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.     

Size structure, gonadic development and diet of the fish Diapterus rhombeus (Gerreidae) in the Pom-Atasta fluvial-deltaic system, Campeche, Mexico

The fish Diapterus rhombeus was studied during an annual cycle from 1992 to 1993 in the fluvial-deltaic Pom-Atasta system associated with Terminos Lagoon, Campeche, Mexico. It is a dominant species in the system, based on its numeric abundance, weight, high frequency and wide distribution. A total of 745 individuals were obtained, with a weigth of 2 890.2 g and length ranging from 3.0 to 16.7 cm. The annual variation of the allometric coefficient b was from 2.71 to 3.345. The condition factor varied from 0.711 to 0.934. The statistical analysis shows significant differences (p < 0.05) between the seasons of the year and the habitats of the system for the weight, the longitude and the condition factor K, which reflects the space-temporal utilization of the system for the species. The population present at Pom-Atasta, consists mainly by juvenile and few preadults individuals in gonadal stages I, II, and III, and more females than males were recorded. This species utilizes the system as a nursery area, growth and feeding area. It has a varied trophic spectrum, and consumes at least eight different groups. Its principal food items are undetermined organic matter, foraminifers, ostracods and tanaidaceans. It is a first order consumer. The Pom-Atasta system is located in a zone of intense fishing and oil activity, so it is important to advance in the knowledge of its fishing resources.     

Gerres methueni Regan, 1920, a senior synonym ofG. rappi (Barnard, 1927) (Perciformes: Gerreidae)

Gerres methueni Regan, 1920, for many years identified asG. rappi (Barnard, 1927), is redescribed as a senior synonym of the latter species, following examination of two syntypes of the former and comparative material from South Africa and Madagascar.Gerres methueni is characterized by prominent dark stripes along the scale rows above the lateral line and the 4 or 5 rows immediately below it, 5–17 small scales on the preopercular flange, arranged in 1–3 scale row(s) at the corner, 42–44 pored lateral line scales+3–5 additional pored scales on the scaly sheath of the caudal fin base, 41/2–51/2 scales between the fifth dorsal fin spine base and lateral line, and second dorsal fin spine length equal to or slightly shorter than the third dorsal fin spine length.Gerres methueni is currently known from South Africa, southern Mozambique and Madagascar, being endemic in those areas.     

Larval development of bigmouth manefish Caristius macropus (Perciformes: Caristiidae) from the western North Pacific

Larvae of bigmouth manefish Caristius macropus are described and illustrated on the basis of seven specimens (4.2–10.5 mm in body length) from the Kuroshio waters (0–60 m depth) and the transition waters (surface) between the Kuroshio and Oyashio fronts of the western North Pacific. The present larvae of C. macropus are distinguished from those of Paracaristius maderensis that inhabit the North Pacific by having 39–40 myomeres, 34 dorsal-fin rays, and 22 anal-fin rays. The present study, along with previous studies of the early life stages of caristiids, shows that larvae of the family may be defined by the following characters: body elongate in preflexion stage but becoming deep bodied and hatchet shaped after notochord flexion; anus located near vertical through base of pectoral fin; head large, without spination or serration; a distinct vertical band on the posterior tail throughout the larval stages, and two bands gradually appearing on the tail and trunk during the flexion and postflexion stages; and melanophores present around the notochord tip by the flexion stage. Adult C. macropus are found in the subarctic and temperate waters of the North Pacific; however, the present study and other occurrences of early life stages of the species probably indicate that C. macropus may spawn over a wide area in the North Pacific.     

Morphological development of larval and juvenile Alectis indica (Perciformes: Carangidae) reared in captivity

Larvae and juveniles of Alectis indica reared in captivity are described based on 47 specimens (3.2–32.0 mm in body length: BL). Development was typical for the tribe Carangini except for the presence of elongated fin filaments. Elongated dorsal-fin filaments were present at preflexion (3.2 mm BL). During flexion, the anal- and pelvic-fin rays elongated and the body deepened. The full complement of fin spines and rays was present by 7.1 mm BL. The larvae of A. indica could be differentiated from those of Alectis ciliaris, which also inhabits in the Indo-Pacific waters, by the presence of a ventral series of melanophores on the tail, elongated pelvic fins, and the timing of anal-fin spine migration. The rounded body and elongated fin rays of A. indica cause it to resemble venomous Cubomedusae.     

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     

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 development of the Amur sleeper Perccottus glenii (Perciformes, Gobioidei, Odontobutidae) and the origin of fish of the suborder Gobioidei

The external morphology and development of skeletal elements is investigated in larvae and fry of one of the most generalized representatives of the suborder Gobioidei—the Amur sleeper Perccottus glenii. It is characterized by an indirect type of development accompanied by the expressed metamorphosis, according to Balon’s classification (1985). Fry of P. glenii are capable of an active mode of life and exogenous feeding almost immediately after hatching which favors a wide distribution of this species. Morphogenesis of previously revealed diagnostic characters of Gobioidei is investigated. New apomorphies are found also indicating to a high separation level of P. glenii from representatives of other suborders of Perciformes. At the same time, it is found that some developmental traits of P. glenii are characteristic of generalized Perciforems. Some advanced characters acquired in parallel with representatives from the group of suborders Blennioidei s. l. also indirectly indicate that P. glenii and, generally, Gobioidei belong to Perciformes. Analysis of special traits of development of the skeleton of P. glenii supports the ideas of Regan (1911) on the origin of Gobioidei from generalized Percoidei. With consideration of advanced characters, general for Gobioidei and the suborders Trachinoidei, Notothenioidei, Zoarcoidei, and Blennioidei of the group Blennioidei s. l., it is assumed that Gobioidei and Blennioidei s. l. stem from the same group or from the related groups of Percoidei.     

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.     

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.

     

Gerres limbatus Cuvier and G. lucidus Cuvier from the Indo-Malay Archipelagos, the latter corresponding to young of the former (Perciformes: Gerreidae)

Taxonomic status of Gerres limbatus Cuvier in Cuvier and Valenciennes, 1830 and G. lucidus Cuvier in Cuvier and Valenciennes, 1830 was studied. The two species were reassessed as the same species, the latter corresponding to young of the former, on the basis of examination of their eight syntypes and other comparative specimens. Gerres limbatus clearly differs from other congeners in having 2½–3 (usually 2½) scales between the 5th dorsal fin spine base and the lateral line, and four or five diffuse, dark saddle patches mainly along the back in life (more apparent in small specimens less than ca. 65 mm in standard length, or preserved and stressed live specimens) (vs. usually more than 3½ scales between fifth dorsal fin spine base and lateral line, and and no such body color pattern of G. limbatus in other congeners). The species is currently known from the southern and western coasts of India including Sri Lanka, the Malay Peninsula, Gulf of Thailand, and Indonesia, becoming rare in occurrence eastward.