ADAPTIVE COMPETENCE OF TELEOSTEI

Christian Bock, Katrin Deigweiher, Timo Hirse, Zora Zittier Alfred Wegener Institute, Bremerhaven, Germany

Objectives

There is no doubt that climate change will dramatically affect life of polar animals, which are specially adapted to low, and constant temperatures. In this context, two main objectives were elaborated on this cruise. Based on previous research, we investigated the influence of a rise in temperature on the ventilatory and circulatory performance of Antarctic fish. According to the theory of oxygen limited thermal tolerance, restrictions of the cardiovascular system are one of the key limiting factors of thermal tolerance. Therefore, Laser Doppler flowmetry as a non-invasive technique was used for online investigations on ventilation, circulation and perfusion (micro-circulation) in Antarctic eelpout Ophtalmolycus amberensis during an acute temperature rise to 4°C on board of RV Polarstern.

The second topic dealt with the question how increasing CO2 concentrations (hypercapnia) will affect lifestyle and behaviour of Antarctic fish. Based on model calculations the current seawater pH is going to drop by 0.5 units by the year 2100 due to increasing CO2 concentrations. This will have serious implications on the acid-base regulation and total energy availability for fish under acidified conditions. In our studies we therefore wanted to compare the sensitivity to hypercapnia of the gill’s energy consuming processes like protein and RNA/DNA synthesis, as well as ion regulation between different fish species. A specification on the ability of temperature adaptability of selected

ANT-XXIII/8, Scientific reports

fish, cephalopod and crustacean species will be done by molecular analysis of blood and tissue samples.

Work at sea

Fish caught from bottom or Agassiz trawls were collected and kept at habitat temperatures in the aquarium container on board Polarstern. Ventilation, heart rate and blood perfusion levels of different organs of the Antarctic eelpout Ophtalmolycus amberensis were measured in vivo by use of Laser Doppler flowmetry (LDF). The effects of an acute temperature rise from -0.5 to 4°C were investigated after at least 12 hours of recovery in the experimental setup. Additionally, first trial measurements of heart rate and blood velocity in two amphipod species were conducted.

Table 2.23 Fish, cephalopod and crustacean species of which tissue and blood samples were taken for molecular analysis.

Main taxa Species Station N° of

individuals Channichthyidae Chaenocephalus aceratus 674 5 Channichthyidae Chianodraco

rastrospinosus 674 5

Channichthyidae Champsocephalus gunnari 674 4 Nototheniidae Gobionotothen gibberifrons various 27 Nototheniidae Notothenia coriiceps from Jubany 14

Cephalopoda Paraledone cornata 615 1

Cephalopoda Megaleledone sp. 615, 617 3 Cephalopoda Megaleledone setebos 615, 616, 638, 643,

650, 651, 661, 676,

Cephalopoda Paraledone aurata 657 1

Cephalopoda Paraledone aequipillae 679, 682, 687, 689 5

Crustacea Eurythenus grillus 683 11

Crustacea Nothocrangon antarcticus 710 10 Crustacea Eusirius properdentatus 683 2

For experiments addressing the effects of hypercapnia on acid base regulation and tissue energy budget, respiration measurements on isolated and perfused fish gills were performed. Briefly, gills were dissected, connected to perfusion cannulaes, and placed into respiration chambers filled with pre-equilibrated seawater with a partial pressure of 10 000ppm CO2. Oxygen consumption rates were measured by using oxygen microoptodes and flow-through sensors. Specific inhibitors for protein-biosynthesis, RNA/DNA-Synthesis and pH- and ion regulation were applied to investigate the response of the main energy consuming processes to hypercapnic acidosis. Additionally, blood and tissue samples were collected for further

CAML and related topics

molecular analyses as well as for the analysis of biochemical blood properties from Antarctic fishes, cephalopods and decapods.

Preliminary results

Table 2.23 summarizes the collected animal species and tissue/blood samples taken for molecular and blood analyses.

0 5 10 15 20 25 30

0 1 2 3 4 5

O. amberensis

Ventilation rate (v/min)

Temperature (°C)

Fig. 2.19 Temperature dependent ventilation rate of Opthalmolycus amberensis.

Temperature incubation experiments of the Antarctic eelpout Ophtalmolycus amberensis. The Antarctic eelpout O. amberensis was used for temperature incubation experiments. Temperature of a water bath was increased up to 4°C over 3 hours and cooled back to control temperature of -0.5-0.0°C, subsequently. The complete experiment time was around 8 to 10 hours. LDF measurements were executed continuously over the duration of the entire experiment.

Fig. 2.19 presents preliminary results on temperature dependent ventilation rates of Ophtalmolycus amberensis. First, ventilation rate increased with temperature and levelled off at temperatures around 3°C already. This is in contrast to previous measurements on the closely related Antarctic eelpout Pachycara brachycephalum. In these experiments ventilatory effort increased exponentially until temperatures above 10°C. Additionally, some animals of O.

amberensis died some days after end of the temperature incubation experiments. These preliminary results might indicate that O. amberensis,

ANT-XXIII/8, Scientific reports

although closely related, is more sensitive to temperature fluctuations than P.

brachycephalum.

Effects of increased CO2 concentration on energy budget and acid-base regulation. After the addition of metabolic inhibitors, the amount of specific energy consuming processes from two Notothenoids could be determined measuring oxygen consumption rates of gills under these conditions. Fig. 2.20 depicts the cellular energy budget together with the main energy consuming processes from gills from Gobionotothen gibberifrons under control conditions in comparison to hypercapnia. Ion regulation, protein synthesis and RNA/DNA synthesis were the main energy consuming processes. Ion regulation and RNA/DNA synthesis were almost doubled under hypercapnic conditions, indicating strong regulation of acid-base regulatory processes. Fig. 2.21 summarizes the results for Notothenia coriiceps. It shows a similar picture in comparison to G. gibberifrons, except of a much lower increase of RNA/DNA synthesis rates.

Control Hypercapnia

Other processes

Ion transport

Protein synthesis RNA/DNA

synthesis

Fig. 2.20 Cellular energy budget of Gobionotothen gibberifrons. Used inhibitors were mainly effective on protein synthesis (cycloheximide), RNA/DNA synthesis (actinomycine) and Na⁺-K⁺-ATPase (ouabain).

Control Hypercapnia

RNA/DNA synthesis

Other processes

Ion transport Protein synthesis

Fig. 2.21 Cellular energy budget of Notothenia coriiceps. Used inhibitors were mainly effective on protein synthesis (cycloheximide), RNA/DNA synthesis (actinomycine) and Na⁺-K⁺-ATPase (ouabain).

CCAMLR and related topics

2.2 "CONVENTION ON THE CONSERVATION OF ANTARCTIC MARINE LIVING RESOURCES (CCAMLR)" AND RELATED TOPICS

2.2.1 THE COMPOSITION; DEMOGRAPHY AND BIOLOGY OF THE