The incidence of,and factors associated with,failure to mate by 245 days of age in the gilt

The incidence of, and factors associated with, gilts failing to mate between 29 and 35 weeks of age were studied over 12 months at a large intensive piggery in southern Australia. After excluding gilts culled as physically unsound, 10.5% of the remaining 2484 gilts failed to mate and were slaughtered.Seventy percent of unmated gilts had ovulated, and of these, 54% had shown negative or low responses to the back-pressure test (BPT) and 16% had shown moderate or high responses. Few prepubertal gilts (1%) had abnormal reproductive tracts.When group size was greater than 50 gilts (< 0.9 m²/gilt) immediately prior to mating (27–28 weeks of age), there was a higher incidence of unmated gilts and an increase in the proportion of unmated gilts which had shown negative or low BPT response than when groups were less than 50 gilts (12.9 vs. 8.6%, P < 0.001; and 8.0 vs. 3.6%, P < 0.001, respectively).The incidence of prepubertal gilts at 35 weeks was lower during spring than other seasons (1.48 and 3.36%, P < 0.05) and higher during summer than other seasons (4.61 and 2.37%, P < 0.01).Fewer Large White gilts remained unmated at 35 weeks of age than Landrace or Large White-Landrace synthetic breed gilts (7.7 and 14.1% of those selected, P < 0.001). More purebred gilts were prepubertal at 35 weeks of age than crossbred gilts (5.4 and 2.4%, P < 0.01).     

Ontogeny of Vision in Marine Crustaceans

Marine crustaceans present an extremely interesting set of examplesin which to examine visual development and metamorphosis. Larvaeof these animals are almost always planktonic, living in thelight field of open waters. The presence of a simple, predictablephotic environment, the relatively basic visual requirementsof larvae, and the need to remain transparent to reduce predationlead to the use of a single eye type throughout all marine crustaceanlarvae. Adult crustaceans, on the other hand, use a greaterdiversity of optical designs than all other animals combined,occupy habitats from the deep sea to mountaintops, and havevery complex visual systems and behaviors. Thus, visual developmentvaries tremendously among modern Crustacea. In this brief review,we consider the structure and development of marine crustaceaneyes, focusing on optics, retinal design, and metamorphosisof the visual pigments.     

Human relaxin increases cyclic AMP levels in cultured anterior pituitary cells

Although relaxin acts at several abdominal sites and mammary tissue associated with pregnancy and parturition, the scope of target tissues and the signals conveying the relaxin message into the cell are poorly defined. We found that human relaxin rapidly elevates the cyclic AMP content of cultured rat anterior pituitary cells. This is a graded response (EC50 0.3 nM relaxin) that can be blocked by anti-relaxin antibodies or the hormones somatostatin and dopamine. Furthermore, other hormones with some sequence homology to relaxin, such as insulin and insulin-like growth factor-I, have no such action. We conclude that the anterior pituitary may be a target tissue for relaxin and that cyclic AMP may act as an intracellular messenger for relaxin in these cells.     

Shrimps that pay attention: saccadic eye movements in stomatopod crustaceans

Discovering that a shrimp can flick its eyes over to a fish and follow up by tracking it or flicking back to observe something else implies a ‘primate-like’ awareness of the immediate environment that we do not normally associate with crustaceans. For several reasons, stomatopods (mantis shrimp) do not fit the general mould of their subphylum, and here we add saccadic, acquisitional eye movements to their repertoire of unusual visual capabilities. Optically, their apposition compound eyes contain an area of heightened acuity, in some ways similar to the fovea of vertebrate eyes. Using rapid eye movements of up to several hundred degrees per second, objects of interest are placed under the scrutiny of this area. While other arthropod species, including insects and spiders, are known to possess and use acute zones in similar saccadic gaze relocations, stomatopods are the only crustacean known with such abilities. Differences among species exist, generally reflecting both the eye size and lifestyle of the animal, with the larger-eyed more sedentary species producing slower saccades than the smaller-eyed, more active species. Possessing the ability to rapidly look at and assess objects is ecologically important for mantis shrimps, as their lifestyle is, by any standards, fast, furious and deadly.