When a Worm Loves a Coral: A Symbiotic Relationship from the Jurassic/Cretaceous Boundary

Round 1

Reviewer 1 Report

General recommendation to the authors (minor comments and corrections are directly inserted into the pdf file:

The description of the tubeworm-coral association is interesting and original, providing new information on a little studied topic. The manuscript is well written and clear, however, the 18 lines of results are scarce and based on few observations (see comments below on the examined cut sections) and the deriving interpretation and discussion are rather superficial and incomplete. To get completeness of observations and consequent interpretative hypotheses on the geometry of the tubes inside the host coral, I suggest integrating observations with further transverse sections cut at different growth stage (juvenile to adult) of the corals and with longitudinal ones (or alternatively integrate with ray-x investigations) for a tridimensional reconstruction of the worm tubes. About the interpretation of your sections, I suggest considering the paper of Lin & Herig (2020) Boll.Soc. Paleont. It. As deducible below (fig.5 of the paper) two tube-holes in the same section of a corallite may correspond to a unique individual also in the studied scleractinians. At least you should discuss this hypothesis or another one on the basis of results about tubes’ geometry. 

 

Also, more detailed observations at higher magnification (possibly under SEM) of the structure of tube walls would ascertain that type 2 belong to serpulids. It already seems to show the growth lamellae typical of serpulids (as the author just mention in line 26).

I encourage authors to integrate with the missing observations the results and consequently interpretation (arrangement of tubeworms inside the coral), providing an integrated version of their manuscript.

The summary must be rearranged accordingly.

Key words: it is not advisable to choose terms already present in the title

Below are punctual further comments to the text:

Lines 41-43: I suggest introducing the topic more exhaustively. There are important examples of polychaetes associated with corals from shelf to deep-sea settings. In this regard, I suggest mentioning (and briefly comment here or in the Discussion) at least the best-known symbioses i.e. Spirobranchus giganteus in Porites and Tubastrea (DeVantier et al., 1986; Hoeksema and ten Hove 2017 Marine Biodiversity) and Eunice norvegica in Desmophyllum pertusum (ex Lophelia) and Madrepora oculata (Mueller et al., 2013 PlosOne).

Line 94:

Line 103: The description needs to be integrated with observations of longitudinal sections and diverse transverse sections of the same corallite. See general comments above.

Line 106: The nature and structure of the two types of wall would be documented

Line 146: Fig. 3 a shows that worm tube is partially embedded within the wall of the colonised coral (see Darrel and Taylor 1993). In this case, the overgrowing process influences the coral morphology producing modification of its shape. The episkeletal infestation by the serpulid occurred in the vicinity of the coral soft-tissues that produced skeleton around the tube. Please, insert opportunely in Results and discussions. 

Line 166: bioclaustration (sensu Palmer and Wilson, 1988) is a term used when the embedded organisms are soft-bodied. Here, I suggest to use "bioimmuration" because worm esoskeletons (tubes) are embedded within the skeleton of the host coral (see Darrel and Taylor 1993). In this case, the overgrowing process influences the coral morphologies (see Fig. 3a) producing peculiar skeletal  protrusions and wall modification, indicating episkeletal infestation in the vicinity of the coral soft-tissues.

Line 239: I suggest to take into account in the discussion also the records of Serpula vermicularis associated to Madrepora oculata (Sanfilippo et al., 2013) and of Filograna sp. associated to Lophelia pertusa (Fig. 5 of Rosso et al., 2010).

Sanfilippo et al (2013) Serpula aggregates and their role in deep-sea coral communities in the southern Adriatic Sea. Facies, 59(4): 663-677.

Rosso et al. (2010). Hard and soft-bottom thanatofacies from the Santa Maria di Leuca deep-water coral province, Mediterranean. Deep Sea Research II. Topical Studies in Oceanography, 57(5-6): 360-379.

 

Comments for author File: Comments.pdf

Author Response

We are grateful for corrections, suggestion and comments. We accepted nearly all of them accordingly with them modified the manuscript. Changes are marked in the version of corrected manuscript with changes marked. Below some comments.

2. Materials and Methods

“for completeness of observations and consequent interpretative hypotheses on the geometry of the tubes inside the host coral, both transversal sections of the same corallite (juvenile to adult stage) and longitudinal sections must be added”

AND Line 103: The description needs to be integrated with observations of longitudinal sections and diverse transverse sections of the same corallite. See general comments above.

REPLY: Tubes with thin wall in longitudinal section was observed in one thin sections. Tube reached around 10 mm in length. Unfortunately this thin section is lost. Tubes with thin wall are in Calamophylliopsis from the Stramberk-type limestones are common. Serial sections through coral skeleton, numerous transverse sections of tubes - round or oval inshape – indicate that tubes are more or less straight. To obtain longitudinal section is difficult if section is not directly along the tube. Moreover coral colonies are recrystallized.

Line 106: The nature and structure of the two types of wall would be documented

REPLY: We introduced Figure 4 showing structure of the wall of thick tube.

 

Reviewer 2 Report

This is an interesting article, providing an important information about oldest Mesozoic coral-worm interactions. It can be published after minor revision 

Comments for author File: Comments.pdf

Author Response

We are grateful for corrections, suggestion and comments. We accepted nearly all of them accordingly with them modified the manuscript. Changes are marked in the version of corrected manuscript with changes marked. Below one

2. Materials and Methods

“do you have more precise information about the age of studied specimens? Or they can be dated as Tirthonian-Berriassian, without further details? “

REPLY: Tithonian-lower Berriasian age of the Stramberk Limestone is well established. However because these limestones occur as olistoliths (large blocks) in the flysch it is not possible to established precise age of most blocks, if not many samples from particular blocks are studied in terms of stratigraphy. Tithonian-Berriasian age of the Stramberk-type limestones is also well established but because they occur occur as pebbles and small blocks age of most pebbles in mostly not possible. Papers about the age of studied limestones can be found in the regional geological literature that we cite in our paper.

Caption of figure 1

“the map is generalized, and lack information about precise position of localities. To improve it, you can add coordinates for each site to figure explanations”

Such generalized map is by intention. More detailed position of collected samples is provided in papers cited by us.

Round 2

Reviewer 1 Report

L'opera riguarda un argomento intrigante che è ben spiegato e merita senza dubbio di essere pubblicato in questa forma. L'osservazione principale che ho fatto nella prima recensione è stata quella di cercare di capire come i vermi inizialmente attaccavano e come si sviluppavano e crescevano all'interno della corallite. Il mio suggerimento è stato quello di trarre ispirazione dall'esempio dei tetracoralli paleozoici. Tuttavia, il tuo materiale a portata di mano, con solo sezioni trasversali, non potrebbe chiarire questo con certezza e l'ipotesi sul modo di vivere (ad "U") potrebbe essere un'elucubrazione. I record futuri potrebbero aggiungere informazioni su di esso. Credo quindi che il manoscritto possa essere tranquillamente accettato in questa nuova forma riveduta.