1 Design and relationships.- 1.1 Introduction.- 1.2 The orders: morphology and life cycles.- 1.2.1 Stauromedusae.- 1.2.2 Coronatae.- 1.2.3 Semaeostomeae.- 1.2.4 Rhizostomeae.- 1.3 Relationships and origins of the class and orders.- 2 Locomotion.- 2.1 Introduction.- 2.2 Mesoglea.- 2.2.1 Fibre composition.- 2.2.2 Mechanics.- 2.3 Muscle.- 2.3.1 General muscular anatomy.- 2.3.2 Fine structure of muscles.- 2.3.3 Physiological properties of muscles.- 2.4 Sensory receptors.- 2.4.1 Structure of the marginal sense organs.- 2.4.2 Photoreception.- 2.4.3 Equilibrium reception.- 2.4.4 Other sensory responses.- 2.5 Nervous system.- 2.5.1 Nervous system of medusae.- 2.5.2 Marginal centres.- 2.5.3 Structure and function of the motor nerve net.- 2.5.4 Diffuse nerve net.- 2.5.5 Nervous system of polyps.- 2.5.6 Transmitters.- 2.6 Locomotion.- 2.6.1 Physical dynamics of swimming.- 2.6.2 Nervous control of swimming.- 2.6.3 Locomotion of polyps.- 2.6.4 Locomotion of planulae.- 3 Feeding.- 3.1 Introduction.- 3.2 Cnidae.- 3.2.1 Structure and classification.- 3.2.2 Formation and migration.- 3.2.3 Discharge.- 3.2.4 Toxins.- 3.2.5 Functions.- 3.3 Types of prey.- 3.3.1 Prey in diets of scyphomedusae.- 3.3.2 Prey of polyps.- 3.4 Contact with prey.- 3.4.1 Medusae encounter probabilities.- 3.4.2 Medusae attraction to prey.- 3.5 Feeding behaviour.- 3.5.1 Medusae prey capture.- 3.5.2 Polyp prey capture.- 3.5.3 Chemical induction of feeding.- 3.6 Feeding rates.- 3.6.1 Selection of prey types.- 3.6.2 Factors affecting feeding rates.- 4 Nutrition.- 4.1 Introduction.- 4.1.1 Units of intake.- 4.1.2 Dietary requirements.- 4.2 Digestion.- 4.2.1 Extracellular and intracellular digestion.- 4.2.2 Enzymes.- 4.2.3 Digestion rates.- 4.3 Circulation and translocation.- 4.3.1 Circulatory canals and ciliary currents.- 4.3.2 Endocytosis.- 4.3.3 Translocation.- 4.4 Uptake of dissolved organic material.- 4.5 Symbiosis.- 4.5.1 Identity and location of algal symbionts.- 4.5.2 Metabolic exchange between symbiont and host.- 4.5.3 Establishment and control of algal numbers.- 4.5.4 Ecological significance of symbiosis.- 5 Metabolism.- 5.1 Introduction.- 5.1.1 Definitions.- 5.1.2 Aerobic and anaerobic metabolism.- 5.2 Factors affecting oxygen consumption.- 5.2.1 Body size.- 5.2.2 Muscular activity.- 5.2.3 Food.- 5.2.4 Temperature.- 5.2.5 Oxygen availability.- 5.2.6 Effects of symbionts.- 5.3 Nitrogen excretion 131 5.3.1 Factors affecting rates of excretion.- 5.3.1 Factors affecting rates of excretion.- 5.4 Osmotic and ionic regulation.- 5.4.1 Water content.- 5.4.2 Buoyancy.- 6 Reproduction.- 6.1 Synopsis.- 6.1.1 Types of reproduction and trade-offs.- 6.1.2 Genetics.- 6.2 Gametogenesis.- 6.2.1 Gonad formation.- 6.2.2 Gamete production.- 6.2.3 Fertilization.- 6.3 Larval development.- 6.3.1 Embryogenesis and planulae.- 6.3.2 Brooding.- 6.3.3 Settlement including metamorphosis.- 6.3.4 Direct development.- 6.4 Polyp.- 6.4.1 Budding.- 6.4.2 Cysts including podocysts.- 6.4.3 Strobilation.- 6.5 Ephyra.- 7 Growth.- 7.1 Measurement of growth.- 7.1.1 Units.- 7.1.2 Methods.- 7.2 Organic composition of scyphozoa.- 7.3 Growth curves.- 7.3.1 Laboratory data.- 7.3.2 Field data.- 7.3.3 Life span.- 7.4 Starvation and regeneration.- 7.4.1 Degrowth and regrowth.- 7.4.2 Regeneration.- 7.5 Conversion efficiencies.- 7.6 Dietary requirements.- 7.6.1 Energy budget.- 7.6.2 Food supply.- 8 Physical ecology.- 8.1 Biomass.- 8.1.1 Measurement.- 8.1.2 Production.- 8.2 Mortality and adaptation to physical factors.- 8.2.1 Temperature.- 8.2.2 Salinity.- 8.2.3 Pollution.- 8.2.4 Oxygen.- 8.3 Depth.- 8.3.1 Vertical distribution.- 8.3.2 Diel migration.- 8.3.3 Changes with life cycle.- 8.4 Aggregation and horizontal migration.- 8.5 Zoogeography.- 9 Biological interactions.- 9.1 Predation.- 9.1.1 Natural predators: planktonic.- 9.1.2 Natural predators: benthic.- 9.1.3 Fisheries.- 9.1.4 Transparency and pigmentation.- 9.2 Parasites.- 9.2.1 Larval trematodes and cestodes.- 9.2.2 Hyperiid amphipods.- 9.3 Associations.- 9.3.1 Associations with fish.- 9.4 Bioluminescence.- 9.4.1 Anatomy of luminescent structures.- 9.4.2 Chemical basis of luminescence.- 9.4.3 Control of luminescence.- 9.4.4 Ecological significance.- 9.5 Trophic relationships.- 9.5.1 Impact on prey populations.- 9.5.2 Competition.- 9.5.3 Trophic levels.- Appendix: Classification of extant scyphozoa.- References.

A functional biology of scyphozoa

To investigate the evolution of cnidarian life cycles, data from the small subunit of the ribosome are used to derive a phylogenetic hypothesis for Medusozoa. These data indicate that Cnidaria is monophyletic and composed of Anthozoa and Medusozoa. While Cubozoa and Hydrozoa are well supported clades, Scyphozoa appears to be paraphyletic. Stauromedusae is possibly the sister group of either Cubozoa or all other medusozoans. The phylogenetic results suggest that: the polyp probably preceded the medusa in the evolution of Cnidaria; within Hydrozoa, medusa development involving the entocodon is ancestral; within Trachylina, the polyp was lost and subsequently regained in the parasitic narcomedusans; within Siphonophorae, the float originated prior to swimming bells; stauromedusans are not likely to be descended from ancestors that produced medusae by strobilation; and cubozoan polyps are simplified from those of their ancestors, which possessed polyps with gastric septa and four mesogleal muscle bands and peristomial pits.

/pdf/phylogeny-of-medusozoa-and-the-evolution-of-cnidarian-life-zfwsrhcl5l.pdf

Phylogeny of Medusozoa and the evolution of cnidarian life cycles

. A cladistic analysis of 87 morphological and life history characters of medusozoan cnidarians, rooted with Anthozoa, results in the phylogenetic hypothesis (Anthozoa (Hydrozoa (Scyphozoa (Staurozoa, Cubozoa)))). Staurozoa is a new class of Cnidaria consisting of Stauromedusae and the fossil group Conulatae. Scyphozoa is redefined as including those medusozoans characterized by strobilation and ephyrae (Coronatae, Semaeostomeae, and Rhizostomeae). Within Hydrozoa, Limnomedusae is identified as either the earliest diverging hydrozoan lineage or as the basal group of either Trachylina (Actinulida (Trachymedusae (Narcomedusae, Laingiomedusae))) or Hydroidolina (Leptothecata (Siphonophorae, Anthoathecata)). Cladistic results are highly congruent with recently published phylogenetic analyses based on 18S molecular characters. We propose a phylogenetic classification of Medusozoa that is consistent with phylogenetic hypotheses based on our cladistic results, as well as those derived from 18S analyses. Optimization of the characters presented in this analysis are used to discuss evolutionary scenarios. The ancestral cnidarian probably had a sessile biradial polyp as an adult form. The medusa is inferred to be a synapomorphy of Medusozoa. However, the ancestral process (metamorphosis of the apical region of the polyp or lateral budding involving an entocodon) could not be inferred unequivocally. Similarly, character states for sense organs and nervous systems could not be inferred for the ancestral medusoid of Medusozoa.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1744-7410.2004.tb00139.x

Cladistic analysis of Medusozoa and cnidarian evolution

We investigated the cytology of the oogenic cycle in two oviparous demosponges, Axinella damicornis and Raspaciona aculeata , during 2 consecutive years both by light and electron microscopy. Oocytes of both species were similar in their basic morphological features but differences were noticed in time required to complete oocyte maturation and mechanisms of acquisition of nutritional reserves. The oogenic cycle of A. damicornis extended for 7–8 months in autumn-spring, while that of R. aculeata did it for 3–5 months in summer-autumn. Yolk of A. damicornis was predominantly formed by autosynthesis. Oocytes endocytosed bacteria individually and stored them in groups in large vesicles. Bacteria were digested and lipidic material was added to the vesicles to produce a peculiar granular yolk hitherto unknown in sponges. Scarce cells carrying heterogeneous inclusions were observed in the perioocytic space, and were interpreted as putative nurse cells. Such cells were presumably releasing lipid granules to the perioocytic space. In contrast, large numbers of nurse cells were found surrounding the oocytes of R. aculeata . They transported both lipid granules and heterogeneous yolk bodies to the oocytes. R. aculeata also produced some of their yolk by autosynthesis. The involvement of nurse cells in the vitellogenesis of R. aculeata shortened the oocyte maturation, whereas a largely autosynthetic vitellogenesis in A. damicornis prolonged the duration of oogenesis.

Ultrastructure of oogenesis of two oviparous demosponges: Axinella damicornis and Raspaciona aculeata (Porifera).

The deepwater stauromedusan Lucernaria janetae n. sp is described from adult and juvenile specimens collected from the East Pacific Rise. Lucernaria janetae is the first species in the genus recorded from the Pacific Ocean, and differs from its congeners in size and morphology. Mitochondrial (16S) and nuclear (SSU) ribosomal gene sequences from L. janetae were analyzed with those of representative stauromedusan taxa to evaluate stauromedusan monophyly. Both genes recovered a strongly monophyletic Stauromedusae that is the sister group to all other medusozoans. Support of these hypotheses is robust to method of phylogenetic reconstruction and to outgroup selection, buttressing the argument that Stauromedusae should be recognized as the class Staurozoa. The molecular markers used here favor the same topology of relationships among our samples and clearly distinguished between two species, Haliclystus sanjuanensis and H. octoradiatus, that have been considered synonymous by many workers. A stable systematic ...

A New Deepwater Species of Stauromedusae, Lucernaria janetae (Cnidaria, Staurozoa, Lucernariidae), and a Preliminary Investigation of Stauromedusan Phylogeny Based on Nuclear and Mitochondrial rDNA Data

An ultrastructural study of the ovary of the sessible jellyfish, Haliclystus octoradiatus, indicates that it is fundamentally different from that of other scyphozoans and is the most structurally complex within the class. Oocytes develop within a series of spherical, sac-like ovarian follicles consisting of an enlarged intercellular space between two layers of subumbrellar gastrodermis. Developing oocytes are largely restricted to a thin germinal epithelium at the periphery of each follicle and gradually migrate toward the lumen as they mature. Individual oocytes are surrounded by early germ cells and follicle-like accessory cells of presumed somatic origin. Similar folliclelike cells have not been described in the Cnidaria previously. Vitellogenesis appears to involve the combined activity of the Golgi complex and associated rough endoplasmic reticulum. Ovarian morphology may be helpful in deciphering phylogeneitc relationships within the Cnidaria. © 1993 Wiley-Liss, Inc.

Ultrastructural study of the ovary of the sessile scyphozoan, Haliclystus octoradiatus (Cnidaria: Stauromedusae).

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Ultrastructural study of the ovary of the sessile scyphozoan, Haliclystus octoradiatus (Cnidaria: Stauromedusae).