Variability in fecundity of the brown crab, Callinectes bellicosus Stimpson, 1859 (Brachyura, Portunidae), along the coast of Sonora

This work analyses how the fecundity of the brown swimming crab, Callinectes bellicosus, varies along the coast of Sonora in the Gulf of California. Ripe female crabs were collected during May 2015 in four zones, and fecundity was determined and compared with carapace width (CW), total body weight (TW) and egg mass weight (MW). TW ranged between 100.5 g and 209.8 g (average = 158.2 g, coefficient of variation (CV) = 23.4%); CW ranged from 97.9 mm to 123.6 mm (average = 113.4 mm, CV = 8.3%); MW varied from 16.4 g to 34.1 g (average = 25.3 g, CV = 20.4%). The total fecundity (number of eggs per female) of C. bellicosus varied from 1 769 195 to 3 739 254 (average = 2 730 217, CV = 22.2%); partial fecundity (number of eggs per g of egg mass) ranged from 100 422 to 117 130 (average = 107 721, CV = 5.1%). A general north-south decrease in fecundity was observed, although the least fecund females were found in central Sonora (Kino Bay). The most significant linear correlation was found between total fecundity vs. egg mass weight. Total fecundity was better explained by a Von Bertalanffy model, with a maximum average fecundity of 3.7 million eggs for a female of 230 g total weight.

Another brick in the wall: population dynamics of a symbiotic species of Oxydromus (Annelida, Hesionidae), described as new based on morphometry

Oxydromus humesi is an annelid polychaete living as a strict bivalve endosymbiont (likely parasitic) of Tellina nymphalis in Congolese mangrove swamps and of Scrobicularia plana and Macomopsis pellucida in Iberian saltmarshes. The Congolese and Iberian polychaete populations were previously considered as belonging to the same species, the latter showing regular distribution, intra-specific aggressive behaviour, and complex hostentering behaviour. The fresh Iberian samples enabled us to undertake consistent morphometric analyses, as well as to further analyse the characteristics of the association and the population dynamics of the Iberian population hosted by S. plana. Among the morphological differences between the Congolese and Iberian specimens, leading to the description of the latter as Oxydromus okupa sp. nov., the most important are: 1) longer cephalic appendages, 2) greater distance between the eyes, 3) larger dorsal cirrostyle in relation to the corresponding dorsal lobe and cirrophore. Moreover, dorsal and ventral lobes are similar in length, with the tip of the former reaching the tip of the latter in O. okupa sp. nov., while the dorsal lobe is much shorter than the ventral one in O. humesi. Mature adults of O. okupa sp. nov. occurred during the whole study period, with a higher percentage of ripe females in spring and, particularly, in summer. Numerous host specimens showed the symbiont’s most preferred shell length (>26 - 36 mm). However, the prevalence was very low (usually <5%) and showed a clear seasonal pattern, being lower during spring/summer. This suggests that males are able to leave their hosts during this period, most likely to improve fertilization by directly entering or approaching a host occupied by a ripe female, while females usually remain inside. Based on the new results, the current knowledge of symbiotic Hesionidae and their relationships with invertebrate hosts is updated and discussed.

Rediscovery and augmented description of the HMS ‘Challenger’ acorn worm (Hemichordata, Enteropneusta),Glandiceps abyssicola, in the equatorial Atlantic abyss

A 2009 oceanographic expedition of the Russian Academy of Sciences collected the anterior region of a single acorn worm (phylum Hemichordata, class Enteropneusta) by trawling at a depth of 5560 m in the Romanche Trench (equatorial Atlantic). The specimen was a ripe female with numerous, relatively small oocytes in each ovary. Phylogenetic analysis of rDNA sequences robustly placed the worm in the family Spengelidae. In addition, morphological features of the proboscis, collar, and anterior trunk region indicated that the worm wasGlandiceps abyssicola, a species previously represented solely by the holotype, which had been dredged from the equatorial Atlantic in 1873 by the HMS ‘Challenger’ and subsequently sent to Germany for description by Spengel (1893). The holotype was presumably destroyed by World War II bombing; therefore, we here designate the Romanche Trench specimen as the neotype ofG. abyssicolaand supply an augmented species diagnosis.

Reproductive traits of Gymnogeophagus labiatus (Teleostei, Cichlidae), in an upper stretch of Sinos river, Caraá, Brazil

This work describes the reproduction of Gymnogeophagus labiatus (Hensel, 1870) from an upper stretch of Sinos river, southern Brazil, based on the analysis of 174 males and 132 females captured in monthly samples taken from January to December 2007. Results showed that reproductive activity occur in spring and summer although ripe males were found along the year. The standard length of the smallest ripe male was 104.74 mm (Lt) and the smallest ripe female was 55.00 mm (Lt). There was a significant difference in total sex ratio, with 1.32 males to each female (χ2 = 5.76). Males were much more abundant in March (1.75 males: 1 female) and December (5 males: 1 female). Females were more abundant in the 62├77 mm interval (1 male: 2.36 female) while males were more abundant in the 77├92 mm size interval (2.57 males: 1 female). The largest length intervals were composed of only males. Mean absolute fecundity was 113.4 (± 31.24 sd) and mean relative fecundity was 0.0125 (± 0.0026 sd) oocytes/mg. In ripe ovaries, small-diameter oocytes were observed at high frequencies while larger ones occurred at lower frequencies. This pattern is common in fishes with asynchronous oocyte development. Characteristics of G. labiatus, such as low fecundity, asynchrony in oocyte development, multiple spawning, and its well-known parental care behavior, are consistent with an equilibrium strategy, as proposed for other cichlids.

Changes in serum androgens and estrogens during spawning in bluefish, Pomatomus saltator, and king mackerel, Scomberomorus cavalla

Androgens and estrogens were assayed by radioimmunoassay (RIA) technique in serum of bluefish, Pomatomus saltator, and king mackerel, Scomberomorus cavalla. Both species were collected in the northeast Gulf of Mexico from August through November 1979. When categorized by stage of ovarian development a significant correlation between gonadosomatic indices (GSI) and serum estrogens was observed among female S. cavalla but not among P. saltator. Among males and females of both species, a significant correlation between GSI and serum androgens occurred. Peak levels of androgens in male king mackerel (38.12 ± 11.21 ng/mL) were not significantly different from peak levels of females (33.14 ± 5.10 ng/mL). However, in female bluefish, androgens peaked at 3.68 ± 0.88 ng/mL, twofold greater than in males (1.66 ± 0.28 ng/mL). Following this peak, a significant reduction in androgens occurred in ripe female bluefish. No significant change in estrogens occurred in these females. Although the functional significance of changes in androgens in spawning female bluefish was not determined, serum androgen levels may be a useful tool in identifying and timing maturation and spawning in both male and female teleosts.

On the Biology of Calanus Finmarchicus X. Seasonal Changes in Oxygen Consumption

The seasonal changes in the respiration of Calanus are considerable and are, on the whole, related to size and therefore to weight. Length alone is not enough to account for the differences since ripe females, although the same length as unripe, have a markedly higher respiration. In addition, by taking samples of large and of small Calanus of a single stage, it was shown that the difference in respiration was small. Neither is weight by itself enough to account for the difference between groups. Stage V Calanus are, for a given length, heavier even than ripe females and yet their oxygen utilization is low. In this instance, however, an important part of the weight consists of fat which is a food reserve and not actively metabolizing. The difference of weight between ripe and unripe females is not known, but ripe females must be heavier and this will account for their higher oxygen consumption.Although the oxygen and therefore the food required during the spring months is high, at that time the phytoplankton is at its maximum and is probably sufficient to fulfil all needs. Egg-laying depends on the food supply and it is then that Calanus starts breeding. In winter, on the other hand, the Calanus is present as Stage V and oxygen consumption is little more than half what earlier figures suggested. No ‘hibernation’ seems to take place but the population is living in an economical way for Stage V use little oxygen, live in deep water and do not undertake diurnal vertical migration.At 10° C ripe female Calanus will require daily from 3·9–7·2% of their body weight as dry matter in summer and from 2·8–6·7% in winter. Stage V will require 2·3–3·1% in summer and 1·4–3·3% in winter. The higher values are for carbohydrate and the lower for fat.It is difficult to believe that Calanus in winter will be able to find enough food by filtration alone. The fact that in the winter months it depends more on predation may account for its survival.

Notes and Memoranda

Motella fusca. A new British Record. On April 9th Mr. Lowe, Curator of the Municipal Museum, found on the shore under a stone a ripe female Motella, which he brought up to the Laboratory. The fish measured 19 cms. It had three barbels, and on investigation failed to agree with the descriptions of any of the five recognised British species: M. mustela, tricirrata, macrophthalma, maculata, or cimbria.