Acta Zoologica最新文献

The Japanese flathead, Inegocia japonica Cuvier, 1829 is a commercially important fish in small-scale coastal fisheries in Thailand; however, an explanation of its digestive biology is missing. This study describes the digestive tract and accessory organs of I. japonica, using morphological and histological methods. The fish (10 individual fish, 24.5 ± 0.98 cm in total length) were obtained from Libong Island, Thailand. Integrated morphological and histological data showed that the digestive tract was composed of oesophagus, stomach, pyloric caeca and intestine, with accessory organs. All digestive tracts consisted of four layers, including mucosa, submucosa, muscularis and serosa. Two stomach regions were identified (cardiac and pyloric stomachs). Several clusters of gastric glands were identified in the cardiac stomach. Each gland was a unicellular structure. The apical surface of this gland contained the vacuolar cell. The intestine was lined with a simple columnar structure with goblet cells that was similar to pyloric caecum. Goblet cells were rare in the anterior intestine, in contrast to the posterior intestine where goblet cells were abundant. The numerous of hepatocyte was mostly observed in the liver, whereas an exocrine acinar cell of pancreas was also identified. The results of our observations provided the first information of the digestive tract of I. japonica and can be applied to advanced study, such as physiology and histopathology.

Ectotherms thermoregulate to maintain their body temperature within the optimal range needed for performing vital functions. The effect of climate change on lizards has been studied as regards the sensitivity of locomotor performance to environmental temperatures. We studied thermoregulatory efficiency and locomotor performance for Liolaemus fitzgeraldi in the Central Andes of Argentina. We determined body temperature, micro-environmental temperatures and operative temperatures in the field. In the laboratory, we measured preferred temperatures and calculated the index of thermoregulatory efficiency. We estimated the thermal sensitivity of locomotion by measuring sprint speed (initial velocity and long sprint) and endurance at five different body temperatures. Body temperature was not associated with either micro-environmental temperature, nor did it show differences with preferred temperatures. Thermoregulatory efficiency was moderate (0.61). Initial velocity and long sprint trials showed differences at different temperatures; however, endurance did not. Moreover, the optimal temperatures for the performance trials showed no significant differences among themselves. We conclude that Liolaemus fitzgeraldi has thermal sensitivity in locomotor performance with respect to body temperature and that it is an eurythermic lizard that experiences a large variation in body temperature and that has thermal flexibility in the cold.

The order Gonorynchiformes was repeatedly studied to gain new insights into the evolution of its sister-taxon, the Otophysi, the most successful freshwater fish taxon worldwide. Previous ontogenetic studies of gonorynchiforms mainly focused on the anterior vertebral column to investigate the evolutionary origin of the Weberian apparatus. Herein, we highlight the ontogeny of a different skeletal complex, the dorsal and anal fins. We studied the development of the skeletal elements of both fins in the gonorynchiform Kneria stappersii. We gained new insights into the developmental and formation patterns of K. stappersii. We discuss these patterns as well as the development of certain elements like the fin stay in comparison to other gonorynchiforms and available otomorph data. In general, the fin development in K. stappersii is very similar to that of other gonorynchiforms and even otomorphs. Specific differences, however, reveal that much remains unknown about the evolution of median fin elements such as the fin stay.

The present study deals with the topography of retinal ganglion cells (GCs) and spatial resolution in the smelt Hypomesus japonicus. The eyes and retinae were examined by light microscopy and computerized tomography. DAPI labelling was used to visualize cell nuclei in the ganglion cell and inner plexiform layers. Two zones of increased GC density in the nasal and temporal retina were bridged by a horizontal streak with the GC density ranging from 5600 to 8000 cells/mm². The maximum cell density (area retinae temporalis) ranged from 9492 to 14,112 cells/mm², and the total number of GCs varied from 286 x 10³ to 326 x 10³ cells in three individuals. The theoretical anatomical spatial resolution (the anatomical estimate of the upper limit of visual acuity) was minimum in the ventral periphery (smaller fish, 1.43 cpd; larger fish, 1.37 cpd) and maximum in area retinae temporalis (smaller fish, 2.83 cpd; larger fish, 2.41 cpd). The relatively high density of GCs and presence of the horizontal streak and area retinae temporalis in the H. japonicus are consistent with its highly visual behaviour. The present findings contribute to better understanding of the factors affecting the topography of retinal ganglion cells and mechanisms of visual adaptation in fish.

Sex dimorphism is found in many organisms and is an important source of intraspecific variation. Among freshwater fishes, all members of the Aphaniidae (killifishes, Cyprinodontiformes) are known for their pronounced sex dimorphism, and it has been proposed that sexual selection has played a role in their diversification. However, few studies have assessed their sex dimorphism in detail. Here, we use Aphaniops stoliczkanus (Day, 1872) to analyse morphological variability within and between sexes and within the total sample using statistical analyses of body morphometry, meristic traits and otolith data. We found that sex dimorphism (i) is significant in many body morphometric variables, but (almost) absent in meristic traits and otolith morphometry, (ii) is most marked in anal- and dorsal-fin lengths (larger in males), and in anal- and dorsal-fin positions (more anteriorly positioned in males) and (iii) does not alter the overall variance of the population unless the character concerned is highly divergent. Our data also suggest that anal- and dorsal-fin lengths in males of A. stoliczkanus are sexually selected traits. Together with literature data, this reinforces the idea that sexual selection plays a role in the diversification of aphaniid species. Our results are also relevant to work on fossils, in which morphological variability is often difficult to interpret.

Males of Macrobrachium olfersii have a large cheliped (second pereiopod) with individual variations in shape and ornamentation, and they vary in size within and between populations. Some misidentification or doubts about taxonomic validity occur due to this morphological variability throughout their geographic distribution. We carried out a morphometric analysis to detect specific patterns and the potential occurrence of morphotypes in M. olfersii from different populations. Our data set included 52 females and 109 males collected in the Neotropical region, between the north and south limits of Brazilian territory, in coastal rivers from the states of Rio Grande do Norte, Bahia, Espírito Santo, Rio de Janeiro, São Paulo, Paraná and Santa Catarina. Body measurements were size standardized by allometric methods and explored by the principal component analysis (PCA) and non-hierarchical analysis of K-means clustering and canonical variate analysis (CVA). Our results suggested three distinct morphological groups (morphotypes) only for males in M. olfersii. Furthermore, the confirmation of monophyly of the different populations of M. olfersii was accomplished by sequences of 16S rDNA. Additional studies about relative growth in other populations and the analysis of the entire ontogenetic development of males in the laboratory will be important to complement the knowledge about morphotypes in this species.

We studied the life history of the New River Crayfish, Cambarus chasmodactylus in Anthony, Creek, West Virginia during an entire activity season—from May 2011 through October 2011. We observed two mass moulting events; one occurred in May, whereas the other occurred in September. Most males within this population moulted from Form I (i.e. reproductive form) to Form II (i.e. non-reproductive form) in May and then later returned to Form I after a September moulting event. We collected females with active glair glands from May to June, with oviposition occurring from July to August. Fecundity was high and weakly correlated with body size. Egg counts of attached eggs/young in ovigerous females ranged from 41 to 281, with an average of 168. Additionally, from June to October, we dissected a subset of females to determine the monthly gonadal development in females with and without active glair glands. Lastly, in the laboratory, we observed 4th instar neonate crayfishes repeatedly “drifting” between females. We speculate on the relevance of this drifting behaviour and propose future studies to investigate this phenomenon. Our study provides the first comprehensive understanding of the life history of C. chasmodactylus.

Larval information plays an important role in life history and population dynamics studies, as well as in phylogenetic and systematic ones. The early zoeal stages (zoea I, II and III) of the snapping shrimp Alpheus buckupi were described and illustrated based on laboratory-hatched larvae from parental females sampled in Cananéia, São Paulo State, Brazil. The morphological characters of the species were compared with descriptions of other Alpheus species with a known first zoeal stage. The first zoeal stage of this species can be separated from the first zoeal stage described for the other 26 species using the following combination of characteristics: basial endite of maxillule with 2 stout spines (distal one with two rows of spinules) and 2 small plumose setae; basial endite of maxilla bilobed, with 3 and 4 simple setae on proximal and distal lobe, respectively, and five (3 strong and 2 slender) simple setae arranged (2 + 2 + 1) on the basis of first maxilliped. The substantial progress in larval knowledge is fundamental to areas such as ecology and will allow us to better understand the distribution of different early life stages of Alpheus species in the meroplankton community.

We observed the presence of follicular cells (FC) in the ovaries of Penaeus subtilis (n = 1198), which led us to classify the development of germ cells into six phases: oogonia, previtellogenic oocytes, primary and secondary vitellogenic oocytes, mature oocytes and atretic oocytes. The FC changes their shape according to the development of germ cells and showed a different distribution along the ovary, which allowed differentiating vitellogenic oocytes into primary and secondary. We also observed that the postovulatory follicles (POF) are composed of follicular cells. The presence of POF in penaeids ovaries is rarely reported, but allows the differentiation between spent and resting stages, commonly grouped in reproductive biology research. Furthermore, observation of ovarian lining was useful to differentiate immature females from females that had spawned at least once. Thus, ovarian development was classified into six stages: immature, early developing, advanced developing, ripe, spent and resting. The distribution and shape variations of FC, ovarian lining features and presence of POF were considered crucial for the classification of ovarian maturation stages. The methods developed here may improve estimates of their reproductive cycle, size at first maturity and spawning season, which are important variables in future studies of the reproductive dynamics.

Five male specimens of the species Molossus rufus from north-western Parana were captured, identified, packaged and transported to the laboratory for weighing and later euthanasia with isoflurane. They were laparatomized for evaluation of macroscopic characteristics and the digestive tube segments were collected for fixation in 10% neutral formalin for histological processing, after 48 h of fixation. Macroscopically, the digestive tube had an oesophageal segment in the abdominal cavity, with a J-shaped saccular stomach, in addition to a small intestine divided into duodenum, jejunum-ileum and terminal ileum. In the large intestine, an organ dilatation was observed from the small intestine with a one-way oral-aboral ending in the anus, which was called the descending colon. Morphological similarity of the walls of all segments with those of other mammals was observed; however, it presented some peculiarities such as the absence of oesophageal glands, Brunner in the intestine, cecum and appendages. The anatomical disposition and tissue pattern were similar to that found in other insectivorous species. The adaptations of the digestive tube of this species are possibly due to the insectivorous feeding habits, which can be impacted due to anthropic actions in foraging environments.