Ontogenetic diet shift in the June sucker Chasmistes liorus (Cypriniformes,Catostomidae) in the early juvenile stage

Kreitzer JD, Belk MC, Gonzalez DB, Tuckfield RC, Shiozawa DK, Rasmussen JE. Ontogenetic diet shift in the June sucker Chasmistes liorus (Cypriniformes, Catostomidae) in the early juvenile stage.
Ecology of Freshwater Fish 2010: 19: 433–438. © 2010 John Wiley & Sons A/S Abstract – Ontogenetic diet shifts are common in fishes and often occur during early life stages. The larval and early juvenile period is critical in the life cycle of the endangered June sucker, Chasmistes liorus (Teleostei: Catostomidae). High larval and juvenile mortality leads to low recruitment to the breeding population and hence a declining natural population. To understand diet composition and dynamics in June sucker at early life stages, diet was quantified and compared to available food items in the natural environment during the early juvenile stage. Rotifers (Brachionus sp.) were the primary diet item at week 10, but by week 12 a small cyclopoid copepod (Microcyclops rubellus) became predominant. Availability of diet items varied little across the experimental period. The increase in size of young suckers may explain this rapid dietary shift, but there are some inconsistencies with the size selection argument. This diet shift represents an important nutritional change that should be considered in development of diets for young June sucker and in assessing suitability of nursery habitats.     

Aspects of the pathology of Lamproglena clariae (Copepoda: Lernaeidae) on gills of Clarias gariepinus from the Vaal River system,South Africa

Lamproglena clariae attaches to gill filaments of Clarias gariepinus, penetrates the gill tissue and consumes blood. Hence, the purpose of this study was to investigate the mechanical damage caused by this parasite on gill filaments of the host. Infestation intensity and haematocrit values of fish blood were determined and correlated. Fish were killed, gills dissected out and observed with a dissection microscope. Gill filaments with adult females in situ were fixed in a solution of alcohol, formaldehyde and acetic acid and preserved in 70% ethanol. Fixed specimens were studied by histological examination following staining with Heidenhein’s azan solution. Gross morphology revealed varying degrees of swelling of gill filaments near the attached specimens of L. clariae. Epithelial hyperplasia, resulting in fusion of gill lamellae and necrosis of the host tissue in the vicinity of the parasite were revealed through histological examination. No correlation was evident between the infestation intensity and fish haematocrit values. Although results showed that L. clariae causes localized infestation, high intensity of infestation may be detrimental to the fish. Hyperplasia of epithelial tissue resulting in fusion of lamellae would result in restriction of air passages and thus hinder the process of respiration of the host.     

水螅对水蚤卵孵化的效应研究

[目的]探讨利用生物法控制供水水源水蚤爆发的可行性,为自来水厂控制水蚤爆发提供参考。[方法]测定经水螅吞噬后水蚤卵的孵化时间和平均孵化率,并对未孵化的水蚤卵进行活性检测。探讨多形水螅对水蚤卵孵化的影响。[结果]经水螅分别吞噬的单水蚤和多水蚤,被消化排遗后的水蚤卵,其孵化时间为8～24 h,平均孵化率分别为56.42%和55.07%;未孵化的水蚤卵均被台盼蓝染色,且有原生动物侵蚀。对照组水蚤卵孵化率为100%,孵化时间为8～16 h。[结论]经水螅消化排遗后的水蚤卵,其孵化率明显受到抑制。     

Metazoan parasites on gills of Southern Bluefin Tuna (Thunnus maccoyii) do not rapidly proliferate after transfer to sea cages

A relatively new and highly valuable aquaculture industry focuses on three species of bluefin tunas, which are captured from the wild and fattened for several months in sea cages. In teleost aquaculture, mortalities and extra production costs are very commonly associated with metazoan ectoparasites. In tuna, however, the production value lost due to diseases associated with ectoparasites is unknown. We collected epidemiological data on burdens of metazoans on the gills of farmed southern bluefin, Thunnus maccoyii, in a series of monthly samples of tuna from the time of stocking through to harvest (March to August, 2004; N = 210) in five sea cages on a farm off Port Lincoln, Australia. Three species were recorded; for one (a copepod, Pseudocycnus appendiculatus), there was a gradual, significant increase in both abundance (from a mean of 0.1 in March, to 3.83 in August) and prevalence (from 10% to 67.5%). For the other two species (a second copepod, Euryphorus brachypterus, and a polyopisthocotylean flatworm, Hexostoma thynni) there were no discernible trends in prevalences and abundances. These results contrast markedly with those of other intensively cultured species of finfishes, in which parasite epizootics are frequent. This finding may indicate that despite the stresses of captivity, tuna mount a robust immune response to ectoparasites; the relatively low stocking densities at which tuna are farmed may facilitate this. The fall in water temperature during farming (22 °C to 13 °C) may also reduce the reproductive rate of these ectoparasites.     

How to protect a diverse,poorly known,inaccessible fauna: identification and protection of source and sink habitats in the epikarst

• 1. Aquatic subterranean species are often geographically and numerically scarce. Many of these species are denizens of epikarst, the uppermost zone of karst with semi‐isolated solutional openings and channels, and are only known from drip pools in caves where they accumulate as a result of animals dripping out of the epikarst.
• 2. The question of whether these pool communities adequately reflected the epikarst community was addressed by directly collecting animals from drips in a continuous collecting device.
• 3. The study area was six caves in Slovenia, where a total of 35 drips and associated pools were sampled for copepods for a period of approximately one year. A total of 37 copepod species were found, 25 of them stygobionts and 16 epikarst specialists.
• 4. Overall, the frequency of stygobionts was 1.5 times higher in drips compared with pools and the frequency of epikarst specialists was three times higher in drips compared with pools, and the frequency of immature individuals was higher in drips compared with pools, with the exception of one artificially enlarged pool in ?kocjanske jame. The cause of this difference is probably increased juvenile mortality in pools and reduced reproduction, indicating that pools are not source populations.
• 5. The results of this research suggest that epikarst per se, not just the sampling sites (including pools) in caves, needs to be the focus of conservation planning. Copyright © 2010 John Wiley & Sons, Ltd.

     

Description of electrophoretic loci and tissue specific gene expression in the horseshoe bat genus Rhinolophus (Rhinolophidae)

The number of loci encoding an enzyme system, tissue specificity of gene expression and the degree of gene expression in various tissues are often not mentioned in evolutionary studies, but could indirectly provide evidence of evolutionary relationships. Protein electrophoresis was used to study the distributions and tissue specificity of gene expression of enzymes encoded by 42 loci in Rhinolophus clivosus and R. landeri, the genetically most divergent of the ten species of southern African horseshoe bats. No differences in gene expression were found between R. clivosus and R. landeri and isozyme patterns may be compared with other bat species to derive possible phylogenetic relationships.     

Identification of cDNAs induced by the organophosphate trichlorphon in the parasitic copepod Lepeophtheirus salmonis (Copepoda; Caligidae)

Lepeophtheirus salmonis is a copepod ectoparasite of wild and farmed salmonids and can cause considerable damage to infected fish. We have examined the effect of the organophosphate trichlorphon, which was one of the early treatments for sea lice as Neguvon^® on L. salmonis. Suppression subtractive hybridisation was used to prepare a cDNA library enriched for cDNAs expressed in response to the organophosphate trichlorophon and using this technique a total of 33 cDNAs were found to be differentially regulated in response to organophosphate exposure. Sequence analysis of the cDNAs revealed that many were involved in cellular stress responses and or neurotoxicity. The expression of two of these cDNAs was confirmed to be up-regulated in response to trichlorophon.     

三道河水库浮游甲壳动物群落结构特征的初步研究

研究了湖北省三道河水库２００７年８月至２００８年４月浮游甲壳动物的群落结构及现存量的时空变化。三道河水库６个采样点（Ⅰ ～Ⅵ）共鉴定出浮游甲壳动物８科、１３属、２１种,其中枝角类５科、９属、１４种,优势种为简弧象鼻蟤（Ｂｏｓｍｉｎａｃｏｒｅｇｏｎｉ）、短尾秀体蟤（Ｄｉａｐｈａｎｏｓｏｍａｂｒａｃｈｙｕｒｕｍ）和透明蟤（Ｄａｐｈｎｉａｈｙａｌｉｎ）;桡足类３科、４属、７种,优势种为广布中剑水蚤（Ｍｉｃｒｏｃｙｃｌｏｐｓｌｅｕｃｋａｒｔｉ）和汤匙华哲水蚤（Ｓｉｎｏｃａｌａｎｕｓｄｏｒｒｉｉ）。浮游甲壳动物年平均密度为９２．６个／Ｌ,枝角类和桡足类分别为３６．９个／Ｌ和５５．７个／Ｌ;平均生物量为１．１２６ｍｇ／Ｌ,枝角类和桡足类分别为０．７３７ｍｇ／Ｌ和０．３８９ｍｇ／Ｌ。浮游甲壳动物现存量的季节变化明显,密度和生物量由高到低依次为秋季＞夏季＞冬季＞春季。浮游甲壳动物密度的水平分布差异明显,采样点的密度和生物量由高到低为Ⅱ ＞Ⅵ ＞Ⅲ ＞Ⅰ ＞Ⅳ ＞Ⅴ。     

巢湖太湖新银鱼寄生虫调查和食物组成

于2006年11月和2007年8月、9月、11月在巢湖5个采样点分别进行了4次调查,研究了太湖新银鱼(Neosalanx tangkahkeii taihuensis Chen)的寄生虫种类、感染率、感染强度、食物组成等指标。结果显示:巢湖的太湖新银鱼感染的寄生虫是双线绦虫,感染率8月份为(57.14±53.45)%,9月份为(66.67±47.76)%,两月平均感染率为(65.22±48.15)%;感染强度8月份为(0.71±0.76)个/尾,9月份为(1.59±1.80)个/尾,两月平均感染强度为(1.46±1.71)个/尾。桡足类是太湖新银鱼的主要食物,在8月份食物中平均个数组成比例为(66.32±11.85)%,出现率为100%;在9月份食物中平均个数组成比例为(57.86±31.00)%,出现率为87.18%。     

三北地区内陆盐水的浮游甲壳类

１９９０－１９９１年间在三北地区盐度０．５７－２１４ｇ／Ｌ的２８个内陆水体采集了浮游甲壳类水样，共检出４３种甲壳类，其中无甲类２种，枝角类２３种，桡足类１８种。根据经和平均密度，浮游甲壳类的主要种类有１２种，邓无甲类：卤虫；枝角类：大型蚤、扁平小剑水蚤和等刺温剑水蚤。