Reproductive biology of the antipatharian black coral Antipathes fiordensis in Doubtful Sound, Fiordland, New Zealand

The reproductive biology of Antipathes fiordensis Grange, a species endemic to south-western New Zealand, was followed from April 1994 to May 1995. Ten colonies were individually tagged in Doubtful Sound and sampled on a monthly basis in order to determine their reproductive activity. The fecundity of each of the five tagged female colonies was determined by estimating the total number of polyps per colony from photographs of each colony and by planimetry, the proportion of gravid polyps per colony, and the mean number of oocytes per gravid polyp. In addition, 56 colonies were sampled in March 1995 to estimate the sex ratio, height at sexual maturity, and mean sizes of females and males. A. fiordensis was found to be a dioecious species which, in the absence of gonads in the polyps, has no obvious external morphological differences between the sexes. Broadcast spawning of gametes is the likely mode of reproduction. Gametogenesis began in November 1994 and was highly synchronous within and between colonies, with spawning occurring in March 1995. The sex ratio in adults was 1:1. Colonies reached sexual maturity between the heights of 70 and 105 cm which, based on existing estimates of growth rate, corresponds to a minimum age for sexual maturity of about 31 yr. The largest oocytes measured ranged from 100 to 140 μm in size. Female colonies produced between 1.3 and 16.9 million oocytes, with the larger colonies dominating the reproductive output of the population. Received: 23 June 1997 / Accepted: 1 August 1997     

Reproductive biology of the holothurians from the major communities of the New Caledonian Lagoon

The reproductive biology of nine species of aspidochirote holothurians from the major communities of the New Caledonian lagoon has been analysed. The data were obtained from monthly sampling from 1978 to 1982 of their populations on reef slopes and passes for Holothuria nobilis, H. fuscogilva, H. fuscopunctata and Thelenota ananas, in the inner lagoon for Stichopus variegatus, H. scabra and H. scabra versicolor and on reef flats for Actinopyga mauritiana, A. echinites and H. atra. The morphology and anatomy of the gonads and their annual cycle are described. The reproductive cycles, composed of the five phases of gonad growth, maturing, spawning, post-spawning and resting, were determined from the changes in the sexual stages, the gonad indices and the percentage of indeterminate sex. Three main reproductive patterns are recognized, annual cycles with spawning occurring during the warm season or during the cool season and a semiannual cycle. Other population parameters, such as the size of the mature oocytes, the mean size of the individuals at first sexual maturity, and absolute and relative fecundities were calculated and related to the mean size of the species, the taxonomy and the ecology. The reproductive strategies of the species show a gradient that is probably related to the stability of the biotopes, with smaller species living in the more intrable outer reef flats and larger species in deeper lagoon floors.     

Functional morphology of the gonads of the articulate brachiopodTerebratulina retusa

The reproductive anatomy, and ultrastructural features of the gonads of the articulate brachiopodTerebratulina retusa (Linnaeus), are documented based on collections made between October 1985 and October 1986 from the Firth of Lorn, west coast of Scotland. This species is dioecious, and maturity is achieved in both sexes at shell lengths greater than ~5.5 mm. There is no obvious external sexual dimorphism except for slight differences in the coloration of the gonads; testes are white/cream, ovaries are yellow/orange. The gonads occur as four palmate lobes, a pair in each valve. Gonads are formed within a mantle sinus (vascula genitalia), which is an anterior extension of the coelom, that opens posteriorly into the visceral cavity and to the exterior via a pair of metanephridia. The latter serve as gonoducts during spawning. Gametes are borne on genital lamellae formed from a reticulate lattice of connective tissue. The lamellae are an extension of the ileoparietal band and are fused along one margin to the inner mantle membrane. Developing oocytes are closely affixed to the genital lamellae and originate from a pool of proliferating germ cells at its base. Vitellogenic oocytes that are at an advanced stage are released from the genital lamellae, but are retained within thevascula genitalia. Liberated oocytes continue to accumulate yolk and eventually occlude thevascula genitalia, before being spawned. Coelomocytes were identified within the gonads. In spent females these cells appear to be phagocytic and involved in the resorption of necrotic material, while in the male they may serve as nutritive cells.     

Reproductive biology of <Emphasis Type="Italic">Cosmasterias lurida</Emphasis> (Echinodermata: Asteroidea) an anthropogenically influenced substratum from Golfo Nuevo,Northern Patagonia (Argentina)

The starfish Cosmasterias lurida was sampled from the pier piles of Almirante Storni in the Golfo Nuevo, northern Patagonia, from November 2001 to November 2003. In this anthropogenically modified site there is an unusually abundant food supply of mussels and large aggregations of starfishes. The reproductive cycle was studied by organ indices and histological examination of gonads. The highest gonad index (GI) values were found in the summer (February–March), followed by a drop in GI values, indicating spawning. Histological analyses indicated that gametogenesis takes place from June to January, sexual maturity occurred during the summer and spawning occurred in April. The GI and pyloric caeca index (PCI) tended to have an inverse relationship, but this was only statistically significant in males. However, biochemical analyses of the starfish indicated no transfer of nutrients between pyloric caeca and gonads in either sex. In fact, simultaneous accumulation of carbohydrates was found in the pyloric caeca and gonads of both sexes.     

Hepatic mixed-function oxidases in California flatfishes are increased in contaminated environments and by oil and PCB ingestion

Hepatic mixed-function oxidases (MFOs) were measured in the bothid flatfishes Citharicthys sordidus and C. stigmaeus from relatively uncontaminated and from polluted coastal populations of California, USA, at various times of the year during 1979–1980 and in individuals fed crude oil and polychlorinated biphenyl-augmented food in the laboratory. For C. sordidus, aryl hydrocarbon hydroxylase (AHH) specific activity was generally highest around the Los Angeles County sewage outfall on the Palos Verdes Shelf, intermediate near the 7-mile Hyperion sewage outfall in Santa Monica Bay and around a petroleum seep in the Santa Barbara Channel, and lowest in relatively unpolluted Monterey Bay. For C. stigmaeus, which had about ten times less specific activity than the foregoing species, specimens from the Santa Barbara petroleum seep had significantly greater AHH specific activity than those from Monterey Bay. Fishes from contaminated environments also showed increases of microsomal proteins with molecular weights of 56, 54, 57 and 46×10³; moreover, the content of cytochrome P-450 was elevated in specimens of C. sordidus from such environments. Augmentation of food with seep oil or polychlorinated biphenyls (PCBs) induced significant increases in the specific activity of AHH and amounts of microsomal proteins in C. stigmaeus. Thus, these two species of flatfishes are good candidates for monitoring biologically meaningful levels of petroleum and polychlorinated biphenyls in contaminated environments. Moreover, the mixed function oxidase pattern in fish populations from the Santa Barbara petroleum seep is evidently a functional adaptation to chronic intake of petroleum hydrocarbons.     

Direct sampling and in situ observation of a persistent copepod aggregation in the mesopelagic zone of the Santa Barbara Basin

Observations from a one-person submersible (Wasp) in fall, 1982, revealed a persistent aggregation of non-migrating, Stage V copepodites of Calanus pacificus californicus Brodsky in a band 20±3 m thick at a depth of 450 m, about 100 m above the bottom of the Santa Barbara Basin, California. Copepod abundances, calculated from nearest-neighbor distances measured directly from the submersible, yielded maximum densities of 26×10⁶ copepodites m^-3. Quiescent behavior, low laminarinase activity, low protein content, high lipid content and evidence of low excretion rate all suggest that these copepodites were in a state of diapause. Diapausing C. pacificus californicus at other locations along the eastern Pacific coast were also captured in discrete depth plankton tows. Both the submersible observations and the net collections suggest that the dense aggregation of diapausing copepods we observed in the Santa Barbara Basin was a phenomenon associated with seasonal upwelling cycles, and that such aggregations occur during non-upwelling periods when food is scarce in surface waters. Numerous predators, especially the deep sea smelt Leuroglossus stilbius, were observed feeding upon the aggregated copepods; thus, in contrast to the conventional picture of surface-dominated food distribution, deep-water aggregations of C. pacificus californicus may support the mesopelagic community during periods of low food availability in surface waters.     

Histochemical studies on reproductive and nutritional cycles of the holothurian,Holothuria scabra

Histochemical observations were made of seasonal changes of protein, carbohydrates, lipids and nucleic acids in different tissues of Holothuria scabra. Accumulation of organic components in the gonads were observed with the advance of maturity. Protein and lipids were found to be important as storage materials for utilization during development. A sexcorrelated variation of nucleic acids was evident in the gonads. Intestinal protein and lipids were found to be utilized by the gonads during the reproductive cycle; carbohydrates seemed to be of lesser importance.     

Reproduction in five species of crinoids at Lizard Island,Great Barrier Reef

Reproduction in five species of crinoids [Himerometra bartschi (A. H. Clark), H. robustipinna (P. H. Carpenter), Cenometra bella (Hartlaub), Colobometra perspinosa (P. H. Carpenter), and Oligometra serripinna (P. H. Carpenter)] was studied at Lizard Island, Queensland, over 24 mo, from April 1981 to March 1983 (except for O. serripinna —June 1981 to March 1983). All five species of crinoids were dioecious, although a few instances of synchronous hermaphroditism were noted in H. bartschi, C. perspinosa, and O. serripinna. Gonad morphology and the sequence of developmental stages were similar in each species. Within individuals, gametogenesis was synchronous in gonads both along and between arms, except in some proximal and distal genital pinnules in which gonads never matured. Within a species, there was a degree of synchrony of gametogenesis in a sample, but the level of gametogenic activity varied considerably between years. A high level of continuous reproductive activity was observed in H. bartschi, H. robustipinna, Cenometra bella, and Colobometra perspinosa from about mid-summer to early/mid-winter, while O. serripinna probably had a bimodal reproductive cycle with peaks around February and June. There was a significant 1:1 male:female sex ratio in the populations sampled, and unsexable individuals were significantly smaller (as determined by maximum arm length) than either sexable males or females.     

Larval reproduction in the ctenophore Mnemiopsis mccradyi (order Lobata)

Dissogony was observed in normal and experimentally manipulated individuals of Mnemiopsis mccradyi in February–April, 1985. The normal oral-aboral length at which sexual reproduction begins in M. mccradyi is 30±5 mm; however, some larvae, of 1.5 to 2.8 mm (oralaboral length), produce viable gametes. During the present study, not all individuals from a particular spawning which were kept in the same conditions became reproductive at an early age. The age at which larval reproduction began varied between individuals. The length of time over which individuals spawned varied considerably — some spawned only once, while others spawned repeatedly. Only the gonads located under the adesophageal ctene rows (and not those associated with the adtentacular rows) produced gametes during the early reproductive period. After larvae stopped spawning, the gonads regressed and the larvae grew to large lobate stages. Individuals which became sexually reproductive as larvae also became sexually reproductive during lobate stages.     

Reproductive biology and ecology of a deep-demersal fish, alfonsino Beryx splendens, over the seamounts off New Caledonia

The reproductive biology of the alfonsino Beryx splendens was studied by histological examinations, gonadosomatic index and macroscopic scales of maturation of a large sample of gonads. Alfonsino is a gonochoric species. The size-frequency distribution of the sex ratio was bimodal and considered to be due to size dimorphism. In New Caledonia, the breeding period of this species occurs during the southern summer, with a peak in December to January. The spawning stage is attained at a minimum fork length of 28 cm for females and 33 cm for males. The size at which 50% of the population attain sexual maturity (FL₅₀) is 33.2 cm for females and 34.5 cm for males. Maximum potential fecundity is estimated to lie between 270 000 to 675 000 eggs for fish between 34 and 40 cm in fork length. It was possible to differentiate vegetative zones, in which juvenile alfonsino grow until they reach maturity, from reproductive zones (fishing grounds) which are inhabited by mature individuals. The larvae and juveniles could be carried from the reproductive zone to the vegetative zone by currents in an oceanic eddy system. Received: 26 April 1996 / Accepted: 20 September 1996     

Gonadal development in the coral reef damselfish<Emphasis Type="Italic"> Dascyllus flavicaudus</Emphasis> from Moorea,French Polynesia

The present study investigated the sexual pattern of the yellow-tailed dascyllus, Dascyllus flavicaudus (Randall and Allen), through histological examination of the process of gonadal differentiation and maturation and through male-removal experiments in the laboratory. The study was conducted in Moorea, French Polynesia (17°32S; 149°50W), from 31 December 1994 to 11 March 1995. For gonadal histology, two populations were sampled, one consisting of large aggregations (n=54) and the other consisting of small- to medium-sized groups around isolated corals (n=55). An additional small sample (n=21) was also collected from a population that consisted of small groups around isolated corals. After an initially undifferentiated state, gonads of D. flavicaudus developed an ovarian lumen, followed by oocytes in the primary growth stage. From this ovarian state or from more developed ovaries with cortical-alveolus stage oocytes, some gonads developed into testes through degeneration of oocytes and development of spermatogenic tissue. In all three populations, spermatogenic tissue developed only in gonads that contained pre-vitellogenic oocytes (termed as mixed stage 1–2 gonads). The two main populations did not differ in their expression of sex change despite differences in their social organization. In both populations, size of individuals with mixed stage 1–2 gonads overlapped mainly with the size range of immature females, which suggests that functional female-to-male sex change was rare. The hypothesis that D. flavicaudus is primarily gonochoristic is further supported by removal experiments in laboratory groups, in which removal of a dominant male(s) failed to induce sex change in any of the high-ranking females. Yet, in all three field populations, some fish with mixed stage 1–2 gonads were found within the size ranges of mature females, which indicates possible occurrences of functional sex change. These conflicting results indicate that it may be premature to draw any definitive conclusions about the sexual pattern of D. flavicaudus.Communicated by T. Ikeda, Hakodate     

Some biological interactions affecting intertidal populations of the kelp Egregia laevigata

Near Santa Barbara, California (USA), the large laminarian kelp Egregia laevigata (Setchell) occurred from the lower intertidal zone to subtidal depths. In the intertidal zone there was a large recruitment of E. laevigata in the spring. The kelp were largely excluded from a zone in the lowest intertidal zone where the surf grass Phyllospadix sp, grew, but were abundant on all other rock surfaces. Experiments demonstrated that, while neither grazers nor sessile organisms significantly reduced recruitment, E. laevigata of the previous year-class did so. There were also interactions among E. laevigata of the same year-class, expressed as a density-dependent mortality of very small algae, and as faster growth rates and greater number of branches of kelp at low densities. These processes tended to make both numbers and biomass of E. laevigata uniform. The mortality rates of large E. laevigata were so high that, in some locations, no kelp survived for more than 8 months. E. laevigata was, therefore, essentially an annual and opportunistic species in the intertidal zone.     

Oxygen consumption of pelagic juveniles and demersal adults of the deep-sea fish Sebastolobus altivelis,measured at depth

Oxygen consumption rates of the deep-sea fish Sebastolobus altivelis were measured in situ on pelagic juveniles at mesopelagic depths (608 m) and on demersal adults at bathyal depths (1 300 m) in the Santa Catalina Basin in March 1982. Two pelagic juveniles were individually collected, and respiration was measured continuously for approximately 2 d with a slurp gun respirometer manipulated from the submersible “Alvin”. Oxygen consumption rates of these juveniles were highly variable and were 1.5 to 1.8 times higher during the night than during the day. Gut contents of the juveniles were mainly euphausiids (Euphausia pacifica and Nematoscelis difficilis). Four demersal adults were collected by “Alvin” and individually placed in fish-trap respirometers on the bottom where respiration was measured continuously for approximately 1 d. Weight-specific O₂ consumption rates for adults decreased with increasing body weight and were consistent in magnitude throughout the incubation period. Population O₂ consumption for demersal S. altivelis (calculated from abundance, size-frequency distribution, and O₂ consumption regression equation) was 11.01 μl O₂ m^-2 h^-1, which is two orders of magnitude less than the O₂ consumption rate for the population of the most abundant epibenthic megafaunal species in the Santa Catalina Basin, the ophiuroid Ophiophthalmus normani. O. normani is a principal prey for adults of S. altivelis based on gutcontent analysis. Given the population O₂ consumption rate as an estimate of food energy demand, the demersal population of S. altivelis would assimilate only 0.007% of the standing crop of O. normani per day.     

Changes in gonadal development,androgenic gland cell structure,and hemolymph vitellogenin levels during male phase and sex change in laboratory-maintained protandric shrimp, <Emphasis Type="Italic">Pandalus hypsinotus</Emphasis> (Crustacea: Caridea: Pandalidae)

Most pandalid shrimps show protandric hermaphroditism, and male sexual differentiation is considered to be controlled by the androgenic gland. In the present study, we examined the histology of gonadal development during the male phase and sex change and the involvement of the androgenic gland in regulating male reproduction in laboratory-maintained Pandalus hypsinotus. Juvenile shrimps developed testicular tissues in the peripheral part of gonads during the age of 16–31 months and produced spermatozoa between 34 and 36 months. After reaching sexual maturity, male shrimps exhibited seasonal testicular development: active production of spermatozoa (February–May), disappearance of spermatozoa (spent, April–June), increase of spermatocytes (May–November), appearance of spermatids and spermatozoa in the gonads (November–February). The androgenic gland cells became larger and the rough endoplasmic reticulum in the cytoplasm developed at male sexual maturity. The cell structure shows that the androgenic gland hormone is a peptide. Furthermore, bilateral eyestalk ablation on immature male shrimps induced hypertrophy of the androgenic gland and acceleration of male sexual maturation. These results indicate the involvement of androgenic gland hormone and some eyestalk factor in regulating male sexual maturation. Over a 1-year laboratory-rearing period, some male shrimps (16.7%) changed sex. In transitional shrimps, testicular tissues in the gonads and androgenic glands degenerated; on the other hand, oocytes started yolk protein accumulation and hemolymph vitellogenin levels became high. These results suggest that androgenic gland degeneration is a trigger for sex change and that the vitellogenin level is a useful marker for sex change.     

Gonopore sexing technique allows determination of sex ratios and helper composition in eusocial shrimps

An evaluation of the social organization and sexual system of eusocial species of Synalpheus has been hindered because it has not been possible to determine the sexual composition of colony helpers (workers). The external sexual characters typically used to sex caridean shrimps are lacking in Synalpheus. We used SEM sexing technique to determine the sexual composition of helpers in colonies of Synalpheus regalis, S. rathbunae, S. chacei, S. rathbunae A (see Morrison et al. Mol Phylogen Evol 30:563–568, 2004), and S. filidigitus. Colonies consisted of both sexes and sex ratios of helpers generally conformed to 50:50 female to male. Females were characterized by gonopores with U-shaped slits on the coxae of the third pereopods (first walking legs) while males had oval gonopore openings on the coxae of the fifth pereopods (third or last walking legs). In S. chacei, S. filidigitus, and S. rathbunae A, a few helpers were found that had both male and female gonopores (intersexes). All three reproductive females (queens) of S. filidigitus examined were intersexes. Sexing of helpers allowed us to test some hypotheses about sexual differences in helper morphology that might indicate task specialization (division of labor). Male helpers were not different from female ones in body size (except in S. regalis: males somewhat larger) and in fighting chela size. The lack of sexual dimorphism in these characters suggests no male–female specialization in colony tasks such as defense. The presence of male and female helpers similar in size suggests that the sexual system of these eusocial species is gonochoristic, although protandry of some sort in S. filidigitus can not be ruled out. The intersexuality observed in a few individuals may be due to developmental anomalies, protandry, or even simultaneous hermaphroditism. Finally, the sexing technique allowed us to establish that new colonizers of unoccupied sponges in S. rathbunae are a single male and female of helper size.     

Reproductive rates,operational sex ratios and mate choice in St. Peter’s fish

Operational sex ratio (OSR) theory predicts that sexual differences in potential reproductive rates (PRRs) create biases in the OSR and thus determine the relative strength of sexual selection (competition and choice) operating on each sex. Although this theory is well accepted, empirical studies that quantify it are still lacking. This paper presents such a study. I measured the natural OSR of Galilee St. Peter’s fish (Sarotherodon galilaeus) in the field (Lake Kinneret) and examined the direction of mate choice in the laboratory. The OSR in Lake Kinneret was male biased. Both a male-biased sex ratio and higher male reproductive rates (twice as fast as females) contributed to the skew in the OSR, but the sexual differences in PRR were shown to be the main factor causing variation in the OSR. Females, the sex with the lower PRR, were more selective for mates. The faster male reproductive rate may explain why females are more selective for mates despite varying less in quality. Received: 29 May 1995/Accepted after revision: 13 April 1996     

Maternal characteristics and the production and recruitment of sons in the eastern kingbird (<Emphasis Type="BoldItalic">Tyrannus tyrannus</Emphasis>)

Sex allocation theory predicts that if variance in reproductive success differs between the sexes, females who are able to produce high-quality young should bias offspring sex ratio towards the sex with the higher potential reproductive success. We tested the hypothesis that high-quality (i.e., heavy) female eastern kingbirds (Tyrannus tyrannus) that bred early in the breeding season would produce male-biased clutches. A significant opportunity for sexual selection also exists in this socially monogamous but cryptically polygamous species, and we predicted that successful extra-pair (EP) sires would be associated with an excess of male offspring. Although population brood sex ratio did not differ from parity, it increased significantly with female body mass and declined with female breeding date, but was independent of the morphology and display (song) behavior (correlates of reproductive success) of social males and EP sires. Male offspring were significantly heavier than female offspring at fledging. Moreover, the probability that male offspring were resighted in subsequent years declined with breeding date, and was greater in replacement clutches, but lower when clutch size was large. Probability of resighting female offspring varied annually, but was independent of all other variables. Given that variance in reproductive success of male kingbirds is much greater than that of females, and that male offspring are more expensive to produce and have a higher probability of recruitment if fledged early in the season, our results support predictions of sex allocation theory: high-quality (heavy) females breeding when conditions were optimal for male recruitment produced an excess of sons.     

Male-biased sex ratios in New Zealand fur seal pups relative to environmental variation

A number of models have been proposed to provide adaptive explanations of sex-ratio variation in mammals. Two models have been applied commonly to primates and ungulates with varying success—the Trivers-Willard (TW) hypothesis, and the local resource competition (LRC) hypothesis. For polygynous, sexually dimorphic mammals, where males are larger and disperse more readily, these models predict opposite outcomes of sex-ratio adjustment within the same environmental context (high-resource years: TW—more sons; LRC—more daughters). However, many of the predictions of these two models can vary depending on factors influencing resource availability, such as environmental stochasticity, resource predictability, and population density. The New Zealand fur seal (Arctocephalus forsteri) is a polygynous mammal showing marked sexual dimorphism (larger males), with higher variation in male reproductive success expected. We provide clear evidence of male-biased sex ratios from a large sample of A. forsteri pups captured around South Island, New Zealand during 1996/1998, even after accounting for a sex bias in capture probability. The extent of the bias depended upon year and, in 1998, strong climatic perturbations (El Niño/Southern Oscillation, ENSO) probably reduced food availability. Significant male-biased sex ratios were found in all years; however, there was a significant decline in the male bias in 1998. There was no relationship between sex ratio and population density. We suggest that the sex-ratio bias resulted from the production of relatively more male pups. Under the density-independent scenario, the strong male bias in A. forsteri sex ratios is support for the TW model within an environment of high resource predictability. We suggest that some plasticity in the determination of pup sex among years is a mechanism by which A. forsteri females in New Zealand, and perhaps other otariid seals, can maximise fitness benefits when living in regions of high, yet apparently predictable, environmental variability. We also suggest that much of the inconsistency in the reported sex ratios for otariid seals results from the complex interaction of population density and environmental stochasticity influencing relative food availability over time.