Sucking Behavior Research Articles

The Association between Sucking Behavior in Preterm Infants and Neurodevelopmental Outcomes at 2 Years of Age

To evaluate whether a specific period after birth (in weeks postmenstrual age [PMA]) and specific elements of sucking are associated with abnormal neurodevelopmental outcomes at age 2 years using a longitudinal approach. Fifty-two preterm infants participated in this longitudinal cohort study (mean gestational age, 29.5 weeks; mean birth weight, 1197 g). We assessed the infants' sucking patterns at 37-50 weeks PMA using the Neonatal Oral-Motor Assessment Scale. At age 2 years, based on a neurologic examination and the Dutch version of the Bayley Scales of Infant and Toddler Development, Second Edition, we categorized the children as developing normally (n = 39) or abnormally (n = 13). ORs, including 95% CIs, were calculated to ascertain the risk of abnormal neurodevelopmental outcomes. The inability to sustain sucking at 46 weeks PMA (OR, 6.25; 95% CI, 1.29-30.35) and the absence of a mature sucking pattern at 44 weeks PMA (OR, 6.30; 95% CI, 1.40-28.32) significantly increased the odds of abnormal neurodevelopmental outcomes at age 2 years. The ORs of the Neonatal Oral-Motor Assessment Scale items assessing rhythmic jaw movements, rhythmic tongue movements, and coordination among sucking, swallowing, and respiration were high shortly after term, but failed to reach significance. Specific elements of sucking at 4-6 weeks postterm are associated with abnormal neurodevelopmental outcomes in preterm infants at age 2 years. This period might be a sensitive time of infant development in which sucking behavior is an early marker of abnormal developmental outcomes. This finding may offer opportunities for early intervention.

An automatized system for the assessment of nutritive sucking behavior in infants: a preliminary analysis on term neonates.

Nutritive Sucking (NS) is a highly organized process that can reflect infants' maturation during the early post-natal period. The assessment of NS may provide a sensitive means of evaluating early motor skills and their development. Thus, a reliable tool for assessing sucking behavior may benefit diagnostics and treatment of newborns since the first days of life. The aim of this work is to propose an automatized system to measure sucking ability and calculate a set of objective and quantitative indices for its assessment. We focused on the analysis of the Intraoral Pressure (IP) generated by infants while feeding: an ad-hoc designed software application was developed to analyze the signal obtained by a pressure transducer connected with a catheter placed through a standard bottle teat into the oral cavity during feeding. Automatic algorithms for suck and burst identification and for their characterization are described. We carried out a preliminary test of the system, analyzing data from two healthy term newborns, tested twice over time (1-2 days old and 6-10 weeks later). We calculated a set of different sucking parameters (e.g. sucking amplitude, frequency and area), and proposed some indices, that are typically used for the assessment of motor control, in order to assess the smoothness of IP. Results encourage further investigation of the proposed system for monitoring the development of early sucking skills.

Technological Solutions and Main Indices for the Assessment of Newborns’ Nutritive Sucking: A Review

Nutritive Sucking (NS) is a highly organized process that is essential for infants' feeding during the first six months of their life. It requires the complex coordination of sucking, swallowing and breathing. The infant's inability to perform a safe and successful oral feeding can be an early detector of immaturity of the Central Nervous System (CNS). Even though the importance of early sucking measures has been confirmed over the years, the need for standardized instrumental assessment tools still exists. Clinicians would benefit from specifically designed devices to assess oral feeding ability in their routine clinical monitoring and decision-making process. This work is a review of the main instrumental solutions developed to assess an infant's NS behavior, with a detailed survey of the main quantities and indices measured and/or estimated to characterize sucking behavior skills and their development. The adopted sensing measuring systems will be described, and their main advantages and weaknesses will be discussed, taking into account their application to clinical practice, or to at-home monitoring as post-discharge assessment tools. Finally, the study will highlight the most suitable sensing solutions and give some prompts for further research.

Abnormal sucking behavior in infants as a predictor of developmental delay at 18-month or 3-year of age

Abnormal sucking behavior in infants as a predictor of developmental delay at 18-month or 3-year of age

Ecological Sucking Monitoring of Newborns

Feeding by sucking is one of the first activities of daily life performed by infants. Sucking plays a fundamental role in neurological development and may be considered a good early predictor of neuromotor development. In this paper, a new method for ecological assessment of infants' nutritive sucking behavior is presented and experimentally validated. Preliminary data on healthy newborn subjects are first acquired to define the main technical specifications of a novel instrumented device. This device is designed to be easily integrated in a commercially available feeding bottle, allowing clinical method development for screening large numbers of subjects. The new approach proposed allows: 1) accurate measurement of intra-oral pressure for neuromotor control analysis and 2) estimation of milk volume delivered to the mouth within variation between estimated and reference volumes.

Oral Sessions

Background: Approximately 10% of children have maintained a digit sucking habit which is associated with anterior open bite and other malocclusions. Effects and costs of appliances developed to correct the oral habit and the consequent malocclusions remain controversial. Aim: To conduct a case-control study of digit sucking behaviour in a sample of 4-to-12-year-olds in Australia, with a special interest in the effect of orofacial myology management on cessation of the oral habit and correction of the consequent anterior open bite. Design: With appropriate ethics approval, patient records from a local clinic were de-identified and screened. Children having displayed digit sucking behaviour and anterior open bite were included. A 3-month management programme containing daily placement of a stomahesive wafer on the incisive papilla, behaviour shaping, reward charts and supportive phone calls was carried out. Data collected included age, gender, digit sucking behaviour and anterior open bite. A paired-samples t-test was used to examine occurrence of digit sucking behaviour and anterior open bite over the 3-month course. Results: Twenty-one (67.7%) girls and 10 (32.3%) boys completed the programme. There was no difference in age distribution between girls and boys (t = 1.434, df = 29, P = 0.162). Upon completion, twenty-six out of 31 children (83.9%) gave up digit sucking behaviour (t = 12.490, df = 30, P < 0.001). Occurrence of anterior open bite reduced from 19 patients (61.3%) to five patients (16.1%) (t = 4.971, df = 30, P < 0.001). Conclusion: The 3-month programme of orofacial myology management is effective in cessation of digit sucking behaviour and correction of digit-sucking-related anterior open bite. Future investigation is indicated.

The Effects of Music Therapy on Vital Signs, Feeding, and Sleep in Premature Infants

Recorded music risks overstimulation in NICUs. The live elements of music such as rhythm, breath, and parent-preferred lullabies may affect physiologic function (eg, heart and respiratory rates, O2 saturation levels, and activity levels) and developmental function (eg, sleep, feeding behavior, and weight gain) in premature infants. A randomized clinical multisite trial of 272 premature infants aged ≥32 weeks with respiratory distress syndrome, clinical sepsis, and/or SGA (small for gestational age) served as their own controls in 11 NICUs. Infants received 3 interventions per week within a 2-week period, when data of physiologic and developmental domains were collected before, during, and after the interventions or no interventions and daily during a 2-week period. Three live music interventions showed changes in heart rate interactive with time. Lower heart rates occurred during the lullaby (P < .001) and rhythm intervention (P = .04). Sucking behavior showed differences with rhythm sound interventions (P = .03). Entrained breath sounds rendered lower heart rates after the intervention (P = .04) and differences in sleep patterns (P < .001). Caloric intake (P = .01) and sucking behavior (P = .02) were higher with parent-preferred lullabies. Music decreased parental stress perception (P < .001). The informed, intentional therapeutic use of live sound and parent-preferred lullabies applied by a certified music therapist can influence cardiac and respiratory function. Entrained with a premature infant's observed vital signs, sound and lullaby may improve feeding behaviors and sucking patterns and may increase prolonged periods of quiet-alert states. Parent-preferred lullabies, sung live, can enhance bonding, thus decreasing the stress parents associate with premature infant care.

Association between Feeding Methods and Sucking Habits: A Cross-sectional Study of Infants in Their First 18 Months of Life

The aim of this study is to investigate infant feeding patterns and to analyze the influence of breast-feeding methods on the prevalence of non-nutritive sucking habits in a sample of Japanese infants. A random sample of 353 mothers of infants of 18 months of age was interviewed at a public health facility in "K" city. The prevalence and duration of infant feeding patterns categorized as breast-feeding, partial breast-feeding, and bottle-feeding, were determined. The outcome investigated was the prevalence of non-nutritive sucking habits (pacifier use and finger sucking). The data were analyzed using the Chi-square and Fisher's exact tests with Bonferroni correction for multiple comparisons to assess possible association between feeding method and non-nutritive sucking behavior. The infants were categorized into the following groups depending on feeding method: breast-feeding (27.2%), partial breast-feeding (32.0%), or bottle-feeding (40.8%). Among all infants, 13.9% used a pacifier, 18.4% sucked their fingers, and 0.3% had both habits at 18 months of age. Breast-feeding was negatively correlated with pacifier use and finger sucking. In contrast, bottle-feeding was strongly associated with pacifier use and finger sucking. These results suggest that breast-feeding provides benefits to infants, and that non-nutritive sucking habits may be avoided by promoting correct breast-feeding practices.

Pheromone-induced odor learning modifies Fos expression in the newborn rabbit brain

Associative learning contributes crucially to adjust the behavior of neonates to the permanently changing environment. In the European rabbit, the mammary pheromone (MP) excreted in milk triggers sucking behavior in newborns, and additionally promotes very rapid learning of initially neutral odor cues. Such stimuli become then as active as the MP itself to elicit the orocephalic motor responses involved in suckling. In this context, the rabbit is an interesting model to address the question of brain circuits early engaged by learning and memory. Here, we evaluated the brain activation (olfactory bulb and central regions) induced in 4-day-old pups by an odorant (ethyl acetoacetate, EAA) after single pairing with the MP and its subsequent acquired ability to elicit sucking-related behavior (conditioned group) or after mere exposure to EAA alone (unconditioned group). The brain-wide mapping of c-Fos expression was used to compare neural activation patterns in both groups. Evidence of high immunostaining to odorant EAA occurred in the mitral+granule cells layer of the main olfactory bulb in pups previously exposed to EAA in association with the MP. These pups also showed higher expression of Fos in the piriform cortex, the hypothalamic lateral preoptic area and the amygdala (cortical and basal nuclei). Thus, MP-induced odor learning induces rapid brain modifications in rabbit neonates. The cerebral framework supporting the acquisition appears however different compared to the circuit involved in the processing of the MP itself.

What Do We Know About Repetitive Sucking, Biting, Pulling, and Picking Behaviors?

What Do We Know About Repetitive Sucking, Biting, Pulling, and Picking Behaviors?

A Comparison of Early Sucking Dynamics During Breastfeeding After Cesarean Section and Vaginal Birth

The impact of cesarean section (CS) birth and pethidine for post-CS epidural analgesia on early breastfeeding behavior is unclear. This study aimed to measure infant sucking and breastfeeding behavior in infants of mothers who delivered by CS (CS group) and used pethidine patient-controlled epidural analgesia (PCEA) after CS with that of infants who were delivered by vaginal birth (V group), during secretory activation and again after the establishment of lactation. Sucking dynamics and milk intake of breastfeeding infants were assessed on approximately 3 and 20 (follow-up) days postpartum (CS group, n=19; V group, n=15). Nipple diameters, tongue movement, and nipple position during sucking were measured from ultrasound scans of the intra-oral cavity during breastfeeding. Time of the first breastfeed and day of breast fullness were recorded, and infant neurobehavior was assessed. CS infants displayed more anterior tongue movement on Day 3 than at follow-up compared with the V group, which showed a similar amount of movement at each assessment (p for interaction<0.001). Compared with the V group, the CS group showed faster suck rates, especially on Day 3 (p<0.001), later times to first breastfeed (p=0.01) and breast fullness (p=0.03), and lower neurobehavioral scores (p=0.047). Breastfeeding duration and milk intake were similar between groups. Although the observed effect of CS birth followed by pethidine PCEA after CS during the period of secretory activation was small, our results indicate that successful initiation of lactation may require additional breastfeeding support and monitoring at Day 3 postpartum for mothers who undergo CS.

Pre-orbital gland opening: Part of sucking behavior in red deer (Cervus elaphus) calves1

Opening of the pre-orbital gland in red deer (Cervus elaphus) was previously found to be associated with feeding and negatively associated with achieving satiety in bottle-reared red deer calves. We speculated that this acted as a signal from a calf to the mother that it was hungry. Thus, we focused on a possible association between the pre-orbital gland opening and the sucking behavior in red deer calves. We recorded 63 sucking attempts and 150 sucking bouts within a stable social group of 24 farmed red deer females with 19 calves ages 16 to 90 d. The probability of the pre-orbital gland opening or remaining open during a sucking bout rapidly decreased with the on-going sucking phase (P < 0.001), and it was less after than during a sucking attempt (P < 0.03). The proportion of open pre-orbital glands at the end of sucking depended on whether the nursing female (27.85%) or the calf (0%, P < 0.01) terminated the sucking bout. The open pre-orbital gland of the calf after the sucking bout significantly predicted a subsequent sucking attempt (P < 0.001). The probability of open pre-orbital gland was not significantly affected by the age of the calf, sex or birth weight, or age of the nursing female. In conclusion, our study provides evidence that the opening of the pre-orbital gland is one of the general patterns of calf sucking behavior, specifically that it reflects the level of satisfying calf needs.

Comparison of early sucking dynamics of breastfeeding infants born by either caesarean section and vaginal birth

This study compared infant sucking and breastfeeding behaviour in infants of mothers who delivered by caesarean section (CS) and received pethidine for post‐caesarean section analgesia, with mothers who delivered vaginally (V), during the period of secretory activation (day 3) and again after the establishment of lactation (follow‐up). Infant sucking was measured with ultrasound images of the infant's intra‐oral cavity, breastfeeding behaviour was assessed by the LATCH‐R tool and the times to first breastfeed and breast fullness were recorded. CS infants displayed significantly more anterior tongue movement on day 3 than at follow‐up (p&lt;0.001), whereas the V group showed a similar amount of movement between assessments. Compared to the V group, in the CS group LATCH‐R scores improved at follow‐up (CS; p=0.02, V: p=0.15), CS suck rates were faster, especially on day 3 (p&lt;0.001), and times to first breastfeed (p=0.01) and breast fullness (p=0.03) were significantly later. These results suggest a small influence of CS birth and/or pethidine on breastfeeding during the critical period of secretory activation. Funding: Medela AG, Switzerland.

Evolution and Development of Dual Ingestion Systems in Mammals: Notes on a New Thesis and Its Clinical Implications

Traditionally, the development of oral feeding is viewed as a continuous, unitary process in which reflex-dominated sucking behavior gives rise to a more varied and volitional feeding behavior. In contrast, we consider the thesis that the infant develops two separable ingestive systems, one for suckling and one for feeding. First, we apply an evolutionary perspective, recognizing that suckling-feeding is a universal, mammalian developmental sequence. We find that in mammalian evolution, feeding systems in offspring were established prior to the evolution of lactation, and therefore suckling is a separable feature that was added to feeding. We next review an experimental literature that characterizes suckling and feeding as separable in terms of their topography, sensory controls, physiological controls, neural substrates, and experience-based development. Together, these considerations constitute a view of “dual ingestive systems.” The thesis, then, is that suckling is not a simple precursor of feeding but is a complete behavior that emerges, forms, and then undergoes a dissolution that overlaps with the emergence of independent feeding. This thesis guides us to focus differently on the challenges of properly managing and facilitating oral ingestion in infants, especially those born preterm, prior to the developmental onset of suckling.

P1-499 Prevalence and associated factors of anterior open bite in children aged 2–5 years-old

IntroductionThe anterior open bite is the malocclusion with major aesthetic and functional commitments, besides it has a more complex treatment. In order to prevent its occurrence, it's fundamental to know...

Bottle feeding, increased overjet and Class 2 primary canine relationship: is there any association?

The aim of this study was to investigate the association between bottle feeding and prevalence rates of increased overjet and Class 2 primary canine relationship. The sample consisted of 911 children (461 boys, 450 girls) aged 3 (13.9%), 4 (40.8%), 5 (34%) and 6 (11.3%) years, with complete primary dentition. Information about nutritive and nonnutritive (pacifier and/or digit) sucking habits was collected through questionnaires. Three calibrated dentists (κ: 0.9-1.0 and Rs > 0.90) performed the clinical assessments. The children were divided into four groups: G1 - not bottle-fed; G2 - exclusively bottle-fed; G3 - breast- and bottle-fed, bottle feeding ceased before 3 years of age; and G4 - breast- and bottle-fed, bottle feeding ceased between 3 and 4 years of age. Associations between nutritive and nonnutritive sucking behaviors and the malocclusions studied were analyzed by multiple binary logistic regression (α= 0.05). The frequencies of increased overjet were: 25.3% (G1), 38.8% (G2), 39.2% (G3) and 47.8% (G4). The percentages of Class 2 canine relationship were: 27.9% (G1), 48.8% (G2), 43.4% (G3) and 43% (G4). No significant effect of bottle feeding was found. The chances of diagnosing increased overjet (O.R. = 4.42, p < 0.001) and Class 2 canine relationship (O.R. = 4.02, p < 0.001) were greater for children with pacifier and/or digit-sucking habits, compared to those without a history of nonnutritive sucking behavior. It may be suggested that bottle feeding alone is not directly associated with higher prevalence rates of increased overjet and Class 2 canine relationship in the primary dentition.

Cochrane Review: Non‐nutritive sucking for promoting physiologic stability and nutrition in preterm infants

AbstractBackgroundNon‐nutritive sucking is used during gavage feeding and in the transition from gavage to breast/bottle feeding in preterm infants to promote the development of sucking behaviour and improve digestion of enteral feedings.ObjectivesTo determine whether non‐nutritive sucking (NNS) in preterm infants influences: a) weight gain, b) energy intake, c) heart rate, d) oxygen saturation, e) length of hospital stay, f) intestinal transit time, g) age at full oral feeds, or h) any other clinically relevant outcomes.Search strategyMEDLINE and CINAHL databases back to 1976 and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2005) were searched. Updated search in March 2010 included MEDLINE (search via PubMed), CINAHL, EMBASE and CENTRAL (The Cochrane Library).Selection criteriaAll trials utilizing experimental or quasi‐experimental designs in which non‐nutritive sucking in preterm infants was compared to no provision of non‐nutritive sucking were eligible for the review.Data collection and analysisData were extracted independently by the two authors. No subgroup analyses were performed because of the small number of studies related to the relevant outcomes.Main resultsThis review consisted of 21 studies, 15 of which were randomized controlled trials. NNS was found to decrease significantly the length of hospital stay in preterm infants. The review did not reveal a consistent benefit of NNS with respect to other major clinical variables (weight gain, energy intake, heart rate, oxygen saturation, intestinal transit time, age at full oral feeds and behavioral state). The review identified other positive clinical outcomes of NNS: transition from tube to bottle feeds and better bottle feeding performance. No negative outcomes were reported in any of the studies.Authors' conclusionsThis review found a significant decrease in length of stay in preterm infants receiving a NNS intervention. The review did not reveal a consistent benefit of NNS with respect to other major clinical variables (weight gain, energy intake, heart rate, oxygen saturation, intestinal transit time, age at full oral feeds and behavioral state).The review identified other positive clinical outcomes of NNS: transition from tube to bottle feeds and better bottle feeding performance. No negative outcomes were reported in any of the studies. There were also a number of limitations of the presently available evidence related to the design of the studies, outcome variability, and lack of long‐term data. Based on the available evidence, NNS in preterm infants would appear to have some clinical benefit. It does not appear to have any short‐term negative effects.Plain Language SummaryNon‐nutritive sucking for promoting physiologic stability and nutrition in preterm infantsAn infant born prematurely may be fed through a tube into the stomach, so is often given a pacifier to suck on to improve nutrition. An infant needs coordinated sucking, swallowing and breathing to feed. The ability to suck and to swallow is present by 28 weeks gestation, but infants are not fully coordinated until 32 to 34 weeks. This means that preterm infants less than 32 weeks gestation are usually not able to feed effectively from the breast or a bottle. They are fed by a small tube that is placed up the nose into the stomach (gavage feeding). Sucking on a pacifier (non‐nutritive sucking) during gavage feeding may encourage the development of sucking behaviour and improve digestion of the feeding. Non‐nutritive sucking may also have a calming effect on infants, although it does have the potential to interfere with breastfeeding. The authors searched the medical literature and found 21 studies, 15 were randomized controlled trials and six were non‐randomized. The total number of infants in each study ranged from 10 to 59. Weight gain was similar with and without use of a pacifier. Preterm infants with pacifiers did not stay in hospital as long as those without and hospital costs were less (two studies). These infants showed less defensive behaviors during tube feedings, spent less time in fussy and active states during and after tube feedings, and settled more quickly into sleep. Their transition to full enteral (by tube or mouth) or bottle feeds (three studies) and bottle feeding performance, in general, (one study) were easier. No negative outcomes were reported.

Malocclusions and non-nutritive sucking habits: a preliminary study

Objective This study investigated the non-nutritive sucking habits in a sample of patients with malocclusions at the Unit of Pediatric Dentistry of the “Sapienza”, University of Rome. Materials and methods 81 children (average age 5.9 years) were examined from January to December 2008. All children showed typical malocclusions that could be associated with non-nutritive sucking habits (pacifier or finger). Increased overjet (OVJ), anterior openbite (OPB), and posterior crossbite (CRB) were recorded in this survey. A questionnaire was directed to parents. Results At the first examination 40.4% of pacifier users over 24 months were affected by an anterior OPB, 50% by a posterior CRB and 39.4% by an increased OVJ. Moreover, 40.4% of the children with finger or thumb sucking behavior were affected by an anterior OPB, 29.2% by a posterior CRB, and 42.4% by an increased OVJ. Conclusions No statistically significant associations could be detected between the non-nutritive sucking habits and the malocclusions. There was no difference in type of habit in children who presented an anterior OPB, while there was a higher prevalence rate of children with a posterior CRB who had sucked the pacifier and of children with increased OVJ who had sucked their finger.

Breed differences in the expression of maternal care at parturition persist throughout the lactation period in sheep

Maternal care plays an important role in the survival of offspring in mammals. In the ewe initial maternal care is expressed by nurturing the young and formation of an exclusive olfactory bond with the lamb. After the neonatal period, maternal care is associated with co-operation with sucking interactions, maintenance of a close ewe–lamb relationship, communication with lambs, vigilance and a tendency to seek absent lambs. Two breeds of ewe, Suffolk and Scottish Blackface, have previously been shown to differ in their expression of early maternal care, and in lamb survival. It was hypothesised that these differences in the expression of maternal behaviour would persist throughout the lactation period and continue to be expressed in other aspects of maternal care. The maternal behaviour of 32 primiparous ewes (18 Suffolk, 14 Blackface) was observed from birth until weaning at 12 weeks of age. As shown previously, Blackface ewes spent more time grooming their lambs than Suffolk ewes ( P < 0.001), and were more cooperative with the early sucking behaviour of their offspring ( P < 0.01). Blackface ewes were significantly closer to their lambs from birth and throughout the lactation period ( P < 0.05). There were no significant differences between breeds in maternal vocal communication with their lambs, however, Blackface ewes were significantly more vigilant (head alert) than Suffolk ewes from week 4 of lactation onwards ( P < 0.01). The lambs of Suffolk ewes had a significantly higher frequency of sucking bouts ( P < 0.05) than lambs of Blackface ewes in the first weeks of lactation. However, Blackface ewes accepted a greater proportion of lamb sucking attempts than Suffolk ewes ( P < 0.01), and these sucking bouts were longer than with Suffolk ewes ( P < 0.05). The results therefore show that differences in the expression of maternal care seen in the initial post partum period in sheep persist throughout lactation, and would be expected to contribute to lamb survival.

Mating behavior and the evolution of sperm design.

Sperm are the most diverse of all animal cell types, and much of the diversity in sperm design is thought to reflect adaptations to the highly variable conditions under which sperm function and compete to achieve fertilization. Recent work has shown that these conditions often evolve rapidly as a consequence of multiple mating, suggesting a role for sexual selection and sexual conflict in the evolution of sperm design. However, very little of the striking diversity in sperm design is understood functionally, particularly in internally fertilizing organisms. We use phylogenetic comparative analyses covering 16 species of the hermaphroditic flatworm genus Macrostomum to show that a complex sperm design is associated with reciprocal mating and that this complexity is lost secondarily when hypodermic insemination--sperm injection through the epidermis--evolves. Specifically, the complex sperm design, which includes stiff lateral bristles, is likely a male persistence trait associated with sexual conflicts over the fate of received ejaculates and linked to female resistance traits, namely an intriguing postcopulatory sucking behavior and a thickened epithelium of the sperm-receiving organ. Our results suggest that the interactions between sperm donor, sperm, and sperm recipient can change drastically when hypodermic insemination evolves, involving convergent evolution of a needle-like copulatory organ, a simpler sperm design, and a simpler female genital morphology. Our study documents that a shift in the mating behavior may alter fundamentally the conditions under which sperm compete and thereby lead to a drastic change in sperm design.