Interspecific comparison of growth and shape within Diapterus (Gerreidae: Perciformes) using geometric morphometrics

Morphometric analyses can generate useful information to solve taxonomic problems by direct comparison of each species representative’s shape or by analyzing its growth patterns. In this study, growth patterns and shape variation of the four fish species belonging to the genus Diapterus (Gerreidae) were analyzed using geometric morphometrics. We examined 287 specimens, D. auratus (n = 65), D. aureolus (n = 76), D. brevirostris (n = 87) and D. rhombeus (n = 59). For the exploration of growth trajectories of each species, the standard length was used as a size measurement, and the Procrustes distance as a morphological variation measurement. We also compared averages of the morphological change direction within each species through a pairwise comparison between vector angles. These analyses were also used to select those fishes whose increase in size did not lead to a significant change in Procrustes distance. Once this subsample was selected, the body shapes of the four species were compared using Canonical variate Analysis and Multivariate Analysis of Variance. Diapterus aureolus showed the most different morphological trajectory and the most divergent vector within the genus. An average of 93% of correct classification was estimated from Mahalanobis distances. The Canonical Variate Analysis generated three statistically significant canonical variates (p < 0.001) and indicated that D. auratus, D. brevirostris, and D. rhombeus presented a more related shape between them than D. aureolus, as indicated in previous studies. In this context, we considered the shape and growth of D. aureolus with regard to its congeners can be an important element for suggesting a taxonomic rearrangement. However, our interpretation should be supported by phylogenetic analysis. Based in our study, we suggest that trajectories analyses can be directly used in morphometric comparisons to detect those specimens affected by allometry.     

First record of Eucinostomus melanopterus,Bleeker 1863 (Perciformes,Gerreidae) from the Río de la Plata estuary

We established the presence of Eucinostomus at the Río de la Plata Estuary (36°17′74′′S–56°46′68′′W). The report is based on specimen of 191.6 mm. total length, captured in shallow, warm and brackish water with sandy bottom. This is southernmost record for the Southwest Atlantic Ocean, and appears related with an event of low discharge of the Río de la Plata.     

Population parameters of the Pacific flagfin mojarra Eucinostomus currani (Perciformes: Gerreidae) captured by shrimp trawling fishery in the Gulf of California

Shrimp trawling fishery in the Gulf of California captures a wide variety of non-target species of fish, crustaceans, and mollusks that are relatively unknown. The Pacific flagfin mojarra Eucinostomus currani is a frequently found species in these catches, nevertheless, nothing is currently known about its population dynamics. To contribute to the knowledge on this fish species, we studied the size structure, growth, mortality, and the recruitment pattern during the 2004-2005 seasons. A total of 6,078 mojarra were captured from 350 samples, with minimum and maximum lengths of 4.5 cm and a maximum of 21.0 cm. The average total length of the four major cohorts was 11.4, 13.7, 15.6 and 18.0 cm, corresponding to ages 0.9, 1.2, 1.6 and 2.2 years, respectively, being the most abundant the 1.2 year-old group. The instant growth coefficient indicated moderate growth rates (K(s) = 0.81/year, K(E) = 0.85/year), corresponding to individuals living between 3.5 to 3.7 years. The estimated asymptotic lengths was L (infinity) = 21.8 cm. In general, the population could be considered healthy: natural mortality (M = 1.53/year); total mortality (Z = 2.73/year); condition factor (K = 0.01072); fishery mortality (F = 1.2/year) and exploitation rate (E = 0.43/year). The maximum reproduction period almost coincided with the closed season for shrimp fishing (March to August), thus we concluded that survival of the species is ensured because reproduction is indirectly protected.     

A geometric morphometric approach for disparity of the sulcus acusticus of sagitta in species of Gerreidae (Teleostei: Perciformes)

This paper explores shape disparity in the sulcus acusticus of saccular otolith using geometric morphometric methods in selected Gerreidae species. First, multivariate linear regressions between size (CS-log-transformed) and shape were implemented to uncover allometry in the variation of the sulcus acusticus at three levels: intraspecific, intrageneric, and interspecific. Second, we assessed species disparity to investigate if differences in disparity are associated with three biologically contrasting ecological or historical processes within the family. Specifically, we asked: (1) How has disparity changed as a result of an ecological shift from marine to freshwater habitat? (2) How has disparity changed in genera with increasing taxonomic richness? and (3) How did a vicariant event across the Panama isthmus changed disparity in a pair of sister species? Our results indicate that the disparity of the sulcus acusticus shape of the single freshwater species (Eugerres mexicanus) is in the middle of the range of values of the 17 marine species compared. This suggests that the change to a freshwater environment did not influence the variability of the sulcus acusticus. In the taxonomic comparisons, as expected, disparity is lowest in the monotypic Deckertichthys, while it increases with species number in Diapterus. In the vicariant pair, the Pacific basin species (Diapterus brevirostris) has a disparity value almost twice the value than in the Atlantic taxon (D. rhombeus). It remains to be investigated if the same disparity patterns documented here are associated to marine-freshwater ecological shifts and vicariant events in other fish families.

     

Urohyal size versus body-length and weight relationships for thirteen mojarras species (Perciformes: Gerreidae) in Mexican waters

Given that it has been shown that urohyal bones can be used to identify gerreid fish to the species level, predictive regression equations between urohyal size and fish standard length and weight of thirteen species of Gerreidae living along the coasts of Mexico, were calculated. All regressions were statistically significant with coefficients of variation and coefficient of determination values around 0.90 in most of cases. These regression equations could provide a reliable tool in trophic ecology and other studies by estimating the original body size and weight of fish from measuring urohyal bone lengths. Information provide from the urohyal bone-fish length and weight relationships also facilitates the assessment of the potential role of gerreid fish found in the diet of piscivorous species from Mexican waters.     

Larval, pre-juvenile and juvenile development of Diapterus peruvianus (Perciformes: Gerreidae)

The development of Diapterus peruvianus (Sauvage 1879) is based on 60 larvae collected in superficial tows made in Bahía Concepción, and on 16 pre-juvenile and juvenile organisms collected in Bahía de La Paz, B. C. S., México, using a standard plankton net and a rectangular epibenthonic net, respectively. Larvae of D. peruvianus show three large blotches on the dorsum of the gut that can fuse together and give the appearance of one large continuous blotch. There are two to three pre-anal pigments and 16 post-anal pigments in the ventral midline; cephalic pigments are present from the postflexion stage, as well as a serrated preoperculum. The pre-juvenile and juvenile organisms are distinguished by their body depth, the anal-fin formula, the serrated pre-operculum and the base pigments in the dorsal and anal fins.     

Genetic differentiation between two color morphs of Gerres erythrourus (Perciformes: Gerreidae) from the Indo-Pacific region

A portion of the mitochondrial 16S rRNA gene was compared between two color morphotypes of Gerres erythrourus, viz. “yellow type” and “white type,” obtained from Ryukyu Islands, Japan, and various areas of the Indo-Pacific, respectively. Phylogenetic analyses showed that the haplotypes of each color morph were reciprocally monophyletic, supported by high bootstrap values. The degree of sequence difference between the two color morphs was comparable to that existing between species of the same complex as well as other distinct gerreid species. The genetic results together with their geographic range indicated that the two color morphs represent two distinct species. Supplementary material to this paper is available in electronic format at http://dx.doi.org/10.1007/s10228-005-0324-0     

Geometric morphometrics of the skull of Tinamidae (Aves, Palaeognathae)

The Tinamidae comprise exclusively Neotropical palaegnathous birds, with homogeneous body morphology and no sexual dimorphism. The goal of this work was to explore the variation in skull morphology between taxa and its possible correspondence with features such as diet or gender using geometric morphometric tools. Eleven landmarks were analyzed in 53 skulls of 4 genera that inhabit grasslands: Nothoprocta, Eudromia, Nothura and Rhynchotus. Intrageneric and intergeneric variability was analyzed. The genera studied here can be distinguished based on the geometric shape of their skull, with prenarial region length and neurocranium shape as the most outstanding features. In the genus Eudromia, males and females could be differentiated, while in the genus Nothoprocta, the species differentiated according to their trophic habits. This study allows establishing that genera and, in some cases, the gender of the Tinamidae can be differentiated based on cranial shape.     

Two new species of Haliotrema (Monogenoidea: Dactylogyridae) from Cirrhitus rivulatus (Perciformes: Cirrhitidae) from the Pacific coast of Mexico

During surveys of helminth parasites of marine fishes from the Pacific coast of the Guerrero State in Mexico, 2 undescribed species of Haliotrema Johnston and Tiegs, 1922 (sensu Young, 1968) (Dactylogyridae) were found infecting the gills of the giant hawkfish Cirrhitus rivulatus Valenciennes, 1846 (Perciformes, Cirrhitidae), i.e., Haliotrema cirrhitusi n. sp. and Haliotrema pollexinus n. sp. The new species are similar with respect to the morphology of the anchors with base-shaft junction crazed, hinged, or both; dorsal anchors with an elongate superficial root; a tubular male copulatory organ (MCO) with a cylinder-shaped base diagonally opening; and a membranous accessory piece, shaped like a vane, encircling MCO to form 2 complete spirals from the anterior margin of base to the terminal portion of the MCO. While H. cirrhitusi and H. pollexinus differ from all other species of the genus in the general morphology of the copulatory complex, only H. pollexinus notably differs from all these species in having a superficial, blade-like projection from the inner surface on the distal shaft of anchors. Haliotrema cirrhitusi and H. pollexinus are the only members of the genus recorded in the Mexican Pacific and from a cirrhitid host.     

Feeding habits of cichlid species (Perciformes: Cichlidae) in Caobas lake, Quintana Roo, Mexico

Feeding habits of seven cichlid species (Archocentrus octofasciatus, A. spilurus, "Cichlasoma" robertsoni, "C." synspilum, "C." urophthalmus, Petenia splendida, Thorichthys meeki) in Lake Caobas, southern Yucatan Peninsula, were studied. Samples were taken with enclosure and cast nets during the dry and rainy seasons of 1995 (day and night). The environment was characterized by measuring temperature, conductivity and pH. All individuals were below 41 mm SL (N = 281). Frequency of occurrence and prey abundance were analyzed. Main prey items were chironomids, mites, copepods, cladocerans, and ostracods. The cichlids fed mainly on zooplankton, with the partial exceptions of P. splendida (piscivore), "C." synspilum and A. spilurus (herbivores). A cluster analysis showed that the most similar trophic spectra were those of T. meeki, "C." robertsoni and "C." salvini, which were also the least diverse. "C." synspilum and A. spilurus had an intermediate distance between their diets and those of other species. The species with the most distinctive feeding composition were P. splendida (with the most diverse and equitable diet) and the omnivore A. octofasciatus (whose diet was the richest one). T. meeki showed quantitative diel, ontogenetic, and seasonal diet changes, but none between sexes. "C." robertsoni, "C." salvini and "C." synspilum differ in food habits in Caobas and in other localities, a fact that underscores the trophic adaptability of cichlids. Trophic overlap between cichlids in Caobas could imply absence of competition, perhaps because resources are abundant in the ecosystem.     

A review of the <Emphasis Type="Italic">Gerres subfasciatus</Emphasis> complex from the Indo-West Pacific,with three new species (Perciformes: Gerreidae)

Gerres japonicus Bleeker, 1854, and Gerres subfasciatus Cuvier in Cuvier and Valenciennes, 1830, are redescribed, and Gerres akazakii sp. nov. (Japanese endemic), Gerres ryukyuensis sp. nov. (Okinawa I., Japan), and Gerres shima sp. nov. (Indo-Malayan region, including the Andaman Sea, Southeast Asia, southern China and Taiwan, and Ryukyu Is., Japan) are described. Gerres ovatus Günther, 1859, and Gerres kapas Bleeker, 1854, are recognized as junior synonyms of G. subfasciatus and Gerres oyena (Forsskål, 1775), respectively. All species (except G. oyena) have a small (<170?mm in standard length: SL), moderately deep (depth 36–48% SL), body with dark vertical bars, dorsal fin rays X, 9 or IX, 10, and 31/2 or 41/2 scale rows between the 5th dorsal fin spine base and lateral line, defined as the G. subfasciatus complex. The five species can be variously differentiated from each other by dorsal head squamation, and differing meristic, morphometric, and color characters. They are generally distributed sympatrically in the Indo-West Pacific. Other nominal species of uncertain status or relationship are discussed.     

Geometric morphometrics of carapace of Macrobrachium australe (Crustacea: Palaemonidae) from Reunion Island

Zimmermann, G., Bosc, P., Valade, P., Cornette, R., Améziane, N. and Debat, V. 2011. Geometric morphometrics of carapace of Macrobrachium australe (Crustacea: Palaemonidae) from Reunion Island. —Acta Zoologica (Stockholm) 93 : 492–500. We investigated the structure of carapace shape variation in six populations of Macrobrachium australe Guérin‐Méneville 1838 (Crustacea: Decapoda: Palaemonidae) from Reunion Island (Indian Ocean) freshwaters. The morphometric analysis revealed the occurrence of two morphotypes corresponding to two different types of habitats. Individuals living in lotic habitats present a thick carapace armed with a short, robust and straight rostrum, while individuals from lentic habitats have a slender carapace armed with a thin long rostrum orientated upward. This difference suggests an adaptation to lotic disturbances and is tentatively interpreted as adaptive phenotypic plasticity. In such amphidromous organisms regressing to freshwaters after a marine larval phase, selection for physiological and developmental flexibility might facilitate further adaptation and allows the colonisation of a wide panel of environmentally different and sometimes geographically distant insular streams.     

Genetic differences among three species of the genus Trichiurus (Perciformes: Trichiuridae) based on mitochondrial DNA analysis

The mitochondrial DNA segment encoding the 16S ribosomal RNA (16S rRNA) gene sequence (ca. 600 bp) was compared among Trichiurus sp. 2 (sensu Nakabo, 2002) (obtained from various areas of Japan), T. japonicus Temminck and Schlegel (collected from various localities within Japan), and true T. lepturus Linnaeus (caught off the Atlantic coast of the United States and Brazil) of the family Trichiuridae using 10, 10, and 15 specimens, respectively. Based on phylogenetic analysis using a neighbor-joining (NJ) algorithm, the haplotypes of Trichiurus sp. 2, T. japonicus, and T. lepturus indicated three distinct monophyletic lineages, being supported by 100% bootstrap values with no haplotypes overlapping or sharing among the lineages. Trichiurus sp. 2, T. japonicus, and T. lepturus are genetically different from each other, suggesting that they are three distinct species.