Modeling the effects of El Niño, density-dependence, and disturbance on harbor seal (Phoca vitulina) counts in Drakes Estero, California: 1997–2007

Harbor seal ( Phoca vitulina ) haul-out site use may be affected by natural or anthropogenic factors. Here, we use an 11-yr (1997–2007) study of a seal colony located near a mariculture operation in Drakes Estero, California, to test for natural (El Niño-Southern Oscillation (ENSO), density-dependence, long-term trends) and anthropogenic (disturbance or displacement related to oyster production activities) factors that may influence the use of haul-out subsites. Annual mariculture related seal disturbance rates increased significantly with increases in oyster harvest ( r _s= 0.55). Using generalized linear models (GLMs) ranked by best fit and Akaike's Information Criteria, ENSO and oyster production (as a proxy for disturbance/displacement) best explained the patterns of seal use at all three subsites near the mariculture operations, with effects being stronger at the two subsites closest to operations. Conversely, density-dependence and linear trend effects poorly explained the counts at these subsites. We conclude that a combination of ENSO and mariculture activities best explain the patterns of seal haul-out use during the breeding/pupping season at the seal haul-out sites closest to oyster activities.     

Release of arachidonic acid from human endometrial cells in culture mediated by calcium ionophore (A23187) or fluoride.

Primary cultures of endometrial glands and stromal cells were labelled with [14C]-arachidonic acid for 4 h before exposure to either the calcium ionophore, A23187 (which activates phospholipase A2 (PLA2) by increasing intracellular calcium concentrations) or sodium fluoride (which activates a G-protein). Calcium ionophore (0.5-50 mumol/l) stimulated a dose- and time-dependent release of arachidonic acid from endometrial glands. Incubation with ionophore (10 mumol/l) for 1 h released 22% of the incorporated arachidonic acid. There was a corresponding decrease in phospholipids and no loss from triglycerides. Stromal cells were unresponsive to ionophore. Fluoride (10 mmol/l) stimulated a release of arachidonic acid from stromal cells and endometrial glands (6.5% of the total arachidonic acid incorporated). In stromal cells, arachidonic acid was released from triglycerides in Day-1 cultures and from phospholipids in Day-2 cultures. In both Day-1 and Day-2 cultures of endometrial glands, arachidonic acid was released from phospholipids, but not from triglycerides. Among the phospholipids, phosphatidylcholine was always the major source of arachidonic acid. Arachidonic acid release from endometrial glands and stromal cells may be mediated by activation of PLA2 (or phospholipase C) via a G-protein, but in glands calcium ionophore may have a direct effect on PLA2. The response to calcium ionophore may reflect the differences in calcium requirements of the two endometrial PLA2 isoenzymes.     

Reproductive biology of the male bent-winged bat, Miniopterus schreibersii (Vespertilionidae) in southeast South Australia

The seasonal chronology of the events of the reproductive cycle, and changes in the structure and function of the primary and accessory organs of the male bent-winged bat, Miniopterus schreibersii, were studied at latitude 37 degrees S in temperate southeastern Australia. The testicular cycle commenced in late spring (November), and sperm appeared in the seminiferous tubules and epididymides in early fall (March). The cycle of the accessory sex gland complex generally paralleled the testicular cycle, reaching maximum hypertrophy at the time of insemination in late fall (April/May). Thereafter, the primary and secondary sex glands (except the ampullary gland) involuted as the animals entered winter torpor. However, a cauda epididymal store of sperm persisted until late spring, and sperm were often observed, as well, in the ampullary gland duct and alveoli throughout winter. This study has confirmed that male Miniopterus differs from other vespertilionids in that accessory gland activity declines following the fall breeding in keeping with the fact that, unlike in other vespertilionids, insemination, ovulation and conception are concurrent events in the fall in this species. The reduced secretory status of the Leydig cells and exceptionally low levels of circulating androgens throughout the year, in combination with the presence of viable epididymidal sperm for most of gestation, are all interesting features of this reproductive cycle.