SPC Beche-de-mer Information Bulletin #19 – January 2004 43 abstracts,abstracts, publications,publications, workshopsworkshops && meetingsmeetings beche-de-merbeche-de-mer Note from Editor:Abstracts have been provided by the authors, and have been reproduced as is. Towards an understanding of the shallow-water holothuroid (Echinodermata: Holothuroidea) fauna of the western Indian Ocean Yves Samyn Assisting Academic Staff Free University Brussels (VUB), Unit for Ecology & Systematics (ECOL) Pleinlaan 2 - 1050 Brussel - Belgium Source: Summary of PhD The study of the Holothuroidea, commonly known loans of specimens from museums worldwide. In as sea cucumbers, started some 23 centuries ago the course of the construction of this species inven- when Aristotle defined them as "a kind of motion- tory, my colleagues and I discovered several species less marine organisms". Only in the mid sixteenth and one genus new to science. We, however, did not century were holothuroids recognised as animals blindly follow the standing biological classifications per se. Nowadays, Holothuroidea is firmly recog- when describing our findings. Au contraire, while nised as one of the five extant classes of echino- constructing the species lists we took great care to derms. Currently some 1600 species are described; critically question the employed classifications. This these occur from the intertidal to the deep ocean attitude resulted in the taxonomic revision of the trenches and from the polar to the tropical regions. Holothuria subgenus Mertensiothuria and of the holo- thuriid genus Labidodemas. Interestingly, the type The ultimate aim of this dissertation is to under- species of the latter genus revealed itself as a cryptic stand the shallow-water holothuroid biodiversity of species. We were rewarded with the discovery of the western Indian Ocean, the area stretching from two additional new species. Suez to Cape Town and from the East African coast (Red Sea and Persian Gulf included) to 65 degrees Throughout this process, the historical opinions to- East. To attain this goal, several expeditions to two wards holothuroid taxonomy and systematics were contrasting regions of the western Indian Ocean (the never denied. This approach enabled us to revive tropical coast of Kenya together with Pemba Island methodically ignored characters such as the ossicles in northern Tanzania and the subtropical coast of from the musculature. These characters proved not KwaZulu-Natal in the northeast of the Republic of only diagnostic in the recognition of taxa, but also South Africa) were undertaken. The purpose of were informative in terms of recovery of phyloge- these was to assemble a representative collection of nies. By using our rejuvenated insights into such species. (and other) characters we were able to construct a large, morphology-based dataset, which allowed An extensive part of this dissertation is concerned the recovery of the phylogeny of the Holothuriidae, with the construction of a reliable and up-to date the family best represented in this work. This cladis- faunistical list of the holothuroid fauna of these two tic analysis not only revealed that Labidodemas was case areas. The faunistics of the rest of the western indeed monophyletic (as suggested by our earlier Indian Ocean was filled in with the aid of important systematic revision), but also allowed us to state collections from the Seychelles and Inhaca (which that it has arisen from within the (now paraphyletic) were deposited as largely unidentified material in genus Holothuria. As such, Labidodemas is evolution- the collection of the Royal Africa Museum, ary much younger than generally assumed. Our Tervuren, Belgium), with detailed study of virtually phylogenetic studies further suggest a close rela- all the available literature as well as with numerous tionship between the genera Actinopyga, Bohadschia 44 SPC Beche-de-mer Information Bulletin #19 – January 2004 and Pearsonothuria, but unfortunately the recovered biodiversity by means of cluster analysis on several support proved low. Future studies (see also annex b-diversity coefficients and parsimony analyses of on CD Rom) will have to decide whether a new clas- endemicity. These analyses showed that the investi- sification of the Holothuriidae is desired. gated holothuroid fauna of the western Indian Ocean is non-homogeneous and best split into several bio- Taking all these caveats into account, we finally suc- geographic units. These can be explained with (i) ceeded to construct the wanted faunistical list of the species' dispersion ability, (ii) the prevalent current Holothuroidea from the western Indian Ocean. This patterns and (iii) the recent geological history. list was then further used to analyse the patterns of Phylogeny of the Holothuriidae (Echinodermata: Holothuroidea) inferred from morphology W. Appeltans Source: MSc thesis, Vrije Universiteit Brussel. 94 p. 2002 Despite the efforts of numerous notable taxonomists, tube feet. Moreover, often ignored body parts such the taxonomy and systematics of the grand family as longitudinal muscles, cloacal muscles and anal Holothuriidae (Holothuroidea: Aspidochirotida) re- papillae were examined for the presence of ossicles. main vague for some groups. As such, a cladistically Preliminary analysis revealed that for the synallac- substantiated phylogeny based upon clearly de- tid genus Mesothuria, the species used as outgroup fined morphological characters can bring insights (e.g. M. sufflava) clustered in the ingroup. As it is into the evolution of the holothuriids. Thus, here I here argued that this is the result of erroneous iden- present a phylogeny of the group based on morpho- tification, Mesothuria was omitted as outgroup taxon. logical characters. Cladistic analysis was performed On the other hand, two genera of the Stichopodidae by an heuristic search under the maximum-parsi- successfully lent themselves as outgroup. For the mony optimality criterion. 27 ingroup taxa, repre- Holothuriidae, the monophyly of the genera senting all currently recognised genera and subgen- Actinopyga, Bohadschia and Labidodemas was con- era and 6 outgroup taxa, belonging to the closely re- firmed. Labidodemas, however, clustered in the para- lated Stichopodidae and deep-sea Synallactidae, phyletic lineage Holothuria. The enigmatic genus were scored for a total of 68 characters concerning Pearsonothuria turned out to be the sister group of gross external and internal morphology and ossicle Actinopyga. From the resulting phylogeny, infer- assemblage in the body wall, the tentacles and the ences on character evolution are made. Contribution to the study of the relations between fish of the family of Carapidae and their holothurian hosts Eric Parmentier Email: [email protected] Source: PhD Thesis, Université de Liège, Laboratoire de Morphologie Fonctionnelle et Évolutive, 4000 Liège Belgium Aremarkable example of association between ani- The morphofunctional study of the bucco-pharyn- mals is this one of Carapidae fish (Ophidiiformes) geal apparatus, the stable isotopes of carbon (∂13C) and different invertebrates. These fish are known as and nitrogen (∂15N), the stomach content determina- pearlfish. The origin of this name would be the dis- tions and the study of otolith increments allow to covery of dead carapid fish, paralysed and com- define clearly the commensal behaviour of Carapus pletely covered in mother of pearl in the inner face and the parasitic behaviour of Encheliophis, the latter of the valves of the shell of certain oysters (Ballard eating the gonads and the respiratory trees. 1991). The fish belonging to the genus Onuxodon, Carapus and Encheliophis are capable of penetrating and At the tenuis stage, the Carapus larvae leave the residing inside different invertebrates such as sea cu- pelagic area and may enter an holothurian host for cumbers, sea stars, bivalve molluscs and ascideans. the first time. Once inside the sea cucumber, the fish undergo a drastic metamorphosis with a spectacu- In this thesis, a multidisciplinary approach was re- lar 50-60 per cent reduction of the body length. The alised to understand the biology of the Carapini study of the larval development (axial skeleton and (Carapus and Encheliophis) fish living inside holothuri- otoliths) reveals that the association between the ans and to highlight the various factors which make fish and the host is obligatory as the fish needs its these associations possible. host to initiate its metamorphosis. However, the SPC Beche-de-mer Information Bulletin #19 – January 2004 45 host is used as a black box and not as a source of food. Three Carapini fish (C. boraborensis, C. homei and E. gracilis) have also show the ability to emit sounds and the structures (skeletal, muscular and of the swim bladder) responsible were identified and de- scribed. In the framework of the present study, sounds are not likely to be used by the fish to iden- tify the presence of an eventual congener in the holothurian before penetration but are produced in the presence of the congener, inside the holothurian. Indeed, no sound has been recorded while the fish were approaching the potential host or while pene- trating the unoccupied holothurian. The sea cucumber cloaca is located close to the cur- rent of water exhaled, coming from the respiratory trees. Two strategies have then been observed. (1) The fish can penetrate into the host head first, pro- pelling itself by violent strokes of the tail; (2) it places its head at the entry to the host