Haemogregarina majeedi n. sp. from the freshwater fish Barbus sharpeyi Günther (Cyprinidae)

Summary

A new species of haemogregarine was found in the fish Barbus sharpeyi (Cyprinidae): Haemogregarina majeedi n. sp. which is broadly oval to reniform and with a large, subterminal nucleus. It was found with one to two schizonts within the erythrocytes and erythroblasts which were shorter and broader than normal. This is the third haemogregarine described from fishes in Iraq.     

Influence of body mass, age, and maturation on specific oxygen consumption in a freshwater cichlid fish, Cichlasoma nigrofasciatum (Günther, 1869)

The oxygen consumption of a freshwater convict cichlid (Cichlasoma nigrofasciatum) was determined throughout the fish development from age 74 days to 403 days, covering the period before and after maturation. The specific oxygen consumption decreases with increasing age. The decrease in metabolic rate appears rather in distinct phases. A small increase in the average specific metabolic rate (mainly from the bigger fish) around age 200 days suggests an involvement of internal changes in the fish during a transition period from "young" state to "mature" state. The relationship between the specific oxygen consumption and body mass is determined by maturation and age. Before reaching maturation (before age 200 days) the correlation between specific oxygen consumption and body mass is negative for "young" fish of the same age. After age 200 days, no correlation between both parameters could be found. We suggest from this study that both factors "age" and "size" of the organism have to be considered for determining the metabolism, especially in fish. This study indicates that even in fish, which retain a continuous growing capability until they die, the decrease in the specific oxygen consumption is related to the aging process.     

A new cucullanid species (Nematoda) from the freshwater fish Vieja intermedia (Günther, 1862) (Cichlidae) in Mexico

A new nematode species, Cucullanus angeli n. sp., is described from specimens recovered from the intestine of Vieja intermedia (Günther, 1862) from the Lacantun River, State of Chiapas, Mexico. It is characterized largely by having an unusual distinct unpaired median papilla present on anterior cloacal lip in the male and the situation of phasmids (close to eighth pair of papillae); it is further characterized by equal spicules (length 175-475 microm), distribution of caudal papillae, a preanal sucker surrounded by first and second pair of papillae, and conical tail in both sexes, ending in small terminal digitiform process (being more conspicuous in the female).     

Assessing environmental conditions of the Río Champotón (México) using diverse indices and biomarkers in the fish Astyanax aeneus (Günther, 1860)

The upper reaches of the Río Champotón in southwestern Mexico are largely unknown to science. This river is sustaining anthropogenic and natural disturbances by deforestation, substitution of natural vegetation, and agricultural non-point source pollution. Furthermore, hurricanes provoke flooding of these areas, exposing the aquatic biota to pollutants. Several approaches were used to assess the effects of environmental conditions along the freshwater portion of the Río Champotón in the native fish Astyanax aeneus and to determine the feasibility of extrapolating responses between levels of organization, and to link spatial and seasonal fish responses with water quality features. A water quality index (WQI) was employed as an indicator of environmental conditions, a set of sub-organismal biomarkers in A. aeneus (lipid peroxidation, glutathione S-transferase, ethoxyresorufin-O-deethylase and lactate dehydrogenase) was monitored to determine the integrated biomarker response (IBR), and somatic indices (individual and population-level responses; gonadosomatic, hepatosomatic, and condition factor) were characterized. Canonical correspondence analysis revealed spatial and seasonal variations in all the approaches. The dry and the wet season (April and July) exhibited low WQI scores, but decreased hardness and conductivity values as well as increased WQI values occurred during the post-hurricane season when crop fields adjacent to the riverbed were inundated. Although the WQI suggested low levels of contamination, the biomarkers did not remain static; wide fluctuations reflected fish exposure to seasonal stressors that provoked impairments in biological responses. All biomarker values were high, mainly in the post-hurricane season (November). The IBR exhibited two peaks that may be related to stress periods (April and November), with decreasing post-stress values suggesting the existence of homeostatic processes in the fish. The somatic indices reflected some seasonal and spatial differences at the population level – the gonadosomatic and hepatosomatic indices peaked in the middle of July and November, respectively – but the condition factor remained constant among sites and study periods. Future studies are needed to explore the link between the fish biomarker responses and possible causal stressors (natural or anthropogenic).     

Acanthocephalus?amini n. sp. (Acanthocephala: Echinorhynchidae) from the freshwater fish Cichlasoma?urophthalmus (Günther) (Cichlidae) in Mexico

Acanthocephalus amini n. sp. (Palaeacanthocephala: Echinorhynchidae) is described from the intestine of Cichlasoma urophthalmus (Günther) (Pisces: Cichlidae) collected in the Río Champotón, a river in Campeche State, Mexico. It is the fourth species of Acanthocephalus Koelreuther, 1771 described from North American freshwater fishes, although two other species are known from South America. The new species is distinguished from other members of Acanthocephalus by features of its trunk, which is small, clavate, slightly expanded medially and bluntly pointed posteriorly. It is further distinguished by having a cylindrical proboscis armed with 13–14 longitudinal rows of 11–12 stout hooks; the apical and medial proboscis hooks are almost uniform in size and shape, decreasing in size towards the base; the posteriormost hooks are smaller, straighter and more slender than the anterior and middle hooks; and the lateral rows of hooks are more widely spaced, forming a conspicuous longitudinal area devoid of hooks. Furthermore, the lemnisci are saccate and shorter than the proboscis receptacle; and the neck is very short with a thick collar of trunk tegument, which encircles the base of proboscis. In males, the testes are in the middle third of trunk, diagonal, spherical and small relative to the body size, and there are six clavate cement glands. In females, the uterus forms a conspicuous, elongate, cylindrical egg reservoir. The new species is most similar to A. alabamensis Amin & Williams, 1983, but can be distinguished by its swollen, clavate trunk, the largest proboscis hooks being present apically and medially, smaller testes, a shorter male reproductive system relative to body size and females with a prominent uterus. They have different hosts and geographical distribution. The new species can be differentiated from Brasacanthus sphoeroides Thatcher, 2001, a similar species in a monotypic echinorhynchid genus, because the latter is larger, has smaller proboscis hooks and its lemnisci are longer than the receptacle.