Courtship Sounds Advertise Species Identity and Male Quality in Sympatric Pomatoschistus spp. Gobies

Acoustic signals can encode crucial information about species identity and individual quality. We recorded and compared male courtship drum sounds of the sand goby Pomatoschistus minutus and the painted goby P. pictus and examined if they can function in species recognition within sympatric populations. We also examined which acoustic features are related to male quality and the factors that affect female courtship in the sand goby, to determine whether vocalisations potentially play a role in mate assessment. Drums produced by the painted goby showed significantly higher dominant frequencies, higher sound pulse repetition rates and longer intervals between sounds than those of the sand goby. In the sand goby, male quality was predicted by visual and acoustic courtship signals. Regression analyses showed that sound amplitude was a good predictor of male length, whereas the duration of nest behaviour and active calling rate (i.e. excluding silent periods) were good predictors of male condition factor and fat reserves respectively. In addition, the level of female courtship was predicted by male nest behaviour. The results suggest that the frequency and temporal patterns of sounds can encode species identity, whereas sound amplitude and calling activity reflects male size and fat reserves. Visual courtship duration (nest-related behaviour) also seems relevant to mate choice, since it reflects male condition and is related to female courtship. Our work suggests that acoustic communication can contribute to mate choice in the sand goby group, and invites further study.     

The Role of Agonistic Sounds in Male Nest Defence in the Painted Goby Pomatoschistus pictus

Animals often vocalize during territorial challenges as acoustic signals may indicate motivation and fighting ability and contribute to reduce aggressive escalation. Here, we tested the function of agonistic sounds in territorial defence in the painted goby. Pomatoschistus pictus, a small vocal marine fish that defends nests during the breeding season. We first measured the number of times a male approached, avoided, explored, entered and exited two unattended nests associated with either conspecific agonistic sounds or a control: silence or white noise. Acoustic stimuli were played back when the male approached a nest. In a second experimental set, we added visual stimuli, consisting of a conspecific male in a small confinement aquarium near each nest. Even though we found no effect of the visual stimuli, the sound playbacks induced similar effects in both experimental conditions. In the sound vs. silence treatment, we found that when males approached a nest, the playback of conspecific sounds usually triggered avoidance. However, this behaviour did not last as in longer periods males visited nests associated with agonistic sounds more often than silent ones. When the control was white noise, we found no significant effect of the playback treatment in male behaviour. Although we cannot exclude the possibility that other sounds may dissuade nest occupation, our results suggest that agonistic sounds act as territorial intrusion deterrents but are insufficient to prevent nest intrusion on their own. Further studies are needed to test the significance of sound production rate, spectral content and temporal patterns to deter territorial intrusion in fish.     

Behaviour and success of sneaker males in the sand goby, Pomatoschistus minutus

In this study we investigated in laboratory conditions the presence of alternative reproductive tactics in the sand goby and describe proximate factors affecting their expression and success. We describe the reciprocal interactions of resident males, females, and sneaking males. The pre-spawning phase proved to be important for successful nest intrusions by sneakers. The number of sneakers had no effect on the frequency of successful intrusions. When small males had exclusive access to nest sites, they built a nest and courted females, showing a full behavioural repertoire. The intensity of courtship was, however, strongly positively correlated with body size. Using microsatellite DNA markers we assessed paternity shares of territorial and sneaker males in a subset of all replicates. Following successful nest intrusion sneaker males fertilised 5–10% of the eggs. Our interpretation of the results is that sneaking in the sand goby is a conditional tactic, one that is less successful than the normal nest guarding behaviour, at least for one spawning event. Received in revised form: 9 March 2001 Electronic Publication     

Life history traits of Pomatoschistus minutus in the Rhône Delta, France

Life history traits and migratory status of the Sand goby Pomatoschistus minutus were investigated in a brackish lagoon of the Rhône river Delta (Mediterranean Sea, south of France).     

The identification of Pomatoschistus minutus (Pallas) and Pomatoschistus lozanoi (de Buen) (Pisces, Gobiidae)

Sand gobies areextremely abundant in coastal waters and estuaries. Pomuroschistus lozunoi tends to be overlooked due to identification problems. This paper summarizes the characteristics to distinguish P. lozanoi from P. minutus and presents a new distinctive feature that allows identification of juveniles from 15-20 mm standard length onward. The known geographic distribution of P. lozanoi is extended northward to 53°30' N and southward to 40°N on the coast of Europe. In northern Europe P. loxmoi seems better adapted to the estuarine habitat than previously thought.     

Size-assortative nest choice in the absence of competition in males of the sand goby,Pomatoschistus minutus

Synopsis Size-assortative choice of nest site is commonly found among fish with paternal care. This pattern can be explained either by the superior competitive ability of large males for preferred large nests, or by a choice of nest size that is related to the male's own body size. Choice of nest size was studied in males of a small marine fish, the sand goby Pomatoschistus minutus, by providing artificial nest sites in laboratory and field experiments. A positive correlation between nest size and male size, indicating a size-assortative nest choice process, was found in both aquarium and field experiments. This is argued to be the outcome of a preference for an optimal nest size and not to be due to competition, as (a) a surplus of nest sites was available to the individuals in nature; (b) in the aquarium experiments, single males of all sizes, when offered a choice between a smaller and a larger nest site, showed a preference for nests in proportion to their body size and not for the largest available nests; and (c) in the aquaria, when single males were offered only a small or only a large nest site, small males abstained from building nests in the large sites, whereas in the small nest sites males of all sizes built nests. My conclusion is that size assortative nest choice occurred in the absence of competition, which thus is not a necessary condition for size-assortative nesting, contrary to what is commonly assumed in many studies. This preference may represent a compromise (or trade-off) between the advantage of a nest large enough to accommodate many eggs and a smaller one with lower maintenance and defence costs.     

Tolerance, behaviour and oxygen consumption in the sand goby, Pomatoschistus minutus (Pallas), exposed to hypoxia

Behavioural and metabolic reactions of Pomatoschistus minutus (Pallas) exposed to various degrees of hypoxia were studied. At 15°C and 20‰ mortality was 50% at 15.2% oxygen saturation. Avoidance and oxygen saturation showed a linear inverse relationship. At levels lower than 60% saturation increased activity occurred; avoidance was significant at 30% saturation. Active, routine and standard MO₂ correlated linearly with weight at 6 and 15°C (salinity = 19‰). During hypoxia at 15°C routine MO₂ rose significantly at 60–50% and 40–30% saturation expressed either as MO₂ during longer periods at night or MO₂ at shorter intervals during the day. Standard MO₂ was unaffected by hypoxia at 15°C. Haemoglobin concentration was significantly increased when P. minutus was acclimatized to 35% saturation.     

Expected future reproductive success and paternal behaviour in the sand goby, Pomatoschistus minutus (Pisces, Gobiidae)

We studied egg care and guarding behaviour in the paternal sand goby, Pomatoschislus minutus , in relation to egg number and age. A male's expected reproductive success is assumed to increase with larger egg masses and older eggs. Non-shareable care, i.e. fanning, was higher in larger and older egg masses. Egg age explained 65% and egg mass size 22% of the total variation in the amount of fanning performed by a male. Contrary to expectation, egg removal did not affect a male's fanning behaviour, Males that were approached stayed longer in the nest when they guarded larger egg masses. Males with older eggs were also more reluctant to leave the nest. The time since a male had been chased away from his nest until he returned decreased as the season progressed. The results are discussed in relation to tradeoffs between present and future reproductive events.     

Egg presence, egg loss, and female mate preferences in the sand goby (Pomatoschistus minutus)

We studied the effect of egg presence on female mate choicein a fish with paternal care. Females who were allowed a freechoice between two males mated within a shorter time than femaleswho were randomly assigned to a particular male. When a secondfemale was allowed to choose among the males, she preferredthe same male as the previous female. This result shows thatfemales are concordant in their mate choice. When the initialfemale was randomly assigned to mate with one of two males (forcedchoice), the second female mated randomly with respect to thefirst one. Thus females do not prefer males with eggs. If theinitial female was given a free choice, but the eggs were removedfrom the chosen male, the test female mated randomly. When boththe males initially had mated but one randomly determined male'seggs were removed, the test female preferred the male who wasstill guarding eggs. These experiments show that females avoidspawning in unsuccessful nests. When the females in the freechoice/egg removal experiment mated with the unsuccessful malethere was a considerably bigger size difference in favor ofthis male than when the females mated with the other male. Weconclude that female sand gobies show clear mate preferences,but that they do not prefer males with eggs over males withouteggs. They do, however, avoid mating with males guarding unsuccessfulnests. We therefore suggest that egg loss could be an importantfactor selecting for egg preference.     

Temperature selection and avoidance in the sand goby,Pomatoschistus minutus (Pallas), collected at different seasons

Synopsis The sand goby from the Oslofjord, Norway, is extremely eurythermal. In spring and autumn it avoids temperatures lower than about 4° C, in summer 6° C. Acclimation did not influence the lower avoidance temperature, but the critical thermal maximum, the upper avoidance temperature and the temperature where the whole fish darkened (the darkening temperature) varied with acclimation and season. The darkening temperature is suggested to be the upper temperature limit with the greatest ecological significance. The fish, collected at different seasons darkened at between 19.5 and 22° C. In the field the fish is not found at 20° C and higher.The preference temperature varied with season and with acclimation temperature, generally with low precision. In May, the preference temperature was 13.5° C, that is higher than the ambient temperature of 10° C. In summer, the temperature in sampling locality and preference temperature was the same, 17 and 16.5° C respectively. In October, temperature preference was 7.5° C as compared to 9° C in the field. The variation is explained as a behavioural thermoregulation to direct the fish towards optimal conditions at any time.The seasonal variation in preference temperature can not be ascribed only to seasonal variation in temperature, that is an acclimation phenomenon, but other factors are operative as well, factors which will modify the temperature tolerance in the fish.     

Genetic differentiation between populations of Pomatoschistus minutus from the Bristol Channel and the Adriatic

Samples from two populations of the gobiid fish species Pomatoschistus minutus (Pallas) were compared electrophoretically over 31 protein loci. The population from the Lagoon of Venice was shown to possess an extra LDH staining region, not present in P. minutus from Wales or any other congeneric population. The manifestation of this additional LDH band is strongly suggestive of a distinct genetic locus. The two populations have a relatively low overall I value even if this disparity in LDH is neglected. This is largely a result of virtually complete differentiation at two other Ldh loci. It is suggested that the large contribution by 3 out of the 4 Ldh loci to population differentiation, may indicate a specific adaptive response by the Venetian population to the unusual conditions of its habitat.     

四川南充崖沙燕的洞巢生物学

20 0 3年 2～ 6月 ,通过观察法对崖沙燕福建亚种的洞巢进行了考察。崖沙燕巢多筑于水边沙质硬土悬壁的沙土与黄壤交错的沙土层 ,且主要选择在沙土顶部与黄壤交界的部位啄洞营巢 ,喜利用旧巢洞。巢洞呈椭圆形、坑道状 ,多单洞道 ,洞末端扩大成椭球形巢室 ,具巢的洞深 ( 64 3 8± 1 1 73 )cm(n =5 0 )。巢室内外温度差异大 ,而巢室内昼夜温度稳定。繁殖力高、体型大的个体占据中心区深洞繁殖 ,巢多呈半圆状。窝卵数 ( 3 89± 0 92 )枚 (n =3 6) ;多数巢内有一枚卵未孵出 ( 63 3 %) ,孵化率 83 0 4%。     

Threat-sensitive Nest Preferences in Male Upland Bullies,Gobiomorphus breviceps

A male's ability to acquire and defend a nest site against competitors is an important requirement for successful breeding in many fish species. In the upland bully Gobiomorphus breviceps (Eleotridae), not all males are successful in gaining ownership of nesting rocks; therefore, male-male competition may be important in nest acquisition. Although larger nests have the potential to hold more eggs, in nature there is a preferred nest size well below the maximum available. I found that in over 88% of dyadic contests, the larger male was successful in acquiring the single nesting site provided. When males were individually given a choice of two artificial nest rocks, they consistently preferred the larger nest. These results suggest that larger males have the ability to occupy the largest nests. In the presence of a trout predator, males preferred nests with three closed sides 93% of the time. This preference disappeared when the threat was a conspecific. This shows that while males were choosing the larger nests their decisions were also threat-sensitive.     

A note on the existence of a well-developed swimbladder in the bottom-living goby Pomatoschistus minutus

The swimbladder in the sand goby, Pomatoschistus minutus , collected in shallow waters of the Oslofjord, Norway, was studied. As the literature on swimbladders in gobies appeared to be confusing, a short review of relevant literature has been made. On average, the volume of the swimbladder in the sand goby expressed as percentage of the body weight was found to be 4·7 % in May and 2·5 % in June. The significance of this volume variation is discussed.     

Mate preference for multiple cues: interplay between male and nest size in the sand goby, Pomatoschistus minutus

Female mating preferences are often based on more than one cue.In empirical studies, however, different mate choice cues aretypically treated separately ignoring their possible interactions.In the current work, we studied how male body size and sizeof the male's nest jointly affect mate preferences of femalesand gobies, Pomatoschistus minutus. The females were givena binary choice between males that differed either in body sizeor size of their nest or both. We found that neither body sizenor size of the nest alone affected male attractiveness, buttogether these 2 cues had a significant effect. Specifically,large males were more popular among females when they had alarge nest than when they occupied a small nest. The resultssuggest that if interaction effects between multiple mate choicecues are not considered, there is a danger of ignoring or underestimatingthe importance of these cues in sexual selection by female choice.     

Water turbidity by algal blooms causes mating system breakdown in a shallow-water fish, the sand goby Pomatoschistus minutus

Eutrophication as a result of human activity has resulted in increased algal blooms and turbidity in aquatic environments. We investigated experimentally the effect of algal turbidity on the mating system and sexual selection in the sand goby, Pomatoschistus minutus (Pallas), a marine fish with a resource-defence mating system and paternal care. Owing to male-male competition and female choice, large males can monopolize multiple mates, while some males do not achieve mating at all. We show that the number of eggs laid was the same in both turbid and clear tanks but that mating success was more evenly distributed among males in turbid than in clear water. The opportunity for sexual selection was lower in turbid conditions. In turbid conditions mating success was less skewed towards large males. Our results suggest that increased turbidity can change mating systems and decrease the opportunity for sexual selection as well as selection intensity.     

Genetic mating patterns studied in pools with manipulated nest site availability in two populations of Pomatoschistus minutus

Pomatoschistus minutus show paternal care in a resource defence mating system. We investigated the effect of nest-site availability on parasitic spawning. Each experimental pool contained four potentially nest-building males, four females and nests-sites in shortage (2) or excess (6). Both treatments were conducted in two populations; one with natural nest-sites in excess, one with a nest-site shortage. Microsatellite-DNA revealed that all nest-holders had fertilized most of the eggs they tended. Yet, 35% of the nests contained eggs fertilized by another male and 14.4% of the males had performed parasitic spawning. There was no site or treatment effect. Several females spawned in two nests, which coincided with parasitic spawnings, suggesting a cost to the nest-holder in terms of lost mating success. Nest-holders with and without eggs and non-nesting males all spawned parasitically, generating a significantly lower opportunity for sexual selection compared to if there had been no parasitic spawning.     

Effects of a low oxygen environment on parental effort and filial cannibalism in the male sand goby, Pomatoschistus minutus

In fish, brood cycling parental males sometimes eat some orall of their eggs, a behavior termed filial cannibalism. Wetested predictions of filial cannibalism models related to thecost of parental care in the male sand goby, Pomatoschistusminutus, by increasing the parental effort (fanning expenditure)through reduced levels of dissolved oxygen to 39% in an experimentalgroup, whereas a control group had fully saturated water. Malesshowed both full-clutch cannibalism and partial-clutch cannibalismin both treatments. Giving the males one to three females tospawn with, we found that small clutches were completely eatenmore often than were larger ones, whereas partial-clutch cannibalismwas not affected by clutch size. Although treatment did notaffect filial cannibalism, it did affect a male's energy statesuch that males in the low oxygen treatment lost more body fat,indicating a greater fanning effort. This shows that males inthe low oxygen treatment allocated more energy to the presentbrood, potentially at the expense of future reproductive success.Our study strongly suggests that filial cannibalism in malesand gobies represents a strategic life-history decision asan investment in future reproductive success, and is not triggeredby a proximate need for food necessary for the male's own survival.Furthermore, males in the low oxygen treatment built nests withlarger entrances, and were less likely to rebuild their nestsafter destruction. Presumably, this makes fanning easier butthe nest more vulnerable to predators, suggesting a trade-offbetween fanning and nest defense.     

Temperature affects operational sex ratio and intensity of male-male competition: an experimental study of sand gobies, Pomatoschistus minutus

The operational sex ratio is intimately related to the intensityof sexual selection, but factors governing variation in theoperational sex ratio and their effects on mating competitionare still poorly understood. In this study, temperature wasfound to affect both the operational sex ratio and the intensityof male-male competitive interactions in the sand goby [Pomatoschistusminutus (Pallas)]. In an experiment with two different temperaturetreatments, the operational sex ratio became male biased inthe warm treatment (15°C) and males in that treatment interactedmore frequendy than in the cold treatment (8.5°C). Theseresults were as predicted since the potential reproductive rateof males increases faster with temperature than does the potentialreproductive rate of females. Thus, an environmental factor,water temperature, affects not only the reproductive rates ofthe sexes, but also the operational sex ratio and mating competition,and thereby the intensity of sexual selection. Operational sexratio was not found to be correlated with male behavior. Thismay suggest a direct effect of temperature or potential reproductiverates on mate competition. The mechanism behind the evolutionof such a direct relationship would, however, probably be theimpact of potential reproductive rates on operational sex ratio,which in turn direcdy affects sexual selection.