Marine Invertebrates Lecture 2 PDF

BIO237 Marine Invertebrates Gelatinous marine animals Gelatinous marine animals (gelata) 1. We will discuss the taxonomy and biology of gelatinous zooplankton 2. We will look at the consequences of blooms of gelata 3. We will discuss the ecological roles of gelata: i. The “Jellyfish...

BIO237 Marine Invertebrates Gelatinous marine animals Gelatinous marine animals (gelata) 1. We will discuss the taxonomy and biology of gelatinous zooplankton 2. We will look at the consequences of blooms of gelata 3. We will discuss the ecological roles of gelata: i. The “Jellyfish Joyride” ii. Trophic roles Salps (Subphylum Tunicata) Comb jellies (Phylum Ctenophora) True Jellyfishes (Phylum Cnidaria, Class Scyphozoa) Box Jellyfishes (Phylum Cnidaria, Class Cubozoa) Hydromedusae (Phylum Cnidaria, Class Hydrozoa) Siphonophores (Phylum Cnidaria, Class Hydrozoa) Gelata taxonomy…  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Metazoa Parazoa Eumetazoa Radiata Bilateria Protostomia Deuterostomia Lophotrochozoa Ecdysozoa Platyhelminthes Cnidaria and Ctenophora Echinodermata Lophophorata Nematoda Rotifera Subphylum Chordata Arthropoda Mollusca Annelida Tunicata Porifera Ctenophora Cnidaria Lophophore or Ecdysis trochophore larva Deuterostome development, Protostome development endoskeleton Bilateral symmetry Tissues KEY Critical innovations Multicellularity Ancestral colonial choanoflagellate Gelata taxonomy… Animals separated by >500 million years but share a similarity in body design and planktonic lifestyle: Gelatinous body: water content 95% or higher “Gelatinous animals” include at least 2,000 spp. This body form has arisen, independently, multiple times in very different taxa Subphylum Tunicata Non-vertebrate chordates (together with Cephalochordata; lancelets) Barrel-like filter feeders with two siphons; 1 inhalant and 1 exhalent Adult body enclosed by a soft but tough outer covering; the tunic We know they are closely aligned to vertebrates because they have tadpole larvae (possess a notochord, a dorsal nerve chord, and pharyngeal slits). Subphylum Tunicata © Nick Hobgood Class Ascidiacea (sea squirts, benthic) Class Sorberacea (benthic, predatory) Class Appendicularia (larvaceans, planktonic) Class Thaliacea (pyrosomes and salps, planktonic) Class Thaliacea Order Pyrosoma Pyrosomes – colonial zooids (each one a few mm). Colonies can be enormous (tens of metres), however, and bioluminescent. Inhalent siphon outside; exhalent siphon inside Class Thaliacea Order Pyrosoma Pyrosomes – colonial zooids (each one a few mm). Colonies can be enormous (tens of metres), however, and famously bioluminescent Order Salpidae Salps – individual animals (up to 20 cm) resemble barrels with often musclecolonial bands, Order Doliolida Resemble small (0.5 – 5mm) salps individual, non colonial © Hartmut Olstowski RECOMMENDED READING Henschke et al. (2016) Rethinking the role of salps in the ocean. Trends in Ecology and Evolution 31 720-732 Nano- phytoplankton Micro- phytoplankton Zooplankton Henschke et al. (2016) Rethinking the role of salps in the ocean. Trends in Ecology and Evolution 31 720-732 During a swarm, salps can constitute 99% of the zooplankton biomass and cover an area of 100 000 km2 Phylum Ctenophora ea gooseberries, comb jellies a. 200 species ery delicate – hard to collect with nets Oval Lobate Ctenophores 8 set of comb-rows (cilia) for locomotion Carnivorous Swarm forming Class Tentaculata – two tentacles with sticky cells: colloblasts Also contains the benthic forms that are poorly understood Class Nuda – no tentacles The fall and rise of the Black Sea ecosystem 3 rivers : Danube, Dnieper, Dniester - fed by a drainage basin of >2 million km in the 2 northwestern/northern region are responsible for about 85% of total riverine input to the Black Sea (about 340 km3 year-1) Only ca. 10% of the depth of the Black Sea supports eukaryotic life; below 150 – 200 m is anoxic. 1970s and 1980s – increased eutrophication : 1.Increase in number and peak abundance of phytoplankton blooms including several red-tide events 2.Modification of the phytoplankton composition in favor of flagellates 3.Decreased oxygen concentration and expansion of hypoxia 4.Reduced transparency of the water column 5.Decrease in nongelatinous zooplankton 6.Mass mortality among the entire benthos, demersal and pelagic fish populations The fall and rise of the Black Sea ecosystem Early 1980s: accidental introduction of the ctenophore Mnemiopsis leidyi Enormous Mnemiopsis biomass levels reached (>1 kg m in 1989), devastating entire food −2 chain Collapse of pelagic fish population; massive economic damage to Turkish fishing industry Modest recovery of non-gelatinous zooplankton in 1994 - secondary Mnemiopsis bloom RECOMMENDED READING Kideys (2002) Fall and rise of the Black Sea ecosystem. Science 297 1482-1484 The fall and rise of the Black Sea ecosystem Reduction in eutrophic inputs and arrival of Beroe ovata (1997) resulted in control of the Mnemiopsis population and contributed to recovery of the Black Sea ecosystem. Increases seen in anchovy landings and egg densities of anchovy, as well as nongelatinous zooplankton. RECOMMENDED READING Kideys AE (2002) Fall and rise of the Black Sea ecosystem. Science 297 Phylum Cnidaria Cnidarians Class Scyphozoa True jellyfish Class Cubozoa Box jellyfish Class Hydrozoa Diverse forms, including siphonophores Class Anthozoa Corals (lecture 14), sea anemones Siphonophores ca. 175 known species, Up to 40m long, very delicate Colonial, entirely pelagic, often open ocean Scyphozoans Gonochoristic Scyphistoma Not all scyphozoans have a benthic polyp stage Pelagia noctiluca has adapted to an open ocean lifestyle Sensory organs Rhopalium ubozoans possess complex eyes Nilsson et al. (2005) Advanced optics in a jellyfish eye. Nature 435, 201-205 DietPredatory jellyfish use nematocysts to capture fish, shrimps, large zooplankton, other jellyfish, etc. (e.g. Lion’s Mane, Cyanea capitella) Jellyfish without feeding tentacles use mucilage on their oral arms to capture diatoms, ciliates, small copepods, etc. (e.g. Rhizostoma octopus)  Growth rates Rhopilema esculentum (Ariake Sea, Japan) grows from 1.7 cm (0.61 g wet weight; ww) to 70 cm (27 kg ww) between mid-May and early-September (100 days). Daily growth rate of ca. 9% Aurelia auritta (in the lab) grows up to 24% (dry weight) per day  © Leigh Dunne Gelata sometimes form massive blooms  Condon et al. (2012) Questioning the rise of gelatinous zooplankton in the world's oceans. BioScience 62 160-169 Scyphozoans Scyphozoans Ctenophores Salps Consequences of blooms Burst nets Impacts on fisheries Impacts on aquaculture and other industries Tourist impacts Promotion of toxic red tides  Jellyfish causing nets to burst (e.g. Benguela, Japan) © Shin-ichi Uye, Hiroshima University Fish kills (aquaculture) Pelagia 1994 Brittany, Salmon and trout killed noctiluca France Cyanea 1996 Scotland 1,000s salmon killed capillata £250,000 loss Solmaris 1997 Shetland Salmon killed corona Solmaris and 2001 Isle of Lewis 2,747,680 salmon killed others 11 incidents £5 million loss Apolemia 1997 West Coast of 600 tons salmon killed uvaria Norway Pelagia 2007 Northern 150,000 salmon killed noctiluca Ireland  It has been hypothesised that once jellyfishes are established they can outcompete fish populations because of their higher consumption rates, capacity to respond more rapidly to pulses in prey, and ability to prey upon early life stages of many fish RECOMMENDED READING Richardson AJ, Bakun A, Hays GC, Gibbons MJ (2009) The jellyfish joyride: causes, consequences and management responses to a more gelatinous future. Trends in Ecology and Evolution 24 312-322. Gelatinous zooplankton blooms are not new… Condon et al. (2012) Questioning the Fossilised mass strandings rise of gelatinous zooplankton in the world's oceans. BioScience 62 160- of scyphozoans 169 The perceived increase in the number of jellyfish blooms may be a case of shifting baselines Are we seeing more because of an increase in observational efforts?  Alternatively, do jellyfish numbers oscillate over long time scales? RECOMMENDED READING Condon RH et al. (2013) Recurrent jellyfish blooms are a consequence of global oscillations.Proceedings of the National Academy of Sciences of the United States of America 110 1000-1005. “there is no robust evidence for a global increase in jell Gelata have been historically considered unimportant in food webs and biogeochemical cycles because of their high water content and low calorific value: “trophic dead-ends”. Questioning trophic dead ends… Gelata show up poorly in stomach content analyses of fish, compared to other zooplankton Arai (2005) argues that the high rates of digestion (and presumably of assimilation) of gelatinous zooplankton make them sources of energy comparable to better recognized prey such as arthropods.  124 fish species and 34 species of other animals are reported to feed either occasionally or predominately on jellyfish. INSERT Youtube video of leatherback turtle eating scyphozoans https://www.youtube.com/watch?v=R ap3mnq0_lo Arai (2005) Predation on pelagic coelenterates: a review. Journal of the Marine Biological Society of the UK 85 523-536. Four species of penguins in seven locations All species in all locations seen targeting gelata (scyphozoans and ctenophores; salps observed but not attacked) as a food source Penguins observed swallowing whole or tearing off and consuming parts RECOMMENDED READING Thiebot J-B et al. (2017) Jellyfish and other gelata as food for four penguin species – insights from predator-born videos. Frontiers in Ecology and the Environment 15 437–441  Sato et al. (2015). The jellyfish buffet: jellyfish Jellyfish as FADs… enhance seabird foraging opportunities by concentrating prey. Biology Letters 11 20150358. Summary We’ve learnt a bit about the major groups making up the gelatinous marine animals We’ve seen the gelatinous body form has arisen multiple times in disparate taxa We’ve looked at the case study of Mnemiopsis in the Black Sea in some detail We’ve discussed gelata blooms and the “Jellyfish Joyride” Are gelatinous animals really “trophic dead ends”