A novel spermatozoan ultrastructure in the shrimp Hippolyte obliquimanus Dana, 1852 (Decapoda: Caridea: Hippolytidae)

The aim of this study was to describe and illustrate the morphology of the spermatozoon of the Western Atlantic shrimp, Hippolyte obliquimanus. Individuals were sampled from Itagua Beach (Ubatuba, southern Brazil). The male reproductive system was dissected and morphological analysis was undertaken using a stereomicroscope, a light microscope, and transmission electron and scanning electron microscopes. When viewed from the nuclear or acrosomal poles, each spermatozoon has many translucent radiating arms (about 20) from a denser cell body, while laterally the cell body and arms resemble a "cnidarian medusa", with all the arms projecting away from the bell-like cell body. This sperm morphology is distinct from the "thumbtack"-shaped spermatozoa observed in the majority of carideans but has similarities to the spermatozoa of Rhynchocinetes spp. The morphology of sperm of several species of the genus Hippolyte resembles the spermatozoon of H. obliquimanus with the presence of posterior nuclear arms, but it is necessary to study other Hippolyte species to place these arms in the context of the genus.

Fatigue Reliability of 3 Single-Unit Implant-Abutment Designs

Objectives: Because the mechanical behavior of the implant-abutment system is critical for the longevity of implant-supported reconstructions, this study evaluated the fatigue reliability of different implant-abutment systems used as single-unit crowns and their failure modes. Methods and Materials: Sixty-three Ti-6Al-4V implants were divided in 3 groups: Replace Select (RS); IC-IMP Osseotite; and Unitite were restored with their respective abutments. Anatomically correct central incisor metal crowns were cemented and subjected to separate single load to failure tests and step-stress accelerated life testing (n = 18). A master Weibull curve and reliability for a mission of 50,000 cycles at 200 N were calculated. Polarized-light and scanning electron microscopes were used for failure analyses. Results: The load at failure mean values during step-stress accelerated life testing were 348.14 N for RS, 324.07 N for Osseotite, and 321.29 N for the Unitite systems. No differences in reliability levels were detected between systems, and only the RS system mechanical failures were shown to be accelerated by damage accumulation. Failure modes differed between systems. Conclusions: The 3 evaluated systems did not present significantly different reliability; however, failure modes were different. (Implant Dent 2012;21:67-71)