The energetics of feeding strikes in larval carp, Cyprinus carpio

The prey intake of larval carp is described from high-speed (200–1250 frames s⁻¹) films with synchronous lateral and ventral views. Even in first-feeding carp larvae, the operculars are functional in sealing effectively the opercular slit until the moment of prey intake, and the maxillaries close off the corners of the mouth, preventing leak flow. In reducing the distance between larva and prey during attack, the relative importance of sucking the prey towards the mouth and swimming forward is variable; overall they are about equally important. The volume and the velocity of the water sucked into the mouth cavity during prey uptake are calculated. The energy costs of suction, i.e., accelerating the water sucked into the mouth cavity, during prey intake are estimated from these values. The energy costs of suction and swimming are in the same order of magnitude. Together they form only a fraction of 1% of the energetic content of the prey, so considerations about energy expenditure seem unimportant in a strategy to optimize the prey attack. During searching, however, they will be important. Power requirements during attack may also be important.     

Use of learned visual cues during habitat location by Brachymeria intermedia

Like many other parasitoids, Brachymeria intermedia (Hymenoptera: Chalcididae) uses olfactory cues to find its host, but in addition it appears to use learned visual cues to focus its searching efforts at the macrohabitat level. In laboratory experiments, females were held in cages where Lymantria dispar pupae were hidden either in a vertical, tree-like structure or on the floor. After four days females had learned to search for hosts in the structure in which they previously had found pupae. Such training was reversible. During similar tests in a semi-natural situation, in which pupae were hung from a tree trunk or were hidden under leaf litter, females also tailored their subsequent searching to favour the macrohabitat where hosts previously had been found. This parasitoid most likely uses a combination of visual and olfactory cues during host searching.     

Source of F series prostaglandins during the early postpartum period in cattle

In vivo and in vitro studies were conducted to determine the contribution of the bovine uterus to concentrations of 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM) in peripheral plasma of postpartum cows. In Experiment 1, cows were assigned to three groups: untreated control (n = 4), hysterectomy following a manually induced prolapse of the uterus (n = 5) and sham operation (n = 3: prolapse of the uterus and replacement). Surgery was performed within 8 h of parturition, and blood samples collected frequently on the day of surgery and once (0800 h) or twice (0800 and 1700 h) daily from Day 1 to Day 15 postpartum. Following hysterectomy, PGFM concentrations decreased precipitously, became essentially undetectable by 5 h, and remained so for the rest of the experimental period. In contrast (P less than 0.01), PGFM concentrations, which remained elevated during the day of surgery in the sham-operated group, peaked on Day 2 (sham-operated group: 1339 pg/ml) or Day 3 (untreated control: 2143 pg/ml), and declined to a basal concentration between Days 10 to 15. In Experiment 2, in vitro metabolism of tritiated arachidonic acid ([3H] AA: 10 microCi) and production of PGF2 alpha and PGFM were studied in explants of early postpartum intrauterine tissues (myometrium, caruncle and intercaruncular endometrium). Extracts of [3H] AA metabolites released into the incubation medium were separated on Sephadex LH-20 column chromatography. Metabolites of [3H] AA, having the same chromatographic mobility as PGF2 alpha, PGFM and PGE2, were detected.(ABSTRACT TRUNCATED AT 250 WORDS)