**Egg-Laying in the Cuttlefish** *Sepia officinalis*

**Egg-Laying in the Cuttlefish Sepia officinalis**

DOI: 10.5772/intechopen.71915

#### Céline Zatylny-Gaudin and Joël Henry Additional information is available at the end of the chapter

Céline Zatylny-Gaudin and Joël Henry

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.71915

#### **Abstract**

This chapter reviews studies about egg-laying in the cuttlefish Sepia officinalis. Egg masses are spawned in specific mating and spawning coastal areas where mates aggregate between April and June in the English Channel and all year long in the Mediterranean Sea. Environmental cues are clearly involved in the aggregation process, but chemical communication also plays a determining role in these complex mechanisms. The successive steps of egg-laying are orchestrated by three classes of regulatory peptides: (1) neuropeptides that integrate environmental cues, (2) ovarian regulatory peptides that modulate the activity of the genital tract, and (3) sex pheromones expressed and released by the oviduct gland. After egg-laying, embryo protection is ensured for 8-10 weeks by a multilayer capsule secreted by the accessory sex glands. The oviduct gland secretes the inner layer of the egg case. The main nidamental gland secretes the main polysaccharides and glycoproteins, such as Sepia Egg Case Proteins, involved in capsule formation and in embryo protection. The accessory nidamental gland expresses specific proteins inherent in the structural organization of the gland, and hosts symbiotic bacteria. Similarly to salivary glands, this gland secretes immune factors possibly associated with gamete and/or embryo protection.

**Keywords:** reproduction, egg-laying, neuropeptides, ovarian peptides, egg-case, common cuttlefish

#### **1. Introduction**

Phylogenetically, anatomically, and physiologically speaking, cephalopods are indeed mollusks. Yet, they possess special characteristics that distinguish them from other molluscan classes, especially the other two major classes, gastropods and bivalves.

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

First of all, they are the most mobile mollusks. They come in the form of pelagic species capable of performing large-amplitude horizontal and vertical migrations, like squid. Octopoda are in turn largely territorial and therefore sedentary, while the common cuttlefish *Sepia officinalis* exhibits a nectobenthic behavior associated with low or medium migration amplitude depending on the latitude.

**2. Egg-laying: description**

conspecifics, while increasing their ventilation rate.

females and is very difficult to estimate.

internal and external oocyte capsules before fertilization.

**3. Egg-laying: regulation**

mature cleavage products.

oviduct [2].

and 8 kDa.

The cuttlefish *Sepia officinalis* is a semelparous species with a life cycle that varies depending on the geographical location of the population: 15–16 months in the Mediterranean Sea versus 20–22 months in the English Channel. Spawning is associated with a stereotyped behavior. In aquaria, sexually mature females that have not spawned yet manipulate eggs laid earlier by

Egg-Laying in the Cuttlefish *Sepia officinalis* http://dx.doi.org/10.5772/intechopen.71915 5

The different behavioral sequences leading to the laying of eggs are gradually repeated and eventually lead to the laying of the first egg (personal observation). A female can lay dozens of eggs at once, probably 150–200 eggs, which roughly corresponds to the storage capacity of the genital coelom, before a pause that allows it to replenish its stock of mature oocytes (stage V) through asynchronous gametogenesis. It also restores the capsular products secreted by the oviduct gland and the nidamental glands. Some females are then able to lay a second batch of eggs and probably several successive spawns. We do not know exactly how many eggs are laid before the programmed death of the animal. Fertility is probably quite variable among

The first work on the contractile structures of the female reproductive system led to the identification of numerous myotropic or myosuppressor regulatory peptides. The first of them, a neuropeptide belonging to APGWamide family, was identified from a sample of optic lobes purified by rpHPLC on the basis of its myosuppressive effect on the contraction of the distal

Then, new myotropic bioassays on the contractile organs of the female genital apparatus were performed, and the bases of the functional control of spawning and the related activities were laid, for example, blocking or inducing oocyte transport in the oviduct and the secretion of

From the papers published on this topic between 1997 and 2006, it appears that the successive steps of egg-laying are mainly governed by two classes of regulatory peptides: neuropeptides involved in the integration of environmental cues and ovarian regulatory peptides that modulate the activity of the genital tract [2–8]. The recent development of "-omics" approaches based on *de novo* RNAseq and mass spectrometry led to the identification of transcripts and

Using a transcriptomic approach, Enault and collaborators [9] discovered a third category of regulatory peptides, namely the sex pheromones expressed and released by the oviduct gland, and cleaved from three protein precursors into bioactive peptides ranging between 1.3

Unlike other classes of molluscs, cephalopods possess a cephalopodium whose eight arms play an important role in predation but also in mating and egg-laying during the formation of the egg mass (**Figure 1**). These arms are also used for handling prey during catches by capping [1].

This ability to handle prey is quite unique in the marine environment and only found in primates and in some mammals. It is probably related to the exceptional development of the central nervous system (CNS). This CNS is protected by a cartilaginous skull and is located between the eyes, which are capable of forming an image.

**Figure 1.** Main successive steps of the life cycle of the cuttlefish *Sepia officinalis*. (Photo credits: V. Cornet, J. Henry, C. Zatylny-Gaudin).
