[Jul 30th, 2015] – Lectures, Seminars (Team Round-headed Apple Borer)

[Jul 30th, 2015] – Lectures, Seminars (Team Round-headed Apple Borer)

[2015年7月30日] 讲座,研讨会(苹圆头天牛小队)

Blog Entry Written by Team: Round-headed Apple Borer

Team Members: Jacqueline Chiu (U of T), Joshua Boateng (Trent U), Yunhui Zhou (Fudan), Yeqi Lin (SW).

Weather: Sunny, Temp: 20-28℃.

Today was filled with many seminars and lectures and so we were indoors all day. We started the day with Dr. Wang’s lecture on Fish Biodiversity and Conservation. We learned about the origins of fish including the fact that fish are the first vertebrates in history. We learned about two species of jawless fish, which are hagfish (Myxiniforms spp.) and lamprey (Lampetra spp.). Here are some facts about the hagfish and the lamprey species:

Hagfish Lamprey
~60 species, eyes covered with thick skin, lack paired fins, predator & scavenger. ~40 species, pre-longed larval period with multiple life stages, parasite to fish, eggs buried in sediment, spawn in freshwater, migrate to seawater, 75-100 cm, sectorial disc teeth, lack paired fins.

Lamprey can be an invasive species, so people have adopted several methods to control this including:

-building dams to block the lamprey

-using chemicals to kill the lamprey

-using pheromones to attract males and sterilize them and then put them back into the ecosystem; this prevents the males from being able to spread their sperm, which in turn helps decrease the population.

But strictly speaking, jawless fish is not a “fish”, though they usually have a fish-like body shape. The hagfish and lamprey we mentioned above actually belongs to the class Cyclostomata, which does not include the fish we commonly refer to.

The next topic was about jawed fish, which is split up into two categories, bony fishes (Teleostomi), in which 41% are freshwater fish, and cartilaginous fish (Chondrichthyes). Dr. Wang mainly focused on bony fishes. The structures of the fish correspond to specific functions. They have gills for gas exchange, ion regulation, acid-base regulation, filtering water and excreting nitrogen waste. They also have a complex skull to allow feeding, respiration and sensation. Their skeleton and muscles are mainly focused in the trunk of the fish body.

The next lecture presented by Dr. Wang was about his past and current research on Comparative Physiology. Dr. Wang mentioned that he did his research on non-lab animals which means that he always brought the lab to where the species were located as opposed to having the species brought into a lab. This ensured that the species were in their natural environment. Another key point that Dr. Wang mentioned was that morphology reflects functionality. He talked about fishes he encountered during the period of his research including Pirarucu (Arapaima gigas), Oscar (Astronotus ocellatus), Armoured catfish (Pterygoplichthys multiradiatus) and Naked carp (Gymnocypris przewalski). Here are some further details about each fish:

Species of Fish Features
Pirarucu l  2-3 m in size

l  Obligated air-breather, use bladder to retrieve O2

l  Deformed gills, remove CO2 through the gills

l  Extraordinary kidney

Oscar l  Have a bright spot on the tail to trick predators and increase their chance of survival

l  Can tolerate 0.3 mg/L of O2 at 30 degree Celsius

l  Can tolerate the daily fluctuation of O2 (0.3- 9 mg/L)

l  Can shut down one gill to slow down metabolism and conserve energy

Armoured catfish l  Can tolerate extreme hypercapnia and acid-base disturbance

l  Do not regulate extracellular pH

l  Hemoglobin does not display the Root effect

Naked carp l  No scales

l  Slow growth (300 g/10 year)

l  Omnivorous

l  Migrates to freshwater for spawning (anadromous)

l  Not stenohaline (can tolerate a large fluctuation in the salinity of water)

l  Hypoxic tolerant (can tolerate low levels of O2)

Since all these fish have swim bladders, they all experience the Root Effect which is a physiological phenomenon that occurs in fish hemoglobin where with an increased H+ or CO2 concentration, hemoglobin’s affinity and carrying capacity for oxygen decreases.

In the afternoon, we had four student seminars. The topics we talked about include Climate Change, Invasive Species, Eutrophication and Dams. We were one of the groups to present and our topic was Eutrophication. Eutrophication is a natural phenomenon that occurs in an aging lake or pond where nutrients that enter the bodies of water feed the algae causing excessive growth of the algae. Eventually, the algae have to compete for resources and nutrients and some die off, decaying and settling to the bottom of the body of water, decreasing the size of the water body. Our day ended after the student seminars.

今天我们基本上在室内,因为活动主要是上课和研讨会。早上王教授跟我们讲了鱼类多样性和其多样性的保护。鱼类是一种既古老又现代的生物,它们是地球上第一批脊椎动物,而且成功繁衍到了现在。以下是讲座的主要内容。

  1. 无颌类

无颌类严格来说不是“鱼类”,虽然它们通常拥有鱼形的身体。本次讲座主要关注的盲鳗和七鳃鳗这两种生物,在分类上属于圆口纲,而我们通常讲的“鱼”,是指鱼纲中的生物。

盲鳗是大概60个物种的统称,它们的共同特点包括:眼睛退化,并且被厚厚的皮肤覆盖;缺少成对的鱼鳍;能捕捉猎物,也能食腐。

七鳃鳗是大概40多个物种的统称。它们有较长的幼虫期,成体寄生在鱼类上,靠吸食血液为生。在产卵期,一些海水中的七鳃鳗会洄游到淡水区,把卵埋在沉淀物中。七鳃鳗的体长可以达到75-100cm。跟盲鳗一样,它们没有成对的鱼鳍。

七鳃鳗在一些地方是入侵物种,所以人类想了很多种不同的方法来控制其数量,包括:修建水坝使其找不到产卵地、利用化学试剂TFM阻断其细胞内呼吸链、或者利用性激素吸引雄性七鳃鳗,抓捕后对其进行节育处理,再将他们放回生态系统当中。前两种办法都有各自的缺点,第三种方法可以有效降低七鳃鳗的生育率,从而控制其数量。

  1. 有颌类

同样分为了两种:硬骨鱼和软骨鱼。41%的硬骨鱼是淡水鱼类。针对硬骨鱼类,王教授做了更加详细的介绍。硬骨鱼类的鳃有多种功能,包括气体交换、调节离子平衡、酸碱平衡、过滤水体、排泄含氮废物等。它们还拥有复杂的头骨,使其能够顺利地进食,呼吸和感知外界环境。硬骨鱼的骨架和肌肉主要在躯干部分。

王教授第二堂课是关于他以前的研究内容。因为需要研究一些不能在实验室饲养的动物,他常常把实验仪器带到研究对象栖息的地方,这样保证了这些鱼在被研究前处于正常的生活环境中。为了说明鱼类的形态反映它们的功能,王教授举了一些他在研究中遇到的例子:

鱼类的种类 特点
Pirarucu l  体长约2-3cm。

l  只能在空气中呼吸, 从鱼鳔中获取O2,从鱼鳃中排出CO2

l  肾的功能及其发达。

Oscar l  在尾部有一个亮点以迷惑捕食者,这样可以提高生存率。

l  可以忍受极低的氧含量(0.3mg/L, 30摄氏度)。

l  可以忍受氧含量的大幅波动O2 (0.3- 9 mg/L)。

l  在低氧环境下,可以减少一个腮的血流量以降低代谢速率。

Armoured catfish l  可以忍受血液中高浓度的CO2,和体内pH严重偏离。

l  不调节细胞外pH。

l  血红蛋白不会有Root effct

Naked carp l  无鳞鱼。

l  生长缓慢(300 g/10年)。

l  杂食性。

l  需要洄游到淡水中产卵。

l  可以忍受水体盐度的大幅波动。

l  可以忍受低氧浓度。

附:Root effect指在血液中pH和CO2浓度偏离正常值情况下,有时血红蛋白结构发生太大的变化使其最大携氧能力下降的现象。

在晚上,我们有4个学生研讨会,主题包括:气候变化、入侵生物、富营养化和水坝对生态系统的影响。我们是其中的一组,主题是富营养化。在正常情况下,在湖泊演替的后期会发生富营养化,水体变浅,最终变成陆地。但人为活动会使其进程大大加快。富营养化常常伴随着藻类爆发,藻类死亡后,细菌大量繁殖,水体氧含量急剧下降,引起大量生物死亡。富营养化在许多国家是一个严重的问题,急需解决。

晚上研讨会结束后,我们结束了一天的学习。

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