Functional morphology of the seminal receptacle of Mithrax, Mithraculus and Omalacantha spider crabs (Brachyura: Mithracidae).

Most Majoidea crabs display high sperm competition rates due to the development of spermatic strata within the seminal receptacle (SR). To verify the occurrence of sperm competition, SR anatomy and histochemistry analyses were performed in Mithrax hispidus, Omalacantha bicornuta, and Mithraculus forceps. The SR of the three Mithracidae species is classified into two regions, one of mesodermal origin (dorsal), consisting of a stratified epithelium with desquamation cells that produce a holocrine secretion, and the other, an ectodermal region (ventral) comprising a simple cubic epithelium covered by a cuticle. The oviduct opens in a ventral position near the transition region, which exhibits more pronounced folds on the opposite face of the oviduct, which may aid fertilization due to the presence of an external musculature. Sperm masses in a circular format were observed in the SR lumen, reminiscent of coenospermic spermatophores, and no morphological evidence strata of sperm packets were observed in any of the three studied species. The ventral SR followed the most common pattern observed in Majoidea. The secretion produced in the receptacle is composed of glycoproteins, with neutral polysaccharides. Acidic polysaccharides probably play a role against microorganisms from male seminal fluid. Due to the absence sperm packets, we were unable to determine whether the investigated females receive material from more than one male nor (if this does, in fact, occur) whether any preference for the spermatozoa of one male over another takes place during fertilization, that can may indicate the absence of sperm competition in the investigated species.

Ovarian development in swimming crabs: Comparative histochemistry and ultrastructure of Callinectes ornatus and Arenaeus cribrarius (Brachyura, Portunidae).

The ovarian development of Callinectes ornatus and Arenaeus cribrarius was described using histochemistry and ultrastructure. Both species shows the same ovarian stages, which are the juvenile (JUV), adult rudimentary (RUD), developing (DEV), intermediary (INT), mature (MAT), and spent (OV) stages. The JUV and RUD stages showed similar characteristics, and previtellogenesis is characterized by meiotic prophase chromosomes. In the primary vitellogenesis, the oocyte cytoplasm shows many small and large cytoplasmic glycoprotein vesicles. These vesicles correspond to the dilated cisternae of the rough endoplasmic reticulum (RER), which produces the immature (endogenous) yolk. Secondary vitellogenesis (exogenous phase) begins at the DEV stage with the fusion of pinocytic vesicles and vesicles with immature yolks to form mature yolk granules. At the INT stage, the formation of the chorion begins, and the mature yolks increase in size and number, while the RER diminishes. In the MAT stage, the oocytes are completely formed, and the cytoplasm is filled with mature yolk, lipid droplets, and glycogen. There are no significant variations between the gonadosomatic and hepatosomatic indices, which allows us to infer that the transfer of reserves from the hepatopancreas is nearly constant during ovarian development, since we observed primiparous and multiparous females in the same sampled population.

Surface-sediment and hermit-crab contamination by butyltins in southeastern Atlantic estuaries after ban of TBT-based antifouling paints.

Butyltin (BT) contamination was evaluated in hermit crabs from 25 estuaries and in sediments from 13 of these estuaries along about 2,000 km of the Brazilian coast. BT contamination in hermit crabs ranged from 2.22 to 1,746 ng Sn g(-1) of DBT and 1.32 to 318 ng Sn g(-1) of TBT. In sediment samples, the concentration also varied widely, from 25 to 1,304 ng Sn g(-1) of MBT, from 7 to 158 ng Sn g(-1) of DBT, and from 8 to 565 ng Sn g(-1) of TBT. BTs are still being found in surface sediments and biota of the estuaries after the international and Brazilian bans, showing heterogeneous distribution among and within estuaries. Although hermit crabs were previously tested as an indicator of recent BT contamination, the results indicate the presence of contamination, probably from resuspension of BTs from deeper water of the estuary.

A new strategy of endosymbiont midgut bacteria in ant (Ponerinae).

The location and ultrastructure of bacteria associated with microvilli in the midgut of Odontomachus bauri were examined by transmission electron microscopy. These filamentous type bacteria are the second morphotype described in the midgut of this ant. They colonizes only the ectoperitrophic space, more specifically attaching along microvilli. A thick capsule attaches bacteria to microvilli and protect them from acidic pH and digestive enzymes. Details of the location and association with microvilli are discussed.

First report of endocytobionts in the digestive tract of ponerine ants.

We conducted ultrastructural studies to examine the presence of microorganisms in the midgut of the ant Odontomachus bauri (Ponerinae), as a contribution towards understanding the relationships between microorganisms and their hosts. The presence of microorganisms in this region, including inside the cells, suggests their participation in food digestion as symbiontic organisms and represent a new possibility to exploit food sources in the environment.

Contribution of the Malpighian tubules for the maintenance of symbiotic microorganisms in cephalotes ants.

Given the physiological importance of the Malpighian tubules to homeostasis in ants, this study aimed to characterize the enzymology, histology, histochemistry, and ultramorphology of the Malpighian tubules of Cephalotes atratus, C. clypeatus, and C. pusillus, as a contribution for the understanding of this organ, as well as to examine its role in the maintenance of symbiontic microorganisms in the ileum of these ants.

Histology and histochemistry of the ventriculus of Dolichoderus (=Monacis) bispinosus (OLIVIER, 1792) (Hymenoptera: Formicidae).

In this study we histologically and histochemically describe the ventriculus of Dolichoderus bispinosus. The epithelium consists of two basic cell types, highly basophilic generative cells, and digestive cells. The latter present several cytoplasmic vesicles, rich in acidic and neutral polysaccharides, and basic proteins. Also, these cells exhibit an apocrine secretion pattern. A mass of fibrous material is observed on the surface of the epithelium. Finally, we discuss the results obtained.

Ultramorphology and histochemistry of fat body cells from last instar larval of the Pachycondyla (=Neoponera) villosa (Fabricius) (Formicidae: Ponerinae).

The fat body cells of Pachycondyla (=Neoponera) villosa are disposed in a single layer between the cuticle and the digestive tract, forming a group of cells enclosed by a thin membrane. Histological studies have revealed three different cellular types: trophocyte (more abundant), urate, (located among the trophocytes), and oenocyte (the scarcest), usually observed laying near the cuticle. Histochemically, the trophocytes showed a positive reaction for basic proteins in the nucleus and cytoplasm, as well as a strong positive reaction in the cytoplasmic granules. The test for carbohydrates showed a strong positive reaction throughout the cytoplasm, while the test for lipids was positive for the cytoplasmic vesicles. The urate cells showed a positive reaction for basic proteins in the nucleus and in the areas of the cytoplasm surrounding the vesicles. These cells did not react to the PAS test or to Sudan Black B. The oenocytes showed a weak positive reaction to PAS and a strong positive reaction to Sudan Black B and Mercuric-bromophenol Blue.

Ultramorphology and histochemistry of fat body cells from last Instar larval of the Pachycondyla (=Neoponera) villosa (Fabricius) (Formicidae: Ponerinae)

As células do corpo gorduroso de Pachycondyla (=Neoponera) villosa distribuem-se como uma única camada entre a cutícula e o trato digestivo, formando um conjunto de células agrupadas e recobertas por uma fina membrana. Não foram identificados tipos celulares distintos por meio da ultramorfologia, porém a histologia revelou três tipos celulares distintos: os trofócitos, mais abundantes, as células de urato, distribuídas por entre os trofócitos, e os enócitos, menos abundantes que os demais. Os enócitos são comumente observados próximos da cutícula. Histoquimicamente, os trofócitos apresentaram reação positiva para proteínas básicas no núcleo e no citoplasma e reação fortemente positiva nos grânulos citoplasmáticos. O teste para carboidratos foi fortemente positivo em todo o citoplasma, enquanto para os lipídeos observou-se reação positiva nas vesículas citoplasmáticas. Em relação às células de urato, estas apresentaram reação positiva para proteínas básicas no núcleo e citoplasma, por entre as vesículas. Essas células não apresentaram reação para o teste de PAS e Sudan Black B. Quanto aos enócitos, estes apresentaram citoplasma fracamente positivo ao PAS e fortemente positivo ao Sudan Black B e para o azul de bromofenol.

Macromolecular array patterns of silk gland secretion in social Hymenoptera larvae

The cocoon, produced by most holometabolous insects, is built with silk that is usually produced by the larval salivary gland. Although this silk has been widely studied in the Lepidoptera, its composition and macromolecular arrangement remains unknown in the Hymenoptera. The macromolecular array patterns of the silk in the larval salivary gland of some meliponids, wasps, and ants were analyzed with polarized-light microscopy, and they were compared with those of Bombyx mori (Lepidoptera). There is a birefringent secretion in the glandular lumen of all larvae, due to filamentous structural proteins that display anisotropy. The silk in the distal, middle and proximal regions of the secretory portion of Formicidae and Vespidae glands presented a lattice optical pattern. We found a different pattern in the middle secretory portion of the Meliponini, with a zigzag rather than a lattice pattern. This indicates that the biopolymer fibers begin their macromolecular reorganization at this glandular region, different from the Formicidae and the Vespidae, in which the zigzag optical pattern was only found at the lateral duct. Probably, the mechanism of silk production in the Hymenoptera is a characteristic inherited from a common ancestor of Vespoidea and Sphecoidea; the alterations in the pattern observed in the Meliponini could be a derived characteristic in the Hymenoptera. We found no similarity in the macromolecular reorganization patterns of the silk between the Hymenoptera species and the silkworm.