Characterization and distribution of bombesin binding sites in the goldfish hypothalamic feeding center and pituitary

Bombesin (BBS)/gastrin-releasing peptide (GRP) binding sites were characterized and their distribution examined in the goldfish brain and pituitary by radioligand binding and autoradiography. Binding of ¹²⁵I-[Tyr⁴]-BBS-14 to tissue sections was found to be saturable, reversible, time-dependent and displaceable by BBS/GRP-like peptides. Analysis of saturable equilibrium binding revealed a one-site model fit with a K_d of 0.665 ± 0.267 nM. This binding site displayed high affinity for members of the BBS subfamily of peptides, including GRP10 (K_i; 0.292 ± 0.038 nM) and GRP27 (K_i; 2.034 ± 1.597 nM), but showed no affinity for the BBS_8–14 fragment. While an approximate 100-fold lower binding affinity was displayed by the binding site for neuromedin B (K_i; 61.5 ± 28.2 nM), litorin was highly effective in displacing radiolabeled BBS binding (K_i; 1.469 ± 0.427 nM). The localization of saturable and high affinity BBS/GRP binding sites in specific areas of the goldfish brain and pituitary generally revealed a similar anatomical distribution to BBS/GRP-like immunoreactive material reported previously by our laboratory. Quantitative densitometric analysis of radiolabeled BBS binding to brain nuclei and the pituitary revealed a moderate concentration of BBS/GRP binding sites in the hypothalamic feeding area, including the nucleus diffusus lobi inferioris, nucleus recessus lateralis, nucleus lateral tuberis, and nucleus anterior tuberis. Other brain nuclei known to influence the brain feeding center which contained a high density of BBS/GRP binding sites included nuclei of the dorsal and ventro-medial telencephalon, the preoptic hypothalamus, and the optic tectum. High densities of BBS/GRP binding sites were also localized in the dorsal cerebellum, and nucleus habenularis. In the pituitary, BBS/GRP binding sites were present in high concentration in the neurointermediate lobe, with a relatively lower density localized in the pars distalis. The present study further supports a role for BBS/GRP-like peptides in the regulation of feeding behavior and anterior pituitary hormone secretion in teleosts.     

Structure and evolution of teleost mitochondrial control regions

We amplified and sequenced the mitochondrial control region from 23 species representing six families of teleost fish. The length of this segment is highly variable among even closely related species due to the presence of tandemly repeated sequences and large insertions. The position of the repetitive sequences suggests that they arise during replication both near the origin of replication and at the site of termination of the D-loop strand. Many of the conserved sequence blocks (CSBs) observed in mammals are also found among fish. In particular, the mammalian CSB-D is present in all of the fish species studied. Study of potential secondary structures of RNAs from the conserved regions provides little insight into the functional constraints on these regions. The variable structure of these control regions suggests that particular care should be taken to identify the most appropriate segment for studies of intraspecific variation. Correspondence to: T.D. Kocher     

鱼类LZF-IDNA指纹探针的制备

利用Ｏｌｉｇｏ１０００ＤＮＡ合成仪（Ｂｅｃｋｍａｎ）合成了长度为４５ｂｐ的寡核苷酸单链,经纯化后用同位素γ－３２Ｐ－ＡＴＰ作５′末端标记后,制备成鱼类ＬＺＦ－ＩＤＮＡ指纹探针。通过对鱼类的群体实验、亲子鉴定实验、组织细胞的稳定性实验和鱼类种类的适用范围实验后,测得：（１）ＬＺＦ－ＩＤＮＡ指纹探针属多位点寡核苷酸探针;（２）ＬＺＦ－ＩＤＮＡ指纹探针在鱼类种群中的鉴别机率为９．２３×１０－１６;（３）ＬＺＦ－ＩＤＮＡ指纹探针在鱼类亲子鉴定实验中的父系概率为０．９９９９６２;（４）ＬＺＦ－ＩＤＮＡ指纹探针,是一种稳定的,既具有个体识别能力,又具有一定种属特异性的、适用于鱼类ＤＮＡ指纹图研究的基因指纹探针。     

The larval development of lateral musculature in gilthead sea bream Sparus aurata and sea bass Dicentrarchus labrax

Fibre-type differentiation of the lateral musculature has been studied in Sparus aurata (L.) and Dicentrarchus labrax (L.) during larval development. Histochemical and ultrastructural techniques show two presumptive muscle layers and two germinative zones of presumptive myoblasts. At hatching, myotomal muscle consists of a monolayer of thin undifferentiated cells near the skin (first germinative zone) overlying another mono-layer of small diameter fibres extending hypaxially and epaxially away from the transverse septum. Below this, there is a much thicker, deep layer of fibres, generally large in diameter and polygonal in shape. The presumptive myoblasts are located between these two layers of fibres in the second germinative zone. Initially, the superficial and deep muscle fibres show high and low myosin ATPase activity, respectively. Both layers grow by generating new fibres from the two mentioned germinative zones. At the end of larval life, the superficial layer changes its histochemical profile from high to low myosin ATPase activity and, at the same time, intermediate or pink muscle fibres can be observed by oxidative activity (the NADH-TR reaction). Morphometric analysis shows a significant increase in mean fibre diameter during successive ages, as shown by the Student's t-test (hypertrophic growth). Skewness and kurtosis values of fibre diameters point to the generation of a new fibre population from the germinative zones (hyperplastic growth).     

Experimental analysis of some factors affecting parental expenditure and investment inCichlasoma nigrofasciatum (Cichlidae)

Synopsis Parental investment is the cost of providing parental care. The short-term cost of parental care was measured in the biparental substrate nesting cichlid,Cichlasoma nigrofasciatum, by comparing the expected future survival (measured indirectly as energy content of the body), time taken to breed again and, among females, the number of eggs produced at a subsequent spawning of parental and non-parental pairs. In comparison with non-parental pairs, parental pairs took significantly longer to respawn. Body condition and female fecundity were unaffected after a single parental cycle. The effect on parental cost and expenditure of factors likely to stress the parental fish was also investigated. Removing the male parent had no effect on female parental cost. Exposing pairs to potential predators of offspring increased the time taken by pairs to respawn. In parental males, reducing the level of feeding gave rise to a reduction in some care behaviours.     

The ecology of ruffe,Gymnocephalus cernuus (Pisces: Percidae) introduced to Mildevatn,western Norway

Synopsis Diet, habitat use, diel and seasonal activity and a number of population parameters were studied on ruffe,Gymnocephalus cernuus, introduced to Mildevatn, western Norway. This lake is sited outside the natural range of the ruffe and has a lower fish diversity and a different fish species composition than within its native range. From June through September the ruffe was planktivorous and mainly caught at 4 to 6 m depth in the benthic zone. At other times of year ruffe was feeding on zoobenthos and caught deeper in the benthic zone. Ruffe was mainly day active. Zooplankton feeding during summer is the clearest difference compared to ruffe populations living within its natural range. Presence of large zooplankton organisms available for ruffe is suggested as the main reason for the difference found in food choice. The availability of large zooplankton is probably due to community structure caused by a predator and lack of interspecific competition for zooplankton in the deeper parts of the lake. Piscivorous brown trout.Salmo trutta, restrict the habitat of threespined stickleback,Gasterosteus aculeatus, to the zone of littoral vegetation, allowing high densities of larger zooplankton species likeBythotrephes longimanus to be present in the lake. Brown trout is present only in the upper light and well oxygenated parts of the lake, leaving a refuge for the ruffe, where they can feed on the rich zooplankton community.     

Exercise,agonistic behaviour and food acquisition in Arctic charr,Salvelinus alpinus

Synopsis Although swimming is energetically costly, a number of studies on salmonid species have demonstrated increased growth rates in fishes forced to swim for prolonged periods at moderate speeds (typically 1–2 body lengths per sec). This suggests that additional energetic costs of swimming are more than met by alternative compensatory gains. The mechanisms underlying such effects are not fully understood. In this paper, we describe an experiment designed to examine one possible mechanism, namely a swimming-induced inhibition of aggression, with consequent beneficial effects on growth. The study used Arctic charr,Salvelinus alpinus, a species for which a positive relationship between exercise and growth has been clearly established. Using direct behavioural observations on small groups, we demonstrate that individuals displaying high levels of aggressive behaviour are able to monopolise access to food and that enforced swimming at a moderate speed (1 body length per sec) reduces the incidence of aggression although not the degree of monopolisation of food shown by aggressive individuals. These results suggest that the enhanced growth rates accompanying enforced swimming may reflect lower energetic costs of reduced aggressive activity rather than improved access to food by subordinates.     

Electron microprobe analysis of juvenile walleye pollock,Theragra chalcogramma,otoliths from Alaska: a pilot stock separation study

Synopsis The incorporation of dissolved oceanic constituents in the otoliths of fish has potential as a chemical tracer for reconstructing the early life history of marine fish. Wavelength dispersive spectrometers on an electron microprobe were used to measure Na, Mg, P, S, Cl, K, Ca, and Sr concentrations on the outer margins of 57 juvenile walleye pollock, Theragra chalcogramma, otoliths from five locations in the Gulf of Alaska and Bering Sea. Discriminant analyses that used various combinations of Na, P, K, Sr, and fish standard length and/or age showed that 60–80% of the samples could be assigned to the correct capture locality. While the concentrations of some of the measured elements correlated with standard length or age of the fish, there are measurable differences among localities when concentrations are length or age corrected, mainly due to differences in Na and K concentrations. Elemental composition of otoliths potentially could be used to assign fish from a mixed stock fishery to original stocks, information that is greatly needed for the effective management of fish stocks.     

Field and laboratory observations of spawning periodicity and behavior of a northern population of the Atlantic silverside,Menidia menidia (Pisces: Atherinidae)

Synopsis The spawning periodicity and mating behavior of a northern population of the Atlantic silverside, Menidia menidia, was studied both in the field (Salem Harbor, Massachusetts) and in laboratory experiments. Spawning in the field coincided with new and full moons. Under conditions of unlimited food availability in artificial outdoor pools that received natural celestial illumination or in indoor aquaria receiving no evening illumination, spawning occurred every 1–3 days rather than fortnightly. These results suggest that tidal influences are a primary factor that synchronizes spawning in M. menidia. Published reports of diel time of spawning in both marine and freshwater species of Menidia indicate a generic tendency to spawn during mid-morning. This pattern coupled with high tides that cover suitable spawning substrates during mid-morning only at fortnightly intervals could account for the semilunar spawning cycle in marine populations of Menidia. Although general characteristics of the reproductive ecology of M. menidia in Massachusetts were similar to a thoroughly studied population in South Carolina, several differences were evident. The breeding season was shorter in Massachusetts (late; April–June), and occurred over a much lower range of temperatures (9–21°C). Intensity and frequency of spawning was correlated with the height of high tide. Eggs were deposited only on mats of intertidal, filamentous algae rather than on roots or stems of Spartina alterniflora or other intertidal vegetation. Promiscuous spawning occurred in small, highly male-dominated groups of fish, primarily after the tide had begun to recede, and often at the water's edge. No predation on spawning adults was observed but the mummichog, Fundulus heteroclitus, fed daily on developing embryos during high tide. Contribution No. 81, Massachusetts Cooperative Fisheries Research Unit, Contribution No. 349, Marine Sciences Research Center, State University of New York at Stony Brook.     

Distribution of fibres reacting with an α-endorphin antiserum in the neurohypophysis of Carassius auratus and Cyprinus carpio

Summary A strong positive immunoreaction with an -endorphin antiserum occurs in two distinct sites of the goldfish and carp neurohypophysis. Fluorescent nerve terminals are found in the laminar nerve processes located in the rostral pars distalis, but the immunocytological reaction is mainly localised on the nerve processes of the posterior neurohypophysis lying between the intermediate lobe cells. Almost all the digitations of the neurohypophysis are strongly fluorescent. The immunoreactive fibres probably originate from the hypothalamus, where perikarya displaying the same immunoreaction have been found in the pars lateralis of the nucleus lateralis tuberis and in some minor centres. The possibility that the immunoreactive substances revealed on the neurohypophyseal processes may originate in the intermediate lobe cells is also discussed. It has now to be established if this hypothalamo-hypophyseal system contains a substance with endorphic properties or only some immunologically related substance devoid of the corresponding physiological activities.