The mouthparts of the members of the Jaera albifrons group of species (Crustacea: Isopoda)

The mouthparts of Jaera albifrons Leach, Jaera ischiosetosa Forsman, Jaera praehirsuta Forsman and Jaera forsmani Bocquet were examined with the light microscope and the Stereoscan electron microscope, and were found to be identical in all species. The structure of the mouthparts indicate that all four species feed by scouring and abrading algal or bacterial films from rocks or Fucus. Food, therefore, does not seem to be an isolating factor involved in the microdistribution of the four species on a shore.     

No cost of male mating experience on female reproductive success in the almond moth, <Emphasis Type="BoldItalic">Cadra cautella</Emphasis> (Lepidoptera; Pyralidae)

Male copulation experience may have a profound impact on female reproductive success if male reproductive investment declines over consecutive copulations and if females are unlikely to re-mate. Male reproductive investment is particularly interesting in lepidopterans because males produce dimorphic sperm: a fertilizing (eupyrene) and a non-fertilising (apyrene) sperm. In two experiments, we explored the lifetime reproductive investment of male almond moths, Cadra cautella (also known as Ephestia cautella) and examined its influence on female reproductive success. In the almond moth, females re-mate infrequently and males transfer sperm in a spermatophore. Attached to the spermatophore is a large chitinous process, the function of which is unknown. One group of males were permitted consecutive copulations with virgin females and the amount of sperm and size of the spermatophore transferred were compared for all females. We found that the number of both eupyrene and apyrene sperm per ejaculate decreased with his increased mating frequency, while the size of the spermatophore process decreased dramatically after the male’s first copulation. In a second experiment, we allowed males to mate with females throughout their lives and then compared female fecundity and fertilisation success. We found no obvious decrease in female fecundity and fertilisation success with increased male copulation experience, despite the likely reduction in male gametic investment. We discuss potential explanations for the development of this enlarged and elaborate first spermatophore of male almond moths given that it confers no clear fitness advantage to females.     

Variation in emergence of parasitic and predatory isopods among habitats at Lizard Island, Great Barrier Reef

Gnathiid isopods are one of the most abundant groups of ectoparasites on coral reef fishes. They, and other isopods, have been shown to significantly affect the health and behaviour of many reef fish. Whether isopod emergence differs among habitats on coral reefs is not known. In this study, we measured emergence rates of parasitic isopods (Gnathiidea and Flabellifera) in six habitats at two sites at Lizard Island during new moon periods in March and December 2004. Isopods were collected from the periphery and centres of micro-reefs, patch reefs, continuous reefs, and from inter-reefal habitats (sand or rubble) with 1 m² emergence traps. Sites (Casuarina and Coconut Beach) were located on opposite sides of Lizard Island. Live gnathiids were collected with light traps in November 2005 to investigate species differences between sites. At both sites, the most abundant gnathiid species was exclusive to that site. More gnathiid larvae emerged at night, and emergence of fed gnathiids (pranizae) and flabelliferan isopods was almost exclusively nocturnal. Diurnal emergence was greater at Coconut Beach than Casuarina Beach. Although emergence counts were not consistently affected by parameters such as habitat, site, or sampling period, gnathiid size and feeding state were. Where significant differences existed, gnathiids were larger and more often fed over reef borders than centrally. We suggest first stage larvae (Z1) have the largest influence on total abundance and are patchily distributed in accordance with adults from which they have recently hatched. As later stage larvae depend on fish, more successful (fed) and older larvae are found on the edges of reefs where appropriate hosts may be more abundant, or predation is lower. Gnathiids were over-dispersed in all habitats investigated, including apparently homogeneous beds of coral rubble and sand. This indicates that their distributions may be better predicted by very fine scale differences in substrate or that aggregations are the result of gregariousness and may be difficult to predict on the basis of substrate. Emergence traps collected comparatively few parasitic flabelliferan isopods. This community differed greatly from the previously described community of scavenging isopods at Lizard Island. These differences are probably the result of differences in trapping methodology.     

Interspecific territoriality and competition for food between the reef fishes Forsterygion varium and Pseudolabrus celidotus

Long-term behavioural studies were made of the blennioid fish Forsterygion varium and the wrasse Pseudolabrus celidotus in the Cape Rodney-Okakari Point Marine Reserve in New Zealand. Both male and female F. varium defended small 1 to 2 m² territories from the wrasse all year round, althoughl aggressive encounters were most frequent from December to April. Only Large P. celidotus (≧180 mm standard length) were observed to dominate the blenny in interactions. Defence of nests, which were found only on the territories of males between May and October, did not explain the distribution of F. varium aggression between the sexes and seasons. An extensive overlap in the categories and size of prey eaten suggested that protection of food was a major function of F. varium territoriality. F. varium was most frequently aggressive toward P. celidotus of an intermediate size (110 to 160 mm SL) and exhibited greatest overlap in diet with wrasses in this size lange. This dnected the study toward examining the effect of F. varium on the feeding activity of P. celidotus. Within a shallow, Leterogeneous reef habitat, feeding pressure by P. celidotus (bites/are/time) was inversely related to the density of F. varium. Removal of F. varium from small 5x5 m quadrats resulted in large increases in wrasse feeding pressure, suggesting that the blenny influences the foraging of wrasses within their home ranges. When F. varium were removed from the entire home ranges of five 1+yr (110 to 130 mm SL) P. celidotus, these fish exhibited relative increases in both feeding rate and foraging time. The results suggest that P. celidotus grow through a period during which individuals compete with F. varium for food, adding support to the contention that territoriality in F. varium functions to preserve its food supply.     

Sex ratio and host size in a parasitoid wasp

Summary Parasitoid wasps often lay male eggs in small hosts and female eggs in larger hosts. The selective advantage of this strategy can be explained by assuming wasp fitness increases with host size and that this fitness increase is greater in females than in males. I conducted experiments to test a model based on this explanation and found the results generally supported the model with one exception; unlike what the model assumed, these wasps were unable to adjust their offspring sex ratios in each generation to different host size distributions. This finding suggests an alternate view as to how selection might operate in the evolution of parasitoid sex ratios.     

Social inhibition of maturation in females of the temperate wrasse Pseudolabrus celidotus and a comparison with the blennioid Tripterygion varium

In two temperate reef fish, Pseudolabrus celidotus (Bloch and Schneider) and Tripterygion varium (Bloch and Schneider) studied near Leigh, New Zealand, most spawning activity was concentrated during the first 2 months of spawning seasons which lasted about 5 months. In P. celidotus, maturation and spawning of first-year females (0+) was delayed with respect to older (1+yr) females. Within the 0+ age class, the minimum size of maturation declined as the spawning season proceeded. However, in all females of T. varium, ripening and spawning took place over the same time ranges. Observations on the seasonal patterns of female aggression suggested that larger female P. celidotus were socially inhibiting the maturation of small females. The level of interaction was high compared to that in T. varium, and reached a peak over the onset of the spawning season. This hypothesis was tested by the removal of larger (1+yr) female P. celidotus from a field population. The remaining 0+ females increased in ovary weight and matured earlier than those in an undisturbed area. We argue from this experiment that it is of advantage for P. celidotus females to spawn early in the season and of advantage to inhibit other females from doing so. Two possible reasons are suggested, the first applying to sexchanging species such as P. celidotus, the second to temperate-water fishes in general.     

Worker population structure and gyne production in the ant Myrmica

Summary Wild colonies of Myrmica rubra L. were sampled and cultured in the laboratory to assess their reproductive capability. Correlation analysis was then used to relate the reproductive performance to a number of worker population characteristics. This revealed an association between the magnitude of gyne production and the proportion of nurses in the population. The absence of big workers also increased gyne production.Artificially composed cultures were then made and used to confirm greater resistance of nurses and small workers to queen domination.It is suggested that rapidly growing colonies will have higher proportions of young nurse workers refractory to queens and able to deliver the food necessary for gyne production. Such colonies could optimise their reproduction in this way.     

Invertebrates of the upper chamber,Gatún Locks,Panama Canal,with emphasis on Trochospongilla leidii (Porifera)

Observations were made on the horizontal distribution of certain invertebrates on the walls and floor of the upper chamber of the Gatún Lock system of the Panama Canal. The hydroid Cordylophora caspia (Pallas) and the gastrophod Neritina usnea Röding extended the full length of the chamber; the oligochaete Marionina sp. was confined to the upper half of the chamber (adjacent to Gatún Lake), and the amphipod Gitanopsis tortugae? Shoemaker, the isopod Munna sp. and the bivalve Mytilopsis sallei (Recluz) to the lower half; the sponge Trochospongilla leidii (Bowerbank) was distributed from the upper end to near the lower end of the chamber. A peculiar wedge-shaped distribution of T. leidii is thought to be a response to the influence of slight increases in salinity. Morphological observations on T. leidii are presented.     

Infant care,infanticide, and female reproductive strategies in polygynous groups of common marmosets (Callithrix jacchus)

Reproduction in marmoset and tamarin groups is typically restricted to a single dominant female, but it is unclear why subordinate females tolerate delayed reproduction. The presence of two breeding females in free-ranging groups of common marmosets (Callithrix jacchus) presented a unique opportunity to examine differences in the reproductive strategies of dominant and subordinate females. Three groups were monitored for 12–18 months at a forest reserve in northeastern Brazil. Data on infant care were collected during two consecutive all-day follows every 10 days until the infants were 2 months old. Carrying patterns for infants born to dominant females were similar to those observed in groups containing a single breeding female. All group members over 5 months of age participated in infant care, and dominant females allowed some group members to carry their infants from the 1 st day of life. In contrast, subordinate females were protective of their offspring and were their sole caretakers for at least a week following birth. One infant born to a subordinate was killed in an attack involving the dominant female. Overall, dominant females gave birth to more infants and had higher infant survival than did subordinate breeding females. subordinate females were successful in rearing young only when the timing of births was such that they did not overlap with the dependency period of infants born to the dominant female. These patterns suggest that subordinate females may face resource competition, especially over access to helpers. In times of severe competition, subordinate females that delay reproduction may be avoiding a wasted reproductive effort.