Coelacanth Conservation Council

Coelacanth Conservation Council     

Early Growth Stages in Coelacanth Fishes

ALL known specimens of the Recent coelacanth fish, Latimeria, are large specimens (mostly more than 100 cm total length) and only one female with eggs has been recorded^1,2. Consequently, the ontogeny and the early growth stages of the Recent coelacanth are unknown. In the fossil record, one specimen of Holophagus (= Undina) from the Upper Jurassic of Solnhofen, southern Germany, has been recorded with two young coelacanths inside³. Watson has argued from this finding that the coelacanths are viviparous but it seems more reasonable to interpret this fossil specimen as a cannibal that had just swallowed two young of its own kind. This interpretation is favoured by the position of the two specimens and by the discovery of other fossil coelacanths containing large specimens of other kinds of fishes in their stomachs⁴.     

The Second Recorded Living Coelacanth from North Sulawesi

A detailed account of the second coelacanth specimen known to have been captured in Indonesian waters is provided. The account is written in the official format of the Coelacanth Conservation Council's (CCC) inventory of known specimens of the living coelacanth Latimeria chalumnae, and the specimen is herein numbered CCC no. 175. Morphological measurements and fin ray counts are recorded. A comparison of these measurements and meristic data with those recorded for Comoran specimens of Latimeria chalumnae shows that the present specimen has a similar allometry to L. chalumnae. Ongoing genetic analyses should reveal the depth of divergence between the two known populations of living coelacanths and help determine if this specimen is conspecific with its Comoran counterparts.     

An Endogenous Foamy-like Viral Element in the Coelacanth Genome

Little is known about the origin and long-term evolutionary mode of retroviruses. Retroviruses can integrate into their hosts'' genomes, providing a molecular fossil record for studying their deep history. Here we report the discovery of an endogenous foamy virus-like element, which we designate ‘coelacanth endogenous foamy-like virus’ (CoeEFV), within the genome of the coelacanth (Latimeria chalumnae). Phylogenetic analyses place CoeEFV basal to all known foamy viruses, strongly suggesting an ancient ocean origin of this major retroviral lineage, which had previously been known to infect only land mammals. The discovery of CoeEFV reveals the presence of foamy-like viruses in species outside the Mammalia. We show that foamy-like viruses have likely codiverged with their vertebrate hosts for more than 407 million years and underwent an evolutionary transition from water to land with their vertebrate hosts. These findings suggest an ancient marine origin of retroviruses and have important implications in understanding foamy virus biology.     

Evolutionary Changes in Vertebrate Genome Signatures with Special Focus on Coelacanth

With a remarkable increase in genomic sequence data of a wide range of species, novel tools are needed for comprehensive analyses of the big sequence data. Self-organizing map (SOM) is a powerful tool for clustering high-dimensional data on one plane. For oligonucleotide compositions handled as high-dimensional data, we have previously modified the conventional SOM for genome informatics: BLSOM. In the present study, we constructed BLSOMs for oligonucleotide compositions in fragment sequences (e.g. 100 kb) from a wide range of vertebrates, including coelacanth, and found that the sequences were clustered primarily according to species without species information. As one of the nearest living relatives of tetrapod ancestors, coelacanth is believed to provide access to the phenotypic and genomic transitions leading to the emergence of tetrapods. The characteristic oligonucleotide composition found for coelacanth was connected with the lowest dinucleotide CG occurrence (i.e. the highest CG suppression) among fishes, which was rather equivalent to that of tetrapods. This evident CG suppression in coelacanth should reflect molecular evolutionary processes of epigenetic systems including DNA methylation during vertebrate evolution. Sequence of a de novo DNA methylase (Dntm3a) of coelacanth was found to be more closely related to that of tetrapods than that of other fishes.     

An Account of the First Living Coelacanth known to Scientists from Indonesian Waters

A brief narrative is presented of the events surrounding the initial discovery of a coelacanth in an Indonesian fish market in Manado, Sulawesi, on 18 September 1997. Although the specimen was not purchased and preserved, photographs were taken and enough information gathered about the fish to warrant an official entry in the Coelacanth Conservation Council (CCC) inventory of known specimens of the living coelacanth Latimeria chalumnae. All known information about this first Indonesian specimen is summarized in the official CCC inventory format, and the specimen is herein numbered CCC no. 174.     

The Sensory Canal Systems of the Living Coelacanth, Latimeria Chalumnae: A New Instalment

Entire sensory canal systems of the coelacanth, Latimeria chalumnae, are described: not only the course of principal canals with their primary and secondary collaterals, but also the course and branches of the pit-line and reticular canals. The number of pores on the left side of the head were found to be 296 in an early (yolksac) embryo, 321 in a late term fetus, 485 in a juvenile, and 2974 in adults. This means that in latimeria most of the lateral-line canal system develop after parturition. Pit lines of the living coelacanth are not rows of superficial neuromasts but canals covered by a thin epidermis like in other sensory canals of the lateral line. These pit-line canals, however, have a very specific structure and branching pattern: the medial dorsal pit-line canal is connected by fine branches on top of the head. The infra-dentary pit-line canal connects via these branches with canals deep inside the bones. Several fine and richly branched canaliculi of unknown function radiate from each quadratojugal pit-line canal. The gular plate pit-line canal has superficially branching arms as well as connections to numerous deeper canals inside the bone. These canals consist of fine branches that in turn lead to and open on the ventral surface of the gular plates as small pores. The system is reminiscent of the reticular (pore) canal system known only from some fossil agnathans and fishes. Thus latimeria combines the reticular system of ancient vertebrates with the lateral-line system of modern fishes. The significance of this gular (possibly electro-sensory) system for feeding by the coelacanth will be discussed.