Abstract
Evolutionary novelties—derived traits without clear homology found in the ancestors of a lineage—may promote ecological specialization and facilitate adaptive radiations. Examples for such ...novelties include the wings of bats, pharyngeal jaws of cichlids and flowers of angiosperms. Belonoid fishes (flying fishes, halfbeaks and needlefishes) feature an astonishing diversity of extremely elongated jaw phenotypes with undetermined evolutionary origins. We investigate the development of elongated jaws in a halfbeak (
Dermogenys pusilla
) and a needlefish (
Xenentodon cancila
) using morphometrics, transcriptomics and in situ hybridization. We confirm that these fishes' elongated jaws are composed of distinct base and novel ‘extension’ portions. These extensions are morphologically unique to belonoids, and we describe the growth dynamics of both bases and extensions throughout early development in both studied species. From transcriptomic profiling, we deduce that jaw extension outgrowth is guided by populations of multipotent cells originating from the anterior tip of the dentary. These cells are shielded from differentiation, but proliferate and migrate anteriorly during the extension's allometric growth phase. Cells left behind at the tip leave the shielded zone and undergo differentiation into osteoblast‐like cells, which deposit extracellular matrix with both bone and cartilage characteristics that mineralizes and thereby provides rigidity. Such bone has characteristics akin to histological observations on the elongated ‘kype’ process on lower jaws of male salmon, which may hint at common conserved regulatory underpinnings. Future studies will evaluate the molecular pathways that govern the anterior migration and proliferation of these multipotent cells underlying the belonoids' evolutionary novel jaw extensions.
Mitochondrial DNA (mtDNA) can provide genome-level information (e.g. mitochondrial genome structure, phylogenetic relationships and codon usage) for analyzing molecular phylogeny and evolution of ...teleostean species. The species in the order Beloniformes have commercial importance in recreational fisheries. In order to further clarify the phylogenetic relationship of these important species, we determined the complete mitochondrial genome (mitogenome) of garfish Hyporhamphus quoyi of Hemiramphidae within Beloniformes. The mitogenome was 16,524 bp long and was typical of other teleosts mitogenomes in size and content. Thirteen PCGs started with the typical ATG codon (with exception of the cytochrome coxidase subunit 1 (cox1) gene with GTG). All tRNA sequences could be folded into expected cloverleaf secondary structures except for tRNASer (AGN) which lost a dihydrouracil (DHU) stem. The control region was 866 bp in length, which contained some conserved sequence blocks (CSBs) common to Beloniformes. The phylogenetic relationship between 26 fish Beloniformes species was analyzed based on the complete nucleotide and amino acid sequences of 13 PCGs by two different inference methods (Maximum Likelihood and Bayesian Inference). Phylogenetic analyses revealed Hemiramphidae as the sister group to Exocoetidae and it is a paraphyletic grouping. Our results may provide useful information on mitogenome evolution of teleostean species.
DNA barcoding of the cytochrome oxidase subunit I (COI) gene was utilized to assess the species diversity of the freshwater halfbeak genus Hemirhamphodon. A total of 201 individuals from 46 locations ...in Peninsular Malaysia, north Borneo (Sarawak) and Sumatra were successfully amplified for 616 base pairs of the COI gene revealing 231 variable and 213 parsimony informative sites. COI gene trees showed that most recognized species form monophyletic clades with high bootstrap support. Pairwise within species comparisons exhibited a wide range of intraspecific diversity from 0.0% to 14.8%, suggesting presence of cryptic diversity. This finding was further supported by barcode gap analysis, ABGD and the constructed COI gene trees. In particular, H. pogonognathus from Kelantan (northeast Peninsular Malaysia) diverged from the other H. pogonognathus groups with distances ranging from 7.8 to 11.8%, exceeding the nearest neighbor taxon. High intraspecific diversity was also observed in H. byssus and H. kuekanthali, but of a lower magnitude. This study also provides insights into endemism and phylogeographic structuring, and limited support for the Paleo-drainage divergence hypothesis as a driver of speciation in the genus Hemirhamphodon.
A new nematode species,
Philometra longa
n. sp.
(Philometridae), is described from male and female specimens collected from the body cavity of the marine fish,
Hyporhamphus australis
(Steindachner) ...(Hemirhamphidae, Beloniformes) from off the south-eastern coast of Australia. Based on examination by light and scanning electron microscopy, the new species differs from those parasitising other beloniform hosts mainly in the body length (4.69 mm), the length of spicules (141 µm) and the structure of the caudal end and the distal tip of gubernaculum in the male, and in the conspicuously long body (455–560 mm) of the gravid female.
Philometra longa
n. sp.
is the first species of philometrids described from fishes of the family Hemiramphidae. It is the 26th nominal species of philometrids and the 19th species of
Philometra
so far recorded from Australian marine and brackish waters. Re-examined museum specimens of
Philometra
sp. from
Hyporhamphus melanochir
(Valenciennes) off Tasmania, as well as those previously reported from the same host species off the Australian coast, were found to be identical with
P
.
longa
sp. n.
Recent examinations of some marine fishes from off the coast of South Australia revealed the presence of two species of
Philometra
Costa, 1845 (Nematoda: Philometridae):
P
.
inconveniens
n. sp.
from ...the ovary (males) and body cavity (subgravid female) of the southern garfish
Hyporhamphus melanochir
(Valenciennes) (Beloniformes, Hemiramphidae) and
Philometra
sp. (gravid and subgravid females) from the body cavity of the Australian barracuda
Sphyraena novaehollandiae
Günther (Perciformes, Sphyraenidae) (new host and geographical records). Specimens of species are described and illustrated based on light and scanning electron microscopical examinations.
Philometra inconveniens
n. sp.
differs from the most similar species
P
.
longa
Moravec, Barton & Shamsi, 2021, a parasite of the body cavity of the congeneric host off eastern Australia, mainly by a different structure of the gubernaculum (absence of dorsal barbs and presence of lateral extensions on its distal portion). This indicates a high degree of host specificity of these nematodes in co-occuring congeneric hosts.
The paper reports occurrence of Lutke’s halfbeak Hemiramphus lutkei Valenciennes, 1847, for the first time from the coastal waters of Odisha coast, India. This report confirms the occurrence of this ...species form an extended geographical range along the east coast of India and will be helpful in further study of its biology, zoogeography and taxonomic status of the family Hemiramphidae.
The genus Ceratothoa Dana, 1852, is revised for Australian waters. Ceratothoa is represented in Australia by nine species, including two new species: Ceratothoa barracuda sp. nov. described from ...Cairns and Ceratothoa globulus sp. nov. described from Lord Howe Island. Ceratothoa imbricata Fabricius, 1775 is redescribed, with Ceratothoa trillesi (Avdeev, 1979) and Ceratothoa huttoni Filhol, 1885 placed into junior synonymy; the preferred hosts are species of the genus Trachurus (Carangidae). Ceratothoa banksii (Leach, 1818) is validated and brought out of synonymy with Ceratothoa imbricata; host species are from the families Kyphosidae, Scombridae, Latridae, Carangidae, Mugilidae, Salmonidae, Scatophagidae, Pomatomidae and Hemiramphidae. Species excluded from the Australian fauna are Ceratothoa trigonocephala (Leach, 1818) with an unknown host identity and type locality; and Ceratothoa lineata Miers, 1876a, that here is transferred to the genus Mothocya Costa, 1851, with Mothocya ihi Bruce, 1986 placed into junior synonymy. Ceratothoa contracta (Miers, 1880), the New Zealand Ceratothoa novaezelandiae Filhol, 1885 and the East Pacific Ceratothoa gaudichaudii (Milne Edwards, 1840) are regarded here as species inquirenda. A key to the Australian species of Ceratothoa is presented.
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