippolais icterina (Passeriformes: Sylviidae) and N. plumaris (Fritsch) from Fringilla coelebs (Passeroformes: Fringillidae) from N. W. Russia was found. N. hippolae sp. n., female holotype (all measurements in mkm, abbreviations--see Fain e.a., 1999): L 517, W 382, LS 179, WS 325, PA 27, thicker than PI 49 and PE 24, pts smooth, vi, ve [symbol: see text] sci are subequal, about 94, l5 247; propodosomal shield not divided; anterior region of pronotum with rounded verrucosites; venter without scales; legs I-II with 2 free segments and strongly developed lobes at their bases; legs III-IV with one segment, bears 4 and 5 setae respectively (in paratypes number of these setae is variable, 4-5). Male: L 227-254, W 210-219, LS 129-134, WS 170-183, pts are smooth, ve 78-87, sci 83-90, sce 89-95, h 90-110; penis 49-56 long; legs III with 2 free segments, basal segment bears seta, apical segment with 5-6 setae; legs IV with one free segment, it bears 4-5 setae. The new species is closely related to N. pilirostris (Berlese et Trouessart, 1889) and distinguished by characters as follows. N. hippolae sp. n. (female): the setae PI about 2 times are longer than PA and PE; the apical segment of legs III-IV bears 4-5 setae. N. pilirostris: setae PA, PI [symbol: see text] PE are subequal; the apical segment of legs III-IV bears 4 setae only. N. plumaris differs from closely related species N. novoplumaris Moss e.a., 1968 by characters as follows. In female of N. plumaris, the setae PA are subequal to PE and 1.6-1.8 times shorter than PI. In N. novoplumaris, the setae PA shorter than PI and PE.     

The male copulatory system of european pea crabs (crustacea,brachyura, pinnotheridae)

The male copulatory system of the European pinnotherid species Pinnotheres pisum, Pinnotheres pectunculi, and Nepinnotheres pinnotheres was investigated by gross morphology, scanning electron microscopy, histological methods, and confocal laser scanning microscopy. The brachyuran copulatory system is consistently formed by paired penes and two pairs of abdominal appendages, the gonopods, functioning in sperm transfer. In pinnotherids, the long first gonopods transfer the sperm mass into the female ducts. The first gonopod has the ejaculatory canal inside that opens both basally and distally. The second gonopod is solid, short, and conical. During copulation, the penis and the second gonopod are inserted into the basal lumen of the first gonopod. While the penis injects the sperm mass, the second gonopod functions in the transport of spermatozoa inside the ejaculatory canal toward its distal opening. The second gonopod is adapted for the sealing of the tubular system in the first gonopod by its specific shape and the ability to swell. Longitudinal cuticle foldings of the second gonopod hook into structures inside the first gonopod. The second gonopod can interact with the penis during copulation by a flexible flap separating the lumina in which the second gonopod and the penis are inserted. J. Morphol., 2012. © 2012 Wiley Periodicals, Inc.     

Fine structure of the male reproductive system in two species ofHaplognathia sterrer (Gnathostomulida,Filospermoidea)

Summary The structure of the male reproductive systems of two species ofHaplognathia cf.lyra andH. cf.rosacea was described. The structure of the testes and the anterior portions of the sperm ducts in both species was found to be similar. However, considerable species differences were found between the structures of the glands and muscles associated with the reproductive systems. These were more elaborate inH. cf.lyra than inH. cf.rosacea. The former species possessed an H-shaped sperm duct gland, three distinct groups of penis muscles and a penis with two cell types and with a lumen. The latter species had paired sperm duct glands, no specialized penis muscles and a penis with only one cell type and without a detectable lumen. No open gonopore was observed in either species. The sperm presumably exit through a ventral tissue connection observed connecting the penis and the ventral epidermis. These findings were discussed in the light of Mainitz's (1977) theory concerning the primitive penis type within the Gnathostomulida.Abbreviations ap anterior-posterior penis muscles - bm basement membrane - csd common sperm duct - dl dorsal lumen of the penis - dp dorsal gland cells of the penis - dv dorsoventral muscles anterior to the penis - dw sperm duct wall cell - e epidermis - ex exit cell - g intestine - gl gut lumen - n nerve - p penis - sd sperm duct - sdg sperm duct gland - tw testes wall cell - vl ventral lumen of the penis - vp ventral gland cells of the penis This project was supported by NSF grant #GB 42211 (R.M. Rieger P.I.). The line drawings have been executed after our design by Ms. Linda McVay     

Spermatophore expulsion in the carrion beetle Silpha perforata (Coleoptera: Silphidae)

Silphinae (Coleoptera: Silphidae) is an abundant decomposer that plays important roles in the ecosystem. However, there is little information about the life history of this taxon. We found sperm displacement behavior in carrion beetle Silpha perforata. Copulating males bit the female's antenna strongly and inserted the penis into the partner's genital organ more than once. We found a white substance on the tip of penis during copulation. We examined whether this white substance is a previous male's spermatophore, which was removed from the mating partner. When females were dissected just after mating, the same substance that often presents on the penis of mating males was found in the bursa copulatrix of females, although the bursa copulatrix of virgin females was empty. Male behavior during copulation with females of different mating history was also observed to confirm that the removal of spermatophores was observed only in copulation with females that have the spermatophores of previous males. Consequently, we estimated that S. perforata males removed spermatophores of previous males from mating partners. In addition, we dissected the males frozen during copulation, and inspected the penis morphology. This observation revealed that the apical part of the penis was usually hidden in the basal part of penis, but expanded and appeared during insertion. This apical part had many spines, which play an important role in sperm displacement and sexual conflict in some species. These results indicate that there is the sperm competition in S. perforata. This is the first report on sperm competition in Silphinae.     

Spernathecal morphology,sperm transfer and a novel mechanism of sperm displacement in the rove beetle,Aleochara curtula (Coleoptera,Staphylinidae)

Summary The mechanism by which sperm are transferred from the male's spermatophore to the female's storing cage is described for the rove beetle Aleochara curtula, emphasizing a novel mechanism of sperm displacement by competing males. The cuticular, U-shaped spermatheca is equipped with a valve structure and two sclerotized teeth. The tube of the spermatophore extends into the spermathecal duct through the guidance of the flagellum of the male endophallus. Further elongation of the spermatophore tube, however, occurs only after separation of the pair. A primary tube bursts at its tip after passing through the valve. Within the lumen of the primary tube, a second tube passes through the valve and continues to extend up to the apical bulb of the spermatheca, doubles back on itself and swells to form a balloon filling most of the spermatheca. The balloon of the spermatophore is pierced within the spermatheca by tooth-like structures pressed against the spermatophore through contraction of the spermathecal muscle. The same process of spermatophore growing and swelling is also observed in mated females. Sperm from previous copulations are backflushed through the valve and the spermathecal duct, indicative of last-male sperm predominance.Abbreviations ad adhesive secretion covering the sperm - sac am amorphous secretion of the spermatophore - as ascending portion of the spermatophore - ds descending portion of the spermatophore - end parts of the male endophallus - ext extended tube - f flagellum - gs genital segment - lt large tooth - m muscle of the spermatheca - nsc non sclerotized cuticle - op opening of the spermathecal gland - pt primary tube - sc sclerotized cuticle - sd spermathecal duct - se secretion of the spermathecal gland - sf secretion flowing out of the primary tube - sg spermathecal gland - sm sperm - smt small tooth - sp spermatheca - ss sperm sac - st secondary tube - vm vaginal muscle     

Mating and the inferred function of the genital system of the nudibranch, Aeolidiella glauca (Gastropoda: Opisthobranchia: Aeolidioidea)

Abstract. We describe the genital system of the aeolid nudibranch gastropod Aeolidiella glauca as a basis for our ongoing analysis of the mating system of this hermaphroditic species. In addition we give a short account of its mating behavior. A. glauca has an androdiaulic genital system with a proximally situated semiserial seminal receptacle. There is no bursa copulatrix. After fertilization, eggs pass through six glands, i.e., the capsule gland and the female gland mass which is comprised of five histologically differentiated parts. The prostate is a long, glandular tube. The everted, unarmed penis is very large and bears a series of 3–4 hook-shaped lobes consisting only of a simple, ciliated epithelium on its ventral side. Their function is unknown. After courtship, which involves moving in circles followed by resting in a head-to-head position, reciprocally touching each other with the tentacles, the slugs glide into a position where the everted genital atria are in contact. The huge penes are protruded simultaneously shortly after this contact occurs. Each animal strokes its partner's back with the penis and deposits a spermatophore of undetermined shape onto the partner's notum. Sperm enter the recipient through histolysis. How the sperm find their way to the seminal receptacle is not known.     

三种蚤生殖系统的细微结构:雄性外生殖器的发育

本文研究了缓慢细蚤Leptopsylla segnis(Schonherr),不等单蚤Monopsyllus anisus(Rothschild)和猫栉首蚤指名亚种Ctenocephalides felis felis(Bouche)雄性外生殖器的结构,观察了从幼虫、前蛹、蛹至成虫各发育时期的雄性外生殖器的内部结构变化.对有争议的雄蚤上抱器的起源,雄蚤生殖孔的位置,雄性外生殖器芽内陷的腹节以及射精管横切面的细胞数目和阳茎背、腹杆的结构等问题进行了详细的观察和探讨.     

Larval morphology and development of Coptera occidentalis

The morphology and development of immature stages of the solitary internal parasitoid Coptera occidentalis were studied within the pupae of their factitious host, Ceratitis capitata. Parasitoid eggs are of the hymenopteriform type. Three larval instars are described. The first instar is of the mandibulate type bearing prominent submandibular appendages and a pair of terminal lobes on the last abdominal segment. The terminal lobes are covered with cuticular spines. The integument also bears cuticular spines arranged in paired dorsal welts on each of body segments V--IX. The second and third instar larvae are hymenopteriform with simple mandibles, reduced submandibular appendages and smooth integument. The third instar has an open tracheal system with three pairs of spiracles on segments II--IV. Considerable variation in development rates of parasitoid immature stages and high percentage of superparasitism were observed. Parasitoid eggs nearly doubled in size during the 96-h incubation. Development from egg to pupa took minimum 25 days and emergence of imagines started on day 42 after parasitization. Superparasitism was recorded in 56% of the examined hosts. The average number of eggs/host was 5.04 (range 1--22). Supernumerary occurrence of successive larval instars per one host was also observed.     

The effect of size,age, and recent egg laying on copulatory choice of the hermaphroditic mollusc Aplysia juliana

Summary

Aplysia juliana is a cross-fertilizing, simultaneous hermaphrodite. During copulation, an individual may act as either a sperm donor or a sperm recipient, or both, when a pair copulates reciprocally. Experiments were conducted with A. juliana to determine if an animal's size, age, or recent egg-laying activity influenced its choice of copulatory role. Animals were isolated except when paired during daily, half-hour trials. In the first experiment, mature animals of different size (weight) but similar age were randomly paired. Animal size had no effect on the initial copulatory role chosen. In the second experiment, young, maturing A. juliana were paired with older animals. Young animals showed no preference in initial copulatory role either as a group or individually. Older A. juliana showed no copulatory preference as a group, but over half of the individuals demonstrated a consistent choice of one role. Some individuals acted almost exclusively as sperm donors, others as sperm recipients, suggesting that as an A. juliana ages, it is likely to develop a preference for a single copulatory role. A record of daily egg mass production was kept for all animals in the second experiment. Production of an egg mass since the last copulation did not affect the copulatory role chosen in the subsequent copulation.     

The seminal vesicle of the African catfish,Clarias gariepinus

Summary The seminal vesicle of the African catfish, Clarias gariepinus, consists of 36–44 fingerlike lobes built up of tubules in which a fluid is secreted containing acid polysaccharides, acid-, neutral- and basic proteins, and phospholipids. In this fluid sperm cells are stored. The seminal vesicle fluid immobilizes the sperm cells. After ejaculation, it prolongs the period of sperm activity. The seminal vesicle fluid is secreted by the epithelium lining the tubules. The tubules in the proximal part of the lobes are predominantly lined by a simple cylindrical and those of the distal part by a simple squamous epithelium. These epithelial cells contain enzymes involved in energy-liberating processes, the enzyme activites being proportional to the height of the cells. Interstitial cells between the tubules have enzyme-histochemical and ultrastructural features indicative of steroid biosynthesis. Similar characteristics are found in testicular interstitial cells. The most rostral seminal vesicle lobes and the most caudal testicular efferent tubules form a network of tubules that opens at the point where the paired parts of the sperm ducts fuse with each other. The tubules of most seminal vesicle lobes, however, form a complex system that fuses with the unpaired part of the sperm duct.     

Fitness advantages of the biased use of paired laterally symmetrical penises in an insect

The evolution of laterality, that is the biased use of laterally paired, morphologically symmetrical organs, has attracted the interest of researchers from a variety of disciplines. It is, however, difficult to quantify the fitness benefits of laterality because many organs, such as human hands, possess multimodal functions. Males of the earwig Labidura riparia (Insecta: Dermaptera: Labiduridae) have morphologically similar laterally paired penises, only one of which is used for inseminating the female during a single copulation bout, and thus provide a rare opportunity to address how selection pressure may shape the evolution of population‐level laterality. Our population studies revealed that in 10 populations, located at 2.23–43.3° north, the right penis is predominantly used for copulating (88.6%). A damaged penis was found in 23% of rare left‐handers, suggesting that the left penis can function as a spare when the right one is damaged. By pairing L. riparia females with surgically manipulated males, we found that males forced to use the right penis outperformed left‐handed males in copulation (the probability of establishing genital coupling during the 1‐hr observation period: odds ratio [OR] of 3.50) and insemination (probability of transferring a detectable amount of sperm: OR of 2.94). This right‐handed advantage may be due to the coiled morphology of the sperm storage organ with a right‐facing opening. Thus, female genital morphology may play a significant role in the evolution of handedness and may have acted as a driving force to reduce penis number in related taxa.     

Ultrastructure of the Male Accessory Glands and Sperm Ducts of Cylindrotaenia hickmani(Cestoda,Cyclophyllidea)

Abstract The ultrastructure of unicellular accessory glands (= prostate glands) and external male ducts of the cestode Cylindrotaenia hickmaniare described. Accessory glands open into the lumen of the external common sperm duct (= external vas deferens). The gland cells contain abundant endoplasmic reticulum, Golgi bodies and secretory bodies, and have elongate necks that pierce the apical cytoplasm of the duct. Cell contact with the apical cytoplasm of the sperm duct is mediated by septate desmosomes. Accessory glands secrete spherical particles, with a diameter of approximately 70 nm, that adhere to spermatozoa. The roles of these accessory glands may relate to activity of the sperm or development of the female system after insemination. Paired sperm ducts arise from testes, and unite to form a common sperm duct. Each duct consists of a tubular anucleate cytoplasmic region which is supported by nucleated cytons that lie sunken in the parenchyma. The apical cytoplasm of the paired sperm ducts (= vasa efferentia) possesses apical microvilli and abundant mitochondria, but few other cytoplasmic features. The apical cytoplasm of the common sperm duct possesses sparse apical microvilli and numerous electronlucent vesicles. The male gonoducts form an elongate syncytium which is markedly polarized along the length of the ducts. The ducts also display apical–basal polarity in that sunken nucleated cytons support the apical cytoplasm which in turn has distinct basal and apical domains.     

Morphological aspects of Culex quinquefasciatus salivary glands

The salivary glands of Culex quinquefasciatus female mosquitoes are paired organs composed of two lateral lobes with proximal and distal secretory portions, and a medial lobe. All portions comprise a simple epithelium that surrounds a salivary duct. In the apical portion of the medial lobe, non-secretory cells strongly resemble cells involved in ion and water transport. The general architecture of the secretory portions is similar between lobes. The appearance of the secretory material and the morphological aspect of the apical cell membrane are the most distinctive features among the three secretory portions. Cells in the lateral proximal lobe display thin membrane projections extending into a translucent and finely filamentous secretory product. At the lateral distal portion, the apical cell membrane forms an intricate meshwork that encloses a dark secretory product. Medial lobe secretory cells also contain secretory cavities surrounded by intracytoplasmic vesicles, all containing a very dark and uniform product. Scattered cells holding numerous vacuoles, some of them containing a small and electron-dense granule eccentrically located and resembling those of the diffuse endocrine system, are frequently observed in the periphery of all secretory portions. Immunofluorescence assays revealed that the distal portion of the lateral lobes contains apyrase, an enzyme putatively responsible for platelet aggregation inhibition, diffusely distributed in the cell cytoplasm.     

On the serotonergic nervous system of two planktonic rotifers, Conochilus coenobasis and C. dossuarius (Monogononta, Flosculariacea, Conochilidae)

The serotonergic nervous systems of two non-colonial species of Conochilus were examined to obtain the first immunohistochemical insights into the neuroanatomy of species of Flosculariacea (Rotifera, Monogononta). Species of Conochilus, subgenus Conochiloides, were examined using serotonin (5-HT) immunohistochemistry, epifluorescence and confocal laser scanning microscopy, and 3D computer imaging software. In specimens of C. coenobasis and C. dossuarius, the serotonergic nervous system is defined by a dorsal cerebral ganglion, apically directed cerebral neurites, and paired nerve cords. The cerebral ganglion contains approximately four pairs of small 5-HT-immunoreactive perikarya; one pair innervates the posterior nerve cords and three pairs innervate the apical field. The most dorsal pair innervates a coronal nerve ring that encircles the apical field. Within the apical field is a second nerve ring that outlines the inner border of the coronal cilia. Together, both the inner and outer nerve rings may function to modulate ciliary activity of the corona. The other two pairs of perikarya innervate a region around the mouth. Specific differences in the distribution of serotonergic neurons between species of Conochilus and previously examined ploimate rotifers include the following: (a) a lack of immunoreactivity in the mastax; (b) a greater number of apically directed serotonergic neurites; and (c) a complete innervation of the corona in both species of Conochilus. These differences in nervous system immunohistochemistry are discussed in reference to the phylogeny of the Monogononta.