The reproductive biology of nine species of aspidochirote holothurians from the major communities of the New Caledonian lagoon has been analysed. The data were obtained from monthly sampling from 1978 to 1982 of their populations on reef slopes and passes for Holothuria nobilis, H. fuscogilva, H. fuscopunctata and Thelenota ananas, in the inner lagoon for Stichopus variegatus, H. scabra and H. scabra versicolor and on reef flats for Actinopyga mauritiana, A. echinites and H. atra. The morphology and anatomy of the gonads and their annual cycle are described. The reproductive cycles, composed of the five phases of gonad growth, maturing, spawning, post-spawning and resting, were determined from the changes in the sexual stages, the gonad indices and the percentage of indeterminate sex. Three main reproductive patterns are recognized, annual cycles with spawning occurring during the warm season or during the cool season and a semiannual cycle. Other population parameters, such as the size of the mature oocytes, the mean size of the individuals at first sexual maturity, and absolute and relative fecundities were calculated and related to the mean size of the species, the taxonomy and the ecology. The reproductive strategies of the species show a gradient that is probably related to the stability of the biotopes, with smaller species living in the more intrable outer reef flats and larger species in deeper lagoon floors.

/pdf/reproductive-biology-of-the-holothurians-from-the-major-penvkfohz3.pdf

Reproductive biology of the holothurians from the major communities of the New Caledonian Lagoon

Sea cucumbers (Holothuridae and Stichopodidae) have been harvested commercially for at least 1,000 years. The world fisheries for sea cucumbers, however, are not well documented and in general are poorly managed. Depending upon the species exploited, there are two processing procedures for the sea cucumber product. Some species are eaten raw, while most commercial species are processed into a dry product called beche-de-mer or trepang. This dry product is exported to a central market such as Hong Kong and then re-exported to the consumers. In this review, recent statistics on the world sea cucumber fisheries, collected from different services, are detailed for each major fishing area. Case studies for each fishing area are also presented. Recent major changes in the Indo-Pacific fishery include the participation of new producer countries, the shift in the species being exploited, and an increase in the Chinese market. The expansion of the largely monospecific temperate North Pacific fisheries is also described. Statistics from Hong Kong, Singapore, Taiwan, and the Food and Agriculture Organization provide valuable information on the producer and importer countries. Particular attention is paid to the reciprocal trade of beche-de-mer between Hong Kong and Singapore. An evaluation of the world sea cucumber landings and beche-de-mer production is presented. Recent developments include an expansion of the Hong Kong market due to increased demand by China, the importance of Indonesia as a major world producer, and an increase in the fisheries of Tropical Pacific nations. This increase is best documented for New Caledonia and Fiji. Ways to improve the access and the reliability of the statistics for the sea cucumber fishery are discussed, as is the potential for management of artisanal fisheries.

A Review of Recent Developments in the World Sea Cucumber Fisheries

We review the literature on larval development of 182 asteroids, 20 crinoids, 177 echinoids, 69 holothuroids, and 67 ophiuroids. For each class, we describe the various larval types, common feature...

/pdf/larval-and-life-cycle-patterns-in-echinoderms-44wrij6d66.pdf

Larval and life-cycle patterns in echinoderms

The relationship between the five echinoderm classes has perplexed phylogeneticists for some time. Although each of the crinoids (C), asteroids (A), ophiuroids (O), echinoids (E) and holothuroids (H) are morphologically distinct, evidence from larval and adult morphology, molecular biology, and stratigraphy have failed to provide a single consensus solution. We have reviewed all available morphological and molecular data, added new data and reanalysed independent data sets individually and in combination, in order to resolve echinoderm class relationships. In total, we present 21 larval and 50 adult morphological characters, partial 28S-like large subunit rRNA gene data for 39 taxa and complete 18S-like small subunit rRNA gene data for 37 taxa. For a 5 taxon problem there are 105 possible rooted tree topologies, and yet we were consistently presented with three competing hypotheses when data sets were analysed both individually and in combination. The total evidence solution favoured (outgroup(C(A(O(E,H))))) although the alternative tree topology, (outgroup(C(O(A(E,H))))) was only one step longer and (outgroup(C((A,O),(E,H)))) was two steps longer. Only these three trees are serious contenders and the distribution of morphological characters suggests we should discount the solution placing ophiuroids as sister group to an asteroid+echinoid+holothurian clade. Thus we are left with (outgroup(C(A(O(E,H))))) and (outgroup(C((A,O),(E,H)))) as the two most plausible phylogenetic hypotheses. Our data showed high levels of phylogenetic signal and these trees best fit the available data.

The interrelationships of the echinoderm classes: morphological and molecular evidence

The ‘origin of larvae’ has been widely discussed over the years, almost invariably with the tacit understanding that larvae are secondary specializations of early stages in a holobenthic life cycle.



Considerations of the origin and early radiation of the metazoan phyla have led to the conclusion that the ancestral animal (= metazoan) was a holopelagic organism, and that pelago-benthic life cycles evolved when adult stages of holopelagic ancestors became benthic, thereby changing their life style, including their feeding biology.



The literature on the larval development and phylogeny of animal phyla is reviewed in an attempt to infer the ancestral life cycles of the major animal groups. The quite detailed understanding of larval evolution in some echinoderms indicates that ciliary filter-feeding was ancestral within the phylum, and that planktotrophy has been lost in many clades. Similarly, recent studies of the developmental biology of ascidians have demonstrated that a larval structure, such as the tail of the tadpole larva, can easily be lost, viz. through a change in only one gene. Conversely, the evolution of complex structures, such as the ciliary bands of trochophore larvae, must involve numerous genes and numerous adaptations.



The following steps of early metazoan evolution have been inferred from the review.



The holopelagic ancestor, blastaea, probably consisted mainly of choanocytes, which were the feeding organs of the organism. Sponges may have evolved when blastaea-like organisms settled and became reorganized with the choanocytes in collar chambers.



The eumetazoan ancestor was probably the gastraea, as suggested previously by Haeckel. It was holopelagic and digestion of captured particles took place in the archenteron. Cnidarians and ctenophores are living representatives of this type of organization. The cnidarians have become pelago-benthic with the addition of a sessile, adult polyp stage; the pelagic gastraea-like planula larva is retained in almost all major groups, but only anthozoans have feeding larvae.



Within the Bilateria, two major lines of evolution can be recognized: Protostomia and Deuterostomia. In protostomes, trochophores or similar types are found in most spiralian phyla; trochophore-like ciliary bands are found in some rotifers, whereas all other aschelminths lack ciliated larvae. It seems probable that the trochophore was the larval type of the ancestral, pelago-benthic spiralian and possible that it was ancestral in all protostomes. Most of the non-chordate deuterostome phyla have ciliary filter-feeding larvae of the dipleurula type, and this strongly indicates that the ancestral deuterostome had this type of larva.

Origin and evolution of animal life cycles

Descriptions of holothurian metamorphosis are based on data from the relatively specialized order Apoda. Metamorphosis for a relatively unspecialized aspidochirote, Stichopus californicus, is described here. Metamorphosis in Stichopus is characterized by the following features: the madreporic vesicle is a calcite secreting syncytium, not a coelom. Stichopus has no separate axocoel and no transient axial complex forms during metamorphosis. The buccal podia form from the water vascular ring, not the radii. The axes of bilateral larval symmetry and the pentaradial adult symmetry are congruent; therefore, the secondarily derived symmetry in holothurians is the pentaradial symmetry of the adult, as in the other extant echinoderms. No axial or visceral torsion occurs during metamorphosis. The enclosed ambulacra form in a manner distinct from that of the ophiuroids and echinoids. Perivisceral coelomic pores develop near the end of metamorphosis, and before the definitive anus forms. Assignment of holothurians with echinoids to the subphylum Echinozoa is discussed.

Metamorphosis of stichopus californicus (echinodermata: holothuroidea) and its phylogenetic implications

The major cytological stages of oogA©nesis in the holothurian Stichopus californicus are morphologi cally separated in distinct classes of tubules, the discrete anatomical units comprising the ovary. Primordial germ cells are in the connective tissue compartment of the go- nad basis. Mitotic oogonia are in the smallest and most anterior set of primary ovarian tubules. Oocytes in the early prophase stages of meiosis I are in secondary tu bules located more posteriorly. Diplotene oocytes occur in larger, more posterior secondary tubules. The most advanced oocytes are in the most posterior fecund tu bules. S. californicus oocytes bear nuage, a subcellular marker common to many germ line cells. The striking axial polarization of these oocytes, evident as the egg axis, is indistinguishable from the apical basal axial po larization in epithelial germ line cells. These axes are congruent throughout the developmental history of the oocyte. I present a model for the annual cycle of the S. californicus ovary and assessits application to other ho-

Scott Smiley

Papers

Metamorphosis of stichopus californicus (echinodermata: holothuroidea) and its phylogenetic implications

The Dynamics of Oogenesis and the Annual Ovarian Cycle of Stichopus californicus (Echinodermata: Holothuroidea)