Normal and atypical nesting behaviour of Copris lunaris (L.): comparison with related species (Coleoptera, Scarabaeidae)

Abstract. 1. The lifecycle, mating and larval behaviour of Clunaris are described. Adults appeared in the autumn and nested in the following spring. The female beetle remained in the nest with the brood and could nest again the following year.
2. Nesting was initiated when virgin females were mated in the spring. Brood balls were formed by techniques sirnilar to those used by Scarabaeini. The female beetle left the nest soon after the first imagos broke out of the brood balls.
3. Nesting behaviour was readily modified by external conditions. Many parts of the sequence could be repeated or omitted. The female beetle left the nest if the brood was removed, but she remained for longer than usual if younger brood was substituted near the end of the normal nesting period.
4. Certain experimental conditions released behaviour patterns typical of other species. These were formation of superficial nests or of two-chambered nests, oviposition before completing the brood ball, and coating of the brood balls with soil (all found in other Coprina), as well as ball rolling and ball burial (found in Scarabaeini). The results are discussed in relation to the evolution of Copris nesting behaviour.     

Density-dependent predation and implications for stock enhancement with Japanese flounder

In laboratory predation trials kinsen-gani crab Matuta lunaris rarely preyed on hatchery-reared (HR) Japanese flounder Paralichthys olivaceus , even at extremely elevated prey densities ( c . 90 fish m⁻²), but fed readily on sacrificed Japanese founder. This suggests that under similar conditions in the wild predator-prey interactions between kinsen-gani and juvenile Japanese flounder are likely to be weak. Larger Japanese flounder readily cannibalized smaller conspecifics, suggesting that within-release group cannibalism may contribute considerably to post-release mortality of HR Japanese flounder when sufficient size variation exists within groups of released fish. Kinsen-gani presence had no effect on within-release group cannibalism rates of large Japanese flounder on small Japanese flounder. Within-release group cannibalism rates were significantly affected by densities of smaller (prey) fish, implying that the number of fish released (and thus post-release densities) in stock enhancement programmes may significantly affect post-release mortality rates. The probability of within-release group cannibalism increased rapidly as the cannibal-to-prey size ratio exceeded 1.6, suggesting that minimizing size variation of released HR individuals will reduce post-release cannibalism rates. These results have implications for Japanese flounder stock enhancement release strategies, and may be applicable to other finfish stock enhancement programmes.     

Predator-prey interaction between hatchery-reared Japanese flounder juvenile, Paralichthysolivaceus, and sandy shore crab, Matutalunaris: daily rhythms, anti-predator conditioning and starvation

Predator-prey interaction between sandy shore crab, Matuta lunaris (Forskål, 1775), and juvenile Japanese flounder, Paralichthys olivaceus (Temminck et Schlegel), was investigated under controlled laboratory conditions. Possibility of training and conditioning hatchery-reared flounder to avoid predators was also examined. Crabs took over 75% of their daily ration at night when they were given access to prey 24 h a day. Large (64.8±5.4 g)- and medium (30.68±3.33 g)-sized crabs ate ca. 5.5±1.45 and 3.9±1.99 individuals of flounder (TL=4.96±0.23 cm) a day, respectively. When flounder juveniles that have experienced predation pressure by crabs encountered predators again, they exhibited better survival compared to the naive fish. Flounder juveniles were also conditioned either using small and, thus, benign predators, or large crabs over fence. The conditioned fish with either method were better able to avoid capture by crabs than naive fish, revealing that learning process should play an important role in their predator avoidance. Anti-predator performance was also compared between starved and fed flounder juveniles. Fed fish were rarely eaten by predators after 3 h of exposure, whereas starved fish continued to be eaten. Our results suggest that stock-enhancement program of Japanese flounder can be improved by applying proper feeding protocol and conditioning to avoid predators prior to release. Present research supports the idea that behavioural and ecological consideration for the target species is indispensable for the success of stock enhancement.     

Parental behaviour in Copris lunaris (Coleoptera, Scarabaeidae): care and defence of brood balls and nest

Abstract. 1. Nesting female beetles righted brood balls (so as to replace the egg or larva in the uppermost position) and repaired damaged balls. This behaviour required the presence of an egg or larva in the ball, or of a short-lasting material found just after oviposition. The shape of the ball was also a righting stimulus since artificial ellipsoids were stood on end.
2. Balls containing dichloromethane extracts of C.lunaris brood were righted and repaired. Eggs and larvae of several other Scarabaeidae did not release these responses but were destroyed.
3. Righting behaviour was released when brood was absent from the top of the ball. The beetle then crawled vertically downwards and, if it encountered the displaced apex, a novel rolling action followed which automatically turned the ball towards the correct position.
4. An opening made in the nest was repaired with soil excavated from the chamber floor. Clunaris adults and Aphodius fossor larvae were attacked if they were encountered in the nest.     

The evolution of parental behaviour in Scarabaeinae (Coleoptera, Scarabaeidae): an experimental approach

ABSTRACT.

• 1 Dung beetle lifestyles are reviewed. Most Scarabaeinae lay their eggs in dung masses that are packed into underground chambers, but Coprini and Scarabaeini typically lay their eggs in free-standing brood balls and it is in these tribes that parental care of the brood has evolved.
• 2 Brood balls are constructed by aggregating fragments of dung. This technique is derived from the method of gathering dung at the surface. Larvae developing in brood balls are better protected against dehydration and parasite attack. The repair technique of Scarabaeine larvae preadapts them to life in brood balls.
• 3 Parental care by Copris lunaris depends on appropriate responses by the female to the brood, and it has the selective advantage of protecting the brood against parasites. Preadaptations for parental care in‘non-brooding’Coprini are discussed.
• 4 Variations in the basic Copris nesting behaviour are summarized. Similar variations can occur spontaneously in C.lunaris and can also be released by unusual circumstances.
• 5 C.lunaris females could in principle cooperate but certain factors have prevented this social evolution. The significance of the transient cooperation with the male beetle is discussed.