Functional anatomy of the female reproductive system of the American lobster (Homarus americanus).

Light microscopy studies of the female American lobster Homarus americanus reproductive system are essentially nonexistent or outdated. Based on samples taken in the spring, summer, and autumn from the southern Gulf of St. Lawrence between 1994 and 2014, and using a combination of histological and scanning electron microscope techniques, we propose an ovarian cycle with 10 stages, identifying for the first time a recovery stage. Also, an atypical resorption stage, characterized by massive reabsorption of mature oocytes, is occasionally observed during summer months. The oviducts are composed of connective tissue (elastic and collagen fibers) with no muscle or secretory activities. Their epithelium shows a cyclic pattern and phagocytosis activities linked to spawning. Although the role of the seminal receptacle is to store and protect semen, free spermatozoa (i.e., without the spermatophoric wall and the acellular gelatinous substance that constitute the semen) were also observed in its posteriolateral grooves immediately prior to spawning, which is consistent with an external fertilization mechanism at the seminal receptacle. Unexpectedly, free spermatozoa were observed externally near two pore-like structures located on the gonopore's operculum, not at the seminal receptacle, after spawning; hence, more work is needed to fully understand the fertilization mechanism for the American lobster.

Functional anatomy of the male reproductive system of the American lobster (Homarus americanus).

Despite supporting a valuable fishery, the reproductive system of the male American lobster (Homarus americanus) is poorly understood. The elongated H-shaped testis is responsible for spermatogenesis and is composed of follicles, a common collecting duct with interlaced scattered striated muscles, and a serosa as an external wall. Sertoli cells are associated with the spermatogenesis that produces spermatozoa, which are transferred to the collecting duct through a temporary passageway. Spermatogenesis is asynchronous between follicles and occurs on a continuous basis. The anterior and posterior lobes of the testes are independent and connect to the vasa deferentia through the Y-shaped collecting tubules that have a different cell anatomy and function than the two organs they connect. The vas deferens is divided into four regions. Spermatophores, produced in the proximal vas deferens, are packets of spermatozoa encapsulated in a single layer-the spermatophoric wall, which is composed of mucopolysaccharide acid. Large dense ovoid granules and the seminal fluid, composed of acidic sulfated mucosubstances, are secreted in the median vas deferens. Spermatophores within these secreted substances (i.e., semen) are stored in the distal vas deferens that, with the spermiduct (last region of the vas deferens), is responsible for the extrusion of the semen by striated muscle contractions. Smooth muscles suggest a peristaltic movement of the spermatophores within the vas deferens. Finally, the gonopores and the first pair of pleopods (i.e., gonopod) move the semen to the female seminal receptacle during copulation.

Auditory temporal gap detection in children with and without auditory processing disorder.

BACKGROUND: Auditory gap detection is a measure of temporal acuity. The paradigm comes in two forms, distinguished by whether the sounds bounding the silent period are the same (within channel [WC]) or different (between channel [BC]). PURPOSE: The purpose of this study was to test normal children and children referred for auditory processing disorder (APD) assessment, with both gap detection paradigms. RESEARCH DESIGN: Best gap durations (i.e., shortest reliably detected gaps) were measured in a two-interval, two-alternative forced-choice design embedded within a modified method of limits, for both WC and BC paradigms, with stimuli presented at 55 dB HL. STUDY SAMPLE: Sixteen control children and 20 children referred for APD assessment participated in the study. Of the 20 referred children, 9 were diagnostically positive for APD (APD+), and 11 were negative (APD-). The mean age of children in all three groups was 10-11 yr. DATA COLLECTION AND ANALYSIS: Data collected were best gap durations for each paradigm, for each child. Group differences were assessed using Kruskal-Wallis analyses of variance. RESULTS: WC best gap durations were very similar across the three participant groups. BC best gap durations varied significantly between listener groups, with the greatest difference being between controls and APD+ samples. CONCLUSIONS: BC best gap durations differed among the listener groups while WC ones did not. This suggests that the relative timing perceptual operations required by the BC task are more susceptible to the perceptual disturbances in APD than is the simple event detection required by the WC task.