Natural populations of the Closterium ehrenbergii (Desmidiales, Chlorophyta) species complex in Nepal

Several natural populations of the Closterium ehrenbergii Meneghini ex Ralfs species complex were collected in Nepal, in October–December 1982. Water temperature and pH were also recorded. Clonal isolates from these populations were identified to one of four mating groups (H, I, J and M) by test crossing with standard mating-type strains of known mating groups. Groups H and M have smooth walled zygospores, while Groups I and J have scrobiculated zygospore walls. Several undetermined isolates were found in some population samples. In contrast to the previously reported population samples from Nepal, especially from dried soil samples, some of these populations appeared to be rather heavily loaded with mutations that are deleterious to the sexual cycle (i.e. sexual compatibility, zygospore formation and germination). By genetic analysis, a zygote maturation-defective mutation (zym) was detected. One reason for such a heavy genetic load was suggested to be that most population samples had been maintained exclusively by asexual reproduction for a long period in large lakes and nearby ponds, or left-over vegetative populations in paddy fields after other members entered into dormancy through sexual reproduction. The significance of studying such mutations at sexual gene loci is discussed in the light of speciation problems in microalgae.     

Sexual Selection of Zorion guttigerum Westwood (Coleoptera: Cerambycidae: Cerambycinae) in Relation to Body Size and Color

Zorion guttigerum is a flower-visiting longhorned beetle endemic to New Zealand. Sexual selection of this species in relation to the body size and color form of different sexes was investigated in the field. The population sex ratio, based on censuses of feeding and mating sites (flowers), is male-biased. Females are significantly larger than males. Both sexes have antennae of similar length but the antennal length relative to the elytral length is greater in males than in females, and the antennal length of males increases more with an increase in body size than that of females. Both sexes have dark blue (DB) and yellowish-brown (YB) individuals. Both pair-bonded and solitary males are similar in elytral and antennal length. In pair-bonded males, DB individuals are significantly more numerous than YB ones, but in solitary males, the number of both color forms is similar. Males tend to have territory protection behavior, fighting with and chasing away rival males from feeding and mating sites. Larger males usually win the fight but the size-dependent fighting advantage does not translate into mating success. Male color plays an important role in mating success, with DB males having a significantly better chance to mate than YB males. Furthermore, male body size and color also have interactions in mating success: males of DB color morph obtain a greater mating advantage according to body size. Pair-bonded females are significantly larger and have longer antennae than solitary females, suggesting that males prefer larger females for mating. In addition, females of DB color morph with longer antennae are also preferred by males for mating. The significance of these findings is discussed.     

Testosterone,growth and the evolution of sexual size dimorphism

The integration of macroevolutionary pattern with developmental mechanism presents an outstanding challenge for studies of phenotypic evolution. Here, we use a combination of experimental and comparative data to test whether evolutionary shifts in the direction of sexual size dimorphism (SSD) correspond to underlying changes in the endocrine regulation of growth. First, we combine captive breeding studies with mark‐recapture data to show that male‐biased SSD develops in the brown anole lizard (Anolis sagrei) because males grow significantly faster than females as juveniles and adults. We then use castration surgeries and testosterone implants to show that castration inhibits, and testosterone stimulates, male growth. We conclude by reviewing published testosterone manipulations in other squamate reptiles in the context of evolutionary patterns in SSD. Collectively, these studies reveal that the evolution of SSD has been accompanied by underlying changes in the effect of testosterone on male growth, potentially facilitating the rapid evolution of SSD.     

Variation in courtship rate in the fiddler crab Uca annulipes: is it related to male attractiveness?

We investigated among-male variation in courtship waving inthe fiddler crab Uca annulipes. Wave rate is positively correlatedwith both male carapace size and relative claw size (controlledfor body size), and relative claw size is positively correlatedwith an index of body condition. An experimental reduction inthe availability of food decreased male wave rate. These datasuggest that some of the variation in wave rate among malesis due to variation in male condition combined with energeticcosts to waving (differential costs). However, we also foundthat the correlation between male size and wave rate decreasedover the semilunar cycle. Later in the cycle, smaller malesincrease their wave rate relative to that of larger males. Previouswork has shown that females are more likely to accept a smallermale as a mate later in the cycle. We suggest that smaller malesinvest disproportionately more in courtship later in the cyclebecause the potential benefits are greater due to their increasedattractiveness to females (differential benefits). Alternativeexplanations for the observed temporal trend are also discussed.     

Role of neurotransmitters in coordination of male sexual behavior

The review considers the published data and the results obtained by the author on the role of monoamines (serotonin, dopamine, and noradrenaline) in the control of male sexual behavior. In the above respect, the central mechanisms of action of the neurotransmitters are discussed.