{'fraction_non_alphanumeric': 0.036741214057507986, 'fraction_numerical': 0.017191541153202494, 'mean_word_length': 5.323713323713323, 'pattern_counts': {'":': 0, '<': 11, '<?xml version=': 0, '>': 4, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Effect of Food Availability on Reproduction and Growth in the Intertidal Sea Hare Aplysia juliana

The purpose of this study was to investigate the effect of a change in food availability on the growth and reproduction of the hermaphrodite sea hare Aplysia juliana.All groups of A.juliana were fed algae for five days(conditioning period),and then we stopped feeding half of each group for the subsequent five days(experi mental period)while the other half of each group were fed algae.There was a negative relationship between the ini tial body weight of A.juliana and the increment rate in body weight under the fed condition,and positive relation ships were found between the weight of A.juliana and fecundity:i.e.,the number of egg masses and the weight of them.When we stopped feeding,small individuals had more copulations than their counterparts which were under the food-rich condition although there was no increase in the number of copulations with large individuals.How ever,both the number of egg masses and the egg mass weights decreased when we stopped feeding.This implies that the degree to which small individuals divide energy into reproductive activity as males,though not as females, might increase when food availability decreases.


INTRODUCTION
Food resources show spatial and temporal variations for most organisms.Spatial distribution and abundance of foods can vary even within a season,and response to changes in food availability has a critical role in main taining the fitness of an organism.Since organisms need to allocate energy to competing functional demands that can be categorized into survival,growth and reproduction (Roff1992;Stearns1992),the degree to which organ isms allocate energy into each category should vary with food availability.
General life history theory predicts that reduced life expectancy should change resource allocation decisions in favor of increased reproductive effort (Clutton-Brock 1984;Roff1992;Stearns1992).The appropriate re sponses in invertebrates have been traced to the presence of predators(Riessen1999),a harsh abiotic environment (Roitberg et al.1993),and physical injuries (Gellar 1990).On the other hand,a species of moth,Scotopteryx chenopodiata,deprived of food as adults,increased oviposition activity(Javois&Tammaru2004),while two species of fruit flies ignored food deprivation and another fly species even decreased oviposition rate in response to these cues of reduced life expectancy (Prokopy et al. 1993).Thus,the effect of food deprivation on reproduc tive effort is a controversial topic in life history evolu tion.This paper aims to examine the effect of food depri vation as a factor of reduced life expectancy in the sea hare,Aplysia juliana.
Aplysia juliana is a common annual sea hare in our study site,Uranouchi Inlet,southern Shikoku,Japan;it is widely distributed around the coasts of Japan and over extensive parts of the Pacific,Indian and Atlantic Oceans (Hamatani2000).The adults mainly occur and reproduce from early spring to early summer.In spring,the green algae Ulva spp.(mainly U.pertusa)is the most common along the coast of Uranouchi Inlet,existing as patches on ropes,piers,floating docks and on other natural and arti ficial structures.Aplysia juliana actively eats Ulva under rearing conditions and shows a high growth rate(Care foot1970),suggesting that Ulva is a main food of A.ju-liana in the field.However,the distribution and abun dance of U.pertusa rapidly change (Choi et al.2001;Yoshida et al.2002),leading to a situation in which A.ju liana faces a rapid change in food availability during its reproductive season.Temporal dynamics of food avail ability are known to affect the growth and reproduction in opisthobranchs(Chester1996; Ito et al.1996).Herbiv orous sea hares in temperate areas might have a high plasticity in energy allocation to growth and reproduction to cope with changes in the abundance of algae in order to maximize fitness. The objective of this study is to determine how the growth in body weight and reproductive effort,in terms of mating behavior and the number and wet weight of egg masses,were affected by a change in the availability of algae in A.juliana.Since responses to food availabil ity may vary with body size,we also examined whether the effects of algal availability on growth and reproduc tion change with body weight of A.juliana. To standardize the energetic condition of individuals before the experimental period,we divided the rearing period into two parts;the conditioning period in which all aquariums were supplied with algae ad libitum ,and a subsequent experimental period in which we manipulated the food availability (Fig.2).All subgroups were fed every day abundant algae that were composed of green algae,mainly U.pertusa,and some red and brown algae during the conditioning period,from25to30March 2004.Then,we weighed them after the conditioning pe riod of5days.We stopped feeding a subgroup(N-sub group;no food)of each group and kept them for the ex perimental period,from30March to4April2004( Fig.  1).The other subgroup was continuously fed algae ad li bitum for the experimental period(F-subgroup;fed).We weighed them again after the experimental period.Before comparing the two subgroups that differed in food avail ability from each other,we divided the groups into two size classes based on the weights at the end of the condi tioning period;small(wet weight of a subgroup<100g) and large(>100g).Both subgroups in the same group were categorized into the same size class.

Individuals
To compare the relative frequency of mating activity among the subgroups,we observed the mating behavior of sea hares two or three times per day and recorded the number of copulations throughout the rearing period. Aplysia juliana is a hermaphroditic species with fully functional male and female reproductive organs,and sometimes forms mating chains of three or more animals, the one at the front acting solely as a female and the one at the rear solely as a male.Other individuals in between act as both males and females.We scored each mating pair consisting of two individuals as a copulation,and when A.juliana formed a mating chain of three or four individuals we valued them as two or three copulations, respectively.When the mating pair or mating chain formed as a circle,one was added to the number of copu lation for a mating pair(i.e.,2)or mating chain(i.e.,3or 4,respectively).We also counted the number of egg masses in each subgroup and weighed the egg masses every day.Although several egg masses were usually spawned at the same place,we could distinguish the egg masses from each other,based on the color of each egg mass.We returned the sea hares to the field after the ex periments.
We examined with Wilcoxon's signed-ranks test and Kendall's coefficient of rank correlation whether the food availability affected the growth and reproduction in A.ju liana.

RESULTS
Body weights of individuals were between3.86g and 37.86g at the beginning of the conditioning period and between9.19g and54.19g in the end of the period.All subgroups increased in wet weight during the condition ing period.On the whole,wet weights of subgroups at the beginning of the period significantly correlated with those at the end of the period(Kendall's coefficient of Initial weight of subgroups(g) Fig.3.Growth of A.juliana during the conditioning period: (a)the relationship between the initial wet weight of subgroups at the beginning of conditioning period and the final wet weight of the subgroups at the end of the conditioning period,and(b) the relationship between wet weight at the beginning of the conditioning period and the increment rate during the condi tioning period. rank correlation,•£•¥=6.68,p<0.0001) (Fig.3a)  cient of rank correlation,z=2.56,p<0.05)and had heav ier egg masses(Kendall's coefficient of rank correlation, z=4.79,p<0.0001) (Fig.5b,c,d).On the other hand,the N-subgroups partly differed from those during the condi tioning period in the performance of growth and repro duction (Fig.6).There was a significant positive relation ship between the wet weight of the N-subgroups at the beginning of the experimental period and the wet weight of egg masses that were bred during the experimental pe riod(Kendall's coefficient of rank correlation,z=3.04, p<0.01).However,no significant relationships were de tected between wet weights of subgroup and increment rates,the number of copulations and the number of egg masses(Kendall's coefficient of rank correlation, z=0.75,0.65and1.65,respectively,p>0.05).
The effect of food availability varied with the wet weight of the subgroup.Small N-subgroups more fre quently copulated than the F-subgroups consisting of small individuals(Wilcoxon's signed-ranks test,n=6, T=O,p<0.05) (Fig.7a).There was no significant differ ence in the number of egg masses between the N-and F subgroups consisting of small individuals (Wilcoxon's signed-ranks test,n=6,T=4,p>0.05) (Fig.8a).On the other hand,there was not a significant difference in the Weight of egg masses(g)Number of egg masses Number of copulations Increment rate Weight of subgroups(g) Fig.5.Growth and reproduction of A.juliana under the food-rich condition during the experimental period:the rela tionship between the initial wet weight at the beginning of the experimental period and the increment rate during the experi mental period(a),the number of copulations(b),the number of egg masses(c)and wet weight of egg masses(d).
number of copulations between the N-and F-subgroups consisting of large individuals(Wilcoxon's signed-ranks test,n=13,T=41,p>0.05) (Fig.7b).In large individu als,the F-subgroups bred more egg masses than the N subgroups(Wilcoxon's signed-ranks test,n=11,T=4, p<0.01) (Fig.8b),and the wet weights of egg masses of the F-subgroups were heavier than the N-subgroups (Wilcoxon's signed-ranks test,n=13,T=0,p<0.01).A significant difference in the wet weight of egg masses be tween the N-and F-subgroups was also detected in small size class(Wilcoxon's signed-ranks test,n=6,T=0, p<0.05).Increment rates of the F-subgroups were higher than those of the N-subgroups in both size classes (Wilcoxon's signed-ranks test,(small)n=6,T=0, p<0.05,(large)n=13,T=0,p<0.01). In our study,growth and reproduction of A.juliana var ied with body size due to the change of food availability. Under conditions of sufficient food during the condition ing and experimental periods,the subgroups consisting of small individuals had higher increment rates of wet weight than those of large individuals,and positive rela tionships were found between the weight of A.juliana and the number of egg masses and the weight of egg masses.On the other hand,after feeding was stopped,the increment rate did not show a size dependency and nei ther the number of matings nor the number of egg masses had a positive relationship with the body size. Reproduction and growth have been reported to vary in response to different levels of food availability (e.g.Chester1996;Cheung&Lam1999).It is often as sumed that organisms allocate resources differentially with changing environmental conditions.In some marine invertebrates,reproductive effort is reduced with envi ronmental stress or food depletion(Menge1974;Harvey &Vincent1989;Nakaoka1994).However,Susswein (1984)demonstrated that A.fasciata under food deple-tion spend more time mating than do indiviudals under sufficient food.In our experiment,both the number of egg masses and the egg mass weight of the F-subgroups were higher than the N-subgroups.However,small indi viduals of the N-subgroups had more copulations than their counterparts of the F-subgroups although large indi viduals did not.This implies that the mating activity in small individuals,but not large individuals,was higher under the no food conditions than under the food-rich conditions in A.juliana.
At the beginning of mating behavior of A.juliana, an individual acting as a male climbs on the back of an other individual acting as a female,and no resistance of the female is observed.The increase in the number of copulations in small individuals might result from the in crease of activity as males,not as females. Yusa(1996) found that small individuals of A.kurodai tended to mate as males in the field while large individuals did so as fe males.Since small individuals have a lower fecundity as females than large individuals,in order to maximize their reproductive success they should act as males.In our ex periment,all individuals of the N-subgroups had a low fecundity as females because of food depletion.Not only body size but also nutrient conditions might affect the sexual role in sea hares.Although there was not a signifi cant difference in the number of copulations between the N-and F-subgroups of large individuals,they might allo cate time and energy into reproductive activity as much as they can irrespective of the food condition.
In conclusion,this study has clarified that food availability changes the energy allocation between growth and reproduction and the effects depend on body size in the sea hare A.juliana.