Female Aperture Research Articles

OCCURRENCE OF PROTANDRIC HERMAPHRODITISM IN A POPULATION OF THE NEOTROPICAL FRESHWATER CRAYFISH PARASTACUS BRASILIENSIS (PARASTACIDAE)

Preliminary studies have shown that males and females of the freshwater crayfish Parastacus brasiliensis (von Martens, 1869) have an intersexed internal genitalia characterized by the existence of genital ducts of both sexes that connect to a gonad with male or female components, according to the sex. To determine the type of sexuality of this species, specimens (n = 92) from 11.7 to 40.0 mm carapace length were collected at Mariana Pimentel municipality, Rio Grande do Sul, Brazil (30°20′39″S, 51°22′39″W). Anatomical and histological analysis of the gonads disclosed the existence of three sexual forms: (1) intersexed males (n = 36), (2) transitionals between male and female sex (n = 8), and (3) intersexed females (n = 48). The transitionals present the following common morphological features: both genital apertures are present, but the female apertures are closed, as is usual in males; coexistence of oocytes and testicular acini in the same gonad (ootestis); and a longitudinal collecting tubule, large in diameter in the testicular region. The ovarian component of the gonad includes previtellogenic and primary vitellogenic oocytes. Of the 44 individuals classified as males by the analysis of the aspect of the genital apertures, 18.2% were transitionals, suggesting the existence of primary males that never change sex and a sexual system that is known as partial protandry. The existence of small females suggests that some females never go through a male phase. The histology of the gonads and genital ducts is described, and the germ cells are identified in each sex. The possible reasons for the existence of hermaphroditism in the studied population are discussed based on theoretical models.

Occurrence of Protandric Hermaphroditism in a Population of the Neotropical Freshwater Crayfish Parastacus Brasiliensis (Parastacidae)

Preliminary studies have shown that males and females of the freshwater crayfish Parastacus brasiliensis (von Martens, 1869) have an intersexed internal genitalia characterized by the existence of genital ducts of both sexes that connect to a gonad with male or female components, according to the sex. To determine the type of sexuality of this species, specimens (n = 92) from 11.7 to 40.0 mm carapace length were collected at Mariana Pimentel municipality, Rio Grande do Sul, Brazil (30°20′39″S, 51°22′39″W). Anatomical and histological analysis of the gonads disclosed the existence of three sexual forms: (1) intersexed males (n = 36), (2) transitionals between male and female sex (n = 8), and (3) intersexed females (n = 48). The transitionals present the following common morphological features: both genital apertures are present, but the female apertures are closed, as is usual in males; coexistence of oocytes and testicular acini in the same gonad (ootestis); and a longitudinal collecting tubule, large in diameter in the testicular region. The ovarian component of the gonad includes previtellogenic and primary vitellogenic oocytes. Of the 44 individuals classified as males by the analysis of the aspect of the genital apertures, 18.2% were transitionals, suggesting the existence of primary males that never change sex and a sexual system that is known as partial protandry. The existence of small females suggests that some females never go through a male phase. The histology of the gonads and genital ducts is described, and the germ cells are identified in each sex. The possible reasons for the existence of hermaphroditism in the studied population are discussed based on theoretical models.

Observations on the opisthobranch mollusc Acteon tornatilis (L.).

SummaryActeon tornatilis is an opisthobranch mollusc which burrows in sand, using foot, labial and cephalic tentacles in the process. The last also help to exclude sand from the mantle cavity, which is extended into a caecum coiling alongside the visceral hump, presumably used for respiration but also for excretion. The main pallial water current is an exhalant one on the right.The mantle skirt carries, on the left, numerous repugnatorial glands with toxic secretions.Labial glands lie at the mouth and the buccal cavity contains jaws and a reduced buccal mass and radula. Into it open salivary glands the structure of which is like that of the pyramidellids. The oesophagus shows traces neither of glands nor of torsion whereas the stomach, though simplified, has resemblances to that of a prosobranch.The reproductive system is shown to be different from previous descriptions. Male and female ducts are separate from the lower end of the little hermaphrodite duct. The former passes to a prostate from which a vas deferens leads to a large uninvaginable penis; the latter has associated albumen and mucous glands and there is a receptaculum seminis to the duct of which a ventral channel leads from the female aperture in the mantle cavity.Discussion of these aspects of the animal's structure confirms its position as the most primitive of the opisthobranchs.

The mechanism of insemination in the argasid tick, Ornithodorus moubata Murray

The spermatophore in Ornithodorus moubata consists of a bulb with a neck at the end of which are two large capsules. When the spermatophore issues from the male opening the capsules are invaginated into the bulb to form a compact but tense object which the male applies to the female aperture with his proboscis. The male releases his grip on the neck, and the tension in the walls of the bulb causes the capsules to evaginate and thus enter the uterus of the female.

XXXII.—A Specimen of Helix pomatia with Paired Male Organs

Summary1. An account is given of a fully grown specimen of Helix pomatia, which, in addition to the normal set of reproductive organs present on the right side, possesses also on the left side a set of accessory male organs—namely, a penis and its retractor muscle, vas deferens, and flagellum. There is no trace of connection between these supernumerary organs and the ovotestis or the genital ducts of the right side.2. The normal and supernumerary penes are equally developed and are symmetrically placed with regard to the median plane of the head.3. The extra penis has the usual structure; it possesses a fully-developed copulatory organ and a muscular tubular introvert upon the inner sheath.4. The extra vas deferens opens at one end into the penis and at the other terminates blindly in the sub-epidermal tissue; the blind end is bound to the epidermis by a short cord of connective tissue.5. The extra flagellum is normal in size and in its internal structure.6. The penial nerves on both sides have a corresponding course from the cerebral ganglion to their distribution on the penes. Owing to defective preservation it was impossible to determine whether the fibres of the extra penial nerve arise from the ocular nerve, as is apparently the case, or whether they really arise from the pedal ganglion, as do those of the normal penial nerve.7. The penis opens into a short atrium which communicates with the exterior by a genital aperture of normal size and shape. This supernumerary genital aperture occupies a position on the left side exactly corresponding to that of the normal one on the right side. About 2·5 mm. posterior and slightly dorsal to it is the blind end of the vas deferens, which is situated close to the dorsal margin of the epidermal groove, which traverses the anterior portion of the animal.8. In the duplication of the penis and its associated structures this snail presents an example of lateral homoeosis. The only comparable cases recorded in the Mollusca are a Pteropod with paired penes (see Addendum, p. 327) and a specimen of Moschites cirrosa, in which not only was the third right arm hectocotylised as usual, but the third left one also.9. The supplementary vas deferens and the retracted penis form a U-shaped loop, both ends of which are in contact with the epidermis, and so closely resemble the corresponding structures figured by Plate in the primitive Pulmonate, Pythia scarabeus, that these organs may be described as having identical relations in the two forms, except that in the supplementary organs of Helix the vas deferens has no actual opening at its epidermal end and that it bears a flagellum which is not present in Pythia. It is suggested that the supplementary organs of Helix, having been able to develop free from the disturbing influence of the vagina, oviduct, and their accessory structures (which on the right side have been secondarily moved forwards in phylogeny), have assumed a condition closely resembling that which they would present in the ancestral form in which male and female apertures were some distance apart. The form of the extra organs (the vas deferens having a close connection at one end with the epidermis), which, it is suggested, might also be assumed by the corresponding normal organs if they were also free to develop independently of the female structures, supports the view that the present condition of the genital ducts in Helix and in other Stylommatophora, has been derived from a condition existing in the ancestral form in which the vas deferens and penis were connected with the primitive genital opening by means of a lateral groove, such as is still found in Pythia.10. Consideration of this and of other abnormalities which have been described in the Pulmonata leads to the conclusion that the penis develops as an epidermal structure which in Helix and other Stylommatophora is closely associated with, and is secondarily carried inwards by, the invaginating atrium. In proterogynously hermaphrodite forms, especially in those in which the shell is depressed, reduced, or absent, the development of the penis rudiment may be postponed until the male elements in the gonad are further developed.