Ιχθυοπλαγκτόν. Icthyoplankton. G. Koumoundouros. (L.A. Fuiman)

Transcription

1 Ιχθυοπλαγκτόν Icthyoplankton (L.A. Fuiman) G. Koumoundouros

2 Huge variety of reproductive patterns in finfish (internal or external fertilization, ovoviparity, oviparity, viviparity, with or without parental care, demersal or pelagic eggs, fecundity, egg size, etc etc etc etc)

3 The life cycle of Oviparous fish with pelagic eggs (egg laying, external fertilization, lack of parental care, high fecundity) (fig. from Fuiman 2002)

4 The life cycle of Oviparous fish with pelagic eggs Ichthyoplankton: the early life stages of finfish with pelagic eggs Variations pelagic adults pelagic ELS demersal adults pelagic ELS

5 Ichthyoplankton Some reasons to care about An important component of plankton A critical phase of the life cycle of a species Small changes in survivorship of ELS can translate into large variations in adult population size Developmental defects of ELS are powerful indices of environmental disturbances (e.g. chemical and physical pollution) 3

6 Ichthyoplankton Challenges of Planktonic life Main characteristics Locate and catch prey Avoid been a prey Stay synchronised (in space and time) etc, etc Transparency Small size and high growth rates Quantitative match of structural design and functional parameters (Symmorphosis) etc, etc

7 Early life stages of oviparous finfish 1 mm Ø Embryonic stage 2 mm TL Yol k-sac larval stage 4 mm TL 5 mm TL 6 mm TL Pre-flexion stage Flexion stage Larval stage 9 mm TL 12 mm TL 4 5 Metamorphosis stage (post-flexion) 22 mm TL 6 Juvenile stage

8 Embryonic stage Lipid globule 1 Yol k Chorion Main Anatomical Features Perivitelline space Animal pole Hyponeustonic, mm in diameter Telolecithal eggs with meroblastic cleavages Indicative stages of the embryonic development (drawing from Fuiman 2002)

9 Embryonic stage Species specific morphological variability (figure from Alhstrom and Moser 1980)

10 Yol k-sac larval stage Main Anatomical Features Indicative stages (drawing from Fuiman 2002) (Koumoundouros et al. 1998)

11 Yol k-sac Larval stage Species specific morphological variability (figure from Mito 1966)

12 Larval stage Main Anatomical Features 1 Indicative stages Swimbladder 2 Pigment cells Nostril Myomere Dorsal fin bud Notochord 3 4 Pre-opercular spines Liver Caudal fin bud Pelvic fin Anus Anal fin bud bud Urinary duct Pectoral fin bud 5 6 (Koumoundouros et al. 1999)

13 Larval stage Species specific morphological variability (from Re and Meneses 2009)

14 Larval stage Species specific morphological variability

15 Larval stage Species specific Ontogenetic pattern (from Fuiman 2002)

16 Duration of the different stages Species specific High dependence on the water temperature Stage Duration (SD) LARVAL STAGE SD = a T -b Temperature (T) At a given Temperature, the ontogenetic stage depends on the AGE At a given Temperature, the ontogenetic stage depends on the BODY SIZE Growth and Differentiation are tightly connected High dependence on food availability, intraspecific competition, etc 4 (from Fuiman 2002)

17 Ichthyoplankton Surveys Main Goals To study the distribution of ELS in space and time To estimate growth, mortality and recruitment rates To study the trophic relationships in the plankton To estimate the degree of environmental disturbances (developmental defects as indices of env. dist.)

18 Ichthyoplankton Surveys Sampling Methot-Issacs-Kidd-trawl (MIKT) Bongo-net (

19 Ichthyoplankton Surveys Fixation & Preservation In special solutions (formalin, ethanol, etc) (

20 Ichthyoplankton Surveys Systematic Identification Useful characters External morphology Morphometry Pigmentation pattern Special characters Osteology Meristics Ontogenetic state at certain body size

21 Ichthyoplankton Surveys Ostelological features

22 Ichthyoplankton Surveys Analyses Age and growth estimations Abundance estimation Study of the feeding preferences Presence of developmental abnormalities etc etc

23 Lab Material Developmental stages Identify the main anatomical features of each sample (fins, pigmentation, internal organs, etc) Identify the developmental stage of each sample Draw the main anatomical characteristics of the larval stage Pigment cells Nostril Swimbladder Myomere Dorsal fin bud Notochord Pre-opercular spines Liver Caudal fin bud Pelvic fin Anus Anal fin bud bud Urinary duct Pectoral fin bud

24 Lab Material Osteological features and ontogeny Identify and draw the skeletal elements of the caudal fin Identify which elements are mebranous and which cartilaginous bones Correlate the developmental state of the caudal fin with the flexion of the notochord Alizarin Red S / Alcian Blue Ep, epurals; HS, haemal processes; Hy, hypurals; Na, modified neural arch of PU2. NS, neural processes; PrH, parhypural; PU, preural centra; Ur, urostyle; UrN1, uroneural 1.

25 Lab Material Ichthyoplankton samples Select all the specimens which are at the flexion stage Based on the external morphology and pigmentation pattern, count the number of the different species with specimens at the flexion stage Estimate the incidence of specimens belonging to a) pre-flexion, b) flexion and c) post-flexion stage

26 Effect of temperature on the developmental rate Autotrophic phase Duration =???

27 Effect of temperature on the developmental rate Autotrophic phase TsD TsD = a T b TsD -1 Tsd -1 = (T-T 0 ) D o eff Temperature (Τ, o C TsD= stage duration (h) Temperature (Τ, o C T 0 = threshold temperature D o eff = Thermal sum (h o C)

28 Effect of temperature on the developmental rate Autotrophic phase TsD -1 (T-T 0 ) Tsd -1 = Tsd -1 = D o eff T D o eff - T 0 D o eff Y = b X + a Temperature (Τ, o C)

29 Reporting 1) Describe the skeletal features of the caudal fin. Which is the correlation of notochord flexion with the development of caudal fin? 2) Which are the main anatomical features of the larvae at the flexion stage? 3) Which is the morphology of pigment cells in fixed specimens? 4) Using the data set of T-TSD, estimate the thermal sum and the thermal threshold (biological zero) of the autotrophic phase (regression analysis in excel).