Does female nuptial coloration reflect egg carotenoids and clutch quality in the Two-Spotted Goby (Gobiusculus flavescens, Gobiidae)?

Summary

1 - Carotenoid-based ornamentation has often been suggested to signal mate quality, and species with such ornaments have frequently been used in studies of sexual selection.

2 - Female Gobiusculus flavescens (Two-Spotted Goby) develop colourful orange bellies during the breeding season. Belly coloration varies among mature females, and previous work has shown that nest-holding males prefer females with more colourful bellies. Because males invest heavily in offspring during incubation, the evolution of this preference can be explained if colourful females provide males with eggs of higher quality.

3 - We tested this hypothesis by allowing males to spawn with ‘colourful’ and ‘drab’ females and comparing parameters including egg carotenoid concentration, clutch size, hatchability and larval viability between groups. We also investigated relationships between egg carotenoid concentration and clutch quality parameters.

4 - Eggs from colourful females had significantly higher concentrations of total carotenoids than drab females, and photographically quantified belly coloration was a good predictor of egg carotenoid concentration.

5 - Colourful females produced slightly larger clutches, but female belly coloration was not related to any measure of clutch quality. In addition, there were no significant relationships between egg carotenoids and clutch quality. Females with high levels of egg carotenoids spawned slightly earlier, however, possibly because they were more ready to spawn or because of male mate choice.

6 - Our results call into question the generality of a causal link between egg carotenoids and offspring quality.

Freshwater finfish biodiversity and conservation: an Asian perspective

Aspects on biodiversity and conservation of the ichthyofauna in the Asian region, in comparison to that of Africa, Europe and North America have been relatively less documented. This paper attempts to evaluate the above aspects in the East, and South and Southeast Asia based on available information in the literature. The familial diversity in inland waters in Asia (121 families) is considerably higher than in African and Latin American. Also, the finfish faunal diversity of 21 major river basins in East, and South and Southeast Asian indicate that species diversity is not necessarily related to familial diversity. The fish fauna in the region considered presently is highly diverse with an estimated cumulative total of 7447 species. Amongst the freshwater fishes the dominant groups are cyprinids (Cyprinidae, about 1000 species), loaches (about 400 species) of the families Balitoridae and Cobitiidae, gobids (Gobiidae, 300 species), catfishes (Bagridae, about 100 species), and the Osphronemidae (85 species). In the region, 462 freshwater finfish species are reckoned to be threatened, accounting for 17.5% of the all finfish species in this status in the world. In the region there are 66 species that are critically endangered and/or endangered, of which 32 are cyprinids, 14 of which are endemic to Lake Lanao, Mindano Island, Philippines. The diversity of freshwater fish species in the region was significantly related to the land area of the different countries in the following manner:

ln (species ratio) = ln 0.384 (land area in km2) + 0.651( R² = 0.628; p < 0.001).

In addition, the fish species diversity in the major river basins of the region was also found to be positively related to the basin area:

ln (Species richness index) = - 0.789 ln (Area) + 9.368( R² = 0.748; p < 0.001).

Based on above relationship, the predicted fish species richness did not necessarily correlate to river basin size, and rivers with small basins were shown to have high indices. The paper also attempts to evaluate the reasons affecting fish species diversity in the region and suggests mitigating measures.

Endemic freshwater finfish of Asia : distribution and conservation status

Freshwater finfish species richness and level of endemism in East, and South and South-East Asia that included 17 nations were studied using available databases, and included nation-wise distribution, habitat types, and conservation status. The number of endemic finfish species in the region was 559, belonging to 47 families. Families Cyprinidae and Balitoridae accounted for 43.5% and 16.2% of the total number of endemic species in the region, respectively, followed by Sisoridae (25), Gobiidae (20), Melanotaeniidae (19), and Bagridae (16), and the other 41 families had at least one endemic species. Nation-wise the most number of endemic freshwater finfish species occur in India (191), followed by China (88), Indonesia (84), and Myanmar (60). In India, the endemic species accounted for 26.4% of the native freshwater fish fauna, followed by South Korea (16.9%), the Philippines, (16.3%) and Myanmar (15.7%).

Statistically significant relationships discerned between the number of indigenous and endemic species richness to land area (X_la in 10³ km²) of the nations in the region were, Y_in = 218.961 Ln(X_la) – 843.1 (R² = 0.735; P < 0.001) and Y_e = 28.445 Ln X_la−134.47 (R² = 0.534; P < 0.01), respectively, and between indigenous and endemic species richness was Y_e = 0.079X_n− 1.558 (R² = 0.235; P < 0.05).

The overall conservation status of endemic finfish in Asia was satisfactory in that only 92 species were in some state of vulnerability, of which 37 species (6.6%) are endangered or critically endangered. However, the bulk of these species (83.7%) were cave- and or lake-dwelling fish. However, nation-wise, the endemic freshwater finfish fauna of the Philippines and Sri Lanka, based on the imperilment index, were found to be in a highly vulnerable state. Among river basins, the Mekong Basin had the highest number of endemic species (31.3%). The discrepancies between databases are highlighted and the need to consolidate information among databases is discussed. It is suggested that the Mekong Basin be considered as a biodiversity hotspot, and appropriate management strategies be introduced in this regard.