Life history of an unusual marine fish: survival, growth and movement patterns of Hippocampus guttulatus Cuvier 1829

The life history of the long‐snouted seahorse Hippocampus guttulatus was characterized using mark‐recapture data collected within a focal study site and catch data from 53 additional sites in the Ria Formosa coastal lagoon, southern Portugal. Population structure in benthic habitats was characterized by high local densities (0·3–1·5 m^?2), equal sex ratios and few juveniles <70 mm. Adult H. guttulatus maintained small (19·9 ± 12·4 m²), strongly overlapping home ranges during multiple reproductive seasons. Recruited (benthic) juveniles exhibited significantly lower site fidelity than adults. A Ford‐Walford plot of standard length (L_S) at time t against L_S measured during the previous year from tagged juveniles and adults led to estimates of the von Bertalanffy parameters K = 0·571 and L_∞ = 197·6 mm. The growth rate of planktonic juveniles (inferred from previous studies), was greater than predicted by the von Bertalanffy model, providing evidence of an ontogenetic shift in growth trajectory. The instantaneous rate of natural mortality, M, ranged from 1·13 to 1·22 year^?1(annual survival rate = 29·4–32·2%). Sexes did not differ in movement, growth or survival patterns. On average, H. guttulatus measured 12·2 ± 0·8 mm at birth. Planktonic juveniles recruited to vegetated habitat at 96·0 ± 8·0 mm (0·25 years), had mature brood pouches (males only) at 109·4 mm (0·49 years), began maintaining home ranges and reproducing at 125–129 mm (0·85–0·94 years), and lived for 4·3–5·5 years. Early age at maturity, rapid growth rates, and short generation times suggested that H. guttulatus may recover rapidly when direct (e.g. exploitation) and indirect (e.g. by‐catch and habitat damage) effects of disturbance cease, but may be vulnerable to extended periods of poor recruitment.     

The effect of body size on food consumption, absorption efficiency, respiration, and ammonia excretion by the inland silverside, Menidia beryllina (Cope) (Osteichthyes: Atherinidae)

The inland silverside, Menidia beryllina (Cope), is an annual zooplanktivore that occurs in estuarine and freshwater habitats along the Atlantic and Gulf of Mexico coasts and drainages of the United States. Experiments were conducted at 25 ± 1°C to quantify the relationship between mean dry weight (W_D) and rates of energy gain from food consumption (C), and energy losses as a result of respiration (R) and ammonia excretion (E) during routine activity and feeding by groups of fish. The absorption efficiency of ingested food energy (A) was also quantified. Rates of C, E, and R increased with W_D by factors (b in the equation y = aW_D^b) equal to 0.462, 0.667, and 0.784, respectively. Mean (±SE) rates of energy loss during feeding were 1.6 ± 0.1 (R) and 3.4 ± 0.6 (E) times greater than those for unfed fish. Absorption efficiency was independent of W_D and estimated to be 89% of C. From these measurements, the surplus energy available for growth and activity (G) and growth efficiency (K₁) were estimated. Over the range in sizes of juveniles and adults (5–500 mg W_D), predicted G and K₁ values decreased from 7.42 to 0.20 J mg fish^?1 day^?1 and 63 to 21%, respectively. Measured and predicted bioenergetic parameters are discussed within an ecological context for a northern population of this species.     

Some effects of freezing temperatures on overwintering larvae of the large elm bark beetle (Scolytus scolytus)

Overwintering final instar larvae of Scolytus scolytus were tested for coldhardiness by exposure to a range of sub-zero temperatures (–7°Cto –31 °C) in a frost-gradient apparatus for 7 days. The Lt₅₀ for larvae removed from the bark (– 20.5 °C) was significantly different (P < 0.01) from the Lt50 (–18.3 °C) for larvae insulated by the bark (thickness of 7 mm ± 2 mm). Larvae with food in their digestive tract were more susceptible to freezing than the overwintering final instars which had voided their stomach contents. Duration and intensity of cold did not cause any adverse long-term effects. Most of the larvae which survived the sub-zero treatments were able to pupate or reach the adult stage. The mean supercooling point of the overwintering larvae (–30.85 °C) confirmed their cold-hardiness.     

Effect of developmental stage on bovine oocyte plasma membrane water and cryoprotectant permeability characteristics

Knowledge of bovine oocyte plasma membrane permeability characteristics at different developmental stages in the presence of cryoprotective agents (CPAs) is limited. The objective of this study was to determine the oolema hydraulic conductivity (L_p), cryoprotectant permeability (P_CPA), and reflection coefficient (σ) for immature (germinal vesicle stage, GV) and in vitro–matured (metaphase II, MII) bovine oocytes. Two commonly used cryoprotective agents, dimethyl sulfoxide (DMSO) and ethylene glycol (EG), were studied. Osmometric studies were performed using a micromanipulator connected to an inverted microscope at 22 ± 2°C. Each oocyte was immobilized via a holding pipette, and osmotically induced volume changes over time (dv/dt) were recorded. The L_p values for GV and MII oocytes in DMSO (L_p^DMSO) were 0.70 ± 0.06 and 1.14 ± 0.07 μm/min/atm (mean ± SEM) and in EG (L_p^EG) were 0.50 ± 0.06 and 0.83 ± 0.07 μm/min/atm, respectively. Estimates of P_DMSO for GV and MII oocytes were 0.36 ± 0.03 and 0.48 ± 0.03 μm/sec, and P_EG values for GV and MII oocytes were 0.22 ± 0.03, 0.37 ± 0.03 μm/sec, respectively. The σ values for GV and MII oocytes in DMSO (σ_DMSO) were 0.86 ± 0.03 and 0.90 ± 0.04 and in EG (σ_EG) were 0.94 ± 0.03 and 0.76 ± 0.04, respectively. These data demonstrate that bovine oolema permeability coefficients to water and cryoprotectants change after in vitro maturation. Furthermore, the bovine oocyte P_DMSO is higher than the P_EG. These results may provide a biophysical basis for developing criteria for choosing optimal CPAs and for minimizing damage during addition and removal of the CPAs. Additionally, these data support the hypothesis that different procedures may be required for optimal cryopreservation of different oocyte developmental stages. Mol. Reprod. Dev. 49:408–415, 1998. © 1998 Wiley-Liss, Inc.     

Embryo development,oocyte morphology,and kinetics of meiotic maturation in bovine oocytes exposed to 6-dimethylaminopurine prior to in vitro maturation

The developmental competence of bovine follicular oocytes that had been meiotically arrested with the phosphokinase inhibitor 6-dimethylaminopurine (6-DMAP) was studied. After 24 h in vitro culture with 2 mM 6-DMAP, 85 ± 12% of the oocytes were at the germinal vesicle stage compared to 97 ± 3% at the start of culture (P > 0.05). After release of the 6-DMAP inhibition, followed by 24 h IVM, 82 ± 18% were at MII stage, compared with 93 ± 7% in the control group (P > 0.05). The 6-DMAP oocytes displayed a much higher frequency of abnormal MII configurations than the control oocytes (67% vs 23%; P < 0.0001). In addition spontaneous oocyte activation was more frequent than among control oocytes (5% vs 0.3%; P 0.0006). After IVF of 6-DMAP oocytes, normal fertilization was lower (76 ± 8% vs 89 ± 7%; P < 0.01), oocyte activation higher (11 ± 5% vs 2 ± 2%; P < 0.01), and polyspermy slightly but not significantly higher (8 ± 7% vs 4 ± 4%; P > 0.05), compared with the control group. Cleavage was lower (61 ± 13% vs 81 ± 6%; P < 0.001), as well as day 8 blastocyst formation (17 ± 7% vs 36 ± 8%; P < 0.001). The MII kinetics was different for 6-DMAP and control oocytes. Maximum MII levels were reached at 22 h IVM in both groups, but 50% MII was reached at 17 h in 6-DMAP oocytes, compared to 20 h in control oocytes. Ultrastructure of MII oocytes was similar in the two groups, but in 6-DMAP oocytes the ooplasmic vesicle pattern at GV was at a more advanced stage than in control oocytes. In conclusion, 6-DMAP exposure of GV oocytes prior to IVM induce asynchronous cytoplasmic maturation, leading to aberrant MII kinetics. Thus, at the time of insemination a smaller cohort of oocytes will be at the optimal stage for normal fertilization and subsequent blastocyst development. Mol. Reprod. Dev. 50:334–344, 1998. © 1998 Wiley-Liss, Inc.     

Variables affecting the yield and developmental potential of embryos following superstimulation and in vitro fertilization in rhesus monkeys

Three follicular-stimulation protocols were compared to evaluate the yield and quality of oocytes obtained from rhesus monkeys. Five animals received a high-dose regimen of PMSG (protocol I), three received a lower-dose regimen (protocol II), and two received Clomid-Pergonal (protocol III). Oocytes were recovered at laparoscopy after HCG injection, fertilized in vitro, and cultured up to the blastocyst stage. Yields of mature oocytes were 17.2 ± 13.0 (80% of total recovered), 6.7 ± 6.6 (41%), and 4.5 ± 2.5 (90%) per stimulated cycle for protocols I, II, and III, respectively. Of mature oocytes, 72%, 45%, and 89% were fertilized for protocols I, II and III, respectively. Protocol I produced the most fertilized oocytes per stimulated cycle (11.6 ± 11.6) and the greatest E₂ production (approximately fourfold that maximally expected for an unstimulated cycle). For the combined protocol I and II results, there was a significant correlation (P ? 0.05) between mean embryo development score and E₂ production. Fertilized oocytes from protocol I yielded 7.8 ± 8.0 morulae and 6.8 ± 7.2 early zonal blastocysts per cycle. After transfer of nine singleton embryos to surrogate recipients, one live birth resulted. We conclude that our high-dose PMSG regimen offers the best means at present for obtaining susbstantial numbers of developmentally competent oocytes in rhesus monkeys and that more extensive use of rapid serum E₂ assays for monitoring both stimulated cycles and those of potential surrogate recipients could help to predict the success of in vitro fertilization and embryonic development following embryo transfer in rhesus monkeys.     

Effect of circulatory congestion on the components of pulmonary diffusing capacity in morbid obesity

Objective: Obese patients without clinically apparent heart disease may have a high output state and elevated total and central blood volumes. Central circulatory congestion should result in elevated pulmonary diffusing capacity (D_LCO) and capillary blood volume (V_c) reflecting pulmonary capillary recruitment; however, the effect on membrane diffusion (D_m) is uncertain. We examined D_LCO and its partition into V_c and D_m in 13 severely obese subjects (BMI = 51 ± 14 kg/m²) without manifest cardiopulmonary disease before and after surgically induced weight loss. Research Methods and Procedures: D_LCO and its partition into V_c and D_m [referenced to alveolar volume (V_A)] as described by Roughton and Forster, total body water by tritiated water, and fat distribution by waist‐to‐hip ratio were performed. Results: Despite normal D_LCO (mean 98 ± 16% predicted), V_c/V_A was increased (mean 118 ± 30% predicted), and D_m/V_A was reduced (mean 77 ± 34% predicted). Nine of 13 subjects were restudied after weight loss (mean 52 ± 43 kg); V_c/V_A decreased to 89 ± 18% predicted (p = 0.01), and D_m/V_A increased to 139 ± 30% predicted (p < 0.01). Increasing total body water was associated with both increasing V_c (r = 0.74, p = 0.01) and increasing waist‐to‐hip ratio (r = 0.65, p = 0.02), indicating that circulatory congestion increases with increasing central obesity. Discussion: Severely obese subjects without manifest cardiopulmonary disease may have increased V_c indicating central circulatory congestion and reduced D_m suggesting associated alveolar capillary leak, despite normal D_LCO. Reversibility with weight loss is in accord with reversibility of the hemodynamic abnormalities of obesity.     

The reproductive cycle of female Ballan wrasse Labrus bergylta in high latitude,temperate waters

This 2 year study examined the reproductive cycle of wild female Ballan wrasse Labrus bergylta in western Norway as a precursor to captive breeding trials. Light microscopy of ovarian histology was used to stage gonad maturity and enzyme‐linked immuno‐absorbent assay (ELISA) to measure plasma concentrations of the sex steroids testosterone (T) and 17β‐oestradiol (E₂). Ovarian recrudescence began in late autumn to early winter with the growth of previtellogenic oocytes and the formation of cortical alveoli. Vitellogenic oocytes developed from January to June and ovaries containing postovulatory follicles (POF) were present between May and June. These POF occurred simultaneously among other late maturity stage oocytes. Plasma steroid concentration and organo‐somatic indices increased over winter and spring. Maximal (mean ±s.e .) values of plasma T (0·95 ± 0·26 ng ml^?1), E₂ (1·75 ± 0·43 ng ml^?1) and gonado‐somatic index (I_G; 10·71 ± 0·81) occurred in April and May and decreased greatly in July when only postspawned fish with atretic ovaries occurred. Evidence indicates that L. bergylta are group‐synchronous multiple spawners with spawning occurring in spring and peaking in May. A short resting period may occur between late summer and autumn when previtellogenic oocytes predominate and steroid levels are minimal.     

Ontogenetic development of the digestive tract in Cuban gar (Atractosteus tristoechus) larvae

Histological method was used to describe the development of the digestive tract in Atractosteus tristoechus larvae reared under culture conditions. The larvae were kept at 28 ± 1 °C in three 15 L circular tanks for 18 days and they were fed with Artemia. According to the structural changes in the digestive system, three significant stages were established: (1) lecithotrophic, (2) lecithoexotrophic and (3) exotrophic. The first stage spanned from hatching to 3 days after hatching (DAH), the digestive system started to differentiate and larvae depended entirely on the endogenous nutrition from the yolk sac. During second stage (4–10 DAH), considered critical since it is the transition period to exotrophic feeding, the digestive tract was fully differentiated into buccopharynx, esophagus, non-glandular and glandular stomach, anterior and posterior intestine. First periodic Schiff reagent-positive goblet cells also appeared, interdispersed within the epithelium of the digestive tract, increasing substantially in numbers and distribution as development continued. At this early stage, gastric glands were only observed in the fundic stomach and not in the cardiac and pyloric region. Pyloric caeca, spiral valve and rectum were also clearly distinguishable in the intestine. After the onset of the exogenous feeding (11–18 DAH), the organization and differentiation of the digestive tract did not undergo any noticeable modification, only the increase in size and complexity of the structures, and it attained the four tissue layer arrangement characteristic of adult vertebrates.     

Changes in lipid and protein during starvation and the moulting cycle in the tiger prawn, Penaeus esculentus Haswell

Tiger prawns, Penaeus esculentus Haswell (mean wt 20.8 ± 0.3 g, range 13.9–27.7 g) contained 1–2% extractable lipid, 13% protein (biuret method) and 71–74% water (wet wt). In 21 days, the weight of fed prawns increased by 3% and that of starved prawns decreased by 4.4%. Protein was the major energy source during 14 days of starvation, with a loss of 550 mg of total protein compared with a loss of 84 mg of total lipid. The absolute amount of water present remained constant. Of three different tissue compartments, abdomen, cephalothorax, and digestive gland, the abdomen contributed the most protein (330 mg) and lipid (35 mg) during 14 days of starvation. Digestive gland, although containing the largest percentage wet wt of lipid, accounted for only 8.3% of the total lipid in the prawn, and contributed only 18 mg of lipid in 14 days of starvation. Lipid concentration in the digestive gland increased during early premoult (stage D₄) and dropped in late premoult (stage D₄). Resting oxygen consumption rate remained constant at ≈0.1 ml · g^?1 · h^?1 at 25°C during 21 days of starvation.     

Gonads of males and females of the mangrove tree crab Aratus pisonii (Grapsidae: Brachyura: Decapoda): a histological and histochemical view

Nicolau, C.F., Nascimento, A.A., Machado‐Santos, C., Sales, A. and Oshiro, L.M.Y. 2011. Gonads of males and females of the mangrove tree crab Aratus pisonii (Grapsidae: Brachyura: Decapoda): a histological and histochemical view. —Acta Zoologica (Stockholm) 00 :1–9. This study describes the microscopic anatomy of the male and female gonads and the spermatogenesis and oogenesis of the mangrove tree crab Aratus pisonii. Males and females were captured in a mangrove marsh in Guaratiba (23°04′S, 44°10′W), Rio de Janeiro State, Brazil. The testes are composed of spermatogonia I (7.82 ± 0.84 μm), spermatogonia II (6.12 ± 0.72 μm), spermatocytes I (5.62 ± 0.71 μm), spermatocytes II (5.00 ± 0.42 μm), spermatids (4.01 ± 0.33 μm), and spermatozoa (2.58 ± 0.18 μm). The spermatozoids are sent to the vas deferens, which is divided into three regions: anterior vas deferens, middle vas deferens and posterior vas deferens. There are no indications of development as the production of male gametes was continuous throughout the study period. In the females, there are four ovary development stages: previtellogenesis, early‐stage vitellogenesis, mature vitellogenesis, and postspawning. Five types of cells were found in the gonads: oogonia (5.23 ± 1.31 μm), oocytes in early development (19.84 ± 5.16 μm), previtellogenic oocytes (49.49 ± 6.87 μm), vitellogenic oocytes (87.51 ± 10.23 μm), and mature oocytes (174.78 ± 29.46 μm). The findings of this study indicate that A. pisonii females lay eggs on multiple occasions throughout the study period.     

Physical changes in specimens of five species of Cyprinidae preserved in ethanol and frozen

Preservation in 30% ethanol and freezing to a temperature of ?20 ± 2° C is an appropriate method for measurement of fish eggs, larvae and juveniles. Egg diameter of the common carp Cyprinus carpio increased insignificantly by 1·32% after preservation compared with live size. The total length (L_T) of 1 day post‐hatching (dph) larvae as well as the standard length (LS) of 16 dph larvae of C. carpio increased significantly (2·95 and 1·50%, respectively) after preservation. Egg diameter as well as the L_T of 1 dph larvae of barbel Barbus barbus increased significantly after preservation, by 1·74 and 1·96%, respectively over their original size. The standard length (L_S) of 14 dph larvae of B. barbus as well as juveniles of B. barbus, crucian carp Carassius carassius, common nase Chondrostoma nasus and tench Tinca tinca decreased significantly after preservation (?0·56 to ?5·54%), whereas their body mass increased significantly (11·46–18·57%). Preserved eggs of C. carpio and B. barbus were hard, round and transparent. The larvae and juveniles of examined fishes, preserved in frozen ethanol, were straight, flexible and easily measurable after 60 days. Integrity of body surface and fins, as well as preservation of colours were much better in larvae or juveniles frozen and thawed only once than in specimens frozen and thawed thrice. Cooling in 30% ethanol to a temperature of 6 ± 2° C and freezing in water to a temperature of ?20 ± 2° C are not appropriate preservation methods for eggs and larvae of C. carpio (1 and 16 dph).     

The use of a non‐invasive tool for capture–recapture studies on a seahorse Hippocampus guttulatus population

In this study, the spot pattern in Hippocampus guttulatus was analysed using a computer programme algorithm that allowed individual comparison. This methodology was first tested in a controlled environment using 51 adult and 55 juvenile H. guttulatus. Positive matches were obtained in 86·3 and 83·6% of the adults and juveniles, respectively. In a second experiment, monthly surveys were carried out in five selected locations in the Ria Formosa Lagoon, south Portugal, over the course of a year and a total of 980 photographs were analysed. Photographed H. guttulatus were re‐sighted one to nine times during the course of the survey period with an overall re‐sight record of over 30%. Photo‐identification was therefore shown to be a useful tool for non‐invasive mark–recapture studies that can be successfully used to survey the population abundance of H. guttulatus aged 6 months or older in consecutive years. This could be of great value when considering the assessment of H. guttulatus populations and understanding changes over time.     

Segmental flexibility in pig immunoglobulin G studied by neutron spin-echo technique

The dynamic behavior of pig immunoglobulin G in deuterium oxide solutions was investigated by the neutron spin-echo technique. This novel technique makes it possible to study intramolecular motion without introducing probes into the macromolecule. Using neutron spin-echo, the effective diffusion coefficient, D_eff, was obtained as a function of the transferred momentum, κ. For interpretation of the experimental data, two models were designed, and computed D_eff values were compared with experimental data. The rigid T-shape model was compatible with the experimental data only by assuming an unrealistically high rotational diffusion coefficient, and it was therefore unacceptable. Reasonable agreement with all available experimental data was obtained with a flexible model of immunoglobulin G molecule, which the Fab arms are assumed to wobble around the hinge region within an angle of 50°.     

Differential distribution of endothelin peptides and receptors in human adrenal gland

Summary Sub-type selective ligands revealed a differential distribution of endothelin (ET) receptors within human adrenal glands. High densities of ET_A receptors were localized, using [¹²⁵I]-PD151242, to the smooth muscle layer of the arteries, smaller vessels within the capsular plexus and to the secretory cells of zona glomerulosa (K _D=139.8±39.7,B _max=69.7±9.1 fmol mg⁻¹ protein, mean of 3 individuals±sem). ET_B receptors were present in the medulla (K _D=145.2±16.4,B _max=75.5±12.3), zona glomerulosa (K_D=100.6±35.1,B _max=63.1±10.0), fasiculata (K _D 145.1±162.,B _max=67.9±6.9) and reticularis (K_D=118.2±18.6,B _max=71.9±6.5). ET_B receptors were not detected within the smooth muscle of the vasculature. Messenger RNA encoding both sub-types was present in adrenals. ET-like immunoreactivity was localized to the cytoplasm of the endothelial cells from arteries supplying the gland and resistance vessels within the capsular plexus. Staining was also detected in these cells using anti-big ET-1 and less intensely with anti-big ET-2 antisera but not within cells within the cortex or medulla. Big ET-3-like immunoreactivity was localized to secretory cells of the medulla. Staining was not found using antiserum that could detect ET-3, suggesting further processing of big ET-3 may occur within the plasma, and that the cdrenals could be a source of ET-3. The presence of ET-1 was confirmed by high performance liquid chromatography and radioimmunoassay although ET-3 was not detected. The results suggest that ET-1 is the predominant mature isoform, which is localized mainly to adrenal vasculature, particularly the capsular plexus, and may contribute to blood flow regulation in the gland.     

Good Cascade Impactor Practice (GCIP) and Considerations for “In-Use” Specifications

The multi-stage cascade impactor (CI) is widely used to determine aerodynamic particle size distributions (APSDs) of orally inhaled products. Its size-fractionating capability depends primarily on the size of nozzles of each stage. Good Cascade Impactor Practice (GCIP) requires that these critical dimensions are linked to the accuracy of the APSD measurement based on the aerodynamic diameter size scale. Effective diameter (D _eff) is the critical dimension describing any nozzle array, as it is directly related to stage cut-point size (d ₅₀). d ₅₀ can in turn be determined by calibration using particles of known aerodynamic diameter, providing traceability to the international length standard. Movements in D _eff within manufacturer tolerances for compendial CIs result in the worst case in shifts in d ₅₀ of <±10%. Stage mensuration therefore provides satisfactory control of measurement accuracy. The accurate relationship of D _eff to d ₅₀ requires the CI system to be leak-free, which can be checked by sealing the apparatus at the entry to the induction port and isolating it from the vacuum source and measuring the rate of pressure rise before each use. Mensuration takes place on an infrequent basis compared with the typical interval between individual APSD determinations. Measurement of stage flow resistance (pressure drop; ΔP _stage) could enable the user to know that the CI stages are fit for use before every APSD measurement, by yielding an accurate measure of D _eff. However, more data are needed to assess the effects of wear and blockage before this approach can be advocated as part of GCIP.     

Standard metabolism and growth dynamics of laboratory‐reared larvae of Sardina pilchardus

This study provides the first measurements of the standard respiration rate (R_S) and growth dynamics of European sardine Sardina pilchardus larvae reared in the laboratory. At 15° C, the relationship between R_S (µl O₂ individual^?1 h^?1) and larval dry mass (M_D, µg) was equal to: R_S = 0·0057(±0·0007, ± s.e.)·M_D^{0·8835(±0·0268)}, (8–11% M_D day^?1). Interindividual differences in R_S were not related to interindividual differences in growth rate or somatic (Fulton's condition factor) or biochemical‐based condition (RNA:DNA).     

A novel method to determine the diffusional water permeability of oocyte plasma membranes

Measurements of the cell membrane diffusional water permeability (P_d) are important to characterize water passage across water channels and across the lipid bilayer component of the membrane. Existing methods for those measurements are involved; however, we report here a simple procedure to estimate P_d in Xenopus laevis oocytes and similar large cells. Due to the different densities of H₂O and D₂O (heavy water), an oocyte transferred from normal medium to a D₂O-based medium floats initially, but subsequently sinks when a certain amount of the water originally in them is replaced by the D₂O that diffuses in. We describe how the ‘flotation time’ (time that oocytes float in a heavy water solution before they start sinking) yields the P_d of the plasma membrane. Determination of P_d by this procedure and by the rate of tritiated water (T₂O) efflux give for P_d results which are very close: 2.2 ± 0.2 (n = 8) and 2.0 ± 0.1 (n = 6) μm/s, respectively (T = 10°C). Further-more, our method detects the increase in P_d elicited in oocytes by either expression of water channel proteins, or by treating them with the pore-forming antibiotic amphotericin B. This method appears useful to gauge the expression and function of pore-forming, water-permeable membrane proteins.     

A histological study of the organogenesis of the digestive system in bay snook Petenia splendida Günther, 1862 from hatching to the juvenile stage

In bay snook (Petenia splendida) larvae the histological development of the digestive system and swim bladder, and their relative timing of differentiation were studied from hatching to 45 days post‐hatch (dph) at 29°C. Newly hatched larvae showed a simple digestive tract, which appeared as a straight undifferentiated tube lined by a single layer of columnar epithelial cells (future enterocytes). The anatomical and histological differentiation of the digestive tract and accessory glands was a very intense, asynchronous process, proceeding from the distal to the anterior part. The intestine was the first region to differentiate (9 days post‐hatch – dph, 6.5 mm SL), and the oesophagus the last (21 dph, 8.4 mm SL). At the onset of feeding, the digestive system was organized into different functional and histologically differentiated sections, such as the buccopharynx, oesophagus, glandular stomach, and anterior and posterior intestine. This organization resembled that of the juveniles, with the exception of pharyngeal teeth and buccopharyngeal as well as oesophageal goblet cells, which proliferated later during the mixed feeding period. Histological observations revealed that bay snook larvae retained endogenous yolk reserves until 24 dph (8.9 ± 0.4 mm SL), which might be helpful for weaning this species onto a compound diet. The important lipidic accumulation observed in the intestinal mucosa, liver, and pancreas in fish fed a compound trout diet indicated that although fish were able to digest and absorb lipids, the diet formulation did not fit the nutritional requirements of early juveniles of this species. The ontogeny of the digestive system followed the same general pattern as in most cichlid species described to date. However, we detected species‐specific differences in the timing of differentiation that were related to their reproductive guild. According to the histological results, some recommendations regarding the intensive culture of this species are also provided.