Improved Method of Typing Bradyrhizobium japonicum in Soybean Nodules

An improved method for antibiotic resistance recovery of Bradyrhizobium japonicum from soybean (Glycine max (L.) Merr.) nodules that is simple, time saving, and economical was developed. This technique involves the use of two 96-well microtiter plates as a multinodule sterilization chamber and a template and a third plate as a 16-point replicator constructed with steel nails affixed to the plate with epoxy cement. With this system a team of four technicians could type 3,000 nodules per day. This method was useful in assessing strain establishment and interstrain competition when one or more uniquely labeled strains of B. japonicum were inoculated onto either growth-room- or field-grown soybeans. Contamination was low and reproducibility across replicates approached the theoretical upper limit. Simplicity in design and use made this recovery method especially adaptable for field studies in which large numbers of nodules were required to provide a representative statistical sample offering good precision.     

Determinants of Dominance in the Tree Lizard Urosaurus ornatus: the Relative Importance of Mass,Previous Experience and Coloration

A determination of some of the factors that predict the outcome of contests between male tree lizards, Urosaurus ornatus, was made using logistic regression modelling on matched-pair data. Two-day-long encounters were staged between pairs of males differing in size (snout-vent length and mass), previous contest status (previous winners and previous losers), and coloration (dorsal coloration during their previous contest and throat coloration, a fixed trait). Mass proved to be the best single predictor of contest outcome, resulting in an 80% correct classification rate for predicting winners and losers, far better than the less than 57% correct classification rate for snout-vent length. Previous social status (winner or loser) also was a powerful single predictor of contest outcome with a 793% correct classification rate, as was previous dorsal coloration (76.7%). When combined, mass and previous status produced the strongest combination of predictors with a better than 86% correct classification rate. Contrary to several previous studies, which implicated throat coloration as an important status signal of dominance, our results failed to show that throat coloration is a strong predictor of contest outcome. Possible reasons for this discrepancy with earlier findings are discussed. The logistic regression models also allow prediction of the magnitude of difference in mass between two contestants for there to be an equal chance of winning, given a second asymmetry in contest predictors.     

Selfing versus outcrossing in the androdioecious clam shrimp,Eulimnadia texana (Crustacea,Conchostraca)

The clam shrimpEulimnadia texana is an androdioecious crustacean in which hermaphrodites may self fertilize or outcross with males but cannot outcross with other hermaphrodites. Outcrossing is maintained within most populations of this species despite the high genetic cost of sex, suggesting that compensating factors provide an advantage to outcrossing. We hypothesized that one such benefit would be the production of larger clutch sizes resulting from outcrossed matings. To test this prediction, we recorded the body sizes and clutch sizes of hermaphrodites which mated via selfing or bia outcrossing. Clutch sizes showed significant, almost exponential, increases as body size increased in both selfing and outcrossing hernmaphrodites. The rate of this increase was the same for both groups, and there was no significant difference in clutch size when body size was controlled for between the two fertilization types.     

Distastefulness as a defense mechanism in Aplysia brasiliana (Mollusca: Gastropoda)

An unusual courtship pattern for fiddler crabs is described from field observations in Panama. This behavior pattern, referred to here as “directing,” differs considerably from the more frequently observed communal courtship system found in close relatives of Uca deichmanni. A male involved in “directing” approaches a female and attempts to carry or maneuver her into his burrow for mating. The female usually struggles to escape from the male. This activity often attracts other males which attempt to “direct” the female if she escapes from the first male. A male is most successful in “directing” a female into his burrow if a) he is larger than the female, b) the female is wandering (a sign of physiological receptivity) prior to the “directing” attempt, and c) several males attempt to “direct” the female at once. The results suggest that females are choosing mates by inciting several males to compete for them. The males which successfully “direct” the struggling females are probably the most fit males.     

Improved felid embryo development by group culture is maintained with heterospecific companions

Domestic cat embryos of excellent quality appear to improve development of conspecific embryos when cultured together, providing an avenue for improving development of embryos from valuable species or individuals. To have relevance to rare species, it would be useful to understand if this advantage could be conferred by heterospecific companions because there usually are severely limited numbers of conspecific embryos available from wildlife donors. In the first study, we incubated single test cat embryos alone (controls) or with 10 cat embryos or 10 or 20 mouse embryos under similar regimented conditions (each group shared 20 microl medium). In the second study, single test cat embryos were cultured alone, with 10 conspecific or 20 mouse embryos or 10 cattle embryos (each group shared 20 microl medium). Single test embryos in all treatment groups achieved similar (P>0.05) stages of compaction and blastocyst development. In the first study, only the test embryos incubated with 10 cat or 20 mouse companion embryos achieved blastocyst expansion. The average total cell number within test embryos incubated with 10 cat or 20 mouse companions was greater (P<0.05) than controls or those placed with 10 mouse embryos. In the second study, test embryos in all groups achieved blastocyst expansion and had more (P<0.05) total cells per embryo than the solitary controls. Inner cell mass to trophoblast cell ratio did not differ among treatments in either study. Thus, companion mouse and cattle embryos selected for excellent quality confer a benefit to singleton cat embryos, although the number of companions necessary to grant an advantage may be species dependent. If this phenomenon can be extrapolated across species, this may be an avenue for 'common animal embryos' to improve developmental potential of embryos from rare, unrelated taxa.     

Interspecific Communication in Fiddler Crabs: Preliminary Report of a Female Rejection Display Directed toward Courting Heterospecific ♂♂

A newly described display is apparently used by female fiddler crabs (genus Uca) in interspecific communication. The display, termed repetitive-high-rise, is directed primarily toward courting heterospecific ♂♂, which approach or are likely to approach the ♀. We postulate that the display serves to indicate the ♀'s unavailability to these ♂♂ for mating. The ♂♂ respond appropriately by ceasing their approach toward displaying ♀♀. Both reproductively receptive and unreceptive ♀♀ were observed to perform this display. ♀♀ appeared to be able to discriminate, not only between conspecific ♂♂ and heterospecific ♂♂, but also among ♂♂ of heterospecific species. The possible significance for this ability is discussed.     

Birth of a Western Lowland gorilla (Gorilla gorilla gorilla) following in vitro fertilization and embryo transfer

A 21-year-old multiparous female exhibiting 31–41 day menstrual cycles was given hFSH (225 IU/day, Metrodin 75, from cycle day 3 through 9 (menses = day 1) and hCG (10,000 IU, Profasi, on day 10 to stimulate follicular development. At 35 h after hCG, under isoflurane (AErrane) anesthesia, follicles were aspirated by controlled suction under transvaginal ultrasound guidance. Metaphase II oocyctes (n = 11) were placed in modified human tubal fluid (mHTF, 100 μl) medium under oil at 37°C in humidified 5% CO₂. Frozen semen, collected by voluntary ejaculation, was thawed (70°C H₂O bath, 6 sec), diluted slowly, centrifuged, and resuspended in mHTF, and 160,000 motile spermatozoa/ml were added at 6 h after oocyte recovery. At 21 h postinsemination (p.i.) eight oocytes were at the two-cell stage, five were cryopreserved, and three were cultured to the six- to eight-cell stage in mHTF with granulosa cells before transcervical uterine transfer at 47 h p.i. using a Teflon catheter. Micronized progesterone (400 mg/d) was orally administered for 10 weeks posttransfer (p.t.). Ultrasound examination revealed a single fetus at 15 weeks p.t., and unassisted delivery of a live 1.37 kg female infant occurred at 29 weeks. Am. J. Primatol. 41:247–260, 1997. © 1997 Wiley-Liss, Inc.     

Anatomical evidence for androdioecy in the clam shrimp Eulimnadia texana

Recent genetic evidence suggests that the clam shrimp Eulimnadia texana exhibits androdioecy, a rare mating system. In this system, individuals are either hermaphrodites or males, pure females not being found. Through the use of light microscopy, this study provides anatomical evidence that egg-bearing individuals are, indeed, hermaphrodites. All such individuals observed possess ovotestes with testicular tissue restricted to the posterior region of the gonad. Developing sperms in hermaphrodites are similar in appearance to those seen in male-only individuals. This revised version was published online in August 2006 with corrections to the Cover Date.