Fish Morphology

The subclass Teleostei Müller was erected in 1845 to contain all fishes possessing intermuscular bones (e.g., epineurals and epipleurals) and two arterial valves (in the conus arteriosus), and that are characterized also by the absence of muscles at the basal arteria (ventral aorta). Since these characters proved difficult for diagnosing fossils, the content of Teleostei was problematic from the start. These three characters are valid and uniquely derived, but the recognition of the taxon Teleostei sensu Müller has been ignored for most of the past 150 years, and the content of the group has changed numerous times. Additionally, a polyphyletic concept of Teleostei was the predominant idea for most of the last century. It was only during the 1970s that the monophyly of Teleostei was demonstrated. Although its monophyly is accepted, its content and phylogenetic relationships have been a subject of disagreement, with only some recent consensus between morphologists and molecular biologists. Understanding the history of Teleostei requires knowledge of its fossils forms. The monophyly of the total group Teleostei, which now includes Triassic pholidophorids, is supported by numerous synapomorphies, such as autosphenotic without small dermal component; unpaired vomer (in adults); complete ring of two sclerotic bones oriented anterior and posterior to orbit; and a hypural articulating with a few caudal rays—with further transformations in more advanced teleosts. Current evidence indicates that some Late Triassic taxa ({Pholidophoretes salvus and {Knerichthys bronni) from Europe represent the oldest known {pholidophorids, and the European genus {Prohalecites from the Ladinian/Carnian (Triassic; c. 240 Ma) boundary represents the oldest stem teleost. The synapomorphies now shared by living teleosts appeared stepwise more than 100 million years ago in the common ancestors of the sequential sisters of now living groups; they did not originate in the common ancestor of the three main living teleost clades (elopomorphs, and osteoglossomorphs plus clupeocephalans), and the analyses of character distribution reflects the gradual accumulation of features that now diagnose Recent teleosts. A list of characters supporting these hierarchical phylogenetic levels is provided.

The present study attempts to highlight the
value of multi-character approaches for defining thresholds
in fish ontogeny, like the onset of the juvenile period. We
developed techniques to objectively define the transition
from larval to juvenile development using morphometric as
well as morphological characters and exemplify the multicharacter
approach on newly settled white sea-breams
(Diplodus sargus sargus) collected from the eastern
Mediterranean. The morphometric analysis was based on
principles of multivariate allometry whereas the analysis of
morphology, on assigning a suite of selected characters
(here related to external morphology and osteological
development) into larval, transforming and juvenile states.
The size-at-change in multivariate allometric growth (Lm)
is considered here to denote mean length-at-metamorphosis.
An almost perfect match is demonstrated between Lm
(‘multivariate morphometry’) and mean size-at-morphological
change (‘multivariate morphology’) in white seabream.

The ichthyofauna of the Ranganadi River,
a tributary of the Brahmaputra River in Lakhimpur
district, Assam, India, has not been documented so
far. To fill this knowledge gap, samples were taken in
the Ranganadi River from April 2012 to March 2014,
which included 61 species of fishes belonging to six
orders, 17 families and 45 genera. One of these species
is Endangered, two are as Vulnerable, and six are Near
Threatened according to the International Union for the
Conservation of Nature. This study will help support the
conservation of fish diversity in the Ranganadi River of
Assam and the surrounding ecosystems.

The  body  shape  variation  among  244  specimens  of  Periophthalmus  waltoni  Koumans, 1941, collected from seven stations in the Persian Gulf and Gulf of Oman, was  analysed by utilising geometric morphometrics (GM) and truss-based morphometrics  methods (TBM). Discriminant function analysis did not show significant differences  between the shape of females and males. Canonical variate analysis and cluster analysis classified the specimens in two separate groups of stations: those in the Persian  Gulf, and those in the Strait of Hormuz plus Gulf of Oman. Potential factors contributing to the observed variation include differences in physicochemical parameters between the Persian Gulf and the Gulf of Oman.

ABSTRACT The body shape variation among 244 specimens of Periophthalmus waltoni Koumans, 1941, collected from seven stations in the Persian Gulf and Gulf of Oman, was analysed by utilising geometric morphometrics (GM) and truss-based morphometrics methods (TBM). Discriminant function analysis did not show significant differences between the shape of females and males. Canonical variate analysis and cluster analysis classified the specimens in two separate groups of stations: those in the Persian Gulf, and those in the Strait of Hormuz plus Gulf of Oman. Potential factors contributing to the observed variation include differences in physicochemical parameters between the Persian Gulf and the Gulf of Oman.