Morphology of the EGG of Sarcodexia lambens (Diptera: sarcophagidae)

The egg of Sarcodexia lambens (Diptera: Sarcophagidae) is described on the basis of scanning electron microscopy

Structure of the zona pellucida and cumulus oophorus in three species of native Australian rodents.

The sperm head of many Australian hydromyine rodents has three curved hooks projecting from its anterior margin; the structure of the hooks has been characterized, but their function is unknown. In this study, we have investigated whether the hooks might have evolved to assist sperm penetration through more formidable egg vestments, particularly the zona pellucida. Cumulus-oocyte complexes were obtained from two species that possess a three-hooked sperm head (Pseudomys australis and P. nanus) and one species that does not (Notomys alexis) and examined by light and electron microscopy. After fixation in the presence of ruthenium red, the zona pellucida was found to consist of a fibrillar meshwork, but there were no interspecific structural differences. A corona radiata was absent, and the cumulus extracellular matrix was composed of filaments and electron-dense granules in each species. Measurements of the zona thickness in freshly ovulated, unfixed oocytes revealed that it was thinnest (7.8 microns) in P. australis, which has a three-hooked sperm head, and thickest (11.4 microns) in N. alexis, the species in which the ventral hooks are absent. Hence, no correlation was found between the thickness of the zona pellucida or the structure of the cumulus-oocyte complex, and the presence of three hooks on the sperm head. We conclude, therefore, that it is unlikely that the evolution of the three-hooked sperm head is an adaptation for penetration of increased barriers around the oocyte.

Morphological observations on the egg and first instar larva of metacuterelba apicalis (Diptera: cuterebidae)

O ovo e a larva de primeiro estágio de Metacuterebra apicalis (Diptera, Cuterebridae) säo descritos a nível de microscopia óptica e eletrônica de varredura

Phenotypic differences in Schistosoma mattheei ova from populations sympatric and allopatric to S. haematobium.

Schistosoma mattheei ova were collected from cattle in different localities in South Africa and after hatching, miracidia were used to infest Bulinus (Physopsis) globosus. Cercariae harvested from these snails were used to infest the definitive host Praomys (Mastomys) coucha and eggs from the resulting female S. mattheei were collected. These ova were compared with a Schistosoma haematobium X S. mattheei hybrid similarly collected from an infested P. (M.) coucha. The results indicate that S. mattheei populations which are sympatric to S. haematobium possess S. haematobium characteristics. It is suggested that the gene pools of populations of the parasite in these areas are infiltrated with S. haematobium genes via the S. mattheei X S. haematobium hybrid originating from human hosts.

The blood vascular system in the head of the herring gull (Larus argentatus).

The structure and development of the blood vascular system in the head of the herring gull (Larus argentatus) have been studied using injection techniques and histological sections. Three different but interconnected divisions of the arterial system are recognized in the adult: the cerebral carotid artery system, the external ophthalmic artery system, and the external carotid artery system. Embryologically, the arterial system is characterized by changes in the relative development of these divisions; the cerebral carotid system being the most prominent in the first half of the embryonic period. The venous system is divided into two parts, the rostral cephalic system and the caudal cephalic system, which drain separate regions of the head. The Rete ophthalmicum , which is an arteriovenous network associated with the external ophthalmic artery system, can be identified from the fifth day of incubation, and its development appears to be coupled with changes in the arterial supply to the eye. The possibility of a homology between the Rete ophthalmicum of birds and the Rete caroticum of mammals is briefly discussed.

Observations on Graafian follicles and their oocytes during lactation and after the removal of pouch young in the marsupials Isoodon macrourus and Perameles nasuta.

Ovaries from 63 bandicoots (Isoodon macrourus and Perameles nasuta) were collected in order to obtain Graafian follicles close to ovulation for light and electron microscopy. During the first 42 days of lactation (lactation c. 60 days), the follicles were less than 1.0 mm in diameter, whereas from 43 to 52 days, some animals had follicles up to 2.0 mm in diameter, or ovulation had occurred and new corpora lutea were present. This ovulation was associated with the lactation estrus that occurred in some animals. In general, the largest Graafian follicles of the bandicoots were morphologically similar and resembled those of many other mammals. These follicles protruded from the surface of the ovary and revealed a conspicuous theca interna. The granulosa cells exhibited an unusual feature in that they contained masses of glycogen, often associated with lipid droplets and filaments. The oocytes were similar in size (diameter c. 150 microns) to those of some other marsupials and were surrounded by a zona pellucida and cumulus cells attached to the granulosa layer. The cumulus cells did not form a corona radiata as in eutherian mammals. The oocyte nuclei were somewhat flattened, peripherally located and similar in size (c. 40 x 19 microns) to those in other marsupials. These nuclei, which stained lightly with Azure A and were electron-lucent and homogeneous, were unusually irregular in contour. The nuclei were unique in that nucleoli were always absent. Small cytoplasmic bodies which may have been extruded nucleoli were found in the oocytes of I. macrourus, but not in P. nasuta. The cytoplasm in the bandicoot oocytes resembled that of other marsupials and some eutherians in that it was highly vacuolated with most of the organelles concentrated peripherally. Within the central region of the bandicoot oocytes there were crystalloids which were similar to those in oocytes of primordial follicles and in unilaminar blastocysts of I. macrourus.

Euparal as a permanent mounting medium for helminth eggs and proglottids.

The importance of euparal as a permanent mounting medium for eggs of parasites and the process of making permanent slides are analyzed and discussed in detail. Studies show that helminth eggs mounted in euparal exhibit excellent optical and drying properties. Euparal also can be used to identify proglottids of Taenia species and to examine for the presence of Trichinella spiralis in suspicious muscle biopsies.

Infection of man with Trichuris vulpis, the whipworm of dogs.

A gravid female Trichuris was found in histopathologic sections of an appendix in a post-mortem examination, and a posterior extremity of a male Trichuris was recovered from the unsectioned portion of the same appendix. These parasites were identified as T. vulpis, the whipworm of dogs.

Decussion geometrics in the goldfish nervous system: correlation with probability of survival.

In the goldfish, the optic nerve decussation occurs without intermingling of fibers from the two eyes. In two-thirds of juvenile and adult specimens, the left optic nerve is dorsal at the midline. In about 60% of the specimens, the decussation of Mauthner's neuron also has a left-dorsal-to-right (L/R) configuration. Concordance for decussation geometry is greater than 80%, with smaller specimens accounting for a disproportionate number of discordant cases. In embryos and very young larvae, the L/R configuration occurs in slightly less than 50% of optic chiasmata and in slightly more than 50% of Mauthner's cell chiasmata, and there is no significant tendency toward concordance. However, larval specimens that survive 1 month after hatching are markedly skewed toward adult decussation patterns and somewhat skewed toward concordance. These observations, together with results of cannibalization and predation experiments, suggest that the adult population pattern can be achieved through selection pressures against discordant individuals and, perhaps separately, against individuals with right-dorsal-to-left (R/L) chiasmatic configurations. Decussation patterns correlate with embryonic postures, larval orientation preferences, and growth rates after hatching, which may themselves serve as a basis for selection.

Egg size and form as taxonomic criteria in Diphyllobothrium (Cestoda, Pseudophyllidea).

The size and form (length, width, and length: width ratio) of eggs of Diphyllobothrium dendriticum, D. ditremum and D. latum vary considerably among individual worms within each species. The size of eggs varies with host species and a decrease in egg size with increasing intensity of infestation is indicated. The egg size of D. latum increases during the first 10-12 days of egg production. For single worm infections in golden hamsters the mean egg length and width of D. ditremum are significantly smaller than the corresponding means of D. dendriticum and D. latum, while D. latum has significantly wider eggs than D. dendriticum. As taxonomic characteristics, egg size and form may contribute to species delimitation at the population level. For identification at the individual level the best possible accuracy is about 80%. This accuracy is considerably reduced when variation in host species and intensities of infestations are introduced. Scanning electron microscope studies did not reveal any differences among eggs of the three species.

[Structure of ova and larvae of Diplozoon megan (Monogenoidea: Diplozoidae)]. / O stroenii iaits i lichinok Diplozoon megan (Monogenoidea: Diplozoidae).

Data are given on the structure of eggs and larvae of Diplozoon megan from the gills of the ide. The occurrence of local stock of these fishes in the Kurish Gulf is suggested.

Stimulation of repoduction in captivity of the wild rabbit, Oryctolagus cuniculus.

Female wild rabbits which failed to breed under laboratory conditions were treated with gonadotrophins and artificially inseminated with epididymal spermatozoa. The fertilized eggs so obtained were transferred to synchronous domestic rabbits. Altogether, 185 eggs were transferred to thirty-six recipients. Thirty-three of the recipients maintained pregnancy to term and nearly half of the transferred eggs developed into normal young. Birthweights ranged from 45 to 59 g. Postnatal survival was excellent. Females born in captivity remained sexually immature in spite of attaining normal adult body weights. Sexual development was apparently normal in the males, although most remained shy breeders. Incidental observations on ovarian response, egg size and rate of development are presented.