Isolation and characterization of microsatellite loci from mother‐of‐millions,Bryophyllum delagoense (Crassulaceae), and its hybrid with Bryophyllum daigremontianum, ‘Houghton's hybrid’

Nine microsatellite loci were developed, and are transferable, across the Madagascan succulents Bryophyllum daigremontianum, Bryophyllum delagoense (mother‐of‐millions) and their horticultural hybrid (Houghton's), from enriched libraries of the later two species. For B. delagoense, a tetraploid, three to 13 alleles per locus were found for native Madagascan (H_O = 0.4–1.0), and one to nine in invasive Australian (H_O = 0.0–1.0) samples. In addition for 91 Australian samples, only five multilocus genotypes were found (95% of individuals were of two genotypes), suggesting extensive clonality in its introduced range. These loci will be used to examine genetic diversity, hybrid origin and mating system in natural and introduced populations.     

Temporal variation in gametogenic cycles of vesicomyid clams

Summary

Sulfide-rich cold seeps in Monterey Canyon support dense communities of vesicomyid clams, which harbor chemosynthetic bacterial endosymbionts. Because these animals rely upon non-photosynthetic food sources, their life histories may be decoupled from seasonal phytoplankton productivity. We examined this hypothesis by investigating temporal changes in gametogenesis in two vesicomyid clam species. Clams were collected from two cold seeps (600 m and 900 m depths), and their gonads were removed and processed for histological analyses. Oocyte diameters and relative abundances of tissue types were measured in thin sections taken across the gonad. Mean oocyte diameters of Calyptogena kilmeri increased from August to November, 1994, but did not change by March, 1995. Relative proportions of ovarian tissue types (reproductive vs. somatic) also changed during this period, indicating reproductive seasonality. Analyses of Calyptogena pacifica tissues showed no significant change within a 3-month period. Existence of seasonal cycles for vesicomyid clams suggests that either (1) chemosynthetic production is seasonal or (2) reproductive output is tied to factors other than food production, such as synchrony of spawning to maximize fertilization success, or larval survival.