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With some reaching up to 40 cm and weighing 830 g, respectively.

Although weight varies seasonally according to reproduction and the maturity stage.

(reproduction and live cycle)

Isostichopus fuscus is dioecious. Gonads can only be determined and sexed under a microscope. There is no apparent sexual dimorphism among individuals, unless gonads are ripe. When gonads are ripe, males are a white color, while females gonads are orange.

(undetermined Stage): Gonads cannot be accurately distinguished at this stage. Connective tissue in the lumen is present and the gonadal wall is thickened

Spermatogenesis: folds in the gonadal wall are present that the lumen. Additionally, Spherical spermatocytes accumulate at the periphery. The accumulation of spermatocytes causes a decrease in the thickness of the connective tissue.

Maturity. The mature spermatozoa exhibit a rounded shape are slightly dorso-ventrally flattened. thin layer of spermatocytes is present at the periphery site.

Spawning- Developing spermatocytes are still present at the periphery layer. a layer of connective tissue is present at the gonad wall The gonadal wall is observed to thicken, and folds are present inside of the wall

Post-Spawning- A large quantity of phagocytes is present both inside and outside of the follicles. Connective tissue is reabsorbed in the gonadal wall of the follicle.

Oogenesis: Oogonia are attached to the germinal epithelium in the lumen. The oocytes are arranged in a single layer, and have a defined nucleus and peripheral nucleoli. The connective tissue and folds in the gonad gradually reduce as oogenesis progresses.

Mature: Oocytes are present in all tubules in the lumen, and their peripheral nuclei are distinguishable. Connective tissue is absent, and the gonadal wall is very thin (3). Phagocytes surround the inside and outside of the lumen.

Spawning: a layer of connective tissue is present at the gonad wall The gonadal wall is observed to thicken, and folds are present inside of the wall. Any of the remaining oocytes are either in maturity or oogenesis.

Post-spawning: Oocytes observed have significantly decreased in volume. Large amounts of connective tissue are present in the gonadal walls.

Hermaphroditism: Although rare, hermaphroditic samples have been collected. In these cases, the male and female follicles were in different gonadal stages, and some samples were in the spawning stages. In one case, both male and female follicles were in the spawning stages.

The potential for asexual reproduction is possible. Like most echinoderms, I. fuscus has a unique regenerative ability. Induced transverse fission has been experimented in a lab setting. The results were successful, showing a high survival rate, and a complete regeneration of anterior and posterior body parts in a maximum of three months. The results suggest that asexual propagation could serve as a potential tool for restoring their population in the wild.

(Reproductive Cycle). Spawning occurs in Isostichopus fuscus from July to September, with post-spawning gonads occurring in October. Gametogenesis was documented between January and July, with oogenesis occurring approximately one month before spermatogenesis. Peaks in reproduction followed by drastic declines have characterized I. fuscus as an episodic spawner, in which water temperature is thought to play a large role as a reproductive indicator.

(Larvae): I. fuscus has an indirect development. Larvae live in an oligotrophic environment, and must actively feed fro survival.

The development of I. fuscus is separted into larval and juvenile phases. The larval phase begins after the organism hatches from its embryonic envelope, and undergo a series of trasnformations for approximately 22 days; The juvenile stage is initiated afterwards.

Embryos hatch from the fertilization envelope roughly 10 hours after fertilization. The gastrulae have an epidermal layer that is entirely ciliated and supports their movement. After approximately 24 hours, the gastrulae transform into an auricularia larvae. Feeding begins upon the transition to this stage. After 19-24 days, the doliolaria stage is reached, where the larvae shrink to 50 percent of their size. 5 days later, the pentactula stage is reached, in which the organism goes through a settlement phase.

Early settled juveniles are typically 1-1.5 mm in length. Over a 3-4 week period, they undergo rapid growth at an average rate of 0.5-1 mm/day. The juveniles begin to develop brown pigment when they reach a length of approximately 5 mm, and tentacles are visible at about 8mm. At approximately day 52, papillae and an elongated intestine, which suggest peristaltic movements become present. The tegument thickness increase, and the epidermis transforms from a transparent to opaque appearance. At 2 cm in length, the coloration fades to a darkish brown that is characteristic of an adult brown sea cucumber.

(Growth). The average length and weight of Isostichopus fuscus is aprroximately 23 cm and 389 g, although the size and weights of individuals varies seasonally.

(Distribution): I. fusucs is typically found at depths varying from 3 to 20 m in rocky reefs, with sandy patches as a preferred substrate. Within these depths, I. fuscus has been found to predominate areas where high amounts of Ulva sp. are located. Like other sea cucumber, I. fuscus is a deposit feeder, whose survival tends to increase with soft-substrates such as sand or clay. Recent studies suggest that a blend of seaweed species such as P. durvillaei and S. ecuadoreanum are an optimal diet, although they can survive off of other types of seaweed.

(Aquaculture) I. fuscus

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