Postmolt Period Research Articles

Postmoult Uptake of Calcium by the Blue Crab (Callinectes Sapidus) in Water of Low Salinity

ABSTRACT After moulting, blue crabs (Callinectes sapidus) acclimated to a salinity of 2 ‰ were able to calcify as rapidly and accumulate as much calcium as crabs in sea water. Immediately after moult, the total masses of calcium, magnesium and strontium present in the whole body were 4.6, 15.6 and 3.0%, respectively, of their intermoult values. During the time of most rapid calcification, calcium uptake was 5.4±1.4mmol l−1, which is comparable to the maximum rate found in seawater-acclimated crabs. The concentrations of bound and free calcium in the blood changed very little with acclimation salinity, remaining at approximately 3 and 8 mmol l−1. respectively, both during intermoult and 1 day postmoult. Free calcium changed relatively little through the moult cycle, varying between 6.9 and 8.1 mmol l−1, but bound calcium rose to a peak of 6.4 mmol l−1 prior to moult then dropped to 2.6 mmol l−1 after moult, concurrent with a decrease of approximately 80% in the protein concentration of the blood. The concentration of total magnesium in the blood increased from a premoult low of 9.0 mmol l−1 to a postmoult high of 11.7 mmol l−1 and remained elevated throughout the period of rapid mineralization. During the postmoult period of rapid calcium uptake, the internal-to-external concentration ratio for total calcium was 6.6 to 1. The activity ratio, however, was only 2.5 to 1 because 28% of the calcium in the blood was bound to protein, and because the lower ionic strength of the medium resulted in a 2.5-fold higher activity coefficient for the water compared to blood. The transepithelial potential at postmoult (–5.4±0.7mV) was significantly more negative than at intermoult (–3.1±0.6mV). In artificial 2‰ sea water, the transepithelial potential (–9.3±0.7 mV) was higher than the equilibrium potential for calcium (–12.0±0.5 mV), implicating active transport in the uptake of calcium.

High affinity, Ca 2+ specific atpase and Na +K +-ATPase in the gills of a supralittoral crab Leptograpsus variegatus

1. 1. The gills of Leptograpsus variegatus contain a high-affinity, Ca 2+-activated ATPase, probably located in the basolateral plasma membrane of the gill epithelia. 2. 2. The affinity of the ATPase for Ca 2+ is in the micromolar concentration range (6–35 μmol/1). 3. 3. The specific activity of the enzyme did not change during the moult cycle. The ATPase probably does not contribute substantially to increased calcium influx from the medium during the post moult period. 4. 4. The enzyme is believed to function as a selective extrusion mechanism involved in the maintenance of a low cytosolic Ca 2+ level in the epithelial cells.

Aspects of the life-cycle of Loxothylacus panopaei (Gissler), a sacculinid parasite of the mud crab Rhithropanopeus harrisii (Gould): a laboratory study

The life cycle of Loxothylacus panopaei, a sacculinid barnacle parasite, has been investigated. At 20% salinity and 25°C larval broods are released every 5–6 days. The free-swimming larval phase involves four nauplius stages and a cypris stage. Development time to the cyprid is rapid -≈48 h. The lecithotrophic larvae occur in two forms - male and female, most easily distinguished at the cypris stage. Size frequency data of cyprids shows only slight overlap of the sexes, but the unequivocal distinguishing feature is the extra sac on the antennule of the male. Female cyprids settle on the megalopa larva, early crab stages and adults of the host Rhithropanopeus harrisii but only within the 24-h post-moult period. Female cyprids do not settle on the zoeal stages of the crab. Male cyprids settle only on virgin externae. R. harrisii is an estuarine mud crab so its larvae need to be retained in an estuary for successful recruitment. It is argued that L. panopaei larvae most probably use the same retention strategy of remaining at the depth of no net flow, although their salinity tolerance is somewhat more restrictive. The parasite interna phase is particularly rapid (25–27 days) and maturation of the externa is also rapid, the first larval brood being released 14–16 days following male inoculation.

Comparison of the Use of Dietary Aluminum with the Use of Feed Restriction for Force-Molting Laying Hens

Use of a high level of dietary aluminum was compared with a conventional feed restriction procedure for force-molting of Single Comb White Leghorn hens. Six replicate groups of 10 or 12 hens, 72 wk of age, housed 2 per cage, were randomly assigned to Treatments A and B, and 12 replicate groups were assigned to Treatment C. Hens in Treatments A and B were fed ad libitum a corn-soybean meal diet (15% CP, 3.5% Ca and .35% available P) containing .3% Al as aluminum sulfate. Hens in Treatment C were completely feed restricted for 10 days. Oyster shell was provided at 27 g/bird in Treatments B and C on the day before the start of the molting procedure. Water was provided ad libitum for all treatments. The effective photoperiod was reduced to 9 h. A diet containing 13% CP and 1% Ca was provided at 45 g/bird per day, starting 2 or 3 days following cessation of egg production and continuing until Day 28. On Day 29 the photoperiod was increased to 16 h, and hens were fed a layer diet.Egg production completely ceased by Day 7 for hens in Treatment C and almost ceased (3%) by Day 15 for hens in Treatments A and B. Body weight loss for hens in Treatment C was significantly greater than for aluminum-treated hens after 10 days. Feed intake of Al-fed hens averaged 43 g/hen per day. During a 14-wk postmolting period, no significant differences among treatments were observed in feed intake, egg production, and egg shell breaking strength. No differences among treatments were observed in plasma total calcium and inorganic phosphorus measured during the molting or the postmolting period. The results indicate that dietary aluminum can be used as a force-molting agent for laying hens.

Post-Moult Calcification in the Blue Crab, Callinectes Sapidus: Timing and Mechanism

ABSTRACT A series of experiments was conducted to elucidate the events immediately preceding and following moulting (ecdysis) in the blue crab, Callinectes sapidus Rathbun. The crabs gain weight (mostly water) to a level more than twice the premoult value excluding the shed carapace. The gain begins about 4 h before ecdysis, accelerates rapidly to a maximum rate at about the time of ecdysis, and is essentially complete by 2h after ecdysis. Both calcification and net H+ excretion remain at control (intermoult) levels until 1–2 h post-moult, whereupon a very rapid increase in both begins, with the same time course for both processes. The ratio of internal to external calcium concentration drops from 1·4:1 during intermoult to 0·85:1 by 2 days after the moult, reversing the electrochemical gradient during the post-moult period. Calcification is strongly inhibited by the protein synthesis inhibitors actinomycin D and cycloheximide. Isolated whole gills and gill slices do not show significant changes in rates of calcium uptake related to moult stage, indicating that the uptake of calcium across the gills may be largely passive. A low-affinity Ca2+-activated ATPase is present in both gills and epithelium, but only the epithelial activity shows a substantial (fivefold) increase in the hours after ecdysis. The control mechanisms for stimulation of the transport processes remain elusive. Eyestalkless crabs progress normally through moult and post-moult calcification. Peptide profiles from blood and from suspected neurohormone-producing tissues differ markedly with moult stage, but several different approaches to developing a bioassay using peptides from crab tissues and vertebrate sources have been unsuccessful. The physiological events in the hours surrounding ecdysis suggest a complex and precisely timed series of control signals.

Effect of Molting White Leghorn Hens on Egg Shell Pimpling and Shell Quality

Two experiments were conducted to evaluate the effect on eggshell pimpling of molting 85-wk-old White Leghorn hens. Experiment 1 used 120 hens. In Experiment 2, 25 hens consistently laying pimpled shell eggs (PS group) and 25 laying smooth shelled eggs (SS group) were selected. Both groups of hens were molted and observed for seven periods of 28 days and egg production and feed consumption determined pre and postmolt. Shell quality was evaluated for degree of shell pimpling [by scoring eggs from 1 (smooth) to 5 (very pimpled)] and for specific gravity, shell deformation, percentage shell, percentage shell membrane, and egg weight. In Experiment 1, pimple score declined from 3.7 premolt to 2.3 postmolt period one. By period seven, pimple score increased to 3.3. No clear trend was found for specific gravity, shell deformation, percentage shell, or percentage shell membrane. In Experiment 2, pimple scores for the PS group remained significantly higher than SS group scores and were at an unacceptable level (4.8 premolt and 3.6 postmolt).Samples of eggshell membranes from Experiment 2 were obtained either pre or postmolt and lyophilized for analysis of nitrogen and amino acids. Average percentage protein values were 82.8 and 84.1% for premolt and postmolt samples and 81.3 and 85.7% for PS and SS groups, respectively. No significant differences were found in protein percentages. No large differences were shown between amino acid compositions of shell membranes from pre and postmolt or PS and SS groups. The PS group membranes had significantly higher phenylalanine values than those of the SS group. Lysine values were higher postmolt than premolt.

Effect of constant temperatures on Theileria sergenti infection in salivary glands of nymphal Haemaphysalis longicornis.

The parthenogenetic Okayama strain of Haemaphysalis longicornis larvae which had engorged on cattle parasitaemic with the Fukushima stock of Theileria sergenti isolated in Japan were incubated at constant temperatures between 15 and 35°C during their pre-moult and post-moult periods. The Theileria infection rates in the salivary glands of the resultant nymphal ticks were assessed by staining with methyl green/pyronin stain. Constant temperatures of 15, 30 and 35°C were detrimental to the infection of salivary glands. The high infection levels were discernible in ticks incubated at 20 and 25°C. No maturation of T. sergenti was observed in salivary glands of ticks exposed to 35°C without the blood meal stimulus.

Changes in counts of haemocytes and in their physicochemical properties during the moult cycle in Porcellio spinicornis Say (Porcellionidae, Isopoda)

Total haemocyte counts in seventh and eighth growth-stage intermoult Porcellio spinicornis ranged, on average, from 3663.7 haemocytes/mm3 (61.70% hyalinocytes, 10.97% hemigranulocytes, and 27.31% granulocytes) in the male (mean wet weight = 0.051 g) to 4888.1 haemocytes/mm3 (58.36% hyalinocytes, 13.0% hemigranulocytes, and 28.63% granulocytes) in the female (mean wet weight = 0.054 g). Hyalinocyte count decreased by 59.75% following circumferential ecdysial split but gradually increased during anterior moult to peak at postecdysis. However, redox and surface potentials of hyalinocytes remained elevated during the moult (beginning with circumferential ecdysial split to anterior ecdysis). Granulocyte redox and surface potentials were high during the postmoult and intermoult periods, but were low during the moult. No significant changes in the hemigranulocyte and granulocyte counts were observed during the moult cycle. The significance of these findings is discussed.

Elaboration and ultrastructural changes in the pore canal system of the mineralized cuticle of Carcinus maenas during the moulting cycle

Two basic structural components are concerned in the elaboration of the pore canal system in the mineralized cuticle of the decapod crab Carcinus maenas: tubular cytoplasmic extensions originating from epidermis and vertical fibres. These components are present from the moment the first procuticular materials of the new cuticle are laid down but their organization varies according to a precise schedule during the further moult cycle stages. Cytoplasmic extensions form a complicated branching system connecting the epidermal layer with all regions of the cullcular compartment, at least transitorily. During the moult cycle the prolongation of this cellular system appears to result from two concomitant but opposite phenomena. Before ecdysis the growth of cell extensions in the proximal cuticular layers prevails over their regression at the distal level. During the post-moult period these phenomena are reversed in importance so that the pore canal system is without cytoplasmic material as soon as intermoult starts. The depositing of vertical fibres takes place in close contact with the proximal cell extension plasma membrane, which never bears dense plaques. As moult stages progress, they are gradually organized into twisted sheaths that persist throughout the intermoult. Incidentally, some fibres invade the pore canal lumen freed from cell extensions. Some aspects regarding the fine organization, the chemical composition and the functional significance of both epidermal tubular extensions or vertical fibres are also discussed in the light of previous investigations carried out on crustaceans and in other arthropods.

Changes in the fatty acid composition of the gill phospholipids in Gammarus duebeni during moult: evidence for reduced permeability of the gill membrane

1. 1. Following ecdysis there is a significant increase in the water flux across the body surface of the amphipod Gammarus duebeni. 2. 2. This flux declines over a period of 4–5 days coincident with the impregnation of the new cuticle. 3. 3. Gill lipid composition in the period 1–3 days after moult tends to be more uniform than that of intermoult controls. 4. 4. Also characteristically the gills from animals in this immediate post-moult period tend to have a lower level of polyunsaturated fatty acids than intermoult specimens. 5. 5. It is suggested that it may be advantageous to individuals exposed to the possibility of osmotic stress to undergo this change.

Gas Exchange, Acid-Base Balance, and the Oxygen Supply to the Tissues During a Molt of the Blue Crab Callinectes Sapidus

At temperatures compatible with molting the hemocyanin in the blood of an intermolt stage C blue crab transports all but a very small fraction of the oxygen consumed. A number of previous investigations suggest that the respiratory mechanisms permitting the oxygen carrier to function at such a high level during stage C are perturbed during a molt. Many of these suggestions prove to be correct. The uptake of water and the apparent decrease in net hemocyanin synthesis during stages D3 through A result in the virtual loss of the hemocyaninoxygen transport system. A pronounced premolt alkalosis compensates for a concomitant hypercapnia. During exuviation lactate frequently accumulates in the blood, which presumably results from the inadequacy of gas exchange and aerobic metabolism at this time. When the molt is successful, however, the blood becomes only slightly acidotic, if at all, and the acidosis rapidly disappears. The changes in net metabolism of hemocyanin do not entail shifts in the composition of functionally distinct subunits that might permit an adaptation of the oxygen transport system to altered operating conditions in the blood during the early postmolt. There is, however, an increase in oxygen permeability of the general body surface, which becomes a site of oxygen uptake from the medium directly into the metabolically activated epidermis and also into the blood. In animals that survive a molt, including groups exposed to moderately hypoxic as well as normoxic water, there is no sign of tissue hypoxia and total 02 uptake actually increases during the early postmolt. The critical role of these compensatory mechanisms is indicated by severe acidosis and tissue hypoxia prior to mortality in cases of aborted molts and molts that result in morphological aberrations. Later in the postmolt period the decrease in blood calcium that accompanies hardening of the new skeleton lowers hemocyanin-oxygen affinity, permitting the carrier to function at elevated blood PO2. In the decapod crustaceans the hemocyanin (Hc) in the blood is responsible for a very large fraction of the oxygen supplied to metabolizing tissue, especially at the high temperatures compatible with molting in temperate zone species. At least 80% and more commonly 90% of the oxygen consumed is transported to the tissues of a stage C animal in the form of HcO2 (reviewed by Mangum, 1983a). And yet numerous observations suggest that the mechanisms of gas exchange and transport are profoundly perturbed both during and immediately following a molt.

Effect of flightlessness during moult on the iron content in the pectoralis muscle of the Giant Canada Goose (Branta canadensis maxima)

Adult male Giant Canada Geese, collected from a nonmigratory wild population during their premoult, moult, and postmoult periods were studied for changes in the pectoralis muscle. A significant (p ≤ 0.0001) drop in the lean dry weight of the pectoralis muscle during the moult period when the birds were flightless was attributed to disuse atrophy. The concentration of iron in the pectoralis muscle increased significantly (p ≤ 0.0054) during the moult, but the total amount of iron in the muscle remained constant during the three periods. It was revealed that iron was not lost during disuse atrophy, but that it became more concentrated as muscle mass decreased. The diverse results reported in the literature need to be reevaluated in light of concurrent changes in muscle under different experimental conditions and also the different fiber type composition of the muscles studied.

Compensation of Hypercapnic Acidosis in the Aquatic Blue Crab, Callinectes Sapidus: The Predominance of External Sea Water Over Carapace Carbonate as the Proton Sink

ABSTRACT Radioactive labelling of the CaCO3 in the crab’s carapace was employed as a tool to study the contribution of the carapace carbonates to acute buffering of acid-base disturbances. Since Ca2+ uptake is extremely rapid during the post-moult period, crabs that moulted in the laboratory were incubated with 45Ca for 5 days immediately following the moult in order thoroughly to load the carapace carbonate pool with radiolabel. After a subsequent 2-week interval for feeding and completion of the post-moult carapace mineralization phase, these 45Ca-loaded crabs were subjected to a 24 h control period and a 24 h hypercapnic period (water equilibrated with 2% CO2 in air) to induce an internal acidosis. Compared with the control period, a compensatory increase in [HCO3−] of 17 mequivl−1 was observed in the blood, along with an apparent H+ excretion to the external sea water of 10-8 mequivkg−1. A statistically significant increase in circulating [Ca2+] and in the specific radioactivity of the blood Ca2+ reached a maximum during the first 3 h of the compensatory phase. By measuring the radioactivity appearing in the water and the blood, and the specific radioactivity of the carapace carbonates, the contribution of the carapace carbonates was calculated to be 7·5% of the total compensatory H+ disposal. The rapid exchange of Ca2+ with the external medium, coupled with physiological regulation of blood [Ca2+] minimized changes in blood [Ca2+]. The total dissolution of carapace CaCO3 was approximately 0·9 mequivkg−1, less than 0·1% of the quantity contained in the shell. The carapace carbonates, therefore, do contribute to acute buffering of hypercapnic acidosis, but their quantitative importance is small, with the gills serving to conduct most of the compensatory exchanges with the environment.

Chronology of the Female Molt Cycle in Siriella Armata M. Edw. (Crustacea: Mysidacea) Based on Marsupial Development

ABSTRACT An alternative method for staging molt cycles is proposed for adult females of the mysid Siriella armata. Cultured females have a 12-day molt and breeding cycle. At the end of each cycle, liberation of the young, ecdysis of the female, copulation, and egg laying occur successively in less than 8 h. A synchronization between marsupial development, secondary ovarian vitellogenesis, and the integumental cycle is observed. Marsupial development is described and its chronology is related to molt cycle staging. Molt stages are defined following Drach's method complemented by an ultrastructural study of the evolution of the integument. The corresponding 12-day cycle of oocyte development in the ovary is described. Embryonic development corresponds to the female postmolt period. The nauplioid phase matches the intermolt period and the postnauplioid phase is simultaneous with the premolt period. Siriella armata is suggested as a suitable experimental organism for studies of the control of molt and reproductive cycle in mysids.

A Comparison of the Effect of Two Force Molting Methods on Performance of Two Commercial Strains of Laying Hens

A low-sodium diet (.08% Na) was used to force molt 409 hens. Another 421 hens were force molted by conventional water and feed restrictions. Birds were 68 weeks of age at that time, and two strains were about equally represented in each treatment group. These strains were: A, DeKalb; and B, Hisex. The low-sodium diet and water were provided ad libitum to the first group for the entire period of molt (42 days). The second group received no water for 3 days, and no feed for 4 days, after which incremental amounts of whole oats were provided as the only feed until Day 18. After Day 18, incremental amounts of a regular laying mash and decremental amounts of whole oats were provided through Day 26, when laying mash only was given ad libitum. Both treatment groups were in the same building and received the same lighting program during the force-molt period. This program consisted of: Days 1 to 3, no light; Days 4 to 18, 8 hr/day; Days 19 to 25, 9 hr/day; Day 26, 10 hr; then, light was increased 30 min weekly until 14 hr daily was attained. The low-sodium group ceased laying after 28 to 31 days, lost 8.7% of their premolt body weight, reduced feed consumption by 35%, and decreased egg production from 62.3% (in the 28 days preceding the molt) to 19% in the 42 days of molt; their mortality rate was 3.4%. The feed- and water-restricted group receiving oats ceased laying after 11 to 12 days, lost 17% of their premolt body weight, reduced feed consumption by 81%, and decreased egg production from 59.3% (in the 28 days preceding the molt) to 4.0% in the 42 days of molt; their mortality rate was 5%. Nearly all of the birds assigned to the feed and water restriction lost their feathers during the first 2 weeks; in contrast, hens receiving the low-sodium treatment lost their feathers at a much slower rate. No significant differences were observed between the two treatment groups in egg production, egg weight, interior egg quality, or shell quality during 10 subsequent, 28-day postmolt periods.Strain B stopped laying earlier and had a higher mortality rate than Strain A during the force-molt period. However, Strain B had a significantly higher (P<.05) egg production rate during the postmolt period of 280 days.

Feed Restriction During the Growing Period, Forced Molt, and Egg Production

An experiment was conducted to examine postmolt laying performance of White Leghorn hens that had been subjected to feed restriction from 8 to 20 weeks of age.During the postmolt period, birds in all forced-molt (FM) groups consistently had higher percent hen-day egg production than the control birds. Within the FM groups, birds that had previously been restricted fed during the growing period at the rate of 70% of the control group's consumption (R70 -FM) consistently had higher percent hen-day egg production during most of the postmolt period than the nonrestricted fed birds (Ad lib.-FM). Significant (P<.05) improvements in albumen height and shell thickness were observed 4 weeks after the FM period. When premolt, molt, and postmolt periods were combined, R70-FM birds had the highest percent henday egg production and the best feed efficiency of any group.

Influence of Premolt Production on Postmolt Performance with Explanation for Improvement in Egg Production Due to Force Molting

Performance of force-molted hens as influenced by premolt production was determined in two experiments using 720 Babcock hens. Hens selected to be laying at a low (41%), average (59%), and high (75%) rate of production were divided into two groups. One half of the hens were force molted (FM) and the other half served as controls (CON). On completion of the fasting period, blood was collected for chemical analyses from 10 hens per group. These hens were then necropsied and weights of the ovary, oviduct, liver, and fat pad determined. During the last 4 weeks of the postmolt period, dietary calcium was increased from 3.5 to 4.5% in half of each group.Postmolt production was directly related to premolt production. The hens laying the highest rate premolt showed no improvement, whereas those laying at the lowest rate showed the greatest improvement. The FM hens exhibited a lower incidence of shell-less eggs than CON hens. Premolt production appeared to have little influence on postmolt egg weight, organ weights, and blood constituents. However, shell weight and egg specific gravity were significantly improved by force molting. Increasing dietary calcium had no significant influence on shell weight and specific gravity in FM hens in either experiment but significantly increased specific gravity and shell weight of CON hens during Experiment 2.It was concluded that most of the improvement in production in force-molted hens was caused by a reduction in shell-less eggs and not by an increase in ovulation. Also, only a portion of the improvement in shell quality could be explained by an increase in feed intake (calcium intake) after molting due to the increase in production. An improvement in calcium metabolism was postulated to be a major cause of improved shell quality.

Effects of Forced Molt Period on Postmolt Performance of Leghorn Hens

Sixty-four-week-old Single Comb White Leghorn (SCWL) hens were subjected to the following treatments: 1) no forced molt (control); 2) forced molt for 4 weeks (FM4); 3) forced molt for 6 weeks (FM6): and 4) forced molt for 8 weeks (FM8). Molt was induced by restricting feed, water, and photoperiod. Data were analyzed at the 5% level of probability.During the early postmolt period (72 to 76 weeks of age), birds in all FM groups consumed significantly more feed and had significantly higher hen-day egg production than birds in the control group. Albumen height and shell thickness measured at 76 weeks of age were significantly improved by all FM treatments.During the postmolt period (72 to 124 weeks of age), hens in the FM8 group had the highest hen-day egg production and best feed efficiency, whereas birds in the control group had the lowest hen-day egg production and poorest feed efficiency. However, these differences were not statistically significant. Percent hen-day egg production was positively and significantly correlated with FM period. Mortality rate during this period was significantly lower for the FM4 and for the FM8 groups as compared to the control group. Egg shell thickness was significantly improved in two out of the three FM treatments.

Predatory success in the water stick insect: The role of visual and mechanical stimulations after moulting

The more foreleg femur and claw movements that a water stick insect, Ranatra linearis, performs during the 4-h period following a moult, the higher will be its subsequent strike efficiency. The amount of movement is influenced by external factors such as the presence of prey or light. The experiments reported here show that the absence of visual cues during the post-moult periods impairs subsequent performance, but not as much as the absence of both visual and mechanical cues. Perception of mechanical stimuli only during that period subsequently influences the accuracy of simple type strikes elicited when prey is near the forelegs; whereas perception of visual stimuli subsequently improves the accuracy of more complex predatory movements.

Epidemiology of East Coast fever: some effects of temperature on the development of Theileria parva in the tick vector, Rhipicephalus appendiculatus.

The moulting behaviour of nymphal Rhipicephalus appendiculatus from the laboratory colony and 3 field strains from Kenya was greatly influenced by constant temperatures between 18 and 37 degrees C but was not significantly different for the 4 tick strains. Six batches of R. appendiculatus (Muguga laboratory) nymphs which had engorged on cattle parasitaemic with 4 stocks of Theileria parva (Kiambu 4, Kiambu 5, Muguga and Mbita 4) isolated in Kenya were incubated at constant temperatures between 18 and 37 degrees C during their pre-moult and post-moult periods. The Theileria infections in the salivary glands of the resultant adult ticks were assessed by staining with Feulgen's stain. Two stocks (Muguga and Kiambu 5) developed their highest infections in ticks incubated at 28 degrees C while the other two (Kiambu 4 and Mbita 4) developed their highest infections at 23 degrees C. Constant temperatures of 18, 33 and 37 degrees were detrimental to the development of salivary gland infections. Temperature influenced the rate of development and numbers of the earlier Theileria stages in the ticks. Engorged nymphal ticks incubated for 4 days at 37 degrees C during their pre-moult period developed lower infections than ticks exposed at 4 degrees C for 4 days.