Molecular identification and first morphological description of the Colorado snapper Lutjanus colorado (Perciformes: Lutjanidae) larvae.

This research study obtained the first morphological description of the Colorado snapper (Lutjanus colorado) larvae assisted by DNA barcoding as a molecular identification tool. Sixteen Lutjanidae larvae were separated from zooplankton samples and selected for this study. A fragment of the mitochondrial gene cytochrome oxidase subunit I (COI) of 658 bp was used in the analyses of intra- and interspecific genetic divergences; a neighbour-joining tree (NJ) of K2P distances was performed with reference sequences of 15 Lutjanidae species from the Northeastern Tropical Pacific. Genetic divergences and the NJ tree identified 16 larvae as L. colorado. Morphological investigations of larvae at different developmental stages were performed; similarities and differences are discussed in comparison to four species described previously for the Northeastern Pacific. Pigmentation patterns were the best diagnostic features, particularly the caudal melanophores, at least up to 12.4 mm body length.

Drivers for genetic structure at different geographic scales for Pacific red snapper (Lutjanus peru) and yellow snapper (Lutjanus argentiventris) in the tropical eastern Pacific.

The tropical eastern Pacific (TEP) is a highly dynamic region and a model system to study how habitat discontinuities affect the distribution of shorefishes, particularly for species that display ontogenetic habitat shifts, including snappers (Lutjanidae). To evaluate the genetic structure of the Pacific red snapper (Lutjanus peru) and the yellow snapper (Lutjanus argentiventris) throughout their distribution range along the TEP, 13 and 11 microsatellite loci were analysed, respectively. The genetic diversity of L. peru (N = 446) and L. argentiventris (N = 170) was evaluated in 10 and 5 localities, respectively, showing slightly higher but non-significant values in the Gulf of California for both species. The genetic structure analysis identified the presence of significant genetic structure in both species, but the locations of the identified barriers for the gene flow differed between species. The principal driver for the genetic structure at large scales >2500 km was isolation by distance. At smaller scales (<250 km), the habitat discontinuity for juveniles and adults and the environmental differences throughout the distribution range represented potential barriers to gene flow between populations for both species.

Proposed synonymy for Micropogonias altipinnis (Günther 1864), Micropogonias ectenes (Jordan & Gilbert 1882), and Micropogonias megalops (Gilbert 1890).

Within the Sciaenidae family, the genus Micropogonias is composed of three recognized species along the Pacific coast of Mexico: Micropogonias altipinnis, M. ectenes, and M. megalops. These species exhibit overlapping diagnostic characters, which make species identification difficult. This study ties morphological differences (meristic, morphometry of body, and otolith) with DNA sequences (CO1 and 16S fractions of mtDNA and 28S of nDNA) among Micropogonias species in the Pacific. Meristic analysis showed a latitudinal variation among the three species in the number of rays, the number of gill rakers, and length of the longest spine of the dorsal fin. Discriminant analysis of morphometric characters (body and otolith) showed three morphological entities (p < 0.001). However, the mean genetic divergences among the three species with partial sequences of mtDNA (CO1 and 16S), and nuclear (28S) were lower than those reported at the interspecific level (>2%). Genetic results suggest that the three species are one species and that the differences in meristics and morphometry could be the result of phenotypic plasticity or incipient speciation. In this sense, M. ectenes and M. megalops are proposed as junior synonyms of M. altipinnis.

Molecular identification and morphological description of Micropogonias megalops, Cynoscion othonopterus, C. reticulatus and Menticirrhus nasus larvae, collected in the upper Gulf of California during Summer 2012.

Sciaenidae fish larvae were collected from the upper Gulf of California during September 2012 using a conical net (505 µm) through surface tows. These were pre-classified into four larval morphotypes, based on external characteristics (mainly meristic and pigmentation). Partial sequences of cytochrome c oxidase, subunit 1 and 16S rRNA (16S) genes of mitochondrial DNA, were used in molecular genetic identification from each larval morphotype. Genetic results indicated the identification of four larval morphotypes as Micropogonias megalops, Cynoscion othonopterus, C. reticulatus and Menticirrhus nasus. Pigmentation patterns of larvae described after molecular genetic identification made it possible to distinguish between M. megalops, M. nasus and C. othonopterus (postflexion). However, pigmentation was not reliable for differentiating between preflexion larvae of C. othonopterus and C. reticulatus. From these results, both morphological and genetic approaches were proposed as complementary tools in taxonomic studies of ichthyoplankton, particularly in early fish larvae identification of congeneric species with similar morphological characteristics.

Morphological description of genetically identified Cortez bonefish (Albula gilberti, Pfeiler and van der Heiden 2011) leptocephali from the southern Gulf of California.

Bonefish leptocephali of the genus Albula are difficult to identify to the species level due to morphological similarities between two different species present in the Northeastern Pacific Ocean, A. esuncula and A. gilberti. In this study, 22 bonefish leptocephali (premetamorphic and early metamorphic), collected from two locations in the southern Gulf of California were identified as Albula gilberti by comparing 459 bp of their mitochondrial cytochrome b gene sequences to those of four other species of bonefish. The characteristics of these A. gilberti leptocephali were compared to those of previously described bonefish leptocephali in the region. No distinctive morphological characteristics (meristic and pigmentation) were found that differentiate premetamorphic leptocephali of A. gilberti from those of other Albula species, making species identification by molecular-genetics a necessity. In early metamorphic leptocephali some differences in horizontal eye diameter-head length ratio, number of rays of pelvic and anal fins and myomere of pelvic-fin origin may help to differentiate A. gilberti from A. esuncula.