OEB51: The Biology and Evolu on of Invertebrate Animals Lectures: BioLabs 2062 Labs: BioLabs 5088
Instructor: Cassandra Extavour BioLabs 4103 (un l Feb. 11) BioLabs2087 (a er Feb. 11) 617 496 1935 [email protected]
Teaching Assistant: Tauana Cunha MCZ Labs 5th Floor [email protected] Basic Info about OEB 51 • Lecture Structure:
• Tuesdays 1-2:30 pm: • ≈ 1 hour lecture • ≈ 30 minutes “Tech Talk” • the lecturer will explain some of the key techniques used in the primary literature paper we will be discussing that week
• Wednesdays: • By the end of lab (6pm), submit at least one ques on(s) for discussion of the primary literature paper for that week
• Thursdays 1-2:30 pm: • ≈ 1 hour lecture • ≈ 30 minutes paper discussion • Either the lecturer or teams of 2 students will lead the class in a discussion of the primary literature paper for that week
• There will be a total of 7 paper discussions led by students • On Thursday January 28, we will have the list of papers to be discussed, and teams can sign up to present Basic Info about OEB 51 • Bocas del Toro, Panama Field Trip:
• Saturday March 12 to Sunday March 20, 2016: • This field trip takes place during spring break! • It is mandatory to a end the field trip but… • …OEB51 will not meet during the week following the field trip • Saturday March 12: • fly to Panama City, stay there overnight • Sunday March 13: • fly to Bocas del Toro, head out for our first collec on! • Monday March 14 – Saturday March 19: • breakfast, field collec ng (lunch on the boat), animal care at sea tables, lab work, dinner, back to lab… • Sunday March 20: • fly back to Boston
• You do NOT have to be able to SCUBA dive, have a wet suit or snorkel, be an expert swimmer, speak Spanish, or pay any associated expenses • You DO have to be able to tread water, and to feel comfortable on a boat and in water for several hours at a me To request a spot in the course…
• Email the following informa on TODAY to Tauana Cunha [email protected] – Name – Email address – Concentra on – Year – Mo va on for taking the course (max 4 sentences) • We have to have the informa on above before MIDNIGHT on Thursday January 28 • We will email accepted students by 12:00 noon on Friday January 29 • If you are serious about taking this course, be prepared to provide a scan (PDF) of the photo page of your passport on FRIDAY of this week – We need this to request a collec on permit in Panama. What will happen a er today
• By 12:00 noon on Friday January 29: – We will no fy all interested students of whether or not we have accepted them for the course – We will make available on the course website a list of the papers for discussion this semester • By 5:00 pm on on Saturday January 30: – All enrolled students must have • Handed in a signed disclaimer form for Panama field collec on (these are available in class today! Sign one now to be on the safe side) • Emailed Tauana [email protected] a scan or photo of the photo page of your passport • Emailed Tauana your home address (this can be your Harvard or your real home address)
• By 1:00 pm on Tuesday 2 February: – All enrolled students should sign up in groups of 2 to present one of the listed papers, no later than The first student paper presenta on will be on Thursday February 11 – Student paper presenta ons will be every Thursday a er that, except for February 18 and April 14, when our guest lecturers will lead paper discussion OEB51 Lecture 2 – Porifera, Ctenophora Informa on we will be considering for each major taxon (“phylum”)
• General introduc on • Body plan – Body wall and muscle structure – Nervous system – Diges ve system – Excretory system • Reproduc on • Development (embryonic and post-embryonic) • Ecology • Systema cs and phylogene c rela onships • Fossil record (some mes) • Interes ng current research Ctenophora Animals Porifera Placozoa Cnidaria Xenacoelomorpha Parahoxozoa Ambulacraria Echinodermata Hemichordata Planulozoa Deuterostomia Cephalochordata Chordata Urochordata Bilateria Craniata Chaetognatha Bryozoa Entoprocta Cycliophora Nephrozoa Annelida Trochozoa Mollusca Nemertea Brachiopoda Phoronida Spiralia Gastrotricha Protostomia Platyhelminthes Gnathostomulida Micrognathozoa Gnathifera Rotifera Nucleariida Orthonectida Fungi Dicyemida Opisthokonta Filasterea Priapulida Ichthosporea Scalidophora Holozoa Animals Loricifera Choanoflagellata Kinorhyncha Nematoida Nematoda Ecdysozoa Nematomorpha Tardigrada Panarthropoda Onychophora Arthropoda PORIFERA Sponges Ctenophora Animals Porifera Placozoa Cnidaria Xenacoelomorpha Parahoxozoa Ambulacraria Echinodermata Hemichordata Planulozoa Deuterostomia Cephalochordata Chordata Urochordata Bilateria Craniata Chaetognatha Bryozoa Entoprocta Cycliophora Nephrozoa Annelida Trochozoa Mollusca Nemertea Brachiopoda Phoronida Spiralia Gastrotricha Protostomia Platyhelminthes Gnathostomulida Micrognathozoa Gnathifera Rotifera Nucleariida Orthonectida Fungi Dicyemida Opisthokonta Filasterea Priapulida Ichthosporea Scalidophora Holozoa Animals Loricifera Choanoflagellata Kinorhyncha Nematoida Nematoda Ecdysozoa Nematomorpha Tardigrada Panarthropoda Onychophora Arthropoda Porifera
• Sessile • Lack “ ssues” but have many different cell types • Feed with choanocytes – feeding cells that draw water through the sponge body and filter out food par cles – Food par cles are ingested by phagocytosis (specific) or pinocytosis (non-specific) • Filter feeders generally – Some are carnivorous: trap prey with hook-shaped spicules – Some are symbio c with bacteria and zooxanthellae (photosynthe c algae) • Different sponge morphologies might be adap ve for different movement pa erns of water • Most are marine (about 8300 spp.) but some are freshwater (about 50 spp.) • They have a suppor ng skeleton made of spicules, (o en) an elas c network of fibers in the outer layers, and an extracellular matrix that contains collagen • Reproduc on can be sexual or asexual (budding or fragmenta on) • Sponges can live a long me! – Largest specimens of Xestospongia muta es mated as 2300 years old (McMurray et al 2008) Sponges have very varied habitats
Encrusting sponges competing for substrate
An erect sponge in a tropical environment Major sponge taxa
Phylum Porifera
Class Calcarea Subclass Calcinea Order Clathrinida Subclass Calcaronea Order Leucosoleniida Order Lithonida
Class Hexactinellida Silicea Subclass Amphidiscophora Order Amphidiscosida Subclass Hexasterophora Order Hexactinosida Order Lyssacinosida
Class Demospongiae Subclass Tetractinomorpha Order Lithistida Order Astrophorida Order Hadromerida Order Spirophorida Subclass Ceractinomorpha Order Agelasida Order Dendroceratida Order Dictyoceratid Order Halichondrida Order Haplosclerida Order Poecilosclerida Order Verongida Class Homoscleromorpha Order Homosclerophorida
FIGURE 1: Summarized view on the current knowledge of molecular phylogenetic relationships of sponges as dis- cussed in the text. Dashed lines indicate branches of particularly uncertain molecular hypotheses.
120 · Zootaxa 1668 © 2007 Magnolia Press LINNAEUS TERCENTENARY: PROGRESS IN INVERTEBRATE TAXONOMY Poriferan Body Structure
• The outer layer is a single cell layer called the pinacoderm – The cells that make it up are BODYpinacocytes STRUCTURE – It contains dermal pores (surrounded by mul ple cells) or os a (a pore made of a single cell) • Outer layer of cells (single-cell layer): pinacoderm (pinacocytes) • The inner layer is a single cell layer called the choanoderm • Dermal pores (surrounded by multiple cells) or ostia (ostium in singular) (single cell pore): – The cells that make it up are incurrent currents choanocytes • In between the • Inner surface pinacoderm(single-cell layer): and the choanodermchoanoderm (choanocytes is a substance called the ) • Mesohyl between pinacoderm and choanoderm: secretes the skeletal elements mesohyl(organic: collagenous; and inorganic: spicules). The mesohyl contains amebocytes – This secretes skeletal elements (collagenous (organic) and spicules (inorganic)) – The mesohyl contains another cell type called amebocytes
Poriferan Cell Types
• Cells that line surfaces – Pinacocytes – Porocytes – Choanocytes • Cells that secrete the skeleton – Amoeboid cells of various kinds (collencytes, lophocytes, spongocytes) – Sclerocytes (secrete spicules) • Contrac le cells – Myocytes • Archaeocytes – pluripotent and to potent • Spherulous cells – contain secondary metabolites Choanocyte ultrastructure Formation of a triaxon calcareous spicule Sclerocytes
Spongocytes secreting collagen fibrils in a demosponge
Sclerocite of a demosponge with a rudimentary siliceous spicule extending between two vacuoles
Lophocyte • Support (skeletal elements): • Organic: collagenous (spongin in Demospongiae) • Inorganic • Siliceous (hydrated silicon dioxide) • Calcareous (calcium carbonate in the form of calcite or aragonite) Sponges are the only animals that use hydrated silica as a skeletal material Sexual reproduction in sponges Most sponges are hermaphroditic, but they produce sperm and eggs at different times Cross-fertilization is probably the norm Mature sperm cells and oocytes are released into the environment through the aquiferous system Fertilization usually takes place internally or in the water column A planktonic larva forms
Sperm follicle containing mature spermatozoa
Oocyte phagocytizing a trophocyte Zoologica Scripta et al. Ancestral sexuality and reproductive condition in sponges A. Riesgo
Heterochone calyx Inferring the ancestral sexuality and reproductive condition Aphrocallistes vastus Oopsacas minuta in sponges (Porifera) Lophocalyx profundum Rosella nodastrella Mertensia ovum ANA RIESGO,MARTA NOVO,PRASHANT P. SHARMA,MICHAELA PETERSON,MANUEL MALDONADO & Hydra vulgaris GONZALO GIRIBET Nematostella vectensis Clathrina clathrus Sycon coactum Oscarella lobularis Corticium candelabrum Rhopaloeides odorabile Hippospongia lachne
Submitted: 5 July 2012 Riesgo, A., Novo, M., Sharma, P.P., Peterson, M., Maldonado, M., Giribet, G. (2014). Hexadella pruvoti Accepted: 3 July 2013 Inferring the ancestral sexuality and reproductive condition in sponges (Porifera). —Zoolog- Aplysina fulva Aplysina aerophoba doi:10.1111/zsc.12031 – ica Scripta, 43, 101 117. Aplysina cavernicola Considerable diversity abounds among sponges with respect to reproductive and develop- Chondrosia reniformis mental biology. Their ancestral sexual mode (gonochorism vs. hermaphroditism) and repro- Halisarca dujardini Chondrilla nucula ductive condition (oviparity vs. viviparity) however remain unclear, and these traits appear to Chondrilla australiensis have undergone correlated evolution in the phylum. To infer ancestral traits and investigate Calyx podatypa this putative correlation, we used DNA sequence data from two loci (18S ribosomal RNA Haliclona sarai Amphimedon erina and cytochrome c oxidase subunit I) to explore the phylogenetic relationships of 62 sponges Amphimedon compressa whose reproductive traits have been previously documented. Although the inferred tree Xestospongia muta topologies, using the limited data available, favoured paraphyly of sponges, we also investi- Haliclona xena gated ancestral character-state reconstruction on a phylogeny with constrained sponge Siphonochalina siphonella monophyly. Both parsimony- and likelihood-based ancestral state reconstructions indicate Haliclona oculata that viviparity (brooding) was the likely reproductive mode of the ancestral sponge. Chalinula molitba Haliclona elegans Hermaphroditism is favoured over gonochorism as the sexual condition of the sponge ances- Scopalina ruetzleri tor under parsimony, but the reconstruction is ambiguous under likelihood, rendering the Eunapius fragilis ancestry of sexuality unresolved in our study. These results are insensitive to the constraint Spongilla lacustris of sponge monophyly when tracing the reproductive characters using parsimony methods. Acanthella acuta However, the maximum likelihood analysis of the monophyletic hypothetical tree rendered Dictyonella incisa Dragmacidon lunaecharta gonochorism as ancestral for the phylum. A test of trait correlation unambiguously favours Ancestral sexuality and reproductive condition in sponges A. Riesgo et al. Thenea muricata the concerted evolution of sexuality and reproductive mode in sponges (hermaphroditism/ Geodia barretti viviparity, gonochorism/oviparity). Although testing ecological hypotheses for the pattern of Axinella verrucosa Axinella damicornis A sponge reproduction isB beyond the scope of our analyses, we postulate that certain physio- Agelas clathrodes logical constrains might be key causes for the correlation of reproductive characters. Agelas oroides Correspondence author: Ana Riesgo, Museum of Comparative Zoology, Department of Organis- Placospongia intermedia Cliona viridis mic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, Spirastrella cunctatrix USA. E-mail: [email protected] Tethya aurantium Ana Riesgo, Museum of Comparative Zoology, Department of Organismic and Evolutionary Biol- Tethya sp. nov. 2 Tethya sp. nov. 1 ogy, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA and Centro de Estudios Tethya citrina Avanzados de Blanes (CEAB-CSIC), Department of Marine Ecology, Acces a la Cala St. Francesc, Halichondria okadai Hymeniacidon perlevis 14, 17300, Blanes, Girona, Spain. E-mail: [email protected] Suberites domuncula Marta Novo and Prashant P. Sharma, Museum of Comparative Zoology, Department of Organismic Hermaphroditic Oviparous and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA. Mycale laxissima Asbestopluma occidentalis Email: [email protected], [email protected] Gonochoristic Crambe crambe Viviparous C Michaela Peterson, Museum of Comparative Zoology, Department of Organismic and Evolutionary Microciona prolifera Biology, Harvard University,D 26 Oxford Street, Cambridge, MA, 02138, USA and Cambridge Lissodendoryx colombiensis Rindge and Latin High School, 459 Broadway, Cambridge, MA, 02138, USA. Email: scruffy5@ Tedania ignis myway.com Manuel Maldonado, Centro de Estudios Avanzados de Blanes (CEAB-CSIC), Department of Unknown Marine Ecology, Acces a la Cala St. Francesc, 14, 17300, Blanes, Girona, Spain. Email: maldonado Maximum likelihood @ceab.csic.es Gonzalo Giribet, Museum of Comparative Zoology, Department of Organismic and EvolutionaryFig. 4 Maximum likelihood ancestral character-state reconstruction for both sexuality and reproductive condition. Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA. Email: ggiribet@ g.harvard.edu
Fig. 1 Reproductive strategies in Porifera: —A–C: sexual mode, —C–D: reproductive condition. —A. Gonochorism in Raspaciona aculeata.binary reproductive characters, hermaphroditism and vivi- The correlation was weakly upheld under an alternative ªOocytes2013 Theare Norwegian homogenously Academy of Science distributed and Letters, throughout43, 1, January 2014, theentire pp 101–117 mesohyl (scale bar 100 lm). —B. Gonochorism in Axinella damicornis. The101parity and gonochorism and oviparity (likelihood tree topology (Figs 5 and 6) with enforced sponge mono- spermatic cysts (black arrowheads) occupy large areas of the sponge mesohyl (scale bar 100 lm). —C. Hermaphroditism and viviparity inratio = 15.332; P = 0.0040). The reduced 54-taxon data set phyly (likelihood ratio = 8.741; P = 0.0678). However, Corticium candelabrum. Oocytes (white arrowhead) and spermatic cysts (black arrowheads) co-occur with early-stage embryos (black arrows)wherein reproductive data were available for at least one exclusion of terminals with complete lack of reproductive — (scale bar 500 lm). D. Brooding (viviparity) in Niphates erecta. Embryos (black arrows) and larvae (white arrows) are incubated in fi fi brooding chambers. character in all terminals similarly favoured a signi cant cor- character data recovered a strongly signi cant correlation relation between the two traits (LR = 14.533; P = 0.0057). (likelihood ratio = 16.770; P = 0.0021). internal fertilisation, broadcast spawning or brooding (Kerr markers included a fragment of the mitochondrial gene et al. 2011). We defined sexuality as a binary character, cytochrome c oxidase subunit I (COI) and one nuclear gonochorism vs. hermaphroditism (Fig. 1). As the coding ribosomal gene (complete or partial 18S rRNA). The com-ª 2013 The Norwegian Academy of Science and Letters, 43, 1, January 2014, pp 101–117 109 of sexuality and reproductive condition as binary characters plete 18S rRNA (ca. 1.8 kb) was amplified in three overlap- can be difficult in some instances due to limiting published ping fragments of about 950, 900 and 850 bp each, using data, we took into account only long-term studies, in which primer pairs 1F–5R, 3F–18Sbi and 18Sa2.0–9R (primer sex reversals in the sponges were not reported. In some sequences are listed in Table S2). Additional primer pairs species, when most individuals (even if not all) in the were used when the previous pairs failed to amplify the studied population exhibited both sexes, we coded them as fragment: 1F–4R internal to 1F–5R, 3F-5R internal to 3F– hermaphroditic, following Fell (1983). Similarly, when a 18Sbi, 4F-18Sbi internal to 3F–18Sbi, 4F–7R internal to population is predominantly hermaphroditic with few 3F–9R and 5F–9R internal to 4F–9R. A fragment of gonochoric individuals, the latter ones have been suggested 680 bp of the COI gene was amplified using the primers to be transitional stages of successive hermaphrodites. The LCO1490 and HCO2198, developed by Folmer et al. reproductive condition was also coded as binary, oviparity (1994). vs. viviparity (Fig. 1). Here, we considered all the broad- Polymerase chain reactions (PCRs) of 18S rRNA were casting species, regardless of fertilisation occurring inter- performed using AmpliTaq DNA polymerase (Applied Bio- nally or externally, as oviparous and all the brooding systems, Foster City, CA, USA) and COI with HotMaster species as viviparous, because discerning between ovovivi- Taq (5PRIME, Hamburg, Germany) and a GeneAmp Mul- parity and viviparity proved difficult in many instances. ticycler Ep gradient (Eppendorf, Hamburg, Germany). PCR programme for 18S rRNA involved an initial dena- DNA amplification turation step (5 min at 95 °C) followed by 35 or 40 cycles Total genomic DNA was extracted from tissue sample including denaturation at 95 °C for 30 s, annealing (rang- using the DNeasy Tissue Kit (Qiagen, Valencia, CA, ing from 40 °C to 50 °C) for 30 s or 1 min and extension USA), eluting twice with 100 lL of buffer. Molecular at 72 °C for 1 min, with a final extension step at 72 °C for
104 ª 2013 The Norwegian Academy of Science and Letters, 43, 1, January 2014, pp 101–117 Sponge Embryogenesis
Sponge embryos are hard to observe because they develop embedded in the mother. There may be many different forms of sponge embryogenesis. Sponges | IOB column, sometimes in large, synchronised sponsible for the production of biologically spawning events similar to the mass active compounds. The fact that structur- spawning of corals. In contrast, viviparous ally related substances were detected species brood embryos in their mesohyl in unrelated sponges, and that some of and release larvae into the seawater. For these are similar to known microbial com- the investigation of vertical transmission, pounds, points to a microbial origin for at small containers were placed on adult least some compounds. sponges to catch the released larvae (Fig- Due to the rapid rise of drug-resistant ures 3 and 4). Electron microscopy pic- pathogens and the continued emergence tures first indicated the presence of diverse of new infectious diseases, novel and bet- microbes in oocytes, embryos and larvae ter drugs are urgently needed. The major- of various sponge species. However, only ity of bioactive compounds isolated from the application of molecular methods al- sponges have medically and pharmaceuti- lowed the phylogenetic identification of cally relevant properties and some of them these microbes and revealed that the com- are already in preclinical and clinical plex microbial consortia of adult sponges trails. Activity has been found against a are also present in the respective repro- wide spectrum of pathogens and parasites ductive stages (for example Schmitt et al, including viruses, bacteria, fungi, and 2007). Vertical transmission is therefore protozoans (e.g. Plasmodium falciparum, a key mechanism by which the associa- the causative agent of malaria), although tion of sponges and microbial consortia is anti-cancer compounds currently attract maintained. the most attention. Other sponge-derived secondary metabolites including steroids A treasure trove of novel chemicals and saponins, bromotyrosine derivatives Sponges are an exceptionally rich source of and heterocyclic compounds display anti- novel and interesting bioactive compounds fouling activity. Biofouling affects human (reviewed by Blunt et al, 2008). These sub- activity through the growth of a variety of stances represent a diversity of chemical marine sessile organisms on fishing nets, classes including alkaloids, polyketides, hulls of ships, and cooling systems of power and terpenoids and are ecologically highly plants as well as other submersible struc- important for the animals. As sessile in- tures. All of these create enormous costs vertebrates with little morphological pro- and therefore environmentally-friendly tection, sponges rely on a chemical defence antifouling compounds are biotechnologi- system against predators such as fish and cally interesting substances, particularly turtles. Moreover, chemical warfare is also for industry. used against competitors, a mechanism Several approaches are currently used which is particularly important in habi- to recover novel and active substances tats like coral reefs where there is much from sponges and to gain access to the competition for space. Other compounds large amounts of these compounds required may act as anti-fouling agents to prevent for clinical trials. An increasingly common the overgrowth of the sponge by foreign strategy is the cultivation of sponge-asso- microbes or other invertebrates. However, it has long been a matter of debate as to Figure 4. Examples of sponge embryos within the mesohyl (A, B), and larvae (C, D). whether sponges themselves, their associ- PhotographsSponge Embryos and Larvae by N. Lindquist (University of North Carolina at Chapel Hill, USA). ated microorganisms, or possibly a con- certed interplay of both partners, are re-
Figure 3. A trap for catching sponge larvae on top of an adult sponge. Photograph by S. Schmitt.
Schmi (2009) Biologist Volume 56 Number 2, May 2009 | Biologist 77 Sponge Embryogenesis: Fixed Embryogenesis in Oopsacas minuta 107 Downloaded from http://icb.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on February 3, 2014
Fig. 1 Early cleavage stages in the development of O. minuta. (A) Oocyte showing depressions marking the first cleavage plane (arrows); scanning electron microscopy.Oopsacas (B) 2-cell stage. Blastomeres minuta have numerous filopodia, a dense nuclear region, and large lipid inclusions at the periphery. Thick section of an epoxy embedded embryo. (C and D) Scanning electron microscopy (SEM) is o en the best way to observe these embryos Stereomicrographs of 4-cell-stage embryos dissected out of the adult sponge. (C) shows rotational and (D) equatorial cleavage patterns. (E and F) Plastic sections of two 6-cell stage embryos. (E) shows an embryo with dark, lipid inclusions; (F) shows a section through 3 of the 6 cells of another embryo. One of the cells appears to have 2 nuclei (arrow and BUT we couldn’t say anything about live development un l recently… arrowhead). The fact that epoxy penetrates between the blastomeres suggests there is no cytoplasmic connection between cells at this stage. (G–I, K and L) 16- and 32-cell-stage embryos. (G) and (H) show 2 views of plastic embedded embryos. (I) and (L) are scanning electron micrographs of an embryo dissected out of the parent sponge. (J) is a Leys et al. (2007) Integr. Comp. Biol. transmission electron micrograph of the 2 blastomeres from (B). (K) shows a transmission electron micrograph of the blastomeres from the embryo in (H). Blastomeres are uniformly sized and are tenuously held together by vast numbers of filopodia at their surfaces (L, arrow). Scale bars: (A, J, and K), 10 mm; (B–I and L), 20 mm. li, lipid inclusion; nu, nucleus; y, yolk.
that the macromeres become elongate and gradually fill produce filopodia that interdigitate and appear to the center of the blastula (Figs. 2A–D and 3B). Once the fuse (Fig. 3C, upper right). All embryos after this stage embryo is solid, lamellipodia extend from the apical consist of a single multinucleate tissue—the incipient surface of the macromeres to envelop the micromeres trabecular reticulum of the future larva and adult (Fig. 3B–F), thereby forming the outer epithelium of sponge—that envelops the micromeres (Figs. 3E, F the embryo. Furthermore, the macromeres also and 4A–F). Moreover, this macromere-derived Sponge Embryogenesis: Live!
Chondrilla nucula
These were found with early stage embryos in the wild Observa ons consistent with internal fer liza on Sidriet al. (2007) Invert Biol CTENOPHORA The comb jellies
An Antarctic lobate ctenophore feeding upon krill
http://www.youtube.com/watch?v=AeDsSH2lCCE Ctenophores (comb jellies)
Beroe sp.
Mnemiopsis leydei Ctenophora Animals Porifera Placozoa Cnidaria Xenacoelomorpha Parahoxozoa Ambulacraria Echinodermata Hemichordata Planulozoa Deuterostomia Cephalochordata Chordata Urochordata Bilateria Craniata Chaetognatha Bryozoa Entoprocta Cycliophora Nephrozoa Annelida Trochozoa Mollusca Nemertea Brachiopoda Phoronida Spiralia Gastrotricha Protostomia Platyhelminthes Gnathostomulida Micrognathozoa Gnathifera Rotifera Nucleariida Orthonectida Fungi Dicyemida Opisthokonta Filasterea Priapulida Ichthosporea Scalidophora Holozoa Animals Loricifera Choanoflagellata Kinorhyncha Nematoida Nematoda Ecdysozoa Nematomorpha Tardigrada Panarthropoda Onychophora Arthropoda Ctenophora • Outer (ectoderm) and inner (endoderm) ssue layers separated by a cellular mesenchyme – Musculature made of mesenchymal cells • Biradial symmetry: oral-aboral axis • Adhesive exocyto c cells called colloblasts • The gastrovascular cavity (“gut”) is the only “body cavity” – The gut ends in two small anal pores on the aboral side • No discrete respiratory, excretory or circulatory systems • Nervous system: diffuse nerve net or plexus – More specialized than the cnidarian nervous system – Apical sense organ • No sessile life stage (but one sessile species exists) • Eight rows of ciliary plates called combs or ctenes – The comb row movement is controlled by the unique apical sense organ • Some adults and most juveniles have a pair of long tentacles that can o en be retracted into sheaths • Most are hermaphrodi c and self-fer le – Characteris c cydippid larval stage Ctenophoran life • Important marine predators (1 parasi c species known) – Haeckelia rubra incorporates nematocysts (s nging cells) from cnicadian prey • 242 described species – Probably many more undescribed • Most species are planktonic (surface to 3000 m) – A few are benthic – 1 is sessile (Tjalfiella) • Adult sizes range from a few mm to more than 2 m • There is a modest fossil record CTENOPHORA (COMB JELLIES)
• Biradial symmetry? • Through gut? • Apical organ (sensory/locomotory) • Eight rows of ctenes (comb plates) • Adhesive prey-capturing cells (colloblasts) • Tentacles • Nervous system with acetylcholinesterase synapses
BEROE SPP.
Transmission electron microscopy (TEM) revealed a putative two-dimensional photonic crystal composed of an enormous number of tightly packed cilia within the combs of Beroe cucumis. A photonic crystal is a rare type of color-producing structure, composed of a regularly repeating structure with dimensions a fraction of the wavelength of light, complex optical properties and large commercial potential.
Welch, V. L., Vigneron, J. P. & Parker, A. R. The cause of colouration in the ctenophore Beroë cucumis. Current Biology 15, R985-R986 (2005). Ctenophore Body Plan
Byrum & Mar ndale (2004) Gastrula on Ctenophore Embryogenesis: Schema c
Byrum & Mar ndale (2004) Gastrula on Ctenophore Embryogenesis & Gastrula on: Snapshots
308 Dev Genes Evol (2008) 218:307–319
Ectoderm
Endoderm
Mesoderm
Fig. 1 Ctenophore body plan and development. a M. leidyi cydippid is present in both the ciliaByrum as well & Mar ndale (2004) as the nervous system.Gastrula on In; Pang & Mar ndale (2008) Dev Genes this aboral Evol (∼24 h postfertilization) lateral view, with the aboral pole at top and view, cilia from the comb plates, ciliary groove, and apical organ are oral pole at bottom. b Same animal, aboral view, in the focal plane of visible, as well as the subepidermal nerve net and nerve fibers in the the tentacle bulb. Anal pores are visible in a different plane, so are tentacular mesoglea. e–l Differential interference contrast (DIC) time- drawn here in yellow. The tentacular axis runs through the tentacles lapse images of a M. leidyi embryo from 2 h postfertilization to 12 h and the sagittal axis is perpendicular to this. c M. leidyi cydippid fixed postfertilization. The asterisk marks the position of the blastopore and and incubated with Alexa-488-conjugated phalloidin (Invitrogen) and oral pole. e′–l′ Schematic diagram of ctenophore development based imaged with a confocal laser scanning microscope (Zeiss). Shown in on DIC images (e–l) as well as drawings of Metschnikoff (1885). The green is filamentous actin, visualizing the musculature as well as the yellow cells represent the endodermal macromeres and their deriva- actin pegs surrounding the mouth and pharynx. Aboral is at the top tives, and the blue cells are the ectodermal descendents of aboral and oral at the bottom. d M. leidyi cydippid fixed, incubated with anti- micromeres. The red cells are the oral micromeres that give rise to tyrosine tubulin (Sigma) and visualized with an Alexa546-conjugated muscle and mesenchyme secondary stain (Invitrogen). Shown in red is stabilized tubulin, which as biradially symmetrical. Ctenophores are composed of pole, this being the site where polar bodies are given off two epithelia, the epidermis of ectodermal origin and the and the site of first cleavage. The macromeres then buckle gastrodermis that lines the gastrovascular system, which is inward through mechanisms that are not fully understood of endodermal origin. However, below the epidermis lies (Fig. 1f,f′). Before the aboral micromeres completely the mesoglea, a highly gelatinous layer filled with fibers as surround the macromeres, the macromeres divide asym- well as muscle, nerve, and mesenchymal cells. Unlike metrically to give rise to a set of micromeres at the oral pole cnidarians and sponges, ctenophores possess definitive (Fig. 1g,g′). These oral micromeres, the mesodermal cells, muscle cells of endodermal origins (Martindale and Henry enter the blastocoel and move upward between the macro- 1999). These muscle cells have no epithelial component, as meres until they reach the inner surface of the aboral in cnidarians, and are located under the integument ectoderm (Fig. 1h–k,h′-k′) and give rise to the musculature (including the pharynx) and in the mesoglea, including and mesenchymal derivatives. Meanwhile the ectoderm the tentacles (Fig. 1c). The nervous system is composed of continues to spread over the macromeres, meeting at the asubepidermalnervenet,withneuronsconcentrated oral pole, and then invaginates to form the pharynx around the mouth and apical organ; there are also nervous (Fig. 1h–k,h′–k′). The macromeres, now in the interior of elements in the mesoglea, with high concentrations in the the embryo, form the gut and endodermal canal system. tentacles, and near the base of the endoderm (Fig. 1d; Differentiation of the ectoderm also occurs at this time, Hernandez-Nicaise 1991). with the formation of the eight comb rows and the apical Ctenophore development has been well described and is organ at the aboral pole (Fig. 1k,k′). The tentacle apparatus highly stereotyped up to cydippid stages (Chun 1880; forms by an ectodermal thickening and invagination, and Metschnikoff 1885; Reverberi and Ortolani 1965), with a eventually, the tentacles grow out through the tentacle recent study detailing the fate map using intracellular sheathes (Fig. 1l,l′). The tentacles are composed of an outer tracers (Martindale and Henry 1999). Gastrulation begins epidermis, including the highly adhesive colloblast cells, at about 3 h after first cleavage, when the aboral micro- which cover the core made up of a central neural strand and meres begin to undergo epibolic movements orally that muscle fibers imbedded in the mesoglea. envelop the macromeres (Fig. 1e,e′). Like cnidarians but In contrast to the other nonbilaterian metazoans (cnidar- unlike all other metazoans, gastrulation occurs at the animal ians, poriferans, placozoans), there has been very little work Ctenophore Embryogenesis: Live
No ce that cleavage is total, but the cleavage furrow starts at one side of the cell every me.
This type of cleavage is known from some ctenophores and cnidarians.
Pleurobrachia sp. Center for Cell Dynamics To request a spot in the course…
• Email the following informa on TODAY to Tauana Cunha [email protected] – Name – Email address – Concentra on – Year – Mo va on for taking the course (max 4 sentences) • We have to have the informa on above before MIDNIGHT on Thursday January 28 • We will email accepted students by 12:00 noon on Friday January 29 • If you are serious about taking this course, be prepared to provide a scan (PDF) of the photo page of your passport on FRIDAY of this week – We need this to request a collec on permit in Panama.